Effects of polyamines on agronomic traits and photosynthetic physiology of wheat under high temperature stress

Abstract

Two spring wheat varieties were used to study alleviating effects of exogenous spermine (Spm) and spermidine (Spd) on agronomic traits and photosynthesis under high temperature treatment (HT). Our results showed that HT significantly decreased grain mass per panicle of heat-resistant variety (XC 6) by 25% and heat-sensitive variety (XC 31) by 32%. After HT, i.e., at 13 d after flowering, the decrease in net photosynthetic rate of XC 6 (38%) was lower than that of XC 31 (53%); the reason for this was related to XC 6, which could maintain correspondingly normal chlorophyll content (Chl), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration. Exogenous Spm and Spd could increase relative water content, Chl, gs, E, the maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, antenna conversion efficiency, and photochemical quenching coefficient of flag leaves under HT. Our results indicated that the heat resistance of XC 6 is better than that of XC 31 and exogenous Spm and Spd could alleviate the heat injury of photosynthesis of wheat flag leaves.