EFFECTS OF SO₂ AND OTHER AIR POLLUTANTS ON THE MORPHOLOGY OF EPICUTICULAR WAXES ON NEEDLES OF <i>PINUS STROBUS</i> AND <i>PINUS BANKSIANA</i>

Abstract

S ummary Exposure of elongating needles of Pinus strobus L. to SO 2 and other unidentified air pollutants delayed wax deposition in the epistomatal chambers. Following completion of wax deposition, the wax rodlets fused, forming plate like sheets. Needle wettability appeared to be increased as a result of modification of the epicuticular waxes, potentially increasing their sensitivity to acid rain‐induced injury. This occurred without alteration of the structure of the stomatal complex itself. No alteration of wax form was evident on needles of P. banksiana Lamb., even under conditions which led to acute SO 2 foliar injury.