以两种玉凤花属植物为例探究花粉聚合的适应意义

被子植物的花粉以单粒或者多粒聚集在一起的方式进行散布。聚合花粉虽然可增加一次访花移出花粉数量或降低花粉丢失，但来源相同的花粉落置在同一柱头，会引起内部的雄性配子竞争。兰科植物的花粉块作为花粉聚合的极端形式，从花粉囊中移出是整块一次带出，但在落置柱头时，通过花粉小块可能会到达多朵花，因此，解释兰花花粉块的演化需要更多地从花粉落置和后续阶段考虑。但前人的研究缺乏对聚合花粉落置过程的定量分析，聚合花粉导致的配子竞争改变影响繁殖成功的实验证据仍然缺乏。因此，我们计划选择花粉聚合程度差异明显的两种兰科玉凤花属植物（粉叶玉凤花和落地金钱）为对象，比较其花粉聚合程度，追踪花粉块移动，调查聚合花粉对花粉落置效率、延迟落置程度和柱头花粉多样性的影响，结合多花粉来源混合授粉实验来验证配子竞争水平改变对植物繁殖成功的影响。该项目旨在探寻兰花花粉聚合变异的原因，为聚合花粉包装策略的适应性意义研究提供新证据。

Mature pollen grains are separated in most angiosperms but numerous grains are aggregated in some groups. Although aggregated pollen could increase pollen removal per visit and/or reduce pollen loss during transfer, the following deposition of pollen from the same donor onto one stigma may reduce male fitness in principle (mate competition). Pollinia, as the most evolved aggregated pollen, can be removed from anthers by just one efficient visit, while in Orchidaceae one pollinium could be deposited on stigmas of different flowers through massulae (pollen carryover), indicating that the explanation of pollen aggregation phenomenon in Orchidaceae needs more effort on the stigmatic pollen deposition stage and the stage following. However, the quantitative effect of aggregated pollen on stigmatic pollen deposition and the following mate competition on reproductive success still remains unexplored. To investigate the effect of aggregated pollen on stigmatic pollen deposition and reproductive success in Orchidaceae, our proposal plans to (1) quantify their pollen aggregation agree and investigate their effect on pollen deposition, pollen carryover and stigmatic pollen diversity in Habenaria glaucifolia and H. aitchisonii which degree of pollen aggregation is different between the two species ; (2) conduct pollination experiment with pollen mixture from different plants or multiple massulae to test the effect of mate competition on reproductive success. The proposal aims to investigate the cause of pollen aggregation variation in Orchidaceae, and provide a better understanding of the adaptive significance of the packaging strategy of pollen aggregation in angiosperms.