METHOD FOR ACCELERATING GROWTH OF PLANTS

Abstract

Title: METHOD FOR ACCELERATING GROWTH OF PLANTS The invention disclosed herein relates to methods for growing plants, in particular methods for growing a plant under such conditions that a young plant with a better quality is obtained and / or a young plant is obtained sooner, as compared to a standard outdoors-grown plant. The disclosure also relates to a plant per se, an arrangement to carry out said methods, a plant cultivation facility comprising said arrangement, as well as a use of artificial light to accelerate the growth of a plant.

Description

P138101NL00 Title: METHOD FOR ACCELERATING GROWTH OF PLANTS TECHNOLOGICAL FIELD The invention disclosed herein relates to methods for growing plants, plants per se, arrangements to carry out said methods, plant cultivation facilities comprising said arrangement, and the use of artificial light to accelerate growth of plants. BACKGROUND The process of growing plants is usually lengthy. Typically, seed is sown in an outdoors nursery bed or in a tunnel or greenhouse, and the resulting seedlings grow slowly until they are large enough to be transferred to the field. When a plant is ready to be transferred to the field, it is typically referred to as a “young plant”. For example, for forestry plants it typically takes about 125-180 days (including germination) to obtain a young plant, for mangrove about 150 days (including germination), for potato plants grown from real seeds in a tunnel or greenhouse about 42 days, and for strawberry plants grown from real seeds, e.g. in a tunnel or greenhouse, about 65-90 days. Moreover, during the outdoors nursery stage the conditions are not well-controlled, as the weather conditions are not constant. Furthermore, there may be an undesired degree of variation between different plants, and / or the plants may be exposed to pests and diseases. As such, it is desired that methods are developed that accelerate the growth of plants, in particular such that young plants can be transferred sooner to the field, shortening the production cycle. In particular, it is desired that such a method be provided that can be readily carried out, allows employing controlled conditions (including controlled environmental conditions such as light, CO , relative humidity, and the like; pest control; and / or disease 2 control), may reduce the variation between plants, and / or is economical. Some efforts have been made in this respect. For example, the plants may be exposed to growth hormones and / or the plant material may be genetically enhanced. However, the use of chemicals such as growth hormones is undesired as it may lead to water pollution, and genetic enhancement may be cumbersome. Moreover, both procedures are typically expensive. As such, it is still desired to further accelerate the growth of plants, to achieve said acceleration at an early stage, to achieve said acceleration without using genetic enhancement and / or growth hormones, and / or to faster obtain significant differences as compared to reference examples such as outdoor-grown plants. SUMMARY The methods, arrangements, facilities, plants, and uses as disclosed herein meet one or more of the abovementioned desires. In particular, one or more of the abovementioned desires are achieved by the method, arrangement, facility, plant, and use as claimed. BRIEF DESCRIPTION OF THE FIGURES Figure 1 depicts Acacia nilotica plants of about 60-80 cm grown using methods of the invention. It is also indicated that under conventional, traditional conditions it would take about 120-180 days (including germination) to obtain a young plant. “DAS” means “days after sowing”. Figure 2 depicts mangrove plants grown using traditional conditions (top), and mangrove plants grown using methods of the invention (middle and bottom). Figure 3 depicts potato plants grown from real seeds. The plant on the left is a reference example, which was grown in a greenhouse / tunnel. The plants in the middle and on the right of Figure 3 were grown using a method of the invention in 21 and 34 days (including germination), respectively. DETAILED DESCRIPTION In a general sense, the invention is based on the judicious insight that providing artificial light to a plant in its early stages of development accelerates and / or improves the growth and development of said plant. As such, the invention relates to a method for growing a plant, wherein the method comprises the steps of: a) providing plant material selected from the group consisting of a seedling, a cutting, and a plant obtained from a tissue culture; wherein preferably the seedling is obtained by providing a seed and germinating said seed; and b) exposing said plant material to light, wherein said light is substantially exclusively artificial grow light. In particular, the plant is preferably grown under such conditions that a young plant with a better quality is obtained and / or a young plant is obtained sooner, as compared to a standard outdoors-grown plant. As used in this phrase, “such conditions” may refer to any one of the preferred features as mentioned herein, and combinations thereof, in particular to the artificial grow light. As is known to the skilled person, a plant is of improved quality if it has for example a higher dry weight, a better root structure, a higher survival rate, a lower susceptibility to plagues and / or diseases, and / or a faster production rate when grown outdoors. As used herein, “a young plant is obtained sooner” means that the time for obtaining a young plant is reduced. Naturally, it will depend on the plant or the plant variety to exactly what extent the process is accelerated. Typically, “sooner” in this context means that when using a method of the invention, a young plant is obtained in less than 95%, preferably less than 90%, more preferably less than 80%, more preferably less than 75%, even more preferably less than 70%, of the time required to typically obtain a young plant under traditional outdoor conditions. In particular, methods as disclosed herein enable that a young plant is obtained more quickly, such that young plants can be transferred sooner to the field, shortening the production cycle. Moreover, the methods can be readily carried out, allow employing controlled conditions, may reduce the variation between plants, and / or are economical. In the methods of the disclosure plant material is provided. It will be understood that the plant material is subjected to the method of the invention to obtain a (young) plant. Especially, the term “plant material” may refer to any stage of growth, at any moment starting from seed, seedling, cutting, or tissue culture plant, up to a young plant and even a mature plant. In principle, at any stage of growth a plant can benefit from methods of the invention. Preferably, however, the plant material is selected from the group consisting of a seedling, a cutting, and a tissue culture plant. In principle, the method of the invention can be applied to any plant species. Preferably, the plant is selected from the group consisting of mangrove, a forest plant, a potato plant, a strawberry plant, a cacao plant, a palm plant, a tomato plant, an orchid, and Paulownia tomentosa. More preferably, the plant is selected from the group consisting of mangrove, a forest plant, a potato plant, and a strawberry plant. Preferably, the plant is a mangrove. As used herein, “mangrove” indicates a plant of the family Rhizophoraceae, preferably of the genus Rhizophora, most preferably of the species Rhizophora mangle. In other preferred embodiments, the plant is a forest plant. Preferably, the forest plant is selected from the group consisting of fruit-producing plants, food-producing plants, gum- producing plants, timber trees, rubber trees, medicinal plants, oil-producing plants, resin- producing plants, fiber-producing trees, paper-producing trees, and Paulownia tomentosa (also known as a princess tree, empress tree, or foxglove-tree). Preferably, the timber tree is selected from the group consisting of teak (Tectona grandis), mahogany (Swietenia spp.), eucalyptus (Eucalyptus spp.), pine (Pinus spp.), and douglas fir (Pseudotsuga menziesii). Preferably, the medicinal plant is selected from the group consisting of ginseng (Panax spp.), neem (Azadirachta indica), and cinchona (Cinchona spp.). Preferably, the rubber tree is Hevea brasiliensis. Preferably, the food-producing tree is a cocoa plant (Theobroma cacao), or a palm tree (i.e. a plant of the family Palmae or Arecaceae). More preferably, the food- producing tree is a date palm (i.e. a plant of the genus Phoenix, preferably of the species Phoenix dactylifera or Phoenix canarensis). Preferably, the oil- and / or resin-producing plant is selected from the group consisting of oil palm (Elaeis guineensis), frankincense (Boswellia spp.), pine trees (Pinus spp.), sandalwood (Santalum album), and agarwood (Aquilaria spp.). Preferably, the fiber- and / or paper-producing trees are bamboo (Bambusoideae spp.), or mulberry (Morus spp.). Most preferably, the forest plant is an acacia. As used herein, “acacia” refers to a plant of the genus Acacia or Vachellia. Preferably, the acacia is Acacia nilotica (also known as Vachellia nilotica, gum Arabic tree, babul, thorn mimosa, Egyptian acacia, and thorny acacia). In other preferred embodiments, the plant is a potato plant. As used herein, “potato plant” refers to a plant of the species Solanum tuberosum. In other preferred embodiments, the plant is a strawberry plant. As used herein, “strawberry plant" or “strawberry” refers to a plant of the genus Fragaria, preferably of the species Fragaria × ananassa. Preferably, the plant material is a seedling. Seedlings are readily obtained from seeds of a plant. As used herein, “seedling” refers to a plant at the developmental stage between germination and being a young plant. The seedling typically has a height of at most 39 cm, preferably at most 35 cm, more preferably at most 30 cm, more preferably at most 25 cm, more preferably at most 20 cm, more preferably at most 15 cm, more preferably at most 10 cm, and most preferably at most about 8 cm. Preferably, a seedling is used directly after germination. Preferably, the seedling is obtained by providing a seed and germinating said seed. As such, the method of the invention may also start with providing a seed of a plant; and germinating said seed. Preferred methods of germinating said seed are mentioned below. In particular, if the plant to be grown is a potato plant or a strawberry plant, it is preferred that the plant material is a seedling. Then, the method of the invention preferably starts with a step of providing a seed, preferably a true seed, and germination said seed to obtain a seedling. As used herein, “true seed” or “real seed” refers to a fertilized mature ovule that typically has an embryo, stored food material, and / or a protective coat or coats. For example, for potatoes a true seed can be distinguished from a tuber that is traditionally used for germination or sprouting. For potatoes, it is preferred that the true seed is a hybrid seed, for example True Hybrid Potato Seed (HPTS). The plant material may also be a cutting or a tissue culture plant, in particular when the plant is a forestry plant. The advantage of using a cutting or a tissue culture plant is that substantial or even complete genetic homogeneity may be achieved between various plants. The skilled person is aware how to obtain cuttings and / or tissue culture plants. The cutting or tissue culture plant typically has a height of at most 39 cm, preferably at most 35 cm, more preferably at most 30 cm, more preferably at most 25 cm, more preferably at most 20 cm, more preferably at most 15 cm, more preferably at most 10 cm, and most preferably at most about 8 cm. In the method of the invention, the plant material is exposed to light, wherein said light is substantially exclusively artificial grow light. Artificial grow light is non-natural light that induces the growth of plants, in particular induces photosynthesis in plants. Artificial grow light has a different composition in terms of wavelength and / or intensity than sunlight. An advantage of using artificial grow light is that more control can be achieved, in the sense that a constant spectrum and intensity can be maintained throughout the day, whereas the composition and intensity of sunlight changes during the day. With “substantially exclusively” it is typically meant that at least 95%, preferably at least 97%, more preferably at least 98%, more preferably at least 99%, more preferably at least 99.9%, and most preferably 100%, of the light to which the plant is exposed is artificial grow light. Consequently, it is preferred that the plant material is not exposed to natural sunlight, and more preferably that the plant material is not exposed to any other light than said artificial grow light. In particular, it is preferred that the plant material is shielded from natural sunlight, and more preferably that the plant material is shielded from to any other light than said artificial grow light. Preferably, the method of the invention is carried out indoors. As used herein, “indoors” typically refers to a substantially sunlight-free conditioned cultivation environment. This environment may also be configured to control the relative humidity of the air, the space temperature, the substrate temperature, and / or the carbon dioxide concentration of the air. Below, preferred features of the artificial grow light are described. In particular, the photosynthetic flux density of various components of said artificial grow light are mentioned. 2 Herein, the photosynthetic flux density is expressed in units of µmol / m / s. Therein, the area 2 (m ) refers to the surface area at the top of the plant material, typically one or more leaves of said plant material. The skilled person will understand that to maintain a specific photosynthetic flux density or to remain within a range of photosynthetic flux densities throughout the method of the invention, the height of the one or more lighting devices that are typically used to produce the artificial grow light and / or the height of the surface on which the plant material are kept, may be adjusted, if necessary, while the plant material grows. In other words: the distance between said lighting device and the plant material may be held substantially constant by for example increasing the height at which the lighting device is kept as the plant material grows and / or lowering the surface on which the plant material are kept, if necessary. Alternatively, said distance may be fixed for a certain room, and the plant material may be moved to a different room with a different fixed distance between the lighting device and the plant material. For all of the artificial grow light components listed herein it holds that no upper limit needs to be specified for the photosynthetic flux density, since exposing the plant material to more light is not detrimental to the growth of the plant. However, preferably an as low as possible photosynthetic flux density is used, so as to reduce costs, and / or provide a more environmentally friendly method. Preferably, the artificial grow light comprises a red component having a wavelength in a range of from 600 to 700 nm. Preferably, the red component comprises substantially all wavelengths within a range of from 600 to 700 nm, with a peak between 650 and 670 nm, preferably at 660 nm, and wherein the light intensities at 600 nm and 700 nm are less than 5%, preferably less than 2%, more preferably less than 1% of the intensity at said peak. Preferably, the red component has a photosynthetic flux density of at least 30 2 2 2 µmol / m / s; more preferably at least 50 µmol / m / s; more preferably at least 75 µmol / m / s; 2 2 more preferably at least 100 µmol / m / s; more preferably at least 125 µmol / m / s; more 2 2 preferably at least 150 µmol / m / s; more preferably at least 175 µmol / m / s; more preferably at 2 2 least 190 µmol / m / s; more preferably at least 200 µmol / m / s; and most preferably at least 210 2 µmol / m / s. Preferably, the red component has a photosynthetic flux density of at most 1000 2 2 2 µmol / m / s; more preferably at most 750 µmol / m / s; more preferably at most 600 µmol / m / s; 2 2 more preferably at most 500 µmol / m / s; more preferably at most 450 µmol / m / s; more 2 2 preferably at most 400 µmol / m / s; more preferably at most 350 µmol / m / s; more preferably at 2 2 most 300 µmol / m / s; more preferably at most 250 µmol / m / s; and most preferably at most 2 230 µmol / m / s. Preferably, the red component has a photosynthetic flux density in a range of from 30 2 2 to 1000 µmol / m / s; more preferably in a range of from 50 to 750 µmol / m / s; more preferably 2 in a range of from 75 to 600 µmol / m / s; more preferably in a range of from 100 to 500 2 2 µmol / m / s; more preferably in a range of from 125 to 450 µmol / m / s; more preferably in a 2 range of from 150 to 400 µmol / m / s; more preferably in a range of from 175 to 350 2 2 µmol / m / s; more preferably