Monalisa Mohanty
Widespread use of chromium in several industrial and mining activities leads to the release of toxic hexavalent chromium (Cr6+) to environment. Screening and identification of hyperaccumulators for possible phytoremediation of Cr6+ from these contaminated sites has gained utmost importance in recent years. A pot culture experiment was conducted to observe the possible phytotoxic effects of Cr6+ in an agroforestry species, i.e. Sesbania sesban L., commonly known as sesban. Cr6+ showed significant growth retardation in 21 days old sesban seedlings, which includes 80% inhibition in seed germination at 10,000 ppm, 59.6% germination index. At 300 ppm, 67% of seedling survival was noted after 7 days of seedling exposure. A significant variation in root and shoot length of seedlings supplemented with different concentrations of Cr6+ was noticed. Shoot phytotoxicity was amplified from 6% to 31% with elevated supply of Cr6+ from 10 ppm to 300 ppm. An increased supply of chromium showed gradual decrease in chlorophyll content of seedlings. Root and leaf catalase activities were considerably increased in sesban seedlings treated with 10 ppm of Cr6+, which gradually declined with the increasing supply. Root and leaf peroxidase activities were significantly increased with increasing concentration of Cr6+. Chromium bioaccumulation was more in roots than leaves and stems. Roots showed nearly more than 10 times higher chromium bioaccumulation than stems. The results of the present study reveal the phytoremediation mechanisms developed by sesban seedlings to combat Cr6+ induced various physiological stresses under field condition.
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