Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
University of Chinese Academy of Sciences, Beijing, China.
BMC Plant Biol. 2023 Sep 14;23(1):425. doi: 10.1186/s12870-023-04433-2.
As the male and female gametophytes of flowering plants, pollen and ovules largely determine the upper and lower boundaries of plant reproductive success. It is commonly predicted that pollen and ovule number per flower should increase, and pollen-ovule ratio (P/O) per flower should decrease with increasing elevation in response to a more stochastic pollination environment. Here, we aimed to determine the response of pollen number, ovule number, and P/O to other floral traits and elevation gradients for 84 insect-pollinated herbaceous flowering plant species in five sub-alpine and alpine communities (2709 to 3896 m a.s.l.) on Yulong Snow Mountain, southwestern China.
Six floral traits, including P/O, floral display area, flower number, tube depth, flower shape, and pollen presentation, were highly correlated with pollen and ovule number per flower. With increasing elevation, pollen number and P/O per flower increased marginally and significantly, respectively; ovule number per individual, flower number per individual, stigma stamen separation, and inflorescence height decreased significantly. However, ovule number per flower and other floral traits (i.e., floral display area, tube depth, stigma height, stamen height, and pollen and P/O per individual) did not change with elevation. We detected significant phylogenetic signals for pollen number, ovule number, and P/O, suggesting that these traits may be highly conserved and with limited response to changing environmental conditions.
Results revealed patterns of plant reproductive character evolution along elevation gradients and the potential factors governing their spatial variation in high-elevation environments. Plant species at high elevations are more likely adapted to cross-pollination, indicated by increased P/O per flower at high elevations on Yulong Mountain. Combined effects of phylogenetic history and plant-pollinator interactions should determine plant trait evolution.
作为开花植物的雄性和雌性配子体，花粉和胚珠在很大程度上决定了植物生殖成功的上限和下限。通常预测，随着更随机的传粉环境，每朵花的花粉和胚珠数量应该增加，而每朵花的花粉-胚珠比（P/O）应该减少。在这里，我们旨在确定 84 种虫媒草本开花植物物种的花粉数量、胚珠数量和 P/O 对其他花部特征和海拔梯度的响应，这些物种分布在中国西南部玉龙雪山的五个亚高山和高山群落（2709 至 3896 米海拔）。
六个花部特征，包括 P/O、花展示面积、花数、管深、花型和花粉呈现，与每朵花的花粉和胚珠数量高度相关。随着海拔的升高，每朵花的花粉数量和 P/O 分别略有显著增加；个体胚珠数量、个体花数、柱头雄蕊分离和花序高度显著下降。然而，每朵花的胚珠数量和其他花部特征（即花展示面积、管深、柱头高度、雄蕊高度以及个体花粉和 P/O）没有随海拔变化。我们检测到花粉数量、胚珠数量和 P/O 的显著系统发育信号，表明这些特征可能高度保守，对环境条件变化的响应有限。
结果揭示了植物生殖特征沿海拔梯度的进化模式以及控制其在高海拔环境中空间变化的潜在因素。高海拔地区的植物物种更有可能适应异花传粉，这表现在玉龙山上高海拔地区每朵花的 P/O 增加。系统发育历史和植物-传粉者相互作用的综合效应应决定植物特征的进化。
