A cultivation regulation method for improving salt tolerance of rice at tillering stage and application

Abstract

This invention discloses a cultivation regulation method and application for improving salt tolerance during the tillering stage of rice, relating to the field of agricultural planting technology. The method includes: initiating salt stress treatment at the tillering stage (10-20 days after rice transplanting); on the day of salt stress treatment, applying exogenous regulatory substances according to the salt tolerance characteristics of the rice variety; the exogenous regulatory substances are selected from at least one of nitrogen fertilizer, γ-aminobutyric acid (GABA), and salicylic acid; the nitrogen fertilizer application rate is 80 kg N / ha to 120 kg N / ha, the GABA application concentration is 470 μmol / L to 530 μmol / L, and the salicylic acid application concentration is 320 μmol / L to 380 μmol / L. This method can be applied to improve salt tolerance during the tillering stage of rice, increase rice yield under salt stress, and / or improve rice quality. It is simple to operate, highly applicable, and provides efficient and practical technical support for stress-resistant, high-yield, and high-quality rice cultivation in saline-alkali land.

Description

Technical Field

[0001] This invention relates to the field of agricultural planting technology, specifically to a cultivation regulation method and application for improving salt tolerance during the tillering stage of rice. Background Technology

[0002] Soil salinization is a major abiotic stress globally, severely restricting efficient land use and sustainable agricultural development, and threatening global food security. Authoritative statistics show that the total area of ​​saline-alkali land globally reaches 1.381 billion hectares. Affected by factors such as climate warming, inappropriate irrigation, and improper fertilization, secondary salinization is intensifying, with the area expanding year by year, further reducing arable land. Clarifying the geographical and geological characteristics and distribution patterns of saline-alkali land is a core prerequisite for conducting research on saline-alkali land improvement and restoration, as well as the cultivation of stress-resistant crops, and is also a crucial entry point for addressing the food security crisis. As a populous country and a major food producer, my country considers food security a fundamental and strategic issue related to national welfare and people's livelihood. Saline-alkali land, as an important reserve of arable land, plays a vital strategic supporting role in ensuring food security and alleviating the shortage of arable land. my country's total saline-alkali land area is approximately 1.5 billion mu (equivalent to 99.13 million hectares), accounting for 10% of the world's total saline soil area, ranking third globally. A large area of ​​this land has agricultural development potential and enormous potential for increasing grain production. The distribution of saline-alkali land in my country exhibits a significant regional concentration, mainly concentrated in the Northeast, Northwest, North China inland areas, and eastern coastal regions. Among these, the salinization characteristics are typical and the distribution is concentrated in the coastal areas. Jiangsu Province, as the core distribution area of ​​coastal saline-alkali land, has approximately 5.7585 million mu of coastal saline-alkali land, accounting for one-quarter of the total area of ​​coastal saline-alkali land in China, and its natural siltation growth is nearly 20,000 mu per year.

[0003] Rice, as my country's largest grain crop and a staple food for more than half the world's population, is crucial for ensuring food security by improving its yield in saline-alkali environments. Rice is a moderately salt-sensitive crop, and salt stress is the core abiotic stress restricting its growth, development, and yield formation. Studies have confirmed that salt stress globally leads to an average yield reduction of 29.3% to 35% in rice. The damage caused by salt stress to rice varies significantly across its growth stages. The tillering stage, a critical period for yield capacity formation, is significantly affected by salt stress, resulting in a substantial decrease in the number of effective tillers and impacting canopy construction quality, leading to a sharp decline in yield. Furthermore, this damage is difficult to fully recover from through later management practices, severely hindering the achievement of high-quality and high-yield rice cultivation goals in saline-alkali lands. Current research focuses primarily on the physiological mechanisms of rice's response to salt stress, lacking research on cultivation control measures and mechanisms to alleviate rice salt stress. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a cultivation regulation method and application for improving salt tolerance during the rice tillering stage. This method involves applying nitrogen fertilizer and γ-rays during the rice tillering stage. Exogenous regulatory substances such as GABA or salicylic acid can be used to improve the salt tolerance of rice during the tillering stage, increase rice yield under salt stress, and improve rice quality.

[0005] Therefore, in a first aspect, the present invention provides a cultivation regulation method for improving salt tolerance during the tillering stage of rice, comprising: Salt stress treatment was initiated during the tillering stage, 10-20 days after rice transplanting. On the day of salt stress treatment, exogenous regulatory substances were applied according to the salt tolerance characteristics of the rice variety; these exogenous regulatory substances were selected from nitrogen fertilizer, γ-ray... At least one of aminobutyric acid and salicylic acid; The nitrogen fertilizer application rate is 80 kg N / ha to 120 kg N / ha, and the γ The application concentration of GABA is 470 μmol / L to 530 μmol / L, and the application concentration of salicylic acid is 320 μmol / L to 380 μmol / L.

[0006] Furthermore, the salt stress treatment includes: treating with a NaCl solution with a concentration of 80mM~120mM for 6~8 days; after the treatment, irrigation with normal water is carried out.

[0007] Furthermore, the nitrogen fertilizer is urea, and the nitrogen application rate is 90 kg N / ha to 110 kg N / ha; the γ The application concentration of GABA is 490 μmol / L to 510 μmol / L; the application concentration of salicylic acid is 340 μmol / L to 360 μmol / L.

[0008] Furthermore, the nitrogen fertilizer can also be applied as basal fertilizer one day before rice transplanting, as tillering fertilizer seven days after transplanting, and as panicle differentiation fertilizer during the young panicle stage; the total nitrogen application of the basal fertilizer, the tillering fertilizer, and the panicle differentiation fertilizer is 220 kg N / ha ~ 260 kg N / ha; the application ratio of the basal fertilizer, the tillering fertilizer, and the panicle differentiation fertilizer is (1.5 ~ 2.5): 1: (1.5 ~ 2.5).

[0009] Furthermore, the base fertilizer also includes phosphate fertilizer applied in the form of Ca(H2PO4)2 and potassium fertilizer applied in the form of KCl; the application rate of the phosphate fertilizer is 80 kg P / ha to 120 kg P / ha, and the application rate of the potassium fertilizer is 80 kg K / ha to 120 kg K / ha.

[0010] Furthermore, the rice varieties include salt-tolerant rice and salt-sensitive rice.

[0011] Furthermore, when the rice variety is a salt-tolerant rice, the nitrogen fertilizer is applied as an exogenous regulatory substance; when the rice variety is a salt-sensitive rice, the salicylic acid is applied as an exogenous regulatory substance.

[0012] Furthermore, the salt-tolerant rice is FL478 or Nanjing 11, and the salt-sensitive rice is Zhongnong 4 or Nipponbare.

[0013] A second aspect of the invention provides the application of the method in improving salt tolerance during the tillering stage of rice, increasing rice yield under salt stress, and / or improving rice quality.

[0014] Furthermore, the application includes at least one of the following: (1) Increase the number of tillers, plant height, leaf area index and biomass of rice; (2) Improve the photosynthetic pigment content and light energy utilization efficiency of rice; (3) Enhances the activity of antioxidant enzymes in rice and reduces the degree of membrane lipid peroxidation; (4) Promotes the accumulation of osmotic regulatory substances in rice; (5) Optimize rice root morphology and root vigor, and improve nitrogen absorption; (6) Increase the number of effective panicles, the number of grains per panicle, the seed setting rate and the thousand-grain weight of rice, thereby increasing the yield; (7) Improve the processing quality, appearance quality, taste quality and starch viscosity characteristics of rice under salt stress.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The cultivation regulation method for improving salt tolerance during the tillering stage of rice provided by this invention involves applying nitrogen fertilizer and γ-rays during the tillering stage of rice. Exogenous regulation with GABA and salicylic acid can synergistically alleviate salt stress damage from multiple dimensions, including photosynthetic efficiency, antioxidant system, osmotic regulation, root morphology, and nitrogen absorption and utilization, significantly improving salt tolerance during the tillering stage of rice. Simultaneously, precise adaptation can be achieved for salt-tolerant and salt-sensitive varieties; applying nitrogen fertilizer to salt-tolerant varieties and applying salicylic acid to salt-sensitive varieties can significantly restore effective tillering, seed setting rate, and yield. Gamma-aminobutyric acid (GABA) can be used as an auxiliary regulatory substance to further enhance the stress resistance effect. This method can also simultaneously improve rice processing, appearance, taste and starch viscosity characteristics, and achieve synergistic improvement of rice yield and quality under salt stress. It is easy to operate and has strong applicability, providing efficient and practical technical support for stress-resistant, high-yield and high-quality rice cultivation in saline-alkali land. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 The present invention provides an embodiment of the impact of exogenous regulation on the increase in rice yield and yield components under salt stress in 2024, wherein... Figure 1 A represents the number of ears per unit area. Figure 1 C represents the number of grains per ear. Figure 1 E represents the seed setting rate. Figure 1 G represents the weight of 1000 grains. Figure 1 I represents output; Figure 2 The present invention provides an embodiment of the impact of exogenous regulation on the increase in rice yield and yield components under salt stress in 2025, wherein... Figure 2 B represents the number of ears per unit area. Figure 2 D represents the number of grains per ear. Figure 2 F represents the seed setting rate. Figure 2 H represents the weight per thousand grains. Figure 2 J represents output; Figure 3 The effect of exogenous regulation on the increase of rice plant height under salt stress provided in the embodiments of the present invention, wherein, Figure 3 A represents the tillering stage. Figure 3 B represents the young spikelet stage. Figure 3 C represents the heading stage. Figure 3 D represents the maturity stage; Figure 4 The effect of exogenous regulation on the increase of rice tiller number under salt stress provided in this embodiment of the invention, wherein, Figure 4 A represents the tillering stage. Figure 4 B represents the young spikelet stage. Figure 4 C represents the heading stage; Figure 5 The effect of exogenous regulation on the increase of rice leaf area index under salt stress provided in this embodiment of the invention, wherein, Figure 5 A represents the tillering stage. Figure 5 B represents the young spikelet stage. Figure 5 C represents the heading stage; Figure 6 The effect of exogenous regulation on the increase of rice biomass under salt stress provided in the embodiments of the present invention, wherein, Figure 6 A represents the tillering stage. Figure 6 B represents the young spikelet stage. Figure 6 C represents the heading stage; Figure 7 The effect of exogenous regulation on the increase of rice biomass under salt stress provided in the embodiments of the present invention, wherein, Figure 7 A stands for chlorophyll a. Figure 7 B stands for chlorophyll b. Figure 7 C represents the total amount of chlorophyll. Figure 7 D represents carotenoids; Figure 8 The effect of exogenous regulation on the increase of light use efficiency in rice under salt stress, as provided in the embodiments of the present invention, wherein, Figure 8 A represents the amount of light radiation intercepted. Figure 8 B represents the amount of light interception. Figure 8 C represents light energy utilization rate; Figure 9 The embodiments of the present invention provide the amplification effect of rice antioxidant enzymes under salt stress and exogenous regulation, wherein, Figure 9 A represents SOD. Figure 9 B represents the rate of increase in SOD due to exogenous regulation. Figure 9 C stands for CAT. Figure 9 D represents the rate of increase in CAT due to exogenous regulation. Figure 9 E stands for POD. Figure 9 F represents the rate of increase in POD due to exogenous regulation; Figure 10 The embodiments of the present invention provide the reduction effect of MDA and exogenous regulation in rice under salt stress, wherein, Figure 10 A is MDA. Figure 10 B represents the rate of reduction in MDA due to exogenous regulation; Figure 11 The present invention provides an embodiment of the effect of salt stress on the amplification of osmotic regulators and exogenous regulation in rice, wherein... Figure 11 A is a soluble protein. Figure 11 B represents the rate of increase in soluble protein due to exogenous regulation. Figure 11 C is a soluble sugar. Figure 11 D represents the rate of increase in soluble sugars due to exogenous regulation. Figure 11 E stands for proline. Figure 11 F represents the rate of increase of proline due to exogenous regulation; Figure 12 The effect of exogenous regulation on the increase of total nitrogen uptake in rice under salt stress, as provided in the embodiments of the present invention, wherein, Figure 12 A represents the tillering stage. Figure 12 B represents the young spikelet stage. Figure 12 C represents the heading stage. Figure 12 D represents the maturity stage; Figure 13 The effect of exogenous regulation on the increase of rice root morphology under salt stress provided in the embodiments of the present invention, wherein, Figure 13 A represents the root-to-truncation weight. Figure 13 B is the total root length. Figure 13 C is the root surface area. Figure 13 D is the average root diameter; Figure 14 The effects of exogenous regulation on root sap flow and its amplification under salt stress in rice, as provided in this embodiment of the invention, are as follows: Figure 14 A represents root sap flow. Figure 14 B represents the amplification rate of root sap flow; Figure 15 The effect of exogenous regulation on the increase of oxidative capacity in rice roots under salt stress, as provided in the embodiments of the present invention, wherein, Figure 15 A represents the oxidizing power of the root system. Figure 15 B represents the rate of increase in root oxidative power; Figure 16 The effects of exogenous regulation on the increase of SOD, CAT, and POD in rice under salt stress, as provided in the embodiments of the present invention, are as follows: Figure 16 A represents SOD. Figure 16 B represents the growth rate of SOD. Figure 16 C stands for CAT. Figure 16 D represents the growth rate of CAT. Figure 16 E stands for POD. Figure 16 F represents the growth rate of POD; Figure 17 The effect of exogenous regulation on the increase of MDA in rice under salt stress provided in this embodiment of the invention, wherein, Figure 17 A is MDA. Figure 17 B represents the growth rate of MDA; Figure 18 The effect of exogenous regulation on the increase of soluble protein in rice roots under salt stress, as provided in this embodiment of the invention, is as follows: Figure 18 A is a soluble protein. Figure 18 B represents the amplification rate of soluble protein; Figure 19 The exogenous regulation provided in this embodiment of the invention has an effect on the enhancement of rice processing and appearance quality under salt stress, wherein... Figure 19 A represents the percentage of brown rice. Figure 19 B represents the rice milling rate. Figure 19 C represents the head rice yield. Figure 19 D represents the chalky grain ratio. Figure 19 E represents chalkiness; Figure 20 The effect of exogenous regulation on the enhancement of eating taste and nutritional quality of rice under salt stress, as provided in the embodiments of the present invention, wherein... Figure 20 A is amylose. Figure 20 B stands for albumin. Figure 20 C stands for globulin. Figure 20 D represents alcohol-soluble protein. Figure 20 E stands for glutenin; Figure 21The effect of exogenous regulation on the effect of salt stress on the starch viscosity properties (RVA profile) of rice provided in this embodiment of the invention, wherein, Figure 21 A represents the peak viscosity. Figure 21 B represents the viscosity of the hot paste. Figure 21 C is the breakdown value. Figure 21 D is the final viscosity. Figure 21 E is the response value. Figure 21 F represents the reduction value. Detailed Implementation

