Maize Genomics and Genetics 2025, Vol.16, No.3, 129-138 http://cropscipublisher.com/index.php/mgg 131 grains are more sensitive in the early stages of development than in the later stages. Although the heat shock response of mature pollen is relatively limited, heat shock proteins (HSPs) induced by heat stress still play a role in physiological responses (Dupuis and Dumas, 1990). Figure 1 Effect of heat stress on pollen viability of maize at different periods (Adopted from Lv et al., 2024) Image caption: (A) The blue circles indicate the period of heat stress application in maize from different trials; the yellow bars represent the period for which heat stress lasted; the dotted line is positioned at the midpoint of the heat stress period in each trial, and the numbers in the blue circles are the data number of each trial; the orange line is obtained by fitting all data points. (B) Picture of pollen viability by 2,3,5-triphenyltetrazolium chloride (TTC) staining (darker colors show increased viability) (a) SEM images of pollen grains under control temperature (CT; 32/22 ℃), (b) high temperature (HT; 36/26 ℃), (c) extremely high temperature (EHT; 40/30 ℃; d) treatments. White arrows indicate the aperture of pollen. (C) Schematic overview of cytological alterations imposed by heat stress during male gametophyte development tracked by the leaf collar method of maize. PMC, pollen mother cell (Adopted from Lv et al., 2024) 3 Effects of High Temperature on Female Reproductive Development 3.1 Inhibition of ovule and silk development High temperature stress has a significant impact on the development of maize female reproductive structures, especially the development of ovules and filaments. The rate of filaments spitting out bracts is significantly reduced, the number of hairs on filaments is reduced, and the vitality of filaments is reduced. High temperature stress can delay the development of stigma, make it difficult for female ears to spin silk, prolong the interval between tasseling and silking, shorten the pollination time, and thus prolong the anthesis-silking interval (ASI), which is the critical window period for successful fertilization (Alam et al., 2017). Delayed filament development
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