Method for regulating and controlling salt tolerance of rice seedlings by light

Abstract

The invention relates to the field of seedling cultivation biotechnology, and provides a method for regulating and controlling salt tolerance of rice seedlings by light, which is used for improving the salt tolerance of the rice seedlings. According to the method, the rice seedlings are subjected to illumination treatment by adjusting the proportion of blue light, red light and far-red light sources. According to the technology, the growth quality of the rice seedlings is improved by accurately controlling spectrum setting, particularly, the salt resistance of the rice seedlings can be remarkably improved, the survival rate of the rice seedlings under the salt stress condition is increased, and the technology has important application value for agricultural production.

Description

Technical Field

[0001] The present invention relates to the field of rice seedling cultivation biotechnology, and specifically to a method for light-regulated rice seedling salt tolerance, which regulates the ratio of blue light, red light and far-red light sources for rice seedlings. The results show that the technology significantly improves the rice seedlings' seedling index and salt tolerance. Background Art

[0002] With global climate change and unreasonable agricultural irrigation, soil salinization is becoming increasingly serious, seriously affecting the yield and quality of crops. As one of the most important food crops in the world, the study of rice seedling salt tolerance is of great significance for increasing crop yield and ensuring food security. Salt stress can cause plant growth stunting, physiological metabolic disorders, and even death. Therefore, exploring effective salt tolerance regulation technology has important scientific value and application prospects for improving the adaptability and productivity of rice in salinized soils.

[0003] Traditional salt-tolerant breeding methods have long cycles and low efficiency, while modern biotechnology provides a new approach for studying the molecular mechanisms of rice salt tolerance and breeding. Studies have shown that light, as an important environmental factor, has a significant impact on plant growth and development and salt tolerance. Changes in light quality, light intensity, and photoperiod will affect plant photosynthesis, energy metabolism, and hormone signal transduction, thereby affecting plant responses to salt stress.

[0004] However, the current research on light regulation of rice seedling salt tolerance is not in-depth enough, especially the synergistic effect of different ratios of blue light, red light and far-red light on rice salt tolerance is still unclear. Therefore, developing an effective light regulation method to improve the salt tolerance of rice seedlings by precisely controlling the ratio of blue light, red light and far-red light has important theoretical and practical significance for promoting rice salt tolerance breeding and cultivation. Summary of the invention

[0005] The purpose of the present invention is to provide a method for optimizing the growth environment of rice seedlings by precisely controlling the ratio of blue light, red light and far-red light, thereby improving their tolerance to salt stress. This method can not only reduce the dependence on chemical fertilizers and water resources, but also reduce the impact of agricultural production on the environment, while improving the yield and quality of rice. Through this method, we can provide rice growers with an environmentally friendly and efficient salt-tolerant cultivation technology, enhance the adaptability and growth potential of rice seedlings in salinized soil, to cope with the increasingly severe problem of salinized soil, and ensure food security.

[0006] A method for light-regulated salt tolerance of rice seedlings, which improves the salt tolerance of rice seedlings by adjusting the blue / red light ratio, the red / far-red light ratio or the blue / red / far-red light ratio to perform light treatment on the rice seedlings.

[0007] The method comprises cultivating rice seedlings under ordinary white light or full-spectrum white light for 20 days until the two-leaf and one-heart stage, and then switching to adjusted blue / red light ratio, red / far-red light ratio and blue / red / far-red light ratio to perform light treatment on the rice seedlings.

[0008] Further,

[0009] Set the blue / red light ratio to 0.10~5.00;

[0010] Set the red / far-red light ratio to 0.10~5.00.

[0011] Further preferred:

[0012] Set the blue / red light ratio interval to [0.5, 4], preferably [0.50, 1.50);

[0013] Set the red / far-red light ratio interval to [1, 4], preferably [1.00, 3.50);

[0014] Or set the blue / red / far-red light ratio to [0.50,1.50):[0.50,1.50):[0.50,1.50), [1.50,3.50):[1.50,3.50):[0.50,1.50), [3.50,5.00):[3.50,5.00):[0.50,1.50), [0.50,1.50):[1.50,3.50):[0.50,1.50) or [3.50,5.00):[1.50,3.50):[0.50,1.50);

[0015] Further preferred:

[0016] Set the blue / red / far-red light ratio to [1.50,3.50):[1.50,3.50):[0.50,1.50);

[0017] In the above ratio range, “[” and “]” indicate that the ratio can be equal to the ratio, and “)” indicates that the ratio cannot be equal to the ratio.

