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 Croatia. Needles 1-, 2- and 3-years old were studied using a scanning electron microscope and energy dispersive X-ray microanalysis. Induced changes in the appearance and quantity of surface wax were recorded for the samples collected near to the cement factory. In particular, crystalline wax in suprastomatal cavities appeared to coalesce, and subsequently additional amorphous wax formed round the rim of the stoma. The majority of surface calcium detected was associated with the amorphous wax. It was unclear whether this was the result of passive discharge of the calcium with the wax from the epistomatal chamber, or resulted from the soft wax trapping cement dust particles on the needle surface. In either case plugging of stomata appears to have an adverse affect on the health of the trees. (C) 1999 Elsevier Science B.V. All rights reserved.