Integrative plant responses to combined drought and heat stress: Implications for climate-resilient crop development

Global climate change has intensified the frequency and severity of droughts and heat waves, posing a critical threat to agricultural productivity and global food security. Although extensive research has examined plant responses to individual stresses such as drought or heat, the simultaneous or concurrent effect of these stresses in field conditions is inevitable. Despite this reality, integrated understanding of plant responses to combined stress remains limited and fragmented. This review addresses this gap by systematically synthesizing current knowledge on the individual and interactive effects of these stresses on crop plants. The review focusses on how combined drought and heat stress influences morpho-physiological, biochemical, molecular, and metabolic processes, emphasizing that their synergistic effects are often more severe than either stress alone, leading to substantial reductions in crop yield and nutritional quality. Particular attention is given to the central role of reactive oxygen species (ROS) and phytohormone-mediated signaling pathways in facilitating adaptive responses under combined stress conditions. In addition, recent advances in in multi-omics approaches including genomics, transcriptomics, proteomics, and metabolomics are integrated with emerging strategies such as transgenic and microRNA- based technologies, aimed at enhancing crop resilience. This review provides a comprehensive framework for understanding plant responses to combined abiotic stresses, highlighting stress interactions and translating mechanistic insights into strategies for developing stress-resilient crops.