Method for planting hydroponic lettuce

Abstract

The invention provides a planting method of hydroponic lettuce, and relates to the technical field of vegetable cultivation. According to the planting method for hydroponic lettuce, after field planting and hydroponic culture are conducted on lettuce seedlings, a combined artificial light source with the red-blue light ratio being (3-7): 1 is adopted for irradiation; the EC value of the nutrient solution after field planting and before harvesting is 0.8-1.5 mS / cm. According to the planting method of the hydroponic lettuce, after the lettuce seedlings are subjected to field planting and hydroponic culture, red and blue light quality regulation and nutrient solution concentration adjustment are added, a hydroponic lettuce growth synergistic system is constructed through the red and blue light quality regulation and nutrient solution concentration adjustment, the growth system is optimized, high-quality growth of the hydroponic lettuce is achieved, synthesis of secondary metabolites is stimulated, and the yield of the hydroponic lettuce is increased. Flavor substances are accumulated, the vitamin content is increased, and the nitrate content is reduced, so that the lettuce quality is improved, the calcium content is increased, the transpiration is enhanced, and the problem of edge burning is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of vegetable cultivation technology, and in particular to a method for growing hydroponically grown lettuce. Background Technology

[0002] Hydroponics is a highly technology-dependent agricultural cultivation method. Currently, hydroponic lettuce production includes steps such as variety selection, seedling raising, transplanting, post-transplanting management, and harvesting. Varieties are generally selected for their strong resistance, vigorous growth, and resistance to bolting. Seedlings can be raised using either substrate or sponge cultivation. Transplanting is done when seedlings have 3-4 true leaves. Existing hydroponic lettuce management has some common problems. First, the flavor and taste of hydroponically grown vegetables may not be as good as those grown in soil. The microorganisms and complex mineral components in the soil help synthesize unique aromatic substances, which are lacking in a purely hydroponic environment, and the rapid growth rate results in lettuce with less nutritional value and flavor. Second, some varieties may be prone to "edge burn" in hydroponics due to high humidity and rapid growth.

[0003] Existing technology CN108849451A discloses a method for improving the quality of hydroponic lettuce. After the lettuce seedlings are transplanted into hydroponics, they are irradiated with an artificial light source with a red-blue light ratio of 1.2-2.2 (excluding 1.6). When 70%-90% of the lettuce reaches the harvest standard, the light intensity is increased by 20%-40%. This method mainly improves the quality of lettuce by increasing the light intensity and reducing the potassium content in the hydroponic nutrient solution. However, it does not solve the "edge burning" problem that easily occurs in hydroponic lettuce, and the overall improvement in lettuce quality is limited. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of current hydroponic lettuce cultivation, such as the "edge burn" problem and poor overall quality. It provides a hydroponic lettuce cultivation method that improves the quality of hydroponic lettuce through the synergistic effect of light quality regulation and nutrient supply, while effectively solving the "edge burn" problem.

[0005] In the first aspect, the present invention specifically protects a method for planting hydroponically grown lettuce, wherein after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (3~7):1; The EC value of the nutrient solution from transplanting to harvest is 0.8~1.5mS / cm.

[0006] According to the hydroponic lettuce planting method protected by the present invention, preferably, after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (3~5):1.

[0007] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, the EC value of the nutrient solution from transplanting to harvest is 1.2~1.5mS / cm.

[0008] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (3~5):1; the EC value of the nutrient solution from transplanting to harvest is 1.2mS / cm.

[0009] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of 3:1; the EC value of the nutrient solution from transplanting to harvest is 1.2 mS / cm.

[0010] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (5~7):1.

[0011] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, the EC value of the nutrient solution is adjusted in stages from transplanting to harvest: within 3 days after transplanting, the EC value of the nutrient solution is 0.8~1.0 mS / cm; during the growth period, the EC value of the nutrient solution is 1.2mS / cm~1.5 mS / cm.

[0012] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, the pH value of the nutrient solution is 6.0 to 6.5.

[0013] According to the hydroponic lettuce planting method protected by the present invention, preferably, the temperature conditions for transplanting the lettuce seedlings into the hydroponic system are: daytime temperature controlled at 20℃~25℃, nighttime temperature controlled at 14℃~18℃, and nutrient solution temperature controlled at 15℃~22℃.

[0014] According to the hydroponic lettuce planting method protected by the present invention, preferably, the humidity conditions for transplanting the lettuce seedlings into the hydroponic system are: the air humidity is controlled at 60% to 80%.

[0015] According to the hydroponic lettuce cultivation method protected by the present invention, preferably, the light conditions for transplanting the lettuce seedlings into the hydroponic system are: irradiation for more than 8 hours using a combination of artificial light sources with a red-blue light ratio of (3~5):1 in a plant factory cultivation environment; And / or, in a greenhouse precision cultivation environment, in addition to daily natural light, add a combination of artificial light sources with a red-blue light ratio of (3~5):1 for more than 3 hours of irradiation.

[0016] According to the hydroponic lettuce planting method protected by the present invention, preferably, the seedlings are transplanted when they have grown to 2-3 true leaves.

[0017] Beneficial effects: This invention provides a method for hydroponic lettuce cultivation. After the lettuce seedlings are transplanted into hydroponics, red and blue light quality regulation and nutrient solution concentration adjustment are added. These two aspects construct a synergistic growth system for hydroponic lettuce, optimize the growth system, achieve high-quality growth of hydroponic lettuce, stimulate the synthesis of secondary metabolites, accumulate flavor substances, increase vitamin content, and reduce nitrate content, thereby improving the quality of lettuce. At the same time, it increases calcium content, enhances transpiration, and effectively solves the "edge burning" problem. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] In a specific embodiment, the present invention provides a method for planting hydroponic lettuce, wherein after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (3~7):1; The EC value of the nutrient solution from transplanting to harvest is 0.8~1.5mS / cm.

[0020] It should be noted that: The nutrient solution concentration (EC value) mentioned in this invention, namely the electrical conductivity value of the nutrient solution, is expressed in mS / cm. It is a core quantitative indicator that characterizes the total concentration of soluble mineral ions in the nutrient solution used for hydroponic lettuce cultivation. Its value directly reflects the intensity of the supply of essential mineral nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium provided by the nutrient solution for lettuce growth, and the ion concentration is positively correlated with the EC value.

[0021] The key to the hydroponic lettuce cultivation method of the present invention lies in the synergistic improvement of two aspects: on the one hand, the irradiation of a specific ratio of red and blue light is increased, and on the other hand, the concentration of nutrient solution is adjusted in a synergistic manner. Under the specific combination of red and blue light, by adjusting the concentration of nutrient solution, the two work together to improve the quality of lettuce and reduce the phenomenon of edge burning. At the same time, the hydroponic lettuce cultivation method provided by the present invention can also effectively reduce the use of nutrient solution, simplify the operation process, and is more conducive to production.

