Patterns and drivers of pollen temperature tolerance

Pollen, a pivotal stage in the plant reproductive cycle, is highly sensitive to temperature fluctuations, impacting seed quality and quantity. While the importance of understanding pollen temperature limtits (Tmin, Topt, Tmax – collectively PTLs) is recognized, a comprehensive synthesis of underlying drivers is lacking. Here, we examined PTLs, correlating them with vegetative tissue thermotolerance and assessing variability at the intra- and interspecific levels across 198 species with contrasting phylogeny, cultivation history, biology and ecology. At the species level, the PTLs range from 6.1 to 39.5 0 C, with considerable differences among growth forms and cultivation histories. Positive correlations were found between PTLs and leaf/stem temperature tolerances. Notably, pollen cold tolerances varied significantly across species populations, while Topt and Tmax values remained stable. Phylogenetic analysis revealed family-level conservation in pollen cold tolerance, contrasting with heat tolerance’s independence from evolutionary history. Climate emerged as a significant PTL driver, with species at higher elevations and latitudes exhibiting enhanced cold and heat tolerance. Cultivated species displayed narrower temperature tolerances (10.3-39.9 °C) than their wild counterparts (5.2-42.3 °C), highlighting potential crop vulnerabilities to global warming. Herbaceous plants exhibited superior tolerance to both low and high temperatures compared to shrubs and trees, reflecting divergent thermal conditions during anthesis. This study illuminates complex relationships between pollen temperature limits, plant characteristics, and environmental factors, providing crucial insights into climate change impacts on plant reproduction.