Application of Zinc Citrate in Improving Plant Salt Stress Resistance and Improving Saline-Alkali Land

Abstract

This invention relates to the field of agricultural technology, and particularly to the application of zinc citrate in improving plant salt stress resistance and remediating saline-alkali land. This invention is the first to utilize zinc citrate to enhance plant salt stress resistance. Zinc citrate can effectively improve the germination ability of plant seeds under salt stress, increase the activity of the plant's antioxidant system and photosynthetic efficiency, thereby effectively improving the survival rate and growth performance of plants under salt stress. Simultaneously, zinc citrate can effectively reduce the EC value of saline-alkali soil, achieving effective remediation of saline-alkali land, and further improving the germination rate of plant seeds in saline-alkali land.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and in particular to the application of zinc citrate in improving plant salt stress resistance and in the improvement of saline-alkali land. Background Technology

[0002] Salt-alkali stress is one of the major obstacles restricting agricultural development. Globally, the area of ​​saline-alkali land exceeds 950 million hectares, with my country accounting for approximately 100 million hectares. Salt-alkali stress causes multiple harms to plants, including osmotic stress, ion toxicity, and oxidative damage, leading to stunted growth, reduced yields, and even death. High-salt environments limit water absorption, causing cell dehydration and leaf scorching and wilting, thus affecting plant growth and development. Furthermore, salt negatively impacts ion balance and nutrient absorption, thereby reducing photosynthetic and nutrient synthesis capabilities.

[0003] Currently, methods for alleviating salt stress in plants mainly include engineering improvement, biological improvement, and chemical improvement. Engineering improvement is costly and time-consuming; biological improvement is greatly affected by environmental conditions and its own characteristics, making it difficult to achieve ideal application results. Chemical improvement is widely used due to its simplicity and rapid effectiveness. Zinc, as an essential micronutrient for plants, participates in the activation of various enzymes and photosynthetic metabolism, and appropriate supplementation can enhance crop salt tolerance. However, in saline-alkali soils, traditional zinc fertilizers are easily fixed, resulting in extremely low utilization rates and limiting the potential of zinc in enhancing crop stress resistance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an application of zinc citrate in improving plant salt stress resistance and improving saline-alkali land. Zinc citrate can reduce the soluble salt content in saline-alkali soil and significantly improve the ability of plants to resist salt stress.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides the use of zinc citrate in improving plant salt stress resistance and / or in improving saline-alkali land.

[0006] Zinc is an essential micronutrient for plants; however, traditional zinc fertilizers are easily fixed, resulting in extremely low utilization rates and limiting zinc's potential in enhancing crop stress resistance. Through extensive research, the inventors of this application unexpectedly discovered that zinc citrate can significantly improve plants' resistance to salt-alkali stress and effectively reduce the soluble salt content in soil as a soil conditioner, thus solving the problems of poor plant growth and low yields in moderately to severely saline-alkali environments found in existing technologies.

[0007] Studies have shown that, on the one hand, zinc citrate can effectively improve the germination ability of plant seeds under salt stress, and enhance the activity of plant antioxidant systems and the efficiency of plant photosynthesis, thereby effectively improving the survival rate and growth performance of plants under salt stress; on the other hand, zinc citrate can effectively reduce the EC value of saline-alkali soil, achieving effective improvement of saline-alkali land, thereby further improving the germination rate of plant seeds in saline-alkali land.

[0008] In some embodiments of the present invention, the zinc citrate is used to improve at least one of the following properties of plants under salt stress: (A) seed germination ability; (B) seedling growth performance; (C) antioxidant system activity; (D) photosynthetic efficiency.

[0009] In some preferred embodiments of the present invention, the antioxidant system in the (C) antioxidant system activity includes at least one of superoxide dismutase, peroxidase, and catalase.

[0010] In other embodiments of the invention, the zinc citrate is used to reduce the electrical conductivity of saline-alkali land.

