Method for improving salt-alkali tolerance of sesbania by using melatonin

Abstract

The present application relates to the field of agricultural technology, and provides a method for improving the salt and alkali tolerance of sesbania by using melatonin, comprising the following steps: (1) soaking sesbania seeds with a melatonin aqueous solution, rinsing after soaking, and obtaining soaked sesbania seeds; (2) sowing the soaked sesbania seeds and spraying a melatonin aqueous solution on the sesbania seedlings. The method is green, safe, simple to operate, does not increase the field operation link, has no risk of secondary soil pollution, is suitable for different types of main sesbania cultivars such as high salt and alkali tolerance and moderate salt and alkali tolerance, has strong universality, is fully suitable for the large-scale planting of sesbania in severe soda saline-alkali land, and realizes the synergistic effect of ecological management and green manure production in severe saline-alkali land.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and in particular to a method for improving the salt and alkali tolerance of sesbania using melatonin. Background Technology

[0002] Saline-alkali land is an important reserve of strategic arable land resources. Its efficient development, utilization, and ecological improvement are crucial measures to ensure food security and protect the black soil ecosystem. Soda-saline soil (NaHCO3 / Na2CO3) has a high pH value and high Na content. + With its typical barrier characteristics of high content, high carbonate content, low permeability, and low nutrient availability, it is one of the most difficult types of saline-alkali soil to manage globally.

[0003] Sesbania, an annual herbaceous plant belonging to the genus Sesbania in the legume family, possesses strong tolerance to salinity, waterlogging, and poor soil conditions. It also exhibits unique nitrogen-fixing capabilities through root nodules, making it a pioneering green manure crop and a top choice for improving saline-alkali land. It can rapidly increase soil organic matter content, improve soil aggregate structure, and enhance soil nitrogen reserves, demonstrating significant ecological and economic value. However, under severe soda saline-alkali stress, Sesbania's salt tolerance reaches a threshold, frequently resulting in a sharp drop in seed germination rate, stunted growth, and a significant decline in biomass—a core bottleneck. Current technologies lack targeted solutions, severely limiting its widespread application in severely soda saline-alkali land.

[0004] Current technologies for improving severely saline-alkali land, as well as supporting technologies for sesbania cultivation, have significant application shortcomings, which can be summarized as follows: 1. Engineering Improvement Measures. The main approach is to achieve salt leaching and alkali removal through water conservancy engineering measures such as establishing irrigation and drainage systems, constructing terraced fields, and laying underground pipes. However, this method has the problems of large engineering workload, high modification costs, and high operational difficulty. In particular, the Songnen Plain in Northeast China is a severely saline-alkali land with low-lying terrain and poor drainage in most plots. Ditch drainage and well drainage are extremely ineffective and are not suitable for low-cost large-scale planting of green manure crops.

[0005] 2. Chemical amendment measures. This mainly involves applying gypsum, desulfurized gypsum, and acidic amendments to reduce soil salinity and alkalinity through acid-base neutralization. However, this method is only effective for mild to moderately saline-alkali land and has limited effect on severely saline-alkali land with a pH of around 9.8. Furthermore, it suffers from high modification costs, a high risk of secondary soil pollution, and frequent reversion of salinity and alkalinity after modification, which does not meet the core requirements of green manure planting for being green, low-carbon, and eco-friendly.

[0006] 3. Agronomic improvement measures. The main methods used are deep plowing, deep burial of straw, and ridge cultivation to regulate soil water and salt transport. However, these methods cannot overcome the inhibitory effect of severe soda salinity stress on sesbania seed germination, nor can they solve the core bottleneck of low germination rate and difficulty in seedling survival in severely saline-alkali land. Therefore, they have a very small effect on improving the growth of sesbania.

