Cultivation method of selenium-rich seedling vegetables

Abstract

The invention belongs to the technical field of cultivation, and particularly relates to a selenium-rich seedling vegetable cultivation method which comprises the steps of seed treatment, sowing, germination acceleration and nutrient solution spraying and further comprises the following steps: selenium-containing solution cultivation: after nutrient solution spraying, sodium selenite with the concentration of 15-35 M is used for cultivation; illumination: after germination accelerating, irradiating with mixed light of red light, blue light and green light to obtain the selenium-rich seedling vegetables; the light intensity ratio of the red light to the blue light to the green light is (22-23): (6-7): (1-2). According to the method, sodium selenite is used as an exogenous selenium fertilizer, and red, blue and green light is used as mixed light, so that the total selenium content and the organic selenium content in the radishes and the peas are increased.

Description

Technical Field

[0001] The invention belongs to the technical field of cultivation, and in particular relates to a method for cultivating selenium-enriched seedlings. Background Art

[0002] Selenium is an essential trace element for the human body. It has multiple biological functions such as anti-oxidation, anti-aging, anti-cancer, and improving the body's immunity. Sufficient dietary intake of selenium is of great significance to ensuring human health and avoiding invisible hunger. At present, the traditional concept of "food supplements are better than medicine supplements" has made the production of selenium-rich agricultural products more and more respected, the market demand is increasing, and the promotion of selenium-rich agricultural technology has a good prospect. However, traditional field selenium enrichment depends on the selenium enrichment level of the soil and the application of selenium fertilizers. Due to the poor uniformity of soil selenium content, low effectiveness of selenium forms, accumulation of selenium absorption by field crops, and low conversion of organic selenium, it is difficult to obtain a large amount of high-quality selenium-rich agricultural products with consistent selenium enrichment levels by relying solely on selenium-rich soils. At the same time, even if the method of artificial spraying of selenium fertilizers is used as an aid, it is difficult to ensure the selenium enrichment level and the quality of agricultural products, and it is impossible to carry out year-round production. More importantly, open-field selenium-enriched production is limited by natural conditions, and pests and diseases are inevitable. It is difficult to ensure stable and high yields. Pollution caused by pesticide residues and heavy metals associated with the soil occurs frequently, making it impossible to produce and guarantee high-quality, high-selenium-enriched agricultural products. Using hydroponic vegetables to enrich selenium is an effective way for the human body to supplement selenium. During the hydroponic process, seeds are usually sprayed with nutrient solution to promote seed germination. After the seeds germinate and take root, they are cultivated. How to obtain hydroponic lettuce that is effectively enriched with organic selenium has become a technical problem that urgently needs to be solved in this technical field.

[0003] There are many varieties of seedlings, including pea seedlings, radish seedlings, peanut seedlings, toon seedlings, sunflower seedlings, alfalfa seedlings, etc. Compared with ordinary vegetables, seedlings have a crisper taste, rich nutrition, short growth cycle, and are easy to obtain. They are increasingly popular with the public in recent years. Studies have shown that some macromolecular proteins in seeds can be decomposed into small molecular proteins, polypeptides, and free amino acids during germination, which can not only improve the nutrition of seedlings, but also be more easily digested and absorbed by the human body. In the prior art, sodium selenate is usually used. Although sodium selenate can be quickly transported to the aboveground part of the plant to achieve selenium-enriched vegetables, it is easy to cause plant selenate poisoning, affecting the normal growth and development of plants. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for cultivating selenium-enriched seedlings.

[0005] A method for cultivating selenium-rich seedlings and vegetables, comprising seed treatment, sowing, germination, spraying nutrient solution, and further comprising the following steps: Selenium-containing solution cultivation: After spraying the nutrient solution, use a sodium selenite solution with a concentration of 15 µM~35 µM for cultivation; Lighting: after germination, irradiation with a mixture of red light, blue light and green light is performed to obtain the selenium-rich seedlings; The light intensity ratio of the red light, the blue light and the green light is 22-23:6-7:1-2.