[0022] The synergistic effect of light quality regulation and nutrient supply in this invention breaks through the limitations of existing lettuce cultivation techniques where "light regulation" and "nutrient solution concentration regulation" are independent and simply combined. It integrates red and blue light ratio and nutrient solution concentration into an organic and synergistic regulation system. It precisely regulates the intrinsic coupling relationship between lettuce photosynthetic metabolism and nutrient absorption, so that light parameters and nutrient solution concentration parameters form a complementary and amplifying linkage effect, simultaneously optimizing the photosynthetic efficiency and nutrient accumulation efficiency of lettuce, and ultimately achieving a multi-dimensional improvement in lettuce quality.

[0023] Plants grow through photosynthesis, and different wavelengths of light have significantly different effects on this process. Red light is one of the most efficiently absorbed light qualities by plants, driving the core processes of photosynthesis and directly participating in chlorophyll synthesis and the accumulation of carbohydrates (such as sugars), significantly promoting lettuce leaf growth and nutrient formation. Blue light regulates plant morphology, primarily inhibiting excessive stem elongation and promoting thicker leaves. It also regulates metabolic pathways, such as the synthesis of functional components like vitamins and anthocyanins, enhancing the taste and nutritional value of lettuce. A combination of red and blue light in a specific ratio allows lettuce to maintain a relatively fast growth rate while achieving a compact plant shape and thick leaves. Furthermore, it stimulates the synthesis of secondary metabolites, accumulating flavor compounds (such as sugars) and anthocyanins, increasing vitamin content, and reducing nitrate content, thereby improving lettuce quality.

[0024] Nutrient solution is the sole source of essential elements such as nitrogen, phosphorus, and potassium for hydroponic lettuce. Both excessively high and low concentrations will negatively impact growth. Excessive nutrient solution concentration can cause root stress, leading to yellowing and necrosis of leaf edges, a condition known as "edge burn." Reducing the nutrient solution concentration while ensuring the lettuce receives the necessary nutrients for normal growth not only minimizes root damage but also directly reduces the amount of nutrient solution used, lowering production costs and reducing environmental pollution caused by nutrient residue.

[0025] Light quality and nutrition do not affect plants independently; plant needs change based on environmental changes. When the light environment provides a specific combination of red and blue light, the plant's nutrient requirements change accordingly. For example, an increased proportion of blue light promotes stomatal opening, enhances transpiration, and accelerates the plant's absorption of water and nutrients, thereby altering the plant's nutrient utilization efficiency and allocation strategy. Calcium is transported within plants via transpiration; with enhanced transpiration, calcium can be more effectively transported to the leaf edges where transpiration is weaker, thus effectively preventing leaf edge burn caused by calcium deficiency. Under the new light environment, the plant's nutrient utilization efficiency improves, and the nutrient threshold required for its maximum growth potential decreases, allowing for the same or even better results with lower concentrations. This directly reduces costs and environmental impact. The combined effect of direct regulation and optimization of nutrient supply by red and blue light allows a balance to be achieved between lettuce's "energy acquisition (photosynthesis)" and "material synthesis (nutrient utilization)," ultimately achieving a comprehensive effect of improved quality (e.g., increased sugar and vitamin content, reduced nitrate content), reduced costs (reduced nutrient solution usage), and simplified operation.

[0026] In some specific exemplary embodiments, in order to further optimize the effect of the red and blue light ratio on the growth of lettuce roots and the fresh weight of lettuce above ground, improve the overall quality of hydroponic lettuce, and effectively promote the synthesis of VC and soluble protein in lettuce, the red and blue light ratio of the artificial light source used for irradiation after the lettuce seedlings are transplanted into hydroponics can be further preferred to be (3~5):1, for example 3:1, 4:1 or 5:1.

[0027] In some specific exemplary embodiments, sufficient nutrient supply can significantly enhance the promoting effect of suitable light quality on the accumulation of fresh weight in lettuce above ground. The EC value of the nutrient solution from transplanting to harvest mentioned in this invention can be further preferably 1.2~1.5 mS / cm, for example, it can be point values ​​such as 1.2 mS / cm, 1.3 mS / cm, 1.4 mS / cm, 1.5 mS / cm, or any range of values. A nutrient solution concentration of 1.2~1.5 mS / cm is beneficial to increasing the content of soluble sugars, vitamin C, and soluble proteins, and reducing the nitrate content.

[0028] In some specific embodiments, in order to obtain better hydroponic results, in the hydroponic lettuce planting method mentioned in this invention, after the lettuce seedlings are transplanted into hydroponics, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (3~5):1; the nutrient solution concentration from transplanting to harvest is 1.2mS / cm.

[0029] In some specific embodiments, in order to obtain better chlorophyll synthesis and accumulation effects in hydroponic lettuce leaves, the hydroponic lettuce planting method mentioned in this invention uses a combination of artificial light sources with a red-blue light ratio of 3:1 for irradiation after the lettuce seedlings are transplanted into hydroponics; the EC value of the nutrient solution from transplanting to harvest is 1.2 mS / cm.

[0030] In other specific embodiments, in order to steadily increase the soluble sugar content of hydroponic lettuce, the hydroponic lettuce planting method mentioned in this invention uses a combination of artificial light sources with a red-blue light ratio of (5~7):1 after the lettuce seedlings are transplanted into hydroponics.

[0031] In some specific embodiments, the adjustment of nutrient solution concentration from planting to harvest, as mentioned in this invention, is preferably carried out in stages, specifically: Within 3 days after transplanting, the EC value of the nutrient solution should be 0.8~1.0 mS / cm; during the growing season, the EC value of the nutrient solution should be 0.9 mS / cm~1.5 mS / cm, preferably 1.2 mS / cm~1.5 mS / cm.

[0032] During transplanting, root damage is inevitable, weakening the root system's absorption capacity. If a highly concentrated nutrient solution is applied immediately after transplanting, the osmotic pressure of the solution will be much greater than that of the root cells. Water from the root cells will seep back into the nutrient solution, causing root dehydration. Furthermore, lettuce is not tolerant of excessive fertilizer, and seedlings require low levels of nutrients. A low-concentration nutrient solution can create a mild nutrient environment, ensuring a smooth transition to normal growth after the seedlings have recovered.

[0033] In some specific embodiments, the present invention also optimizes other planting conditions for specific lettuce seedlings to be transplanted into hydroponics, for example: In some specific exemplary embodiments, the temperature conditions for hydroponically transplanting lettuce seedlings mentioned in this invention are controlled as follows: daytime temperature is controlled at 20℃~25℃, nighttime temperature is controlled at 14℃~18℃, and nutrient solution temperature is controlled at 15℃~22℃.

[0034] In some specific exemplary embodiments, the humidity conditions for transplanting lettuce seedlings for hydroponics mentioned in this invention are: air humidity controlled at 60% to 80%.

