Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, Tübingen 72076, Germany.
Institute of Botany, Technical University of Dresden, Zellescher Weg 20b, Dresden 01217, Germany.
J R Soc Interface. 2021 Dec;18(185):20210676. doi: 10.1098/rsif.2021.0676. Epub 2021 Dec 15.
The floating leaves of the aquatic fern are covered by superhydrophobic hairs (=trichomes) which are shaped like egg-beaters. These trichomes cause high water repellency and stable unwettability if the leaf is immersed. Whereas hairs are technically interesting, there remains also the question concerning their biological relevance. has its origin in Brazil within a region exposed to intense rainfall which easily penetrates the trichome cover. In this study, drop impact on leaves of were analysed using a high-speed camera. The largest portion of the kinetic energy of a rain drop is absorbed by elastic responses of the trichomes and the leaf. Although rain water is mostly repelled, it turned out that the trichomes hamper swift shedding of rain water and some residual water can remain below the 'egg-beaters'. Drops rolling over the trichomes can, however, 'suck up' water trapped beneath the egg-beaters because the energetic state of a drop on top of the trichomes is-on account of the superhydrophobicity of the hairs-much more favourable. The trichomes may therefore be beneficial during intense rainfall, because they absorb some kinetic energy and keep the leaf base mostly free from water.
水生蕨类植物的漂浮叶片被超疏水的毛发（=刚毛）覆盖，这些毛发的形状像打蛋器。如果叶片浸入水中，这些刚毛会导致高的水斥力和稳定的不湿性。虽然毛发在技术上很有趣，但它们的生物学相关性仍然存在疑问。 起源于巴西的一个地区，该地区经常遭受强降雨的侵袭，强降雨很容易穿透刚毛覆盖层。在这项研究中，使用高速摄像机分析了雨滴对 的叶片的冲击。雨滴的大部分动能被刚毛和叶片的弹性响应吸收。尽管雨水大部分被排斥，但事实证明，这些刚毛阻碍了雨水的迅速排出，一些残留的水可能会留在“打蛋器”下面。然而，在刚毛上滚动的液滴可以“吸起”被困在打蛋器下面的水，因为处于刚毛顶部的液滴的能量状态——由于毛发的超疏水性——要有利得多。因此，在强降雨期间，刚毛可能是有益的，因为它们吸收了一些动能，并使叶片基部大部分保持无水状态。