[0018] Furthermore,

[0019] The ordinary white light has a wavelength of 400 to 770 nm;

[0020] The full spectrum white light has a wavelength of 400 to 770 nm;

[0021] The blue light wavelength range is 450-490nm;

[0022] The red light wavelength range is 620-700nm;

[0023] The far-infrared light has a wavelength of 700-770 nm.

[0024] The light source is an LED lamp, and the light intensity of the light source is 250-300 μmol m -2 s -1 ; The light source is fixed for 16 hours of light and 8 hours of darkness;

[0025] The distance between the light source and the surface of the rice seedling nutrient solution is no more than 0.40 m, and the illumination days are at least 10 days.

[0026] The temperature of the rice seedlings is controlled at 25±5°C, and the humidity is controlled at 75±5%; the CO2 concentration of the rice seedlings is controlled at 800-1100 PPM.

[0027] The NaCl salt concentration that rice can tolerate is 5‰.

[0028] The nutrient solution is changed every 3 to 5 days during the rice seedling stage.

[0029] The rice seedling variety is Nipponbare.

[0030] In the present invention, B represents blue light, R represents red light, and FR represents far-red light.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1) It is possible to improve the salt tolerance of rice seedlings by adjusting the light quality ratio;

[0033] 2) The method is simple and easy to operate;

[0034] 3) Environmentally friendly, no need to use additional chemicals.

[0035] Therefore, the present invention is not only innovative in theory, but also has broad promotion prospects in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the seedling index of the rice seedlings in Example 1;

[0037] Figure 2 is the survival rate of the rice seedlings in Example 1;

[0038] Figure 3 is the change in the content of the osmotic regulating substance in Example 1;

[0039] Figure 4 is the seedling strength index of the rice seedlings in Example 2;

[0040] Figure 5 is the survival rate of rice seedlings in Example 2;

[0041] Figure 6is the change in the content of the osmotic regulating substance in Example 2;

[0042] Figure 7 is the seedling strength index of the rice seedlings in Example 3;

[0043] Figure 8 is the survival rate of rice seedlings in Example 3;

[0044] Fig. 9 is the change in the content of the osmotic regulating substance in Example 3;

[0045] Fig.10 This is a photo of the lighting facility. DETAILED DESCRIPTION

[0046] The present invention is further described and explained in detail below in conjunction with specific implementation cases. Those skilled in the art can implement the present invention based on these descriptions. In addition, the embodiments of the present invention designed in the following cases are only part of the implementation cases of the present invention, rather than all the embodiments. Therefore, based on the embodiments in the present invention, other implementation cases obtained by other technicians without making creative work should all fall within the scope of protection of the present invention.

[0047] Unless otherwise specified, the raw materials used in the implementation of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the implementation of the present invention are all methods known to those skilled in the art.

[0048] Rice morphological index determination of the present invention:

[0049] After 10 days of cultivation under different light quality ratios and salt treatment, 15 rice seedlings were randomly selected, washed with distilled water, and dried with test paper:

[0050] (1) Plant height: Measure plant height from leaf tip to pseudostem base with a ruler;

[0051] (2) Stem diameter: The width of the pseudostem base and the diameter of the taproot were measured using a vernier caliper;

[0052] (3) Fresh weight: Dry the surface moisture with absorbent paper and weigh the fresh weight with an analytical balance;

[0053] (4) Dry weight: 15 fresh samples were placed at 105°C for 30 min, dried at 80°C until constant weight was reached, and their dry weights were measured using an analytical balance and the average value was taken;

[0054] (5) Seedling index: Seedling index = (stem diameter / plant height + underground dry weight / aboveground dry weight) × total dry weight.

[0055] (6) Survival rate: After 10 days of salt treatment, the rice seedlings were rehydrated for 8 days and the survival rate of the rice seedlings was calculated based on the growth of new leaves.

[0056] Proline content determination of the present invention:

[0057] (1) Preparation of acidic ninhydrin reagent: weigh 1.25 g of ninhydrin, add 30 mL of glacial acetic acid and 20 mL of 6 mol·L -1 Phosphoric acid is heated to 70°C and dissolved. After cooling, it is stored in a brown reagent bottle at 4°C and is stable within two days.