[0035] In some specific exemplary embodiments, the light conditions for transplanting and hydroponically cultivating lettuce seedlings mentioned in this invention are as follows: irradiation for more than 8 hours using an artificial light source with a red-blue light ratio of (3~5):1 in the cultivation environment of a plant factory; In addition to natural light, artificial light sources with a red-blue light ratio of (3~5):1 are added for more than 3 hours in a greenhouse with precise cultivation.

[0036] In some specific exemplary embodiments, the lettuce seedlings mentioned in this invention are transplanted into hydroponics when the seedlings have grown to 2-3 true leaves.

[0037] In some specific embodiments, the hydroponic lettuce cultivation method of the present invention may further include the following steps: (1) Variety selection We select high-quality, disease-resistant, high-yielding, and bolt-resistant varieties that are registered in the state, and choose pelleted coated seeds.

[0038] (2) Sowing Both substrate seedling cultivation and sponge block seedling cultivation are acceptable.

[0039] For substrate seedling raising, use 72-cell or 105-cell trays. After filling the trays with substrate, press the trays into the cells, placing one seed in each cell. Cover the cells with vermiculite or perlite with a particle size of 1 mm to 2 mm, with a thickness of 5 mm to 7 mm. Maintain the substrate moisture content at 80% to 90% until seedlings emerge.

[0040] Before sowing seeds in sponge blocks, press the sponge blocks into water to fully absorb water. Sow the seeds in the center of the sponge blocks and place them in a flat-bottomed, perforated seedling tray. Place the seedling tray in a hydroponic trough and keep the bottom of the seedling blocks submerged by 3 mm to 5 mm until the seedlings emerge.

[0041] (3) Seedling management Maintain a temperature of 20℃~25℃ before emergence. After emergence and before transplanting, maintain a daytime temperature of 24℃~26℃ and a nighttime temperature of 14℃~18℃, with sufficient sunlight. After the cotyledons unfold, irrigate with nutrient solution, with a pH value between 6.0 and 6.5 and an EC value between 0.8mS / cm and 1.0mS / cm.

[0042] (4) Planting Transplant the seedlings when they have 2-3 true leaves, planting one lettuce seedling in each planting hole. Seedlings grown in substrate are placed directly into the planting hole, while seedlings grown in sponge are placed in planting net cups, which are then inserted into the planting hole to secure the plant.

[0043] (5) Nutrient solution preparation and management Nutrient solution preparation: A general formula can be used for the nutrient solution, such as the Hogland, Japanese Garden, or Yamazaki lettuce formulas. Prepare a 100-fold stock solution according to the nutrient solution formula, and then dilute it to the working solution according to the stock solution ratio. Measure the pH value of the working solution and adjust the pH value of the nutrient solution to 6.0–6.5 using dilute nitric acid or dilute phosphoric acid.

[0044] Nutrient solution management: Monitor and adjust the EC and pH values ​​required by lettuce at different growth stages.

[0045] Within 3 days of transplanting, the EC value should be controlled between 0.8 mS / cm and 1.0 mS / cm. During the growing season, the EC value should be controlled between 1.2 mS / cm and 1.5 mS / cm, and should remain unchanged until harvest.

[0046] The nutrient solution used in the recycling process should be replaced after 2-3 crops in winter and after 1-2 crops in summer.

[0047] (6) Post-planting management Temperature management: Daytime temperature is controlled at 20℃~25℃, nighttime temperature is controlled at 14℃~18℃, and nutrient solution temperature is controlled at 15℃~22℃.

[0048] Humidity management: Air humidity is controlled at 60% to 80%. Humidity is increased by means of wet curtains, spraying, and watering in corridors; humidity is reduced by means of heating and ventilation.

[0049] Light management: In the cultivation environment of the plant factory, the light source is directly replaced with red and blue light (red:blue = 3~5:1), and the daily light time is maintained at more than 8 hours; In a greenhouse environment with precise cultivation, in addition to natural light, additional light sources are provided, such as red and blue light (red:blue = 3~5:1), with more than 3 hours of supplemental lighting per day.

[0050] Pest and disease control: Major insect pests include aphids, thrips, and leaf miners. Physical methods such as yellow and blue sticky traps are preferred for control. Major diseases include downy mildew, brown spot, and stem rot. Agricultural and physical control methods, such as adjusting the cultivation environment, are preferred. Chemical control should be used appropriately when necessary.

[0051] Hydroponic lettuce grown using the hydroponic lettuce cultivation method mentioned in this invention has excellent taste and nutritional value. The high-quality hydroponic lettuce of this invention has at least one of the following characteristics: (a) The soluble sugar content of the hydroponic lettuce is 7.2~7.5 mg / g; (b) The vitamin C content of the hydroponic lettuce is 18~21 mg / 100g; (c) The soluble protein content of the hydroponic lettuce is 2.2~3.1 mg / Kg; (d) The calcium content of the hydroponic lettuce is 400~410mg / Kg.

[0052] Examples 1-9 A method for growing hydroponically grown lettuce involves irradiating lettuce seedlings with a combination of red and blue artificial light sources after transplanting and before harvesting, and adjusting the concentration of the nutrient solution from transplanting to harvest.

[0053] The specific adjustment plan is shown in Table 1.

[0054] Table 1 Serial Number illumination nutrient solution EC value Example 1 Red to blue light ratio 3:1 0.9ms / cm Example 2 Red to blue light ratio 3:1 1.2ms / cm Example 3 Red to blue light ratio 3:1 1.5ms / cm Example 4 Red to blue light ratio 5:1 0.9ms / cm Example 5 Red to blue light = 5:1 1.2ms / cm Example 6 Red to blue light = 5:1 1.5ms / cm Example 7 Red to blue light ratio 7:1 0.9ms / cm Example 8 Red to blue light ratio 7:1 1.2ms / cm Example 9 Red to blue light ratio 7:1 1.5ms / cm Comparative Example 1 A method for growing hydroponically grown lettuce involves irradiating the lettuce seedlings with a combination of red and blue artificial light sources after transplanting them into the hydroponics system. The difference from Example 1 is that the nutrient solution concentration EC value is 0.6 ms / cm.

[0055] Comparative Example 2 A method for growing hydroponically grown lettuce involves irradiating the lettuce seedlings with a combination of red and blue artificial light sources after transplanting them into the hydroponics system. The difference from Example 4 is that the nutrient solution concentration EC value is 0.6 ms / cm.

[0056] Comparative Example 3 A method for growing hydroponically grown lettuce involves irradiating the lettuce seedlings with a combination of red and blue artificial light sources after transplanting them into the hydroponics system. The difference from Example 7 is that the nutrient solution concentration EC value is 0.6 ms / cm.

[0057] Comparative Examples 4-6 A method for hydroponically growing lettuce involves irradiating the lettuce seedlings with white light after transplanting and adjusting the nutrient solution concentration from transplanting to harvest. Specific adjustment procedures are shown in Table 2.

