Evaluation of Free Radical Scavenging Activities Against Multiple Heavy Metals Stress inAvicennia marina(Forsk.) andRhizophora mucronata Lamk

The tolerance mechanism of mangrove species (Avicennia marina(Forsk.) andRhizophora mucronata Lamk) was studied by inducing multiple heavy metal stress in roots and leaves of the plants. Mangrove seedlings were treated with different concentrations of heavy metal solution (Cr, Cd, Pb and Hg) for a period of 2 months. Scavenging antioxidant enzymes like Polyphenol Oxidase (PPO), Glutathione-S-transferase (GSTs) and Guaiacol Peroxidase (POD) were analyzed in both species afterappropriate intervals of 15 days. Results revealed that activities of these antioxidative enzymes were altereddue tomultiple heavy metals exposure in both mangrove species, whereas leaves exhibited the higher valuesas compared to the roots. In the leaves of both mangrove plants GSTs exhibited an increased trend throughout the investigated period whereas, PPO activity initially showed an increasing trend, but gradually decreased with the passage of time in response to heavy metal stress. Furthermore, an increased level of antioxidants was also observed in A. marina thanR. mucronatawhich proves that the former is a strong candidate for heavy metals phyto-remediation with its viable survival strategie