Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7635-9. doi: 10.1073/pnas.0911223107. Epub 2010 Apr 19.
Upon release from the anther, pollen grains of angiosperm flowers are exposed to a dry environment and dehydrate. To survive this process, pollen grains possess a variety of physiological and structural adaptations. Perhaps the most striking of these adaptations is the ability of the pollen wall to fold onto itself to prevent further desiccation. Roger P. Wodehouse coined the term harmomegathy for this folding process in recognition of the critical role it plays in the survival of the pollen grain. There is still, however, no quantitative theory that explains how the structure of the pollen wall contributes to harmomegathy. Here we demonstrate that simple geometrical and mechanical principles explain how wall structure guides pollen grains toward distinct folding pathways. We found that the presence of axially elongated apertures of high compliance is critical for achieving a predictable and reversible folding pattern. Moreover, the intricate sculpturing of the wall assists pollen closure by preventing mirror buckling of the surface. These results constitute quantitative structure-function relationships for pollen harmomegathy and provide a framework to elucidate the functional significance of the very diverse pollen morphologies observed in angiosperms.
花粉粒从花药释放出来后，会暴露在干燥的环境中并脱水。为了在这个过程中存活下来，花粉粒具有多种生理和结构上的适应性。其中最显著的适应之一是花粉壁能够折叠到自身上，以防止进一步的干燥。Roger P. Wodehouse 创造了“harmomegathy”这个术语来形容这个折叠过程，以表彰它在花粉粒生存中所扮演的关键角色。然而，目前还没有一个定量的理论可以解释花粉壁的结构如何有助于 harmomegathy。在这里，我们证明了简单的几何和力学原理可以解释花粉壁的结构如何引导花粉粒走向不同的折叠途径。我们发现，具有高顺应性的轴向伸长孔的存在对于实现可预测和可逆的折叠模式至关重要。此外，壁的精细雕刻通过防止表面的镜像屈曲来辅助花粉的闭合。这些结果构成了花粉 harmomegathy 的定量结构-功能关系，并为阐明被子植物中观察到的非常多样化的花粉形态的功能意义提供了一个框架。
