Induction of chilling tolerance in wheat during germination by pre-soaking seed with nitric oxide and gibberellin

Chilling depresses seed germination and seedling establishment, and is one major constraint to grain yield formation in late sown winter wheat. Seeds of winter wheat (Triticum aestivum L.) were separately pre-soaked with sodium nitroprusside (SNP, as nitric oxide donor) and Gibberellic acid (GA(3)) before germination and then germinated under low temperature. SNP and GA(3) pre-treatment increased seed germination rate, germination index, weights and lengths of coleoptile and radicle, while they decreased mean germination time and weight of seeds germinating under low temperature. Exogenous NO and GA(3) increased seed respiration rate and promoted starch degradation along with increased amylase activities. In addition, efficient antioxidant systems were activated by NO, and which effectively reduced concentrations of malondialdehyde and hydrogen peroxide (H2O2). Seedling growth was also enhanced by exogenous NO and GA(3) as a result of improved seed germination and maintenance of better reactive oxygen species homeostasis in seedling growing under chilling temperatures. It is indicated that exogenous NO was more effective than GA(3) in alleviating chilling stress during seed germination and seedling establishment in wheat.