[0058] (2) Preparation of standard curve: 0-30 μg·mL -1 Prepare a standard curve within the proline concentration range. Take 8 25 mL stoppered test tubes and number them. Take 0.0, 1.0, 2.5, 5.0, 10.0, 15.0, 20.0, 30.0 μg·mL -1 Add 2mL of a series of proline standard solutions, 2mL of glacial acetic acid, and 2mL of ninhydrin reagent in a test tube, shake well, boil in water for 30 minutes, cool, add 5.0mL of toluene each time, shake well and extract. Let stand in the dark for 2 to 3 hours. After complete stratification, use a pipette to draw the toluene layer, use an enzyme reader to adjust the zero value with the No. 1 standard curve test tube as the blank, and measure the absorbance at a wavelength of 520nm. Draw a standard curve with the proline content as the horizontal axis and the absorbance as the vertical axis. At the same time, use the regression method to obtain the regression line;

[0059] (3) Extraction of proline: Weigh 0.1 g of sample into a 1.5 mL centrifuge tube, add 1 mL of 80% ethanol, grind into a homogenate using a high-throughput tissue grinder, and extract in an 80°C water bath for 20 min. Add about 0.04 g of artificial zeolite (alkaline amino acids interfere with the determination of proline and are adsorbed and removed by artificial zeolite) and 0.02 g of activated carbon to the extract, shake vigorously for 5 min, cool, centrifuge at 3000 rpm for 10 min, and take the supernatant for testing;

[0060] (4) Sample determination: 0.4 mL of the above extract was taken into 1.5 mL centrifuge tubes, and 0.4 mL of glacial acetic acid and 0.4 mL of ninhydrin reagent were added to each of the above test tubes, respectively. The samples were heated in a boiling water bath for 15 min. After cooling, the absorbance of each sample was measured at 520 nm using an ELISA reader. The mass of proline in each mL of the sample solution was found from the standard curve.

[0061] (5) Calculation of results: Proline (μg·g -1 )=(C×V t ) / (W×V s )×100%

[0062] Where, C is the mass of proline (μg) obtained (or calculated) from the standard curve; V t is the total volume of the extract (mL); V sis the volume of the extract used in the determination (mL); W is the fresh weight of the sample (g).

[0063] Determination of malondialdehyde (MDA) content of the present invention:

[0064] (1) Preparation of MDA thiobarbituric acid (TBA) reagent: Weigh 0.15 g of thiobarbituric acid and add a small amount of sodium hydroxide (1 mol·L -1 ) and then dilute to volume with 10% trichloroacetic acid (TCA) to obtain 25 mL of 0.6% thiobarbituric acid reagent;

[0065] (2) MDA extraction: Weigh 0.1 g of chopped rice sample, add 1 mL of 10% TCA, add two 5 mm steel balls and grind using a grinder. Centrifuge the homogenate at 4000 rpm for 10 min. The supernatant is the sample extract.

[0066] (3) Color reaction and determination: Take 0.4 mL of the supernatant after centrifugation (add 0.4 mL of distilled water for control), add 0.4 mL of 0.6% TBA solution, mix well, react in a boiling water bath for 15 min, cool quickly and centrifuge again. Take the supernatant and measure the absorbance at 532, 600 and 450 nm.

[0067] (4) Calculation of results: Sugar substances in plant tissues interfere with the MDA-TBA reaction. To eliminate this interference, the following formula can be used to eliminate the error caused by sucrose:

[0068] MDA content (μmol·g -1 )=[6.45(A 532 -A 600 )-0.56×A 450 ] / NW

[0069] Where: A 450 , A 532 , A 600 Represent the absorbance values ​​at wavelengths of 450, 532 and 600 nm respectively; N is the total volume of the extract (mL); W is the fresh weight of the sample (g).

