Osmolyte accumulation plays important roles in the drought priming induced tolerance to post-anthesis drought stress in winter wheat ( Triticum aestivum L.)

Winter wheat were subjected to moderate drought priming before anthesis and then to a severe drought stress after anthesis. The plant morphology, osmolyte accumulation related traits in both leaves and roots were analysed during the priming, the post-anthesis drought stress, and the recovery from the drought stress. The primed plants (PD) showed lower reduction in leaves dry weight and grain yield, higher maximum root length, compared with non-primed plants (CD). The PD maintained lower osmotic potential related to the higher contents of leaf proline and sucrose. The higher proline content could be resulted from the improved activities of Δ 1 -pyrroline-5-carboxylate synthetase (P5CS) due to the up-regulated expression of P5CS. The higher sucrose content correlated with the up-regulated expression of gene encoding the sucrose-phosphate synthetase. No significant differences between PD and CD in contents of proline and sucrose of root were found. Meanwhile, the PD showed higher activities of antioxidant enzymes, which contributed to lower cell membrane peroxidation level as compared with the CD in both leaves and roots under drought stress. It is concluded that the enhanced tolerance to drought stress in primed plants were related to the enhanced osmolyte accumulation to maintain a better plant water status, which further resulted in relatively higher photosynthesis, lower oxidative stress damage and grain yield under the post-anthesis drought stress.