[0006] Preferably, the intensity of the mixed light is 200 µmol∙m -2 ∙s -1 ~500µmol∙m -2 ∙s -1 , the photoperiod is 12 h~24 h.

[0007] Preferably, the mixed light is located 30 cm to 50 cm above the seedlings.

[0008] Preferably, during germination and cultivation in sodium selenite solution, the temperature is maintained at 23°C to 27°C, the relative humidity is 50% to 70%, and the CO2 concentration is maintained at 400 ppm to 500 ppm.

[0009] Preferably, the seed treatment is to soak the seeds in water until they turn white.

[0010] Preferably, the sowing is hydroponic sowing.

[0011] Preferably, during hydroponics, the distance between the seeds and the sodium selenite solution is 0.5 cm to 1 cm.

[0012] Preferably, the sodium selenite solution circulates.

[0013] Preferably, the nutrient solution is Hoagland nutrient solution.

[0014] Preferably, the seedlings are radish and peas.

[0015] Preferably, the harvest period of the seedlings is 10 to 20 days.

[0016] Preferably, the selenium refers to total selenium and organic selenium.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses sodium selenite as an exogenous selenium fertilizer and red, blue and green light as mixed light to increase the total selenium and organic selenium contents in radish and peas. The total selenium and organic selenium contents in the red, blue and green light treatment are significantly higher than those in the red and blue light treatment, and it is found that adding a small amount of green light can promote plant growth and selenium enrichment. Therefore, a seedling and vegetable cultivation method based on sodium selenite as an exogenous selenium fertilizer and red, blue and green light as mixed light is proposed.

[0018] The present invention uses the composite index of yield-total selenium content-organic selenium content as a standard to determine the optimal light quality and formula composition of seedlings and vegetables; although selenate can be quickly transported to the aboveground part of the plant, it is easy to cause selenate poisoning of the plant. The present invention uses sodium selenite as an exogenous selenium fertilizer, first accumulates in the root and is converted into organic selenium, and then the organic selenium is transported to the aboveground part. The composite index of yield-total selenium content-organic selenium content is used to determine the optimal sodium selenite fertilizer concentration for producing selenium-rich seedlings and vegetables. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure 2 shows the effect of sodium selenite concentration on the total selenium content of radish and pea seedlings. The lowercase letters in the same plant indicate significant differences among treatments (p<0.05), and the error bars indicate the standard deviation.

[0020] Figure 2 Effect of sodium selenite concentration on the organic selenium content of radish and pea sprouts.

[0021] Figure 3 This figure shows the effects of red, blue and green light quality on the total selenium content of radish and pea seedlings. The lowercase letters in the same plant indicate significant differences among treatments (p<0.05), and the error bars indicate standard deviations.

[0022] Figure 4 This paper studies the effects of red, blue and green light quality on the organic selenium content of radish and pea seedlings. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0024] In the process of seed germination, the use of exogenous essential elements for biofortification is a simple, efficient and low-cost method to improve the nutritional value of seedlings. Treatment with exogenous Se at an appropriate concentration can promote the growth of seedlings, increase the active ingredients such as phenols and flavonoids in seedlings, and convert inorganic Se into organic Se that is more easily absorbed by the human body. The organic Se in plant seedlings has high anti-cancer activity and can be used as food for preventing and treating cancer. Therefore, the present invention uses seedlings widely consumed in Asian countries as carriers for Se biofortification, especially cruciferous vegetables.

[0025] The present invention determines the LED light quality and formula parameters for efficiently producing selenium-rich seedlings and vegetables, and determines the optimal light quality and formula composition of seedlings and vegetables based on the composite index of yield-total selenium content-organic selenium content. Sodium selenite is used as an exogenous selenium fertilizer, which is better than sodium selenate as an exogenous selenium fertilizer. The optimal sodium selenite fertilizer concentration for producing selenium-rich seedlings and vegetables is determined based on the composite index of yield-total selenium content-organic selenium content, thereby ensuring the production of high-quality, high-yield and high-selenium-rich seedlings and vegetables.