[0018] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0019] A first aspect of this invention provides a cultivation regulation method for improving salt tolerance during the tillering stage of rice, comprising: Salt stress treatment was applied during the tillering stage, 10 to 20 days after rice transplanting. On the day of salt stress treatment, exogenous regulatory substances were applied according to the salt tolerance characteristics of the rice variety; the exogenous regulatory substances were selected from nitrogen fertilizer, γ-ray... At least one of aminobutyric acid and salicylic acid; Preferably, salt stress treatment is performed during the tillering stage, 14 days after rice transplanting.

[0020] The nitrogen application rate for nitrogen fertilizer is 80 kg N / ha to 120 kg N / ha, γ The application concentration of GABA is 470 μmol / L to 530 μmol / L, and the application concentration of salicylic acid is 320 μmol / L to 380 μmol / L.

[0021] Preferably, salt stress treatment is performed during the tillering stage, 14 days after rice transplanting.

[0022] Specifically, nitrogen fertilizer, γ The application range of aminobutyric acid and salicylic acid was determined based on previous experimental screening. Too low an application rate has no effect on alleviating salt stress in rice or the effect is not obvious, while too high an application rate will aggravate the effect of salt stress, causing seedling burn and growth inhibition.

[0023] In some embodiments, salt stress treatment includes: treating with a NaCl solution with a concentration of 80mM to 120mM for 6 to 8 days; and then irrigating with normal water after the treatment is completed.

[0024] Preferably, the concentration of the NaCl solution is 100 mM, and the treatment time is 7 days.

[0025] In some embodiments, the nitrogen fertilizer is urea, and the nitrogen application rate is 90 kg N / ha to 110 kg N / ha; γ The application concentration of GABA is 490 μmol / L to 510 μmol / L; the application concentration of salicylic acid is 340 μmol / L to 360 μmol / L.

[0026] Preferably, the nitrogen fertilizer application rate is 100 kg N / ha; γ The application concentration of GABA is 500 μmol / L; the application concentration of salicylic acid is 350 μmol / L.

[0027] In some embodiments, nitrogen fertilizer may also be applied as basal fertilizer one day before rice transplanting, as tillering fertilizer seven days after transplanting, and as young panicle differentiation fertilizer during the young panicle stage; the total amount of nitrogen applied by basal fertilizer, tillering fertilizer and young panicle differentiation fertilizer is 220 kg N / ha ~ 260 kg N / ha, and the application ratio is (1.5 ~ 2.5): 1: (1.5 ~ 2.5).

[0028] Specifically, this application rate is set according to the actual situation of rice production. It scientifically matches the nitrogen requirements of rice in key growth stages, optimizes nitrogen fertilizer allocation, and thus lays the foundation for improving yield, nitrogen fertilizer utilization rate and rice quality.

[0029] A higher proportion of basal fertilizer (1.5~2.5): Applied before transplanting, it provides sufficient initial nitrogen nutrition for rice seedlings, promotes root development and early growth, lays the foundation for subsequent tillering, and avoids slow seedling establishment due to insufficient nutrition after transplanting. A tillering fertilizer proportion of 1 (as a baseline): Applied on the 7th day after transplanting, when rice enters the tillering stage, moderate nitrogen supply effectively promotes tillering, but avoids excessive nitrogen leading to too many ineffective tillers or excessive plant growth, thus maintaining a reasonable plant population structure and reducing disease risk. A higher proportion of young panicle differentiation fertilizer (1.5~2.5): Applied during the young panicle stage, this stage is crucial for panicle formation and grain development. Higher nitrogen levels support young panicle differentiation, increase the number of grains per panicle, seed setting rate, and thousand-grain weight, directly enhancing yield potential.

[0030] A total nitrogen application rate of 220 kg N / ha to 260 kg N / ha, within a reasonable range and combined with multiple applications, can reduce nitrogen loss (such as leaching or volatilization), improve utilization efficiency, and reduce the risk of environmental pollution. The ratio range (1.5 to 2.5) also allows for flexible adjustments based on soil fertility, variety, and climate, enhancing adaptability. This ratio, by precisely controlling the timing and amount of nitrogen supply, balances the growth needs of rice at different stages, contributing to high-yield, high-efficiency, and sustainable cultivation.

[0031] Preferably, the total nitrogen application rate is 240 kg N / ha; the application ratio of basal fertilizer, tillering fertilizer, and young spikelet differentiation fertilizer is 2:1:2.

[0032] In some embodiments, the base fertilizer also includes phosphate fertilizer applied in the form of Ca(H2PO4)2 and potassium fertilizer applied in the form of KCl; the application rate of phosphate fertilizer is 80 kg P / ha to 120 kg P / ha, and the application rate of potassium fertilizer is 80 kg K / ha to 120 kg K / ha.

[0033] Preferably, the phosphorus application rate of phosphate fertilizer is 100 kg P / ha, and the potassium application rate of potassium fertilizer is 100 kg K / ha.

[0034] In some embodiments, rice varieties include salt-tolerant rice and salt-sensitive rice.

[0035] In some embodiments, when the rice variety is salt-tolerant, nitrogen fertilizer is applied as an exogenous regulatory substance; when the rice variety is salt-sensitive, salicylic acid is applied as an exogenous regulatory substance, and γ-aminobutyric acid plays an auxiliary regulatory role in both types of varieties.

[0036] In some embodiments, the salt-tolerant rice is FL478 or Nanjing 11, and the salt-sensitive rice is Zhongnong 4 or Nipponbare.

[0037] A second aspect of the present invention provides the application of the above method in improving the salt tolerance of rice during the tillering stage, increasing rice yield under salt stress, and / or improving rice quality.

[0038] The above applications include at least one of the following: (1) Increase the number of tillers, plant height, leaf area index and biomass of rice; (2) Improve the photosynthetic pigment content and light energy utilization efficiency of rice; (3) Enhances the activity of antioxidant enzymes in rice and reduces the degree of membrane lipid peroxidation; (4) Promotes the accumulation of osmotic regulatory substances in rice; (5) Optimize rice root morphology and root vigor, and improve nitrogen absorption; (6) Increase the number of effective panicles, the number of grains per panicle, the seed setting rate and the thousand-grain weight of rice, thereby increasing the yield; (7) Improve the processing quality, appearance quality, taste quality and starch viscosity characteristics of rice under salt stress.

[0039] Example 1: A cultivation regulation method to improve salt tolerance during the tillering stage of rice. 1. Experimental Materials and Methods This experiment was conducted in 2024 and 2025 at the Jiangdu Experimental Base of the Institute of Agricultural Science and Technology Development (International Joint Laboratory) of Yangzhou University. A cement pond (4m × 3m × 1m) for salt treatment was constructed in the field at the Jiangdu Experimental Station. The pond contained topsoil backfilled from the field. The soil properties of the experimental site were as follows: organic matter 10.2 g·kg⁻¹ -1 Total nitrogen 1.2 g·kg -1 Available phosphorus 36.3 mg·kg -1 Available potassium 88.7 mg·kg -1 Rice varieties with different salt tolerance (2 salt-tolerant varieties and 2 salt-sensitive varieties) selected in the preliminary screening were selected as experimental materials for field trials. Specific materials are shown in Table 1 below. Sowing was conducted on May 25, 2024. Seedlings were raised in seedbeds and transplanted on June 24, with a seedling age of 30 days. The row spacing was 15cm × 30cm, and double-row transplanting was used. Each treatment was replicated three times in this experiment. Nitrogen fertilizer was urea, with a total nitrogen application of 240 kg N / ha, applied in a 2:1:2 ratio in three applications: basal fertilizer (1 day before transplanting), tillering fertilizer (7 days after transplanting), and panicle differentiation fertilizer. Phosphorus fertilizer (100 kg P / ha) and potassium fertilizer (100 kg K / ha) were applied once as basal fertilizer, respectively, using Ca(H2PO4)2 and KCl. Salt stress was applied according to the experimental design after transplanting. For the tillering stage treatment, salt stress began on day 14 post-transplanting with a 100 mM NaCl solution for 7 days. During the treatment period, nitrogen fertilizer (100 kg N / ha) and chemical regulators (γ-aminobutyric acid 500 μmol / L, salicylic acid 350 μmol / L) were applied, with each regulator treatment administered on the same day as the salt stress treatment. The blank control (no salt treatment and no regulator treatment) is represented by BL, the salt treatment by CK, the salt + nitrogen fertilizer treatment by S1, the salt + γ-aminobutyric acid treatment by S2, and the salt + salicylic acid treatment by S3. After the salt stress treatment ended, irrigation was switched to normal water, similar to the control group. Scientific and meticulous management was implemented, including weed control and timely prevention of pests, diseases, and weeds to minimize yield loss.

