Abstract: 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.

Key words: Fishery resources, Marine geographic information system, Spatial heterogeneity, Semivariogram, Spatial autocorrelation