[0026] Artificial light plant factory is an advanced form of facility horticulture development. It has the advantages of high precision of production factor control, high resource utilization, year-round continuous production, safe and clean agricultural products, etc. It is an inevitable trend of future facility horticulture development. As a cold light source, LED light source greatly reduces the production energy consumption of artificial light plant factory. At the same time, LED light source can modulate the spectrum according to the physiological needs of plants, and can intelligently control the light environment according to the time and space needs of plant production, which greatly improves the output level and quality of agricultural products in artificial light plant factory. Obviously, compared with the production of selenium-rich agricultural products in the field, artificial light plant factory is more suitable for the production of selenium-rich vegetables, selenium-rich medicinal plants, selenium-rich strawberries, selenium-rich forage and other plant products. It can not only realize year-round automation, large-scale and standardized production, but also the high yield, good quality and selenium-rich level of selenium-rich plants are guaranteed to a certain extent. It is an important method for the production of selenium-rich agricultural products in the future.

[0027] Artificial light plant factories are ideal facilities for producing selenium-rich seedlings and vegetables. Through three-dimensional multi-layer cultivation, automated nutrient solution selenium fertilizer management, and precise environmental control, they can produce high-quality, high-selenium-enriched selenium seedlings and vegetables on a large scale throughout the year. Artificial light plant factories do not occupy arable land and can use various buildings for production (such as factories, basements, color steel plate rentals, etc.). They are especially suitable for production in urban communities and local production and sales. They have the characteristics of high resource efficiency, low carbon, labor saving, and easy management. Therefore, the production of selenium-rich plants in plant factories has incomparable advantages over large-field selenium-rich production, and will definitely have broad application prospects.

[0028] The method of the present invention can achieve the final effect by maintaining the temperature at 23° C. to 27° C., the relative humidity at 50% to 70%, and the CO2 concentration at 400 ppm to 500 ppm during the germination and selenium-containing solution cultivation process.

[0029] Example 1 A method for cultivating selenium-rich seedlings comprises the following steps: Seed treatment: Select seeds of uniform size and full grains, weigh radish seeds and place them in a beaker, wash the seeds 3 times, and soak the radish seeds in room temperature water for 12 h.

[0030] Sowing: Sow the seeds in the cultivation tray. The cultivation tray is divided into a tray and a chassis. There is a gap between the bottom of the tray and the bottom of the chassis. Use 0.1% potassium permanganate solution to soak and disinfect the cultivation tray, then wash it. Spread a layer of gauze on the tray for later use. The specific sowing process is: after the seeds turn white, place the seeds evenly in the tray of the cultivation tray, arrange the seeds evenly and leave a certain gap, and place the cultivation tray on the culture rack.

[0031] Germination: The temperature is maintained at 25°C, the relative humidity is 60%, and the CO2 concentration is maintained at 450 ppm. This temperature, relative humidity, and CO2 concentration continue until the end of cultivation. Germination is carried out in a dark place for one day after sowing.

[0032] Lighting: LED lighting was carried out on the second day after sowing. The LED light board was 40 cm vertically above the cultivation tray, and the red, blue and green mixed light was 360 µmol / m 2 / s, the photoperiod was 16 h:8 h, the light intensity ratio of red, blue and green light was 22:6:2, and the lighting lasted until the end of cultivation.

[0033] Spraying nutrient solution: On the first day after germination, spray 1 / 2 concentration of Hoagland nutrient solution. The formula of Hoagland nutrient solution is shown in Table 1. Use an insulation cover to maintain the humidity of the seed coat.

[0034] Selenium-containing solution cultivation: After spraying Hoagland nutrient solution, start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are regularly exchanged within the same treatment and harvested after 12 days.

[0035] Example 2 A method for cultivating selenium-rich seedlings, which differs from Example 1 in that the seedlings are different, specifically comprises the following steps: Seed treatment: Select seeds of uniform size and full grains, weigh the pea seeds and place them in a beaker, wash the seeds three times, and soak the pea seeds in room temperature water for 24 h.