in a range of from 190 to 300 µmol / m / s; more preferably in a 2 2 range of from 200 to 250 µmol / m / s; and most preferably of from 210 to 230 µmol / m / s. Most preferably, the red component has a photosynthetic flux density of about 220 2 µmol / m / s. Preferably, the artificial grow light comprises a blue component having a wavelength in a range of from 400 to 500 nm, preferably in a range of from 420 to 495 nm. Preferably, the blue component comprises substantially all wavelengths within a range of from 420 to 495 nm, with a peak between 440 and 460 nm, preferably at 450 nm, and wherein the light intensities at 420 nm and 495 nm are less than 5%, preferably less than 2%, more preferably less than 1% of the intensity at said peak. More preferably, the blue component comprises substantially all wavelengths within a range of from 400 to 500 nm, with a peak between 440 and 460 nm, preferably at 450 nm, and wherein the light intensities at 400 nm and 500 nm are less than 5%, preferably less than 2%, more preferably less than 1% of the intensity at said peak. Preferably, the blue component has a photosynthetic flux density of at least 10 2 2 2 µmol / m / s; more preferably at least 20 µmol / m / s; more preferably at least 25 µmol / m / s; 2 2 more preferably at least 30 µmol / m / s; more preferably at least 40 µmol / m / s; more preferably 2 2 at least 45 µmol / m / s; more preferably at least 50 µmol / m / s; more preferably at least 55 2 2 2 µmol / m / s; more preferably at least 60 µmol / m / s; and most preferably at least 65 µmol / m / s. Preferably, the blue component has a photosynthetic flux density of at most 250 2 2 2 µmol / m / s; more preferably at most 200 µmol / m / s; more preferably at most 150 µmol / m / s; 2 2 more preferably at most 125 µmol / m / s; more preferably at most 100 µmol / m / s; more 2 2 preferably at most 95 µmol / m / s; more preferably at most 90 µmol / m / s; more preferably at 2 2 most 85 µmol / m / s; more preferably at most 80 µmol / m / s; and most preferably at most 75 2 µmol / m / s. Preferably, the blue component has a photosynthetic flux density in a range of from 10 2 2 to 250 µmol / m / s; more preferably of from 20 to 200 µmol / m / s; more preferably of from 25 2 2 to 150 µmol / m / s; more preferably of from 30 to 125 µmol / m / s; more preferably of from 40 2 2 to 100 µmol / m / s; more preferably of from 45 to 95 µmol / m / s; more preferably of from 50 to 2 2 90 µmol / m / s; more preferably of from 55 to 85 µmol / m / s; more preferably of from 60 to 80 2 2 µmol / m / s; and most preferably of from 65 to 75 µmol / m / s. Most preferably, the blue component has a photosynthetic flux density of about 70 2 µmol / m / s. Preferably, the artificial grow light comprises a far-red component having a wavelength in a range of from 680 to 800 nm, more preferably in a range of from 680 to 770 nm, more preferably in a range of from 701 to 770 nm. Preferably, the far-red component comprises substantially all wavelengths within a range of from 701 to 770 nm, with a peak in a range of from 720 to 750 nm, preferably in a range of from730 to 740 nm, and wherein the light intensities at 701 nm is less than 30%, preferably less than 25%, and more preferably less than 23% of the intensity at said peak; and the light intensity at 770 nm is less than 5%, preferably less than 4%, more preferably less than 3% of the intensity at said peak. More preferably, the far-red component comprises substantially all wavelengths within a range of from 680 to 770 nm, with a peak between 730 and 750 nm, preferably in a range of from 730 to 740 nm, and wherein the light intensities at 680 nm and 770 nm are less than 6%, preferably less than 5%, more preferably less than 4% of the intensity at said peak. Preferably, the far-red component has a photosynthetic flux density of at least 1 2 2 2 µmol / m / s; more preferably at least 2 µmol / m / s; more preferably at least 5 µmol / m / s; more 2 2 preferably at least 8 µmol / m / s; more preferably at least 10 µmol / m / s; more preferably at 2 2 least 12 µmol / m / s; more preferably at least 15 µmol / m / s; more preferably at least 18 2 2 2 µmol / m / s; more preferably at least 20 µmol / m / s; and most preferably at least 25 µmol / m / s. Preferably, the far-red component has a photosynthetic flux density of at most 100 2 2 2 µmol / m / s; more preferably at most 75 µmol / m / s; more preferably at most 60 µmol / m / s; 2 2 more preferably at most 50 µmol / m / s; more preferably at most 47 µmol / m / s; more 2 2 preferably at most 45 µmol / m / s; more preferably at most 42 µmol / m / s; more preferably at 2 2 most 40 µmol / m / s; more preferably at most 37 µmol / m / s; and most preferably at most 35 2 µmol / m / s. Preferably, the far-red component has a photosynthetic flux density in a range of from 2 2 1 to 100 µmol / m / s; more preferably of from 2 to 75 µmol / m / s; more preferably of from 5 to 2 2 60 µmol / m / s; more preferably of from 8 to 50 µmol / m / s; more preferably of from 10 to 47 2 2 µmol / m / s; more preferably of from 12 to 45 µmol / m / s; more preferably of from 15 to 42 2 2 µmol / m / s; more preferably of from 18 to 40 µmol / m / s; more preferably of from 20 to 37 2 2 µmol / m / s; and most preferably of from 25 to 35 µmol / m / s. Most preferably, the far-red component has a photosynthetic flux density of about 30 2 µmol / m / s. Preferably, the artificial grow light comprises the red component and the blue component. In some preferred embodiments, the artificial grow light essentially consists of the red component and the blue component. If plants with a larger internode length and / or taller plants are desired, it is however desired that the artificial grow light comprises the far-red component. As such, in some preferred embodiments the artificial grow light comprises the red component, the blue component, and the far-red component. More preferably, the artificial grow light essentially consists of the red component, the blue component, and the far-red component. If the artificial grow light comprises said red component and said far-red component, it is preferred that the ratio of the photosynthetic flux density of said red component over the photosynthetic flux density of the far-red component is in a range of from 1:1 to 60:1. More preferably, said ratio is of from 2:1 to 40:1; more preferably of from 3:1 to 30:1; more preferably of from 4:1 to 20:1; more preferably of from 5:1 to 15:1; more preferably of from 5.5:1 to 12:1; more preferably of from 6:1 to 9:1; even more preferably of from 7:1 to 8:1. Most preferably, said ratio is about 7.3:1. For all of the artificial grow light components listed herein it holds that while lighting devices can be used that produce a single wavelength within the defined range, the best results are obtained when using one or more lighting devices that produce a range of wavelengths. Typically, the peak intensity of such light sources is at or around a specific wavelength, and the light intensity gradually decreases towards the lower and upper wavelengths of the range provided, typically forming a bell curve or a skewed distribution around said specific wavelength. At the lower and upper wavelengths of the range provided, the light intensity is typically less than 5%, preferably less than 2%, more preferably less than 1% of the intensity at said specific wavelength. For example, for the red light component a light source can be used producing light with wavelengths in a range of from 600-700 nm with a peak between 650 and 670 nm, preferably at 660 nm. Likewise, for the blue light component a lighting device can be used producing light with wavelengths in a range of from 420-495 nm with a peak between 440 and 460 nm, preferably at 450 nm. Similarly, for light having a far-red component a light source can be used producing light with wavelengths in a range of from 701-770 nm, preferably in a range of from 680-770 nm, with a peak in a range of from 720 to 750 nm, preferably in a range of from 730 to 740 nm. Preferably, in the methods of the invention the plant material is exposed to the artificial grow light for at least 8 hours per day; preferably for at least 9 hours a day, more preferably at least 10 hours per day, more preferably at least 11 hours a day, and most preferably at least 12 hours a day. Preferably, in the methods of the invention the plant material is exposed to the artificial grow light for at most 24 hours per day; preferably for at most 23 hours a day, more preferably at most 22 hours per day, more preferably at most 21 hours a day, more preferably at most 20 hours a day. Preferably, in the methods of the invention the plant material is exposed to the artificial grow light for a duration in a range of from 8 to 24 hours a day, more preferably of from 9 to 22 hours a day, and most preferably of from 12 to 20 hours a day. If the plant is a forest plant, in particular an Acacia plant, the plant material is preferably exposed to the artificial grow light for a duration in a range of from 12 to 18 hours a day, more preferably of from 13 to 15 hours a day, and most preferably for about 14 hours a day. If the plant is a mangrove plant, in particular Rhizophora, the plant material is preferably exposed to the artificial grow light for a duration in a range of from 10 to 16 hours a day, more preferably of from 11 to 13 hours a day, and most preferably for about 12 hours a day. If the plant is a potato plant, the plant material is preferably exposed to the artificial grow light for a duration in a range of from 12 to 22 hours a day, more preferably of from 16 to 20 hours a day, and most preferably for about 16 or about 20 hours a day. If the plant is a strawberry plant, the plant material is preferably exposed to the artificial grow light for a duration in a range of from 14 to 18 hours a day, more preferably of from 15 to 17 hours a day, and most preferably for about 16 hours a day. It will be understood that the exposure of the plant material to the artificial grow light may be continuous or discontinuous throughout the day. However, it is preferred that the plant material is continuously exposed to the artificial grow light during the time periods mentioned herein. When the plant material is not exposed to artificial grow light during the methods of the disclosure, it is preferred that the plant material is not exposed to any visible light, more preferably that said plant material is kept in the dark. In principle, the growth of and / or flowering in the plant may be accelerated further by other means than exposing said plant to artificial growth light, such as by pruning at a fork from which an orthotropic shoot and at least one plagiotropic branch have developed by removing at least the orthotropic shoot and maintaining the at least one plagiotropic branch; contacting the plant material with growth hormones (in particular synthetic and / or artificial growth hormones); and / or genetically enhancing the plant material. However, one advantage of the methods of the disclosure is that such means are not necessary, thus making the process easier, more economical, and / or more readily available. Thus, the methods of the disclosure preferably do not comprise pruning the plant material at a fork from which an orthotropic shoot and at least one plagiotropic branch have developed by removing at least the orthotropic shoot and maintaining the at least plagiotropic branch. Likewise, the methods of the disclosure preferably do not comprise the step of bringing the plant material into contact with growth hormones, in particular artificial and / or synthetic growth hormones. Moreover, the methods of the disclosure preferably do not comprise genetically enhancing the plant material. It will be understood, however, that the methods of the invention optionally comprise pruning plant material having at least one plagiotropic branch by removing said at least one plagiotropic branch. Duration of method In principle, any plant can benefit from the method of the invention for any length of time, whether it be short or for the entire lifetime of said plant. On the one hand, the longer the method of the invention is applied, the stronger and healthier a plant may become. Therefore, it is preferred that the method of the invention is carried out for at least one day, more preferably at least 2 days; more preferably at least 5 days; more preferably at least 10 days; more preferably at least 15 days; and most preferably at least 20 days. On the other hand, however, it may be more cost-effective and more friendly to the environment to apply the method of the invention not longer than necessary, and to transfer the young plant obtained with the method of the invention to the field as soon as possible. Therefore, it is preferred that the method of the invention is carried out for at most 300 days, more preferably at most 270 days; more preferably at most 240 days; more preferably at most 220 days; more preferably at most 200 days; more preferably at most 180 days; more preferably at most 170 days; more preferably at most 160 days; more preferably at most 150 days; more preferably at most 140 days; more preferably at most 130 days; more preferably at most 110 days; and most preferably at most 120 days. If the plant is a forest plant, in particular an Acacia plant, the method of the invention is preferably carried out for of from 50 to 160 days. If the plant is a mangrove plant, in particular Rhizophora, the method of the invention is preferably carried out for of from 60 to 140 days, preferably of from 70 to 125 days, and most preferably for of from 75 to 120 days. If the plant is a potato plant, the method of the invention is preferably carried out for of from 16 to 40 days, preferably of from 18 to 37 days, and most preferably for of from 20 to 35 days. If the plant is a strawberry plant, the method of the invention is preferably carried out for of from 34 to 46 days, preferably of from 36 to 44 days, and most preferably for of from 38 to 42 days. These periods relate to when the starting material is a seed of a plant, and a seedling is obtained therefrom by germinating said seed. As such, said periods include time for germination. When starting with a seedling directly, or when starting with a cutting or a tissue culture plant, the same periods apply minus said time for germination. Typically, during the method of the disclosure the root of the plant material will be kept in a substrate. The substrate may be soil or an aqueous solution, but it is preferred that the substrate is soil. However, it will be understood that during the method of the disclosure the plant material can be repotted if necessary, and thus the root may temporarily not be kept in a substrate. Likewise, horticultural substrates and horticultural nutrient solutions suitable for the growth of plants are known to the skilled person. Other parameters In principle, the methods of the disclosure work well, and accelerate the growth of plants. However, even better results are obtained if one or more other parameters are within certain ranges as well. These parameters are selected from the group consisting of space temperature, substrate temperature, relative humidity, CO concentration, electric 2 conductivity of the substrate, and the pH of the substrate. The preferred values of these parameters are detailed below. In the methods of the disclosure the best results are obtained if for all of these parameters the preferred values are used. The temperature of the plant material can be measured and adjusted using standard techniques known to the skilled person. Preferably, the plant material is kept at a temperature of at least 15°C; more preferably at least 16°C; more preferably at least 18°C; more preferably at least 19°C; more preferably at least 20°C; more preferably at least 21°C; and most preferably at least 22°C. Preferably, the plant material is kept at a temperature of at most 40°C; more preferably at most 37°C; more preferably at most 36°C; more preferably at most 35°C; more preferably at most 34°C; more preferably at most 33°C; more preferably at most 32°C; more preferably at most 31°C; more preferably at most 30°C; more preferably at most 29°C; and most preferably of at most 28°C. Preferably, the plant material is kept at a temperature in a range of from 15 to 40 °C; more preferably in a range of from 16 to 37 °C; more preferably in a range of from 18 to 36 °C; more preferably in a range of from 19 to 35 °C; more preferably in a range of from 20 to 34 °C; more preferably in a range of from 21 to 33 °C; and most preferably in a range of from 22 to 32 °C. More preferably, if the plant is a forest plant, in particular Acacia, or a mangrove plant, the plant material is kept at a temperature in a range of from 23 to 31 °C; more preferably in a range of from 24 to 30 °C; more preferably in a range of from 25 to 29 °C; and even more preferably in a range of from 26 to 28 °C. Most preferably, if the plant is a forest plant, in particular Acacia, the plant material is kept at a temperature of about 27 °C. Most preferably, if the plant is a mangrove plant, the