Promotive Effect of Priming with 5-Aminolevulinic Acid on Seed Germination Capacity, Seedling Growth and Antioxidant Enzyme Activity in Rice Subjected to Accelerated Ageing Treatment

Seed deterioration by ageing caused by natural and artificial treatments lowers germinability and viability. Seed priming is a technique used to relieve seed deterioration from ageing. We evaluated the effect of seed priming with 5-aminolevulinic acid (ALA) at various concentrations on the seed germination capacity, seedling growth, antioxidant enzyme activities, and lipid peroxidation in the rice seedling cultivar Pathum Thani 1 with or without exposure to artificial ageing treatment. Seeds were subjected to accelerated ageing treatment by exposure to high relative humidity and high temperature conditions for 84 hr (aged seeds). The shoot length was significantly reduced and the injury index and H2O2 formation were increased in the seedlings emerged from the aged seeds. Priming of the aged seeds with 0.5 mu g mL(-1) ALA significantly enhanced the seed germination capacity and seedling relative growth rate to values higher than those obtained by priming with water (hydropriming). However, there was no significant difference in superoxide dismutase, peroxidase and ascorbate peroxidase activity as compared with hydropriming. In the seeds not given ageing treatment priming with ALA significantly increased the superoxide dismutase and peroxidase activities in the seedlings by 144% and 282%, respectively, as compared with the hydropriming treatment. Seed priming with ALA at 0.2 mu g mL(-1) significantly increased the relative growth rate of seedling and lowered seedling water content as compared with the values without priming or with hydropriming. Seed priming with ALA was confirmed to enhance rice seed germination capacity, seedling growth, and antioxidant enzyme activity in rice seedlings.