Thirsty, soaked, and thriving: Maize morpho-physiological and biochemical responses to sequential drought, waterlogging, and re-drying

Abstract

Maize (Zea mays), a pivotal cereal crop, frequently encounters sequential abiotic stresses—drought, waterlogging, and re-drought—that impose multifaceted and interlinked constraints on its growth and productivity. This study elucidates the specific impacts of these sequential stress events on maize morphology, physiology, and biochemistry, offering critical insights into the crop's adaptive capacities and limitations. Drought stress elicited severe morphological alterations, including pronounced leaf curling, significant reductions in leaf area, and inhibited shoot elongation, collectively undermining photosynthetic efficiency. Root systems exhibited marked shallowness and sparsity, substantially restricting water and nutrient uptake. Photosynthetic pigment degradation, particularly of chlorophyll and carotenoids, was acute, accompanied by diminished CO₂ assimilation and elevated leaf temperatures, which likely exacerbated oxidative stress through reactive oxygen species (ROS) overproduction. Waterlogging stress following drought, although alleviating some drought-induced damage, introduced oxygen deprivation in the rhizosphere, leading to disrupted root respiration, necrosis, and impaired nutrient acquisition. Adaptive responses, such as partial recovery of photosynthetic pigments, improved water balance, and reduced oxidative stress; however, metabolic recovery remained incomplete, with stunted growth and persistent root biomass loss. Re-drought stress followed by pre-drought and waterlogging imposed the most catastrophic effects, characterized by pervasive leaf necrosis, pronounced shoot and root stunting, and a systemic collapse in biomass accumulation. The re-drought phase was marked by escalated ROS levels, membrane destabilization, and the overwhelming failure of antioxidative defenses, culminating in metabolic dysfunction and structural disintegration. These findings underscore the urgent necessity for targeted breeding strategies to optimize root system architecture, fortify antioxidative defense mechanisms, and enhance osmoprotectant synthesis. Integrative multi-omics approaches and comparative studies across diverse maize genotypes are imperative to unravel the genetic and molecular underpinnings of stress resilience.