[0036] Sowing: Sow the seeds in the cultivation tray. The cultivation tray is divided into a tray and a chassis. There is a gap between the bottom of the tray and the bottom of the chassis. Use 0.1% potassium permanganate solution to soak and disinfect the cultivation tray, then wash it. Spread a layer of gauze on the tray for later use. The specific sowing process is: after the seeds turn white, place the seeds evenly in the tray of the cultivation tray, arrange the seeds evenly and leave a certain gap, and place the cultivation tray on the culture rack.

[0037] Germination: The temperature is maintained at 25°C, the relative humidity is 60%, and the CO2 concentration is maintained at 450 ppm. This temperature, relative humidity, and CO2 concentration continue until the end of cultivation. Germination is carried out in a dark place for one day after sowing.

[0038] Lighting: LED lighting was carried out on the second day after sowing. The LED light board was 40 cm vertically above the cultivation tray, and the red, blue and green mixed light was 360 µmol / m 2 / s, the photoperiod was 16 h:8 h, the light intensity ratio of red, blue and green light was 22:6:2, and the lighting lasted until the end of cultivation.

[0039] Spraying nutrient solution: On the first day after germination, spray 1 / 2 concentration of Hoagland nutrient solution. The formula of Hoagland nutrient solution is shown in Table 1. Use an insulation cover to maintain the humidity of the seed coat.

[0040] Selenium-containing solution cultivation: After spraying Hoagland nutrient solution, start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are regularly exchanged within the same treatment and harvested after 12 days.

[0041] Example 3 A method for cultivating selenium-rich seedlings, which differs from Example 2 in that the ratio of red, blue and green light is different, specifically comprises the following steps: Seed treatment: Select seeds of uniform size and full grains, weigh the pea seeds and place them in a beaker, wash the seeds three times, and soak the pea seeds in room temperature water for 24 h.

[0042] Sowing: Sow the seeds in the cultivation tray. The cultivation tray is divided into a tray and a chassis. There is a gap between the bottom of the tray and the bottom of the chassis. Use 0.1% potassium permanganate solution to soak and disinfect the cultivation tray, then wash it. Spread a layer of gauze on the tray for later use. The specific sowing process is: after the seeds turn white, place the seeds evenly in the tray of the cultivation tray, arrange the seeds evenly and leave a certain gap, and place the cultivation tray on the culture rack.

[0043] Germination: The temperature is maintained at 23°C, the relative humidity is 50%, and the CO2 concentration is maintained at 400 ppm. This temperature, relative humidity, and CO2 concentration continue until the end of cultivation. Germination is carried out in the dark for one day after sowing.

[0044] Lighting: LED lighting was carried out on the second day after sowing. The LED light board was 40 cm vertically above the cultivation tray, and the red, blue and green mixed light was 360 µmol / m 2 / s, the photoperiod was 16 h:8 h, the light intensity ratio of red, blue and green light was 23:6:1, and the lighting lasted until the end of cultivation.

[0045] Spraying nutrient solution: On the first day after germination, spray 1 / 2 concentration of Hoagland nutrient solution. The formula of Hoagland nutrient solution is shown in Table 1. Use an insulation cover to maintain the humidity of the seed coat.

[0046] Selenium-containing solution cultivation: After spraying Hoagland nutrient solution, start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are regularly exchanged within the same treatment and harvested after 12 days.

[0047] Example 4 A method for cultivating selenium-rich seedlings, which differs from that of Example 3 in that the mixed light conditions are different, specifically comprises the following steps: Seed treatment: Select seeds of uniform size and full grains, weigh the pea seeds and place them in a beaker, wash the seeds three times, and soak the pea seeds in room temperature water for 24 h.

[0048] Sowing: Sow the seeds in the cultivation tray. The cultivation tray is divided into a tray and a chassis. There is a gap between the bottom of the tray and the bottom of the chassis. Use 0.1% potassium permanganate solution to soak and disinfect the cultivation tray, then wash it. Spread a layer of gauze on the tray for later use. The specific sowing process is: after the seeds turn white, place the seeds evenly in the tray of the cultivation tray, arrange the seeds evenly and leave a certain gap, and place the cultivation tray on the culture rack.