[0040] Table 1 Rice Variety Information

[0041] 2. Sampling and determination of relevant indicators 2.1 Growth Indicators After the salt treatment at the tillering stage, 12 representative plants with consistent growth were selected from each replicate of each treatment, with three replicates in total. Plant height and the number of tillers were measured, and the stems and leaves were separated. Leaf area was measured using a leaf area meter (LI-3100C AREA METER). The stems and leaves were weighed separately, and after blanching at 105°C for 30 minutes in an oven, they were dried at 85°C to constant weight, and finally weighed. Leaf area index (LAI) and crop growth rate (CGR) were subsequently statistically analyzed and calculated.

[0042] LAI(m) 2 m -2 = Total area of ​​green leaves / Area of ​​land occupied CGR (gd) -1 m -2 ) = (W a -W b ) / (t a -t b ) W a W b Biomass measured in two separate measurements; t a t b The time between the two measurements.

[0043] 2.2 Measurement of Light Interception and Utilization Efficiency The light interception rate (LI), light irradiance (IR), and light utilization efficiency (RUE) of various rice varieties were measured using a canopy meter (AccuPAR LP-80, Decagon Devices Inc., Pullman, WA, USA) at different growth stages of rice. Measurements were taken on sunny days from 11:00 AM to 1:00 PM. Three points were randomly selected horizontally and vertically from each plot for measurement. Readings were taken at points 5 cm above and below the water surface of the rice canopy, ensuring the meter was horizontal. Six measurements were taken for each plot. The light irradiance interception rate (LI), light irradiance interception (IR), and light utilization efficiency (RUE) were calculated.

[0044] LI (%) = (I a -I b ) / I a ×100 IR(MJ) = LI × I a RUE (g MJ) -1 =Biomass / IR I a Readings when the canopy is above the rice canopy (μmol m) -2 s -1 ); I b : The reading of the canopy meter at the bottom of the rice canopy (μmol m)-2 s -1 The average light radiation interception rate (AVE.LI%) for a specific growth period or time interval is the average of two consecutive measurements of LI%. Light interception amount is the cumulative total light interception amount (MJ / m³) for a specific growth period or stage. -2 ).

[0045] 2.3 Determination of photosynthetic pigments Five fresh leaves, fully expanded at the top, were randomly selected from each plot. After removing the veins, the leaves were frozen in liquid nitrogen and stored in an ultra-low temperature (-80°C) freezer. The chlorophyll content, antioxidant enzyme activity, and osmotic regulators were then measured.

[0046] The photosynthetic pigment content was determined by the ethanol-acetone mixed extraction method: 0.2g of the fully expanded uppermost leaf of rice was weighed and added to a 10mL centrifuge tube with 95% ethanol-acetone solution. The tube was placed in a 4°C refrigerator and soaked for 72h. After 72h, the mixture was stirred and the supernatant was measured at 665nm, 649nm and 470nm respectively.

[0047] 2.4 Antioxidants and Osmosis Regulators Superoxide dismutase (SOD) activity was determined using the nitroblue tetrazolium (NBT) reduction method: 0.2 g of fully expanded rice leaves were weighed, added to the extract, and ground in an ice bath to form a homogenate. The homogenate was then transferred to a centrifuge tube, centrifuged for 20 min, and the supernatant was collected as the enzyme solution. The enzyme solution was then mixed with methionine, nitroblue tetrazolium, ethylenediaminetetraacetic acid (EDTA), and riboflavin solution in the dark. After mixing, the mixture was exposed to light for 30 min to initiate the reaction. The reaction was then measured at 560 nm.

[0048] Peroxidase (POD) activity was determined using the guaiacol method: enzyme solution was taken, guaiacol reaction solution was added, and colorimetric analysis was performed at 470 nm using a time-based colorimetric method.

[0049] Catalase (CAT) activity was measured using the ultraviolet absorption method: enzyme solution was taken, hydrogen peroxide solution was added, and colorimetric analysis was performed at 240 nm using a time-dependent colorimetric method.

[0050] Malondialdehyde (MDA) content was determined using the thiobarbituric acid (TBA) colorimetric method: 0.2 g of the uppermost fully expanded leaf from rice was weighed, added to the extract, and ground in an ice bath to form a homogenate. The homogenate was then transferred to a centrifuge tube and centrifuged at room temperature for 20 min. The supernatant was collected as the enzyme solution. The enzyme solution was mixed with the thiobarbituric acid solution by shaking and reacted in a boiling water bath for 15 min. After the reaction, the mixture was rapidly cooled, and after cooling to room temperature, centrifuged for 10 min. The supernatant was then measured at 600 nm, 532 nm, and 450 nm.

[0051] Soluble protein content was determined using the Coomassie Brilliant Blue G-250 staining method: 0.2g of the uppermost fully expanded leaf from rice was weighed, added to the extract, and homogenized in an ice bath. The homogenate was then transferred to a centrifuge tube and centrifuged for 20 minutes. The supernatant was collected as the enzyme solution. The protein standard solution was prepared using bovine serum albumin. The enzyme solution was thoroughly mixed with the Coomassie Brilliant Blue solution and allowed to stand for 2 minutes before measurement at 595 nm.

[0052] Soluble sugar determination: Weigh 0.1g of sample into a centrifuge tube, add 80% ethanol, incubate at 80℃ for 30min, cool, centrifuge for 15min, filter, repeat the above operation three times, combine the filtrates, and dilute to volume to obtain the extract. Take 1mL of extract, 1mL of ultrapure water, and 4mL of anthrone solution, mix, incubate at boiling water for 15min, cool, and measure the absorbance at 620nm.

[0053] The proline content was determined using the acidic ninhydrin colorimetric method. An appropriate amount of plant sample was weighed, and extracted by grinding with 3% sulfosalicylic acid solution. The extraction was performed in a boiling water bath for 10 min. After cooling, the sample was filtered or centrifuged, and the supernatant was used as the test solution. An equal volume of glacial acetic acid and acidic ninhydrin colorimetric solution were added to the test solution, and the mixture was developed in a boiling water bath for 30 min. After cooling, toluene was added for complete extraction. After standing and separating the layers, the upper organic phase was taken. Using toluene as a blank control, the absorbance was measured at a wavelength of 520 nm. The proline concentration in the sample was calculated according to the proline standard curve, and the proline content was calculated using the formula. The results were expressed in μg·g⁻¹. -1 Fresh weight indicates.

[0054] 2.5 Determination of nitrogen absorption and utilization efficiency Nitrogen content was determined using a Kjeldahl nitrogen analyzer, and total nitrogen uptake (NUP) was calculated.

[0055] Nitrogen determination: Dry the collected sample at 85℃ to constant weight, pulverize it, and pass it through a 100-mesh sieve. Accurately weigh 0.5g of the dry sample and place it in a glass test tube. Add concentrated sulfuric acid and a catalyst (prepared with copper sulfate and potassium sulfate). React at 420℃ for 1.5h. After the reaction is complete, place the tube in a ventilated area to cool and allow the harmful gases to evaporate completely. After cooling, the ammonium nitrogen content (mg N / g) can be determined using a Kjeldahl nitrogen analyzer.

[0056] NUP (kg·ha) -1 = Nitrogen concentration in different parts of the plant × biomass.

[0057] 2.6 Measurement of Output and Output Components Yield determination: At maturity, a 1m sample was taken from the center of each replicate plot of each treatment. 2 After harvesting, the rice undergoes threshing, impurity removal, and sun drying. The weight of the grains is then measured to calculate the yield, which is then converted to the yield with a 14% moisture content.

[0058] Yield components: At maturity, 12 rice plants were taken from each replicate plot of each treatment. After measuring plant height and panicle number, the panicles were removed, threshed, and the grains were dried. After water selection and winnowing (FJ-1, China), full grains, semi-full grains, and shriveled grains were separated. Three replicates of full grains (30g), semi-full grains (15g), and shriveled grains (2g) were weighed, counted, dried, and weighed. Finally, the following indicators were calculated: number of grains per panicle (SP), number of panicles per unit area (PN), seed setting rate (SSR), thousand-grain weight (TGW), and yield (GY).

[0059] 2.7 Quality Measurement Take plump grains that have been naturally air-dried at maturity, and determine the rice quality indicators according to NY / T 83-2020 "Methods for Determination of Rice Quality": Processing quality: The brown rice rate, milled rice rate, and head rice rate were measured using a JNMJ-3 rice milling machine, repeated 3 times. Appearance quality: The chalky grain rate and chalkiness were determined using an SC-E type rice appearance quality tester, repeated 3 times. Taste and nutritional quality: Amylose content was determined by iodine colorimetric method; protein components (albumin, globulin, prolamin, glutenin) were determined by continuous extraction method, all on dry weight.

[0060] 3. Results Analysis 3.1 Effects of salt stress on the yield and yield components of different rice varieties V1-V4 represent different rice varieties: V1 is FL478, V2 is Nanjing 11, V3 is Zhongnong 4, and V4 is Nipponbare. BL-S3 represent different treatments: BL is the blank control, CK is the salt treatment, S1 is salt + nitrogen fertilizer, S2 is salt + γ-amino acid, and S3 is salt + salicylic acid. Different letters indicate significant differences among different treatments of the same variety (P<0.05). T and V represent different treatments and varieties, respectively. P < 0.001; P<0.01; P<0.05; ns, P>0.05; the same applies below.

[0061] Table 2. Effects of salt stress on yield and yield components of different rice varieties (2024)

[0062] Table 3. Effects of salt stress on yield and yield components of different rice varieties (2025)

[0063] Salt stress significantly inhibited the yield and yield components of different salt-tolerant rice varieties. P<0.001 (P<0.05, ns, P>0.05), and the inhibitory effect was consistent in the 2024 and 2025 trials.

[0064] (1) Output As shown in Tables 2 and 3, compared with the blank control (BL), the yield of all varieties decreased significantly under salt stress treatment (P<0.001), with the decrease ranging from 37.2% to 69.4%. Among them, V4 showed the largest decrease, with a decrease of 65.4% and 69.4% in 2024 and 2025, respectively. The decrease in yield of salt-tolerant varieties was smaller than that of salt-sensitive varieties.

[0065] Compared with salt stress treatment (CK), S1, S2, and S3 all alleviated the inhibitory effect of salt stress on yield to varying degrees. Figure 1 As shown, in 2024, S2 improved V1 by 20%, and S3 improved V2, V3, and V4 by 40.0%, 35.0%, and 122.2%, respectively. Figure 2 As shown, in 2025, S2 will improve by 19.0% over V1, S3 will improve by 32.3% over V2 and 45.7% over V3, and S1 will improve by 106.7% over V4.

[0066] (2) Number of ears per unit area As shown in Tables 2 and 3, compared with the blank control (BL), salt stress treatment significantly reduced the number of spikes per unit area for all varieties, with V4 showing the largest decrease, decreasing by 60.1% and 64.6% in 2024 and 2025, respectively, compared with BL. The decrease in salt-tolerant varieties was smaller than that in salt-sensitive varieties.