plant material is kept at a temperature of about 28 °C. More preferably, if the plant is a potato plant, the plant material is kept at a temperature in a range of from 16 to 29 °C; more preferably in a range of from 17 to 28 °C; more preferably of from 18 to 27 and most preferably of from 20 to 25 °C. More preferably, if the plant is a strawberry plant, the plant material is kept at a temperature in a range of from 18 to 26 °C; more preferably in a range of from 20 to 24 °C; and most preferably at a temperature of about 22 °C. In the methods of the disclosure, it is also possible to separately control the space temperature (viz. the air temperature) and the substrate temperature. Thus, the temperature of the root of the plant material can be controlled by the substrate temperature, and the temperature of the shoot of the plant material can be controlled by the space temperature. Although some variation between the space temperature and the substrate temperature is allowed, it is preferred that the space temperature and the substrate temperature are substantially the same. Preferably, the root of the plant is kept at a temperature of at least 15°C; more preferably at least 16°C; more preferably at least 18°C; more preferably at least 19°C; more preferably at least 20°C; more preferably at least 21°C; and most preferably at least 22°C. Preferably, the root of the plant is kept at a temperature of at most 40°C; more preferably at most 37°C; more preferably at most 36°C; more preferably at most 35°C; more preferably at most 34°C; more preferably at most 33°C; more preferably at most 32°C; more preferably at most 31°C; more preferably at most 30°C; more preferably at most 29°C; and most preferably of at most 28°C. Preferably, the root of the plant is kept at a temperature in a range of from 15 to 40 °C; more preferably in a range of from 16 to 37 °C; more preferably in a range of from 18 to 36 °C; more preferably in a range of from 19 to 35 °C; more preferably in a range of from 20 to 34 °C; more preferably in a range of from 21 to 33 °C; and most preferably in a range of from 22 to 32 °C. More preferably, if the plant is a forest plant, in particular Acacia, or a mangrove plant, the root of the plant is kept at a temperature in a range of from 23 to 31 °C; more preferably in a range of from 24 to 30 °C; more preferably in a range of from 25 to 29 °C; and even more preferably in a range of from 26 to 28 °C. Most preferably, if the plant is a forest plant, in particular Acacia, the root of the plant is kept at a temperature of about 27 °C. Most preferably, if the plant is a mangrove plant, the root of the plant is kept at a temperature of about 28 °C. More preferably, if the plant is a potato plant, the root of the plant is kept at a temperature in a range of from 16 to 29 °C; more preferably in a range of from 17 to 28 °C; more preferably of from 18 to 27 and most preferably of from 20 to 25 °C. More preferably, if the plant is a strawberry plant, the root of the plant is kept at a temperature in a range of from 18 to 26 °C; more preferably in a range of from 20 to 24 °C; and most preferably at a temperature of about 22 °C. Preferably, the shoot of the plant is kept at a temperature of at least 15°C; more preferably at least 16°C; more preferably at least 18°C; more preferably at least 19°C; more preferably at least 20°C; more preferably at least 21°C; and most preferably at least 22°C. Preferably, the shoot of the plant is kept at a temperature of at most 40°C; more preferably at most 37°C; more preferably at most 36°C; more preferably at most 35°C; more preferably at most 34°C; more preferably at most 33°C; more preferably at most 32°C; more preferably at most 31°C; more preferably at most 30°C; more preferably at most 29°C; and most preferably of at most 28°C. Preferably, the shoot of the plant is kept at a temperature in a range of from 15 to 40 °C; more preferably in a range of from 16 to 37 °C; more preferably in a range of from 18 to 36 °C; more preferably in a range of from 19 to 35 °C; more preferably in a range of from 20 to 34 °C; more preferably in a range of from 21 to 33 °C; and most preferably in a range of from 22 to 32 °C. More preferably, if the plant is a forest plant, in particular Acacia, or a mangrove plant, the shoot of the plant is kept at a temperature in a range of from 23 to 31 °C; more preferably in a range of from 24 to 30 °C; more preferably in a range of from 25 to 29 °C; and even more preferably in a range of from 26 to 28 °C. Most preferably, if the plant is a forest plant, in particular Acacia, the shoot of the plant is kept at a temperature of about 27 °C. Most preferably, if the plant is a mangrove plant, the shoot of the plant is kept at a temperature of about 28 °C. More preferably, if the plant is a potato plant, the shoot of the plant is kept at a temperature in a range of from 16 to 29 °C; more preferably in a range of from 17 to 28 °C; more preferably of from 18 to 27 and most preferably of from 20 to 25 °C. More preferably, if the plant is a strawberry plant, the shoot of the plant is kept at a temperature in a range of from 18 to 26 °C; more preferably in a range of from 20 to 24 °C; and most preferably at a temperature of about 22 °C. The relative humidity of air can be measured and adjusted using standard techniques known to the skilled person. As used herein, “relative humidity” indicates a present state of absolute humidity relative to a maximum humidity given the same temperature. Therein, “absolute humidity” is the actual water content of the air, and is typically expressed as either mass of water vapor per volume of moist air (in grams per cubic meter) or as mass of water vapor per mass of dry air (usually in grams per kilogram) Preferably, the plant material is subjected to a relative humidity of at least 45%, and more preferably at least 60%. Preferably, the plant material is subjected to a relative humidity of at most 100%, and more preferably of at most 95%. Preferably, the plant material is subjected to a relative humidity in a range of from 45 to 100%. If the plant is a forest plant, in particular an Acacia plant, the plant material is preferably subjected to a relative humidity in a range of from 65 to 90%, preferably of from 70 to 85%, and most preferably of about 80%. If the plant is a mangrove plant, in particular Rhizophora, the plant material is preferably subjected to a relative humidity in a range of from 60 to 85%, preferably of from 65 to 80%, and most preferably of about 70%. If the plant is a potato plant, the plant material is preferably subjected to a relative humidity in a range of from 45 to 75%, preferably of from 47 to 70%, and most preferably of from 52 to 65%. If the plant is a strawberry plant, the plant material is preferably subjected to a relative humidity in a range of from 50 to 90%, preferably of from 55 to 85%, and most preferably of from 60 to 75%. The CO concentration in air can be measured and adjusted using standard techniques 2 known to the skilled person. Preferably, the plant material is subjected to air having a CO concentration of at least 2 250 ppm; more preferably at least 400 ppm; more preferably at least 500 ppm; more preferably at least 600 ppm; more preferably at least 700 ppm; more preferably at least 800 ppm; more preferably at least 900 ppm; more preferably at least 1000 ppm; more preferably at least 1100 ppm; more preferably at least 1200 ppm; more preferably at least 1300 ppm; and most preferably at least 1400 ppm. Preferably, the plant material is subjected to air having a CO concentration of at most 2 2750 ppm; more preferably at most 2600 ppm; more preferably at most ppm; more preferably at most 2500 ppm; more preferably at most 2400 ppm; more preferably at most 2300 ppm; more preferably at most 2200 ppm; more preferably at most 2100 ppm; more preferably at most 2000 ppm; more preferably at most 1900 ppm; more preferably at most 1800 ppm; more preferably at most 1700 ppm; and most preferably at most 1600 ppm. Preferably, the plant material is subjected to air having a CO concentration in a range 2 of from 250 to 2750 ppm; more preferably in a range of from 400 to 2600 ppm; more preferably in a range of from 500 to 2500 ppm; more preferably in a range of from 600 to 2400 ppm; more preferably in a range of from 700 to 2300 ppm; more preferably in a range of from 800 to 2200 ppm; and more preferably in a range of from 900 to 2100 ppm. If the plant is a forest plant, in particular Acacia, the plant material is preferably subjected to air having a CO concentration in a range of from 500 to 2000 ppm; more 2 preferably in a range of from 1100 to 1900 ppm; more preferably in a range of from 1200 to 1800 ppm; more preferably in a range of from 1300 to 1700 ppm; more preferably in a range of from 1400 to 1600 ppm; and most preferably about 1500 ppm. If the plant is a mangrove plant, a potato plant, or a strawberry plant, the plant material is preferably subjected to air having a CO concentration in a range of from 1000 to 2750 2 ppm; more preferably in a range of from 1500 to 2500 ppm; more preferably in a range of from 1750 to 2250 ppm; and most preferably about 2000 ppm. The electrical conductivity of the substrate can be measured and adjusted using standard techniques known to the skilled person. Preferably, the electrical conductivity of the substrate in which the plant material of 2 the plants grows is maintained at a value of at least 1.0 mS / cm , more preferably at least 1.2 2 2 2 mS / cm , more preferably at least 1.3 mS / cm , more preferably at least 1.4 mS / cm , and more 2 preferably at least 1.5 mS / cm . Preferably, the electrical conductivity of the substrate in which the plant material of 2 the plants grows is maintained at a value of at most 3.0 mS / cm , more preferably at most 2.9 2 2 2 mS / cm , more preferably at most 2.8 mS / cm , more preferably at most 2.7 mS / cm , more 2 2 preferably at most 2.6 mS / cm , more preferably at most 2.5 mS / cm , more preferably at most 2 2 2 2.4 mS / cm , more preferably at most 2.3 mS / cm , more preferably at most 2.2 mS / cm , and 2 most preferably at most 2.1 mS / cm . Preferably, the electrical conductivity of the substrate in which the plant material of 2 the plants grows is maintained from 1.1 to 2.8 mS / cm , more preferably of from 1.2 to 2.4 2 2 mS / cm , more preferably of from 1.3 to 2.3 mS / cm , more preferably of from 1.4 to 2.2 2 2 mS / cm , and most preferably in a range of from 1.5 to 2.1 mS / cm . If the plant is a forest plant, in particular Acacia, a mangrove plant, or a potato plant, the electrical conductivity of the substrate in which the plant material of the plants grows is 2 preferably maintained in a range of from 1.2 to 2.8 mS / cm , more preferably of from 1.8 to 2 2 2.2 mS / cm ; more preferably of from 1.9 to 2.1 mS / cm ; and most preferably at a value of 2 about 2.0 mS / cm . If the plant is a strawberry plant, the electrical conductivity of the substrate in which the plant material of the plants grows is preferably maintained in a range of from 1.2 to 2.0 2 2 mS / cm , more preferably of from 1.3 to 1.9 mS / cm ; more preferably of from 1.5 to 1.7 2 2 mS / cm ; and most preferably at a value of about 1.6 mS / cm . The pH of the soil can be measured and adjusted using standard techniques known to the skilled person. Preferably, the pH of the substrate in which the plant material of the plants grows is maintained at a value of at least 4.5, more preferably at least 4.8, more preferably at least 5.0, more preferably at least 5.1, more preferably at least 5.2, and more preferably at least 5.3. Preferably, the pH of the substrate in which the plant material of the plants grows is maintained at a value of at most 7.0, more preferably at most 6.8, more preferably at most 6.7, even more preferably at most 6.6, and more preferably at most 6.5. Preferably, the pH of the substrate in which the plant material of the plants grows is maintained in a range of from 4.5 to 7.0, more preferably of from 4.7 to 6.9, more preferably of from 4.9 to 6.7, more preferably of from 5.1 to 6.5. If the plant is a forest plant, in particular an Acacia plant, the pH of the substrate in which the plant material of the plants grows is preferably maintained in a range of from 5.2 to 6.3, more preferably of from 5.4 to 6.2, more preferably of from 5.6 to 6.1, more preferably of from 5.8 to 6.0, and most preferably about 5.9. If the plant is a mangrove plant, in particular an Acacia plant, the pH of the substrate in which the plant material of the plants grows is preferably maintained in a range of from 5.6 to 7.4, more preferably of from 5.8 to 7.2, more preferably of from 6.1 to 6.9, more preferably of from 6.4 to 6.6, and most preferably about 6.5. If the plant is a potato plant, in particular an Acacia plant, the pH of the substrate in which the plant material of the plants grows is preferably maintained in a range of from 5.2 to 6.4, more preferably of from 5.3 to 6.2, more preferably of from 5.5 to 6.0, more preferably of from 5.7 to 5.9, and most preferably about 5.8. If the plant is a strawberry plant, in particular an Acacia plant, the pH of the substrate in which the plant material of the plants grows is preferably maintained in a range of from 4.8 to 5.9, more preferably of from 5.0 to 5.7, more preferably of from 5.1 to 5.5, more preferably of from 5.2 to 5.4, and most preferably about 5.3. When multiple plants are grown simultaneously using a method of the invention, it is preferred that the leaf area index is at most 4, more preferably at most 3.7. In this way, the plant material can be optimally exposed to the artificial grow light. First days of a cutting or tissue culture plant If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then in the first 8 days, and most preferably the first 7 days it is preferred that the below values are used for the temperature, the relative humidity, and / or the artificial grow light. After said first days, it is preferred that the conditions as listed above are applied. If in a method of the disclosure the starting material is a seedling, it is preferred that the conditions as listed above are applied throughout conducting said method. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then in the first about 1 day, the artificial grow light preferably comprises a red component as defined herein. Then, the red component preferably has a photosynthetic flux 2 2 density of at least 30 µmol / m / s; more preferably at least 60 µmol / m / s; more preferably at 2 2 least 80 µmol / m / s; and most preferably at least 100 µmol / m / s. Then, the red component 2 preferably has a photosynthetic flux density of at most 190 µmol / m / s; more preferably at 2 2 most 160 µmol / m / s; more preferably at most 130 µmol / m / s; and most preferably at most 2 120 µmol / m / s. Then, preferably the red component has a photosynthetic flux density in a 2 2 range of from 30 to 190 µmol / m / s; more preferably of from 60 to 160 µmol / m / s; more 2 2 preferably of from 80 to 140 µmol / m / s; more preferably of from 90 to 130 µmol / m / s; and 2 most preferably of from 100 to 120 µmol / m / s. Then, most preferably the red component has 2 a photosynthetic flux density of about 110 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 2 to 3 of carrying out said method, the artificial grow light preferably comprises a red component as defined herein. Then, the red component preferably has a 2 2 photosynthetic flux density of at least 100 µmol / m / s; more preferably at least 115 µmol / m / s; 2 and most preferably at least 125 µmol / m / s. Then, the red component preferably has a 2 photosynthetic flux density of at most 185 µmol / m / s; more preferably at most 170 2 2 µmol / m / s; and most preferably at most 155 µmol / m / s. Then, preferably the red component 2 has a photosynthetic flux density in a range of from 100 to 185 µmol / m / s; more preferably of 2 2 from 115 to 170 µmol / m / s; and most preferably of from 125 to 155 µmol / m / s. Then, most 2 preferably the red component has a photosynthetic flux density of about 140 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 4 to 7 of carrying out said method, the artificial grow light preferably comprises a red component as defined herein. Then, the red component preferably has a 2 2 photosynthetic flux density of at least 130 µmol / m / s; more preferably at least 150 µmol / m / s; 2 and most preferably at least 170 µmol / m / s. Then, the red component preferably has a 2 photosynthetic flux density of at most 250 µmol / m / s; more preferably at most 230 2 2 µmol / m / s; and most preferably at most 210 µmol / m / s. Then, preferably the red component 2 has a photosynthetic flux density in a range of from 130 to 250 µmol / m / s; more preferably of 2 2 from 150 to 230 µmol / m / s; and most preferably of from 170 to 210 µmol / m / s. Then, most 2 preferably the red component has a photosynthetic flux density of about 190 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then in the first about 1 day, the artificial grow light preferably comprises a blue component as defined herein. Then, the