Abstract: The effects of melatonin-soaking seeds on physiological and biochemical characteristics of rice seedlings under submergence stress. Three concentration treatments of melatonin(10, 100, 1 000 μmol/L) were arranged. The agronomic traits such as Mesocotyl length, coleoptile length, shoot length, fresh weight and survival rate, and the physiological and biochemical indexes such as enzyme activity of peroxidase(POD), superoxide dismutase(SOD), catalase(CAT) and malondialdehyde(MDA) content were measured.The results showed that low concentration MT-soaking could alleviate the stress and high concentration MT-soaking aggravate the toxicity. Compared with short mesocotyl cultivars Huahang 31 and DH4040, long mesocotyl cultivars Ezhong 4 and DH4038 had higher survival rates under submergence stress. Among the four cultivars, Huahang 31 had the best effect of MT-soaking seeds in two treatments, i.e. 10,100 μmol/L MT. The treatment of 100 μmol/L MT-soaking seeds could greatly improve the seedling survival rate of all cultivars. When the MT-soaking concentration increased to 1 000 μmol/L, the survival rate of all cultivars was inhibited. MT-soaking seeds could reduce MDA content, increase POD, SOD and CAT activities, and promote agronomic traits such as mesocotyl length, coleoptile length, bud length and fresh weight, while 100 μmol/L MT-soaking seeds could also promote the related agronomic traits. While 1 000 μmol/L MT-soaking could also promote the related agronomic traits and enzyme activity,but the survival rate decreased significantly.It was concluded that soaking-seeds with appropriate concentration of melatonin could improve the vigor and emergence rate of rice seedlings under submergence stress, and significantly reduce the toxicity of submergence stress on rice seedlings.

Key words: Rice, Mesocotyl, Melatonin, Soaking-seed, Submergence stress

CLC Number: 

• S511