[0058] Table 2 Serial Number illumination Nutrient solution concentration Comparative Example 4 White light 0.9ms / cm Comparative Example 5 White light 1.2ms / cm Comparative Example 6 White light 1.5ms / cm Test case The hydroponic cultivation of lettuce is carried out according to the following detailed steps: after the lettuce seedlings are transplanted into hydroponics, the conditions of Examples 1-9 and Comparative Examples 1-6 are used for transplanting and hydroponics.

[0059] (1) Variety selection We select high-quality, disease-resistant, high-yielding, and bolting-resistant varieties that are nationally registered and have been pelleted and coated.

[0060] (2) Sowing Both substrate seedling cultivation and sponge block seedling cultivation are acceptable.

[0061] For substrate seedling raising, 72-cell trays are used. After filling the trays with substrate, one seed is placed in each cell. The trays are then covered with vermiculite or perlite with a particle size of 1 mm, with a thickness of 6 mm. The substrate moisture content is maintained at 80% until the seedlings emerge.

[0062] (3) Seedling management Maintain a temperature of 25℃ before emergence, and from emergence to transplanting, maintain a daytime temperature of 25℃ and a nighttime temperature of 16℃, with sufficient sunlight. After the cotyledons unfold, irrigate with nutrient solution, with a pH value between 6.0 and 6.5 and an EC value between 0.9 mS / cm.

[0063] (4) Planting Transplant the seedlings when they have 2-3 true leaves, planting one lettuce seedling in each planting hole. Seedlings grown in substrate are placed directly into the planting hole, while seedlings grown in sponge are placed in planting net cups, which are then inserted into the planting hole to secure the plant.

[0064] (5) Nutrient solution preparation and management Nutrient solution preparation: A general formula can be used for the nutrient solution, such as the Hogland, Japanese Garden, or Yamazaki lettuce formulas. Prepare a 100-fold stock solution according to the nutrient solution formula, and then dilute it to the working solution according to the stock solution ratio. Measure the pH value of the working solution and adjust the pH value of the nutrient solution to 6.0–6.5 using dilute nitric acid or dilute phosphoric acid.

[0065] Nutrient solution management: Monitor and adjust the EC and pH values ​​required by lettuce at different growth stages.

[0066] Within 3 days of transplanting, the EC value was controlled between 0.9 mS / cm. During the growing season, the EC value remained unchanged as in the examples and comparative examples until harvest.

[0067] The nutrient solution used in the recycling process should be replaced after 2-3 crops in winter and after 1-2 crops in summer.

[0068] (6) Post-planting management Temperature management: Daytime temperature is controlled at 20℃~25℃, nighttime temperature is controlled at 14℃~18℃, and nutrient solution temperature is controlled at 15℃~22℃.

[0069] Humidity management: Air humidity is controlled at 60% to 80%. Humidity is increased by means of wet curtains, spraying, and watering in corridors; humidity is reduced by means of heating and ventilation.

[0070] In the cultivation environment of the plant factory, light management is based on the examples and comparative examples, with the daily light duration maintained at more than 8 hours.

[0071] Pest and disease control: Major insect pests include aphids, thrips, and leaf miners. Physical methods such as yellow and blue sticky traps are preferred for control. Major diseases include downy mildew, brown spot, and stem rot. Agricultural and physical control methods, such as adjusting the cultivation environment, are preferred. Chemical control should be used appropriately when necessary.

[0072] The specific results are as follows: Four sets of repeated experiments were set up under the experimental conditions of each embodiment and comparative example. Five lettuce plants were randomly selected from each set as test samples, and the average value was taken as the final test result under the experimental conditions.

[0073] (1) Effects of different treatments on lettuce growth phenotype Different light qualities and different nutrient synergistic treatments have different effects on the phenotypic growth of lettuce, as detailed in Table 3.

[0074] Table 3. Phenotypic differences in lettuce under different treatments Plant height / cm Number of leaves SPAD value Example 1 B2 17.5 21.5 21.85 Example 2 B3 17.725 23.5 22.9 Example 3 B4 18.25 23.25 22.625 Example 4 C2 17.675 21.25 21.55 Example 5 C3 18.175 23.25 22.875 Example 6 C4 18.175 23.25 22.675 Example 7 D2 17.725 21.25 21.375 Example 8 D3 18.275 22.25 21.4 Example 9 D4 18.3 22.25 21.925 Comparative Example 1 B1 17.05 21 21.55 Comparative Example 2 C1 17.275 20.75 21.35 Comparative Example 3 D1 17.3 20.5 20.85 Comparative Example 4 A2 18.175 21 19.525 Comparative Example 5 A3 18.35 21.75 19.925 Comparative Example 6 A4 18.475 21.75 20.05 The data in Table 3 are the mean values ​​of all tested samples.

[0075] SPAD value is the relative chlorophyll content. SPAD value is an indicator that characterizes the relative chlorophyll content of plant leaves. It is calculated by comparing the difference in absorption and transmission of 650nm red light and 940nm infrared light by the leaves. The higher the value, the higher the chlorophyll content and the greener the leaves. It is measured by an instrument (model: Top Cloud Agriculture TYS-B handheld portable chlorophyll meter). As shown in Table 3, under the same light quality, the average height of lettuce plants gradually increased, and the height growth in the red-blue light = 5:1 treatment tended to stabilize after the concentration reached 1.2 ms / cm. The effect of nutrient solution concentration on plant height varied under different light quality treatments. In the white light treatment, the plant height increased by 6.03% when the nutrient solution concentration increased from 0.6 ms / cm to 1.5 ms / cm; while in the red-blue light = 3:1 treatment, the plant height increase within the same concentration range was 7.04%. There is an interaction between light quality and nutrient solution concentration; the lettuce plant height in the red-blue light = 3:1 treatment was more sensitive to changes in nutrient solution concentration.

[0076] At the same nutrient solution concentration, the red-blue light ratio of 3:1 treatment was generally more effective than white light and other red-blue light ratios in increasing the number of lettuce leaves. Under the same light quality, the increase in leaf number at different nutrient solution concentrations showed a trend of first increasing and then stabilizing, with the increase tending to plateau after the concentration exceeded 1.2 ms / cm. In the nutrient solution concentration range of 0.6~0.9 ms / cm, the difference in leaf number among different light quality treatments was small; when the nutrient solution concentration was increased to 1.2 ms / cm, the increase in leaf number in the red-blue light ratios of 3:1 and 5:1 was much higher than that in the white light and 7:1 treatments. The coupling effect of high-concentration (1.2 ms / cm) nutrient solution and suitable red-blue light ratios (3:1, 5:1) was more conducive to the differentiation and growth of lettuce leaves.