[0049] Germination: The temperature is maintained at 23°C, the relative humidity is 50%, and the CO2 concentration is maintained at 400 ppm. This temperature, relative humidity, and CO2 concentration continue until the end of cultivation. Germination is carried out in the dark for one day after sowing.

[0050] Lighting: LED lighting was carried out on the second day after sowing. The LED light board was 40 cm vertically above the cultivation tray, and the red, blue and green mixed light was 200 µmol / m 2 / s, the photoperiod was 12 h:10 h, the light intensity ratio of red, blue and green light was 23:6:1, and the lighting lasted until the end of cultivation.

[0051] Spraying nutrient solution: On the first day after germination, spray 1 / 2 concentration of Hoagland nutrient solution. The formula of Hoagland nutrient solution is shown in Table 1. Use an insulation cover to maintain the humidity of the seed coat.

[0052] Selenium-containing solution cultivation: After spraying Hoagland nutrient solution, start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are regularly exchanged within the same treatment and harvested after 12 days.

[0053] Example 5 A method for cultivating selenium-rich seedlings, which differs from that of Example 4 in that the mixed light conditions are different, specifically comprises the following steps: Seed treatment: Select seeds of uniform size and full grains, weigh the pea seeds and place them in a beaker, wash the seeds three times, and soak the pea seeds in room temperature water for 24 h.

[0054] Sowing: Sow the seeds in the cultivation tray. The cultivation tray is divided into a tray and a chassis. There is a gap between the bottom of the tray and the bottom of the chassis. Use 0.1% potassium permanganate solution to soak and disinfect the cultivation tray, then wash it. Spread a layer of gauze on the tray for later use. The specific sowing process is: after the seeds turn white, place the seeds evenly in the tray of the cultivation tray, arrange the seeds evenly and leave a certain gap, and place the cultivation tray on the culture rack.

[0055] Germination: The temperature is maintained at 23°C, the relative humidity is 50%, and the CO2 concentration is maintained at 400 ppm. This temperature, relative humidity, and CO2 concentration continue until the end of cultivation. Germination is carried out in the dark for one day after sowing.

[0056] Lighting: LED lighting was carried out on the second day after sowing. The LED light board was 40 cm vertically above the cultivation tray, and the red, blue and green mixed light was 500 µmol / m 2 / s, the photoperiod was 24 h, the light intensity ratio of red, blue and green light was 23:6:1, and the lighting lasted until the end of cultivation.

[0057] Spraying nutrient solution: On the first day after germination, spray 1 / 2 concentration of Hoagland nutrient solution. The formula of Hoagland nutrient solution is shown in Table 1. Use an insulation cover to maintain the humidity of the seed coat.

[0058] Selenium-containing solution cultivation: After spraying Hoagland nutrient solution, start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are regularly exchanged within the same treatment and harvested after 12 days.

[0059] Verification experiment 1. Effects of exogenous sodium selenite concentration on seedling growth and selenium enrichment under LED red and blue light 1. Test materials Cultivation device: The cultivation tray (18 cm × 8 cm × 5 cm) is divided into a tray and a base tray. It is soaked and disinfected in 0.1% potassium permanganate solution and then washed. A layer of gauze is spread on the tray for later use.

[0060] Seed treatment: Select seeds of uniform size and full grains, weigh radish and pea seeds and place them in beakers respectively, and wash the seeds 2-3 times. Soak pea seeds in room temperature water for 24 hours and radish seeds for 12 hours. After the seeds turn white, place them evenly in the tray of the cultivation tray, place the seeds evenly and leave some gaps, and place the cultivation tray on the cultivation rack.

