Reactions to cement factory dust contamination by Pinus halepensis needles

Comparisons were made between the surfaces of Pinus halepensis needles from a site with relatively clean air, and one near to a cement factory in Croa tia. Needles 1-, 2- and 3-years old were studied using a scanning electron microscope and energy dispersive X-ray microanalysis. Induced changes in th e appearance and quantity of surface wax were recorded for the samples coll ected near to the cement factory. In particular, crystalline wax in suprast omatal cavities appeared to coalesce, and subsequently additional amorphous wax formed round the rim of the stoma. The majority of surface calcium det ected was associated with the amorphous wax. It was unclear whether this wa s the result of passive discharge of the calcium with the wax from the epis tomatal chamber, or resulted from the soft wax trapping cement dust particl es on the needle surface. In either case plugging of stomata appears to hav e an adverse affect on the health of the trees. (C) 1999 Elsevier Science B .V. All rights reserved.