Effects Of Ascorbic Acid(AsA)on Cold Tolerance And Antioxidant Mechanism Of Cotton Seeds

[Purpose]Cotton plays an important position in China’s agricultural production.In recent years,climate variability at sowing time has a significant impact on the growth and yield of cotton,the cotton growth period was delayed and the normal growth and development process was hindered,so the yield decreased and the quality became worse.Therefore,to enhance the cold tolerance of cotton seed germination and reasonable technical measures,to implement early sowing in cotton production,to resist the risk of cotton cold damage at early low temperature,it is of great significance to ensure the normal growth period,yield and quality of cotton.Ascorbic acid（AsA）is a kind of hexosetose lipid compound synthesized in animals and plants.It is a macromolecule antioxidant widely found in plants and animals,ascorbic acid（AsA）can promote the germination of crops and the growth of seedlings under adversity in Nakatane.The experiment was conducted to study the effects of ascorbic acid（AsA）on seed germination ability and photosynthesis of cotton seedlings under low temperature stress,and to explore its stress-resistant mechanism,the regulation effect of ascorbic acid（AsA）on cotton under low temperature stress was revealed.[Method]Taking Xinluzao 61 as experimental material,the germination characteristics of cotton seeds at low temperature（15°C）were measured by using different concentrations of ascorbic acid（AsA）at different time,to study the effect of ascorbic acid priming on cold tolerance of cotton seed germination,and to select the best priming combination,and to measure the response of photosynthetic and chlorophyll fluorescence characteristics of cotton seedlings to low temperature stress under different ascorbic acid treatments,the effects of ascorbic acid on cold tolerance of cotton seedlings were investigated,and the optimal ascorbic acid treatment method was determined The activities of major antioxidant enzymes and AsA-GSH related enzymes in cotton seeds were analyzed before,after and during germination in the optimal priming combination,the mechanism of antioxidation regulation of ascorbic acid（AsA）on cold tolerance of cotton seed germination was revealed.[Result]（1）The germination of cotton seeds was accelerated by ascorbic acid solution priming.It was found that 50mg/L ascorbic acid（AsA）could promote germination of cotton seeds under low temperature stress,the germination potential,germination rate,germination index and germination index of cotton seeds were increased by 11.11%,12.30%,43.28%and 43.30%,and the average germination time was shortened by 0.2 days.（2）Seeds were primed with 50 mg/L ascorbic acid（AsA）for 24 h,the photosynthetic and chlorophyll fluorescence parameters of seedlings were measured at one-heart stage of two leaves,c I increased continuously,but TR increased significantly with the prolongation of low temperature stress,and decreased by 36.16%compared with CK at normal temperature on the 2nd day,Fv/Fo and Fv/Fm increased by96.77%and 67.63%on the 4th and 3rd day,respectively.（3）As the seedlings reach the two-leaf stage,the results showed that spraying 25 mg/L ascorbic acid（AsA）on the 1st,3rd and 5th day before low temperature stress had the most significant effect on light system of seedlings,the concentrations of 25 mg/L ascorbic acid Tr,Pn,Gs and Ci decreased by 68.27%,37.56%,54.67%and 13.80%,respectively.Compared with CK-T,Fo,Fv/Fo,Fv/Fm and PI_ABSwere significantly relieved at low temperature for 5 days,and Fo decreased by 10.69%at the 3rd day,Fv/Fm and Fv/Fo increased significantly by 34.25%and 35.62%on the 2nd day,and PI_ABSincreased by 22.49%on the 1st day.（4）At the concentration of 50mg/LAsA for 24h,the activity of SOD,POD,CAT and the content of MDA were alleviated under low temperature stress,compared with CK-T,on the 3rd day of germination,SOD and POD increased by 46.99%,POD increased by 84.03%,CAT increased by six times,MDA content decreased by 42.14%The activities of APX,MDHAR,DHAR,GR,GPX of AsA-GSH increased by202.17%,48.27%,42.79%,43.95%,147.69%onthe3rddayand31.64%,83.22%,33.51%,44.45%,203.82%on the 7th day compared with those of CK-T;Compared with CK-T,the contents of AsA,DHA,GSH and GSSG increased by 94.60%,29.62%,92.15%,71.20%and90.23%,62.23%,50.13%and 65.50%respectively on the 3rd day and 7th day of the Glutathione cycle（AsA-GSH）.[Conclusion]Ascorbic acid（AsA）treatment can improve the ability of seed germination under low temperature stress,alleviate the damage of low temperature to seed antioxidant system,and promote seed germination In addition,ascorbic acid alleviated the damage of low temperature to the light system of seedlings,alleviated the phenomena of excessive light energy and photoinhibition in the leaves of seedlings,and improved the tolerance of cotton seedlings to low temperature,it provides a reasonable and effective solution for a series of problems caused by low temperature in seed germination and seedling stage.