[0011] In a second aspect, the present invention provides a method for improving the salt stress resistance of plants, comprising applying a zinc citrate solution to at least one of the following (a)-(d): (a) Plants subjected to salt stress; (b) Plants at risk of salt stress; (c) The growth environment of plants under salt stress; (d) Plant growth environment with salt stress risk.

[0012] In some embodiments of the present invention, the concentration of zinc citrate in the zinc citrate solution is 10-1000 mg / L, preferably 10-800 mg / L.

[0013] In some embodiments of the present invention, the concentration of zinc citrate in the zinc citrate solution is 10-100 mg / L.

[0014] In some preferred embodiments of the present invention, the concentration of zinc citrate in the zinc citrate solution is 100 mg / L.

[0015] The concentration of zinc citrate in a zinc citrate solution affects its ability to improve plant salt stress resistance. Experimental results show that when the concentration of zinc citrate in the solution is 10-1000 mg / L, zinc citrate can effectively improve the plant's resistance to salt-alkali stress. Within this concentration range, the effect of zinc citrate in alleviating salt stress shows a pattern of "first increasing, then decreasing" with increasing concentration. When the concentration of zinc citrate in the solution is 10-100 mg / L, it shows a stable and significant alleviating effect on plant seed germination, seedling growth, and physiological indicators. Especially when the concentration of zinc citrate is 100 mg / L, its effect on improving plant salt-alkali stress resistance reaches its optimal level.

[0016] In some embodiments of the present invention, the zinc citrate solution is an aqueous solution of zinc citrate.

[0017] In some embodiments of the present invention, the plant growth environment under salt stress is saline-alkali land with a soil salt content of 0.3%-2.0%.

[0018] In some embodiments of the present invention, the zinc citrate solution is applied by at least one of soil irrigation, foliar spraying, and seed treatment.

[0019] In some embodiments of the present invention, the zinc citrate solution is applied by soil irrigation, and the amount of zinc citrate applied per acre of soil is 10-25 kg.

[0020] In some embodiments of the present invention, the zinc citrate is applied when the seeds are planted in the growth substrate, and then applied every 2-4 days. In some preferred embodiments of the present invention, the zinc citrate is applied when the seeds are planted in the growth substrate, and then applied every 3 days.

[0021] In some embodiments of the present invention, the plant includes at least one of food crops, vegetables, flowers, and fruit trees.

[0022] In some embodiments of the present invention, the plant is at least one of rapeseed, corn, wheat, and sorghum.

[0023] Thirdly, the present invention provides the application of zinc citrate in combination with water-soluble fertilizers for improving plant salt stress resistance.

[0024] Studies have shown that the combined application of zinc citrate and water-soluble fertilizers has a synergistic effect, which is more conducive to improving the plant's resistance to salt stress.

[0025] In some embodiments of the present invention, the water-soluble fertilizer is a water-soluble fertilizer specifically for saline-alkali land.

[0026] In some embodiments of the present invention, the water-soluble fertilizer contains nitrogen, phosphorus, and potassium; the water-soluble fertilizer contains 20% total nitrogen, 20% phosphorus (calculated as P2O5), and 20% potassium (calculated as K2O) by mass percentage. This water-soluble fertilizer can effectively supplement the nitrogen, phosphorus, and potassium macroelements required by plants under salt stress.

[0027] In some embodiments of the present invention, the weight ratio of zinc citrate to water-soluble fertilizer is 1:5.

[0028] In some embodiments of the present invention, the zinc citrate is used in the form of a zinc citrate solution with a concentration of 100 mg / L; the water-soluble fertilizer is used in the form of a water-soluble fertilizer solution with a concentration of 500 mg / L; and the volume ratio of the zinc citrate solution to the water-soluble fertilizer solution is 1:1. The zinc citrate solution and the water-soluble fertilizer solution are prepared and used immediately.

