Peer review

Drought is a limiting factor for wheat production. Nitric oxide (NO) and hydrogen peroxide (H2O2) are key signalling molecules produced in response to drought stress. Drought priming is a promising strategy for enhancing drought tolerance. Here, the roles of NO and H2O2 in drought priming were investigated. The results showed that the scavengers of NO or H2O2 reduced the effects of priming‐induced tolerance to drought stress during seedling and grain filling stages. Drought priming induced the production of H2O2 and NO, suggesting that H2O2 and NO were involved in priming‐induced drought tolerance and that the synthesis of H2O2 could be related to respiratory burst oxidase homologues (RBOH). Further, nitrate reductase (NR) activity was not the unique source for NO production. The elevated production of NO in the primed plants was blocked by scavengers of both H2O2 and NO, whereas the H2O2 concentration was not affected by a scavenger of NO. Osmolyte accumulation induced by drought priming was partly inhibited by the removal of NO, but was higher than in non‐primed plants. NO worked downstream of H2O2‐mediated the accumulation of proline and glycine‐betaine in primed plants under drought stress during grain filling. The results increase our understanding of the roles of H2O2 and NO in priming‐induced drought tolerance in wheat.

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