[0067] Compared with salt stress treatment (CK), S1, S2, and S3 all alleviated the inhibitory effect of salt stress on the number of ears per unit area to varying degrees. Figure 1 As shown, in 2024, S2 improved by 14.6% and 69.1% over V1 and V4, respectively. S3 improved by 20.2% and 49.4% over V2 and V3, respectively. Figure 2 As shown, in 2025, S2 will improve by 17.3% over V1, and S3 will improve by 22.3% and 47.9% over V2 and V3, respectively. S1 will improve by 76.1% over V4.

[0068] (3) Number of grains per ear As shown in Tables 2 and 3, compared with the blank control (BL), salt stress led to a significant decrease in the number of grains per ear, with V3 and V4 showing the largest decreases, decreasing by 80.5% and 64.2% respectively in 2024.

[0069] Compared with salt stress treatment (CK), S1, S2, and S3 all alleviated the inhibitory effect of salt stress on the number of grains per ear to varying degrees. Figure 1As shown, in 2024, S1 improved by 55.1% and 100% compared to V1 and V4, respectively. S3 improved by 79.3% and 257.5% compared to V2 and V3, respectively. Figure 2 As shown, in 2025, S1 will improve V1 and V4 by 94.4% and 46% respectively, and S3 will improve V2 and V3 by 75.9% and 140.0% respectively.

[0070] (4) Fruit setting rate As shown in Tables 2 and 3, compared with the blank control (BL), salt stress led to a significant decrease in fruit set rate, with V3 and V4 showing the largest decreases, decreasing by 70.2% and 56.6% respectively in 2025.

[0071] Compared with salt stress treatment (CK), S1, S2, and S3 all alleviated the inhibitory effect of salt stress on fruit setting rate to varying degrees. Figure 1 As shown, in 2024, S2 improved by 32.4% and 140.7% over V1 and V4, respectively. S1 improved by 61.8% over V2, and S3 improved by 98.5% over V3. Figure 2 As shown, in 2025, S2 will improve upon V1 and V4 by 24% and 102.3% respectively, S1 will improve upon V2 by 38.7%, and S3 will improve upon V3 by 153.8%.

[0072] (5) Thousand-grain weight As shown in Tables 2 and 3, compared with the blank control (BL), salt stress led to a significant decrease in thousand-grain weight, with V4 showing the largest decrease, decreasing by 18.5% in 2024.

[0073] Compared with salt stress treatment (CK), S1, S2, and S3 all alleviated the inhibitory effect of salt stress on thousand-grain weight to varying degrees. Figure 1 As shown, in 2024, S1 improved by 9.2% and 11.3% over V1 and V2, respectively. S3 improved by 15.5% over V3, and S2 improved by 14.6% over V4. Figure 2 As shown, in 2025, S1 will improve by 5% and 12.6% over V1 and V2, respectively. S3 will improve by 6.7% over V3, and S2 will improve by 10.8% over V4.

[0074] 3.2 Effects of salt stress on growth-related characteristics of different rice varieties 3.2.1 Effects of salt stress on plant height (pH) and tiller number (TN) of different rice varieties Table 4. Effects of salt stress on plant height of different rice varieties at different growth stages.

[0075] Table 5. Effects of salt stress on tiller number at different growth stages of different rice varieties.

[0076] (1) Plant height Table 4 shows that treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on rice plant height (PH) at the tillering stage, young panicle stage, heading stage, and maturity stage. (P<0.001).

[0077] Compared with the blank control (BL), the plant height of all rice varieties decreased significantly at the tillering, young panicle, heading, and maturity stages under salt stress treatment. The salt-sensitive varieties (V3 and V4) showed a greater decrease in plant height at each stage than the salt-tolerant varieties (V1 and V2). Specifically, at the tillering stage, V3 showed the largest decrease (27.7%), while V2 showed the smallest decrease (17.7%). At the young panicle stage, V3 showed the largest decrease (19.3%), while at the heading stage, V3 still showed the largest decrease (19.3%), and V2 showed the smallest decrease (13.5%). At maturity, V4 showed the largest decrease (21.0%).

[0078] Compared with salt stress treatment (CK), the three regulatory treatments S1, S2, and S3 effectively alleviated the inhibitory effect of salt stress and significantly increased plant height in all varieties at the tillering, young panicle, heading, and maturity stages. At the tillering stage, S1 was more effective than S2 and S3 in increasing V1 height, with an increase of 25.1%. The differences in the increases in V2 height among S1, S2, and S3 were not significant, at 13.8%, 9.7%, and 13%, respectively. The differences in the increases in V3 height among S1, S2, and S3 were also not significant, at 24.6%, 24.3%, and 25.1%, respectively. S3 was more effective than S1 and S2 in increasing V4 height, with an increase of 26.8%. At the young panicle stage, S1 was more effective than S2 and S3 in increasing V1 height, with an increase of 16.8%. The differences in the increases in V2 height among S1, S2, and S3 were not significant, at 14.3%, 12.2%, and 16%, respectively. S3 was more effective than S1 in increasing V3 and V4 height. S1 and S2 showed increases of 21.5% and 12.8%, respectively. During the heading stage, the effects of S1, S2, and S3 on V1 improvement were not significantly different, at 9.2%, 9.5%, and 6.6%, respectively. S1 was more effective at improving V2 than S2 and S3, with an increase of 10.1%. S2 was more effective at improving V3 and V4 than S1 and S3, with increases of 13.1% and 15.5%, respectively. At maturity, S1 was more effective at improving V1 and V2 than S2 and S3, with increases of 12% and 16.5%, respectively. S3 was more effective at improving V3 than S1 and S2, with an increase of 6.5%. S2 was more effective at improving V4 than S1 and S3, with an increase of 15.1%.

[0079] like Figure 3As shown, overall, the increase in plant height for each rice variety from the three exogenous regulation methods decreased with the growth stage. For salt-tolerant varieties V1 and V2:S1, the effect of increasing plant height was more stable at most growth stages. For salt-sensitive varieties V3 and V4:S3, the increase in plant height was more prominent at the young panicle stage, heading stage, and maturity stage, and the effect of alleviating salt stress was better. Overall, S3 performed better among salt-sensitive varieties, while S1 was more stable among salt-tolerant varieties, and S2 had a relatively weaker effect.

[0080] (2) Number of tillers Table 5 shows that the treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on the number of rice tillers (TN) at the tillering stage, young panicle stage, and heading stage. (P<0.001).

[0081] Compared with the blank control (BL), the number of tillers in all rice varieties decreased significantly at the tillering, young panicle, heading, and maturity stages under salt stress treatment. The salt-sensitive varieties (V3 and V4) showed a greater decrease in tiller number at each stage than the salt-tolerant varieties (V1 and V2). Specifically, at the tillering stage, V3 showed the largest decrease (66.7%), while V1 showed the smallest decrease (52.0%). At the young panicle stage, V3 showed the largest decrease (62.5%), while at the heading stage, V4 still showed the largest decrease (62.7%), and V2 showed the smallest decrease (40.2%).

[0082] Compared with salt stress treatment (CK), the three regulatory treatments S1, S2 and S3 can effectively alleviate the inhibitory effect of salt stress and significantly increase the number of tillers in each variety during the tillering stage, young spikelet stage and heading stage. During the tillering stage, S1 showed a better effect on improving V1 and V2 than S2 and S3, with increases of 16.7% and 19.8% respectively. S3 showed a better effect on improving V3 and V4 than S1 and S2, with increases of 69.3% and 24.7% respectively. During the young panicle stage, S1 showed a better effect on improving V1 than S2 and S3, with an increase of 39.5%. S2 showed a better effect on improving V2 and V4 than S1 and S3, with increases of 38.3% and 74.2% respectively. The improvement effects of S1, S2, and S3 on V3 were not significantly different, all showing significant increases. During the heading stage, S1 showed a better effect on improving V1 and V3 than S2 and S3, with increases of 90.1% and 93.8% respectively. S2 showed a better effect on improving V2 and V4 than S1 and S3, with increases of 22.3% and 77.9% respectively.

[0083] like Figure 4 As shown, overall, for salt-tolerant varieties V1 and V2, S1 showed the most significant tillering improvement effect, significantly better than S2, S3, and CK. For salt-sensitive varieties V3 and V4, S2 showed the most significant tillering improvement effect, significantly better than S1, S3, and CK. Overall, the regulatory effects of S1 and S2 were significantly better than S3 and CK, with S1 being more suitable for salt-tolerant varieties and S2 being more suitable for salt-sensitive varieties.

[0084] 3.2.2 Effects of salt stress on leaf area index of different rice varieties Table 6. Effects of salt stress on leaf area index at different growth stages of different rice varieties.

[0085] Table 6 shows that the treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on the leaf area index (LAI) of rice at the tillering stage, young panicle stage, and heading stage. (P<0.001).

[0086] Compared with the blank control (BL), salt stress significantly reduced the leaf area index of all rice varieties at the tillering, young panicle, and heading stages, with the reduction in salt-sensitive varieties (V3 and V4) generally exceeding that of salt-tolerant varieties (V1 and V2). Specifically, at the tillering stage, V4 showed the largest reduction (64.4%), while V1 showed the smallest (55.4%); at the young panicle stage, V4 showed the largest reduction (72.3%), while V2 showed the smallest (47.2%); and at the heading stage, V3 showed the largest reduction (69.2%).

[0087] Compared with salt stress treatment (CK), the three regulatory treatments S1, S2 and S3 can effectively alleviate the inhibitory effect of salt stress and significantly improve the leaf area index of each variety during the tillering stage, young spikelet stage and heading stage. During the tillering stage, S2 was more effective than S1 and S3 in improving V1 and V4, with increases of 88.4% and 62.3%, respectively. S1 was more effective than S2 and S3 in improving V2, with an increase of 62%. The improvement effects of S1, S2, and S3 on V3 were not significantly different, with increases of 81.8%, 85.6%, and 88.6%, respectively. During the young spikelet stage, S2 was more effective than S1 and S3 in improving V1 and V3, with increases of 62.5% and 97.2%, respectively. S1 was more effective than S2 and S3 in improving V2, with an increase of 50.1%. The improvement effects of S1, S2, and S3 on V4 were not significantly different, with increases of 84.6%, 72.9%, and 77.9%, respectively. During the heading stage, S1 was more effective than S2 and S3 in improving V1 and V2, with increases of 67.7% and 60.9%, respectively. S2 was more effective than S1 and S3 in improving V3 and V4, with increases of 91.6% and 119.7%, respectively.

[0088] like Figure 5 As shown, a comprehensive comparison of salt-tolerant varieties (V1, V2) reveals that S1 exhibits the most significant improvement in tillering and heading stages, outperforming S2 and S3. For salt-sensitive varieties (V3, V4), S2 demonstrates the most significant improvement in young panicle and heading stages, outperforming S1 and S3. Overall regulatory effect: Both S1 and S2 show significantly better regulatory effects than S3, with S1 being more suitable for salt-tolerant varieties and S2 more suitable for salt-sensitive varieties.

[0089] 3.2.3 Effects of salt stress on aquatic biomass of different species Table 7. Effects of salt stress on biomass of different rice varieties at different growth stages.

[0090] Table 7 shows that the treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on rice biomass (BIO) at the tillering stage, young panicle stage, heading stage, and maturity stage. (P<0.001).

[0091] Compared with the blank control (BL), salt stress significantly reduced biomass in all rice varieties at the tillering, young panicle, and heading stages, with salt-sensitive varieties (V3 and V4) showing a greater overall reduction than salt-tolerant varieties (V1 and V2). Specifically, at the tillering stage, V3 showed the largest reduction (55.3%), while V1 showed the smallest (46.2%); at the young panicle stage, V4 showed the largest reduction (64.7%), while V2 showed the smallest (49.1%); at the heading stage, V4 showed the largest reduction (68.5%), while V2 showed the smallest (51.2%); and at maturity, V4 showed the largest reduction (74.9%), while V1 showed the smallest (61.4%).