[0029] In some embodiments of the present invention, the water-soluble fertilizer further comprises at least one of humic acid and amino acids. Humic acid / amino acids can further improve soil aggregate structure and promote the absorption of zinc ions and nutrients by plant roots; zinc citrate achieves salt resistance by reducing soil EC value and activating the plant's antioxidant system. The two form a triple synergistic mechanism of "soil improvement + synergistic nutrient supply + enhanced plant stress resistance". Compared with zinc citrate alone, combined application can increase the seed germination rate of plants by 10%-25%, increase seedling height / root length by 15%-30%, increase fresh weight by 20%-35%, and significantly improve salt resistance.

[0030] Fourthly, the present invention provides a product for improving the salt stress resistance of plants, comprising zinc citrate and water-soluble fertilizer, and further comprising at least one of soil conditioner and plant growth regulator.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: Zinc citrate is an environmentally friendly organic zinc source, but its application in improving saline-alkali land and enhancing plant resistance to salt stress has not been reported. This invention is the first to utilize zinc citrate in improving plant resistance to salt stress, which is of great significance for fully utilizing saline-alkali land resources and increasing crop yields.

[0032] Zinc citrate can effectively improve the germination ability of plant seeds under salt stress, and enhance the activity of plant antioxidant systems and the efficiency of plant photosynthesis, thereby effectively improving the survival rate and growth performance of plants under salt stress. At the same time, zinc citrate can effectively reduce the EC value (Electrical Conductivity) of saline-alkali soil, achieving effective improvement of saline-alkali soil, and further improving the germination rate of plant seeds in saline-alkali soil.

[0033] The combined application of zinc citrate and water-soluble fertilizer in this invention further enriches the application of zinc citrate in saline-alkali land improvement and plant salt stress resistance. The two form a synergistic effect, increasing salt resistance by 8%-35% compared to zinc citrate alone. Simultaneously, it achieves "multiple effects with a single application," improving soil, supplementing zinc micronutrients, and replenishing macronutrients needed for plant growth. This reduces the frequency of fertilizer application, lowers agricultural production costs, and is more suitable for large-scale agricultural production in saline-alkali land, with a broader application prospect. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 The figure shows the effect of zinc citrate on the germination rate of rapeseed under salt stress in Example 1 of the present invention.

[0036] Figure 2 This is a diagram showing the growth of rapeseed under different treatments after 14 days in Example 2 of the present invention.

[0037] Figure 3 The bar graph shows the germination rate of rapeseed at 7 days, the hypocotyl length of rapeseed at 14 days, the root length of rapeseed at 14 days, and the fresh weight of rapeseed at 14 days under different treatments in Example 2 of the present invention.

[0038] Figure 4 This is a diagram showing the germination of maize seeds under different treatments on day 7 in Example 3 of the present invention.

[0039] Figure 5 The images show the germination rate of maize seeds under different treatments on day 7 and the radicle length on day 7 in Example 3 of this invention.

[0040] Figure 6 This is a diagram showing the germination of wheat seeds under different treatments on day 7 in Example 3 of the present invention.

[0041] Figure 7 The graph shows the germination rate, coleoptile length, and radicle length of wheat seeds under different treatments on day 7 in Example 3 of this invention.

[0042] Figure 8 This is a diagram showing the germination of sorghum seeds under different treatments on day 7 in Example 3 of the present invention.

[0043] Figure 9 The graph shows the germination rate, coleoptile length, and radicle length of sorghum seeds under different treatments on day 7 in Example 3 of this invention.

[0044] Figure 10 This is a diagram showing the growth and development of maize under different treatments on day 14 in Example 4 of the present invention.

[0045] Figure 11 The graph shows the germination rate of maize on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments in Example 4.

[0046] Figure 12 This is a diagram showing the growth and development of wheat on day 14 under different treatments in Example 4 of the present invention.

[0047] Figure 13 The graph shows the germination rate of wheat on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments in Example 4 of this invention.