blue component preferably has a photosynthetic flux 2 2 density of at least 20 µmol / m / s; more preferably at least 25 µmol / m / s; and most preferably 2 at least 30 µmol / m / s. Then, the blue component preferably has a photosynthetic flux density 2 2 of at most 50 µmol / m / s; more preferably at most 45 µmol / m / s; and most preferably at most 2 40 µmol / m / s. Then, preferably the blue component has a photosynthetic flux density in a 2 2 range of from 20 to 50 µmol / m / s; more preferably of from 25 to 45 µmol / m / s; and most 2 preferably of from 30 to 40 µmol / m / s. Then, most preferably the blue component has a 2 photosynthetic flux density of about 35 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 2 to 3 of carrying out said method, the artificial grow light preferably comprises a blue component as defined herein. Then, the blue component preferably has a 2 2 photosynthetic flux density of at least 30 µmol / m / s; more preferably at least 35 µmol / m / s; 2 and most preferably at least 40 µmol / m / s. Then, the blue component preferably has a 2 2 photosynthetic flux density of at most 60 µmol / m / s; more preferably at most 55 µmol / m / s; 2 and most preferably at most 50 µmol / m / s. Then, preferably the blue component has a 2 photosynthetic flux density in a range of from 30 to 60 µmol / m / s; more preferably of from 35 2 2 to 55 µmol / m / s; and most preferably of from 40 to 50 µmol / m / s. Then, most preferably the 2 blue component has a photosynthetic flux density of about 45 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 4 to 7 of carrying out said method, the artificial grow light preferably comprises a blue component as defined herein. Then, the blue component preferably has a 2 2 photosynthetic flux density of at least 40 µmol / m / s; more preferably at least 50 µmol / m / s; 2 and most preferably at least 60 µmol / m / s. Then, the blue component preferably has a 2 2 photosynthetic flux density of at most 90 µmol / m / s; more preferably at most 80 µmol / m / s; 2 and most preferably at most 70 µmol / m / s. Then, preferably the blue component has a 2 photosynthetic flux density in a range of from 40 to 90 µmol / m / s; more preferably of from 50 2 2 to 80 µmol / m / s; and most preferably of from 60 to 70 µmol / m / s. Then, most preferably the 2 blue component has a photosynthetic flux density of about 65 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then during the first about 3 days, the artificial grow light preferably comprises a far-red component as defined herein. Then, the far-red component preferably has a photosynthetic 2 2 flux density of at least 1 µmol / m / s; more preferably at least 3 µmol / m / s; more preferably at 2 2 least 5 µmol / m / s; more preferably at least 7 µmol / m / s; more preferably at least 10 2 2 µmol / m / s; and most preferably at least 12 µmol / m / s. Then, the far-red component preferably 2 has a photosynthetic flux density of at most 30 µmol / m / s; more preferably at most 25 2 2 2 µmol / m / s; more preferably at most 22 µmol / m / s; more preferably at most 20 µmol / m / s; 2 2 more preferably at most 19 µmol / m / s; and most preferably at most 17 µmol / m / s. Then, preferably the far-red component has a photosynthetic flux density in a range of from 1 to 30 2 2 µmol / m / s; more preferably of from 3 to 25 µmol / m / s; more preferably of from 5 to 22 2 2 µmol / m / s; more preferably of from 7 to 20 µmol / m / s; more preferably of from 10 to 19 2 2 µmol / m / s; and most preferably of from 12 to 17 µmol / m / s. Then, most preferably the far-red 2 component has a photosynthetic flux density of about 15 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 4 to 7 of carrying out said method, the artificial grow light preferably comprises a far-red component as defined herein. Then, the far-red component preferably has 2 2 a photosynthetic flux density of at least 15 µmol / m / s; more preferably at least 20 µmol / m / s; 2 and most preferably at least 22 µmol / m / s. Then, the far-red component preferably has a 2 2 photosynthetic flux density of at most 35 µmol / m / s; more preferably at most 30 µmol / m / s; 2 and most preferably at most 28 µmol / m / s. Then, preferably the far-red component has a 2 photosynthetic flux density in a range of from 15 to 35 µmol / m / s; more preferably of from 20 2 2 to 30 µmol / m / s; and most preferably of from 22 to 28 µmol / m / s. Then, most preferably the 2 far-red component has a photosynthetic flux density of about 25 µmol / m / s. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then in the first about 3 days, the relative humidity of the air is preferably at least 75%, more preferably at least 80%, more preferably at least 85%, and most preferably at least 88%. Then, the relative humidity of the air is preferably at most 99%, more preferably at most 97%, more preferably at most 95%, and most preferably at most 92%. Then, the relative humidity of the air is preferably of in a range from 75 to 99%, more preferably of from 80 to 97%, more preferably of from 85 to 95%, and most preferably of from 88 to 92%. Then, most preferably the relative humidity of the air is about 90%. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 4 to 7 of carrying out said method, the relative humidity of the air is preferably at least 75%, more preferably at least 78%, more preferably at least 81% and most preferably at least 83%. Then, the relative humidity of the air is preferably at most 95%, more preferably at most 92% more preferably at most 89%, and most preferably at most 87%. Then, the relative humidity of the air is preferably of in a range from 75 to 95%, more preferably of from 78 to 92%, more preferably of from 81 to 89%, and most preferably of from 83 to 87%. Then, most preferably the relative humidity of the air is about 85%. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then during the first about 1 day of carrying out said method, it is preferred that the cutting or the tissue culture plant is kept at a temperature of at least 17°C; more preferably at least 18°C; and most preferably at least 19°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature of at most 23°C; more preferably at most 22°C; and most preferably at most 21°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature in a range of from 17 to 23°C; more preferably of from 18 to 22°C; and most preferably of from 19 to 21°C. Then, most preferably the cutting or the tissue culture plant is kept at a temperature of about 20°C. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 2 to 3 of carrying out said method, it is preferred that the cutting or the tissue culture plant is kept at a temperature of at least 19°C; more preferably at least 20°C; and most preferably at least 21°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature of at most 25°C; more preferably at most 24°C; and most preferably at most 23°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature in a range of from 19 to 25°C; more preferably of from 20 to 24°C; and most preferably of from 21 to 23°C. Then, most preferably the cutting or the tissue culture plant is kept at a temperature of about 22°C. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then on days 4 to 7 of carrying out said method, it is preferred that the cutting or the tissue culture plant is kept at a temperature of at least 22°C; more preferably at least 23°C; and most preferably at least 24°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature of at most 28°C; more preferably at most 27°C; and most preferably at most 26°C. Then, preferably the cutting or the tissue culture plant is kept at a temperature in a range of from 22 to 28°C; more preferably of from 23 to 27°C; and most preferably of from 24 to 26°C. Then, most preferably the cutting or the tissue culture plant is kept at a temperature of about 25°C. If in a method of the disclosure the starting material is a cutting or a tissue culture plant, then for the first about 7 days of carrying out said method, it is preferred that the substrate temperature and the space temperature are substantially the same. Methods for mangrove plants Several preferred features for methods of the invention for growing mangrove plants are already indicated above. Furthermore, when growing mangrove plants using methods of the invention, it is also preferred that the leaf area index about 75 days after sowing is in a range of from 0.6 to 1.5, preferably about 1.1. Preferably, the leaf area index about 120 days after sowing is in a range of from 1.2 to 2.1, preferably about 1.8. Methods for potato plants Several preferred features for methods of the invention for growing potato plants are already indicated above. Furthermore, when growing potato plants using methods of the invention, the following features are also preferred. Preferably, the artificial grow light comprises a red component and a blue component. Preferably, from about day 6 until about day 20 after sowing the artificial grow light essentially consists of a red component and a blue component. Preferably, from about day 21 onwards the artificial grow light comprises a red component, a blue component, and a far-red component; and more preferably essentially consists of a red component, a blue component, and a far-red component. Preferably, when growing a potato plant using a method of the invention the red 2 component has a photosynthetic flux density of at least 125 µmol / m / s; more preferably at 2 2 least 150 µmol / m / s; and most preferably at least 175 µmol / m / s. Preferably, when growing a potato plant using a method of the invention the red component has a photosynthetic flux 2 2 density of at most 300 µmol / m / s; more preferably at most 250 µmol / m / s; and most 2 preferably at most 225 µmol / m / s. Preferably, when growing a potato plant using a method of the invention the red component has a photosynthetic flux density in a range of from 125 to 2 2 300 µmol / m / s; more preferably in a range of from 150 to 250 µmol / m / s; and most 2 preferably of from 175 to 225 µmol / m / s. Most preferably, when growing a potato plant using a method of the invention the red component has a photosynthetic flux density of about 200 2 µmol / m / s. Preferably, from about day 6 until about day 20 after sowing the blue component has a 2 2 photosynthetic flux density of at least 20 µmol / m / s; more preferably at least 30 µmol / m / s; 2 and most preferably at least 40 µmol / m / s. Preferably, from about day 6 until about day 80 2 after sowing the blue component has a photosynthetic flux density of at most 70 µmol / m / s; 2 2 more preferably at most 60 µmol / m / s; and most preferably at most 42 µmol / m / s. Preferably, from about day 6 until about day 20 after sowing the blue component has a photosynthetic 2 flux density in a range of from 20 to 80 µmol / m / s; more preferably in a range of from 30 to 2 2 70 µmol / m / s; and most preferably of from 40 to 60 µmol / m / s. Most preferably, from about day 6 until about day 20 after sowing the blue component has a photosynthetic flux density of 2 about 50 µmol / m / s. Preferably, from about day 21 onwards after sowing the blue component has a 2 2 photosynthetic flux density of at least 85 µmol / m / s; more preferably at least 80 µmol / m / s; 2 and most preferably at least 85 µmol / m / s. Preferably, from about day 21 onwards after 2 sowing the blue component has a photosynthetic flux density of at most 110 µmol / m / s; more 2 2 preferably at most 100 µmol / m / s; and most preferably at most 95 µmol / m / s. Preferably, from about day 21 onwards after sowing the blue component has a photosynthetic flux density 2 in a range of from 70 to 110 µmol / m / s; more preferably in a range of from 80 to 100 2 2 µmol / m / s; and most preferably of from 85 to 95 µmol / m / s. Most preferably, from about day 21 onwards after sowing the blue component has a photosynthetic flux density of about 90 2 µmol / m / s. Preferably, from about day 21 onwards after sowing the far-red component has a 2 2 photosynthetic flux density of at least 15 µmol / m / s; more preferably at least 20 µmol / m / s; 2 and most preferably at least 25 µmol / m / s. Preferably, from about day 21 onwards after 2 sowing the far-red component has a photosynthetic flux density of at most 50 µmol / m / s; 2 2 more preferably at most 40 µmol / m / s; and most preferably at most 35 µmol / m / s. Preferably, from about day 21 onwards after sowing the far-red component has a photosynthetic flux 2 density in a range of from 15 to 50 µmol / m / s; more preferably in a range of from 20 to 40 2 2 µmol / m / s; and most preferably of from 25 to 35 µmol / m / s. Most preferably, from about day 21 onwards after sowing the far-red component has a photosynthetic flux density of about 30 2 µmol / m / s. Preferably, from about day 6 until about day 20 the leaf area index is in a range of from 3 to 4, preferably about 3.7. Preferably, from about day 26 onwards the leaf area index is in a range of from 0.6 to 1.0, preferably about 0.8. Methods for strawberry plants Several preferred features for methods of the invention for growing strawberry plants are already indicated above. Furthermore, when growing strawberry plants using methods of the invention, the following features are also preferred. Preferably, the artificial grow light comprises a red component and a blue component, and more preferably essentially consists of a red component and a blue component. Preferably, from about day 8 until about day 14 after sowing the red component has a 2 2 photosynthetic flux density of at least 90 µmol / m / s; more preferably at least 100 µmol / m / s; 2 and most preferably at least 110 µmol / m / s. Preferably, from about day 8 until about day 14 2 after sowing the red component has a photosynthetic flux density of at most 150 µmol / m / s; 2 2 more preferably at most 140 µmol / m / s; and most preferably at most 130 µmol / m / s. Preferably, from about day 8 until about day 14 after sowing the red component has a 2 photosynthetic flux density in a range of from 90 to 150 µmol / m / s; more preferably in a 2 2 range of from 100 to 140 µmol / m / s; and most preferably of from 110 to 130 µmol / m / s. Most preferably, from about day 8 until about day 14 after sowing the red component has a 2 photosynthetic flux density of about 122 µmol / m / s. Preferably, from about day 8 until about day 14 after sowing the blue component has a 2 2 photosynthetic flux density of at least 25 µmol / m / s; more preferably at least 30 µmol / m / s; 2 and most preferably at least 32 µmol / m / s. Preferably, from about day 8 until about day 14 2 after sowing the blue component has a photosynthetic flux density of at most 60 µmol / m / s; 2 2 more preferably at most 50 µmol / m / s; and most preferably at most 42 µmol / m / s. Preferably, from about day 8 until about day 14 after sowing the blue component has a photosynthetic 2 flux density in a range of from 25 to 60 µmol / m / s; more preferably in a range of from 30 to 2 2 50 µmol / m / s; and most preferably of from 32 to 42 µmol / m / s. Most preferably, from about day 8 until about day 14 after sowing the blue component has a photosynthetic flux density of 2 about 37 µmol / m / s. Preferably, from about day 15 until about day 40 after sowing the red component has a 2 2 photosynthetic flux density of at least 220 µmol / m / s; more preferably at least 230 µmol / m / s; 2 and most preferably at least 235 µmol / m / s. Preferably, from about day 15 until about day 40 2 after sowing the red component has a photosynthetic flux density of at most 275 µmol / m / s; 2 2 more preferably at most 260 µmol / m / s; and most preferably at most 250 µmol / m / s. Preferably, from about day 15 until about day 40 after sowing the red component has a 2 photosynthetic flux density in a range of from 220 to 275 µmol / m / s; more preferably in a 2 2 range of from 230 to 260 µmol / m / s; and most preferably of from 235 to 250 µmol / m / s. Most preferably, from about day 15 until about day 40 after sowing the red component has a 2 photosynthetic flux density of about 245 µmol / m / s. Preferably, from about day 15 until about day 40 after sowing the blue component has 2 2 a photosynthetic flux density of at least 60 µmol / m / s; more preferably at least 65 µmol / m / s; 2 and most preferably at least 70 µmol / m / s. Preferably, from about day 15 until about day 40 2 after sowing the blue component has a photosynthetic flux density of at most 100 µmol / m / s; 2 2 more preferably at most 85 µmol / m / s; and most preferably at most 80 µmol / m / s. Preferably, from about day 15 until about day 40 after sowing the blue component has a photosynthetic 2 flux density in a range of from 60 to 100 µmol / m / s; more preferably in a range of from 65 to 2 2 85 µmol / m / s; and most preferably of from 70 to 80 µmol / m / s. Most preferably, from about day 15 until about day 40 after sowing the blue component has a photosynthetic flux density 2 of about 75 µmol / m / s. Preferably, from about day 8 until about day 14 after sowing the leaf area index is in a range of from 