Vetiver grass is a potential candidate for phytoremediation of iron ore mine spoil dumps

Vetiver grass, Chrysopogon zizaniodes (L.) Roberty, is a perennial C4 grass, valued for its aromatic essential oil in the roots. Vetiver attracted global attention as a natural means for diverse environmental applications including detoxification of degraded soil and water. A pilot study was conducted to investigate its potential to rehabilitate iron ore spoil dumpsites generated from the Joda East Iron mine located in Odisha, India. Four diverse genotypes of vetiver: S2 (diploid variety), S4 (tetraploid derivative of S2), TH (originated from Thailand), BL (a broad leaf) were grown over a period of 12 months to observe their growth performance, metal tolerance and metal uptake. The shoot/root length, photosynthetic pigments - chlorophyll, carotenoid and biomass production of plants grown on iron mine soil decreased initially as compared to the control plants grown on garden soil. At the end of 12 month the plants showed evidence of normal growth and appeared healthy. Scanning electron microscopy (SEM) and Perl's Prussian blue stain confirmed the uptake and localization of Fe in the roots and shoots of the plants grown on mine soil. In addition Zn, Mn, Cr and Cu, was detected in the plant tissues. Such accumulation of metals in plant tissues led to oxidative damage induced by reactive oxygen species (ROS). As a consequence the activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPOD), glutathione reductase (GR) and glutathione peroxidase (GPX) were increased. Based on the results it can be inferred that vetiver grass per se can tolerate high concentrations of Fe along with other heavy metals in its tissues. Such potential vary across the four genotypes, and the genotype BL followed by S4 can be claimed of paramount importance in terms of phytoremediation. Thus vetiver grass can be effectively used for rehabilitation and soil stabilization of sites contaminated with high levels of heavy metals, particularly Fe, Mn, Zn and Cr.