Donam Tushabe

Climate change‐induced heat waves often reduce seed yields and quality via high‐temperature effects in the gametophytic phase. Yet, in contrast to model and crop species, the ability of pollen and ovules to adapt or acclimate to heat stress in wild plants remains poorly understood. To address this gap, we examined the adaptation and acclimation potential of six gametophytic traits in 11 wild Silene vulgaris populations across a temperature gradient in Europe. First, we cultivated plants in a common garden to reveal differences in gametophytic traits indicative of adaptation. Next, we assessed their acclimation potential by subjecting flowering plants to two chronic heat stress (CHS) treatments: moderate (35°C/30°C) and severe (40°C/35°C) for 18 days. Also, we estimated the CHS effects on seed quantity and quality. The common garden experiment showed no intraspecific variation in gametophytic traits across the temperature gradient, suggesting these traits may not influence reproductive adaptation to local habitats. During CHS, the female gametophyte was less temperature‐sensitive than the male. Moderate CHS led to larger ovaries with more large‐sized ovules, while severe CHS reduced ovule numbers but increased their size. Both CHS treatments decreased pollen grain numbers, size, and anther length, with severe CHS causing greater reductions. These reductions in gametophytic traits led to lower seed yield and quality. Under both CHS treatments, acclimation potential did not vary along the temperature gradient, except for pollen size under severe CHS, which was larger in warmer climates. Our findings revealed the lack of adaptation and acclimation mechanisms in the gametophytic traits (except for pollen size) of wild Silene vulgaris populations along the temperature gradient. These findings suggest that Silene plants may rely on alternative strategies, such as shifts in gametophyte physiology and biochemistry or flowering phenology, to respond to thermal stress associated with heat waves.

Climate change-induced heat waves often result in reduced seed yields and quality via high-temperature effects in the gametophytic phase. Surprisingly, the ability of pollen and ovules, particularly among wild plant populations, to adapt or acclimate to heat stress remains poorly understood. To address this gap, we examined the adaptive and acclimation potential of six gametophytic traits in eleven distinct populations of wild Silene vulgaris across a temperature gradient in Europe. First, we cultivated plants in a common garden to reveal differences in gametophytic traits indicative of adaptation. Next, we assessed the acclimation potential of these traits to heat stress by subjecting flowering plants to two chronic heat stress (CHS) treatments: moderate (35/30 °C) and severe (40/35 °C), for 18 days. Findings from the common garden experiment indicated no intraspecific variation in gametophytic traits across the temperature gradient, suggesting that these traits may not influence the plant’s sexual adaptation to its local habitat. Plants originating from colder climates produced more and larger seeds than those from warmer climates. During CHS treatments, the female gametophyte was less temperature sensitive compared to the male gametophyte. Moderate CHS led to larger ovaries with more, large-sized ovules, while severe CHS reduced ovule numbers but increased their size. In contrast, both CHS treatments decreased pollen grain numbers, size, and anther length, with severe CHS causing more significant reductions. These reductions in gametophytic traits ultimately translated to lower seed yield and quality, which may threaten the sustained existence of natural plant populations over time. Under both CHS treatments, the acclimation potential did not vary among plant populations along the temperature gradient, except for pollen size under severe CHS, with larger pollen size in warmer climates than in colder regions. Our findings suggest that the lack of adaptation and acclimation mechanisms in the gametophytic traits (except for pollen size) of wild Silene vulgaris populations along the temperature gradient indicates that these plants may rely on alternative strategies, such as shifts in flowering time, to respond to thermal stress.

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 limits (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 191 species with contrasting phylogeny, cultivation history, growth form and ecology. At the species level, the PTLs range from 9.0 to 42.4°C, with considerable differences among individual species. Vegetative tissue showed greater tolerance to both low and high temperatures than pollen. A significant, though weak, correlation was observed between PTLs and leaf temperature tolerance. Pollen heat tolerance was independent of that in leaves and stems. The greatest intraspecific variability was observed in pollen cold tolerance (Tmin), followed by Topt and Tmax. Phylogenetic analysis revealed family‐level conservation in all three pollen temperature tolerance measures. Climate emerged as a significant PTL driver of pollen cold tolerance, with species from colder and stable climates exhibiting enhanced cold tolerance. Cultivated and wild species did not differ in their pollen temperature tolerances. Herbaceous plants showed higher tolerance to high temperatures compared to shrubs and trees, potentially reflecting divergent thermal conditions during anthesis. This study provides the first formal analysis of complex relationships between pollen temperature limits, plant characteristics and environmental factors, providing crucial insights into climate change impacts on plant reproduction.

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.