Impact of high day and night temperatures on major food crops: A comprehensive review

Abstract

Understanding plant responses to both day and night heat is essential for developing climate smart agriculture systems to sustain global food production. High daytime (> 35 °C) and nighttime (> 25 °C) temperatures are increasingly threatening global food production. Major crops such as rice, wheat, maize, soybean and barley are especially vulnerable during flowering and grain filling. However, the distinct and combined effects of day versus night heat on crop performance remain underexplored in a comparative manner. This review synthesises findings from recent physiological, biochemical and molecular studies on heat stress responses in staple food crops. It compares the impacts of high day temperature and high night temperature on photosynthesis, respiration, reproductive development, oxidative stress, antioxidant defenses, grain yield and quality. Data from field experiments, controlled environment studies and meta-analyses are integrated. Daytime heat impairs photosynthesis and carbon assimilation, while nighttime heat increases respiration rates, depletes carbohydrate reserves and disrupts nutrient partitioning. Both conditions reduce pollen viability and spikelet fertility, causing yield losses of 5–40 % depending on the crop and growth stage. Heat stress triggers reactive oxygen species accumulation, leading to cellular damage and membrane lipid peroxidation. Antioxidant systems (superoxide dismutase, catalase, ascorbate peroxidase) provide only partial protection under prolonged heat. Crop-specific vulnerabilities include grain chalkiness in rice, reduced kernel weight in maize and impaired nodulation in legumes. Breeding tools such as clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein 9 (CRISPR/Cas9) and agronomic practices like adjusted sowing dates and optimised irrigation help mitigate these effects. This review uniquely compares daytime and nighttime heat effects across multiple staple crops, integrating physiological, molecular and agronomic perspectives with quantitative yield data.