[0077] When the nutrient solution concentration was 0.6 ms / cm and 1.5 ms / cm, the average SPAD value was highest in the red-blue light = 5:1 treatment and lowest in the white light treatment, with differences of 1.925 and 2.625, respectively. When the nutrient solution concentration was 0.9 ms / cm and 1.2 ms / cm, the average SPAD value was highest in the red-blue light = 3:1 treatment and lowest in the white light treatment, with differences of 2.325 and 2.975, respectively. The SPAD value of lettuce leaves treated with red-blue light ratios was significantly higher than that treated with white light, with the improvement effect being particularly prominent in the red-blue light = 3:1 and red-blue light = 5:1 treatments. In the white light and red-blue light = 7:1 treatments, the average SPAD value of leaves gradually increased with the increase of nutrient solution concentration. When the concentration increased from 0.6 ms / cm to 1.5 ms / cm, the SPAD increase was 3.22% and 5.16%, respectively. In the red-blue light = 3:1 treatment, the average SPAD value of leaves first increased and then decreased with the increase of nutrient solution concentration. It reached a peak at 1.2 ms / cm and continued to increase until it slightly decreased at 1.5 ms / cm. In the red-blue light = 5:1 treatment, the average SPAD value of leaves first increased and then stabilized with the increase of nutrient solution concentration. After the concentration reached 1.2 ms / cm, it remained in the range of 22.7~22.9. There is a significant interaction between light quality and nutrient solution concentration on the SPAD value of lettuce leaves. Under low nutrient solution concentrations (0.6–0.9 ms / cm), the difference in SPAD values ​​between different light quality treatments is relatively small. When the nutrient solution concentration is increased to 1.2–1.5 ms / cm, the increases in SPAD values ​​for red-blue light ratios of 3:1 and 5:1 are much greater than those for white light and red-blue light ratios of 7:1. This indicates that the coupling effect of high nutrient solution concentrations (1.2–1.5 ms / cm) and suitable red-blue light ratios (3:1, 5:1) can significantly promote the synthesis and accumulation of chlorophyll in lettuce leaves.

[0078] (2) Effects of different treatments on biomass accumulation in lettuce Different light qualities and different nutrient synergistic treatments have different effects on lettuce biomass accumulation, as shown in Table 4.

[0079] Table 4. Differences in biomass accumulation in lettuce under different treatments Serial Number Fresh weight on the ground (g) Fresh weight underground (g) Dry weight on the ground (g) Dry weight of underground soil (g) Example 1 B2 78.77 6.96 2.95 0.45 Example 2 B3 90.83 7.22 3.41 0.52 Example 3 B4 89.25 7.20 3.43 0.50 Example 4 C2 77.01 6.62 2.97 0.44 Example 5 C3 87.87 7.21 3.38 0.50 Example 6 C4 89.48 7.09 3.39 0.50 Example 7 D2 71.37 6.09 2.74 0.42 Example 8 D3 85.29 6.59 3.13 0.45 Example 9 D4 86.35 6.76 3.16 0.46 Comparative Example 1 B1 71.23 6.14 2.91 0.41 Comparative Example 2 C1 71.51 6.14 2.79 0.41 Comparative Example 3 D1 67.74 5.92 2.71 0.40 Comparative Example 4 A2 69.88 5.89 2.74 0.42 Comparative Example 5 A3 84.03 6.03 3.07 0.42 Comparative Example 6 A4 85.63 6.19 3.16 0.44 Under the same nutrient solution concentration, the average above-ground fresh weight of lettuce treated with a red-blue light ratio was significantly higher than that treated with white light, and the regulatory effects of different red-blue light ratios varied. The light quality regulation effect was most significant at a nutrient solution concentration of 1.2 ms / cm. Comparing different red-blue light ratios, it can be seen that the average above-ground fresh weight of lettuce treated with a red-blue light ratio of 3:1 (Group B) was at a relatively high level at all nutrient solution concentrations, followed by the red-blue light ratio of 5:1 (Group C). The difference between the red-blue light ratio of 7:1 (Group D) and the other two gradually widened with increasing nutrient solution concentration, indicating that an excessively high proportion of red light would weaken the promoting effect of the red-blue light ratio on the above-ground fresh weight of lettuce.

[0080] Under the same light quality ratio, the above-ground fresh weight of lettuce showed a trend of first significantly increasing and then stabilizing with the increase of nutrient solution concentration. 1.2~1.5 ms / cm can significantly promote the accumulation of above-ground fresh weight of lettuce.

[0081] There was a significant interaction between the light quality ratio and nutrient solution concentration on the above-ground fresh weight of lettuce. At low nutrient solution concentrations (0.6, 0.9 ms / cm), the difference in above-ground fresh weight among different light quality treatments was relatively small; at high nutrient solution concentrations (1.2, 1.5 ms / cm), the difference in above-ground fresh weight among different light quality treatments significantly increased. Furthermore, the advantage of red-blue light = 3:1 (Group B) was much greater at high concentrations than at low concentrations, indicating that sufficient nutrient supply can significantly enhance the promoting effect of suitable light quality on the accumulation of above-ground fresh weight in lettuce. The B3 treatment (red-blue light = 3:1 + nutrient solution concentration 1.2 ms / cm) had the highest mean above-ground fresh weight, reaching 90.83 g; followed by the C4 treatment (red-blue light = 5:1 + nutrient solution concentration 1.5 ms / cm), with a mean of 89.48 g.

[0082] Under the same nutrient solution concentration, the mean underground fresh weight of lettuce treated with a red-blue light ratio was significantly higher than that treated with white light (Group A), and the regulatory effects of different red-blue light ratios varied. The mean underground fresh weights of red-blue light = 3:1 (Group B) and red-blue light = 5:1 (Group C) were similar at various nutrient solution concentrations and were both at relatively high levels. The underground fresh weight of red-blue light = 7:1 (Group D) was significantly lower than the former two, indicating that an excessively high proportion of red light weakens the promoting effect of the red-blue light ratio on lettuce root growth. Under the same light quality ratio, the underground fresh weight of lettuce showed a trend of first significantly increasing and then stabilizing with increasing nutrient solution concentration.

[0083] At low nutrient solution concentrations (0.6, 0.9 ms / cm), the difference in underground fresh weight among different light quality treatments was relatively small; at high nutrient solution concentrations (1.2, 1.5 ms / cm), the difference in underground fresh weight among different light quality treatments significantly increased, indicating that sufficient nutrient supply can significantly enhance the promoting effect of suitable light quality on lettuce root growth. The B3 treatment (red-blue light = 3:1 + nutrient solution concentration 1.2 ms / cm) had the highest average underground fresh weight of 7.22 g, followed by the C3 treatment (red-blue light = 5:1 + nutrient solution concentration 1.2 ms / cm), with an average of 7.21 g. Both were the optimal treatment combinations for promoting lettuce root growth.