[0007] 4. Biological improvement measures. These mainly include the breeding of salt-tolerant varieties, the application of microbial agents, and the regulation of plant growth regulators. Among these, the breeding cycle for salt-tolerant sesbania varieties is long and the breeding cost is high. Even highly salt-tolerant varieties are still severely inhibited in the severely saline-alkali environment with a pH of around 9.8. Microbial agents are difficult to colonize in severely saline-alkali soils with high pH values, and their application effects are extremely unstable and costly. Although there are sporadic reports of the application of melatonin, as a natural plant growth regulator, in staple crops such as wheat and corn, there is a complete lack of specific application schemes for sesbania under severe soda saline-alkali stress. There are no suitable parameters for different salt-tolerant sesbania varieties, and the existing scattered parameters cannot be adapted to severely saline-alkali environments, resulting in extremely poor field application effects and hindering large-scale promotion. Summary of the Invention

[0008] The purpose of this invention is to provide a method for enhancing the salt and alkali tolerance of sesbania using melatonin. Addressing the core problem of severely saline-alkali soils where sesbania's own salt and alkali tolerance reaches a threshold, germination and growth are severely limited, and there is a lack of dedicated, efficient, and green supporting control technologies, this invention provides a method for enhancing the salt and alkali tolerance of sesbania using melatonin. By employing standardized melatonin soaking technology, the endogenous stress resistance system of sesbania is activated from the seed germination stage, breaking through its own salt and alkali tolerance threshold. This significantly improves the seed germination rate, germination potential, and seedling survival rate of different salt-tolerant sesbania varieties under severe soda saline-alkali stress. By optimizing the core parameters of the entire soaking process, the oxidative damage to sesbania plants under severe saline-alkali stress is alleviated, promoting root and plant growth during the seedling stage, increasing aboveground biomass, and fully leveraging the legume nitrogen fixation and green manure soil improvement functions of sesbania. This method is simple to operate, low in cost, and environmentally friendly with no secondary pollution, making it perfectly suited to the agricultural needs of large-scale sesbania cultivation in severely soda saline-alkali land. Ultimately, it achieves the synergistic goal of efficient pioneer green manure cultivation and soil ecological improvement in severely soda saline-alkali land.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for improving the salt and alkali tolerance of sesbania using melatonin, comprising the following steps: (1) Soak the sesame seeds in a melatonin solution, rinse them after soaking, and obtain the soaked sesame seeds; (2) Sow the soaked sesame seeds and spray the sesame seedlings with melatonin solution.

[0010] Preferably, the sesame seeds in step (1) are disinfected before soaking; the disinfection method is as follows: soak in a 1.8-2.2% sodium hypochlorite solution for 8-12 minutes, then rinse with sterile water 4-6 times, drain and set aside.

[0011] Preferably, the concentration of the melatonin aqueous solution in step (1) is 50 μmol / L to 100 μmol / L.

[0012] Preferably, the ratio of melatonin aqueous solution to sesquiterpene seeds in step (1) is 4-5 mL: 1 g.

[0013] As a preferred option, the soaking method in step (1) is to soak the sesame seeds at a constant temperature of 23-27℃ in a dark environment for 8-12 hours.

[0014] Preferably, sterile water is used for rinsing in step (1), and the rinsing is performed 3 to 4 times.

[0015] Preferably, the spraying time in step (2) is when the sesbania seedlings are at the 3-leaf stage, and the spraying time is after sunset.

[0016] Preferably, the concentration of the melatonin aqueous solution during spraying in step (2) is 50 μmol / L to 100 μmol / L.

[0017] Preferably, the application rate of the melatonin aqueous solution in step (2) is 0.8~1.2 L / m³. 2 .

[0018] Beneficial effects: This invention addresses the core bottleneck in sesbania cultivation in severely saline-alkali lands by establishing, for the first time, a standardized melatonin application technology system adapted to different salt-tolerant sesbania varieties. This fills the gap in specialized stress-regulating technology for sesbania under severe soda-salt stress. By activating the endogenous stress-resistance system during sesbania seed germination, this invention overcomes its own salt tolerance threshold, systematically improving the germination ability, seedling survival rate, and biomass accumulation of sesbania in severely saline-alkali habitats. The entire process is green and safe, with no secondary pollution, and the operational steps are fully compatible with existing field practices. This is an innovative green manure stress-resistance cultivation technology for severely saline-alkali lands.

