西安市常见绿化植物叶片润湿性能及其影响因素

Leaf surface wettability of major plant species for urban greening in Xi'an and related affecting factors

利用接触角测定仪测定了西安市21种常见绿化植物叶片表面的接触角,探讨了叶片表面特性如蜡质、绒毛、气孔对接触角的影响。结果表明,植物叶片正背面、物种间的接触角差异均显著,叶片正面和背面接触角大小在40°～140°。接触角大小与变异系数呈负相关,可能由于接触角小的润湿叶片在不同的生境和位置下,受到环境条件的影响较大而出现大的变异;接触角较大的非润湿性叶片,环境物质持留时间较短,对叶片形态和组成影响较小,因而出现小的变异。植物叶片表面的接触角随蜡质含量的升高而增大。表皮蜡质去除后大部分叶片接触角明显降低,尤其是疏水性较强的银杏(Ginkgo biloba)、月季(Ro-sa chinensis)和紫叶小檗(Berberis thunbergii)。女贞(Ligustrum lucidum)正背面、加杨(Popu-lus canadensis)背面等亲水型的叶片蜡质去除后接触角反而增大。叶片绒毛的多少及其形态、分布方式对接触角具有重要的影响,不同的作用方式表现出润湿和不润湿的特征,人为将其去除可以增加叶片的润湿性。背面气孔密度与气孔长度、保卫细胞长度呈负相关;接触角则与气孔密度呈负相关,与气孔长度呈正相关。

We measured the contact angle of water droplet on leaf surfaces of 21 major plant species for urban greening in Xi＇an,and studied the effects of leaf surface characteristics such as epidermal wax,trichomes,and stomata on the contact angle.There existed significant differences in the contact angle among test plant species and between adaxial and abaxial leaf surfaces.The contact angle ranged from 40° to 140°,and was negatively correlated with its coefficient of variance.The greater variance of the contact angle on wettable leaves could be related to the greater effects of dust,acid rain,and other environmental substances on the leaf surface structure;while for nonwettable leaves,the relatively short retained time of environmental substances gave smaller effects on the leaf surface structure and composition.The contact angle increased with increasing epidermal wax content.After the removal of epidermal wax by chloroform,the leaf contact angle of most plant species,especially of hydrophobic species Ginkgo biloba,Rosa chinensis and Berberis thunbergii,decreased significantly.On the contrary,the removal of epidermal wax increased the leaf contact angle of a few hydrophilic species,such as the adaxial and abaxial leaf contact angle of Ligustrum lucidum and the abaxial leaf contact angle of Populus canadensis.The amount,morphology,and distribution of trichomes had great effects on the leaf contact angle.Different types of action pattern led to different wetting characteristics.Artificial removal of trichomes increased the leaf surface wettability.The stomatal density of abaxial leaf surface was negatively correlated with guard cell length and stomatal pore length,while the contact angle of abaxial leaf surface was negatively correlated with stomatal density and positively with stomatal pore length.