BIOPHYSICAL ASPECTS OF FOG DEPOSITION ON THE NEEDLES OF 3 CONIFERS

Fog depositional patterns on the needles of three conifers were examined experimentally using ultrasonically generated fog droplets containing a dilute fluorescent dye. Fluorescence microscopy analysis of deposition rates and patterns revealed that the mechanism of inertial impaction was of little importance under the imposed conditions. Gravitational sedimentation and diffusional transport may be important for Abies balsamea, but surface active mechanisms probably dominate for Picea rubens and, possibly, Pinus strobus. In young physiologically active needles of Picea rubens most of the fog was deposited on the epicuticular waxes which occlude epistomatal chambers. This non-random depositional pattern is discussed with reference to the sensitivity of Picea rubens to acidic fogs.