Morpho-physiological Tolerance Mechanisms of Talinum patens to Lead

Abstract

The objective of this study was to evaluate lead phytotoxicity on Talinum patens and the morpho-physiological tolerance mechanisms. The following parameters were considered: germination percentage, germination speed index, root and shoot length, fresh and dry matter, lead content in tissues, enzymatic antioxidant system, proline content, lipid peroxidation, root anatomy, cytogenetic analysis, and chlorophyll fluorescence. The experimental design was completely randomized, with five concentrations: 0, 50, 100, 250, and 500 μM Pb(NO3)2 and five replicates. Exposure to Pb(NO3)2 solutions did not influence germination, shoot length, or fresh and dry matter. However, a Pb(NO3)2-dependent concentration effect was observed, which reduced cell division in the root meristematic zone (mitotic index), reducing their length. Superoxide dismutase, catalase, and ascorbate peroxidase showed increased activity when exposed to lead, and the same effect was detected for proline content and lipid peroxidation. There was an increase in the dissipation of excess energy in photosystems, as well as an increase in epidermal thickness. Therefore, Talinum patens plants had morpho-physiological characteristics that favor their germination, development, and metal tolerance.