Leguminous plants nodulated by selected strains of Cupriavidus necator grow in heavy metal contaminated soils amended with calcium silicate

Abstract

Increasing concern regarding mining area environmental contamination with heavy metals has resulted in an emphasis of current research on phytoremediation. The aim of the present study was to assess the efficiency of symbiotic Cupriavidus necator strains on different leguminous plants in soil contaminated with heavy metals following the application of inorganic materials. The application of limestone and calcium silicate induced a significant increase in soil pH, with reductions in zinc and cadmium availability of 99 and 94 %, respectively. In addition, improved nodulation of Mimosa caesalpiniaefolia, Leucaena leucocephala and Mimosa pudica in soil with different levels of contamination was observed. Significant increases in the nitrogen content of the aerial parts of the plant were observed upon nodulation of the root system of Leucaena leucocephala and Mimosa pudica by strain UFLA01-659 (36 and 40 g kg−1) and by strain UFLA02-71 in Mimosa caesalpiniaefolia (39 g kg−1). The alleviating effect of calcium silicate resulted in higher production of dry matter from the aerial part of the plant, an increase in nodule number and an increase in the nitrogen fixation rate. The results of the present study demonstrate that the combination of rhizobia, leguminous plants and calcium silicate may represent a key factor in the remediation of areas contaminated by heavy metals.