[0048] Figure 14 This is a diagram showing the growth and development of sorghum under different treatments on day 14 in Example 4 of the present invention.

[0049] Figure 15 The graph shows the germination rate of sorghum on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments in Example 4 of this invention.

[0050] Figure 16 The figure shows the effect of zinc citrate on the activities of SOD, CAT and POD in rapeseed leaves under salt stress in Example 5 of the present invention.

[0051] Figure 17 This is a diagram showing the effect of zinc citrate on saline-alkali soil in Example 6 of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] In the following examples, the term "solution" refers to "aqueous solution".

[0054] Example 1: Zinc citrate enhances the germination ability of rapeseed seeds under salt stress. (1) Experimental methods Select plump, uniformly sized seeds of the Brassica napus variety G135. Disinfect the seeds with a 1% sodium hypochlorite solution, then rinse them thoroughly with sterile water to remove the sodium hypochlorite solution. Let them air dry. Use a 4-compartment petri dish (9cm in diameter), placing 15 seeds in each compartment. Line the bottom with a layer of filter paper (e.g., ...). Figure 1 As shown), add 4 mL of different types of solutions.

[0055] Control group: 300 mM NaCl solution (NaCl); Processing Group: Zinc citrate: 300 mM NaCl + 10 mg / L zinc citrate (10-Zn), 300 mM NaCl + 100 mg / L zinc citrate (100-Zn), 300 mM NaCl + 1000 mg / L zinc citrate (1000-Zn).

[0056] Citric acid: 300 mM NaCl + 10 mg / L citric acid (10-C), 300 mM NaCl + 100 mg / L zinc citrate (100-C), 300 mM NaCl + 1000 mg / L zinc citrate (1000-C).

[0057] Zinc sulfate: 300 mM NaCl + 10 mg / L zinc sulfate (10-S), 300 mM NaCl + 100 mg / L zinc sulfate (100-S), 300 mM NaCl + 1000 mg / L zinc sulfate (1000-S).

[0058] Each treatment was performed in triplicate, with the germination rate of seeds after 7 days being used as the evaluation metric for treatment effectiveness.

[0059] Evaluation criteria for germination rate: The length of the hypocotyl of the seed must be greater than the diameter of the seed.

[0060] (2) Experimental results The effect of zinc citrate on rapeseed seed germination rate under salt stress is shown in the figure below. Figure 1 As shown in Table 1 below. Figure 1 In the diagram, A1 represents a 300 mM NaCl solution; A2, A3, and A4 represent the addition of zinc citrate to the 300 mM NaCl solution to achieve zinc citrate concentrations of 10 mg / L, 100 mg / L, and 1000 mg / L, respectively.

[0061] Table 1 shows that under 300 mM NaCl stress, treatment with zinc citrate significantly improved the germination rate of rapeseed seeds, with better results than citric acid and zinc sulfate. For example, treatment with 300 mM NaCl + 100 mg / L zinc citrate resulted in a maximum germination rate of 73.3%, an increase of 171.5% compared to NaCl. Treatment with 300 mM NaCl + 100 mg / L citric acid resulted in a germination rate of 53.32%, an increase of 97.48% compared to NaCl; and treatment with 300 mM NaCl + 100 mg / L zinc sulfate resulted in a germination rate of 53.32%, an increase of 96.39% compared to NaCl. Zinc citrate also significantly promoted the growth of rapeseed hypocotyls and roots, increasing hypocotyl length and root length by 146.7% and 173.0%, respectively, compared to NaCl.

[0062] Table 1. Effects of different reagents on rapeseed seed germination under salt stress.

