Abstract

Iron is an essential element, and its deficiency and excess result in negative effects on the growth and physiology of plants. Heavy metals are the highest anthropic pollutants that affect mangrove ecosystem. This study aimed to analyze the development of Rhizophora mangle seedlings in response to excess Fe under controlled conditions. Seedlings of R. mangle previously established were transferred to the culture substrate containing 45 (Control), 135, 225, 270, and 315 µmol L-1 of Fe. The propagules were cultivated for 270 days and during this period the epicotyl length and leaf production were evaluated. At the end of the experiment, the epicotyl length, growth rate, and gas exchange of the seedlings were calculated in the different treatments and the quantification of Fe in the aerial part and root of the seedlings were performed. The excess of Fe led to lower incorporation of biomass, mainly affecting leaf production in the treatment with 315 µmol L-1. A reduction was observed in the assimilation of carbon, also a reduction in stomatal conductance in the highest concentrations of the metal. The excess of Fe in the cultivation solution increased its concentration in the seedlings biomass, with the roots being principally responsible for the bioaccumulation. Although R. mangle plants showed clear signs of stress to excess Fe, they also have a strong capacity for bioaccumulation and tolerance.

Key words: Trace metal, mangrove, toxicity, bioaccumulation.