Maize physiology under waterlogging: shoot and root adaptive responses to mitigate low oxygen stress

Waterlogging is a major constraint to maize (Zea mays L.) productivity, particularly in regions increasingly affected by extreme precipitation. This review synthesizes current knowledge on the physiological and molecular responses of maize to low-oxygen stress, focusing on adaptive mechanisms in both root and shoot tissues. In roots, lysigenous aerenchyma formation is triggered by hypoxia, ethylene, and reactive oxygen species signaling, facilitating internal oxygen diffusion. Flood-induced adventitious roots-regulated by ethylene-auxin interactions and raffinose metabolism-promote fine lateral root development, enhancing nutrient uptake. Since maize lacks a tight barrier to radial oxygen loss, introgression of the quantitative trait locus that promotes its formation from Zea nicaraguensis, represents promising breeding targets. Shoot-level physiological changes-including reduced stomatal conductance, impaired photosynthesis, and premature senescence-may result from oxidative stress signaling. Leaf damage persists long after soil saturation ends, indicating limited recovery capacity. Cytokinins can mitigate oxidative damage and delay senescence, offering the potential for enhancing shoot resilience. Further research is needed to determine if shoot aerenchyma occurs in maize and how it is regulated. Integrating transcriptomics, phenomics, and field-based evaluations will be crucial to understand both root and shoot responses and will accelerate the breeding of climate-resilient maize for flood-prone agroecosystems.