Effect of Polyamine on Grain Filling of Winter Wheat and Its Physiological Mechanism

Grain filling in wheat is an important agronomic trait affecting grain weight.Polyamine is a plant growth regulator that is proved to participate in regulation of grain filling in rice and maize.In the present study,Zhoumai 18 and Xinong 538 were used to investigate the effect of polyamine on grain weight during filling process;besides,the photosynthetic characteristics,activities of antioxidant enzymes(SOD,POD,and CAT),malondialdehyde(MDA) content in flag leaves,and ethylene(ETH) content in grains were also measured for explaining the mechanism of such effect.The results showed that external spermidine(Spd) and spermine(Spm) significantly promoted grain filling,while external putrescine(Put) had no significant effect on grain filling.External Spm and Spd increased chlorophyll content,activities of antioxidant enzymes,and photosynthetic rate,but decreased MDA content in flag leaves and ETH level in grains.Therefore,we conclude that the effects on grain filling vary with polyamine species,and may relate to photosynthesis and senescence of leaves and ETH level of grains.