Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China.
Institute for Peat and Mire Research, Northeast Normal University, State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Changchun, China.
PLoS One. 2014 Jan 27;9(1):e86581. doi: 10.1371/journal.pone.0086581. eCollection 2014.
The selective pressure imposed by maximizing male fitness (pollen dispersal) in shaping floral structures is increasingly recognized and emphasized in current plant sciences. To maximize male fitness, many flowers bear a group of stamens with temporally separated anther dehiscence that prolongs presentation of pollen grains. Such an advantage, however, may come with a cost resulting from interference of pollen removal by the dehisced anthers. This interference between dehisced and dehiscing anthers has received little attention and few experimental tests to date. Here, using one-by-one stamen movement in the generalist-pollinated Parnassia palustris, we test this hypothesis by manipulation experiments in two years. Under natural conditions, the five fertile stamens in P. palustris flowers elongate their filaments individually, and anthers dehisce successively one-by-one. More importantly, the anther-dehisced stamen bends out of the floral center by filament deflexion before the next stamen's anther dehiscence. Experimental manipulations show that flowers with dehisced anther remaining at the floral center experience shorter (1/3-1/2 less) visit durations by pollen-collecting insects (mainly hoverflies and wasps) because these 'hungry' insects are discouraged by the scant and non-fresh pollen in the dehisced anther. Furthermore, the dehisced anther blocks the dehiscing anther's access to floral visitors, resulting in a nearly one third decrease in their contact frequency. As a result, pollen removal of the dehiscing anther decreases dramatically. These results provide the first direct experimental evidence that anther-anther interference is possible in a flower, and that the selection to reduce such interferences can be a strong force in floral evolution. We also propose that some other floral traits, usually interpreted as pollen dispensing mechanisms, may function, at least partially, as mechanisms to promote pollen dispersal by reducing interferences between dehisced and dehiscing anthers.
目前植物科学越来越认识到并强调，最大限度地提高雄性适合度（花粉传播）对花部结构的选择压力。为了最大限度地提高雄性适合度，许多花具有一组雄蕊，其花药具有时间上分离的开裂，从而延长花粉粒的呈现。然而，这种优势可能会带来代价，因为开裂的花药会干扰花粉的去除。到目前为止，这种开裂的和开裂的花药之间的干扰很少受到关注，也很少进行实验测试。在这里，我们使用广布传粉的帕纳西亚·帕卢斯特里斯（Parnassia palustris）中的雄蕊逐个移动，通过两年的操作实验来检验这一假设。在自然条件下，帕纳西亚·帕卢斯特里斯（Parnassia palustris）花朵的五枚可育雄蕊单独伸长花丝，花药逐个依次开裂。更重要的是，在另一枚雄蕊的花药开裂之前，花药开裂的雄蕊通过花丝弯曲离开花的中心。实验操作表明，由于这些“饥饿”的昆虫因开裂的花药中花粉稀少且不新鲜而受挫，留在花中心的开裂花药的花朵会经历更短的（1/3-1/2 ）访问时间花粉收集昆虫（主要是食蚜蝇和黄蜂）。此外，开裂的花药会阻止正在开裂的花药接触到花的访客，导致它们的接触频率几乎减少三分之一。因此，正在开裂的花药的花粉去除率大大降低。这些结果首次提供了直接的实验证据，证明花药-花药干扰在花朵中是可能的，并且减少这种干扰的选择可以成为花进化中的一个强大力量。我们还提出，一些其他的花部特征，通常被解释为花粉分配机制，可能至少部分地作为减少开裂的和开裂的花药之间干扰的机制来促进花粉传播。
