The effects of ethylenediaminetetra-acetic acid (EDTA) on germination, length of stem, area of leaf, fresh weight, level of lipid per oxidation, alkaline phosphatase, acid phosphatase, super oxide dismutase (SOD) and catalase in the roots of cadmium (Cd) treated maize (Zea mays L) and cowpea (Vigna unguiculata L) seedlings after 7 and 21 days of germination were determined in this study. The results obtained, indicate that at the end of 7 and 21 days of exposure to Cd, percentage germination of the seeds were not significantly different in both control and test soil (p>0.05). Morphological parameters (area of leaf, length of stem and fresh weight) were significantly reduced by Cd after 7 and 21 days. The supplementation of the soil sample with EDTA (0.5 mM or 1.0 mM) reversed the effect of Cd on these parameters as it significantly increased length of stems, area of leaf and plant fresh weight. There was a significant decrease in root acid phosphatase, root alkaline phosphatase, super-oxide dismutase (SOD) and catalase activity in both plant species. Both used doses of EDTA to ameliorate the above biochemical parameters. Increased level of root lipid peroxidation in Cd treated maize and cowpea seedlings was observed after 7 and 21 days of germination. Albeit, the level of lipid peroxidation in the root of Cd treated maize was significantly higher than that of cowpea, an indication that cowpea may be more tolerant than maize to Cd toxicity. The treatment of plant with, concentrations of EDTA (0.5 and 1.0 mM) failed to decrease the Cd induced, but increased the level of root lipid peroxidation. These results indicate that EDTA (0.5 mM and 1.0 mM) could be used for the treatment of Cd toxicity in plants; although, EDTA did not totally protect cowpea seedling from oxidative stress.
Key words: Heavy metal, phytoremediation.
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