Physiological impact of heat stress and their alleviation measures in agriculture: A review

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Abiotic stresses are becoming more prevalent in modern agriculture as a result of shifting climate scenarios. Elevated temperature stress is one of the most important abiotic stresses to address since it has detrimental consequences for plant physiology, molecular structure, and phenology. The morphological impact occurs in the form of reduced germination, poor emergence, poor seedling vigor, abnormal seedling. Heat stress also results in the closure of stomata, reduced leaf size and consequent increase in stomatal density. One of the major physiological impacts of heat stress is on the fluidity of the membrane structure of the plant cell. Heat stress leads to increased fluidity of the thylakoid membrane and disruption of metabolic functions, which either deliver or accept electrons from PSII and, thus, cause dislodging of PSII from thylakoid membrane. The respiration generally increases in the temperature range of 0-35/ 40⁰C, reaches plateau at 40-50⁰C and decreases beyond 50⁰C due to damage to the respiratory mechanism. Elevated temperature directly impacts the cellular water content and indirectly through the increased water depletion rate from the soil. In order to design the appropriate corrective actions, it is crucial to research all the factors leading to heat stress thoroughly. The traditional agronomic and breeding interventions are crucial, but the rising food demand and the intensifying heat stress call for some cutting-edge biotechnological interventions, such as transgenics, genome editing, and CRISPR/cas9, to induce genome-level heat tolerance. The present review deals in detail with each of the previously listed aspects.