[0070] Determination of the content of hydrogen peroxide (H2O2) of the present invention:

[0071] (1) Preparation of standard curve: Prepare a standard curve within the range of 0 to 0.1 μmol of hydrogen peroxide. Take 7 2 mL centrifuge tubes, number them, and add reagents to the centrifuge tubes according to Table 1-1. After the precipitate is completely dissolved, carefully transfer it to a 10 mL volumetric flask and rinse the centrifuge tube with distilled water in small amounts several times. Combine the washing liquids and make the volume up to 10 mL. Measure the absorbance at a wavelength of 415 nm. Draw a standard curve with the amount of hydrogen peroxide as the horizontal axis and the absorbance as the vertical axis. At the same time, use the regression method to obtain the regression line;

[0072] (2) Extraction of hydrogen peroxide: weigh 0.1 g of fresh plant tissue into a 2 mL centrifuge tube, add 1.5 mL of acetone precooled at 4°C, grind into a homogenate using a high-throughput tissue grinder, centrifuge at 3000 rpm for 10 min, and take the supernatant for testing;

[0073] (3) Sample determination: Take 1 mL of the above extract into 1.5 mL centrifuge tubes, and add 0.1 mL of 5% titanium sulfate and 0.2 mL of concentrated ammonia water to each of the above centrifuge tubes. After the precipitate is formed, centrifuge at 3000 rpm for 10 min and discard the supernatant. Wash the precipitate twice with acetone to remove the plant pigment. Add 1 mL of 2 mol·L -1 After the samples are completely dissolved, the absorbance of each sample at 415 nm is measured by an enzyme marker, and the amount of hydrogen peroxide in the sample (μmol) is found from the standard curve.

[0074] Table 1 Amount of each reagent added to draw the standard curve

[0075]

[0076] (4) Calculation of results: Hydrogen peroxide (μmol·g -1 )=(C×V t ) / (W×V1)

[0077] Where, C is the amount of hydrogen peroxide (μmol) obtained (or calculated) from the standard curve; V t is the total volume of the extract (mL); V1 is the volume of the extract used during the measurement (mL); W is the fresh weight of the sample (g).

[0078] Soluble protein content determination of the present invention:

[0079] (1) Preparation of Coomassie Brilliant Blue reagent: Weigh 100 mg of Coomassie Brilliant Blue G-250, dissolve in 50 mL of 90% ethanol, add 100 mL of 85% phosphoric acid, and then make up to 1000 mL with distilled water. Store in a brown bottle and store at room temperature for one month.

[0080] (2) Preparation of standard protein solution: Weigh 25 mg of bovine serum albumin (BSA), dissolve it in distilled water and make up to 250 mL to prepare 100 μg mL -1 Bovine serum albumin;

[0081] (3) Preparation of standard curve: Prepare a standard curve in the range of 0-100 μg protein mass. Take 6 test tubes, add reagents according to Table 1-2, shake well, add 5 mL of Coomassie Brilliant Blue reagent to each tube, shake well, and leave for about 5 minutes. Use test tube No. 1 as a blank control and measure the absorbance at 595 nm. Draw a standard curve with protein mass as the horizontal axis and absorbance as the vertical axis. At the same time, use the regression method to obtain the regression line;

[0082] (4) Extraction of soluble protein: Weigh 0.25-0.5 g of fresh sample, add 10 mL of distilled water, grind into a homogenate, centrifuge at 5000 rpm for 10 min, and keep the supernatant for later use;

[0083] (5) Sample determination: Take 1.0 mL of sample extract (appropriately diluted according to the protein content) and put it into a 10 mL centrifuge tube (repeat 3 times for each sample), add 5 mL of Coomassie Brilliant Blue reagent, and shake well. After standing for 2 minutes, measure the absorbance at 595 nm and check the protein mass using the standard curve;

[0084] Table 2 Amount of each reagent added to draw the standard curve

[0085]

[0086] (6) Calculation of results: Soluble protein content (mg·g -1 )=(C×V t ) / (W×V s ×10 3 )

[0087] Where, C is the value (μg) obtained (or calculated) from the standard curve; V t is the total volume of the extract (mL); V s is the volume of the extract used in the determination (mL); W is the fresh weight of the sample (g).

[0088] Example 1

[0089] A method for light-regulated salt tolerance of rice seedlings, the specific steps are as follows

[0090] 1. Experimental methods

[0091] (1) Place the detachable plant supplementary light on the top of the rice seedling raising rack and raise the rice seedlings in a flat surface to ensure uniform light distribution.

[0092] (2) After the rice seeds are sterilized, they are soaked at room temperature for 48 hours and then germinated in a constant temperature and humidity chamber at 37°C for 12 hours. The rice seeds with consistent germination are selected and sown in a germination box on a 96-well plate. The seedling raising environment temperature is 25°C, the relative humidity is 75%, and the CO2 concentration is 1000PPM; it has stable ordinary white light, full-spectrum white light, red light and blue light fixed radiation, and the light intensity is 250μmol·m -2 ·s -1 , fixed light 16h / d, darkness 8h / d to meet the basic light requirements of rice seedling growth.

