Laboratory of Plant Systematics and Evolutionary Biology, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
Ecology and Environment Monitoring and Scientific Research Center, Yangtze Basin Ecology and Environment Administration, Ministry of Ecology and Environment of the People's Republic of China, Wuhan, 430010, China.
Am J Bot. 2022 Jun;109(6):1004-1015. doi: 10.1002/ajb2.1865. Epub 2022 May 30.
Pollinator sharing of co-flowering plants may result in interspecific pollen receipt with a fitness cost. However, the underlying factors that determine the effects of heterospecific pollen (HP) are not fully understood. Moreover, the cost of stigma closure induced by HP may be more severe for plants with special touch-sensitive stigmas than for plants with non-touch-sensitive stigmas. Very few studies have assessed HP effects on stigma behavior.
We conducted hand-pollination experiments with 10 HP donors to estimate HP effects on stigma behavior and stigmatic pollen germination in Campsis radicans (Bignoniaceae) at low and high pollen loads. We assessed the role of phylogenetic distance between donor and recipient, pollen size, and pollen aperture number in mediating HP effects. Additionally, we observed pollen tube growth to determine the conspecific pollen-tube-growth advantage.
Stigma behavior differed significantly with HP of different species. Pollen load increased, while pollen size decreased, the percentage of permanent closure and stigmatic germination of HP. Stigmatic HP germination increased with increasing aperture number. However, HP effects did not depend on phylogenetic distance. In addition, conspecific pollen had a pollen-tube-growth advantage over HP.
Our results provide a good basis for understanding the stigma-pollen recognition process of plant taxa with touch-sensitive stigmas. We concluded that certain flowering traits drive the HP effects on the post-pollination period. To better understand the impact of pollinator sharing and interspecific pollen transfer on plant evolution, we highlight the importance of evaluating more factors that determine HP effects at the community level.
共花期植物的传粉者共享可能导致种间花粉接收，从而带来适应度成本。然而，决定异交花粉（HP）影响的潜在因素尚未完全了解。此外，与非触感敏感柱头的植物相比，HP 引起的柱头闭合的成本可能对具有特殊触感敏感柱头的植物更为严重。很少有研究评估 HP 对柱头行为的影响。
我们进行了 10 种 HP 供体的人工授粉实验，以评估 HP 对低和高花粉负荷下 Campsis radicans（紫葳科）柱头行为和柱头花粉萌发的影响。我们评估了供体和受体之间的系统发育距离、花粉大小和花粉孔数量在介导 HP 影响方面的作用。此外，我们观察了花粉管的生长情况，以确定同物种花粉管生长的优势。
柱头行为因不同物种的 HP 而异。花粉负荷增加，而花粉大小减小，HP 的柱头永久性闭合和柱头萌发的百分比增加。柱头 HP 萌发随孔数的增加而增加。然而，HP 影响并不取决于系统发育距离。此外，同物种花粉在花粉管生长方面具有优势。
我们的研究结果为理解具有触感敏感柱头的植物类群的柱头-花粉识别过程提供了良好的基础。我们得出结论，某些开花特征驱动了 HP 对授粉后阶段的影响。为了更好地理解传粉者共享和种间花粉转移对植物进化的影响，我们强调了在群落水平上评估更多决定 HP 影响的因素的重要性。
