一旦将这个环氧树脂“花瓣”垂直放置，蜜蜂便需要用其表面上的隆起保持平衡。
（图片提供:Beverley Glover）
为了喝到美味的花蜜，一只大黄蜂不得不在摇摆的花瓣间保持身体的平衡。根据一项新的研究，蜜蜂在采蜜的过程中得到了植物的帮助。在80%的开花植物中发现的锥形细胞提供了一个坚实的落脚点，并且使授粉的机会大为增加。
从上世纪70年代开始，科学家便一直在争论这些细胞，即所谓的锥形表皮细胞的功能。一些学者认为，通过改善花的颜色或是将植物的温度升高一到两摄氏度——这将有利于花蜜的形成，锥形表皮细胞能够让花对蜜蜂产生更大的吸引力。然而英国剑桥大学的植物分子生物学家Beverley Glover却提出了一个完全不同的假设：这些细胞能够为蜜蜂提供附着摩擦力。
Glover指出：“在野外，一朵花绝对不是一个静止的大餐盘。”她说，尽管花会随着风摆动，但这些细胞使得蜜蜂能够站稳脚跟，从而大大增加了授粉的可能性，这或许是进化的结果。
为了排除锥形表皮细胞的颜色和气味的功能，Glover和同事制造了一个金鱼草花瓣的白色、无味儿的环氧树脂模型。这个模型的表面不是平面就是模拟锥形表皮细胞的锥形隆起线纹。而花瓣中的小管道里则填充了蔗糖。
当这个模型水平放置时，平面和“崎岖”的花瓣对蜜蜂具有同等的吸引力。然而，一旦将这个模型按照一定的角度或垂直放置，蜜蜂则更愿意选择那些具有粗糙表面的花瓣。研究人员在最近的《当代生物学》杂志网络版上报告了这一研究成果。用高速录像机进行的分析显示，当蜜蜂在粗糙的花瓣模型上降落时，它们将所有的脚都插入花瓣表面，并停止拍打翅膀，进而从容地进餐。然而，当蜜蜂试图在平滑的花瓣上采蜜时，它们中间的腿会在花瓣表面胡乱地爬行，同时猛烈地拍打翅膀。
美国加利福尼亚大学里弗赛德分校的退休进化生态学家Nickolas Waser表示：“拍打翅膀使蜜蜂浪费了大量的能量。”Waser指出，“动物希望在尽可能短的时间里获得尽可能多的能量，因此，一个让它们能够在吃饭的时候保存更多能量的表面对蜜蜂而言具有重要的意义。”（生物谷Bioon.com）
生物谷推荐原始出处：
Current Biology, 14 May 2009 doi:10.1016/j.cub.2009.04.051
Conical Epidermal Cells Allow Bees to Grip Flowers and Increase Foraging Efficiency
Heather M. Whitney1,4,Lars Chittka2,Toby J.A. Bruce3andBeverley J. Glover1,,
1 Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
2 Research Centre for Psychology, School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
3 Department of Biological Chemistry, Rothamsted Research, Harpenden AL5 2JQ, UK
4 Present Address: School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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 [1,2]. The location and frequency of conical cells have led to speculation that they play a role in attracting animal pollinators [1,3,4]. Snapdragon (Antirrhinum) mutants lacking conical cells have been shown to be discriminated against by foraging bumblebees [4]. 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 cellsbut 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.
