Effect of high temperature on leaf senescence and related enzymes of grain starch synthesis in stay-green wheat after anthesis

Abstract

Aims Our objectives were to explore the influence of high temperature on enzymes of grain starch synthesis in stay-green wheat(Triticum aestivum) and reveal heat tolerance in stay-green wheat.Methods We used the stay-green wheat 'Wm8' and 'Ym66' and the control varieties 'XY6' and 'XY22' as ex-perimental materials.A warming cover of plastic film was used to carry out the high-temperature treatment.After anthesis,we measured green leaf number,chlorophyll content,malonaldehyde(MDA) and membrane permeabil-ity,as well as the activities of the enzymes of grain starch synthesis were measured.Important findings High temperature after anthesis promotes rapid leaf senescence.For all four varieties,the green leaf number and chlorophyll content significantly decreased,but the MDA content and the relative electric conductivity increased markedly.The stay-green wheat varieties had higher green leaf number and chlorophyll content and lower MDA content and relative electric conductivity than the control cultivars after high temperature treatment.In grains,the activities of the enzymes of grain starch synthesis(sucrose synthase,SS;adenosine di-phosphate glucose pyrophosphorylase,AGPP;and soluble starch synthase,SSS) in all four varieties decreased after high temperature treatment.But activities of these enzymes in the stay-green wheat were also higher than those in the control wheat,suggesting that it was beneficial for the starch accumulation in grain of stay-green wheat under high temperature.Among the three enzymes,a significant difference existed in SSS activity between the high temperature treatment and the control,and activities of the above three enzymes were positively and sig-nificantly correlated with grain-filling rate(r = 0.905,0.419 and 0.801,respectively),so they play a key role in starch synthesis in the grain of wheat.Above all,the stay-green wheats have better resistance to high temperature than other varieties,and they have strong photosynthesis capacity and higher grain weight.Hence,breeding new cultivars with the stay-green characteristic would reduce the influence of high temperature stress during grain fill-ing in wheat production.