SEASONAL-CHANGES OF LEAF SURFACE CONTAMINATION IN BEECH, OAK, AND GINKGO IN RELATION TO LEAF MICROMORPHOLOGY AND WETTABILITY

The leaf surfaces of beech, oak and ginkgo have been investigated with respect to contamination with particles during one growing season. Ba sed on the observation that particles are removed from water-repellent leaves by rain (Lotus effect) the three species were selected because they differ in leaf surface micromorphology and wettability. Leaves o f beech are smooth, lacked wax crystals and were +/-wettable. Those of ginkgo were rough because their cells were convex and were densely co vered by wax crystals, resulting in permanent water repellency. Leaves of oak were covered by waxes and were water repellent when young, but , a few weeks after leaf expansion had ceased the waxes were rapidly e roded. These differences in wettability resulted in different amounts of contamination. Ginkgo collected a very small number of particles du ring the whole vegetation period. In beech the contamination was signi ficantly higher, but fairly constant, whereas oak leaves accumulated p articles with age.