The Study Of Exogenous Selenium On The Growth And Anthocyanin Synthesis In The Purple Lettuce

Although selenium(Se)is not necessary for plant,it is an important trace element for human?animal and microorganism.The appropriate intake of selenium can increase the regeneration of traumatic tissue and resistance,so selenium is known as "life protection agent".In this study,the aim is to ascertain the physiological response of seedling stage of purple lettuce(Lactuca sativa L.)cv.'Purple Rome' to different selenite concentration(0,4,8,12,16 ?M)in the form of selenite added into the hydroponic systems,including the response of growth,anthocyanin content,selenium content and oxidative damage index.In order to explore the effect of selenite on anthocyanin accumulation and antioxidant system,we analysed the related gene expression in seedling stage of purple lettuce using the real time quantitative PCR(qRT-PCR).The result will evaluate which selenite concentration is more advantageous and provide theoretical guidance for the production of enriched anthocyanins and selenium in purple lettuce.The results are shown below:Firstly,anthocyanin content and selenium content increased significantly with the increase of exogenous selenium concentration.The low concentration of selenite(4-8 ?M)could significantly promote the growth of purple lettuce at seedling stage,increasing the fresh weight of plant and promote the accumulation of anthocyanin and soluble sugar,but the higher concentration of selenite(?8 ?M)could inhibit plant growth.Secondly,the level of lipid membrane peroxidation(MDA)was not obviously affected below 4 ?M,which may be result from the enhancement of antioxidant capacity.The activities of SOD,POD and CAT were significantly increased by selenite treatment,and SOD activity reached the maximum at 8 ?M,which was 1.6 times of that of control.POD activity reached the maximum at 4 ?M.CAT activity reached the maximum value at 16?M.Fluorescence probe analysis showed that the fluorescence density of O2·-,ROS and PI decreased first and then increased.The fluorescence density of ROS and PI was lower than that of control at 4 ?M.After that,the fluorescence density gradually increased,and were significantly higher than the control.The results of qRT-PCR showed that the expression of CAT gene was up-regulated at 16 ?M with the increase of selenium concentration.The expression level of SOD gene was up-regulated and then decreased and the expression level was the highest at 8?M and the lowest at 16 ?M.Therefore,the concentraction of 4?M can improve the antioxidant enzyme activity and antioxidant capacity of purple lettuce at seedling stage.Thirdly,we analysed the effect of selenite on seedling stage of purple lettuce anthocyanin accumulation and related gene expression by using real time fluorescence quantitative expression technology.Results showed that the expression of CHS gene increased significantly and riched the maximum value at the concentration of 16?M,which was 2.04 times of that of the control.And each treatment was significantly higher than the control.