Abstract:

Low temperature stress seriously affects seed germination of cotton. In order to clarify the regulation of melatonin on cotton seed germination under low temperature stress, the sea island cotton variety ‘Xinhai 41’ was used as test material in this study. The effect of different melatonin concentration treatments on germination characteristics, antioxidant enzyme activity, MDA and hydrogen peroxide content of cotton seeds was analyzed under low temperature stress (15℃). The results showed that the germination rate, germination potential and germination index of cotton seeds were reduced by 17.41%, 13.52% and 74.96%, respectively, and the embryonic root length was reduced by 40.35%, while SOD, POD and CAT activities were slightly increased, and MDA and H₂O₂ contents were increased under low temperature compared with the normal temperature control. The low concentrations of melatonin (10 μmol/L and 20 μmol/L) treatments significantly increased the germination potential, germination rate and germination index, as well as embryonic root length, enhanced the activities of antioxidant enzymes and reduced the production of MDA and H₂O₂ in cotton seeds under low temperature stress, in which the SOD, POD and CAT activities increased after 20 μmol/L melatonin treatment compared with the low temperature control by 3.53%, 29.47%, and 3.45%, and MDA and H₂O₂ contents were reduced by 13.93% and 8.08%, respectively, after 20 μmol/L melatonin treatment compared with the low temperature control. The appropriate concentration of melatonin treatment could effectively alleviate the damage of low temperature stress on cotton seed germination and enhance the low temperature stress of seeds, among which 20 μmol/L melatonin treatment has the best effect.

Key words: melatonin, low temperature stress, cotton, antioxidant enzyme activity, germination characteristics