[0061] Artificial light plant factory (PFAL) and LED panel lights: The temperature of PFAL was maintained at 25±2℃ and the relative humidity was 50%~70% during the whole experiment. The CO2 concentration was maintained at 450±50 ppm. A composite LED panel light consisting of red (660±15 nm), blue (530±12 nm) and green (460±12 nm) was used (Wuxi Huazhaohong Optoelectronics Technology Co., Ltd., Wuxi, China), with a size of 50 cm×50 cm. The light panel was 40 cm vertically above the experimental cultivation tray. The light intensity was measured on the upper surface of the tray and the experimental light intensity was set. After sowing, the seeds were protected from light for one day. The next day, LED illumination was carried out, with a red and blue mixed light (4:1) of 360 µmol / m 2 / s, and the photoperiod was 16 h:8 h.

[0062] Selenium-containing nutrient solution: In the early stage, spray 1 / 2 concentration of Hoagland nutrient solution (Table 1), use a heat-insulating cover to maintain the humidity of the seed coat, and start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the position is regularly exchanged within the same treatment.

[0063] Table 1 Composition of Hoagland nutrient solution 2. Experimental processing and management Selenium concentration treatment: 15 µM, 25 µM, 35 µM, 45 µM and 55 µM sodium selenite solutions were prepared with Hoagland nutrient solution as solvent and added to the bottom plate respectively. The liquid level was level with the bottom of the tray. No selenium was used as the control (CK, four replicates were set for each group).

[0064] Harvesting method and determination method: The seedlings were harvested after 12 days of cultivation. The roots and hypocotyls were separated during harvesting, rinsed with deionized water, dried with absorbent paper, and placed in a tin foil bag. After quick freezing with liquid nitrogen, they were ground into powder at low temperature and stored at -80°C for testing. An appropriate amount of fresh samples were freeze-dried. The total selenium content was determined by referring to the method in "Determination of Selenium in Food GB5009.93-2017". After microwave digestion, hydride atomic fluorescence spectrometry was used for detection; the samples needed to be pretreated before the determination of inorganic selenium content. Weigh 0.2 g of dry sample and place it in a stoppered test tube. Add 10 mL of 50% hydrochloric acid solution, mix well, extract by ultrasonic extraction for 30 min, and then extract in a boiling water bath for 30 min. After cooling, filter with a 0.45 µm water filter membrane to obtain the inorganic selenium extract. The determination method is the same as that of total selenium. The organic selenium content of seedlings is the difference between the total selenium content and the inorganic selenium content.

[0065] 3. Test results and analysis With the increase of sodium selenite concentration in the nutrient solution, the aboveground fresh weight of radish and pea seedlings first increased and then decreased. Except for the pea seedlings that were not treated with selenium, the plant height also showed a pattern of first increasing and then decreasing. This is because the appropriate concentration of sodium selenite solution can promote the growth of radish and pea seedlings, increase plant height and fresh weight, while excessively high concentrations of sodium selenite will be toxic to the seedlings and inhibit their growth. In this study, when the concentration of sodium selenite was 25 µM, the plant height and fresh weight of radish seedlings reached the maximum; among the pea seedlings treated with selenium, the 35 µM treatment group had the largest plant height and aboveground fresh weight, indicating that pea seedlings have a higher selenium tolerance than radish seedlings. On the other hand, Figure 1 It can be seen that the total selenium content in radish seedlings first increased and then decreased with the increase of the concentration of exogenous sodium selenite, which is similar to the growth index. When the concentration of exogenous sodium selenite was 35 µM, the total selenium content reached a maximum of 95.45 mg / kg, which was significantly higher than other treatments. Figure 2 The trend of organic selenium content in radish seedlings was consistent with that of total selenium content, reaching a maximum of 71.59 mg / kg when the concentration of exogenous sodium selenite was 35 µM. The total selenium and organic selenium contents of pea seedlings reached the highest when the concentration of exogenous sodium selenite was 25 µM, which were 10.82 mg / kg and 8.53 mg / kg, respectively. Although pea seedlings have a higher tolerance to sodium selenite than radish seedlings and can still grow well at higher selenium concentrations, their selenium enrichment ability is far less than that of radish seedlings.