[0063] Example 2: Zinc citrate improves the growth performance of rapeseed under salt stress. (1) Experimental methods After sterilization, rapeseed seeds (G135) were planted in 7 cm × 7 cm seedling pots containing 100 g vermiculite. The pots were then watered with 150 mL of water (CK), 300 mM NaCl (NaCl), 300 mM NaCl + 10 mg / L zinc citrate (10-Zn), 300 mM NaCl + 100 mg / L zinc citrate (100-Zn), and 300 mM NaCl + 1000 mg / L zinc citrate (1000-Zn), ensuring the liquid did not overflow. Subsequently, 150 mL of 300 mM NaCl + different concentrations of zinc citrate was applied every 3 days for a total of 3 applications. Germination rate was recorded 7 days after sowing, and hypocotyl length, root length, and fresh weight were measured 14 days later. The effect of zinc citrate on rapeseed growth under salt stress was analyzed.

[0064] (2) Experimental results In this embodiment, the growth of rapeseed under different treatments at 14 days is as follows: Figure 2 As shown; the germination rate of rapeseed at 7 days, the hypocotyl length of rapeseed at 14 days, the root length of rapeseed at 14 days, and the fresh weight of rapeseed at 14 days under different treatments are as follows: Figure 3 As shown.

[0065] From the perspective of rapeseed germination rate over 7 days, zinc citrate treatment can significantly improve the germination rate and post-emergence growth of rapeseed. Figures 2-3 Compared with the NaCl control, 10-Zn, 100-Zn, and 1000-Zn increased by 209.87%, 310.73%, and 271.67%, respectively. In terms of 14-day growth performance, zinc citrate promoted hypocotyl elongation in rapeseed, with the 100 mg / L treatment showing the most significant effect, increasing hypocotyl length by 184.5% compared to the NaCl control. Simultaneously, it significantly promoted root length and fresh weight increase in rapeseed, with the 100 mg / L zinc citrate showing the most pronounced effect, increasing root length by 201.9% and fresh weight by 304.4%.

[0066] Example 3: Zinc citrate enhances the germination ability of other crop seeds under salt stress. Experimental materials: maize variety "Zhengdan 958"; sorghum variety "Zhongke Tian 438"; wheat variety "Bainong 607".

[0067] (1) Experimental methods The difference from the experimental method in Example 1 is that rapeseed seeds were replaced with corn seeds, wheat seeds, and sorghum seeds respectively, and CK was a water control; NaCl represents 214 mM NaCl solution; 10-Zn represents 214 mM NaCl + 10 mg / L zinc citrate, 100-Zn represents 214 mM NaCl + 100 mg / L zinc citrate, and 1000-Zn represents 214 mM NaCl + 1000 mg / L zinc citrate.

[0068] (2) Experimental results In this embodiment, the germination status of maize seeds on day 7 under different treatments is as follows: Figure 4 As shown; the germination rate and radicle length of maize seeds on day 7 under different treatments are as follows. Figure 5 As shown; the germination status of wheat seeds on day 7 under different treatments is as follows. Figure 6 As shown; the germination rate, coleoptile length, and radicle length of wheat seeds on day 7 under different treatments are as follows: Figure 7 As shown; the germination status of sorghum seeds on day 7 under different treatments is as follows. Figure 8 As shown; the germination rate, coleoptile length, and radicle length of sorghum seeds on day 7 under different treatments are as follows: Figure 9 As shown.

[0069] Germination experiments showed that 100 mg / L zinc citrate significantly enhanced the germination ability of maize, wheat, and sorghum seeds under salt stress. Compared with 214 mM NaCl solution, 100 mg / L zinc citrate increased the germination rate of maize seeds by 86.4% and the radicle length by 51.0%; increased the germination rate of wheat seeds by 85.7% and the radicle length by 232.5%; and increased the germination rate of sorghum seeds by 85.7% and the radicle length by 117.5%.

[0070] Example 4: Zinc citrate improves the growth performance of other crops under salt stress. Experimental materials: maize variety "Zhengdan 958"; sorghum variety "Zhongke Tian 438"; wheat variety "Bainong 607".

