Table 1.

Effects of high temperature stress in different crop species.

Crops	Heat treatment	Growth stage	Major effects	References
Chili pepper (Capsicum annuum)	38/30 °C (day/night)	Reproductive, maturity and harvesting stage	Reduced fruit width and fruit weight, increased the proportion of abnormal seeds per fruit.	[36]
Rice (Oryza sativa)	Above 33 °C, 10 days	Heading stage	Reduced the rates of pollen and spikelet fertility.	[37]
Wheat (Triticum aestivum)	37/28 °C (day/night), 20 days	Grain filling and maturity stage	Shortened duration of grain filling and maturity, decreases in kernel weight and yield.	[38]
Wheat (Triticum aestivum)	30/25 °C day/night	From 60 DAS to maturity stage	Reduced leaf size, shortened period for days to booting, heading, anthesis, and maturity, drastic reduction of number of grains/spike and smaller grain size and reduced yield.	[39]
Sorghum (Hordeum vulgare)	40/30 °C (day/night)	65 DAS to maturity stage	Decreased chlorophyll (chl) content, chl a fluorescence, decreased photosystem II (PSII) photochemistry, Pn and antioxidant enzyme activity and increased ROS content, and thylakoid membrane damage, reduced yield.	[40]
Rice (Oryza sativa)	32 °C (night temperature)	Reproductive stage	Decreased yield, increased spikelet sterility, decreased grain length, width and weight.	[41]
Maize (Zea mays)	35/27 °C (day/night), 14 days	Reproductive stage	Reduced ear expansion, particularly suppression of cob extensibility by impairing hemicellulose and cellulose synthesis through reduction of photosynthate supply.	[42]
Rice (Oryza sativa)	25–42.5 °C	Vegetative growth stage	Decrease in the CO2 assimilation rate.	[43]
Soybean (Glycine max)	38/28 °C (day/night), 14 days	Flowering stage	Decreased the leaf Pn and stomatal conductance (gs), increased thicknesses of the palisade and spongy layers, damaged plasma membrane, chloroplast membrane, and thylakoid membranes, distorted mitochondrial membranes, cristae and matrix.	[44]
Tobacco (Nicotiana tabacum)	43 °C, 2 h	Early growth stage	Decrease in net photosynthetic rate (Pn), stomatal conductance as well as the apparent quantum yield (AQY) and carboxylation efficiency (CE) of photosynthesis. Reduced the activities of antioxidant enzymes.	[45]
Okra (Abelmoschus esculentus)	32 and 34 °C	Throughout the growing period	Reduced yield, damages in pod quality parameters such as fibre content and break down of the Ca-pectate.	[46]
Maize (Zea mays)	33–40 °C, 15 days	During Pre-anthesis and silking onwards	Severe effect on plant and ear growth rates.	[47]
Wheat (Triticum aestivum)	38 °C, 24 and 48 h	Seedling stage	Decreased chl and relative water content (RWC); diminished antioxidative capacity.	[18]
Wheat (Triticum aestivum)	32/24 °C (day/night), 24 h	At the end of spikelet initiation stage	Spikelet sterility, reduced grain yield.	[48]

DAS—Days after sowing.