[0066] Table 2 Effects of sodium selenite concentration on growth indicators of radish and pea seedlings under LED red and blue light Note: The data in the table are mean ± standard deviation; and the lowercase letters after the data of the same plant in the same column indicate significant differences at the p<0.05 level.

[0067] 4. Test conclusion When the sodium selenite concentration was 25 µM, the plant height and fresh weight of radish seedlings reached the maximum, while the total selenium and organic selenium contents were the highest when the sodium selenite concentration was 35 µM; among the pea seedlings, the plant height and aboveground fresh weight were the largest in the 35 µM treatment group, and the total selenium and organic selenium contents were the highest in the 25 µM treatment group. Based on the comprehensive indicators of plant height, fresh weight, total selenium and organic selenium contents, the optimal sodium selenite concentration for radish and pea seedlings was 35 µM, at which the seedlings obtained a higher organic selenium content without affecting their normal growth.

[0068] 2. Effects of LED red, blue and green light quality on seedling growth and selenium enrichment 1. Test materials Cultivation device: The cultivation tray (18 cm × 8 cm × 5 cm) is divided into a tray and a base tray. It is soaked and disinfected in 0.1% potassium permanganate solution and then washed. A layer of gauze is spread on the tray for later use.

[0069] Seed treatment: Select seeds of uniform size and full grains, weigh radish and pea seeds and place them in beakers respectively, and wash the seeds 2-3 times. Soak pea seeds in room temperature water for 24 hours and radish seeds for 12 hours. After the seeds turn white, place them evenly in the tray of the cultivation tray, place the seeds evenly and leave some gaps, and place the cultivation tray on the cultivation rack.

[0070] Artificial light plant factory (PFAL) and LED panel lights: The temperature of the PFAL was maintained at 25±2℃ and the relative humidity was 50%~70% during the whole experiment. The CO2 concentration was maintained at 450±50 ppm. A composite LED panel light consisting of red (660±15 nm), blue (530±12 nm) and green (460±12 nm) was used (Wuxi Huazhaohong Optoelectronics Technology Co., Ltd., Wuxi, China), with a size of 50 cm×50 cm. The light panel was located 40 cm vertically above the experimental cultivation tray. The light intensity was measured on the upper surface of the tray and the experimental light intensity was set. After sowing, the seeds were protected from light for one day. The LED illumination was carried out on the second day, and the light intensity was set to 360 µmol / m 2 / s, the red, blue and green ratios are shown in Table 3, and the photoperiod is 16 h:8 h.

[0071] Table 3 Experimental light quality treatment parameters “-” in the table means no addition.

[0072] Selenium-containing nutrient solution: In the early stage, spray 1 / 2 concentration of Hoagland nutrient solution, use an insulation cover to maintain the humidity of the seed coat, and start from the fifth day to prepare sodium selenite solution with gradient concentration using Hoagland nutrient solution as solvent and add it to the bottom tray. The liquid level should be level with the bottom of the tray. Stir the sodium selenite solution every day to facilitate the supply of dissolved oxygen. In order to ensure that each replicate receives the same light, the positions are exchanged regularly within the same treatment.

[0073] 2. Experimental processing and management Selenium concentration treatment: Based on the results of the previous selenium concentration test, a 35 µM sodium selenite solution was prepared to enrich each treatment with selenium and added to the bottom tray so that the liquid level was level with the bottom of the tray (four replicates were set for each group).

[0074] Harvesting method and determination method: The seedlings were harvested after 12 days of cultivation. The roots and hypocotyls were separated during harvesting, rinsed with deionized water, dried with absorbent paper, and placed in a tin foil bag. After quick freezing with liquid nitrogen, they were ground into powder at low temperature and stored at -80°C for testing. An appropriate amount of fresh samples were freeze-dried. The total selenium content was determined by referring to the method in "Determination of Selenium in Food GB5009.93-2017". After microwave digestion, hydride atomic fluorescence spectrometry was used for detection; the samples needed to be pretreated before the determination of inorganic selenium content. Weigh 0.2 g of dry sample and place it in a stoppered test tube. Add 10 mL of 50% hydrochloric acid solution, mix well, extract by ultrasonic extraction for 30 min, and then extract in a boiling water bath for 30 min. After cooling, filter with a 0.45 µm water filter membrane to obtain the inorganic selenium extract. The determination method is the same as that of total selenium. The organic selenium content of seedlings is the difference between the total selenium content and the inorganic selenium content.

