Effects of Ethylene on Cotton Adaption to Waterlogging Stress and the Underlying Mechanism

[Objective] Waterlogging adversely affects cotton growth and development, and continuous waterlogging may further result in considerable yield loss or crop failure. Enhancing the ability of cotton to adapt to waterlogging stress to preserve yield and quality is therefore critical. Ethylene is an important signal molecule, which plays a vital role in the process of plant stress resistance. However, the mechanism of ethylene in mitigating cotton waterlogging damage is still unclear. [Method] In this study, we setup an experiment with a cotton (Gossypium hirsutum L.) variety K638 in an electric rain shelter at the experimental station of the Shandong Cotton Research Center at Linqing, Shandong. We treated the cotton plants by waterlogging for 10 d during the flowering stage and used a non-waterlogged treatment as the control. During the waterlogging stress treatment, cotton plants were treated with an ethylene signal transduction inhibitor (1-MCP) or ethylene synthesis precursor (ACC) to detect the effects of ethylene content on cotton waterlogging injury and its physiological mechanism. [Result] The results revealed that a foliar spray of 1-MCP significantly inhibited ethylene synthesis in the stressed cotton plants, the content of ethylene and malondialdehyde (MDA) decreased by 5.3% and 39.2%, and the activities of alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC), and lactate dehydrogenase (LDH) decreased by 37.8%, 20.5%, and 8.2%, respectively. The photosynthetic rate, dry weight of the whole plant, and seed cotton yield increased by 13.5%, 3.3%, and 4.6%, respectively. The effect of ACC on the plants was the opposite because spraying ACC promoted ethylene accumulation in the waterlogged cotton. The ethylene and MDA content increased by 8.0% and 19.5%, respectively. The activities of ADH, PDC, and LDH increased by 17.5%, 11.2%, and 8.0%, respectively, while the photosynthetic rate, dry weight of the whole plant, and seed cotton yield decreased by 6.0%, 7.7%, and 8.0%, respectively. [Conclusion] In summary, reducing ethylene content in waterlogged cotton plants can significantly alleviate hypoxia damage caused by waterlogging stress and subsequently promote cotton growth and development by restoring physiological metabolism.