[0092] Compared with the salt stress treatment (CK), the three regulatory treatments S1, S2, and S3 effectively alleviated the inhibitory effect of salt stress and significantly increased the biomass of each variety at the tillering, young panicle, and heading stages. At the tillering stage, the effects of S1, S2, and S3 on V1 were not significantly different, with increases of 59.0%, 61.5%, and 46.2%, respectively. S3 was more effective than S1 and S2 in increasing V2, V3, and V4, with increases of 40.8%, 101.3%, and 32.1%, respectively. At the young panicle stage, S1 was more effective than S2 and S3 in increasing V1, V3, and V4, with increases of 37.7%, 56%, and 99.7%, respectively. The effects of S1, S2, and S3 on V2 were not significantly different, with increases of 22.4%, 20.2%, and 23.1%, respectively. At the heading stage, S1… The improvement effect on V1 is better than that on S2 and S3, with an increase of 44.7%. The improvement effect of S3 on V2 is better than that on S1 and S2, with an increase of 32.6%. The improvement effect of S2 on V3 and V4 is better than that on S1 and S3, with increases of 24.1% and 61% respectively. In the mature stage, the improvement effect of S1 on V1 and V4 is better than that on S2 and S3, with increases of 47.7% and 127% respectively. The improvement effects of S1, S2 and S3 on V2 are not significantly different, with increases of 50.3%, 50.3% and 57.4% respectively. The improvement effect of S2 on V3 is better than that on S1 and S3, with an increase of 64.1%.

[0093] like Figure 6As shown, in a comprehensive comparison, S1 showed the best effect among the three control measures, while the overall effects of S2 and S3 were similar. S1 performed best in the young spikelet stage, heading stage, and maturity stage, especially on the salt-sensitive variety V4. S2 performed best at the maturity stage of the salt-sensitive variety V3. S3 showed significant performance at the tillering stage and also significantly improved the maturity stage of the salt-tolerant variety V2.

[0094] 3.3 Effects of salt stress on light energy utilization of different rice varieties 3.3.1 Effects of salt stress on photosynthetic pigments in different varieties Table 8. Effects of salt stress on photosynthetic pigments at the tillering stage of different rice varieties.

[0095] Table 8 shows that treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on photosynthetic pigments in rice during the tillering stage. (P<0.001).

[0096] Compared with the blank control (BL), salt stress significantly reduced chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in all rice varieties, with the reduction in salt-sensitive varieties (V3, V4) generally exceeding that in salt-tolerant varieties (V1, V2). Specifically, for chlorophyll a, V3 showed the largest reduction (29.6%), while V2 showed the smallest (22.1%); for chlorophyll b, V4 showed the largest reduction (54.2%), while V2 showed the smallest (28.1%); for total chlorophyll, V3 showed the largest reduction (35.8%), while V2 showed the smallest (23.8%); and for carotenoids, V3 showed the largest reduction (48.8%), while V1 showed the smallest (31.9%).

[0097] Compared with salt stress treatment (CK), the three regulatory treatments S1, S2, and S3 effectively alleviated the inhibitory effect of salt stress and significantly increased chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in all varieties during the tillering stage. For chlorophyll a, S1 was more effective than S2 and S3 in increasing V1, V3, and V4, with increases of 27.2%, 14.3%, and 23.6%, respectively; S2 was more effective than S1 and S3 in increasing V2, with an increase of 14.1%. For chlorophyll b, S1 was more effective than S2 and S3 in increasing V1 and V4, with increases of 56.8% and 89.9%, respectively; S3 was more effective than S1 and S2 in increasing V2 and V3, with increases of 30.1% and 59.2%, respectively. Regarding total chlorophyll, S1… For V1 and V4, S2 showed better improvement than S3, with increases of 34.4% and 37.3% respectively. For V2, S2 showed better improvement than S1 and S3, with an increase of 17.2%. For V3, S3 showed better improvement than S1 and S2, with an increase of 23.9%. For carotenoids, S2 showed better improvement than S1 and S3, with increases of 44.8% and 33.3% respectively. For V3 and V4, S1 showed better improvement than S2 and S3, with increases of 80.9% and 82.1% respectively.

[0098] like Figure 7 As shown in the above, under salt stress treatments, S1, S2, and S3 all significantly increased photosynthetic pigments during the rice tillering stage, thereby alleviating the inhibition of photosynthesis by salt stress. Among them, S1 had the best overall effect, especially in increasing carotenoids and chlorophyll b, followed by S2, while S3 had a relatively weaker effect.

[0099] 3.3.2 Effects of salt stress on the light energy utilization efficiency of different varieties Table 9. Effects of salt stress on light use efficiency during the tillering stage of different rice varieties.

[0100] Table 9 shows that treatment (T), variety (V), and their interaction effects (T×V) all had extremely significant effects on the light energy utilization efficiency of rice during the tillering stage. (P<0.001).

[0101] Compared with the blank control (BL), salt stress significantly inhibited the light use efficiency (LI, IR, RUE) at the tillering stage in rice varieties with different salt tolerance. The reduction was generally greater in salt-sensitive varieties (V3, V4) than in salt-tolerant varieties (V1, V2). Specifically, for LI, V4 showed the largest reduction (55.7%), while V1 showed the smallest (25.4%); for IR, V4 showed the largest reduction (62.1%), while V2 showed the smallest (41.8%); and for RUE, V3 showed the largest reduction (71.6%), while V1 showed the smallest (42.8%).

[0102] Applying different regulatory measures under salt stress significantly alleviated the decrease in light energy utilization efficiency (LEE). The LEE indices of all varieties were significantly improved under S1, S2, and S3 treatments. For LI, S1 was more effective than S2 and S3 in improving V1 and V4, with increases of 33% and 86.5%, respectively. The improvement effects of S1, S2, and S3 on V2 were not significantly different, with increases of 30.5%, 32.6%, and 28.7%, respectively. S1 and S3 were more effective than S2 in improving V3, with increases of 63.1% for both. For IR, S1 was more effective than S2 and S3 in improving V1, V2, V3, and V4, with increases of 57.0%, 66.7%, 75.8%, and 82.8%, respectively. For RUE, S3 was more effective than S1 and S2 in improving V1 and V4, with increases of 42.1% and 83.7%, respectively. S1 was more effective than S2 and S3 in improving V2 and V3, with increases of 92.2% and 87.2%, respectively.

[0103] like Figure 8 As shown in the comparison, for salt-tolerant varieties (V1, V2), S1 and S3 have better overall effects and can be selected according to specific indicator requirements. For salt-sensitive varieties (V3, V4), S1 (nitrogen fertilizer) has the most obvious advantages, effectively alleviating the inhibition of light utilization by salt stress, and is the better choice.

[0104] 3.4 Effects of salt stress on antioxidant enzymes in different rice varieties 3.4.1 Effects of salt stress on SOD, CAT, and POD levels in leaves of different varieties like Figure 9 As shown, compared with the blank control, salt stress significantly increased the activities of SOD, CAT, and POD during the tillering stage of different salt-tolerant rice varieties, indicating that rice actively activated its antioxidant defense system to scavenge reactive oxygen species under salt stress. Furthermore, the enzyme activity increases in salt-tolerant varieties (V1 and V2) were generally higher than those in salt-sensitive varieties (V3 and V4). V2 showed the largest increases in SOD and POD activities, at 61.6% and 25.1%, respectively. V1 showed the largest increase in CAT activity, at 39.8%. V3 showed the smallest increases in SOD, CAT, and POD activities, at 21.3%, 7.5%, and 0.04%, respectively.

[0105] Applying different regulatory measures under salt stress further enhanced the activity of antioxidant enzymes. The activities of SOD, CAT, and POD in all varieties were significantly higher than those in the control (CK) under S1, S2, and S3 treatments. For SOD, S3 showed a better effect on increasing V1 than S1 and S2, with an increase of 99.2%; S2 showed a better effect on increasing V2 and V4 than S1 and S3, with increases of 29.8% and 74%, respectively; and S1 showed a better effect on increasing V3 than S2 and S3, with an increase of 34.5%. For CAT, S1 showed a more significant effect on increasing V1 and V4, with increases of 18.1% and 23.4%, respectively; and S2 showed a better effect on increasing V2 and V3 than S1 and S3, with increases of 42.5% and 23.8%, respectively. For POD, S1 showed a better effect on increasing V1, V3, and V4 than S2 and S3, with increases of 79.1%, 69.8%, and 66.9%, respectively; and S2 showed a better effect on increasing V2 than S1 and S3, with an increase of 129.7%.

[0106] In summary, for salt-sensitive varieties (V3, V4), S2 has a significant advantage in enhancing POD activity; for salt-tolerant varieties (V1, V2), S1 shows more stable performance in enhancing SOD and CAT activity and can more effectively enhance antioxidant capacity.

[0107] 3.4.3 Effects of salt stress on different varieties of MDA like Figure 10 As shown, compared with the blank control, salt stress significantly increased the MDA content during the tillering stage of different salt-tolerant rice varieties, indicating that salt stress leads to cell membrane lipid peroxidation and causes membrane damage. Moreover, the increase in MDA in salt-sensitive varieties (V3, V4) was generally higher than that in salt-tolerant varieties (V1, V2), with V4 showing the largest increase (317.0%) and V2 showing the smallest increase (171.0%).

[0108] Applying different regulatory measures under salt stress significantly reduced MDA content. The MDA content of all varieties under S1, S2, and S3 treatments was significantly lower than that under the control (CK). The reduction effects of S1, S2, and S3 on V1 were not significantly different, at 34%, 39%, and 33.7%, respectively. S3 was more effective than S1 and S2 in reducing V2 and V3, with reductions of 57.6% and 61.7%, respectively. S1 was more effective than S2 and S3 in reducing V4, with a reduction of 71.7%.

[0109] In summary, for salt-tolerant varieties (V1, V2), S3 is more effective in reducing membrane lipid peroxidation; for salt-sensitive varieties (V3, V4), S1 has the most obvious advantage, effectively alleviating membrane damage caused by salt stress and protecting cell membrane integrity.

[0110] 3.5 Effects of salt stress on osmotic regulators in different rice varieties like Figure 11As shown, compared with the blank control, salt stress significantly increased the content of soluble protein, soluble sugar, and proline at the tillering stage in different salt-tolerant rice varieties, indicating that rice maintains cell osmotic pressure and enhances stress resistance by accumulating osmotic regulatory substances. Furthermore, the increase in substance accumulation in salt-tolerant varieties (V1, V2) was generally higher than that in salt-sensitive varieties (V3, V4). Specifically, for soluble protein, V2 showed the largest increase (34.9%), while V3 showed the smallest (5.6%); for soluble sugar, V1 showed the largest increase (17.4%), while V4 showed the smallest (1.2%); and for proline, V1 showed the largest increase (93.5%), while V4 showed the smallest (3.2%).

[0111] Applying different regulatory measures under salt stress can further promote the accumulation of osmotic regulatory substances. The contents of soluble protein, soluble sugar and proline in each variety under S1, S2 and S3 treatments are significantly higher than those in CK. For soluble proteins, S3 showed better enhancement of V1 and V2 than S1 and S2, with increases of 39.7% and 14.2%, respectively; S2 showed better enhancement of V3 than S1 and S3, with an increase of 14.4%; and S1 showed better enhancement of V4 than S2 and S3, with an increase of 9.7%. For soluble sugars, S2 showed better enhancement of V1 than S1 and S3, with an increase of 17.8%; S3 showed better enhancement of V2 than S1 and S2, with an increase of 6.5%; and S1 showed better enhancement of V3 and V4 than S2 and S3, with increases of 65.5% and 7.8%, respectively. For proline, S1 showed better enhancement of V1 than S2 and S3, with an increase of 42.4%; and S3 showed better enhancement of V2 than S2 and S3, with an increase of 84.1%. S2 improves V3 better than S1 and S3, with an increase of 25.7%. The improvement effects of S1, S2 and S3 on V4 are not significantly different, with increases of 69.3%, 74.4% and 69% respectively.