[0071] (1) Experimental methods The difference from the experimental method in Example 2 is that: rapeseed seeds were replaced with corn seeds, wheat seeds, and sorghum seeds respectively, and CK was a water control; NaCl represents 214 mM NaCl solution; 10-Zn represents 214 mM NaCl + 10 mg / L zinc citrate, 100-Zn represents 214 mM NaCl + 100 mg / L zinc citrate, and 1000-Zn represents 214 mM NaCl + 1000 mg / L zinc citrate.

[0072] (2) Experimental results In this embodiment, the growth and development of maize on day 14 under different treatments are as follows: Figure 10 As shown; the germination rate of maize on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments are as follows. Figure 11 As shown; the growth and development of wheat on day 14 under different treatments are as follows. Figure 12 As shown; the germination rate of wheat on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments are as follows: Figure 13 As shown; the growth and development of sorghum under different treatments on day 14 are as follows. Figure 14 As shown; the germination rate of sorghum on day 7, plant height on day 14, root length on day 14, and fresh weight on day 14 under different treatments are as follows: Figure 15 As shown.

[0073] The results showed that compared with NaCl (214 mM NaCl solution), 100 mg / L zinc citrate increased the plant height of maize by 112%, root length by 71.6%, and fresh weight by 86.8%; increased the plant height of wheat by 24.2%, root length by 75.9%, and fresh weight by 26.7%; and increased the plant height of sorghum by 77.4%, root length by 60.4%, and fresh weight by 52.9%.

[0074] Example 5: Zinc citrate alters the redox balance in crops under salt stress. (1) Experimental methods After sterilization, rapeseed seeds were planted in 7 cm × 7 cm seedling pots containing approximately 100 g of vermiculite. The pots were then watered with 150 mL of water (CK), 300 mM NaCl (NaCl), and 300 mM NaCl + 100 mg / L zinc citrate (100-Zn), ensuring the liquid did not overflow. Subsequently, 50 mL of 300 mM NaCl + different concentrations of zinc citrate was applied every 3 days for a total of 3 applications. The aboveground and underground parts were harvested after 14 days. The effects of zinc citrate on crop physiological indicators under salt stress were analyzed.

[0075] (2) Experimental results In this embodiment, the effects of zinc citrate on the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in rapeseed leaves under salt stress are as follows: Figure 16 As shown.

[0076] Depend on Figure 16 As can be seen, in a 300 mM NaCl solution, the addition of 100 mg / L zinc citrate significantly increased the CAT activity in rapeseed from 4686.2 U / g protein to 4965.98 U / g protein; SOD and POD activities increased by 25.9% and 95.8%, respectively. 100 mg / L zinc citrate exhibits the activity of scavenging excess ROS (reactive oxygen species), enhancing the plant's antioxidant defense system and reducing the negative effects of high salt stress.

[0077] Example 6: Zinc citrate effectively reduces the electrical conductivity of saline-alkali land. (1) Experimental methods The effect of zinc citrate on soil layers (0–30 cm) in saline-alkali land was simulated using a cylindrical container (60 cm high, 12 cm diameter) filled to a depth of 30 cm with soluble salts containing 0.5 wt% and an electrical conductivity (EC1:5) of (1610 ± 50) μS / cm. -1Saline-alkali soil with a pH of 8.52±0.05 (soil-to-water ratio 1:5) was irrigated with 200 mL of water (CK) and 100 mg / L zinc citrate (A), respectively. Then, 100 mg / L zinc citrate was applied every 7 days. The control group was irrigated with deionized water using the same method. 200 mL was applied each time, for a total of two applications. Soil samples were taken every 5 cm after 14 days to measure electrical conductivity (EC).

