M. B. Ali

Chromium (VI) accumulation reduces chlorophyll biosynthesis, nitrate reductase activity and protein content in Nymphaea alba L.

Plants of Nymphaea alba L. grown at various levels of chromium (VI) ranging from 1 to 200 microM accumulated chromium in concentration and duration-dependent manner. At all Cr levels, chromium accumulation by various plant tissues followed the order roots > leaves > rhizomes. Approximately 93% of total chromium present in the medium was accumulated by plants at lowest conentration (1 microM) used in the experiment. Chromium-induced toxicity appears at 1 microM chromium resulting in the build-up of delta-aminolevulinic acid (ALA) and reduced activities of delta-aminolevulinic acid dehydratase (ALAD) and nitrate reductase (NR), total chlorophyll (Chl) and protein contents. Ch1a was more sensitive than Ch1b to chromium toxicity. It could be inferred that chromium toxicity is not located at the level of ALA synthesis, but, probably at the ALAD activity which was more severely affected during chlorophyll biosynthesis. Finally, impaired chlorophyll biosynthesis resulted in reduced total chlorophyll content.

Physico-chemical characteristics and pollution level of Lake Nainital (U.P., India): role of macrophytes and phytoplankton in biomonitoring and phytoremediation of toxic metal ions.

Lake Nainital is the sole source of drinking water for the local people and even to majority of tourists. In background of lake utility and its importance at national level, such study is essential which is focused on toxic metal pollution and current nutrient status of the lake and their magnification by algae and macrophytes. Study has shown that lake water is rich in nutrients which supports growth of many aquatic macrophytes and algal blooms. Besides, water is contaminated with metals like Cr, Cu, Fe, Mn, Ni, Pb and Zn. Concentration of some of them like Fe, Pb and Ni were higher than the recommended maximum permissible limits. Concentration of these metals were also found high in lake sediments. The level of metals amongst various components of lake varied considerably in different season. Plants and algae growing therein accumulated appreciable amount of metals and water roots of Salix being more efficient than others. High metal removing potential of these plants may be significant for biomonitoring studies and could be a useful phytoremediation technology to restore water quality by harvesting submerged and floating biomass inhabiting littoral zone of the lake.

Bioaccumulation of toxic metals (Cr, Cd, Pb and Cu) by seeds of Euryale ferox Salisb. (Makhana) ☆

The level of toxic metals Cr, Cd, Pb and Cu was determined in seeds, water and sediments collected from nine closed waterbodies of Darbhanga, north Bihar, used for cultivation of the edible aquatic macrophyte Euryaleferox Salisb. during harvesting season of the crop for two successive years (1996 and 1997). Seeds bioconcentrated appreciable amount of these toxic metals in the order Pb > Cr > Cu > Cd. The increased load of metal pollution due to domestic and municipal discharges threatened the habitats of the plant. The toxic metal contents in seeds were found positively correlated with the ambient concentration of metals in water and sediments. The importance of these findings has been discussed for national water resource economy of the country and human health perspectives.