[0112] In summary, for salt-sensitive varieties (V3, V4), S2 is the most effective in promoting proline accumulation; for salt-tolerant varieties (V1, V2), S1 and S3 each have their advantages in increasing the content of soluble protein, soluble sugar and proline.

[0113] 3.6 Effects of salt stress on nitrogen uptake in different rice varieties Table 10 Effects of salt stress on total nitrogen uptake at different growth stages of different rice varieties

[0114] Table 10 shows that treatment (T), variety (V), and their interaction effects (T×V) have a highly significant impact on the total nitrogen uptake of rice during the tillering stage. P < 0.001; (P<0.05).

[0115] Compared with the control group, salt stress significantly inhibited the total nitrogen uptake of different salt-tolerant rice varieties at all stages. The reduction was generally greater in salt-sensitive varieties (V3 and V4) than in salt-tolerant varieties (V1 and V2). At the tillering stage, V4 showed the largest reduction (83.4%), while V1 showed the smallest (49.9%). At the panicle stage, V3 showed the largest reduction (84.2%), while V1 showed the smallest (64.7%). At the heading stage, V4 showed the largest reduction (81.7%), while V1 showed the smallest (71.6%). At maturity, V4 showed the largest reduction (86.8%), while V2 showed the smallest (71.1%).

[0116] Applying different regulatory measures under salt stress significantly alleviated the decrease in total nitrogen uptake. Under S1, S2, and S3 treatments, the total nitrogen uptake of all varieties was significantly increased. During the tillering stage, S3 showed a better effect on increasing V1, V2, V3, and V4 than S1 and S2, with increases of 63.2%, 153.8%, 210%, and 162.5%, respectively. During the young panicle stage, S1 showed a better effect on increasing V1 and V3 than S2 and S3, with increases of 61.2% and 148.2%, respectively. S3 showed a better effect on increasing V2 and V4 than S1 and S2, with increases of 105.2% and 152.9%, respectively. During the heading stage, S1 showed a better effect on increasing V1 than S2. S2 and S3 showed an increase of 91.3%. S3 was more effective than S1 and S2 in improving V2, V3, and V4, with increases of 83.8%, 60.4%, and 186%, respectively. In the mature stage, S1 was more effective than S2 and S3 in improving V1, V3, and V4, with increases of 82.1%, 122.4%, and 168.4%, respectively. The improvement effects of S1, S3, and S2 on V2 were not significantly different, with increases of 48.9%, 57.2%, and 46.6%, respectively.

[0117] like Figure 12 As shown, overall, S1 has the most significant enhancing effect on salt-sensitive varieties V3 and V4, with stable and broad-spectrum effects; S2 has a more gradual and balanced regulatory effect on salt-tolerant varieties V1 and V2; S3 has a prominent enhancing effect on V2 and V3, with excellent overall repair capabilities.

[0118] 3.7 Effects of salt stress on root growth and physiological characteristics of different rice varieties 3.7.1 Effects of salt stress on root growth of different rice varieties Table 11 Effects of salt stress on root morphology of different rice varieties

[0119] Salt stress significantly inhibited root morphological parameters (root dry weight, total root length, root surface area, and average root diameter) at the tillering stage in rice varieties with different salt tolerance. P<0.001 (P<0.05).

[0120] (1) Root-to-stem weight Table 11 shows that, compared with the control group, the root dry weight of all rice varieties under salt stress was significantly lower than that of the control group, and the inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the root dry weight reduction was 60.2% for salt-tolerant variety V1 and 75.4% for V2 under the control group; while the root dry weight reduction was 80% for salt-sensitive varieties V3 and 80.2% for V4 under the control group. The root dry weight stability of salt-tolerant varieties (V1 and V2) was significantly better than that of salt-sensitive varieties (V3 and V4).

[0121] like Figure 13 As shown, compared with salt stress treatment, applying different regulatory measures can significantly alleviate the decrease in root dry weight. The root dry weight of each variety under S1, S2, and S3 treatments is significantly higher than that under CK treatment. S2 increases V1 and V3 by 66.7% and 184.2%, respectively, while S3 increases V2 and V4 by 161.8% and 105.3%, respectively.

[0122] (2) Total root length Table 11 shows that, compared with the control group, the total root length of all rice varieties under salt stress was significantly lower than that of the control group, and this inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the total root length of salt-tolerant variety V1 decreased by 39% under the control group (CK), and that of V2 decreased by 37.6%. In contrast, the total root length of salt-sensitive varieties V3 decreased by 48.1% and that of V4 decreased by 62.9% under the control group (CK). The stability of total root length in salt-tolerant varieties (V1 and V2) was significantly better than that in salt-sensitive varieties (V3 and V4).

[0123] like Figure 13 As shown, compared with salt stress treatment, applying different regulatory measures can significantly alleviate the decrease in total root length. The total root length of each variety under S1, S2, and S3 treatments is significantly higher than that under CK treatment. S2 increases V1 by 61.3%, S3 increases V2 by 52%, and S1 increases V3 and V4 by 38.7% and 123.8%, respectively.

[0124] (3) Root surface area Table 11 shows that, compared with the control group, the root surface area of ​​all rice varieties under salt stress was significantly lower than that of the control group, and this inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the root surface area of ​​salt-tolerant variety V1 decreased by 55.6% under the control group (CK), and that of V2 decreased by 43.3%. In contrast, the root surface area of ​​salt-sensitive varieties V3 decreased by 61.9% and that of V4 decreased by 61.7% under the control group (CK). The root surface area stability of salt-tolerant varieties (V1 and V2) was significantly better than that of salt-sensitive varieties (V3 and V4).

[0125] like Figure 13As shown, compared with salt stress treatment, applying different regulatory measures can significantly alleviate the reduction in root surface area. The root surface area of ​​each variety under S1, S2, and S3 treatments is significantly higher than that under CK treatment. S2 increases V1 and V3 by 70% and 49.8%, respectively, while S3 increases V2 and V4 by 73.1% and 36.7%, respectively.

[0126] (4) Average root diameter Table 11 shows that, compared with the control group, the average root diameter of all rice varieties under salt stress was significantly lower than that of the control group, and the inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the average root diameter of salt-tolerant variety V1 decreased by 40.5% under the control group (CK), and that of V2 decreased by 48.7%. In contrast, the average root diameter of salt-sensitive varieties V3 decreased by 67.5% under the control group (CK), and that of V4 decreased by 65.3%. The average root diameter stability of salt-tolerant varieties (V1 and V2) was significantly better than that of salt-sensitive varieties (V3 and V4).

[0127] like Figure 13 As shown, compared with salt stress treatment, applying different regulatory measures can significantly alleviate the decrease in average root diameter. The average root diameter of each variety under S1, S2, and S3 treatments is significantly higher than that under CK treatment. S3 is more effective than S1 and S2 in improving the root diameter of V1, V2, V3, and V4, increasing it by 44.2%, 72.7%, 177.0%, and 73.8%, respectively.

[0128] 3.7.2 Effects of salt stress on root physiology of different rice varieties (1) Root sap flow like Figure 14 As shown, salt stress significantly inhibits the root sap flow intensity during the tillering stage of different salt-tolerant rice varieties.

[0129] Compared with the control group, root sap flow in all rice varieties under salt stress was significantly lower than that in the control group, and this inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the root sap flow reduction was 68.5% for salt-tolerant variety V1 and 65.9% for V2 under the control group; while the root sap flow reduction was 79.1% for salt-sensitive variety V3 and 72.3% for V4 under the control group. The root sap flow stability of salt-tolerant varieties (V1 and V2) was significantly better than that of salt-sensitive varieties (V3 and V4).

[0130] Compared with salt stress treatment, the application of different regulatory measures can significantly alleviate the reduction in root sap flow. The root sap flow of all varieties under the S1, S2, and S3 treatments is significantly higher than that under the CK treatment. S3 increases V1 and V2 by 151.1% and 104.5%, respectively, S1 increases V1 by 115.3%, and S2 increases V4 by 144.2%.

[0131] (2) Root oxidative power like Figure 15 As shown, salt stress significantly inhibits the root sap flow intensity during the tillering stage of different salt-tolerant rice varieties.

[0132] Compared with the control group, the root oxidative capacity of all rice varieties under salt stress was significantly lower than that of the control, and this inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the root oxidative capacity of salt-tolerant variety V1 decreased by 37.8% under the control group (CK), and that of V2 decreased by 33.3%. In contrast, the root oxidative capacity of salt-sensitive varieties V3 decreased by 41.3% and that of V4 decreased by 64.6% under the control group (CK). The root oxidative capacity stability of salt-tolerant varieties (V1 and V2) was significantly better than that of salt-sensitive varieties (V3 and V4).

[0133] Compared with salt stress treatment, the application of different regulatory measures can significantly alleviate the decrease in root oxidative capacity. The root oxidative capacity of all varieties under S1, S2, and S3 treatments is significantly higher than that under CK treatment. S1 increases V1 by 30.8%, and S3 is more effective than S1 and S2 in increasing V2, V3, and V4 by 39.2%, 49.6%, and 120.6%, respectively.

[0134] (3) Root system SOD, CAT, POD like Figure 16 As shown, salt stress significantly induced the activity of root antioxidant enzymes (SOD, CAT, POD) during the tillering stage in rice varieties with different salt tolerance.

[0135] Compared with the control group, the activities of all three enzymes in each variety under salt stress treatment were significantly higher than those under the control group, and this induction effect showed obvious differences in salt tolerance among different varieties. Specifically, in salt-tolerant variety V1, the activities of SOD, CAT, and POD increased by 80%, 133.3%, and 24.4%, respectively, under CK treatment compared to BL; in V2, the activities of SOD, CAT, and POD increased by 87.6%, 134.8%, and 93.7%, respectively. In salt-sensitive variety V3, the activities of SOD, CAT, and POD increased by 50.2%, 119.4%, and 13.3%, respectively, under CK treatment compared to BL; and in V4, the activities of SOD, CAT, and POD increased by 13.2%, 105.3%, and 8.7%, respectively. The increase in antioxidant enzyme activity in salt-tolerant varieties (V1 and V2) was significantly higher than that in salt-sensitive varieties (V3 and V4).

[0136] Compared with salt stress, applying different regulatory measures under salt stress significantly enhanced the activity of antioxidant enzymes. The activities of all three enzymes in each variety were significantly higher under the S1, S2, and S3 treatments than under the CK treatment. Specifically, for SOD, S3 increased the activities of V1 and V2 by 93.3% and 24%, respectively, while S1 increased the activities of V3 and V4 by 103.5% and 130.2%, respectively; for CAT, S3 increased the activities of V1, V2, V3, and V4 by 43.4%, 72.4%, 102.8%, and 49.6%, respectively; and for POD, S2 increased the activities of V1 and V4 by 81.9% and 95.5%, respectively, while S2 increased the activities of V2 and V3 by 94.4% and 174.9%, respectively.

[0137] (4) Root MDA like Figure 17 As shown, salt stress has a significant inducing effect on the root MDA content during the tillering stage of different salt-tolerant rice varieties.

