Effects of Waterlogging at Different Developmental Stages on Growth, Yield and Physiological Responses of Forage Maize

Waterlogging (WL) is an abiotic stress that severely limits crop yield. However, limited research has addressed the effects of long-term WL stress at different developmental stages on the yield and physiological responses of forage maize. In this study, forage maize plants were subjected to 14-day WL stress at the emergence (E), four-leaf (V4), eleven-leaf (V11), and tasseling (VT) stages. Plant height significantly decreased by 60% at the E stage and 48% at the V4 stage when exposed to 14-day WL. Leaf area decreased by 79% at the E stage, and the number of green leaves decreased most significantly at the VT stage. Chlorophyll fluorescence (Fv/Fm) and the relative chlorophyll content index (RCI) decreased most significantly at the V4 stage. The lysigenous aerenchyma formation rate of the roots increased significantly after 14-day WL at the V4 stage, whereas the number of adventitious roots increased most significantly at the V11 stage. The hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, which are indicative of the root oxidation state, exhibited the highest increase at the E stage. In addition, at the E and V4 stages, the expression of genes related to energy metabolism and lysigenous aerenchyma formation in the roots was upregulated after 14-day WL. The total dry matter (DM) of maize after harvest decreased most significantly when exposed to 14-day WL at the V4 stage, while acid detergent fiber (ADF) and neutral detergent fiber (NDF) increased with the developmental stages. Consequently, total digestible nutrients (TDNs) and the relative feed value (RFV) decreased with advancing developmental stages, with the highest decrease at the VT stage. These results demonstrate that effective drainage management during the early developmental stage (V4) is more important to prevent forage maize yield loss due to prolonged WL stress, which is expected to increase in frequency due to climate change, and management during the later developmental stage (VT) is critical to prevent decreases in feed values. These findings provide valuable insights into the physiological responses of forage maize to WL stress.