Promotion of 5-aminolevunlinic acid on seed germination of watermelon (Citrullus lanatus)under salt stress

Salinity usually prohibits seed germination and seedling growth. How to promote seed germination and seedling growth has been an important agricultural technique in saline regions. In the work, it was found that 75 to 125mmol/L NaCl treatment significantly inhibited seed germination and seedling growth of watermelon. Treatment with 15 to 30 mg/L 5-aminolevulinic acid (ALA) could promote seed germination and seedling growth under 125 mmol/L NaCl stress, companied with the increased activities of superoxidate dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), but the decreased activity of lipoxygenaze (LOX) and a lower level of MDA in hypocotyls and radicles. Addition with ascorbic acid (AsA), an inhibitor of POD activity, in a concentration of 1 g/L might eliminate the promotion of ALA on seed germination, which suggested that the promotion of exogenous ALA treatment on germination under salt stress might be associated with the increased activities of the antioxidant enzymes, especially POD.