Acúmulo foliar de enxofre e suas relações com alterações no crescimento de plantas jovens de Tibouchina pulchra Cogn. (Melastomataceae) expostas nas proximidades do polo industrial de Cubatão, SP

Abstract

Acúmulo foliar de enxofre e suas relações com alterações no crescimento de plantas jovens de Tibouchina pulchra Cogn. (Melastomataceae) expostas nas proximidades do polo industrial de Cubatão, SP 1 ABSTRACT-(Foliar sulfur accumulation and its relations with changes in growth of saplings of Tibouchina pulchra Cogn. (Melastomataceae) exposed around the industrial complex of Cubatão, SP, Brazil). The aim of this study was to verify, under field conditions, if SO 2 imissions from the industrial complex of Cubatão, since absorbed and accumulated in leaves, may cause changes in the growth of saplings of T. pulchra. The study was performed along 1997 by exposing potted plants during three consecutive periods of 16 weeks in three sites: Pilões river valley (RP; under low levels of SO 2); Caminho do Mar and Mogi river valley (CM and VM respectively; under high SO 2). After each exposure, foliar accumulation of sulfur and changes in growth and biomass parameters, besides the statistical relations among them, were determined. Significant foliar accumulation of sulfur was observed in plants exposed at CM (exposures 1 to 3) and at VM (exposures 2 and 3). The growth of plants from both polluted sites was strongly modified, especially height and number of leaves and branches. Changes in biomass of leaves, stem+branches and roots were rarely detected, but significant reductions in the root/shoot ratio were observed in plants exposed at CM and VM (exposures 1 and 3). The decrease in height and in stem+branch and root biomass (exposure 2) and the increase in height and in leaf and branch production, as well as the decrease in number of leaves (main stem), in root biomass and in root/shoot ratio (exposure 3) were significantly explained by the accumulation of sulfur in leaves (p < 0.01).