Abstract
High-temperature stress is a major abiotic constraint limiting plant growth and agricultural productivity. While its adverse effects are well documented, most studies have examined individual species or isolated physiological mechanisms. This review provides a comprehensive comparative analysis of heat stress responses across four major crops - barley ( Hordeum vulgare ), rice ( Oryza sativa ), maize ( Zea mays ), and tomato ( Solanum lycopersicum ), alongside the model plant Arabidopsis thaliana , focusing on their morphological, physiological, and biochemical adaptations as well as current mitigation strategies. Morphological assessments reveal that root traits are more heat-sensitive than shoot length, biomass, or germination rate. Physiologically, all species exhibit reduced photosynthetic rate and PSII efficiency (Fv/Fm), though stomatal conductance and transpiration responses vary. Biochemically, the accumulation of reactive oxygen species (ROS) and antioxidant activity exhibit species- and stress-dependent regulation, with both upregulation and downregulation observed. Among mitigation approaches, seed priming emerges as a cost-effective strategy, while miRNA-mediated regulation shows strong potential for developing heat-tolerant cultivars. This synthesis highlights critical knowledge gaps and outlines future directions for enhancing crop resilience in the face of rising temperatures.