Temporal dynamics of floral characteristics and reproduction output of Impatiens oxyanthera under warming

Climate warming threatens plant sexual reproduction, and plants with extended flowering can experience distinct biotic and abiotic environments across the season. Therefore, responses and adaptations of plant reproduction to warming may vary across the season. Our aim was to examine how climate warming affects plant floral traits and reproductive success across different phenological stages within a single flowering season. In this study, infrared heaters were used to simulate warming (+1.5°C) during the growing season of Impatiens oxyanthera. Flowering was divided into early, middle, and late time-periods based on the flowering onset and end dates of the experimental population. The changes in floral and reproductive characteristics, as well as their relationships across these three time periods, were investigated under warming conditions. Our study on I. oxyanthera demonstrates that warming significantly delayed flowering onset, reduced the number of flowers per plant, and decreased both the length and curvature of nectar spurs. Warming also disrupted correlations between floral traits to some extent compared with the control. Flowers that opened during the late period were smaller, had fewer ovules but more nectar, and produced fewer filled seeds. Warming exerted period-specific impacts on nectar spur length, reducing it during the late flowering period compared with the control treatment but not during the early or middle periods. However, the changes in floral traits caused by the interaction of warming and flowering period did not significantly affect reproductive success at the single-fruit level. These findings highlight the temporal heterogeneity of plant responses to climate warming and suggest that potential buffering mechanisms might contribute to maintaining reproductive outcomes under moderate warming conditions.