表皮细胞的润湿性与表面微观结构及花瓣结构化角质层之间关系的理论研究方法。
A theoretical approach to the relationship between wettability and surface microstructures of epidermal cells and structured cuticles of flower petals.
作者信息
Taneda Haruhiko, Watanabe-Taneda Ayako, Chhetry Rita, Ikeda Hiroshi
机构信息
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-0033, Japan, National Herbarium and Plant Laboratories, Department of Plant Resources, Kathomandu, Nepal and The University Museum, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-0033, Japan
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-0033, Japan, National Herbarium and Plant Laboratories, Department of Plant Resources, Kathomandu, Nepal and The University Museum, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-0033, Japan.
出版信息
Ann Bot. 2015 May;115(6):923-37. doi: 10.1093/aob/mcv024. Epub 2015 Apr 7.
BACKGROUND AND AIMS
The epidermal surface of a flower petal is composed of convex cells covered with a structured cuticle, and the roughness of the surface is related to the wettability of the petal. If the surface remains wet for an excessive amount of time the attractiveness of the petal to floral visitors may be impaired, and adhesion of pathogens may be promoted. However, it remains unclear how the epidermal cells and structured cuticle contribute to surface wettability of a petal.
METHODS
By considering the additive effects of the epidermal cells and structured cuticle on petal wettability, a thermodynamic model was developed to predict the wetting mode and contact angle of a water droplet at a minimum free energy. Quantitative relationships between petal wettability and the geometries of the epidermal cells and the structured cuticle were then estimated. Measurements of contact angles and anatomical traits of petals were made on seven herbaceous species commonly found in alpine habitats in eastern Nepal, and the measured wettability values were compared with those predicted by the model using the measured geometries of the epidermal cells and structured cuticles.
KEY RESULTS
The model indicated that surface wettability depends on the height and interval between cuticular steps, and on a height-to-width ratio for epidermal cells if a thick hydrophobic cuticle layer covers the surface. For a petal epidermis consisting of lenticular cells, a repellent surface results when the cuticular step height is greater than 0·85 µm and the height-to-width ratio of the epidermal cells is greater than 0·3. For an epidermis consisting of papillate cells, a height-to-width ratio of greater than 1·1 produces a repellent surface. In contrast, if the surface is covered with a thin cuticle layer, the petal is highly wettable (hydrophilic) irrespective of the roughness of the surface. These predictions were supported by the measurements of petal wettability made on flowers of alpine species.
CONCLUSIONS
The results indicate that surface roughness caused by epidermal cells and a structured cuticle produces a wide range of petal wettability, and that this can be successfully modelled using a thermodynamic approach.
背景与目的
花瓣的表皮表面由覆盖着结构化角质层的凸起细胞组成，表面粗糙度与花瓣的润湿性有关。如果表面长时间保持湿润，花瓣对访花者的吸引力可能会受损，并且可能会促进病原体的附着。然而，目前尚不清楚表皮细胞和结构化角质层如何影响花瓣的表面润湿性。
方法
通过考虑表皮细胞和结构化角质层对花瓣润湿性的叠加效应，建立了一个热力学模型，以预测水滴在最小自由能下的润湿模式和接触角。然后估算了花瓣润湿性与表皮细胞几何形状和结构化角质层之间的定量关系。对尼泊尔东部高山栖息地常见的七种草本植物的花瓣接触角和解剖特征进行了测量，并将测得的润湿性值与使用表皮细胞和结构化角质层的测量几何形状由模型预测的值进行了比较。
关键结果
该模型表明，表面润湿性取决于角质层台阶的高度和间距，以及如果表面覆盖有厚疏水角质层时表皮细胞的高宽比。对于由透镜状细胞组成的花瓣表皮，当角质层台阶高度大于0.85μm且表皮细胞高宽比大于0.3时，会形成拒水表面。对于由乳头状细胞组成的表皮，高宽比大于1.1会产生拒水表面。相反，如果表面覆盖有薄角质层，则无论表面粗糙度如何，花瓣都具有高润湿性（亲水性）。对高山物种花朵的花瓣润湿性测量结果支持了这些预测。
结论
结果表明，表皮细胞和结构化角质层引起的表面粗糙度产生了广泛的花瓣润湿性，并且可以使用热力学方法成功地对其进行建模。
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