Seed priming alleviated salt stress effects on rice seedlings by improving Na+/K+ and maintaining membrane integrity

The potential of seed priming by different chemicals on alleviation of growth inhibition of rice (Oryza sativa L.) seedlings under salt stress was investigated. A preliminary experiment using 10 seed-priming chemicals including NaCl, KCl, CaCl2, KNO3, ascorbic acid (AsA), mannitol, polyethylene glycol (PEG6000), sorbitol, wood vinegar and distilled water revealed that mannitol, KNO3 and wood vinegar were more effective than the others in alleviating salt-induced growth inhibition of 10- day-old seedlings. Various concentrations of mannitol (1, 2 and 3%), KNO3 (0.25, 0.5 and 0.75%) and wood vinegar (1:1000, 1:300 and 1:100 dilutions) were subsequently used to prime rice seeds to investigate the effects on mitigation of salt-induced growth inhibition and modulation of physiological responses of 4-week-old rice plants grown in a hydroponic solution. All tested concentrations of mannitol, KNO3 and wood vinegar resulted in seedlings with significantly higher dry weights than those grown from non-primed and hydroprimed seeds under both controlled and saltstressed (150 mM NaCl, 7 days) conditions. Under salt stress, enhanced growth of seedlings raised from seeds primed with all three chemicals was attributable to greater membrane stability, higher chlorophyll content and lower Na+/K+ ratio.