A Comparative survey of bioaccumulation of some mettallic ions such as CU(II), Cr(VI)O₄²⁻ by the aquatic fern - Azolla Pinnata

Abstract

Plants of Azolla pinnata were treated with six different concentrations of Cu(II) and Cr(VI)O₄²⁻ (0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 mg dm⁻³) for 48, 72, 168 hours under laboratory conditions. Accumulation of Cu(II) and Cr(V)O₄²⁻ by Azolla pinata was studied. cud accumulation was greater than that of Cr for Azolia plants. The plants showed ability to reduce 5.0 mg dm⁻³ Cu background concentration to below 0.03 mg dm⁻³ within 168 hours. The Cr(VI)O₄²⁻ concentration of 5.0 mg dm⁻³ was reduced to below 0.14 mg dm⁻³ in 168 hours. Cysteine synthesis was greater under Cu than Cr stress condition. The Chlorophyll content in plants decreased non-significantly with an increase in Cu(II) and Cr(VI)O₄²⁻ concentrations and duration of exposure. The results suggest that an increase in cysteine by Cu(II) and Cr(V1)O₄²⁻ treatment at the initial exposure period are part of the overall expression of Cu(I) and Cr(VI)O₄²⁻ tolerance in the plant, and the decrease in Chlorophyll content is a consequence of Cu(II) and Cr(V1)O₄²⁻ toxicity at higher metal concentrations and increased period of exposure.