2 to 3, preferably about 2.5. Preferably, from about day 15 onwards the leaf area index is in a range of from 2.5 to 4, preferably about 3. Germination methods Herein, preferred methods for germinating a seed of a plant are described. The steps of these methods may precede the steps of the method of the invention, if the starting material in the latter method is a seed. Preferably, the method for germinating a seed of a plant so as to obtain a seedling comprises the steps of: (a) providing a seed of a plant; (b) covering said seed with soil; preferably burying said seed in soil; wherein said soil is in contact with air; and (c) allowing the seed to germinate. When germinating seed from a forest plant, in particular a plant of the genus Acacia, preferably one or more of the following conditions are applied for about 30 days: (i) maintaining the soil temperature in a range of from 25 to 35 °C; preferably in a range of from 27 to 33 °C; more preferably in a range of from 29 to 31 °C; and most preferably at about 30 °C; (ii) maintaining the relative humidity of the air in a range of from 85 to 95%; preferably in a range of from 87 to 92%; and most preferably at about 90%; (iii) maintaining the CO 2 concentration in the air in a range of from 300 to 700 ppm; preferably of from 320 to 650 ppm; more preferably of from 350 to 550 ppm; more preferably of from 370 to 470 ppm; more preferably of from 400 to 440 ppm; and most preferably at about 420 ppm. When germinating seed from a potato plant, preferably one or more of the following conditions are applied for about 5 days: (i) maintaining the soil temperature in a range of from 17 to 20 °C; and most preferably at about 18.5 °C; (ii) maintaining the relative humidity of the air in a range of from 85 to 95%; and most preferably at about 90%; (iii) maintaining the CO 2 concentration in the air in a range of from 300 to 700 ppm; and most preferably at about 420 2 ppm; and (iv) a plant density of from 600-700 plants per m ; most preferably about 666 plants 2 per m . When germinating seed from a strawberry plant, preferably one or more of the following conditions are applied for about 5 days: (i) maintaining the soil temperature in a range of from 20 to 24 °C; and most preferably at about 22 °C; (ii) maintaining the relative humidity of the air in a range of from 85 to 100%; and most preferably at about 90% to about 95%; (iii) maintaining the CO concentration in the air in a range of from 1500 to 2500 ppm; 2 and most preferably at about 2000 ppm; and (iv) a plant density of from 900-960 plants per 2 2 m ; most preferably about 937 plants per m . Preferably, at the end of the germination phase the leaf area index is in a range of from 2.5 to 4, preferably about 3. Preferably, in the germination method the seed is not exposed to artificial grow light. More preferably, in the germination method the seed is kept in the dark. Preferably, in the germination method the seed is sowed in a container, preferably a pot, having a volume in a range of from 20 to 90 mL, most preferably about 25 mL, about 30 mL, or about 75 mL. Plants The invention also relates to plants per se. Preferably, the plant is obtainable by a method as disclosed herein. Plants of the invention are distinguishable from known plants, in particular when grown outdoors using traditional conditions, by being of better quality. In particular, plants of the invention have a larger total dry weight, a larger total leaf area, lower susceptibility to plagues and diseases, faster production rate after transfer to an outdoor field, and / or higher survival rate after transfer to an outdoor field. Several preferred plants are indicated below. In a preferred embodiment, the plant is a forest plant, more preferably a plant of the species Acacia nilotica. 2 Preferably, the forest plant has a total leaf area of at least 725 cm ; more preferably at 2 2 2 least 1000 cm ; more preferably at least 1100 cm ; more preferably at least 1150 cm ; more 2 2 preferably at least 1200 cm ; and most preferably at least 1225 cm . Preferably, the forest 2 2 plant has a total leaf area of at most 4000 cm ; more preferably at most 3500 cm ; more 2 2 preferably at most 3000 cm ; more preferably at most 2750 cm ; more preferably at most 2 2 2600 cm ; and most preferably at most 2200 cm . Preferably, the forest plant has a total leaf 2 2 area in a range of from 900 to 4000 cm ; more preferably of from 1000 to 3500 cm ; more 2 2 preferably of from 1100 to 3000 cm ; more preferably of from 1150 to 2750 cm ; more 2 2 preferably of from 1150 to 2600 cm ; and most preferably of from 1200 to 2200 cm . 2 2 Preferably, the forest plant has a total leaf area of about 1225 cm , or about 1750 cm . Preferably, the forest plant has a total dry weight of at least 6.0 gram; more preferably at least 6.5 gram; more preferably at least 7.0 gram; more preferably at least 10 gram; more preferably at least 15 gram; and most preferably at least 17 gram. Preferably, the forest plant has a total dry weight of at most 50 gram; more preferably at most 45 gram; more preferably at most 40 gram; more preferably at most 35 gram; more preferably at most 30 gram; and most preferably at most 25 gram. Preferably, the forest plant has a total dry weight in a range of from 6.0 to 50 gram; more preferably of from 6.5 to 45 gram; more preferably of from 7.0 to 40 gram; more preferably of from 10 to 35 gram; more preferably of from 15 to 30 gram; and most preferably of from 17 to 25 gram. Preferably, the forest plant has a total dry weight of about 20 gram. In other embodiments, however, the forest plant has a total dry weight of about 8.0 gram. Preferably, the forest plant has an average internode length of at least 3.5 cm; more preferably at least 4.0 cm; more preferably at least 4.5 cm; more preferably at least 5.0 cm; more preferably at least 5.5 cm; and most preferably at least 6.0 cm. Preferably, the forest plant has a average internode length of at most 17 cm; more preferably at most 15 cm; more preferably at most 14 cm; more preferably at most 13 cm; more preferably at most 12 cm; and most preferably at most 11 cm. Preferably, the forest plant has a average internode length in a range of from 3.5 to 17 cm; more preferably of from 4.0 to 15 cm; more preferably of from 4.5 to 14 cm; more preferably of from 5.0 to 13 cm; more preferably of from 5.5 to 12 cm; and most preferably of from 6.0 to 11 cm. Preferably, the forest plant has a average internode length of about 6.4 cm, or about 10 cm. Preferably, the forest plant has a height of at least 20 cm; more preferably at least 25 cm; more preferably at least 30 cm; more preferably at least 35 cm; more preferably at least 40 cm; and most preferably at least 45 cm. Preferably, the forest plant has a height of at most 200 cm; more preferably at most 175 cm; more preferably at most 150 cm; more preferably at most 130 cm; more preferably at most 125 cm; and most preferably at most 120 cm. Preferably, the forest plant has a height in a range of from 20 to 200 cm; more preferably of from 25 to 175 cm; more preferably of from 30 to 150 cm; more preferably of from 35 to 130 cm; more preferably of from 40 to 125 cm; and most preferably of from 45 to 120 cm. Preferably, the forest plant has a height of about 45 cm, about 65 cm, or about 100 cm. Preferably, the forest plant has a ratio of the dry weight of the shoot over the dry weight of the root of at least 1:0.6, more preferably at least 1:0.5, more preferably at least 1:0.4, and most preferably at least 1:0.35. Preferably, the forest plant has a ratio of the dry weight of the shoot over the dry weight of the root of at most 1:0.05, more preferably at most 1:0.1, more preferably at most 1:0.2, and most preferably at most 1:0.25. Preferably, the forest plant has a ratio of the dry weight of the shoot over the dry weight of the root in a range of from 1:0.6 to 1:0.05, more preferably of from 1:0.5 to 1:0.1, more preferably of from 1:0.4 to 1:0.2, and most preferably of from 1:0.35 to 1:0.25. Most preferably, the forest plant has a ratio of the dry weight of the shoot over the dry weight of the root of about 1:0.3. Preferably, the forest plant has a number of leaf pairs on the main stem of at least 6, more preferably at least 7, more preferably at least 8, and most preferably at least 9. Preferably, the forest plant has a number of leaf pairs on the main stem of at most 18, more preferably at most 16, more preferably at most 13, and most preferably at most 11. Preferably, the forest plant has a number of leaf pairs on the main stem in a range of from 6 to 18, more preferably of from 7 to 16, more preferably of from 8 to 13, and most preferably of from 9 to 11. Most preferably, the forest plant has a number of leaf pairs on the main stem of about 10. In other embodiments, the forest plant has a number of leaf pairs on the main stem of about 7. In another preferred embodiment, the plant is a mangrove plant, more preferably a plant of the species Rhizophora mangle. 2 Preferably, the mangrove plant has a total leaf area of at least 80 cm ; more preferably 2 2 at least 100 cm ; and most preferably at least 150 cm . Preferably, the mangrove plant has a 2 2 total leaf area of at most 400 cm ; more preferably at most 350 cm ; and most preferably at 2 most 300 cm . Preferably, the mangrove plant has a total leaf area in a range of from 80 to 2 2 400 cm ; more preferably of from 100 to 350 cm ; and most preferably of from 150 to 325 2 2 2 cm . Preferably, the mangrove plant has a total leaf area of about 180 cm , or about 300 cm . Preferably, the mangrove plant has a total dry weight of at least 12 gram, more preferably at least 14 gram; and most preferably at least 15 gram. Preferably, the mangrove plant has a total dry weight of at most 25 gram; more preferably at most 21 gram; and most preferably at most 19 gram. Preferably, the mangrove plant has a total dry weight in a range of from 12 to 25 gram; more preferably of from 14 to 21 gram; and most preferably of from 15 to 19 gram. Preferably, the mangrove plant has a total dry weight of about 17 gram. Preferably, the mangrove plant has an average internode length of at least 3.5 cm; more preferably at least 4.0 cm; and most preferably at least 5.0 cm. Preferably, the mangrove plant has an average internode length of at most 11 cm; more preferably at most 9 cm; and most preferably at most 7.0 cm. Preferably, the mangrove plant has an average internode length in a range of from 3.5 to 11 cm; more preferably of from 4.0 to 9 cm; and most preferably of from 5.0 to 7.0 cm. Preferably, the mangrove plant has a average internode length of about 6.0 cm. Preferably, the mangrove plant has a height of at least 25 cm; more preferably at least 30 cm; and most preferably at least 35 cm. Preferably, the mangrove plant has a height of at most 65 cm; more preferably at most 60 cm; and most preferably at most 55 cm. Preferably, the mangrove plant has a height in a range of from 25 to 65 cm; more preferably of from 30 to 60 cm; and most preferably of from 35 to 55 cm. Preferably, the mangrove plant has a height of about 40 cm, or about 50 cm. Preferably, the mangrove plant has a ratio of the dry weight of the shoot over the dry weight of the root of at least 2.0, more preferably at least 2.5, and most preferably at least 3.0. Preferably, the mangrove plant has a ratio of the dry weight of the shoot over the dry weight of the root of at most 5.0, more preferably at most 4.5, and most preferably at most 4.0. Preferably, the mangrove plant has a ratio of the dry weight of the shoot over the dry weight of the root in a range of from 2.0 to 5.0, more preferably of from 2.5 to 4.5, and most preferably of from 3.0 to 4.0. Most preferably, the mangrove plant has a ratio of the dry weight of the shoot over the dry weight of the root of about 3.5 or 3.8. Preferably, the mangrove plant has a number of leaf pairs on the main stem of at least 1, and most preferably at least 2. Preferably, the mangrove plant has a number of leaf pairs on the main stem of at most 6, and most preferably at most 5. Preferably, the mangrove plant has a number of leaf pairs on the main stem in a range of from 1 to 6, and most preferably of from 2 to 5. Most preferably, the mangrove plant has a number of leaf pairs on the main stem of about 3 or about 4. In another preferred embodiment, the plant is a potato plant, more preferably a plant of the species Solanum tuberosum. 2 Preferably, the potato plant has a total leaf area of at least 35 cm ; more preferably at 2 2 least 46 cm ; and most preferably at least 50 cm . Preferably, the potato plant has a total leaf 2 2 area of at most 600 cm ; more preferably at most 550 cm ; and most preferably at most 500 2 2 cm . Preferably, the potato plant has a total leaf area in a range of from 35 to 600 cm ; more 2 2 preferably of from 46 to 550 cm ; and most preferably of from 50 to 500 cm . Preferably, the 2 2 potato plant has a total leaf area of about 55 cm , or about 456 cm . Preferably, the potato plant has a total dry weight of at least 0.10 gram, more preferably at least 0.14 gram; and most preferably at least 0.16 gram. Preferably, the potato plant has a total dry weight of at most 3.0 gram; more preferably at most 2.4 gram; and most preferably at most 2.3 gram. Preferably, the potato plant has a total dry weight in a range of from 0.10 to 3.0 gram; more preferably of from 0.14 to 2.4 gram; and most preferably of from 0.16 to 2.3 gram. Preferably, the potato plant has a total dry weight of about 0.17 gram or about 2.19 gram. Preferably, the potato plant has a height of at least 3.5 cm; more preferably at least 4.0 cm; and most preferably at least 4.2 cm. Preferably, the potato plant has a height of at most 6.0 cm; more preferably at most 5.0 cm; and most preferably at most 4.7 cm. Preferably, the potato plant has a height in a range of from 3.5 to 6.0 cm; more preferably of from 4.0 to 5.0 cm; and most preferably of from 4.2 to 4.7 cm. Preferably, the potato plant has a height of about 4.5 cm. Preferably, the potato plant has a number of leaf pairs on the main stem of at least 4, and most preferably at least 5. Preferably, the potato plant has a number of leaf pairs on the main stem of at most 10, and most preferably at most 9. Preferably, the potato plant has a number of leaf pairs on the main stem in a range of from 4 to 10, and most preferably of from 5 to 9. Most preferably, the potato plant has a number of leaf pairs on the main stem of about 6, or about 8. In another preferred embodiment, the plant is a strawberry plant, preferably of the species Fragaria × ananassa. Preferably, the strawberry plant is an F1 hybrid strawberry plant, and more preferably the strawberry plant is of the variety Dellizimo. Arrangement The disclosure also relates to an arrangement for carrying out the method of the invention, in particular for growing a plant under such conditions that a young plant with a better quality is obtained and / or a young plant is obtained sooner, as compared to a standard outdoors-grown plant. The arrangement comprises the plant material and a lighting device configured to provide artificial grow light to the plant material. The artificial grow light is preferably as defined herein. Preferably, the lighting device is configured to communicate with a light controller configured to control the lighting device. In principle, any suitable light source can be used. However, preferably the lighting device comprises one or more light-emitting diodes (LEDs). More preferably, the lighting device comprises a light-emitting diode configured to provide the red component as defined herein. More preferably, the lighting device comprises a light-emitting diode configured to provide the blue component as defined herein. More preferably, the lighting device comprises a light-emitting diode configured to provide the far-red component as defined herein. Even more preferably, the lighting device comprises a light-emitting diode configured to provide the red component as defined herein, and a light-emitting diode configured to provide the blue component as defined herein. Most preferably, the lighting device comprises a light-emitting diode configured to provide the red component as defined herein, a light-emitting diode configured to provide the blue component as defined herein, and a light-emitting diode configured to provide the far-red component as defined herein. The arrangement preferably further comprises an air temperature adjustment device configured to adjust the air temperature. During operation the air temperature adjustment device may be used to maintain the air temperature at a temperature as defined above. Temperature adjustment devices such as heating and cooling adjustment devices are well- known to the skilled person. Preferably, the air temperature adjustment device is configured to communicate with an air temperature controller. The air temperature controller is configured to control the air temperature adjustment device. Preferably, the arrangement further comprises an air temperature sensor configured to measure the air temperature. Preferably, the air temperature sensor is