Jin Xiao-Fang, Ye Zhong-Ming, Amboka Grace M, Wang Qing-Feng, Yang Chun-Feng
Institute of Ecology and Environmental Science, Nanchang Institute of TechnologyNanchang, China.
Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of SciencesWuhan, China.
Front Plant Sci. 2017 May 10;8:783. doi: 10.3389/fpls.2017.00783. eCollection 2017.
A sensitive bilobed stigma is thought to assure reproduction, avoid selfing and promote outcrossing. In addition, it may also play a role in pollinator selection since only pollinators with the appropriate body size can trigger this mechanism. However, no experimental study has investigated how the sensitive stigma responds to different pollinators and its potential effects on pollination. (Phrymaceae), a plant with a bilobed stigma was studied to investigate the relationship between stigma behaviors and its multiple insect pollinators. The reaction time of stigma closure after touched, duration of temporary closure, and factors determining permanent closure of the stigma were studied when flowers were exposed to different visitors and conducted with hand pollination. Manual stimulation was also used to detect the potential differences in stigmas when touched with different degrees of external forces. Results indicated that, compared to pollinators with a small body size, larger pollinators transferred more pollen grains to the stigma, causing a rapid stigma response and resulting in a higher percentage of permanent closures. Duration of temporary closure was negatively correlated with the speed of stigma closure; a stigma that closed more rapidly reopened more slowly. Manual stimulation showed that reaction time of stigma closure was likely a response to external mechanical forces. Hand pollination treatments revealed that the permanent closure of a stigma was determined by the size of stigmatic pollen load. For large pollinators, the speedy reaction of the stigma might help to reduce pollen loss, enhance pollen germination and avoid obstructing pollen export. Stigmas showed low sensitivity when touched by inferior pollinators, which may have increased the possibility of pollen deposition by subsequent visits. Therefore, the stigma behavior in is likely a mechanism of pollinator selection to maximize pollination success.
人们认为，敏感的两裂柱头有助于确保繁殖、避免自花授粉并促进异花授粉。此外，它可能还在传粉者选择中发挥作用，因为只有体型合适的传粉者才能触发这一机制。然而，尚无实验研究调查敏感柱头如何对不同传粉者做出反应及其对授粉的潜在影响。对一种具有两裂柱头的透骨草科植物进行了研究，以探究柱头行为与其多种昆虫传粉者之间的关系。当花朵接触不同访客并进行人工授粉时，研究了柱头被触碰后闭合的反应时间、暂时闭合的持续时间以及决定柱头永久闭合的因素。还使用人工刺激来检测柱头在受到不同程度外力触碰时的潜在差异。结果表明，与体型较小的传粉者相比，体型较大的传粉者会将更多花粉粒转移到柱头上，导致柱头快速反应，从而使永久闭合的比例更高。暂时闭合的持续时间与柱头闭合速度呈负相关；闭合较快的柱头重新开放得较慢。人工刺激表明，柱头闭合的反应时间可能是对外部机械力的一种反应。人工授粉处理表明，柱头的永久闭合由柱头花粉负载量的大小决定。对于大型传粉者而言，柱头的快速反应可能有助于减少花粉损失、提高花粉萌发率并避免阻碍花粉输出。当受到劣质传粉者触碰时，柱头表现出较低的敏感性，这可能增加了后续访花时花粉沉积的可能性。因此，该植物的柱头行为可能是一种传粉者选择机制，以实现授粉成功率最大化。
