Division of Plant Ecology and Systematics, Biology Department, University of Leuven, Heverlee, Belgium; Terrestrial Ecology Unit, Department of Biology, Ghent University, Ghent, Belgium.
Plant Biol (Stuttg). 2014 May;16(3):669-76. doi: 10.1111/plb.12097. Epub 2013 Sep 20.
To increase the accuracy of pollen capture and transfer by pollinators some plant species have developed secondary pollen presentation structures. Because the presence of secondary pollen presentation structures at the pistil may reduce the spatial separation between the sexual functions and increase the risk of self-interference and selfing, temporal segregation of the sexual organs, triggered by visiting insects, can be expected to occur. We investigated secondary pollen presentation and the temporal dynamics of the sexual phases in combination with the physiological self-incompatibility system in Campanula trachelium, a protandrous insect-pollinated herb. Stylar hair retraction (male function) and curling of the stigmatic lobes (female function) were modelled using Gompertz growth functions. Finally, we performed pollination experiments in the lab and field to assess seed set and pollen limitation under natural conditions. About 68% of the total pollen load was captured by stylar hairs. Manual manipulation of the stylar hairs, mimicking pollinator visitation, significantly shortened the male phase and accelerated the female phase, resulting in a significant decline in temporal overlap between the two sexual functions. Conversely, when pollinators and/or manual manipulations were lacking, the male phase was substantially prolonged and sexual overlap was maximal. This suggests that spreading of the sexual phases and thus the risk of sexual interference are largely determined by the interaction between stylar hairs and visiting pollinators. Natural seed set was high and not pollinator limited. Overall, these results indicate that secondary pollen presentation and partial protandry resulted in efficient pollen capture, transfer and deposition.
为了提高传粉媒介对花粉的捕获和传递的准确性，一些植物物种已经进化出了次生花粉展示结构。由于柱头处次生花粉展示结构的存在可能会减少有性器官之间的空间分离，并增加自干扰和自交的风险，因此可以预期，有访花昆虫触发的性器官的时间隔离会发生。我们调查了次生花粉展示和性相的时间动态，同时结合生理上自交不亲和系统，研究了风铃草属的一个雌雄异熟的传粉草本植物。花柱毛的缩回（雄性功能）和柱头裂片的卷曲（雌性功能）使用 Gompertz 生长函数进行建模。最后，我们在实验室和野外进行了授粉实验，以评估在自然条件下的种子结实率和花粉限制。大约 68%的总花粉负荷被花柱毛捕获。模拟传粉者访问的花柱毛手动操作显著缩短了雄性阶段并加速了雌性阶段，导致两个性功能之间的时间重叠显著减少。相反，当缺少传粉者和/或手动操作时，雄性阶段会大大延长，性重叠达到最大值。这表明，性相的扩展以及性干扰的风险在很大程度上取决于花柱毛和来访传粉者之间的相互作用。自然种子结实率高，不受传粉者限制。总的来说，这些结果表明，次生花粉展示和部分雌雄异熟导致了高效的花粉捕获、传递和沉积。
