Analysis on Photosynthesis Mechanism of Resistance to High Temperature during Grain Filling in Winter Wheat(Triticum aestivum L.)

Two winter wheat cultivars,Jimai 22 with high resistance to high temperature and Jimai 20 with sensitive to high temperature,were planted in 2012-2014 crop cycles to investigate the structural photosynthetic responses to high temperature during the grain filling stage.Tiller number,ear number,fertile percentage and yield were analysed.Net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2concentration(Ci),transpiration rate(Tr),photochemical fluorescence quenching coefficient(qP),original light energy conversion efficiency(Fv/Fm),actual photochemical efficiency of PSII(ΦPSII),non-photochemical quenching coefficient(NPQ)and ultra-structure at filling period under field temperature of 30~36℃ were investigated.The results showed that under high temperature during the grain filling stage,compared with Jimai 20,Jimai 22 showed closely granum,undamaged membrane structure,Pn,Tr,Gs,ΦPSIIand qPof its flag leaf increased 14.0%,22.5%,57.8%,7.9% and 6.1%,respectively.There were no significant changes in Fv/Fm.While NPQ decreased by 18.9%,and yield increased by 1.4%.In conclusion,under high temperature during grain filling stage,Jimai 22 showed chloroplast in good condition,limited loss of light energy by heat dissipation,high efficiency of light energy and photosynthetic rate and better assimilation,so yield was increased.