Whitney Heather M, Chittka Lars, Bruce Toby J A, Glover Beverley J
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
Curr Biol. 2009 Jun 9;19(11):948-53. doi: 10.1016/j.cub.2009.04.051. Epub 2009 May 14.
The plant surface is by default flat, and development away from this default is thought to have some function of evolutionary advantage. Although the functions of many plant epidermal cells have been described, the function of conical epidermal cells, a defining feature of petals in the majority of insect-pollinated flowers, has not. The location and frequency of conical cells have led to speculation that they play a role in attracting animal pollinators. Snapdragon (Antirrhinum) mutants lacking conical cells have been shown to be discriminated against by foraging bumblebees. Here we investigated the extent to which a difference in petal surface structure influences pollinator behavior through touch-based discrimination. To isolate touch-based responses, we used both biomimetic replicas of petal surfaces and isogenic Antirrhinum lines differing only in petal epidermal cell shape. We show that foraging bumblebees are able to discriminate between different surfaces via tactile cues alone. We find that bumblebees use color cues to discriminate against flowers that lack conical cells--but only when flower surfaces are presented at steep angles, making them difficult to manipulate. This facilitation of physical handling is a likely explanation for the prevalence of conical epidermal petal cells in most flowering plants.
植物表面默认是平的，偏离这种默认状态的发育被认为具有某种进化优势功能。尽管已经描述了许多植物表皮细胞的功能，但圆锥形表皮细胞的功能尚未明确，而圆锥形表皮细胞是大多数虫媒花花瓣的一个显著特征。圆锥形细胞的位置和分布频率引发了一种推测，即它们在吸引动物传粉者方面发挥作用。已经证明，缺乏圆锥形细胞的金鱼草（Antirrhinum）突变体不被觅食的大黄蜂所青睐。在这里，我们研究了花瓣表面结构差异通过基于触觉的辨别对传粉者行为的影响程度。为了分离基于触觉的反应，我们使用了花瓣表面的仿生复制品以及仅在花瓣表皮细胞形状上有所不同的同基因金鱼草品系。我们发现，觅食的大黄蜂仅通过触觉线索就能区分不同的表面。我们还发现，大黄蜂利用颜色线索来区分缺乏圆锥形细胞的花朵——但只有当花朵表面以陡峭角度呈现，使其难以操作时才会如此。这种对物理操作的便利可能解释了大多数开花植物中圆锥形表皮花瓣细胞普遍存在的原因。
