Impression of contemporary heat stress complexities in agricultural crops: a review

Recent global climate patterns have resulted in a higher occurrence of exceptionally high temperatures presenting substantial complications for agricultural productivity worldwide. Prolonged exposure to elevated temperatures, or heat stress, can cause irreversible damage to plant health. The intricate processes of plant growth and development, which rely on numerous temperature-sensitive biochemical reactions, are profoundly affected by the intensity and duration of heat events as well as the specific plant species involved (e.g., wheat). Therefore, a comprehensive understanding is essential to develop effective management strategies to mitigate heat stress and protect crop yield and quality. Heat stress occurring during critical growth stages can drastically reduce the productivity of staple food crops, threatening global food security. It can decrease agricultural output by up to 12% by impairing key physiological processes such as photosynthesis, reproduction and seed germination (decrease up to 25%). This review investigates how heat stress disrupts enzyme activities including rubisco, nitrate reductase, proteases, catalase, starch synthase and ATP synthase, leading to impairments in photosynthesis, carbohydrate metabolism, protein synthesis, anti-oxidative defense and regulation of phytohormones. These disruptions negatively affect plant growth and yield. By examining the roles of protective mechanisms, such as, heat shock proteins, enzymatic and non-enzymatic antioxidants (ascorbic acid, carotenoids, flavonoids, α-tocopherol, catalase, glutathione reductase, superoxide dismutase, and peroxidases), osmoprotectants (proline, glycine betaine, trehalose), phytohormones (abscisic acid, cytokinins and salicylic acid) and morphological adaptations, the review underscores the complexity and the interdependence of various defense systems in crop improvement strategies, focusing on the identification of key metabolic markers, stress-resilient traits and molecular targets for genetic enhancement.