Hydrogen Peroxide Promotes Terminal Heat Stress Recovery in Wheat by Strengthening Leaf Physiological Functioning

Wheat crops are highly sensitive to high temperatures during reproductive and grain filling phases. This study explored how hydrogen peroxide (H 2 O 2 ) protects grain yield formation in wheat crops exposed to heat during different developmental phases. Two wheat genotypes, Ujala-16 and Anaj-17, of varying heat tolerances, were subjected to heat stress (32 °C/20 °C) at pre-anthesis, anthesis, and post-anthesis stages under glasshouse and field conditions. Before heat stress treatment, the plants were sprayed with 60-ppm hydrogen peroxide (H 2 O 2 ). Post-stress changes in leaf physiology were studied to understand the heat recovery mechanism. Despite significant genotypic variations, high temperature damaged leaf physiology and grain yield of both studied wheat genotypes. On average, high temperatures during any developmental phase caused more damage to Anaj-17 than to Ujala-16. Compared with the control, the plants heated during pre-anthesis, anthesis, and post-anthesis produced 44%, 35%, and 25% lesser grains yield per spike (averaged across genotypes and experiments), respectively. In contrast, post-anthesis-stressed plants produced the smallest grains compared to those heated during pre-anthesis or at anthesis. Compared with the control, H 2 O 2 -treated plants sustained significantly higher leaf chlorophyll and net photosynthetic rate by protecting cellular membranes from heat injury. Under hot conditions, hydrogen peroxide-treated plants yielded 17% more grains (averaged across the developmental phases and genotypes) than control plants. Our study suggests wheat performance can be improved through exogenous H 2 O 2 application, particularly during terminal heat stress.