ASSESSMENT OF LEAD ACCUMULATION POTENTIAL AND ITS PHYTOTOXIC EFFECTS IN EICHHORNIA CRASSIPESShiv Pratap, Kiran Gupta and Kum Kum Mishra
To assess the toxicity of Pb various parameters e.g. morphological, physiological, biochemical and genotoxicity were studied in situ as well as under laboratory condition,.. Plants of E. crassipes were exposed to nutrient solution containing 0.01, 0.1, 2.5, 5.0 and 10.0 ppm of lead for 24, 48,72 and 96 h. Leaf and root samples from treated culture were taken and analysed for bioconcentration of Pb. Accumulation of Pb was more in roots (791 jig g-' dw) in comparison to leaves (328.3 lag g-1 dw). The accumulation in root and leaf tissue was found to be both concentration and duration dependent. Phytotoxicity of Pb showed that chlorophyll a, b and total chlorophyll were stimulated from 0.01 to 0.1 ppm and inhibited at concentration ranging from 1.0 ppm to 10.0 ppm with the duration of exposure. Carotenoid content was induced from 0.01 to 2.5 ppm and decreased from 5.0 to 10.0 ppm. At lower concentration protein content and NR activity was induced, however, higher concentration had significant inhibitory effect on these two parameters. Root meristems were studied for mitotic index, which was induced from 0.01 to 0.1 ppm and decreased from 1.0 ppm to 10.0 ppm. It is concluded that lead inhibits cell division. Numerous micronuclei were also observed. The result indicated that water hyacinth is a good sensor to monitor low level of aquatic lead. Results showed high tolerance and accumulation potential of Pb by E. crassipes. The plant is found to be tolerant to the elevated lead concentration up to 0.1 ppm as there is no inhibition of chlorophyll and carotenoids. So this bioassay can be used for biomonitoring and control of heavy metal pollution in the aquatic environment
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