Effects Of Tea Polyphenols On Non-enzymatic Clearance Mechanism Of Reactive Oxygen Species In Wheat Seedlings Under Salt Stress

Salinized soils are widespread in the world,and the area is still expanding,which can cause osmotic stress on the plants and destroy ion balance,and even induce the accumulation of large amounts of reactive oxygen species?ROS?to affect the normal growth,development of plants and crops yield reduction.Tea polyphenols are a natural antioxidant and have the advantages of being non-toxic and harmless.Therefore,it is practical significance to explore the response of exogenous TP to plant physiological mechanisms under salt stress.In this experiment,Longchun 30 wheat?Triticum aestivum L.?was taken as the research object.Through measuring the relevant growth and physiological indexes of wheat under different treatment,the growth characteristics of Longchun 30 wheat seeding and the active oxygen non-enzymatic protection system were discussed.The response of 150mmol·L^-1NaCl,Tea Polyphenols?TP?and the combined treatment of the two,the main results are as follows:1.Salt stress significantly reduced the relative growth rate?RGR?,biomass and leaf area of wheat seedlings,but increased leaf specific gravity;the addition of TP effectively alleviated the reduction of RGR,biomass and leaf area of wheat seedlings under salt stress,increased the specific gravity on the contrary.At the same time,the higher of the TP concentration,the more obvious for the relief effect.2.The high Na⁺concentration in the salt treatment environment restricted the absorption of K⁺and Ca²⁺by the root system,thereby weakening the transfer rate of these two kinds of nutrition ions;the addition of TP improved the selective absorption and transport coefficient of these two ions by wheat seedlings,higher TP concentration will increase the impact on nutrient ions'absorption and transportion.3.The treatment with 150mmol·L^-1 NaCl inhibited non-enzymatic antioxidants significantly,reduced the synthesis of ascorbic acid?AsA?,reduced glutathione?GSH?,carotenoids,total flavonoids,total phenols and anthocyanins,the formation also caused a large accumulation of proline content;the amount of TP not only increased the ratio of AsA/DHA and GSH/GSSG,but also increased the content of non-enzymatic antioxidants.4.150mmol·L^-11 Salt treatment reduced the scavenging rates of hydroxyl free radicals?·OH?,H₂O₂ radicals,and ABTS^·?in wheat seedlings,but increased the scavenging rates of superoxide anion radicals(O₂^·?);the addition of TP made the scavenging rates of·OH and H₂O₂ radicals were improved uncommonly.When the concentration of TP was 100mg·L^-1,the ABTS scavenging rate and iron reducing power were significantly enhanced.5.Salt increased the activity of phenylalanine ammonia lyase?PAL?and polyphenol oxidase?PPO?significantly,while 4-coumarin acid coenzyme A ligase?4CL?and Chalcone isomerase?CHI?enzyme activity were significantly reduced,during the growth of wheat;adding some TP under salt stress,the activity of PAL did not change significantly,but PPO activity decreased,while the decline of 4CL and CHI's activity are more significant.The above results show that salt stress inhibits plant growth by affecting the plant's absorption of potassium and calcium nutritional ions,which is manifested by the reduction of RGR and biomass;and by changing the activities of related enzymes in the flavonoid synthesis pathway,reducing total flavonoids,polyphenols Synthesis of phenol and anthocyanins;In addition,salt treatment also changed AsA-GSH cycle rate and normal synthesis of non-enzymatic synthetic substances such as carotenoids and proline in wheat seedlings,and weakened the reactive oxygen species.The addition of TP increased the selective absorption and transport coefficient of K⁺and Ca²⁺in wheat seedlings under150mmol·L^-11 NaCl treatment,and promoted the growth of wheat seedlings by increasing the RGR and leaf surface area.At the same time,the addition of TP to the plant AsA-GSH Circulation and flavonoid pathways have a corresponding impact,resulting in a significant increase in the amount of non-enzymatic antioxidants,thereby improving the plant's antioxidant capacity and enhancing the free radical scavenging effect of wheat seedlings.