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.