[0093] (3) First, the rice seedlings were hydroponically cultured under ordinary white light or full-spectrum white light until they reached the two-leaf and one-heart stage. Then, the seedlings were treated with a NaCl salt concentration of 5‰ and transferred to red light and blue light with different ratios, namely R, [0.10, 0.25), [0.25, 0.50), [0.50, 1.50), [1.50, 3.50), [3.50, 5.00], and B. The specific ratios are shown in Tables 3 and 4. One group was left to continue growing under white light as a control, where R represents red light and B represents blue light. After 10 days of growth, samples were taken to test their morphological indicators and salt tolerance indicators. Finally, one box of seedlings from each treatment group was kept and grown under ordinary white light W. P Or full spectrum white light W Q The cells were rehydrated and grown under light for 8 days, and their survival rate was tested. All light exposure times started at 8:00.

[0094] 2. Test results and analysis

[0095] Morphological indexes of rice seedlings after 10 days of salt stress

[0096] Table 3 Rice seedling morphological indexes of Example 1

[0097]

[0098] Determination of stress resistance-related indicators of rice seedlings, and calculation of seedling survival rate 8 days after rehydration

[0099] Table 4: Stress resistance related indicators and survival rate of rice seedlings in Example 1

[0100]

[0101]

[0102] Example 2

[0103] A method for light-regulated salt tolerance of rice seedlings, the specific steps are as follows

[0104] 1. Experimental methods

[0105] (1) Place the detachable plant supplementary light on the top of the rice seedling raising rack and raise the rice seedlings in a flat surface to ensure uniform light distribution.

[0106] (2) After the rice seeds are sterilized, they are soaked at room temperature for 48 hours and then germinated in a constant temperature and humidity chamber at 37°C for 12 hours. The rice seeds with consistent germination are selected and sown in a germination box on a 96-well plate. The seedling raising environment temperature is 25°C, the relative humidity is 75%, and the CO2 concentration is 1000PPM; it has stable ordinary white light, full-spectrum white light, red light and far-red light fixed radiation, and the light intensity is 250μmol·m -2 ·s -1 , fixed light 16h / d, darkness 8h / d to meet the basic light requirements of rice seedling growth.

[0107] (3) First, the rice seedlings were hydroponically cultured under normal white light or full-spectrum white light until the two-leaf one-heart stage; then, the seedlings were treated with a NaCl salt concentration of 5‰ and transferred to different ratios of red light and far-red light, namely FR, [0.10, 0.25), [0.25, 0.50), [0.50, 1.50), [1.50, 3.50), [3.50, 5.00], and R. The specific ratios are shown in Tables 5 and 6. A group was left to continue growing under white light as a control, where R represents red light and FR represents far-red light. After 10 days of growth, samples were taken to test their morphological indicators and salt tolerance indicators; finally, one box of seedlings from each treatment group was kept and rehydrated and grown under normal white light or full-spectrum white light for 8 days to test their survival rate. All lighting times started at 8:00.

[0108] 2. Test results and analysis

[0109] Morphological indexes of rice seedlings after 10 days of salt stress

[0110] Table 5 Rice seedling morphological indexes of Example 2

[0111]

[0112]

[0113] Determination of stress resistance-related indicators of rice seedlings, and calculation of seedling survival rate 8 days after rehydration

[0114] Table 6: Rice seedling stress resistance related indicators and survival rate in Example 2

[0115]

[0116] Example 3

[0117] A method for light-regulated salt tolerance of rice seedlings, the specific steps are as follows

[0118] 1. Experimental methods

[0119] (1) Place the detachable plant supplementary light on the top of the rice seedling raising rack and raise the rice seedlings in a flat surface to ensure uniform light distribution.

[0120] (2) After the rice seeds are sterilized, they are soaked at room temperature for 48 hours and then germinated in a constant temperature and humidity chamber at 37°C for 12 hours. The rice seeds with consistent germination are selected and sown in a germination box on a 96-well plate. The seedling raising environment temperature is 25°C, the relative humidity is 75%, and the CO2 concentration is 1000PPM; it has stable ordinary white light, full-spectrum white light, blue light, red light and far-red light fixed radiation, and the light intensity is 250μmol·m -2 ·s -1 , fixed light 16h / d, darkness 8h / d to meet the basic light requirements of rice seedling growth.

