Phytoremediation of Lead and Chromium Contaminated Soil Improves with the Endogenous Phenolics and Proline Production in Parthenium, Cannabis, Euphorbia, and Rumex Species

Abstract

Phytoremediation is the most promising and emerging technology for remediation of metal-contaminated sites. The aim of the current research was to investigate the metals accumulation potential of four weed species i.e., Parthenium, Cannabis, Euphorbia, and Rumex species. The endogenous free proline, total phenolic, carotenoids, and chlorophyll contents were assessed under metals stress and correlated with metals accumulation in plants. Plants of each species were allowed to grow in reference (uncontaminated) soil and other group on industrial effluent-contaminated soil under natural environment. Phytoextraction potentials of these plants were evaluated for removal of lead (Pb) and chromium (Cr). The heavy metal concentration in plant parts was analyzed by atomic absorption spectrophotometer. Varied accumulation of metals was found among different weed species. Moreover, metal accumulation was different within plant tissues i.e., roots, leaves, and stem. Cannabis and Parthenium showed bio-concentration BCF > 1 for Pb, reflecting their high metal accumulation potential and both plants were found superior than Rumex and Euphorbia for Cr accumulation. The endogenous free proline and phenolic contents showed significantly positive correlation with Pb accumulation in four plants i.e., Parthenium (R2 = 0.977, R2 = 0.9996), Cannabis (R2 = 0.9924, R2 = 0.9999), Euporbia (R2 = 0.9992, R2 = 0.9832), Rumex (R2 = 0.6033, R2 = 0.8272) respectively. Similarly, Cr accumulation in plants showed significantly positive correlation with proline and phenolic but the BCF ˂ 1.The chlorophyll and carotenoids contents in all plants negatively correlated with Pb and Cr concentration.