Molecular Plant Breeding 2025, Vol.16, No.4, 211-220 http://genbreedpublisher.com/index.php/mpb 213 synchronized pollination can be achieved, the impact caused by delayed filaments can be partially compensated for. Furthermore, asynchronous pollination can also cause the kernels on the same panicle to compete for nutrients, and some kernels may fail due to insufficient nutrient supply. Figure 1 Multiple processes related to kernel set are affected by drought stress throughout the flowering stage (Adopted from Shen et al., 2019) Image caption: At the tasseling stage, drought causes pollen abortion, limits ear differentiation, and extends the anthesis-silking interval (ASI), all of which are associated with kernel abortion. At the silking stage, drought can severely suppress silk elongation, widen the time intervals of early- and later-emerged silks, and extend the pollination time gaps (PTG) for ovaries within ear. Increased PTG is a factor known to induce kernel abortion. During the stage between pollination and fertilization, drought decreases silk receptivity and limits pollen germination and pollen tube elongation, leading to pollination failure or kernel abortion. After fertilization, kernel abortion may be induced by drought (Adopted from Shen et al., 2019) 3.3 Synchronization metrics and evaluation techniques Pollination synchrony can be measured by several indicators, such as the distribution of filament exposure time, the length of pollination intervals, and the seed setting rate (for example, the number of kernels produced divided by the number of filaments involved in pollination). In the field, the effects of natural pollination and artificial synchronous pollination can be compared, and the impact of synchronous pollination can be evaluated by combining the changes in the number of kernels in the main and secondary panicles (Westgate et al., 2022). In addition, computational models can be used to simulate the process of pollen diffusion and pollen reception by filaments. Combined with the data measured in the field, pollination synchrony and its contribution to the final yield can be quantified more accurately (Kuo et al., 2021). 4 Effects of Sowing Date on Reproductive Timing and Fertility 4.1 Early vs. late sowing: thermal accumulation and developmental shifts Early-sown maize usually grows better because it can utilize the temperature earlier and has a longer growth period. Thus, the plants grow vigorously, the kernel development time is sufficient, and the yield will naturally be higher (Tsafack et al., 2024). If sowing is too late, the vegetative growth period of the plants will be shortened. Although the reproductive period may be prolonged, the overall growth period is still shortened, the accumulated heat is reduced, and the kernel development will be affected (Cao et al., 2024). In the northern and northeastern regions of our country, early sowing can make full use of sunlight and temperature, which is conducive to increasing theoretical yields. If sown late, there will be less light and heat, and the yield is also prone to decline (Zhu et al., 2022; Wu et al., 2023). In tropical and subtropical regions, late sowing often causes maize to enter the
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