Effects Of Betaine (GB) On Regulation Of Chlorop Lasts D1Protein And Function Of PSⅡ In Wheat Leaves Under High Temperature And Irradiance Stress

In Chinaˊs Huanghuai winter wheat zone, cross-stress of heat andhigh irradiance occurs frequently, which results in damage to photosyntheticapparatus, decline of photosynthesis in leaves, retard of seed growth and decrease ingrain yield. In this paper we studied the regulating effects of exogenous glycinebetaine on the content of D1protein in wheat leaf thylakoid membrane、chlorophyll fluorescence parameters、 photosynthetic rate、 antioxidant enzymesactivity and cell membrane stability. The aim was to provide the failure mechanism ofphotosynthetic apparatus caused by high temperature and irradiance stress, providedscientific basis to enhance plant resistance and served for practice.In this paper the experiments materials we studied were AiKang58, inpustulation period, we sprayed foliage by distilled water、0.5mmol/L GB、1mmol/L GB、2mmol/L GB、3mmol/L GB，after continuous spraying for threedays, we setted the wheat under the heat and high irradiance stress for two hours, andthen switch the dim light, sampled the leaves for measuring the content of D1proteinin thylakoid membrane, chlorophyll fluorescence parameters,photosynthetic rate,antioxidant enzymes activity and cell membrane stability before threat, after threatand recovered form threat.Results indicated that under high temperature and irradiance, the content of D1protein decreased, the activity of SOD and POD decreased, the value of Fv/Fm, qPand Pn decreased, the value of NPQ increased, the contend of MDA increased, thevalue of relative conductivity increased. Results explained that under hightemperature and irradiance, the wheat had encountered harm, normal operation of PSⅡwas broken, photoelectron transfer suffered suppression, cause elevated reactiveoxygen species and antioxidative enzyme activity inhibited.After recovered in dim light, compared to high temperature and irradiance stress,the content of D1protein increased, the activity of SOD and POD increased, the valueof F_v/F_m, qP and Pn increased, the value of NPQ decreased, the contend of MDA decreased, the value of relative conductivity decreased. Under the dim light, the wheatconsumed excessive energy during photorespiration to alleviated the harm caused byhigh temperature and irradiance stress.Results indicated that GB sprayed on leaves inhibited effectively the netdegradation of D1protein, maintained higher activity of SOD and POD, abirritatedthe oxydic impair caused by high temperature and irradiance stress, reduced the levelof cell-damaging free radicals, and then maintain a higher optimal/maximalphotochemical efficiency of PS Ⅱin the dark(F_v/F_m), Photochemical quenching(qP),reduced the damaging of reactive center in PSⅡ. After dark-recover, the content ofD1protein rapidly Increasied, stabled the structure of PS Ⅱreaction center, the effecton repairing photosynthetic apparatus was saliency, guaranteed the photosyntheticapparatus function well. The concentration of GB at1mmol/L was best than the restfor the wheat to resist the stess caused by high temperature and irradiance stress.