[0084] Under the same nutrient solution concentration, the mean above-ground dry weight of lettuce treated with a red-blue light ratio was significantly higher than that treated with white light (Group A), and the regulatory effects of different red-blue light ratios varied significantly. The red-blue light ratio of 3:1 (Group B) resulted in the highest mean above-ground dry weight at all nutrient solution concentrations, followed by red-blue light ratio of 5:1 (Group C). The difference between red-blue light ratio of 7:1 (Group D) and the other two gradually widened with increasing nutrient solution concentration, indicating that an excessively high proportion of red light weakens the promoting effect of the red-blue light ratio on lettuce dry matter accumulation. Under the same light quality ratio, the above-ground dry weight of lettuce showed a trend of first significantly increasing and then stabilizing with increasing nutrient solution concentration. There was a significant interaction between the light quality ratio and nutrient solution concentration on the above-ground dry weight of lettuce. At low nutrient solution concentrations (0.6, 0.9 ms / cm), the difference in aboveground dry weight among different light quality treatments was relatively small. At high nutrient solution concentrations (1.2, 1.5 ms / cm), the difference in aboveground dry weight among different light quality treatments significantly increased. Furthermore, the red-blue light ratio of 3:1 (Group B) and 5:1 (Group C) showed a much greater advantage at high concentrations than at low concentrations, indicating that sufficient nutrient supply can significantly enhance the promoting effect of appropriate light quality on lettuce dry matter accumulation. The B4 treatment (red-blue light = 3:1 + nutrient solution concentration 1.5 ms / cm) had the highest mean aboveground dry weight of 3.43 g, followed by the B3 treatment (red-blue light = 3:1 + nutrient solution concentration 1.2 ms / cm) with a mean of 3.41 g; there was no significant difference between the two treatments.

[0085] Under the same nutrient solution concentration, the mean underground dry weight of lettuce treated with a red-blue light ratio was significantly higher than that treated with white light (Group A), and the regulatory effects of different red-blue light ratios varied. The mean underground dry weights of red-blue light = 3:1 (Group B) and red-blue light = 5:1 (Group C) were similar at various nutrient solution concentrations and were both at relatively high levels. The underground dry weight of red-blue light = 7:1 (Group D) was significantly lower than the former two, indicating that an excessively high proportion of red light weakens the promoting effect of the red-blue light ratio on the accumulation of dry matter in lettuce roots. Under the same light quality ratio, the underground dry weight of lettuce showed a trend of first significantly increasing and then stabilizing with increasing nutrient solution concentration. There was a significant interaction between the light quality ratio and the nutrient solution concentration on the underground dry weight of lettuce. At low nutrient solution concentrations (0.6, 0.9 ms / cm), the difference in underground dry weight among different light quality treatments was relatively small, while at high nutrient solution concentrations (1.2, 1.5 ms / cm), the difference in underground dry weight among different light quality treatments significantly increased. Furthermore, the advantages of red-blue light ratios of 3:1 (Group B) and 5:1 (Group C) at high concentrations were significantly greater than those at low concentrations, indicating that sufficient nutrient supply can significantly enhance the promoting effect of suitable light quality on the accumulation of dry matter in lettuce roots. The B3 treatment (red-blue light = 3:1 + nutrient solution concentration 1.2 ms / cm) had the highest mean underground dry weight of lettuce, followed by the C3 and C4 treatments.

[0086] (3) Effects of different treatments on lettuce quality Soluble sugars are an important indicator for measuring the taste and nutritional quality of lettuce.

[0087] The method for detecting soluble sugar content is as follows: Anthrone colorimetric method: Ingredients: Fresh lettuce leaves Reagents: Anthrone reagent: Weigh 0.2g of anthrone, dissolve in 100mL of concentrated sulfuric acid, and prepare for use on the same day. Glucose standard solution: Accurately weigh 100mg of glucose, dissolve in distilled water and dilute to 100mL to obtain a 1mg / mL glucose standard solution.

[0088] Instruments and equipment: spectrophotometer, constant temperature water bath, centrifuge, mortar and pestle, volumetric flask, pipette, colorimetric tubes, etc.

[0089] Experimental steps: Plotting the standard curve: Take seven clean colorimetric tubes and add 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mL of glucose standard solution, respectively. Then, bring the volume to 1.0 mL with distilled water to achieve glucose concentrations of 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mg / mL. Add 4.0 mL of anthrone reagent to each tube, shake quickly, and immediately place the tubes in a boiling water bath for 10 minutes. After heating, remove and cool to room temperature. Using a blank tube (0 mg / mL glucose solution) as a control, measure the absorbance of each solution at 620 nm using a spectrophotometer. Plot a standard curve with glucose concentration on the x-axis and absorbance on the y-axis.

[0090] Sample preparation: Weigh 5g of fresh lettuce leaves, wash and dry them, then chop them finely. Place them in a mortar, add 10mL of distilled water, and grind into a homogenate. Transfer the homogenate to a centrifuge tube and centrifuge at 4000r / min for 10 minutes. Collect the supernatant. Transfer the supernatant to a 50mL volumetric flask, dilute to the mark with distilled water, and mix well to obtain the sample solution to be tested.

[0091] Sample determination: Take 1.0 mL of the sample solution to be tested into a clean colorimetric tube, add 4.0 mL of anthrone reagent, shake well, and perform color development and cooling according to the steps in the standard curve plotting. Using a blank tube as a control, measure the absorbance of the sample solution at a wavelength of 620 nm.

[0092] Result calculation: Based on the absorbance of the sample solution, the corresponding glucose concentration is found on the standard curve. The soluble sugar content in tomatoes is calculated using the following formula: Soluble sugar content (mg / g) = (C×V) / W, where C is the glucose concentration (mg / mL) found on the standard curve, V is the total volume of the sample extract (mL), and W is the sample mass (g).

[0093] Precautions: When anthrone reagent is mixed with concentrated sulfuric acid, a large amount of heat will be generated. Handle with care to prevent splashing and injury. The colorimetric reaction should be carried out under acidic conditions, and the reaction time and temperature must be strictly controlled to ensure the accuracy of the results. During sample extraction, ensure complete extraction as much as possible. The supernatant after centrifugation should be clear; turbidity may affect the measurement results.

[0094] Vitamin C is the core antioxidant nutrient in lettuce.

[0095] The method for detecting vitamin C content is as follows: GB5009.86-2016 National Food Safety Standard, Determination of Ascorbic Acid in Food, Method III: 2,6-Dichlorophenolindophenol Titration Method Soluble protein reflects the protein nutritional level of lettuce, and its content is synergistically regulated by light quality and nutrient solution concentration.

[0096] The method for detecting soluble protein content is as follows: Coomassie Brilliant Blue Ingredients: Fresh lettuce.

[0097] Reagents: Coomassie Brilliant Blue G-250 dye reagent, standard protein solution (such as bovine serum albumin, BSA), distilled water, mortar and pestle, centrifuge, centrifuge tubes, pipettes, spectrophotometer, cuvettes, etc.

