Influence of salicylic acid pre-treatment on emergence and early seedling growth of cucumber (Cucumis sativus)under salt stress

Salicylic acid (SA) is a common, plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was therefore conducted to test whether the application of SA at various concentrations (0, 0.25, 0.50 or 1.0 mM) through a seed-soaking method would protect cucumber (Cucumis sativus L.) seedlings subjected to salt stress. After soaking, seeds were sown in plastic trays filled with washed fine sand. The trays were then placed in the greenhouse and watered with different NaCl solutions (0, 50, 100 and 150 mM), for a period of 4 weeks. SA improved the majority of physiological (relative leaf chlorophyll content, leaf relative water content and chlorophyll fluorescence ratio) and morphological parameters (total emergence, mean emergence time, shoot and root dry weights) of cucumber seedlings subjected to salt stress. SA improved the injuries caused by salt stress by promoting K+ accumulation and preventing increases in leaf electrolyte leakage and Na+ contents of leaves and roots. The best protection appeared to be obtained from SA applied by seed-soaking method at 1.00 mM.