Timerman David, Greene David F, Urzay Javier, Ackerman Josef D
Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, Canada H4B 1R6
Department of Geography, Planning and Environment, Concordia University, 1455 de Maisonneuve West, Montreal, Quebec, Canada H3G 1M8.
J R Soc Interface. 2014 Dec 6;11(101):20140866. doi: 10.1098/rsif.2014.0866.
In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind-stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems.
在风媒传粉过程中，花粉从花药释放到气流中决定了可供传粉的花粉数量和时间。尽管花粉释放具有生态和进化上的重要性，但风与雄蕊之间的相互作用以及将花粉粒送入气流的具体力量却鲜为人知。我们提供了实证证据，表明大气湍流直接作用于广布的风媒杂草披针叶车前的雄蕊，引发共振振动，从而释放出间歇性的花粉粒。在实验室实验中，我们表明雄蕊具有的机械特性与理论预测的湍流驱动共振振动范围相符。以雄蕊的特征共振频率对其进行机械激发会使其产生共振，大量散落花粉。由于花药质量的减少，每次散落花粉后雄蕊的特征固有频率会随时间增加，这增加了触发后续散落所需的机械能。在湍流风条件下对一个自然种群的实地观察结果与这些实验室结果一致，并表明花粉是从由小涡旋激发而共振的雄蕊中释放出来的，这些小涡旋的周转周期与在实验室中测得的特征共振频率相似。湍流驱动雄蕊在共振时振动可能是风媒被子植物花粉散落的主要机制。在风中释放花粉的能力可被视为区分虫媒植物和风媒植物的一个主要因素，并且对诸如阻尼比和抗弯刚度等性状的选择可能在传粉系统的进化转变中具有重要意义。