[0019] This invention, based on the common biological characteristics of sesbania seeds with different salt-alkali tolerances and combined with the stress patterns of severely sodium-sodium saline-alkali habitats, has developed core parameters for the entire process of melatonin seed soaking. It has formulated a complete technical solution including standardized seed pretreatment, soaking concentration, soaking time, soaking environment control, and post-soaking treatment. The invention clarifies the systematic improvement effect of this solution on the germination, seedling growth, and physiological stress resistance of different salt-alkali tolerant sesbania varieties under severe sodium-sodium saline-alkali stress. Currently, there is no standardized implementation plan for the application of melatonin in sesbania under severe sodium-sodium saline-alkali stress, and field validation data has not yet been published.

[0020] This invention only requires soaking the seeds before sowing sesbania, without adding any additional field planting steps. It is fully compatible with conventional sesbania sowing processes and has strong operability. The reagents used in this method are green and environmentally friendly. In severely saline-alkali environments, it can stably improve the germination rate, seedling survival rate, and aboveground biomass of sesbania varieties with different salt and alkali tolerances. The improvement effect is stable, can be replicated and promoted on a large scale, and has strong practicality. Attached Figure Description

[0021] Figure 1 The effects of different concentrations of melatonin on germination indices of Zhongke Jing 1 seeds under severe saline-alkali stress; Figure 2 The effects of different concentrations of melatonin on the germination indices of Lujing 5 seeds under severe saline-alkali stress; Figure 3 The effect of melatonin on antioxidant-related indicators of Zhongke Jing 1 under severe saline-alkali stress; Figure 4 The effect of melatonin on antioxidant-related indicators of Zhongke Jing 1 under severe saline-alkali stress. Detailed Implementation

[0022] This invention provides a method for improving the salt and alkali tolerance of sesbania using melatonin, comprising the following steps: (1) Soak the sesame seeds in a melatonin solution, rinse them after soaking, and obtain the soaked sesame seeds; (2) Sow the soaked sesame seeds and spray the sesame seedlings with melatonin solution.

[0023] In this invention, the sesame seeds in step (1) are disinfected before soaking; the disinfection method is preferably: soaking in a 1.8~2.2% sodium hypochlorite solution for 8~12 minutes, then rinsing with sterile water 4~6 times, draining and setting aside, and more preferably: soaking in a 2% sodium hypochlorite solution for 10 minutes, then rinsing with sterile water 5 times, draining and setting aside.

[0024] In this invention, the concentration of the melatonin aqueous solution in step (1) is preferably 50 μmol / L to 100 μmol / L, and more preferably 100 μmol / L.

[0025] In this invention, the ratio of melatonin aqueous solution to sesquiterpene seeds in step (1) is preferably 4-5 mL:1 g, and more preferably 4 mL:1 g.

[0026] In this invention, the soaking method in step (1) is preferably: soaking the sesame seeds at a constant temperature of 23~27℃ in a dark environment for 8~12 h, and more preferably: soaking the sesame seeds at a constant temperature of 25℃ in a dark environment for 12 h.

[0027] In this invention, sterile water is preferably used for rinsing in step (1), and the number of rinsings is preferably 3 to 4 times.

[0028] In this invention, the spraying time in step (2) is preferably the 3-leaf stage of the sesbania seedlings, and the spraying time is preferably after sunset.

[0029] In this invention, the concentration of the melatonin aqueous solution during spraying in step (2) is preferably 50 μmol / L to 100 μmol / L, and more preferably 100 μmol / L.

[0030] In this invention, the preferred application rate of the melatonin aqueous solution in step (2) is 0.8~1.2 L / m³. 2 More preferably 1 L / m 2 .

