Modified activity of the ground meristem and tissue differentiation in Schinus molle L. under cadmium contamination

Abstract

Previous works show the development of thicker mature leaves in tolerant plants growing under cadmium (Cd) contamination. The aim of this study was to evaluate the Cd effects in the leaf meristems in the tolerant species Schinus molle. Plants were grown in nutrient solution containing 0, 10 and 50 µM of Cd. Anatomical analysis was performed in the leaf primordia sampled at regular time intervals. Under the lowest cadmium level (10 µM) increased ground meristem thickness, diameter of the cells; cell elongation rate and the leaf dry mass were found. However, 50 µM of Cd reduced all these variables. In addition, the cells of the ground meristem of S. molle leaf primordia became larger when exposed to cadmium. Epidermis, palisade parenchyma and vascular tissues developed earlier in Cd-exposed leaves. The modifications found in the ground meristem may be related to the development of thicker leaves in S. molle plants exposed to low Cd levels. Older leaves showed higher Cd content compared to the younger ones, preventing toxicity to the more functional organs. Thus, low Cd concentrations promote changes in the ground meristem reflecting on the development of thicker and enhanced leaves.