Climate Extremes and Crop Productivity: Integrating Physiological Mechanisms and Adaptive Traits for Resilience and Yield Stability

Climate extremes such as heatwaves, prolonged droughts, soil salinization, and flooding are increasingly threatening global food security by destabilizing crop yields. These stressors disrupt essential physiological processes including photosynthesis, water relations, nutrient uptake, and reproductive development. Plants, however, have evolved a range of adaptive physiological pathways that confer resilience under such conditions. Heat stress triggers thermotolerance mechanisms through heat shock proteins, membrane stabilization, and antioxidant defenses. Drought resilience is mediated by stomatal regulation, osmotic adjustment, root plasticity, and abscisic acid (ABA) signaling. Under salinity, plants maintain ion homeostasis, sequester toxic ions, and accumulate compatible solutes, while flooding tolerance involves hypoxia sensing, aerenchyma formation, ethylene signaling, and metabolic reprogramming. Importantly, many of these responses converge through shared signaling pathways involving reactive oxygen species (ROS), calcium ions, and hormonal crosstalk, resulting in cross-tolerance against multiple stresses. Physiological traits such as stay-green phenotype, water use efficiency (WUE) and radiation use efficiency (RUE), reproductive resilience, and recovery capacity are increasingly recognized as critical determinants of yield stability under climate extremes. Advances in high-throughput phenotyping, omics technologies, and gene editing provide unprecedented opportunities to integrate these traits into breeding programs. This review highlights the physiological basis of crop resilience to climate extremes, discusses strategies for trait deployment in crop improvement, and identifies future directions for linking physiology to climate-smart agriculture. By emphasizing resilience and yield stability, the paper underscores the need to reorient breeding and management strategies toward crops capable of sustaining productivity in an era of climatic uncertainty.