Putrescine exogenous application alleviates oxidative stress in reproductive tissue under high temperature in rice

Polyamines accumulate under high temperature (HT) stress and play a vital role in improving stress tolerance in plants. Present study was conducted in four contrasting rice genotypes viz. Nagina22 (N-22), IR-64, Pusa Rice Hybrid-10 (PRH-10) and Pusa Basmati 1121 (PB-1121) to analyse the effect of exogenous Putrescine (Put) application in alleviating HT stress effects at reproductive stage. Rice plants were exogenously treated with two concentrations of Put (2.5 and 3.5 mM) at pre-anthesis stage and exposed to HT stress (38.6 ± 0.84 °C). HT exposure during flowering caused significant decrease in flag leaf’s photosynthesis rate, membrane stability, spikelet fertility (SF) and panicle grain yield. Exogenous Put application improved its endogenous level in the leaf and panicle tissues. Its application has enhanced the cells antioxidant capacity, has decreased hydrogen peroxide (H2O2) concentration and membrane lipid peroxidation together with improvement in membrane stability. However, effect of HT stress on SF and panicle grain yield was non-significantly ameliorated by this increase in endogenous Put concentration. This study concludes that exogenous application of Put may enhance cellular tolerance under HT stress by lowering the oxidative stress in terms of H2O2 and membrane peroxidation and improves membrane stability but may not fully alleviate the HT stress effects on spikelet tissues. It is suggested that further attempts can be made either through application of higher concentrations of Put or by enhancing its level using transgenic/molecular approaches in spikelets. Alternatively, genotypes with naturally higher polyamines concentrations in the spikelets may be identified and tested for their response under HT stress.