Effects of High Temperature Stress on Photosynthesis and Antioxidant Sys-tem of Cary a cathayensis
In order to understand the effects of high temperature stress on photosynthesis and antioxidant system of hickory(Carya cathayensis Sarg.)seedlings,and to provide reference basis for the cultivation of hickory in high temperature season,the changes of gas exchange and chlorophyll fluorescence,as well as antioxidant enzymes and antioxidants were measured in hickory seedlings at different temperatures(25 ℃,30 ℃,35 ℃,40 ℃)in this study.The results showed that the net photosynthetic rate(Pn)and stomatal conductance(Gs)were increased first and then decreased with the increase of temperature,but the intercellular CO2 concentration(Ci)was increased continu-ously.The initial fluorescence(Fo)and non photochemical quenching(NPQ)of hickory were increased signifi-cantly under high temperature stress,while the maximum photochemical effiiciency(Fv/Fm)and electron transfer rate(ETR)were decreased significantly above 35 ℃.Under high temperature stress,the contents of hydrogen per-oxide(H2O2)and malondialdehyde(MDA)increased significantly.However,at 25 ℃～35 ℃,the activities of su-peroxide dismutase(SOD),catalase(CAT),peroxidase(POD),ascorbic acid peroxidase(APX),glutathione perox-idase(GPX)and glutathione reductase(GR),as well as the contents of reduced glutathione(GSH)and oxidized glutathione(GSSG)increased with the increase of temperature,but decreased significantly at 40 ℃.These results indicated that the PSⅡ reaction was damaged and the electron transfer rate was decreased in hickory seedlings un-der high temperature stress,which reduced the photosynthetic rate,and that the protective effects of heat dissipa-tion and antioxidant system were quickly induced.However,under high temperature stress of 40 ℃,the antioxi-dant system was damaged,which exceeded the tolerance threshold of hickory seedlings.
HickoryHigh temperature stressPhotosynthesisAntioxidant enzymes
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维普
