Response Of Chlorophyll Fluorescence And AsA-GSH Cycle To Acid Rain And High Temperature In Osmanthus Fragrans Var. Semperflorens

In order to explore the effect of acid rain,high temperature and co-stress.In this experiment,Osmanthus.fragrans var.‘Semperflorens'as experimental materials,and the method of artificial spraying by pot was adopted,simulated the different gradient of acid rain?control pH5.6,light pH4,middle pH3 and high pH2?and high temperature stress.By measuring the changes of photosynthetic pigmentcontent,Chlorophyllfluorescenceparameters,reactiveoxygenspecies?ROS?,malondialdehyde?MDA?content,antioxidant and antioxidant enzymes in O fragrans var.‘Semperflorens'leaves.mainly coming to the following conclusions:1?As the pH of acid rain decreases,the chlorophyll content in O fragrans var.‘Semperflorens'increasede,but the difference was not significant?P>0.05?.In high temperature and acid rain stress,chlorophyll content also has the same trend,but the values are with simulated acid rain pH value decreased,but compared to the control group are on the rise,the differences was no significant either?P>0.05?.In acid rain stress,heat dissipation quantum ratio??Do?,specific fluxes or activities expressed per reaction center?QA in can be reduced state,units of PS II reaction center of activity?and reaction center density,specific fluxes or activities expressed per reaction center?the activity of the unit cross-sectional area?,performance index and the driving force with the increase in the intensity of acid rain increases.The quantum yield/energy distribution ratio decreases with the increase of acid rain intensity.Under high temperature acid rain stress,the opposite trend was presented.These results suggest that acid rain and high temperature had the effect of inhibiting the photosynthetic performance of the sweet scented O.fragrans var.‘Semperflorens'leaves.2?As the pH of acid rain decreases,The content of H₂O₂,SOD activity,MDA and superoxide anion in O.fragrans var.‘Semperflorens'leaves were increased,CAT activity,POD activity and soluble protein content increased first and then decreased.In high temperature and acid rain stress,H₂O₂ content,superoxide anion content,soluble protein content increased,the rest are reduced after the first rise.These results suggest that by improving osmanthus antioxidant activity of the enzyme to resist acid rain,high temperature environment.3?In high temperature and acid rain stress,AsA,GSH,oxidized glutathione?GSSG?content and AsA/DHA,GSH/GSSG value and ascorbic acid and catalase?APX?,dehydroascorbate reductase?DHAR?,Monodehydroascorbate reductase?MDHAR?,glutathione reductase?GR?activity decreased,dehydroascorbic acid?DHA?content increased gradually.The surface of the blade can keep the AsA-GSH cycle efficiency is higher in stress period,can effectively inhibit the activity of oxygen?ROS?accumulation,which may be one of the reasons for its better resistance to acid rain and high temperature.In conclusion,after high temperature and acid rain stress,the photosynthetic performance was inhibited to some extent,the efficiency was was decreased and ROS accumulation was achieved,O.fragrans var.‘Semperflorens'can quickly start the antioxidant defense system to improve the non enzymatic antioxidant content and antioxidant activity,which can maintain the balance of ROS,thus maintaining a high AsA-GSH cycle efficiency,showed a strong tolerance to high temperature and acid rain stress.