configured to communicate with the air temperature adjustment device and / or the air temperature controller. Preferably, the air temperature controller is configured to control the air temperature adjustment device in dependence of communication received by the air temperature controller from the air temperature sensor. The arrangement preferably further comprises a substrate temperature adjustment device configured to adjust the substrate temperature. During operation the substrate temperature adjustment device may be used to maintain the substrate temperature at a temperature as defined above. Temperature adjustment devices such as heating and cooling adjustment devices are well-known to the skilled person. Preferably, the substrate temperature adjustment device is configured to communicate with a substrate temperature controller. The substrate temperature controller is configured to control the substrate temperature adjustment device. Preferably, the arrangement further comprises a substrate temperature sensor configured to measure the substrate temperature. Preferably, the substrate temperature sensor is configured to communicate with the substrate temperature adjustment device and / or the substrate temperature controller. Preferably, the substrate temperature controller is configured to control the substrate temperature adjustment device in dependence of communication received by the substrate temperature controller from the substrate temperature sensor. Preferably, the arrangement further comprises a humidity adjustment device configured to adjust the relative humidity. During operation the humidity adjustment device may be used to maintain the relative humidity as defined above. For example, the humidity adjustment device may absorb and / or release moisture from the air to adjust the relative humidity. Preferably, the humidity adjustment device is configured to communicate with a humidity controller. The humidity controller is configured to control the humidity adjustment device as defined herein. During operation, the humidity controller and the humidity adjustment device may be used to maintain the relative humidity as defined above. Preferably, the arrangement further comprises a humidity sensor configured to measure the relative humidity. Preferably, the humidity sensor is configured to communicate with the humidity adjustment device and / or the humidity controller. Preferably, the humidity controller is configured to control the humidity adjustment device in dependence of communication received by the humidity controller from the humidity sensor. Preferably, the arrangement comprises a CO adjustment device configured to adjust 2 the CO concentration of air. During operation the CO adjustment device may be used to 2 2 maintain the CO concentration of air as defined above. For example, the CO adjustment 2 2 device may absorb and / or release carbon dioxide from or to the air to adjust the CO 2 concentration of the air. Preferably, the CO adjustment device is configured to communicate with a CO 2 2 controller. The CO controller is configured to control the CO adjustment device as defined 2 2 herein. During operation, the CO controller and the CO adjustment device may be used to 2 2 maintain the CO concentration in the air as defined above. 2 Preferably, the arrangement further comprises a CO sensor configured to measure the 2 CO concentration in the air. Preferably, the CO sensor is configured to communicate with 2 2 the CO adjustment device and / or the CO controller. Preferably, the CO controller is 2 2 2 configured to control the CO adjustment device in dependence of communication received 2 by the CO controller from the CO sensor. 2 2 Preferably, the arrangement comprises a conductivity adjustment device configured to adjust the electrical conductivity of the substrate. It will be understood that if herein reference is made to “conductivity” without the adjective “electrical”, “electrical conductivity” is nevertheless meant. During operation the conductivity adjustment device may be used to maintain the electrical conductivity of the substrate as defined above. For example, the conductivity adjustment device may absorb and / or release water and / or salts from or to the substrate to adjust the electrical conductivity. Preferably, the conductivity adjustment device adjusts the electrical conductivity of the water that is provided to the substrate. Preferably, the conductivity adjustment device is configured to communicate with a conductivity controller. The conductivity controller is configured to control the conductivity adjustment device as defined herein. During operation, the conductivity controller and the conductivity adjustment device may be used to maintain the electrical conductivity as defined above. Preferably, the arrangement further comprises a conductivity sensor configured to measure the electrical conductivity. Preferably, the conductivity sensor is configured to communicate with the conductivity adjustment device and / or the conductivity controller. Preferably, the conductivity controller is configured to control the conductivity adjustment device in dependence of communication received by the conductivity controller from the conductivity sensor. Preferably, the arrangement comprises a pH adjustment device configured to adjust the pH of the substrate. During operation the pH adjustment device may be used to maintain the pH of the substrate as defined above. For example, the pH adjustment device may absorb and / or release water, acidic substances, and / or basic substances from or to the substrate to adjust the pH. It will be understood that “basic” as used herein refers to Brønsted bases. Preferably, the pH adjustment device adjusts the pH of the water that is provided to the substrate. Preferably, the pH adjustment device is configured to communicate with a pH controller. The pH controller is configured to control the pH adjustment device as defined herein. During operation, the pH controller and the pH adjustment device may be used to maintain the pH of the substrate as defined above. Preferably, the arrangement further comprises a pH sensor configured to measure the pH of the substrate. The pH of the substrate can be measured directly on the substrate, but it is preferred that the pH of the substrate is determined by measuring the pH of the water provided to or obtained from the substrate. Preferably, the pH sensor is configured to communicate with the pH adjustment device and / or the pH controller. Preferably, the pH controller is configured to control the pH adjustment device in dependence of communication received by the pH controller from the pH sensor. Most preferably, the arrangement further comprises the air temperature adjustment device, the substrate temperature adjustment device, the humidity adjustment device, the CO 2 adjustment device, the conductivity adjustment device, and the pH adjustment device. It will be understood that one adjustment device may be configured to adjust more than one parameter. As such, the CO adjustment device may for example also be configured 2 to adjust the relative humidity, and / or the air temperature. Likewise, the pH adjustment device may for example also be configured to adjust the electrical conductivity of the substrate. In other words: the various adjustment devices as disclosed herein may be combined, preferably integrated. Most preferably, the arrangement further comprises the air temperature sensor, the substrate temperature sensor, the humidity sensor, the CO sensor, the conductivity sensor, 2 and the pH sensor. It will be understood that the aforementioned adjustment devices and the aforementioned sensors may be integrated, in particular such that a respective sensor is integrated with a respective adjustment device. For example, the pH sensor may be comprised in the pH adjustment device. Alternatively, the sensor and the adjustment device are physically separated. This may reduce the influence of the adjustment device on the measurements of the sensor, e.g. if the adjustment device releases acid to adjust the pH the concentration of acid close to the adjustment device may be temporarily high as the acid diffuses into the substrate. Preferably, the arrangement further comprises the air temperature controller, the substrate temperature controller, the humidity controller, the CO controller, the conductivity 2 controller, and / or the pH controller. More preferably, the arrangement further comprises the air temperature controller, the substrate temperature controller, the humidity controller, the CO controller, the conductivity controller, and the pH controller. 2 It will be understood that the communication between the controller and the respective (adjustment) device and / or sensor may be via wires or wireless, wherein wireless communication is preferred. Preferably, the (adjustment) device and / or the sensor are provided with telecommunication means configured to exchange signals and / or message with the controller. As such, the controller may be able to communicate with the (adjustment) device and / or sensor from a remote location. It is however preferred that the controller is at the same location as the (adjustment) device and / or sensor, viz. that the controller and the (adjustment) device and / or sensor are at most 500 meters away from each other, more preferably at most 250 meters, more preferably at most 100 meters, and most preferably at most 50 meters. Plant cultivation facility The invention also relates to a plant cultivation facility comprising the arrangement of the invention. Preferably, the plant cultivation facility comprises a controlled condition environment that is substantially daylight-free. Preferably, the plant material, the one or more adjustment devices, and / or the one or more sensors as defined herein are kept within said controlled condition environment. Preferably, the controlled condition environment comprises one or more of daylight shielding, heat insulation, and moisture shielding. It will be understood that it is not required that the one or more controllers as defined herein are also present in the plant cultivation facility. The one or more controllers may communicate with the one or more adjustment devices via wires or wirelessly, and therefore may communicate remotely. Use The invention also pertains to the use of artificial light to accelerate the growth of a plant; wherein preferably substantially exclusively artificial grow light is used; wherein preferably said artificial grow light is as defined herein. Preferably, the plant is selected from the group consisting of selected from the group consisting of mangrove, a forest plant, a potato plant, a strawberry plant, a cacao plant, a palm plant, a tomato plant, and an orchid; more preferably the plant is selected from the group consisting of mangrove, a forest plant, a potato plant, and a strawberry plant; and even more preferably from the group consisting of mangrove, an acacia, a potato plant, and a strawberry plant. In some preferred embodiments, in the use the plant is a plant of the genus Rhizophora. In other preferred embodiments, in the use the plant is a plant of the genus Acacia or Vachellia. In other preferred embodiments, in the use the plant is a plant of the species Solanum tuberosum, wherein preferably said plant is a seedling of the species Solanum tuberosum, wherein the seedling is obtained by providing a seed and germinating said seed. In other preferred embodiments, in the use the plant is a plant of the genus Fragaria, wherein preferably said plant is a seedling of the genus Fragaria, wherein the seedling is obtained by providing a seed and germinating said seed. Preferably, the other conditions of the method of the invention are used in the use of artificial grow light to accelerate the growth of a plant, in particular the carbon dioxide concentration of the air, the pH of the substrate, the electric conductivity of the substrate, the relative humidity of the air, and the temperature, in particular the substrate temperature and / or the space temperature. Definitions The term “about” as used herein preferably indicates a deviation of 25% or less from the given value, more preferably 20% or less, more preferably 15% or less, more preferably 10% or less, and most preferably 5% or less. In particular, when referring to the “first about 2 days” or “first about 4 days” and the like when the starting material is a cutting or a tissue culture plant, “about” preferably means a deviation of 25% or less. In particular, when referring to specific values for the air temperature, substrate temperature, pH of the substrate, carbon dioxide concentration of the air, the electric conductivity of the substrate, or the relative humidity of the air, “about” preferably means a deviation of 10% or less, most preferably 5% or less. Herein, “dry weight” refers to the weight of a plant or a part thereof after said plant or part thereof has been dried. Usually, the residual moisture level in said plant or part thereof after drying is at most 10 wt%, preferably at most 5 wt%, as compared to the total weight of the dried plant or dried part. Herein, the “total dry weight” refers to the dry weight of the entire plant (viz. both shoot and root). A “young plant” as referred to herein is a plant that is not mature (yet), but has all the typical parts of a plant, such as a root, a stem, and one or more leaves. Typically, as used herein “young plant” refers to a plant that is of sufficient quality and / or has sufficient weight to be (further) grown outdoors. The skilled person is able to use common general knowledge and / or simple experiments to assess whether a plant has said sufficient quality and / or sufficient weight. The young plants as described herein typically comprise a stem having a leaf pair, preferably multiple leaf pairs. Herein, “a leaf pair” is defined as two leaves on opposite sides of the stem. Herein, “shoot” refers to the part of the plant that is above ground, including the stem, leaves, fruit, and the like. By contrast, “root” refers to the part of the plant that is below ground. Said ratio can be determined by harvesting said plant, drying said plant, separating the shoot from the root, and measuring the dry weight of the shoot and the root, and comparing the dry weights. Alternatively, the shoot and the root are first separated, and then dried separately. As used herein, “leaf area index” refers to the total leaf area present within a certain area divided by the ground surface area of said area. Herein, the “leaf area” is the amount of surface area of leaves of plants (e.g. one plant 2 may have 1000 cm of leaf area divided over 8 leaves). Herein, the “total leaf area” indicates the leaf area of all leaves of a plant combined. There are several ways in which the leaf area of a leaf can be determined, which all yield substantially the same result. For instance, the area of a leaf can be measured manually, for example by using millimeter graph paper, or by other means. For instance, a photograph can be taken of one or more leaves on a contrasting background with a known scale object. Software such as ImageJ can then be used to apply a scale using the known object, locate the contour(s) of the one or more leaves, and measure the leaf area. Furthermore, the leaf area can be determined automatically using handheld or portable leaf area meters that measure leaf area by scanning the surface of the leaf. This is a non- destructive method that the skilled person can readily use, also to measure the total leaf area of a plant. Alternatively, a destructive method can also be employed if desired. In that case, all leaves of a plant may be harvested and dried, and the total weight of the dried leaves may be determined. The total leaf area can then be obtained from multiplying the total dry weight with a certain conversion factor. This conversion factor can be obtained from literature, and / or by measuring the dry weight of a sample of leaves with a known area. An alternative to drying and weighing the leaves is to scan the leaves and analyze their surface area digitally. For determining the total leaf area per plant of a large number of plants, only a small number of plants (e.g. at most 5% of all plants; or about 10 plants) may need to be examined. The average of the results obtained in this way can be considered to be representative for all plants. This is in particular useful when employing the destructive method, as it may not be necessary to harvest the leaves of all plants. Examples The invention is illustrated below using several examples. It will be understood that the invention is not limited thereto, and other embodiments such as those listed above are also capable of achieving the technical effects and benefits of the invention. Unless indicated otherwise, the following conditions were applied for the methods of the invention in the below examples. The plants were kept indoors, in a controlled condition environment that was substantially daylight-free. This controlled condition environment comprised a lighting device (in particular lighting