Exogenous Glycinebetaine Mediated Tolerance Mechanism Regulates the Contrasting Responses to Drought and Flooding Stresses in Leaf Physiochemical Attributes and Growth of Maize

Background Flooding and drought are the two most devastating natural hazards limiting maize production. Exogenous glycinebetaine (GB), an osmotic adjustment agent, has been extensively used but limits focus on its role in mitigating the negative effects of different abiotic stress. The study aims to identify the different roles of GB in regulating the diverse defense mechanisms of maize against drought and flooding. Methods Hybrids of Yindieyu 9 and Heyu 397 grown in pots in a ventilated greenhouse were subjected to flooding (2–3 cm standing layer) and drought (40–45% field capacity) at the three-leaf stage for 8 d. The effects of different concentrations of foliar GB (0, 0.5, 1.0, 5.0, 10.0 mM) on the physiochemical attributes and growth of maize were tested. Results Both varieties were verified to have greater drought tolerance to combat oxidative stress associated with higher antioxidant activities, and proline content than flooding. While flooding decreased superoxide dismutase, peroxidase activities, and proline content, those all declined with stress duration, leading to a larger reactive oxygen species than drought. Heyu 397 was verified to be more sensitive to drought and flooding than Yindieyu 9. It was peroxidase under drought and ascorbate peroxidase under flooding that played crucial roles in tolerating water stress. Foliar GB further enhanced antioxidant ability which contributed the most effect to peroxidase to eliminate more hydrogen peroxide than superoxide anion under water stress, promoting growth especially for leaf. Furthermore, exogenous GB made a greater increment on Heyu 397 than Yindieyu 9 as well as flooding than drought. Conclusion Overall, a GB concentration of 5.0 mM with a non-toxic effect on well-watered maize was determined to be optimal for the effective mitigation of water stress damage to the physiochemical characteristics and growth of maize.