[0098] Experimental steps: Plotting the standard curve: Take six clean test tubes and add 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of standard protein solution, respectively. Make up the volume with distilled water to 1 mL, resulting in protein concentrations of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mg / mL. Add 5 mL of Coomassie Brilliant Blue G-250 dye reagent to each test tube, shake well, and incubate at room temperature for 5-15 minutes. Using a blank tube (0 mg / mL protein solution) as a control, measure the absorbance of each solution at 595 nm using a spectrophotometer. Plot a standard curve with protein concentration on the x-axis and absorbance on the y-axis.

[0099] Sample preparation: Weigh 5g of fresh lettuce leaves, wash and dry them, then chop them and place them in a mortar. Add 10mL of distilled water and grind them into a homogenate. Transfer the homogenate to a centrifuge tube and centrifuge at 4000-5000r / min for 10-15 minutes. Take the supernatant as the sample solution to be tested.

[0100] Sample determination: Take 1 mL of the sample solution to be tested and place it in a clean test tube. Add 5 mL of Coomassie Brilliant Blue G-250 dye reagent, shake well, and let stand at room temperature for 5-15 minutes. Using a blank tube as a control, measure the absorbance of the sample solution at a wavelength of 595 nm.

[0101] Result calculation: Based on the absorbance of the sample solution, the corresponding protein concentration is found on the standard curve. The soluble protein content in lettuce is calculated using the following formula: Soluble protein content (mg / g) = (C×V) / W, where C is the protein concentration (mg / mL) found on the standard curve, V is the total volume of the extract (mL), and W is the sample mass (g).

[0102] Precautions: Coomassie Brilliant Blue G-250 dye reagent should be prepared fresh for each use to avoid reagent deterioration due to prolonged storage. When measuring absorbance, ensure that the cuvette has good light transmittance, and calibrate with distilled water or blank solution before each measurement.

[0103] Nitrate content is an important indicator for evaluating the safety and quality of lettuce; excessive nitrate content can pose potential health risks.

[0104] The method for detecting nitrate content is as follows: GB5009.33-2016 National Food Safety Standard - Determination of Nitrites and Nitrates in Food - Method III - Determination of Nitrates in Vegetables and Fruits - Ultraviolet Spectrophotometry The method for detecting the calcium content in lettuce leaves is as follows: GB5009.92-2016 National Safety Standard for Determination of Calcium in Food - Method III: Inductively Coupled Plasma Atomic Emission Spectrometry The test results are shown in Table 5.

[0105] Table 5. Differences in quality indicators of lettuce under different treatments Serial Number Soluble sugars (mg / g) Vitamin C (mg / 100g) Soluble protein (mg / kg) Nitrate (mg / kg) Calcium (mg / kg) Example 1 B2 5.14 18.49 2.38 1833.62 407.7475 Example 2 B3 6.18 20.49 2.62 2195.90 409.7475 Example 3 B4 7.29 20.49 3.10 2372.24 408.1025 Example 4 C2 7.41 17.95 2.36 2078.36 405.275 Example 5 C3 7.33 18.95 2.49 2265.87 405.9675 Example 6 C4 7.38 20.01 2.87 2372.49 402.3975 Example 7 D2 7.44 16.97 2.35 2071.18 395.2525 Example 8 D3 7.50 17.97 2.49 2248.33 396.1375 Example 9 D4 7.39 17.47 2.78 2377.95 395.6575 Comparative Example 1 B1 5.04 18.46 2.29 1646.32 397.27 Comparative Example 2 C1 7.36 17.95 1.99 1882.45 394.77 Comparative Example 3 D1 7.43 16.95 1.93 1963.58 384.8825 Comparative Example 4 A2 5.12 17.93 2.36 2182.29 398.4725 Comparative Example 5 A3 6.19 19.53 2.49 2385.87 389.0725 Comparative Example 6 A4 5.37 20.03 2.87 2521.56 387.7025 As shown in Table 5, light quality has a significant dominant effect on soluble sugar content: the soluble sugar content of groups C and D (red light = 5:1 and 7:1, respectively) is higher than that of groups A and B.

[0106] Table 5 shows that group B (red-blue light = 3:1) had the best overall vitamin C content; group A had the lowest mean vitamin C content at 18.87 mg / 100g. At lower nutrient solution concentrations (0.6 ms / cm, 0.9 ms / cm), the vitamin C content of groups A (white light) and B (red-blue light = 3:1) was generally higher than that of groups C and D (high proportion of red light). At higher nutrient solution concentrations (1.2 ms / cm, 1.5 ms / cm), treatments B and C showed better vitamin C content. Group D (red-blue light 7:1) had the lowest relative vitamin C content among all treatments. The effect of nutrient solution concentration on vitamin C content showed a "first increase, then stability" pattern: In groups A, B, and C, the vitamin C content reached its peak when the nutrient solution concentration increased to 1.2~1.5 mS / cm; while the vitamin C content in group D (red to blue light = 7:1) was generally low, with an average of only 17.34 mg / 100g, and there was no significant upward trend with changes in nutrient solution concentration, indicating that an excessively high proportion of red light may inhibit vitamin C synthesis in lettuce.

[0107] Under all light quality treatments, the soluble protein content showed a steady and continuous increase with increasing nutrient solution concentration. This clearly reflects the direct promoting effect of increased nitrogen (and other nutrients) supply on plant protein synthesis. The soluble protein content of groups B and C was generally higher than that of groups A and D, with treatment B4 (3.10 mg / kg) having the highest value among all treatments; group A had the lowest average soluble protein content, at only 2.42 mg / kg. Under the same light quality, the soluble protein content showed a significant increasing trend with increasing nutrient solution concentration: the soluble protein content of treatments B1 to B4 increased from 2.29 mg / kg to 3.10 mg / kg, an increase of 35.4%, and treatment C4 (2.87 mg / kg) was 44.2% higher than treatment C1 (1.99 mg / kg), indicating that a suitable red-blue light ratio combined with a higher nutrient solution concentration can effectively promote protein synthesis in lettuce.

[0108] Table 5 shows that the nitrate content in all treatment groups increased linearly with increasing nutrient solution concentration. Light quality had a significant regulatory effect on nitrate content. The overall nitrate content in group B was lower than that in groups A, C, and D, with treatment B1 showing the lowest value among all treatments. Group A showed the largest increase in nitrate content. At high nutrient solution concentrations (1.5 ms / cm), there was no significant difference in nitrate content among treatments B4, C4, and D4, indicating that the regulatory effect of light quality on nitrate accumulation was weakened under high nutrient solution concentrations. At the same nutrient solution concentration, the nitrate content was generally highest under white light (group A). ​​Treatments supplemented with blue light (groups B, C, and D) effectively reduced nitrate accumulation, with the red-blue light ratio of 3:1 (group B) showing a particularly significant nitrate-reducing effect at low and medium concentrations. Blue light promoted the assimilation and reduction of nitrate by activating nitrate reductase activity.

[0109] A red-to-blue light ratio of 3:1 to 5:1 (Group B) can significantly increase the content of vitamin C and soluble protein; Red light to blue light ratio of 5:1 to 7:1 (Groups C and D) can steadily increase the soluble sugar content; white light (Group A) treatment results in the lowest overall nutritional quality of lettuce.

