Effects of phenolic acids on watermelon seed germination,seedling growth,and physiological and biochemical properties

The experimental results showed that 4 phenolic acids(coumaric acid,cinnamic acid,ferulic acid and vanillic acid) from the decay product and root exudates of watermelon had significant effects on watermelon seed germination and seedling roots' physiological activities.The phenolic acids had an inhibiting effect on the seed germination and the effect became greater as the concentration increased.When the concentration of phenolic acids reached 800 mg/L,the effect of cinnamic acid was the greatest while that of vanillic acid was the least,in which the seed germination rates decreased by 52.6%and 37.9%respectively in comparison with the control;Cinnamic acid had the greatest inhibiting effect on the radicle and plumular axis lengths of watermelon while vanillic acid had the least.In the roots of watermelon seedlings,the activities of dehydrogenase and SOD gradually reduced but the activities of POD and PPO increased as the concentration of phenolic acids increased.