Seed osmopriming invokes stress memory against post-germinative drought stress in wheat (Triticum aestivum L.)

Seed osmopriming improves gemination performance of seeds under normal and stressed environmental conditions, a feature possibly associated with 'stress memory'. To investigate whether seed osmopriming could develop tolerance to drought stress during post-germinative stages of wheat (Triticum aestivum L.), we primed the seeds of a drought-sensitive cultivar (Yangmai 16) by following a pre-standardized protocol of -0.9 MPa PEG at 18 degrees C for 30 h, and then dried at room temperature. The plants from unprimed and primed seeds were simultaneously exposed to a severe drought stress during tillering (Feekes 2 stage) and jointing (Feekes 6 stage), respectively, and we investigated the changes in leaf water relations, photosynthetic processes, lipid peroxidation, antioxidative defense, and relative growth rate during drought. Moreover, grain yield traits were recorded at maturity. Drought stress caused a reduction in leaf water potential, relative water content, net photosynthesis, quantum yield, and contents of chlorophylls and carotenoids; however, the decrease in these traits was less in primed-seed plants as compared to unprimed-seed plants. During drought stress, primed-seed plants showed lower reactive oxygen species formation and lipid peroxidation, and higher activities of catalase, ascorbate peroxidase, and glutathione reductase than unprimed-seed plants. Seed osmopriming treatment allowed wheat plants to maintain a greater relative growth rate during the drought period, resulting in higher dry matter and grain yield production relative to non-priming treatments. It was concluded that seed osmopriming resulted in long-lasting stress memory, which stabilized plant growth and productivity by altering physiological and biochemical responses to post-germinative drought stress in wheat.