[0078] (2) Experimental results The effects of zinc citrate on saline-alkali soils are as follows: Figure 17 As shown in the figure; where CK is the water control and A is zinc citrate. After 14 days of treatment, zinc citrate was used in a cylindrical tank to simulate the 0–30 cm soil depth in saline-alkali soil. In the 0–5 cm soil layer, the EC of the water control was 1611 µS / cm, while the EC of the 0–5 cm soil layer in the cylindrical tank after adding 100 mg / L zinc citrate was 417.7 µS / cm. Therefore, compared with water, 100 mg / L zinc citrate can significantly reduce soil EC by 74.1%.

[0079] Example 7: Combined application of zinc citrate and water-soluble fertilizer enhances crop germination and growth performance under salt stress. (1) Experimental methods Test crops: rapeseed (G135), wheat (Bainong 607), maize (Zhengdan 958), sorghum (Zhongke Tian 438); Test reagent: ① Single application group: 100mg / L zinc citrate aqueous solution + NaCl; rapeseed 300mM NaCl, wheat / corn / sorghum 214mM NaCl; ② Combined application: 100 mg / L zinc citrate aqueous solution + 500 mg / L water-soluble fertilizer solution for saline-alkali land + NaCl; 300 mM NaCl for rapeseed, 214 mM NaCl for wheat / corn / sorghum; the composition of the water-soluble fertilizer for saline-alkali land is: N-P2O5-K2O=20-20-20 (containing 5 wt% humic acid). The volume ratio of zinc citrate aqueous solution to water-soluble fertilizer solution is 1:1. Prepare and use immediately. ③ Blank control (CK): Water; ④ Salt stress control (NaCl): rapeseed 300mM NaCl, wheat / corn / sorghum 214mM NaCl; Experimental design: Seed disinfection, petri dish / nutrient pot treatment methods, replication settings, and statistical standards for indicators were completely consistent with those of Examples 1, 2, 3, and 4; Application method: Soil irrigation / seed treatment, the same as the application method of zinc citrate alone. For each acre of soil, apply the mixed solution equivalent to 10-25 kg of zinc citrate + 50-125 kg of water-soluble fertilizer.

[0080] (2) Experimental results In this embodiment, the optimal concentration of 100 mg / L zinc citrate aqueous solution was used as a control. The combined application was used to determine the effect of improving seed germination rate and seedling growth indicators (plant height / root length / fresh weight) of crops under salt stress. At the same time, the activities of antioxidant enzymes (SOD / CAT / POD) in rapeseed were measured according to the method in Example 5. The results are shown in Tables 2-4 below: Table 2. Effects of single vs. combined application of zinc citrate on crop seed germination rate under salt stress.

[0081] Table 3. Effects of single vs. combined application of zinc citrate on crop seedling growth indicators under salt stress.

[0082] Table 4. Effects of zinc citrate single application vs. combined application on antioxidant enzyme activity in rapeseed under salt stress.

[0083] The results showed that the combined application of zinc citrate and water-soluble fertilizer for saline-alkali soil at a 1:1 volume ratio significantly improved the seed germination rate and seedling growth indicators (plant height / root length / fresh weight) of rapeseed, wheat, corn, and sorghum under salt stress compared to zinc citrate alone. Rapeseed germination rate increased by 20.9% compared to zinc citrate alone, and fresh weight increased by 386.8% compared to the salt-stress control, demonstrating a significant synergistic effect. The combined application further activated the plant's antioxidant defense system. Under salt stress, the activities of SOD, CAT, and POD in rapeseed increased by 29.9%, 16.5%, and 32.7% respectively compared to zinc citrate alone, enabling more efficient removal of reactive oxygen species (ROS), alleviating oxidative damage caused by salt stress, and enhancing plant salt stress resistance. The synergistic mechanism was as follows: zinc citrate reduced soil EC value and increased zinc ion bioavailability, while the water-soluble fertilizer supplemented nitrogen, phosphorus, and potassium macronutrients and promoted root development through humic acid, forming a "soil improvement + micronutrient supply + The triple-action system of "synergistic effects of macronutrients" achieves dual optimization of the soil-plant nutrient system. This combined application scheme is simple to operate, and the application method is completely consistent with that of zinc citrate alone. No additional adjustments to the field operation process are required, making it suitable for large-scale agricultural application in saline-alkali land.

