Anatomia e trocas gasosas de Heteranthera reniformis Ruiz & Pav. em resposta ao Cromo

Abstract

Macrophytes are able to absorb elements, through phytoremediation, attenuating pollutants in the environment efficiently and cheaply. Here, the objective was to evaluate the tolerance of Heteranthera reniformis to chromium, through anatomical and physiological characteristics. The source of chromium used for 15 days was: 0; 20; 40; 80; 160 and 320 mg L‐1. Gas exchange with IRGA equipment was evaluated. The root and leaf samples dehydrated, infiltrated and included in hydroxyethyl methacrylate for the preparation of slides. Parathermic sections were obtained by free hand, clarified and stained to capture the images. Histological data were analyzed using the Sisvar software. At the root, the cortex presented reduction, the epidermis, endoderm and exoderm presented thickening. The adaxial epidermis of the leaf and chlorophyllous parenchyma reduced and the spongy parenchyma was thickened. There was reduction of the stomatal density, polar and equatorial diameters. No effect of the treatments under the gas exchange variables was observed, demonstrating that H.reniformis responses were not negatively influenced by the metal. The modifications related to the apoplastic barriers can be considered a mechanism favorable to the tolerance and can contribute to the maintenance of the characteristics of gas and stomatal exchanges in the presence of chromium.