Effects of drought-flood abrupt alternation on the characteristics of leaf senescence and grain yield of maize

Drought and waterlogging have been two of the most important abiotic stresses on plant growth and development. Furthermore, plants can suffer from the dual stresses of drought and waterlogging in some cases, including drought-flood abrupt alternation (DFAA) stress. The occurrence of DFAA is ever increasing in the middle and lower reaches of the Yangtze River, China, in recent years, due mainly to the global climate. There is a severe threat to the sustainable crop production. However, it remains unknown about the DFAA impact on the leaf senescence and grain yield of maize, together with the underlying mechanisms. The purpose of this study was to investigate the effects of different water stress treatments at the jointing stage on the net photosynthetic rate (P_n), leaf SPAD values, activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), soluble protein and malondialdehyde (MDA) contents at the key growth stages, ear number per plant, kernels number per ear, and one-thousand weight of maize. Taking the spring maize "Yidan 629" as the research object, a leaching-pond experiment was carried out in Jingzhou City, Hubei Province, China in 2021. The treatments included the moderate drought (with 55%-60% field capacity as irrigation low limit for 18 d, D), waterlogging for 6 d (W), moderate drought immediately followed by waterlogging for 3 d (D-LW), moderate drought immediately followed by waterlogging for 6 d (D-MW), moderate drought immediately followed by waterlogging for 9 d (D-HW) at the jointing stage, and well-water during the whole grown season (CK) of maize. Leaf senescence traits were characterized to determine the grain yield and its components at the bell, tasselling and filling stages. The results showed that there were comparable SPAD values, SOD, CAT, and POD activities, soluble protein content, P_n at the tasselling and filling stages, and ear number per plant, kernels number per ear, and one-thousand weight in the D-LW treatment, compared with the CK. Thus, a relatively high grain yield was obtained in the D-LW treatment. This indicated that the moderate drought immediately followed by waterlogging for 3 d at the jointing stage reduced the leaf senescence, thus stabilizing the grain yield of maize. Compared with the CK, the treatments D, W, D-MW, and D-HW significantly reduced P_n, SPAD values, activities of SOD, CAT, and POD, and soluble protein content, whereas, there was a significant increase in the MDA content of maize leaves at the bell, tasselling, and filling stages, resulting in the low ear number per plant, kernels number per ear, and one-thousand weight, and correspondingly smaller grain yield of maize. Consequently, the treatments D, W, D-MW, and D-HW significantly reduced the grain yield of maize by 13.3%-72.7%. Overall, the adverse effects of water stress treatments on the leaf senescence and grain yield were ranked in the descending order of D-HW, D-MW, W, D, D-LW treatment. Therefore, the moderate drought immediately followed by waterlogging for 3 d at the jointing stage shared the compensatory on the SPAD value, antioxidant enzyme activities, soluble protein content and P_n of maize leaves, leading to a relatively high grain yield of maize. The finding can also provide a theoretical reference to cope with the drought-flood abrupt alternation disaster, and then manage the irrigation and drainage for maize.