ABD EL-ALL, AZZA A. M. ,ELHAM M. AREF AND HANAN A. M. HASSANEIN( 2011). Bioaccumulation of heavy metals by the water fern azolla pinnataEgypt. J. Agric. Res., 89 (4), 2011 1261
Abstract: Azolla pinnata aquatic fronds were tested for their ability to bioaccumulate heavy metals from Yoshida medium supplemented with different heavy metals, i.e. Pb+2, Cd+2 and Cu+2 at different concentrations 0.0, 0.5, 1.0, 1.5 and 2.0 ppm, at different growth periods of 5, 10, 15, 20, 25 and 30 days. Results revealed that azolla can grow healthy with the accumulation of these metals. The highest fresh and dry weights of azolla were observed after 30 days at 2.0 ppm of Cu+2. These values were significantly higher than those for Pb+2 and Cd+2 at 1.0 and 0.5 ppm , respectively. Also, azolla fronds exerted higher nitrogenase activity when grown in culture medium without heavy metals, or supplemented with 1.5, 1.5 and 0.5 ppm of Pb+2, Cd+2 and Cu+2, respectively. The highest records of nitrogen uptake were obtained, in the presence of Cu+2 (2.0 ppm) treatment, while phosphorus uptake increased with increasing the concentrations of Pb+2 and Cu+2 from 0.5 ppm to 2.0 ppm. On the other hand, phosphorus uptake decreased with increasing the concentrations of Cd+2 from 0.5 to 2.0 ppm. Potassium uptake in response to different Cd+2 concentrations was lower than the other treatments including the control, from 5 to 30 days of growth periods. The greatest contents of Pb+2, Cd+2 and Cu+2 were observed in azolla fronds grown in presence of 2.0 ppm of any of these elements and collected after 30 days. Pb+2 uptakes were higher at the concentration of 2.0 ppm compared with other concentrations of Cd+2 and Cu+2. Thus, Azolla pinnata showed tolerance to the tested heavy metals at concentration up to 1mg/l that supposed to pollute the medium. Therefore, azolla can serve as a phytoremdiation agent in the heavy metal polluted habitats.
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