[0121] (3) First, the rice seedlings were hydroponically cultured under ordinary white light or full-spectrum white light until they reached the two-leaf and one-heart stage. Then, the seedlings were treated with a NaCl salt concentration of 5‰ and transferred to different proportions of blue light, red light, and far-red light, respectively: [0.50,1.50):[0.50,1.50):[0.50,1.50), [1.50,3.50):[1.50,3.50):[0.50,1.50), [3.50,5.00):[3.50,5.00):[0.50,1.5 0), [0.50, 1.50): [1.50, 3.50): [0.50, 1.50) or [3.50, 5.00): [1.50, 3.50): [0.50, 1.50), the specific ratio values ​​are shown in Tables 7 and 8, and one group is left to continue growing under white light as a control, where B represents blue light, R represents red light, and FR represents far-red light; after 10 days of growth, samples are taken to test their morphological indicators and salt tolerance indicators; finally, one box of seedlings from each treatment group is left, and rehydrated and grown under ordinary white light or full-spectrum white light for 8 days to test their survival rate. All lighting times start at 8:00.

[0122] 2. Test results and analysis

[0123] Morphological indexes of rice seedlings after 10 days of salt stress

[0124] Table 7 Rice seedling morphological indexes of Example 3

[0125]

[0126] Determination of stress resistance-related indicators of rice seedlings, and calculation of seedling survival rate 8 days after rehydration

[0127] Table 8: Stress resistance related indicators and survival rate of rice seedlings in Example 3

[0128]

[0129]

[0130] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for light-regulated salt tolerance of rice seedlings, characterized in that: By adjusting the blue / red light ratio, the red / far-red light ratio or the blue / red / far-red light ratio, the rice seedlings are treated with light to improve the salt resistance of the rice seedlings.

2. The method according to claim 1, characterized in that The rice seedlings are cultivated under ordinary white light or full-spectrum white light for 20 days to the two-leaf and one-heart stage, and then transferred to an adjusted blue / red light ratio, red / far-red light ratio, or blue / red / far-red light ratio for light treatment.

3. The method according to claim 1 or 2, characterized in that: Set the blue / red light ratio to 0.10~5.00; Set the red / far-red light ratio to 0.10~5.

00.

4. The method according to claim 3, characterized in that Set the blue / red light ratio interval to [0.5, 4], preferably [0.50, 1.50); Set the red / far-red light ratio interval to [1, 4], preferably [1.00, 3.50); Or set the blue / red / far-red light ratio to [0.50,1.50):[0.50,1.50):[0.50,1.50), [1.50,3.50):[1.50,3.50):[0.50,1.50), [3.50,5.00):[3.50,5.00):[0.50,1.50), [0.50,1.50):[1.50,3.50):[0.50,1.50) or [3.50,5.00):[1.50,3.50):[0.50,1.50); Preferred: Set the blue / red / far-red light ratio to [1.50,3.50):[1.50,3.50):[0.50,1.50).

5. The method according to any one of claims 1 to 4, characterized in that: The wavelength of ordinary white light is 400-770nm; The full spectrum white light has a wavelength of 400 to 770 nm; The blue light wavelength range is 450-490nm; The red light wavelength range is 620-700nm; The far-infrared light has a wavelength of 700-770 nm.

6. The method according to any one of claims 1 to 4, characterized in that: The light intensity of the light source is 250-300 μmol m -2 s -1 The light source is fixed with 16 hours of illumination and 8 hours of darkness; the distance between the light source and the surface of the nutrient solution for rice seedlings is not greater than 0.40 m, and the illumination days are at least 10 days.

7. The method according to any one of claims 1 to 4, characterized in that: The temperature of the rice seedlings is controlled at 25±5°C, and the humidity is controlled at 75±5%; the CO2 concentration of the rice seedlings is controlled at 800-1100 PPM.

8. The method according to any one of claims 1 to 4, characterized in that: The NaCl salt concentration that rice can tolerate is 5‰.

9. The method according to any one of claims 1 to 4, characterized in that: The nutrient solution is changed every 3 to 5 days during the rice seedling stage.

10. The method according to any one of claims 1 to 4, characterized in that: The rice seedling variety is Nipponbare.

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