Exogenous melatonin mediates physiological and photosynthetic response mechanisms of maize cultivars under waterlogging stress

BACKGROUND: Global warming has led to increased rainfall and waterlogging in some areas, which poses a threat to global food security. RESULTS: The results showed that the negative effects of different waterlogging stresses on different maize were mitigated by spraying exogenous melatonin, which maximally increased POD activity in C 7- 2 maize leaves, SOD activity in ZD 958 maize leaves and CAT activity in Z 58 maize leaves, which in turn reduced MDA in ZD 958 maize leaves and proline content in Z 58 maize leaves, increased antioxidant enzyme activities, and slowed down the damage of the stress on the plant body. Moreover, exogenous melatonin maximally increased chlorophyll b in C 7- 2 maize leaves, chlorophyll and chlorophyll a content of Z 58 maize leaves under CF2 stress, which indicated that melatonin could alleviate the integrity of chloroplast membranes by stress. Meanwhile, exogenous melatonin also increased the stomatal conductance, interstitial carbon dioxide concentration, and transpiration rate of ZD 958, and raised the net photosynthetic rate of C 7 - 2, which enhanced photosynthesis, increased the content of carbohydrates, and directly provided an energy source for the maize growth and metabolism, providing energy source and maintaining cell activity. CONCLUSIONS: In conclusion, this study deeply explored the different regulatory effects of melatonin on maize varieties with different genetic backgrounds, showing that waterlogging stress had the least effect on Z 58 maize while melatonin had the best effect on alleviating the damage of ZD 958 under waterlogging stress, followed by Z 58, and lastly C 7 - 2, which deepened the understanding of the molecular mechanism of melatonin in alleviating adversity stress, and provided an opportunity to investigate the mechanism of melatonin action and to optimise its application in agricultural production.