[0075] 3. Test results and analysis The addition of green light increased the plant height and aboveground fresh weight of radish and pea seedlings. The plant height reached the maximum in the R22B6G2 treatment, and the aboveground fresh weight reached the maximum in the R23B6G1 treatment. This may be because the addition of green light activated the light sensors in the seedlings, counteracting growth inhibition, thereby promoting early growth and stem elongation. In terms of selenium enrichment, the addition of green light increased the total selenium content of radish and pea seedlings, reaching a maximum of 124.0 mg / kg and 10.17 mg / kg in the R22B6G2 treatment, which was significantly higher than the red and blue light treatment. The organic selenium content of radish and pea seedlings was also the highest in the R22B6G2 treatment, reaching 69.14 mg / kg and 6.41 mg / kg. The total selenium and organic selenium content of the red, blue and green light treatments were significantly higher than those of the red and blue light treatments. This may be because green light plays a role in plant growth and development, and a small amount of green light can promote plant growth and selenium enrichment.

[0076] Table 4 Effects of red, blue and green light quality on growth indicators of radish and pea seedlings Note: The data in the table are mean ± standard deviation; and the lowercase letters after the data of the same plant in the same column indicate significant differences at the p<0.05 level.

[0077] 4. Test conclusion The addition of green light not only increased the plant height and fresh weight of radish and pea seedlings, but also promoted the absorption and conversion of selenium in seedlings. Based on the comprehensive indicators of plant height, fresh weight, total selenium and organic selenium, the best light quality treatment for radish and pea seedlings was R22B6G2. Due to the plant species, the total selenium and organic selenium content of radish seedlings is 10-14 times that of pea seedlings, and radish seedlings have greater potential for factory production as selenium-rich seedlings.

[0078] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0079] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for cultivating selenium-enriched seedlings, comprising seed treatment, sowing, germination, and spraying nutrient solution, characterized in that: The following steps are also included: Selenium-containing solution cultivation: After spraying the nutrient solution, use a sodium selenite solution with a concentration of 15 µM~35 µM for cultivation; Lighting: after germination, irradiation with a mixture of red light, blue light and green light is performed to obtain the selenium-rich seedlings; The light intensity ratio of the red light, the blue light and the green light is 22-23:6-7:1-2.

2. The cultivation method according to claim 1, characterized in that The intensity of the mixed light is 200 µmol∙m -2 ∙s -1 ~500µmol∙m -2 ∙s -1 , the photoperiod is 12 h~24 h.

3. The cultivation method according to claim 1, characterized in that The mixed light is located 30 cm to 50 cm above the seedlings.

4. The cultivation method according to claim 1, characterized in that: During germination and cultivation in sodium selenite solution, the temperature is maintained at 23℃~27℃, the relative humidity is 50%~70%, and the CO2 concentration is maintained at 400 ppm~500 ppm.

5. The cultivation method according to claim 1, characterized in that: The seed treatment is to soak the seeds in water until they turn white.

6. The cultivation method according to claim 1, characterized in that: The sowing is hydroponic sowing.

7. The cultivation method according to claim 6, characterized in that: During hydroponics, there is a distance of 0.5cm~1cm between the seeds and the sodium selenite solution.

8. The cultivation method according to claim 1, characterized in that: The nutrient solution is Hoagland nutrient solution.

9. The cultivation method according to claim 1, characterized in that: The seedling vegetables are radish and peas.

10. The cultivation method according to claim 1, characterized in that: The selenium mentioned above refers to total selenium and organic selenium.

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