Anatomia e fisiologia de plantas de Schinus molle L. (Anacardiaceae) expostas ao cádmio mecanismos de tolerância e potencial para fitorremediação

Abstract

This work aimed at evaluating the potential for phytoremediation of the Schinus molle woody species when exposed to different concentrations of Cadmium (Cd), in addition to the anatomical and physiological mechanisms related with tolerance. Experiments were assembled with seven month old S. molle plants exposing them to different concentrations of cadmium [0, 10, 20, 50, 125 and 250mM Cd (NO3)2] for a period of 90 days. After the experimental period, we evaluated variables related to: photosynthesis, growth, tolerance, nutritional status of the plants and root and leaf anatomy. The data were submitted to analysis of variance and the means compared by the Scott-Knott test or submitted to regression. The S. molle species presents tolerance index above 80% for concentrations up to 20mM of Cd. The main Cd tolerance mechanism was the compartmentalization of this element in the roots and the decrease in the translocation to the shoots by means of the formation of apoplastic barriers. With up to 20µM of Cd the S. molle leaves presented beneficial characteristics, such as thickening of the mesophyll. However, starting at 50mM, the thickness of the mesophyll decreases and this species presents a decrease in size and stomata density in the presence of Cd. The Cd concentration in the shoot remains low and the tolerance index below 100% may indicate that S. molle does not present a good performance for phyto-stabilization in highly contaminated sites. However, due to the moderate tolerance displayed by the species, field studies are necessary in order to evaluate the potential of the same for the phyto-stabilization of areas contaminated with Cd.