Effects of exogenous melatonin on growth and physiological characteristics of tartary buckwheat seedlings under drought stress

【Objective】 To explore the effects of exogenous melatonin(MT) on the growth and physiological characteristics of tartary buckwheat seedlings under drought stress, and to provide a theoretical reference for the basic research and applied research of the drought resistance physiological of tartary buckwheat.【Method】 Chuanqiao 2 was used as the test material in this study.Under 15% polyethylene glycol(PEG) simulated drought stress, there were 5 treatments including CK(distilled water), PEG, PEG+50 μmol/L MT, PEG+100 μmol/L MT and PEG+200 μmol/L MT. Measured the fresh and dry weight of the above-ground part, the fresh and dry weight of the underground part, photosynthetic pigment, antioxidative enzyme activity and content of osmotic regulators of tartary buckwheat seedlings under different treatments. The entropy weight TOPSIS analysis method and the gray correlation degree analysis were used to comprehensively evaluate the physiological indexes of tartary buckwheat seedlings under the drought stress of exogenous MT treatment.【Result】 Spraying different concentrations of MT could alleviate the inhibition of drought stress on the growth of tartary buckwheat seedlings, and the effect of spraying 100 μmol/L MT was better. Compared with the PEG treatment, the fresh weight of the aboveground part, the fresh weight of the underground part, the dry weight of the aboveground part, the dry weight of the underground part and the root-shoot ratio of tartary buckwheat seedlings were increased by 18.6%, 38.6%, 18.1%, 136.4% and 96.7%, respectively. The contents of chlorophyll a, chlorophyll b, carotenoids and total chlorophyll respectively increased by 35.0%, 19.6%, 48.3% and 30.8%, catalase(CAT) and peroxidase(POD) activities respectively increased by 27.1% and 74.4%, malondialdehyde(MDA) content decreased by 45.9%, proline and soluble sugar content respectively increased by 11.07% and 50.2%. In addition, the results of grey correlation analysis showed that exogenous MT mainly reduced the damage to tartary buckwheat seedlings caused by drought stress by increasing POD activity, soluble sugar and carotenoid content.【Conclusion】 100 μmol/L MT can effectively alleviate the inhibitory and damage effects of drought stress on the growth of tartary buckwheat seedlings, and improve the drought resistance of tartary buckwheat seedlings.