[0110] Nutrient solution concentration is positively correlated with lettuce quality indicators: a nutrient solution concentration of 1.2~1.5 ms / cm is beneficial to increase the content of soluble sugar, vitamin C and soluble protein, and reduce the nitrate content.

[0111] The overall mean calcium content of lettuce leaves treated with different nutrient solution concentrations was as follows: Red-Blue Light = 3:1 (B, 405.72 mg / kg) > Red-Blue Light = 5:1 (C, 402.10 mg / kg) > Red-Blue Light = 7:1 (D, 392.98 mg / kg) > White Light (A, 390.99 mg / kg). The calcium content of lettuce leaves showed a typical trend of first increasing and then decreasing with the gradient increase of nutrient solution concentration: within the range of 0.6–1.2 ms / cm, increasing the nutrient solution concentration increased the effective concentration of calcium ions that the roots could absorb, meeting the calcium requirements for lettuce growth, and the calcium content continued to rise; when the nutrient solution concentration exceeded 1.2 ms / cm and increased to 1.5 ms / cm, the calcium content slightly decreased. This is because high-concentration nutrient solution increases the osmotic pressure of the rhizosphere environment, inhibiting the lettuce roots' active water and fertilizer absorption capacity, and reducing the efficiency of calcium ion transport to the leaves. Therefore, it was determined that 0.9~1.2 ms / cm is the suitable nutrient solution concentration range for calcium accumulation in lettuce leaves.

[0112] There is a highly significant synergistic coupling effect between light quality and nutrient solution concentration. Under different light quality conditions, the response of lettuce leaf calcium content to changes in nutrient solution concentration varies significantly. White light treatment group (A): The calcium content of lettuce leaves showed an increasing-decreasing-decreasing trend with increasing nutrient solution concentration, reaching a peak at 0.9 ms / cm (A2). When the concentration continued to increase to 1.2 and 1.5 ms / cm, the calcium content continued to decrease, indicating that lettuce under white light environment has poor adaptability to high concentration nutrient solution, and high concentration nutrient solution will significantly inhibit its calcium absorption and accumulation. Under the red-blue light ratio of 3:1, the group with the best calcium content among all light quality treatments showed a continuous increasing trend in calcium content in lettuce leaves with increasing nutrient solution concentration, reaching the highest value of 409.75 mg / kg in the entire experiment at 1.2 ms / cm (B3). Even when the nutrient solution concentration was increased to 1.5 ms / cm (B4), the calcium content only slightly decreased to 408.10 mg / kg, still maintaining an extremely high level. It can be seen that the red-blue light ratio of 3:1 can significantly enhance the tolerance of lettuce to high-concentration nutrient solution, and the synergistic effect of the two can maximize the accumulation of calcium in lettuce leaves. Under a red-blue light ratio of 5:1, the calcium content in lettuce leaves reached its peak at 1.2 ms / cm (C3) (405.97 mg / kg), slightly lower than the same concentration treatment with a red-blue light ratio of 3:1. Calcium content decreased slowly after the concentration exceeded 1.2 ms / cm, but the calcium content at 1.5 ms / cm (C4) was still higher than that under white light and the same concentration treatment with a red-blue light ratio of 7:1, indicating better overall calcium accumulation than the white light and red-blue light ratio of 7:1 treatments. In the red-blue light ratio of 7:1 treatment group (D), the calcium content in lettuce leaves showed a continuous and slow increasing trend with increasing nutrient solution concentration, reaching its peak at 1.2 ms / cm (D3) (396.14 mg / kg), and slightly decreasing at 1.5 ms / cm. The calcium content at all concentrations in this group was significantly lower than that in the red-blue light ratio of 3:1 and 5:1 treatment groups, further verifying that an excessively high proportion of red light in the red-blue light ratio reduces the promoting effect of light quality on calcium absorption in lettuce. Based on the combined values ​​and variation patterns of calcium content in lettuce leaves across the various treatment groups, under the conditions of this experiment: the optimal synergistic combination was red-blue light = 3:1 + nutrient solution concentration of 1.2 ms / cm, resulting in a calcium content of 409.75 mg / kg in lettuce leaves; red-blue light = 3:1 + 1.5 ms / cm (B4, 408.10 mg / kg); the second-best combinations were red-blue light = 3:1 + 0.9 ms / cm (B2, 407.75 mg / kg) and red-blue light = 5:1 + 1.2 ms / cm (C3, 405.97 mg / kg).

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for cultivating hydroponically grown lettuce, characterized in that, After the lettuce seedlings were transplanted and hydroponically cultured, they were irradiated with a combination of artificial light sources with a red-blue light ratio of (3~7):

1. The EC value of the nutrient solution for hydroponics from transplanting to harvest is 0.8~1.5mS / cm.

2. The method for cultivating hydroponically grown lettuce according to claim 1, characterized in that, After the lettuce seedlings were transplanted and hydroponically cultured, they were irradiated with an artificial light source with a red-blue light ratio of (3~5):

1.

3. The method for cultivating hydroponically grown lettuce according to claim 2, characterized in that, The EC value of the nutrient solution from planting to harvest is 1.2~1.5 mS / cm.

4. The method for cultivating hydroponically grown lettuce according to claim 1, characterized in that, After the lettuce seedlings are transplanted and hydroponically cultured, they are irradiated with a combination of artificial light sources with a red-blue light ratio of (5~7):

1.

5. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 4, characterized in that, From transplanting to harvest, the EC value of the nutrient solution should be adjusted in stages: within 3 days after transplanting, the EC value of the nutrient solution should be 0.8~1.0 mS / cm; during the growing season, the EC value of the nutrient solution should be 1.2 mS / cm~1.5 mS / cm.

6. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 5, characterized in that, The pH value of the nutrient solution is 6.0 to 6.

5.

7. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 6, characterized in that, The temperature conditions for transplanting and hydroponically cultivating lettuce seedlings are as follows: daytime temperature controlled at 20℃~25℃, nighttime temperature controlled at 14℃~18℃, and nutrient solution temperature controlled at 15℃~22℃.

8. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 7, characterized in that, The humidity conditions for transplanting and hydroponically cultivating the lettuce seedlings are: air humidity controlled at 60% to 80%.

9. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 8, characterized in that, The light conditions for transplanting and hydroponically cultivating the lettuce seedlings are as follows: In the cultivation environment of the plant factory, artificial light sources with a red-blue light ratio of (3~5):1 are used for more than 8 hours of irradiation. And / or, in a greenhouse precision cultivation environment, in addition to daily natural light, add a combination of artificial light sources with a red-blue light ratio of (3~5):1 for more than 3 hours of irradiation.

10. The method for cultivating hydroponically grown lettuce according to any one of claims 1 to 9, characterized in that, Transplant the seedlings when they have grown 2-3 true leaves.