devices comprising one or more light-emitting diodes), an air temperature adjustment device; a substrate temperature adjustment device; a humidity adjustment device; a CO adjustment device; a pH adjustment device; a conductivity 2 adjustment device; an air temperature sensor; a substrate temperature sensor; a humidity sensor; a CO sensor; a pH sensor; and a conductivity sensor. All (adjustment) devices and 2 sensors are as defined herein, and were configured to communicate with one or more controllers. A suitable horticultural substrate was used, and a suitable horticultural nutrient solution was applied when necessary. Optionally, one or more of the side branches were pruned. Moreover, if in the examples reference is made to light having a red component, it is meant that a light source was used producing light with wavelengths in a range of from 600- 700 nm with a peak at 660 nm, wherein the light intensities at 600 and 700 nm are less than 2% of the light intensity at said peak. Likewise, for light having a blue component a light source was used producing light with wavelengths in a range of from 400-500 nm with a peak at 450 nm, wherein the light intensities at 400 and 500 nm are less than 1% of the light intensity at said peak. Finally, for light having a far-red component a light source was used producing light with wavelengths in a range of from 680-800 nm with a peak at 730-740 nm, wherein the light intensity at 680 nm is less than 6% of the light intensity at said peak, and the light intensity at 800 nm is less than 2% of the light intensity at said peak. Unless indicated otherwise, for plants grown from seeds day 0 is the day of sowing. Example 1 – Forestry plant This Example relates to forestry plants, of which Acacia nilotica was chosen as an example. Multiple procedures according to the invention were used to grow young plants of Acacia nilotica. Procedures 2A and 2B start with a cutting or a tissue culture plant of a plant. By contrast, procedures 1A and 1B start with providing a seed of a plant, sowing said seed in a suitable horticultural substrate, and allowing the seed to germinate. The germinating seed was kept indoors under controlled conditions. Germination was carried out using the following conditions. Both the space temperature and the substrate temperature were maintained in a range of from 27 to 33 °C, typically at about 30°C. The relative humidity of the air was maintained in a range of from 85 to 95%, typically at about 90%. The carbon dioxide concentration in the air was maintained in a range of from 300 to 650 ppm, typically at about 420 ppm. The seed was sowed in a pot having a volume in a range of from 65-90 mL, typically 75 mL. No artificial grow light was applied. Germination took about 30 days, after which a seedling was obtained. Unless indicated otherwise, the following conditions were applied for the rest of procedures 1A and 1B, and throughout procedures 2A and 2B. The plants were exposed to artificial grow light for about 12-18 hours a day, typically 14 hours a day, for a total duration of up to 210 days. The CO concentration was kept within 2 the range of from 420-2000 ppm, typically at about 1500 ppm. A suitable horticultural substrate was used, and a suitable horticultural nutrient solution was applied when necessary. The electrical conductivity of the soil in which the plants grew was maintained in a range of 2 2 from 1.2-2.8 mS / cm , typically at about 2.0 mS / cm ; and the pH of said soil was maintained in a range of from 5.2-6.6, typically at about pH 5.9. The temperature of both the soil and the (shoots of the) plant were maintained in a range of from 25-30 °C, typically at about 27 or 29 °C. The relative humidity of the air was maintained in a range of from 75-85%, typically at about 80%. For procedures 1A and 1B, the plants were kept in a pot with a volume in a range of from 65-90 mL, typically 75 mL, for the first about 58-64 days (not including germination). On about day 58-64, the plants were repotted to a pot with a volume in a range of from 500- 1400 mL, typically 700 mL, or to a pot with a volume in a range of from 1500-3000 mL, typically 2000 mL. If the plants were first repotted to a pot with a volume of from 500-1400 mL, the plants were transferred again on about day 101 to a pot with a volume in a range of from 1500-3000 mL, typically 2000 mL. A plant density of about 500-600 (typically 558) 2 plants per m was maintained for the first about 58-64 days (not including germination). If the plants were potted in a pot of a volume of from 500-1400 mL, the plant density was about 2 150-250, typically 204, plants per m . If the plants were potted in a pot of a volume of from 2 1500-3000 mL, the plant density was about 30-80, typically 60, plants per m . After germination, a leaf area index of about 2-4, typically about 3, was maintained. For procedures 2A and 2B, the plants were kept in a pot with a volume in a range of from 65-90 mL, typically 75 mL, for the first about 39-45 days. On about day 39-45, the plants were repotted to a pot with a volume in a range of from 500-1400 mL, typically 700 mL, or to a pot with a volume in a range of from 1500-3000 mL, typically 2000 mL. If the plants were first repotted to a pot with a volume of from 500-1400 mL, the plants were transferred again on about day 61 to a pot with a volume in a range of from 1500-3000 mL, typically 2000 mL. Below, procedures 1A, 1B, 2A, and 2B according to the invention are presented. In each procedure, the growth of a plant is accelerated by exposing said plant substantially exclusively to artificial grow light. In procedures 1A and 2A, the artificial grow light consists essentially of a red component and a blue component, while in procedures 1B and 2B the artificial grow light consists essentially of a red component, a blue component, and a far-red component. Table 1 lists the composition of the artificial grow light used in procedures 1A and 1B. Likewise, Table 2 lists the further conditions used in procedures 2A and 2B. As explained above, procedures 1A and 1B use seeds or seedlings as a starting material, while Procedures 2A and 2B use cuttings or tissue culture plants as a starting material. able 1. Composition of artificial grow light used in procedures 1A and 1B. Parameter Target value Range 2 Blue light (µmol / m / s) 70 60-100 2 Red light (µmol / m / s) 220 200-300 Procedure 1A 0 0-5 ar-red light 2 µmol / m / s) Procedure 1B 30 10-50 able 2. Composition of artificial grow light, temperatures, and relative humidity, used in procedures 2A and 2B. Day 1 Day 2-3 Day 4-7 Day 8 onwards arameter Target Range Target Range Target Range Target Range value value value value Blue light 35 25-45 45 35-55 60 50-70 70 60-100 2 µmol / m / s) Red light 125- 175- 200- 110 95-125 140 190 220 2 µmol / m / s) 155 205 300 2A 0 0-5 0 0-5 0 0-5 0 0-5 ar-red ght 2 µmol / m / s) 2B 15 10-20 20 15-25 25 20-30 30 10-50 pace temperature nd substrate 20 18-22 22 20-24 25 22-27 27 25-29 emperature (ºC) Relative humidity 90 85-95 90 85-95 85 80-90 80 75-85 %) eaf area index 1 0,5-1,5 1 0,5-1,5 1 0,5-1,5 3 2-4 at end of stage) a lant density 558 500- 558 500- 558 500- 558 500- 2 # / m ) 600 600 600 600 a If repotted to a pot of about 700 mL on about day 31, the plant density is typically in a range of from 150-250 2 (on average about 204) plants per m . If repotted to a pot of about 2000 mL on about day 31 (or about day 61 if the plants were first transferred to a pot of about 700 mL on about day 31), the plant density is typically in a 2 range of from 30-80 (on average about 60) plants per m . Below, the results are shown of the Procedures 1A, 2A, 1B, and 2B of the invention. Table 3 summarizes the growth methods and their differences as compared to a reference example. Table 4 shows the plant quality obtained when applying the procedures of the invention for various amounts of time. Table 3. Comparison of the reference procedure and procedures of the invention used to grow young plants of Acacia nilotica, and the time required to obtain a young plant. Reference 1A 1B 2A 2B Exposed to artificial no yes yes yes yes grow light? from with far-red light? no yes no yes sunlight cutting or cutting or Starting material seed seed seed tissue culture tissue culture plant plant Grown indoors or outdoors indoors indoors indoors indoors outdoors? Days required to about about a 125-180 about 100 about 100 a a obtain young plant 120 120 a including time for germination. Table 4. Results from procedures 1A, 1B, 2A, and 2B of the invention when growing young plants of the species Acacia nilotica, and the characteristics of the plants obtained after a certain number of days following the procedure. The number of days for procedures 1A and 1B includes 30 days for germination. Typical ranges are given for certain plant properties, and the typical values are indicated between parentheses. 1A 1B 2A 2B Plant type B C L B C L Number of days 120 160 160 100 140 140 without germination 90 130 130 n / a n / a n / a Total leaf area per 900-1600 1350-2200 1350-2200 900-1600 1350-2200 1350-2200 2 (1750) (1750) (1750) plant (cm ) (1225) (1225) (1750) Total dry weight of 6-11 (8.0) 15-30 (20) 15-30 (20) 6-11 (8.0) 15-30 (20) 15-30 (20) entire plant (g) Ratio of shoot over root 1:0.4 – 1:0.2 1:0.4 – 1:0.2 1:0.4 – 1:0.2 1:0.4 – 1:0.2 1:0.4 – 1:0.2 1:0.4 – 1:0.2 (1:0.3) (1:0.3) (in g dry weight / g dry (1:0.3) (1:0.3) (1:0.3) (1:0.3) weight) Height of plant (cm) 30-60 (45) 50-80 (65) 75-125 30-60 (45) 50-80 (65) 75-125 (100) (100) Average internode 4-9 (6.4) 4-9 (6.4) 6-14 (10) 4-9 (6.4) 4-9 (6.4) 6-14 (10) length (cm) Number of leaf pairs on 6-8 (7) 9-11 (10) 9-11 (10) 6-8 (7) 9-11 (10) 9-11 (10) the main stem Number of side branch 0-1 (0) 2-4 (3) 2-4 (3) 0-1 (0) 2-4 (3) 2-4 (3) pairs Example 2 – Mangrove In this example, young plants of the species Rhizophora mangle were grown from seeds. The conditions of Table 5 shown below were applied for 75 days to obtain a young plant, or for 120 days to obtain a larger young plant. able 5. Conditions to grow young plants of the species Rhizophora mangle using methods of he invention. “Day 51 onwards” indicates the conditions until the end of the procedure ither 75 days or 120 days). Day 0-50 Day 51 onwards arameter Target value Range Target value Range Air temperature (ºC) 28 26-30 28 26-30 ubstrate temperature 28 26-30 28 26-30 ºC) Relative humidity (%) 70 65-80 70 65-80 2 Blue light (µmol / m / s) 70 60-100 70 60-100 2 Red light (µmol / m / s) 220 200-300 220 200-300 2 ar-red light (µmol / m / s) 0 0-5 0 0-5 ight (h / 24h day) 12 10-16 12 10-16 Concentration CO (ppm) 2000 1500-2500 2000 1500-2500 2 ot / plug volume (mL) 200 180-220 2000 1500-2500 lectrical conductivity 2.0 1.2-2.8 2.0 1.2-2.8 2 mS / cm ) pH 6.5 5.8-7.2 6.5 5.8-7.2 2 a a lant density (# / m ) 60 50-70 360 300-400 b b 558 500-600 a a eaf area index (at end of 1.1 0.6-1.5 tage) n / a n / a b b 1.8 1.2-2.1 b fter 75 days. After 120 days. The characteristics of the plants obtained using the procedures of Table 5 for 75 days or for 120 days are shown in Table 6. Table 6. Results from the procedures of Table 5 of the invention when growing young plants of the species Rhizophora mangle, and the characteristics of the plants obtained after a certain number of days following the procedure. Typical ranges are given for certain plant properties, and the typical values are indicated between parentheses. Plant type B C Number of days 75 120 2 Total leaf area per plant (cm ) 100-250 (180) 200-350 (300) Total dry weight of entire plant (g) N.D. 14-21 (17) Ratio of shoot over root 2.5-4.5 (3.5) 2.5-4.5 (3.8) (in g dry weight / g dry weight) Height of plant (cm) 30-50 (40) 40-55 (50) Average internode length (cm) 4-9 (6) 4-9 (6) Number of leaf pairs on the main stem 2-4 (3) 3-5 (4) Number of side branch pairs 0-1 (0) 1-3 (2) Example 3 – Potato plants In this example, young plants of the species Solanum tuberosum were grown from real seeds that were sown in a substrate. The conditions for growing a reference plant in a greenhouse or tunnel are shown in Table 7, and the conditions for growing young plants using methods of the invention are shown in Tables 8 (short procedure for growing young plants) and 9 (longer procedure for growing larger young plants). Table 7. Conditions for growing a reference plant of the species Solanum tuberosum in a greenhouse or tunnel, wherein the plant is not exposed to artificial grow light. It took 42 days to produce a young plant using this procedure. Parameter Target value Range Air temperature (ºC) 30 27-33 Substrate temperature (ºC) 30 27-33 Relative humidity (%) 90 85-95 Concentration CO (ppm) ambient (~420) 350 - 450 2 Pot / plug volume (ml) 30 25 - 35 Nutrition scheme n / a n / a Electrical conductivity n / a n / a 2 (mS / cm ) pH 5.8 5.5 - 6.2 2 Plant density (# / m ) 666 600-700 Leaf area index (at end of 2.5 2.2 - 2.8 stage) Table 8. Conditions for growing a young plant of the species Solanum tuberosum within 21 days using a method according to the invention. Day 0 - 5 Day 6 - 21 Parameter Target value Range Target value Range Air temperature (ºC) 18.5 17 - 20 25 23 - 27 Substrate temperature (ºC) ~ 18.5 ~ 17 - 20 ~ 25 ~ 17 - 20 Relative humidity (%) 90 85 - 95 65 60 - 70 2 Blue light (µmol / m / s) 0 - 50 30 - 70 2 Red light (µmol / m / s) 0 - 200 150 - 250 2 Far-red light (µmol / m / s) 0 - 0 - Light (h / 24h day) 0 - 20 18 - 22 Concentration CO (ppm) ambient (~420) 2000 1000 - 2000 2 Pot / plug volume (ml) 30 25 - 35 30 25 - 35 Electrical conductivity n / a - 2.0 1.8 - 2.0 2 (mS / cm ) pH n.a - 5.8 5.5 - 6.2 2 Plant density (# / m ) 666 600 - 700 666 600 - 700 Leaf area index 0 - 3.7 3 - 4 (at end of stage) e 9. Conditions for growing a large young plant of the species Solanum tuberosum within 34 days using a method according to the invention. Day 0 - 5 Day 6 - 20 Day 21 - 25 Day 26 - 34 rameter Target Range Target Range Target Range Target Range value value value value emperature 18.5 17 - 25 23 - 27 20 18 - 22 23 21 - 25 20 strate ~ 18.5 ~ 17 - ~ 25 ~ 17 - ~ 20 ~ 18 - ~ 23 ~ 21 - perature (ºC) 20 20 22 25 tive humidity 90 85 - 65 60 - 70 65 60 - 70 52 47 - 57 95 e light 0 - 50 30 - 70 90 80 - 90 80 - 2 ol / m / s) 100 100 light 0 - 200 150 - 200 180 - 200 180 - 2 ol / m / s) 250 220 220 red light 0 - 0 - 30 20 - 40 30 20 - 40 2 ol / m / s) ht (h / 24h day) 0 - 20 18 - 22 16 12 - 20 16 12 - 20 centration CO ambient 2000 1000 - 2000 1000 - 2000 1000 - 2 m) (~420) 2000 2000 2000 plug volume 30 25 - 30 25 - 35 6500 6000 - 6500 6000 - 35 7000 7000 ctrical n / a - 2.0 1.8 - 2.0 2.0 1.8 - 2.0 1.8 - ductivity 2.0 2.0 2 / cm ) n.a - 5.8 5.5 - 6.2 5.8 5.5 - 5.8 5.5 - 6.2 6.2 2 Plant density (# / m ) 666 600 - 666 600 - 17 15 - 20 17 15 - 20 700 700 Leaf area index 0 - 3.7 3 - 4 n / a - 0.8 0.6 - (at end of stage) 1.0 The results of the procedures of Tables 7-9 are shown below in Table 10. A plant obtained using the procedure of Table 7 is shown on the left of Figure 3, a plant obtained using the procedure of Table 8 is shown in the middle of Figure 3, and a plant obtained using the procedure of Table 9 is shown on the right of Figure 3. Table 10. Young plants of the species Solanum tuberosum obtained using the procedures of Table 7 (plant A), Table 8 (plant B), or Table 9 (plant C). Typical ranges are given for certain plant properties, and the typical values are indicated between parentheses. Plant type A (reference) B (invention) C (invention) Number of days 42 21 34 2 Total leaf area per plant (cm ) 30-45 (38) 46-65 (55) 350-550 (456) 0.09-0.15 (0.12) 2.0-2.4 (2.19) Total dry weight of entire plant (g) 0.14-0.20 (0.17) Height of plant (cm) 3.5-4.5 (4.0) 4-5 (4.5) 4-5 (4.5) Number of leaf pairs on the main 2-4 (3) 5-7 (6) 7-9 (8) stem Number of side branch pairs 0-1 (0) 0-1 (0) 2-4 (3) Example 4 – Strawberry plants In this example, young plants of the species Fragaria × ananassa (variety Dellizimo) were grown from real seeds that were sown in a substrate. Using a method of the invention, applying the conditions shown in Table 11, young strawberry plants were typically obtained within 40 days (typical range of from 35-45 days). The plants grown using the method of the invention within about 40 days had a height of about 8 cm (typically in a range of from 6-10 cm), and had about 8 leaf pairs on the main stem (typically in a range of from 6-10). e 11. Conditions for growing a young plant of the species Fragaria × ananassa within 40 s using a method according to the invention. Day 0-7 Day 8-14 Day 14-40 ameter Target value Range Target value Range Target value Range e perature d substrate 22 20-24 22 20-24 22 20-24 perature tive 90 / 95 85-100 70-75 65-85 60- 65 55-70 idity (%) light 0 n / a 37 30-50 75 70-80 2 ol / m / s) light 0 n / a 122 100-140 245 230-260 2 ol / m / s) red light 0 n / a 0 0-5 0 0-5 2 ol / m / s) ght (h / 24h 0 n / a 16 15-17 16 15-17 oncentration 2000 1500-2500 2000 1500-2500 2000 1500-2500 (ppm) volume 25 20-30 25 20-30 135 80-250 ) trical uctivity n / a n / a 1.6 1.3-1.9 1.6 1.3-1.9 2 cm ) n / a n / a 5.3 5.0-5.8 5.3 5.0-5.8 t density 937 900-960 937 900-960 162 108-290 2 ) area x (at end 3 2.5 - 4 2.5 2 - 3 3 2.5 - 4 age)

