Effects Of Selenite On Chlorophyll Fluorescene And Xanthophyll Cycle Of Rice Exposed To The Stresses Of Salt And High Light Intensity

Salt stress and high light intensity are main factors limiting the production of rice,especially in rice seedling and reproductive stages.However,previous researches seldom focused on the effect of both stress,and whether exogenous selenite could alleviated the stress effect and its possible underlying mechanism are still unclear.We investigate the effects of synergistic effect of slt and high light intensity on the non-photochemical quenching and xanthophyll cycle of rice,and the possible alleviation effects of selenite when responsive to the two stresses.In the present experiment,the rice seedlings are treated with two levels of selenite,salt and light inten sity independently and with their combinations,and analyzed some physiological indicators,including chlorophyll fluorescence,content of malondialdehyde,activity of catalyse,photochemical reflectance index,content of chlorphyll and total content of canthophyll cycle pigments.The main results are listed below.1.When treated with salt and high light intensity stress,total content of xanthophyll cycle pigments are greatly reduced,photochemical quenching,non-photochemical quenching,efficiency of PhotosystemⅡ,electron transport rate,photochemical reflectance index,activity of catalyse,content of chlorophyll a,content of chlorophyll b,content of chlorophyll a and chlorophyll b,totally content of xanthophyll cycle pigments are significantly reduced.And content of malondialdehyde and ration between chlorophyll a and chlorophyll b are significantly increased,and has little influence on the content of carotenoid.2.When treated with salt and high light intensity stress synergistically,selenite treatment can greatly increase total content of xanthophyll cycle pigments and significantly increases maximum efficiency of Photosystem Ⅱ under light adapted,efficiency of Photosystem Ⅱ,electron transport rate,photochemical reflectance index,activity of catalyse,content of chlorophyll a,content of chlorophyll a and chlorophyll b,and significantly reduces the content of malondialehyde,but has little influence on photochemical quenching or non-photochemical quenching,content of carotenoid.We can conclude that,the non-photochemical quenching are inhibited by and xanthophyll cycle are boosted by synergistic stresse of salt and high light intensity,resulting in irreversible photoinhibition and significant reduced photochemical efficiency.Selenite treatment relieved photoinhibiton and improve photochemical efficiency of rice seedlings exposed to stresses resulting from reducing extent of xanthophyll cycle and promote relaxation of non-photochemical quenching.