[0031] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example

[0033] 1. Test site and materials

[0034] This experiment consisted of two parts: an indoor severe soda saline-alkali stress control experiment and a field in-situ verification experiment. The indoor experiment was conducted in the artificial climate chamber of the Grassland Research Institute of the Heilongjiang Academy of Agricultural Sciences. The field experiment was conducted at the severe soda saline-alkali land experimental base in Lindian County, Daqing City, at 124°18′35″E, 46°44′27″N. The geographical location is a mid-temperate continental monsoon climate. The soil type of the experimental site is saline-alkali meadow soil. The average pH value of the 0-20cm soil layer is 9.85, the electrical conductivity is 992.4 µs / cm, and the total salt content is 0.64%, which is typical of severe soda saline-alkali land.

[0035] Experimental materials: The tested sesbania varieties were the highly salt-tolerant variety "Zhongkejing No. 1" and the moderately salt-tolerant variety "Lujing No. 5"; melatonin was analytical grade with a concentration ≥99.8%.

[0036] 2. Experimental Design

[0037] (1) Indoor germination test under severe sodium salt stress

[0038] The experiment employed a single-factor, completely randomized experimental design, using a mixed sodium bicarbonate solution with a NaCl:Na₂SO₄:NaHCO₃:Na₂CO₃ mass ratio of 1:9:9:1 and a concentration of 160 mmol / L to simulate severe saline-alkali stress in the field. Seven melatonin seed soaking concentrations were set up: 0 (water control, CK), 25 μmol / L, 50 μmol / L, 75 μmol / L, 100 μmol / L, 150 μmol / L, and 200 μmol / L. Each treatment was set up separately for two varieties, Zhongkejing 1 and Lujing 5, with five biological replicates per treatment and 30 seeds per replicate. The seed soaking treatment was uniformly carried out in accordance with the technical solution of this invention: after the seeds completed the standardized disinfection pretreatment, they were placed in melatonin solutions of corresponding concentrations at a liquid-to-seed ratio of 4 mL / g, and soaked at a constant temperature of 25℃ and in complete darkness for 12 h; after soaking, the seeds were rinsed 4 times with sterile water, drained, and placed in petri dishes lined with two layers of sterile filter paper. 5 mL of the above-mentioned severe salt-alkali stress solution was added to each petri dish, and the dishes were placed in an artificial climate chamber with a constant temperature of 25℃, constant humidity of 70%, and 12 h light / 12 h darkness for cultivation.

[0039] (2) Field in-situ verification test

[0040] The experiment used "Zhongke Jing 1" and "Lujing 5" as the test varieties, and set up two treatment groups: one group was soaked in water as a blank control (CK); the other group adopted the optimal treatment scheme of this study, namely, soaking seeds in 100 μmol / L melatonin for 12 h (MT). A randomized block design was adopted, with 4 replicates for each treatment. The ridge width was 0.65 m, the ridge length was 5 m, the field management method was uniform, the seeding rate was 2.5 kg / hm² (40 seeds / m on the ridge), and the seeding depth was 2-3 cm.

[0041] (3) Survey indicators and methods

[0042] ① Seed germination indicators

[0043] Germination rate and germination potential of sesbania seeds in each treatment were statistically analyzed, and germination index and seed vigor index were calculated; the germination standard was radicle protrusion ≥2 mm.

[0044] Germination potential (GP) = Number of seeds germinated on day 4 / Total number of seeds × 100%; Germination rate (GR) = Number of germinated seeds on day 7 / Total number of seeds × 100%; Germination index (GI) = Σ(Gt / Dt); Vitality Index (VI) = Germination Index × Sprout Length.

[0045] ② Seedling growth and physiological indicators

[0046] On day 7 after melatonin supplementation, the relative electrical conductivity, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, and proline content of seedling leaves were measured. All indicators were measured using industry-standard methods, and each treatment was repeated three times. On day 14 after melatonin supplementation, the seedling height, taproot length, fresh weight per plant, and dry weight per plant of sesbania seedlings in each treatment were measured. In the field experiment, the survival rate of plants was counted at the sesbania seedling stage (30 days after sowing), and the plant height, aboveground fresh weight, and dry weight were measured at the full flowering stage. Soil samples were collected from the 0-20 cm soil layer before sowing and after sesbania harvest to measure soil pH, electrical conductivity (EC), organic matter content, and available nitrogen content.