[0138] Compared with the control group, the root MDA of all rice varieties under salt stress was significantly higher than that of the control, and this inhibitory effect varied significantly among different salt-tolerant varieties. Specifically, the MDA of salt-tolerant variety V1 increased by 92.6% and that of V2 increased by 91.3% under the control group; while that of salt-sensitive variety V3 increased by 136.8% and that of V4 by an average of 148.0% under the control group. The root MDA stability of salt-tolerant varieties (V1, V2) was significantly better than that of salt-sensitive varieties (V3, V4). Compared with salt stress treatment, applying different regulatory measures can significantly alleviate the increase in MDA. The MDA of all varieties under S1, S2, and S3 treatments is significantly lower than that under CK treatment. S3 is more effective than S1 and S2 in reducing V1, V2, and V4 by 41.2%, 35.1%, and 27.2%, respectively, while S1 reduces V3 by 54.7%.

[0139] (5) Root soluble protein like Figure 18 As shown, salt stress has a significant inducing effect on the content of soluble protein in the roots of different salt-tolerant rice varieties during the tillering stage.

[0140] Compared with the control group, the soluble protein content of all varieties under salt stress treatment was significantly higher than that under the control group, and this induction effect showed obvious differences in salt tolerance among different varieties. Specifically, the soluble protein content of salt-tolerant variety V1 increased by 11.8% under CK treatment compared to BL, and that of V2 increased by 25.7%; while the soluble protein content of salt-sensitive variety V3 increased by 1.7% under CK treatment compared to BL, and that of V4 increased by 8.7%. The increase in soluble protein content of salt-tolerant varieties (V1 and V2) was significantly higher than that of salt-sensitive varieties (V3 and V4).

[0141] Applying different regulatory measures under salt stress significantly increased the accumulation of soluble protein content. The soluble protein content of all varieties under S1, S2, and S3 treatments was significantly higher than that under the CK treatment. Specifically, S3 increased V1 and V2 by 27.7% and 20.7%, respectively, while S2 increased V3 and V4 by 26.6% and 26.3%, respectively.

[0142] 3.8 Effects of salt stress on the quality of different rice varieties 3.8.1 Processing quality and appearance quality Table 12 Effects of salt stress on rice processing and appearance

[0143] Table 12 shows that treatment (T) has a significant impact on the processing quality and appearance quality of rice. P<0.01; The interaction between treatment and variety (T×V) was not significant (ns, P>0.05).

[0144] (1) Brown rice rate Compared with the control group, salt stress significantly reduced the brown rice percentage in all salt-tolerant rice varieties, with the reduction being significantly greater in salt-sensitive varieties (V3, V4) than in salt-tolerant varieties (V1, V2). The reductions for V1, V2, V3, and V4 were 16.9%, 17.2%, 24.9%, and 30.9%, respectively. Compared with salt stress, all three control measures significantly restored the brown rice percentage under salt stress. S2 was more effective than S1 and S3 in restoring the percentages of V1, V2, V3, and V4, with increases of 19.3%, 13.1%, 29.7%, and 37.6%, respectively.

[0145] (2) Rice milling rate Compared with the control group, salt stress significantly reduced the milling rate of different salt-tolerant rice varieties, with the reduction in salt-sensitive varieties (V3, V4) being significantly greater than that in salt-tolerant varieties (V1, V2). The reduction rates for V1, V2, V3, and V4 were 13.4%, 15.2%, 19.5%, and 25.2%, respectively. Compared with salt stress, all three control measures significantly restored the milling rate under salt stress. S2 was more effective than S1 and S3 in restoring the milling rate of V1, V2, V3, and V4, with increases of 11.6%, 4.9%, 16.5%, and 21.5%, respectively.

[0146] (3) Head rice rate Compared with the control group, salt stress significantly reduced the head rice percentage of different salt-tolerant rice varieties, with the reduction being significantly greater in salt-sensitive varieties (V3, V4) than in salt-tolerant varieties (V1, V2). The reductions for V1, V2, V3, and V4 were 26.5%, 25.1%, 29.6%, and 27.6%, respectively. Compared with salt stress, all three control measures significantly restored the head rice percentage under salt stress. S2 was more effective than S1 and S3 in restoring the head rice percentage for V1, V2, V3, and V4, with increases of 34.3%, 18.5%, 26.3%, and 37.1%, respectively.

[0147] (4) Chalky grain rate Compared with the control group, salt stress significantly increased the chalky grain rate in different salt-tolerant rice varieties, with the increase in salt-sensitive varieties (V3, V4) being significantly higher than that in salt-tolerant varieties (V1, V2). The increases for V1, V2, V3, and V4 were 60%, 72.3%, 106.8%, and 100%, respectively. Compared with salt stress, all three control measures significantly restored the chalky grain rate under salt stress. S1 was more effective for V1 than S2 and S3, reducing it by 26.4%. S2 was more effective for V2 and V3 than S1 and S3, reducing them by 24.1% and 48.7%, respectively. S3 was more effective for V4 than S1 and S2, reducing it by 6.9%.

[0148] (5) Chalkiness Compared with the control group, salt stress significantly increased the chalkiness of different salt-tolerant rice varieties, with the increase in salt-sensitive varieties (V3, V4) being significantly higher than that in salt-tolerant varieties (V1, V2). The increases for V1, V2, V3, and V4 were 83.3%, 80.6%, 213%, and 139.4%, respectively. Compared with salt stress, all three regulatory measures significantly restored chalkiness under salt stress. S3 was more effective than S1 and S3 in restoring chalkiness to V1 and V4, with reductions of 36.4% and 19.7%, respectively. S2 was more effective than S1 and S3 in restoring chalkiness to V2, with a reduction of 39.3%. S1 was more effective than S2 and S3 in restoring chalkiness to V3, with a reduction of 63.9%.

[0149] like Figure 19 As shown, in terms of overall effect, S2 > S1 > S3. S2 performs best in terms of processing quality (especially head rice rate) and chalky grain rate reduction; S1 is better in chalkiness control; although S3 also has a positive effect, its overall effect is slightly inferior to the former two.

[0150] 3.8.2 Effects of salt stress and control measures on the eating taste and nutritional quality of rice Table 13 Effects of salt stress on the eating taste and nutritional quality of different rice varieties

[0151] Table 13 shows that treatment (T) had a significant impact on the eating taste and nutritional quality of rice. P<0.05; The interaction between treatment and variety (T×V) was not significant (ns, P>0.05).

[0152] (1) Amylose content Amylose, a core indicator of rice eating quality, shows a significant response to salt stress during its accumulation process. Compared to the control group, under salt stress, the amylose content of different rice varieties all showed a highly significant decreasing trend, with the decrease in salt-sensitive varieties (V3, V4) being significantly higher than that in salt-tolerant varieties (V1, V2). The decreases in salt-tolerant varieties V1 and V2 were 26.4% and 32.9%, respectively, while the decreases in salt-sensitive varieties V3 and V4 reached 36.2% and 35.6%, respectively. Figure 20 As shown, compared with salt stress, all three regulatory measures could alleviate the inhibitory effect of salt stress on amylose synthesis to varying degrees, and the regulatory effects showed significant variety specificity. S2 had the best effect on improving V1, with an increase of 13.3%, while S1 had relatively significant effects on improving V2 and V4, at 22.1% and 27.1%, respectively. S3 had the largest effect on improving V3, at 25%.

[0153] (2) Albumin content Albumin, a stress-responsive protein in rice grains, directly reflects the stress level of the plant. Compared with the control, salt stress significantly induced albumin accumulation in all varieties, with salt-sensitive varieties showing a significantly higher accumulation rate than salt-tolerant varieties. The albumin content increases for varieties V1, V2, V3, and V4 were 37.3%, 31.0%, 39.4%, and 46.7%, respectively, with the salt-sensitive variety V4 showing the highest increase. Figure 20 As shown, compared with salt stress, all three regulatory measures significantly downregulated the abnormal accumulation of albumin, and the regulatory effects showed significant gradient differences. S1 had the best effect on reducing V1, decreasing it by 25%, while S3 had the best effect on reducing V2, decreasing it by 22.6%. S1 and S3 had the best effect on reducing V3 and V4, decreasing them by 27.3% and 18.2%, respectively.

[0154] (3) Globulin content Globulins, as an important component of rice grain protein, exhibit a relatively mild response to salt stress. Compared with the control group, the globulin content of all tested varieties showed a significant upward trend under salt stress, with considerable differences in the increase among varieties. V4 showed the highest increase (39.4%), while V1 showed the lowest (13.3%), generally indicating a trend where salt-sensitive varieties showed a higher increase than salt-tolerant varieties. Figure 20As shown, compared with salt stress, the three regulatory measures had a weaker overall effect on globulin content, and the response patterns among varieties tended to be consistent, which is consistent with the result of the analysis of variance that the interaction between treatment and variety (T×V) was not significant. Under each regulatory measure, the decrease in globulin content of all varieties did not exceed 10%, with S2 showing the largest decrease in V1 (9.6%).

[0155] (4) Content of alcohol-soluble protein The synthesis and metabolism of prolamins are highly sensitive to salt stress. Compared with the control group, salt stress significantly induced the accumulation of prolamins in all varieties, with the increase in salt-sensitive varieties being much higher than that in salt-tolerant varieties. The increases in salt-tolerant varieties V1 and V2 were 41.0% and 44.0%, respectively, while the increase in salt-sensitive variety V3 was 62.8%, and the increase in V4 was as high as 100.7%, becoming the most severe indicator of salt stress response among all protein components. Figure 20 As shown, compared with the salt-stressed control (CK), the regulatory effects of the three regulatory measures on prolactin decreased. S3 had the best effect on V1, V2, and V3, decreasing by 7.4%, 22.9%, and 20.2%, respectively, while S2 had the best effect on V4, decreasing by 47.1%.

[0156] (5) Gluten content Glycine, the most abundant storage protein in rice grains, directly determines the nutritional quality of rice. Compared with the control group, salt stress significantly increased the glutenin content of all varieties, with salt-sensitive varieties showing a higher increase than salt-tolerant varieties. V2 showed the lowest increase (9.9%), V4 the highest (88.6%), and V1 and V3 increased by 32.1% and 53.6%, respectively. Figure 20 As shown, compared with salt stress CK, all three regulatory measures significantly downregulated abnormal gluten accumulation. S2 had the best effect on V1, V2, and V3, reducing them by 20.7%, 14.9%, and 15.4%, respectively, while S1 had the best effect on V4, reducing it by 22.7%.

[0157] 3.8.3 Effects of salt stress and control measures on rice starch viscosity characteristics (RVA profile) Table 14 Effects of salt stress on the viscosity properties (RVA profile) of rice starch

[0158] As shown in Table 14, the effects of treatment (T), variety (V), and all RVA spectral indices (peak viscosity, hot slurry viscosity, disintegration value, final viscosity, recovery value, and reduction value) were all highly significant. P < 0.001. Treatment × Variety (T × V), the interaction had a highly significant effect on all parameters except peak viscosity. (P<0.001), with no significant effect on peak viscosity (ns, P>0.05).

[0159] (1) Peak viscosity Compared with the control group, under salt stress, the peak viscosity content of different rice varieties all showed a highly significant decreasing trend, and the decrease in salt-sensitive varieties (V3, V4) was significantly higher than that in salt-tolerant varieties (V1, V2). The decreases in salt-tolerant varieties V1 and V2 were 13.5% and 12.5%, respectively, while the decreases in salt-sensitive varieties V3 and V4 reached 18.3% and 26.0%, respectively. Figure 21 As shown, compared with salt stress, all three regulatory measures can alleviate the inhibitory effect of salt stress on peak viscosity to varying degrees. S2 has a better effect on improving V1, V3, and V4 than S1 and S3, with increases of 12.1%, 15.9%, and 24.2%, respectively. S3 has the best effect on improving V2, with an increase of 11.6%.

