Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, Kiel, 24098, Germany.
Department N5, Donetsk Institute for Physics and Engineering, R. Luxemburg Str. 72, Donetsk 83112, Ukraine.
Sci Rep. 2017 Apr 3;7:45483. doi: 10.1038/srep45483.
Primary aerial surfaces of terrestrial plants are very often covered with three-dimensional epicuticular waxes. Such wax coverages play an important role in insect-plant interactions. Wax blooms have been experimentally shown in numerous previous studies to be impeding locomotion and reducing attachment of insects. Among the mechanisms responsible for these effects, a possible adsorption of insect adhesive fluid by highly porous wax coverage has been proposed (adsorption hypothesis). Recently, a great decrease in insect attachment force on artificial adsorbing materials was revealed in a few studies. However, adsorption ability of plant wax blooms was still not tested. Using a cryo scanning electron microscopy approach and high-speed video recordings of fluid drops behavior, followed by numerical analysis of experimental data, we show here that the three-dimensional epicuticular wax coverage in the waxy zone of Nepenthes alata pitcher adsorbs oil: we detected changes in the base, height, and volume of the oil drops. The wax layer thickness, differing in samples with untreated two-layered wax coverage and treated one-layered wax, did not significantly affect the drop behavior. These results provide strong evidence that three-dimensional plant wax coverages due to their adsorption capability are in general anti-adhesive for insects, which rely on wet adhesion.
陆生植物的初级气生表面通常覆盖着三维的表皮蜡。这种蜡覆盖物在昆虫与植物的相互作用中起着重要的作用。在许多先前的研究中，蜡花已被实验证明会阻碍昆虫的运动并减少其附着。在这些效应的作用机制中，有人提出昆虫粘性液体可能被高度多孔的蜡覆盖物吸附（吸附假说）。最近，一些研究揭示了昆虫在人工吸附材料上的附着力大大降低。然而，植物蜡花的吸附能力仍未得到测试。使用冷冻扫描电子显微镜方法和高速视频记录流体滴的行为，以及对实验数据进行数值分析，我们在这里表明，蜡质区的 Nepenthes alata 瓶状叶的三维表皮蜡覆盖物吸附了油：我们检测到油滴的底部、高度和体积发生了变化。蜡层厚度在未经处理的双层蜡覆盖和处理过的单层蜡的样本中有所不同，但对液滴行为没有显著影响。这些结果有力地证明，由于其吸附能力，三维植物蜡覆盖物通常对依赖湿附的昆虫具有抗粘性。
