Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Ghent, Belgium.
Department of Biology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium.
Plant J. 2020 Jul;103(2):769-780. doi: 10.1111/tpj.14770. Epub 2020 May 3.
Foliar water uptake (FWU), the direct uptake of water into leaves, is a global phenomenon, having been observed in an increasing number of plant species. Despite the growing recognition of its functional relevance, our understanding of how FWU occurs and which foliar surface structures are implicated, is limited. In the present study, fluorescent and ionic tracers, as well as microcomputed tomography, were used to assess potential pathways for water entry in leaves of beech, a widely distributed tree species from European temperate regions. Although none of the tracers entered the leaf through the stomatal pores, small amounts of silver precipitation were observed in some epidermal cells, indicating moderate cuticular uptake. Trichomes, however, were shown to absorb and redistribute considerable amounts of ionic and fluorescent tracers. Moreover, microcomputed tomography indicated that 72% of empty trichomes refilled during leaf surface wetting and microscopic investigations revealed that trichomes do not have a cuticle but are covered with a pectin-rich cell wall layer. Taken together, our findings demonstrate that foliar trichomes, which exhibit strong hygroscopic properties as a result of their structural and chemical design, constitute a major FWU pathway in beech.
叶面水分吸收（FWU），即水直接进入叶片的过程，是一种全球性现象，在越来越多的植物物种中都有观察到。尽管人们越来越认识到它的功能相关性，但我们对 FWU 如何发生以及哪些叶面结构与之相关的理解还很有限。在本研究中，荧光和离子示踪剂以及微计算机断层扫描技术被用于评估欧洲温带地区广泛分布的山毛榉叶片中水分进入的潜在途径。尽管示踪剂都没有通过气孔进入叶片，但在一些表皮细胞中观察到了少量的银沉淀，表明存在中度的角质层吸收。然而，研究表明，绒毛能够吸收和重新分配大量的离子和荧光示踪剂。此外，微计算机断层扫描技术表明，在叶片表面润湿过程中，72%的空绒毛重新充满水分，微观研究表明，绒毛没有角质层，而是被一层富含果胶的细胞壁覆盖。综上所述，我们的研究结果表明，山毛榉叶片的绒毛由于其结构和化学设计而具有强烈的吸湿性，是山毛榉叶片水分吸收的主要途径。