[0160] (2) viscosity of hot paste Compared with the control group, under salt stress, the thermal viscosity content of different rice varieties all showed a highly significant decreasing trend, and the accumulation rate of salt-sensitive varieties was significantly higher than that of salt-tolerant varieties. The decreases in thermal viscosity of V1, V2, V3, and V4 were 12.0%, 21.4%, 27%, and 33.1%, respectively, with the salt-sensitive variety V4 showing the largest decrease. Figure 21 As shown, compared with salt stress, all three control measures can significantly increase the viscosity of the thermal slurry. S2 has the best effect on improving V1, V2 and V3, with increases of 13.5%, 22.7% and 17.9% respectively, while S1 has the best effect on improving V4, with an increase of 10.8%.

[0161] (3) Disintegration value Compared with the control group, the disintegration values ​​of all tested varieties under salt stress showed a significant decreasing trend, with large differences in the degree of decrease among varieties. V3 showed the largest decrease (37.8%), while V2 showed the smallest decrease (13.3%). Overall, the decrease in salt-sensitive varieties was greater than that in salt-tolerant varieties. Figure 21 As shown, compared with salt stress, all three regulatory measures significantly increased the disintegration value. S1 had the best effect on increasing V1, with an increase of 5.5%, S3 had the best effect on increasing V2, with an increase of 10.3%, and S2 had the best effect on increasing V3 and V4, with increases of 48.2% and 46.5%, respectively.

[0162] (4) Final viscosity Compared with the control group, salt stress significantly increased the final viscosity of different rice varieties. The increases were 17.6% and 15.7% for salt-tolerant varieties V1 and V2, respectively, 22.9% for salt-sensitive variety V3, and a staggering 48.1% for V4. Figure 21 As shown, compared with salt stress (CK), the effects of the three control measures on final viscosity decreased. S2 had the best effect on V1, V2, V3, and V4, decreasing them by 9.9%, 6.6%, 16.6%, and 31.5%, respectively.

[0163] (5) Response value Compared with the control group, salt stress significantly increased the recovery values ​​of different rice varieties, with salt-sensitive varieties showing a higher increase than salt-tolerant varieties. For example... Figure 21 As shown, compared with the salt-stressed control group (CK), all three regulatory measures significantly reduced the recovery values. S2 was most effective for V1, V2, V3, and V4, reducing them by 43.6%, 39.0%, 53.2%, and 65.5%, respectively.

[0164] (6) Decrease value Compared with the control group, salt stress significantly increased the reduction values ​​of different rice varieties, and the increase was higher in salt-sensitive varieties than in salt-tolerant varieties. Figure 21 As shown, compared with salt stress CK, all three regulatory measures significantly reduced the attenuation value. S3 was most effective for V1 and V2, S1 was most effective for V3, and S2 was most effective for V4.

[0165] 4. Conclusion In summary, this invention used two salt-tolerant rice varieties (V1 and V2) and two salt-sensitive varieties (V3 and V4) as materials, and conducted field trials for two consecutive years to systematically explore the effects of salt stress during the tillering stage on rice yield, growth characteristics, photosynthetic physiology, antioxidant and osmotic regulation, nitrogen absorption, root physiology, and rice quality. The regulatory effects and variety specificity of S1 (nitrogen fertilizer), S2 (γ-aminobutyric acid), and S3 (salicylic acid) were clarified. Based on correlation analysis and membership function comprehensive evaluation, the following conclusions were drawn: I. Overall Effects of Salt Stress on Rice (1) Salt stress during the tillering stage significantly inhibited the growth and development of rice, reducing plant height, number of tillers, leaf area index and biomass. The number of tillers was most sensitive to salt stress, and the degree of inhibition in salt-sensitive varieties was significantly higher than that in salt-tolerant varieties.

[0166] (2) Salt stress significantly reduces the content of photosynthetic pigments and light energy utilization efficiency. Light energy utilization is the direct cause of the yield decline. At the same time, it disrupts the balance of the antioxidant system, leading to a large accumulation of MDA and aggravated membrane lipid peroxidation damage.

[0167] (3) Salt stress significantly inhibits root morphogenesis and physiological activity. Root oxidative power is significantly positively correlated with yield, and is a key root factor that restricts yield formation under salt stress.

[0168] (4) Salt stress significantly reduces the total amount of nitrogen absorbed by plants. Nitrogen absorption is highly positively correlated with yield, and yield is mainly determined by affecting the number of ears per unit area and the seed setting rate.

[0169] (5) Salt stress significantly reduces rice yield. The number of panicles per unit area and the seed setting rate are the most sensitive yield components, which synergistically determine the yield level. At the same time, it significantly deteriorates processing quality, appearance quality and eating quality. There is a significant synergistic relationship between quality and yield.

[0170] II. Common Regulatory Effects of Exogenous Regulatory Substances S1, S2, and S3 can all effectively alleviate salt stress damage, with the core physiological mechanism being the synergistic effect of four major pathways: (1) Increase the content of photosynthetic pigments and enhance the efficiency of light energy capture and utilization; (2) Enhance the activity of SOD, CAT and POD, reduce the content of MDA, and alleviate membrane lipid peroxidation damage; (3) Promotes the accumulation of osmotic regulatory substances and maintains cell osmotic pressure and water balance; (4) Optimize root morphology, enhance root oxidation capacity and sap flow intensity, and promote nitrogen absorption and transport.

[0171] III. Variety-specificity of regulatory effects (1) Salt-tolerant varieties (V1, V2): S1 (nitrogen fertilizer) has the best overall effect and the highest membership function value. It can significantly improve photosynthesis, nitrogen absorption, tillering and biomass, steadily increase the seed setting rate and the number of ears per unit area, and the yield recovery rate reaches 79.4%, and significantly improve the processing quality.

[0172] (2) Salt-sensitive varieties (V3, V4): S3 (salicylic acid) has the best regulatory effect and the highest membership function comprehensive value. It can effectively reduce MDA content, repair cell membranes, protect root function, significantly increase the number of grains per ear and the seed setting rate, and the yield recovery rate reaches 69.1%.

[0173] (3) S2 (γ-aminobutyric acid) plays an auxiliary regulatory role in both types of varieties. It has a positive effect on tiller number, accumulation of soluble sugar and proline, and some quality indicators, but its overall effect is weaker than that of S1 and S3.

[0174] (4) Critical regulation period: The tillering stage is the most critical period for exogenous substances to alleviate salt stress and restore growth and yield.

[0175] IV. The Law of Synergistic Regulation of Yield and Quality (1) Under salt stress, the head rice yield, amylose, and hot paste viscosity were significantly positively correlated with yield, while chalkiness and protein composition were significantly negatively correlated with yield, revealing the physiological basis for the synergistic regulation of yield and quality.

[0176] (2) All three control measures can significantly restore rice quality. The overall effect ranking is: S2 > S1 > S3. S2 is the best in improving head rice rate and chalky grain rate, S1 is better in controlling chalkiness, and S3 is outstanding in restoring the eating quality of salt-sensitive varieties.

[0177] V. Innovation Points (1) The system elucidates the intrinsic relationship between rice yield, growth, photosynthesis, antioxidant, nitrogen, root system and quality under salt stress, identifies MDA, root oxidative power, nitrogen absorption and light energy utilization as the core limiting factors, and reveals the synergistic regulation mechanism of yield and quality.

[0178] (2) Compared with most studies, which mainly focus on the physiological mechanisms under salt stress, this experiment, in addition to the physiological mechanisms, further explored the salt-tolerant cultivation regulation technology, providing theoretical and practical basis for the stress-resistant cultivation of rice.

[0179] (3) Combining correlation analysis and membership function method to quantitatively evaluate the regulation effect, providing scientific basis and technical support for the selection of exogenous regulation measures for rice in saline-alkali land.

[0180] It will be readily understood by those skilled in the art that the above-described advantageous methods can be freely combined and superimposed without conflict. The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A cultivation regulation method for improving salt tolerance of rice at tillering stage, characterized in that, include: The salt stress treatment is started at the tillering stage from the 10th day to the 20th day after rice transplanting, and on the day of the salt stress treatment, an exogenous regulating substance is applied according to the salt tolerance characteristics of the rice variety; the exogenous regulating substance is selected from nitrogen fertilizer, γ at least one of aminobutyric acid and salicylic acid; The nitrogen application amount of the nitrogen fertilizer is 80 kg N / ha to 120 kg N / ha, and the γ The application concentration of the aminobutyric acid is 470 μmol / L to 530 μmol / L, and the application concentration of the salicylic acid is 320 μmol / L to 380 μmol / L.

2. The method according to claim 1, characterized in that, The salt stress treatment includes: treating with a NaCl solution with a concentration of 80mM~120mM for 6~8 days; after the treatment, irrigation with normal water is carried out.

3. The method according to claim 1, characterized in that, The nitrogen fertilizer is urea, and the application rate is 90 kg N / ha to 110 kg N / ha; the γ The application concentration of GABA is 490 μmol / L to 510 μmol / L; the application concentration of salicylic acid is 340 μmol / L to 360 μmol / L.

4. The method according to claim 1, characterized in that, The nitrogen fertilizer is also applied as basal fertilizer one day before rice transplanting, as tillering fertilizer seven days after transplanting, and as panicle differentiation fertilizer during the young panicle stage; the total nitrogen application of the basal fertilizer, tillering fertilizer and panicle differentiation fertilizer is 220 kg N / ha ~ 260 kg N / ha; the application ratio of the basal fertilizer, tillering fertilizer and panicle differentiation fertilizer is (1.5 ~ 2.5): 1: (1.5 ~ 2.5).

5. The method according to claim 4, characterized in that, The base fertilizer also includes phosphate fertilizer applied in the form of Ca(H2PO4)2 and potassium fertilizer applied in the form of KCl; the application rate of phosphate fertilizer is 80 kg P / ha to 120 kg P / ha, and the application rate of potassium fertilizer is 80 kg K / ha to 120 kg K / ha.

6. The method according to claim 1, characterized in that, The rice varieties include salt-tolerant rice and salt-sensitive rice.

7. The method according to claim 6, characterized in that, When the rice variety is salt-tolerant, the nitrogen fertilizer is applied as an exogenous regulatory substance; when the rice variety is salt-sensitive, the salicylic acid is applied as an exogenous regulatory substance.

8. The method according to claim 6, characterized in that, The salt-tolerant rice is FL478 or Nanjing 11, and the salt-sensitive rice is Zhongnong 4 or Nipponbare.

9. The application of the method according to any one of claims 1-8 in improving salt tolerance during the tillering stage of rice, increasing rice yield under salt stress, and / or improving rice quality.

10. The application according to claim 9, characterized in that, The application includes at least one of the following: (1) Increase the number of tillers, plant height, leaf area index and biomass of rice; (2) Improve the photosynthetic pigment content and light energy utilization efficiency of rice; (3) Enhances the activity of antioxidant enzymes in rice and reduces the degree of membrane lipid peroxidation; (4) Promotes the accumulation of osmotic regulatory substances in rice; (5) Optimize rice root morphology and root vigor, and improve nitrogen absorption; (6) Increase the number of effective panicles, the number of grains per panicle, the seed setting rate and the thousand-grain weight of rice, thereby increasing the yield; (7) Improve the processing quality, appearance quality, taste quality and starch viscosity characteristics of rice under salt stress.

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