Physiological Regulation Mechanism Of Exogenous Betaine On Germination And Growth Characteristics Of Rice Seeds Under High Temperature Stress

Rice was one of the most important food crops in China.As global climate warms and the frequency of extreme weather increases,high temperature stress had become one of the most important stresses in rice production.At present,in the rice planting area of the middle and lower reaches of the Yangtze River,farmers generally had the habit of one season rice direct seeding,and the seeds after direct seeding were often affected by high temperature and heat damage,which seriously affected the germination of rice seeds.Betaine was an important osmotic adjustment substance in plants,which could improve the resistance of plants to various environmental stresses.Therefore,this experiment used different concentrations of exogenous betaine to soak seeds,which was used Xiangzaoxian 45 as the material,to explore the effect of different temperatures on the germination characteristics of rice seeds,and to determine the germination rate,vigor index,morphological characteristics,antioxidant enzyme activity and malondialdehyde content and other indicators.It provided a theoretical basis for clarifying the physiological regulation mechanism of rice seeds under different temperatures.At the same time,the regulation mechanism of betaine on the germination of rice seeds under high temperature stress was explored by measuring the activity of antioxidant system and the content of endogenous hormones in the process of germination of rice seeds under high temperature stress.It laid a foundation for the application of betaine in rice production.The main conclusions of this study were as follows:(1)Betaine could alleviate the damage of seed germination caused by high temperature to some extent,and 10mmol/L betaine was the most effective.It could significantly promote the root growth,increase root length,root surface and so on,and could significantly improve the activities of SOD、POD and CAT under high temperature stress.(2)After soaking with 10 mmol/L betaine(M1),the SOD activity under high temperature stress could be significantly improved.The SOD activity of the endosperm-ruptured seeds(SG3)was significantly increased,which was increased by 10.88 times compared with the control M2.During the germination process of betaine seed soaking treatment(M1),the MDA content of the endosperm-ruptured seeds(SG3)was significantly reduced by 41.8% compared with the control M2.Under high temperature stress,the content of IAA and GA20 in the endosperm-ruptured seeds(SG3)of 10 mmol/L betaine seed soaking treatment(M1)was reduced by 42.78% and 50.98% compared to the control M2,and the ABA content was compared the control M2 also decreased by 29.04%,both of which reached a significant difference.(3)Through transcriptomics analysis,it was found that betaine was mainly through the down regulation of related genes such as GH3,SAUR,PP2 C,TCH4,TGA in the synthesis of auxin,abscisic acid and salicylic acid could alleviate the damage of rice seed germination under high temperature stress.