The leaf surfaces of beech, oak and ginkgo have been
investigated with respect to contamination with particles
during one growing season. Based 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 of beech are smooth, lacked wax crystals
and were ±wettable. Those of ginkgo were rough
because their cells were convex and were densely covered 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 eroded. These differences
in wettability resulted in different amounts of
contamination. Ginkgo collected a very small number of
particles during the whole vegetation period. In beech
the contamination was significantly higher, but fairly
constant, whereas oak leaves accumulated particles with age.