n-Alkane distribution of leaves of Psidium guajava exposed to industrial air pollutants

The distribution of n-alkanes of foliar epicuticular waxes of Psidium guajava (Myrtaceae) exposed to air pollutants was determined by GC-EIMS. Saplings were exposed for two periods of one year (July 2000–June 2001 and December 2000–November 2001) in two experimental sites: Pilões River Valley (PV), where the contamination of air pollutants is relatively low, and Mogi River Valley (MV), which is severely affected by pollutants released by chemical, fertilizer, ceramic, iron and steel industries. On average, total leaf waxes were higher for plants that were exposed initially in the rainy season (December). Leaf waxes showed different n-alkane composition comparing both sites, especially during the first period of exposure (July 2000–June 2001). The main n-alkane waxes in both areas were C25, C26 and C27. However, in both experimental periods, an increase of the relative amounts of homologous of shorter carbon chains (C18–C23) under pollutants influence was observed. While the total percents of such homologues were on average 9.5 and 10.2 at PV for the first and second experimental periods, the observed percents at MV were on average 15.6 and 13.7, respectively. The results of the present work are in agreement with previous findings that air pollutants affect the synthesis of surface waxes, leading to alterations of the distribution of wax constituents.