Effects Of High Temperature And Strong Light On D1Protein、Deg1Proteas And PSⅡ Performance In Chloroplasts Of Wheat Leaves And The Protective Role Of Salicylic Acid

Wheat(Tritivum aestivum, L) is the main food crops in northern China, Itsproduction not only impacts people’s living standards but also impacts state economicdevelopment directly. In recent years, wheat production faces the challenge of hightemperature stress because of the greenhouse effect. Wheat filling stage is not only therush hour of a variety of diseases and insect pests, but also the key period of grainnumber and grain weight. Therefore, the photosynthesis of wheat filling stage got a lotof attention recently. In this paper, the influence of SA on the D1protein, Deg1protease, Chlorophyll fluorescence parameters, Electronic transfer rate, antioxidantactivity, cell membrane stability and PSII function of high temperature, strong lightwere studied. The aim is to understand the protective mechanisms of exogenous SAon the photosynthetic and provide experimental foundation for taking resistancemeasureUsing wheat variety “Aikang58” as material, the experiments were conducted onexperimental farm of Henan Agricultual University. Wheat seeds were planted in potsand sand plates. Foliar sprayings of0.3mmol·L-1SA were done on the20th day afteranthesis (grain filling stage) in field of pot experiments or the fourth leaf stage in sandculture. Water was sprayed in contrast. Then the plants were exposed to irradiance of1600μmol·m-2·s-1provided by1000W tungsten lamp and temperature of38℃for2hours，dark recovery3h processing(temperature of light：25℃， PFD为600umol·m-2·s-1).Take the flag leaf of the treatment plant as test materials, parts of themare used to test the physiological indexes of chlorophyll fluorescence parameters andphotosynthetic rate, the rest was conducted liquid nitrogen freezing immediately andused for the determination of D1protein and Deg1protease. The main results asfollows:1. The modulatory effect of exogenous SA on wheat thylakoid D1protein content andDeg1protease on the condition of high temperature and strong light stress. High temperature and strong light stress lead to degradation of D1proteins andDeg1protease, the content decrease obviously, PS Ⅱi s damagedtoo. In recoverystage, both the content of D1proteins and Deg1protease had some rise but still lowerthan the level prior the stress. Compared to the pretreatment of blade with water (W),SA maintains the higher content of D1proteins and Deg1protease, reduces thephotoinhibition of wheat in adversity conditions, and effectively protects the responsecenter of PS Ⅱfrom damaging, maintains effective operation organization of plantphotosynthesis.2. Effects of exogenous SA on PSII functioning under high temperature and stronglight stressUnder high temperature and strong light stress, NPQ is increased, but the wholechain electronic transfer rate, PSII electronic transfer rate, Fv/Fm, φＰＳⅡ, qP and Pnare reduced.After3h of recovery under moderated temperature and normal illumination, NPQis significantly reduced, while the whole chain electronic transfer rate, PSII electronictransfer rate, Fv/Fm, φＰＳⅡ, qP and Pn are ascended obviously, this suggests that PSⅡ suffers reversible damage. Compared to the pretreatment of blade with water (W),SA not only have the effect of maintaining higher whole chain electronic transfer rate,PSII electronic transfer rate,Fv/Fm,φＰＳⅡ,Qp,Pn and lower NPQ, but also acceleratingthe increase of the electronic transfer rate, chain PSII electronic transfer rate, Fv/Fm,φＰＳⅡ, qP, Pn and the reducing of NPQ of recovery thus reduces the damage level ofthe photosynthetic institutions, maintains the stability of response center structure ofPS Ⅱand higher turnover rate.3. Impacts of exogenous SA on the antioxidant activity and cell membrane stability ofwheat leaves under high temperature and high light stressUnder high temperature and high light stress, membrane stability lessens andmembrane fluidity increases. The activity of antioxidant enzymes APS, CAT and GRall decreases while the MDA’s accumulation, the content of H2O2, the concentrationof superoxide anion radical the relative conductivity increases. Compared with theleaves preprocessed by water, the leaves preprocessed by SA have higher activity ofSOD, APX, CAT, GR, lower content of H2O2and lower concentration of superoxideanion radical, the accumulation of MDA was inhibited, and the relative conductivityincreases.