[0084] It should be noted that when zinc citrate is used in combination with water-soluble fertilizers in this invention, the following precautions should be taken to ensure synergistic effects: 1. Prepare and use immediately: Mix zinc citrate solution and water-soluble fertilizer solution at a ratio of 1:1 (by volume) and apply immediately to avoid prolonged storage which may cause nutrient complexation and inactivation. 2. Application timing: It is best to apply the basal fertilizer to the soil before crop sowing, or to irrigate before / at the beginning of seedling stress. Under severe stress in saline-alkali soil (soil salinity 1.5%-2.0%), it can be applied once every 7 days for 2-3 consecutive times. 3. Incompatibilities: Avoid mixing with strong alkaline fertilizers or phosphate fertilizers alone to prevent zinc ion fixation. If phosphate fertilizers need to be applied, they should be applied 5-7 days apart from the mixture of this invention. 4. Scope of application: It can be used in combination with soil conditioners and plant growth regulators. It is suitable for various application methods such as irrigation of saline-alkali soil, foliar spraying, and seed soaking. When spraying foliar, the mixture needs to be diluted 500 times to avoid burning the leaves. When treating seeds, the seeds can be soaked in the undiluted solution for 6-8 hours, dried, and then sown. 5. Dosage control: The combined application of the mixed solution should not exceed 25 kg of zinc citrate and 125 kg of water-soluble fertilizer per acre of soil to avoid excessive nutrients leading to secondary soil salinization.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of zinc citrate in improving plant salt stress resistance and / or improving saline-alkali land.

2. A method for improving the salt stress resistance of plants, characterized in that, This includes applying a zinc citrate solution to at least one of the following (a)-(d): (a) Plants subjected to salt stress; (b) Plants at risk of salt stress; (c) Plant growth environment under salt stress; further, the plant growth environment under salt stress is saline-alkali land with a soil salt content of 0.3%-2.0%; (d) Plant growth environment with salt stress risk.

3. The method for improving plant salt stress resistance according to claim 2, characterized in that, The concentration of zinc citrate in the zinc citrate solution is 10-1000 mg / L, preferably 10-800 mg / L.

4. The method for improving plant salt stress resistance according to claim 3, characterized in that, The concentration of zinc citrate in the zinc citrate solution is 100 mg / L.

5. The method for improving plant salt stress resistance according to any one of claims 2-4, characterized in that, The zinc citrate solution is an aqueous solution of zinc citrate.

6. The method for improving plant salt stress resistance according to any one of claims 2-5, characterized in that, The zinc citrate solution can be applied by at least one of soil irrigation, foliar spraying, or seed treatment. Preferably, the zinc citrate solution is applied by soil irrigation, and the amount of zinc citrate applied per acre of soil is 10-25 kg.

7. The method for improving plant salt stress resistance according to any one of claims 2-6, characterized in that, The plants include at least one of food crops, vegetables, flowers, and fruit trees.

8. The method for improving plant salt stress resistance according to claim 7, characterized in that, The plant is at least one of rapeseed, corn, wheat, and sorghum.

9. Application of zinc citrate combined with water-soluble fertilizer in improving plant salt stress resistance; preferably, the water-soluble fertilizer contains nitrogen, phosphorus and potassium; wherein, by mass percentage, the total nitrogen content is 20%, the phosphorus content (calculated as P2O5) is 20%, and the potassium content (calculated as K2O) is 20%; Preferably, the water-soluble fertilizer further comprises at least one of humic acid and amino acids.

10. A product for improving the salt stress resistance of plants, characterized in that, The products used to improve plant salt stress resistance include zinc citrate and water-soluble fertilizers, as well as at least one of soil conditioners and plant growth regulators.

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