Anatomical changes caused by boron in Calopogonium mucunoides Desv

Abstract

Soil contamination by toxic elements due to anthropic impacts negatively affects biodiversity. Some of these elements in low concentrations are micronutrients for plants, such as boron (B). This element plays a key role in various plant functions, including cell wall formation, maintenance of the structural and functional integrity of biological membranes. Calopogonium mucunoides is a herbaceous legume found in the Cerrado that is used for green manure and tolerates high concentrations of several metals. The morphophysiological and anatomical responses of this species have not yet been evaluated. The objective of this work was to characterize the anatomical alterations in leaves and roots of C. mucunoides caused under varying but high concentrations of B in the soil. The following concentrations of B: 0 (control), 30, 120 and 480 mg dm−3 were used. Anatomical changes were observed in the abaxial epidermis of leaves when exposed to a concentration of 30 mg dm−3. The roots showed changes in the primary xylem also at the concentration of 30 and the concentration of 480 mg dm−3 affects the development of secondary tissue growth. Starch grains were detected in the parenchyma in leaves and roots, demonstrating cell wall protection by pectic substances and lipids at the base of the trichome. The defense mechanisms that the species uses to confer tolerance are not yet known and the present results may help provide an anatomical basis to corroborate other sources of evidence and biomarkers that this species can use for phytoremediation processes.