Influence of different air pollutants on the structure of needle wax of spruce (Picea abies [L.] Karsten)

With the help of the scanning electron microscope surface structures of spruces exposed to different sorts of air pollutants are examined. On the surface of unexposed spruce needles crystalline wax structures — hollow tubes — are visible covering the stomata rows on all sides of the needle and filling the stomatal antechamber with a close-knit mesh. Non-reactive dusts only mechanically disturb the wax structures; MgO-containing fine dusts influence the wax tubes in a more serious way: the wax tubes fuse and the crystalline structure is lost. X-ray-analysis of the deposited particles reveals Mg to be the dominating element. SO₂ also causes severe alterations of the wax structures; with oxidants as the main emission component the wax structures are nearly unaffected.