[0047] (4) Results and Analysis

[0048] ① Effects of melatonin treatment on seed germination of different sesbania varieties under severe saline-alkali stress

[0049] Depend on Figure 1 and Figure 2 It was found that under severe salt-alkali stress of 160 mmol / L, seed soaking treatment with 50–100 μmol / L melatonin significantly improved the seed germination ability of two varieties, “Zhongkejing No. 1” and “Lujing No. 5”, with the 100 μmol / L melatonin treatment showing the most significant improvement. For the highly salt-tolerant variety Zhongkejing No. 1, compared with the control (CK), the germination rate, germination potential, germination index, and seed vigor index of *Senecio scandens* after seed soaking with 100 μmol / L melatonin were significantly increased by 10.67%, 16.67%, 10.11%, and 49.24%, respectively, all reaching a significant level (P<0.05). For the moderately salt-tolerant guarana variety Lujing 5, compared with the water control, the germination rate, germination potential, germination index, and seed vigor index significantly increased by 17.33%, 19.33%, 18.80%, and 112.51%, respectively, after soaking in 100 μmol / L melatonin (P<0.05). This demonstrates that the 100 μmol / L melatonin soaking treatment has a stable promoting effect on the germination of guarana varieties with different salt-alkali tolerance levels under salt-alkali stress, and is universally applicable.

[0050] ② Effects of melatonin on seedling growth of different sesbania varieties under severe saline-alkali stress

[0051] The experimental results showed that the combined treatment of seed soaking and spraying with 100 μmol / L melatonin significantly promoted the growth and development of sesbania seedlings under severe salt-alkali stress. Although melatonin had a greater promoting effect on the morphological indicators of 'Lujing 5' cultivar, compared with the control (CK), the plant height, stem diameter, and dry matter accumulation in both above-ground and below-ground parts of the seedlings in both treatment groups were significantly increased. This demonstrates that the method of this invention can effectively alleviate the inhibitory effect of severe salt-alkali stress on the seedling growth of different salt-tolerant sesbania varieties, and break through their own salt-alkali tolerance thresholds.

[0052] ③ Effects of melatonin on antioxidant indicators of different sesbania varieties under severe saline-alkali stress

[0053] Depend on Figure 3 , 4 It can be seen that, compared with the control (CK), the treatment of soaking seeds in 100 μmol / L melatonin and spraying can significantly increase the activity of antioxidant enzymes SOD and POD, while promoting the content of osmotic regulator proline, reducing the content of membrane lipid peroxidation product MDA and relative conductivity, effectively activating the plant's endogenous antioxidant system, improving osmotic regulation capacity, alleviating the damage of severe salt and alkali stress to sesbania cell membranes, systematically enhancing the salt and alkali tolerance of sesbania from a physiological level, and having a stable promoting effect on different salt-tolerant varieties.

[0054] ④ Field in-situ verification test

[0055] Field trials conducted in severely saline-alkali land showed that, compared with the control group (CK), the two sesbania varieties treated with the preferred method of this invention exhibited significantly superior growth: the seedling survival rate, flowering height, and aboveground dry matter accumulation of "Zhongkejing 1" and "Lujing 5" were significantly increased. Post-harvest soil testing revealed that, compared with the pre-sowing soil, the average pH value of the 0-20 cm soil layer in the treatment group decreased by 0.38, electrical conductivity decreased by 2.15%, soil organic matter content increased by 4.27%, and available nitrogen content increased by 12.58%. These improvement effects were significantly better than the control group (CK), demonstrating that the method of this invention can simultaneously achieve the dual goals of improving the salt tolerance of sesbania in severely saline-alkali land and improving soil ecology.