Claims

1. A method for growing a plant under such conditions under which a young plant of better quality is produced obtained and / or a young plant is obtained earlier, compared with a standard outdoor-grown plant, where the method includes the steps by: a) providing plant material selected from the group consisting from a seedling, a cutting, and a tissue culture plant; whereby preference the seedling is obtained by providing a seed and the germination of said seed; and b) exposing said plant material to light, whereby the said light is substantially exclusively artificial grow light.

2. The method according to claim 1, whereby the leaf area index is maintained at a value of at most 4, preferably in a range from 2 to 4, with a stronger preference for around 3.

3. The method according to one of the preceding conclusions, whereby the artificial grow light a red component with a go length in a range comprises from 600 to 700 nm, and where the red component is has a photosynthetic ux density of at least 30 µmol / mZ / s; at preference in a range of 30 to 1000 µmol / m² / s.

4. The method according to one of the preceding conclusions, whereby the artificial grow light a far-red component with a go length in a range from 680 to 800 nm includes, preferably from 680 to 770 nm, and where the far-red component is a photosynthetic has a ux density of at least 1 µmol / m² / s; preferably in a range from 1 to 100 µmol / m² / s.

5. The method according to conclusions 3 and 4, whereby the artificial grow light mentioned red component and mentioned far-red component includes, where the ratio of the photosynthetic ux density of mentioned red component regarding the photosynthetic ux density of the said far-red component lies in a range of 1:1 up to and including 60:

1.

6. The method according to one of the preceding conclusions, whereby the artificial grow light a blue component with a go length in a range from 400 to 500 nm includes, preferably from 420 to 495 nm, and where the blue component has a photosynthetic ux density has a level of at least 10 µmol / m² / s; preferably in a range of 10 to with 250 µmol / mZ / s.

7. The method in accordance with one of the preceding conclusions, whereby The said plant is selected from the group consisting of mangrove, a forest plant, a potato plant, a strawberry plant, a cocoa plant, a palm plant, a tomato plant, an orchid and Paulowm'a tomentosa.

8. The method in accordance with one of the preceding conclusions, whereby the mentioned plant is a plant of the genus Rhizophora.

9. The method according to claim 8, whereby the artificial grow light a red component with a go length in the range of 600 to 700 nm comprises, and where the red component has a photosynthetic ux density has a value of at least 90 µmol / mZ / s; and where the artificial grow light a blue component with a go length in a range of 400 up to and including comprises 500 nm, and where the blue component is a photosynthetic has a ux density of at least 10 µmol / m² / s.

10. The method in accordance with one of conclusions 1 through 7, whereby the said plant is a plant of the genus Acacia or Vachellt'a. 1 1. The method according to claim 10, whereby the artificial grow light a red component with a go length in the range of 600 to 700 nm comprises, and where the red component has a photosynthetic ux density has a value of at least 90 µmol / mZ / s; and where the artificial grow light a blue component with a go length in a range of 400 up to and including comprises 500 nm, and where the blue component is a photosynthetic has a ux density of at least 10 µmol / mZ / s.

12. The method in accordance with one of conclusions 1 through 7, whereby the said plant is a plant of the species Solanum tuberosum.

13. The method according to conclusion 12, where the method the steps includes: all) the providing of a true seed of a plant of the species Solanum tuberosum; a2) the germination of said true seed in order to such a seedling obtain; and b) exposing the said seedling to light, whereby said light is substantial, excluding artificial grow light.

14. The method according to one of conclusions 12 and 13, whereby the artificial grow light a red component with a go length in a range comprises from 600 to 700 nm, and where the red component is has a photosynthetic ux density of at least 150 µmol / m² / s; and where the artificial grow light has a blue component with a includes a length in a range of 400 to 500 nm, and where the blue component has a photosynthetic ux density of at least 30 µmol / mZ / s.

15. The method in accordance with one of conclusions 1 through 7, whereby The said plant is a plant of the genus Fragart'a.

16. The method according to conclusion 15, where the method the steps includes: all) the provision of a seed of a plant of the genus Fragart'a; a2) the germination of said seed in order to produce a seedling obtain; and b) exposing the said seedling to light, whereby said light is substantial, excluding artificial grow light.

17. The method according to one of conclusions 15 and 16, whereby the artificial grow light a red component with a go length in a range comprises from 600 to 700 nm, and where the red component is has a photosynthetic ux density of at least 100 µmol / m² / s; and where the artificial grow light has a blue component with a includes a length in a range of 400 to 500 nm, and where the blue component has a photosynthetic ux density of at least 30 µmol / m² / s.

18. The method according to one of the preceding conclusions, whereby the working method is carried out internally; preferably for at least the first 70 days, preferably at least the first 80 days.

19. The method according to one of the preceding conclusions, whereby the The procedure is carried out for a maximum of 80 days, preferably at most 70 days.

20. The method according to one of the preceding conclusions, whereby the The process is continued at least until the plant bears fruit. 2 1. The method according to one of the preceding conclusions, whereby when the plant has become a young plant, said plant becomes moved to a field outside.

22. The method according to one of conclusions 1 to 20, whereby the working method is carried out indoors at least until said plant bears fruit.

23. The method according to one of the preceding conclusions, whereby said plant material is exposed to light for at least 8 hours per day; preferably for at least 8 hours per day, and with most preference for a duration in the range of 8 to 24 hours per day.

24. The method according to one of the preceding conclusions, whereby said plant material at a temperature in a range of 15 up to and including is kept at 40 °C; preferably in a range of 17 to 35 °C; with greater preference in a range of 18 to 32 °C; with most preferred in a range of 25 to 30 °C.

25. The method according to one of the preceding conclusions, whereby said plant material is exposed to a relative humidity in a range of 60 to 100%; preferably in a range from 65 to 97%; with more preference in a range of 67 to and with 95%; and with most preference in a range of 70 to 85%.

26. The method according to one of the preceding conclusions, whereby said plant material is exposed to air with a CO2- concentration of at least 250 ppm; preferably in a range of 250 to and with 2750 ppm.

27. A plant obtainable by the method according to one of the previous conclusions.

28. A plant within the meaning of claim 27; where said plant a plant of the genus Acacia or Vachellt'a is; where said plant: a) a total leaf area per plant in a range of 900 up to and including 2750 cm2; b) a total dry weight in a range of 6.0 to 30 grams; c) an average internode length in a range of 4 to 14 cm; d) an average leaf area per leaf pair in a range of 150 up to and including 250 cm²; e) a height in the range of 30 to 125 cm; f) a ratio of the dry weight of the shoot over the dry weight of the root in a range of 1:0.4 up to and including 1:0.2 and g) a number of leaf pairs on the main stem in a range of 6 to and with 1 1 has.

29. A plant according to claim 27 ; where said plant a plant of the genus Rhizophora is; where said plant: a) a total leaf area per plant in a range of 50 up to and including 70 cm2; b) a total dry weight in a range of 12 to 21 grams; c) an average internode length in a range of 4 to 9 cm; d) an average leaf area per leaf pair in a range of 50 to and with 70 cm²; e) a height in the range of 30 to 55 cm inclusive; f) a ratio of the dry weight of the shoot over the dry weight of the root in a range of 1:0.4 up to and including 1:0.2 and g) a number of leaf pairs on the main stem in a range of 2 to and with 5 has.

30. A plant within the meaning of claim 27 ; where said plant a plant of the species is Solanum tuberosum; where said plant: a) a total leaf area per plant in a range of 46 up to and including 550 cm2; b) a total dry weight in a range of 0.14 to 2.4 grams; c) a height in the range of 4 to 5 cm; and d) a number of leaf pairs on the main stem in a range of 5 to and with 9 has. 3 1. An apparatus for growing a plant under such conditions under which a young plant of better quality is produced obtained and / or a young plant is obtained earlier, compared with a standard outdoor-grown plant, where the setup includes: a) the plant material as defined in one of claims 1 to and with 26; and b) a lighting adjustment device designed to artificial to provide grow light to the plant material, whereby the artificial grow light is as defined in one of the conclusions 1 up to and including 26; and optionally an air temperature adjustment device configured to the to adjust air temperature; a substrate temperature- adjustment device configured to adjust the substrate temperature; a humidity adjustment device designed to the relative to adjust humidity; a COg adjustment device configured to to adjust the COg concentration of air; a pH adjustment device designed for the pH of the substrate on which the plant material is required to adjust; and / or a conductivity adjustment device designed to the electrical conductivity of the substrate on which it plant material is kept to adapt; and optionally an air temperature sensor configured to the to measure air temperature; a substrate temperature sensor configured to to measure the substrate temperature; a humidity sensor installed to measure the relative humidity; a COg sensor configured to the to measure the CO2 concentration of air; a pH sensor designed to measure the pH of to measure the substrate on which the plant material is kept; and / or a conductivity sensor designed to measure the electrical conductivity of the to measure the substrate on which the plant material is kept; and optionally an air temperature controller designed to the to control air temperature adjustment device; a substrate temperature controller designed to control the substrate temperature. to control an adjustment device; a humidity controller equipped to control the humidity adjustment device; a CO2- controller designed to control the COg adjustment device; a pH- controller designed to control the pH adjustment device; and / or conductivity controller designed to the conductivity- to control adaptation device.

32. A plant breeding facility comprising the establishment according to conclusion 31, whereby the planting facility preferably has a substantially sunlight-free is a conditioned growing environment.

33. Use of artificial light to accelerate the growth of a plant selected from the group consisting of mangrove, a forest plant, a potato plant, a strawberry plant, a cocoa plant, a palm plant, a tomato plant, and an orchid; preferably substantially exclusive artificial grow light is used; whereby preferably mentioned artificial grow light is as defined in one of conclusions 1 to with 26.

34. The use pursuant to claim 33, where the said plant is a plant is of the genus Rhizophora.

35. The use pursuant to claim 33, where the said plant is a plant is of the genus Acacia or Vachellia.

36. The use pursuant to claim 33, where the said plant is a plant is of the species Solanum tuberosum.

37. The use pursuant to claim 36, where the said plant is a seedling of the species Solanum tuberosum is, whereby the seedling is obtained by the providing a seed and the germination of said seed.

38. The use pursuant to claim 33, where the said plant is a plant is of the genus Fragaria.

39. The use pursuant to claim 38, where the said plant is a seedling is of the genus Fragaria, where the seedling is obtained by the providing a seed and the germination of said seed. 1 / 3 FIG. 1

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