Mechanisms of Phytoremediatory Effect of Ocimum basilicum L. and its Rhizosphere Exposed to Different Concentrations of the Organochlorine Pesticide Endosulfan

Abstract

Endosulfan is a toxic organochlorine pesticide, environmentally persistent, banned and restricted in many countries. For phytoremediation purposes, we have previously observed that the presence of Ocimum basilicum decreased the concentration of endosulfan in experimentally-polluted soil by 37% after 30 days. To study the possible mechanism, we evaluated whether endosulfan could affect 1) the activity of glutathione S transferase (GST) of O. basilicum and 2) microorganisms from rhizosphere. Young plants were added to experimentally-polluted soil with endosulfan. Rhizosphere microorganisms were exposed to several concentrations of endosulfan and cultured in Luria Bertani (LB) broth or agar, their growth was determined by triplicate either spectrophotometrically or by plate count. After exposure to the pesticide endosulfan in O. basilicum and its rhizosphere, three effects were observed: 1) In LB broth, optimal growth of microorganisms was observed at 72 and 48 h after exposure to endosulfan 2.4 and 3.4 mg/10 mL. 2) Optimal growth of microorganisms in LB agar was observed at 0.3 and 2.4 mg/10 mL. 3) GST was increased after exposure to these pesticides over its control. These observations suggest that phytostimulaton and phytotransformation could be involved as possible mechanisms of the phytoremediatory effect of O. basilicum.