[0056] in conclusion

[0057] The melatonin application method provided by this invention can significantly overcome the salt tolerance threshold of sesbania itself, solving the core bottleneck of inhibited seed germination and severely suppressed seedling growth in different salt-tolerant sesbania varieties under severe soda salt stress at around pH 9.8. Based on the results of both indoor and field trials, the preferred method of this invention is as follows: Sesbania seeds are soaked in a 100 μmol / L melatonin solution under constant temperature and light conditions at 25℃ for 12 hours; once the sesbania seedlings have grown to the 3-leaf stage, foliar spraying with the same concentration of melatonin solution is performed between 20:00 and 21:00 at a dosage of 1 L / m². 2 This program has shown excellent improvement effects on both the highly salt-tolerant variety "Zhongkejing No. 1" and the moderately salt-tolerant variety "Lujing No. 5", and has strong field applicability and universality.

[0058] As can be seen from the above embodiments, the present invention provides a method for improving the salt and alkali tolerance of sesbania using melatonin, including the following steps: (1) soaking sesbania seeds in melatonin aqueous solution, rinsing after soaking, and obtaining soaked sesbania seeds; (2) sowing the soaked sesbania seeds and spraying the sesbania seedlings with melatonin aqueous solution. The present invention breaks through the salt and alkali tolerance threshold of sesbania itself, significantly improves the seed germination ability and seedling survival rate of different salt-tolerant sesbania varieties under severe soda saline-alkali stress, effectively solves the core bottleneck of difficult emergence and poor seedling survival of sesbania in severely saline-alkali land, and fills the gap in sesbania-specific salt and alkali tolerance regulation technology. It can systematically enhance the stress resistance of sesbania in severely saline-alkali environment, alleviate the oxidative damage of plants to plants caused by high pH value and high salt and alkali stress, promote the growth of roots and aboveground parts during the seedling stage, significantly improve the biomass accumulation of sesbania, give full play to the nitrogen fixation and green manure soil improvement functions of sesbania leguminous root nodules, and rapidly improve the soil fertility of severely soda saline-alkali land. The method of this invention is green, safe, and easy to operate. It does not add any extra field operations and has no risk of secondary soil pollution. At the same time, it is compatible with different types of sesbania var. mongolica, such as those with high salt and alkali tolerance and those with moderate salt and alkali tolerance. It has strong versatility and is fully adapted to the needs of large-scale planting of sesbania var. mongolica in severely saline-alkali land, thus achieving synergistic effects between ecological management of severely saline-alkali land and green manure production.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the salt tolerance of sesbania using melatonin, characterized in that, Includes the following steps: (1) Soak the sesame seeds in a melatonin solution, rinse them after soaking, and obtain the soaked sesame seeds; (2) Sow the soaked sesame seeds and spray the sesame seedlings with melatonin solution.

2. The method according to claim 1, characterized in that, The sesame seeds mentioned in step (1) are disinfected before soaking. The disinfection method is as follows: soak in a 1.8-2.2% sodium hypochlorite solution for 8-12 minutes, then rinse with sterile water 4-6 times, drain and set aside.

3. The method according to claim 1 or 2, characterized in that, The concentration of the melatonin aqueous solution in step (1) is 50 μmol / L to 100 μmol / L.

4. The method according to claim 3, characterized in that, The ratio of melatonin aqueous solution to sesquiterpene seeds in step (1) is 4-5 mL: 1 g.

5. The method according to claim 3, characterized in that, The soaking method described in step (1) is to soak the sesame seeds at a constant temperature of 23-27℃ in a dark environment for 8-12 hours.

6. The method according to claim 3, characterized in that, Sterile water is used for rinsing in step (1), and the rinsing is performed 3 to 4 times.

7. The method according to claim 3, characterized in that, The spraying period described in step (2) is when the sesbania seedlings are at the 3-leaf stage, and the spraying time is after sunset.

8. The method according to claim 3, characterized in that, The concentration of the melatonin aqueous solution during spraying in step (2) is 50 μmol / L to 100 μmol / L.

9. The method according to claim 3, characterized in that, The application rate of the melatonin aqueous solution in step (2) is 0.8~1.2 L / m³. 2 .

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