Potassium application promote cotton acclimation to soil waterlogging stress by regulating endogenous protective enzymes activities and hormones contents

To investigate the effect of potassium application on cotton damage mitigation after waterlogging stress, experiments were conducted under two potassium application levels (0 and 150 kg K2O hm-2) with three types of soil waterlogging treatments (0d, 3d and 6d) during cotton flowering stage. The results showed that: (a) under simple soil waterlogging stress, the increments of endogenous hormones contents of IAA, GA3 and ZR in cotton leaves were decreased as days of soil waterlogging. On the contrary, the soluble protein, MDA and ABA contents were significantly increased, while ZR/ABA, IAA/ABA and GA3/ABA were decreased. CAT and POD enzyme activities were increased although SOD activity decreased with the duration of soil waterlogging. (b) Potassium application combined with soil waterlogging significantly affected the antioxidant enzymes activity and endogenous hormones balance compared with soil waterlogging alone, leading to a significant increase in soluble protein and a pronounced decrease in H2O2 content, O2- generation rate, and MDA content, a significant increase in IAA, GA3 and ZR contents while a decrease in ABA content. Besides, it also kept higher SOD, CAT activities and slowly increased POD activity. (c) There was an obvious compensatory effect in cotton after 3d soil waterlogging under potassium application, which promoted rapidly recovery of physiological enzymes activities and ABA content. However, 6d soil waterlogging required a longer time for recovery. These findings were expected to provide a scientific and theoretical basis for reducing flood damage and improving cotton yield.