Santha Devi

Role of humic acid entrapped calcium alginate beads in removal of heavy metals.

Most of the available techniques for removal of heavy metals from solution such as leachates from waste sites are very expensive. The technique described in this paper is designed to study the removal of humic acid by alginate beads and the subsequent binding of the metals within the beads thus decreasing the leachability of heavy metals from a hazardous waste site. The entry of 500 mg/l humic acid into 3% calcium alginate beads in 24 h showed a distinct fluorescence as compared to the fluorescence shown by the entry of 100 and 250 mg/l of humic acid into alginate beads. Further, on treatment of calcium alginate beads containing 500 mg/l humic acid with metals such as Cu, Mn, Zn, Cr and Fe, quenching of fluorescence was noticed, which was maximum with Cu and minimum with Fe.

Biochemical studies on the toxicity of linear alkylbenzene sulphonate to Scenedesmus quadricauda in culture

Abstract The biochemical mechanisms involved in the response of the fresh water alga Scenedesmus quadricauda in experimental culture to linear alkylbenzene sulphonate (LAS), the active component of synthetic detergents, and a major water pollutants are studied. At 0.02% LAS (w/v) a growth promoting and at 0.1% a toxic effect was manifested. Transmission electron microscopy showed altered functional organization, especially in chloroplasts. Impairment in photosynthesis as studied by 14 CO 2 assimilation and oxygen evolution on illumination was also evident at the toxic level. Incorporation of 14 C-glycine from the medium to chlorophylls, as tested after thin layer chromatography and Sephadex LH 20 gel filtration, suggested chlorophyll synthesis to be a target of toxicity. Alkaline fructose-diphosphatase activity was also adversely affected. Dark respiration and heterotrophic fixation of 14 CO 2 were also inhibited by higher levels of LAS. The algae were found to elicit uptake of LAS from the medium, partly degrading it and using it for growth, and partly accumulating it leading to toxicity. The biochemical basis of phycotoxicity is explained and its significance to ecotoxicology of water pollutants discussed.

Effect of linear alkylbenzene sulfonate on Scenedesmus quardicauda in culture

Abstract Synthetic detergents are among the most prevalent of water pollutants leading to ecological disturbances. Therefore, their potential ecotoxicological impact was studied using a laboratory model system. The effect of different concentrations of linear alkylbenzene sulfonate (LAS), a major component of synthetic detergent, on experimental cultures of the fresh water alga Scenedesmus quardicauda has been studied. The threshold level for LAS was found to be 0.05%, above that level marked toxicity was evident and growth and survival of exposed cultures were adversely affected. There was also a decrease in nutrient uptake and in protein and DNA syntheses. Pathomorphological alterations were also evident from scanning electron microscopic observations. The significance of the above data in relation to aquatic toxicity and ecotoxicological impact of synthetic detergents is discussed.

Chronic toxicity of cadmium in Pteris vittata, a roadside fern.

The effect of Cd at concentrations of 0.1, 1.0, 2.5, 5.0 and 10.0 ppm on Pteris vittata, a commonly occurring roadside fern was studied during the entire life cycle from spore germination to spore production. Light, fluorescence, scanning and transmission electron microscopy were used to study the structural changes due to Cd. With increasing Cd concentrations the following changes were observed: inhibition of first and second generation spores, abnormal development of protonema, disintegration of thylakoid organization, delayed formation of reproductive elements and abnormal sporangia. As the Cd content of the plants increased with increasing concentration in the medium, biomass-specific concentrations of chlorophyll and carotenoids decreased. The gametophytic phase was more sensitive than the sporophytic stage to Cd. The differences noticed during the three stages of development could be useful as markers for Cd contamination in the environment.

Toxicity of linear alkyl benzene sulphonate on some aquatic plants

The effect of different concentrations of linear alkyl benzene sulphonate under laboratory conditions on Salvinia molesta Mitchell, Hydrilla verticillata (L.f.) Royle, Ceratophyllum demursum L., Lemna minor L., Spirodella polyrhiza (L.) Schleid, and Pistia stratiotes L. was studied. A dose dependent effect on protein and chlorophyll a and b contents leading to substantial changes were noticed in the ultrastructural features as evident from scanning electron microscopy.

Ultrastructural and biochemical effects of cadmium on the aquatic fern Marsilea minuta Linn

The uptake of cadmium by cultured vegetative clones of the aquatic fern Marsilea minuta was studied in a static experimental bioassay system as functions of dose and period of exposure. The pathomorphological manifestations of Cd toxicity, as studied by transmission electron microscope, indicated damage to chloroplasts and tonoplasts as well as electron opaque granular deposits. Preliminary evidence based on molecular sieving chromatography showed the formation of two cadmium-binding proteins of 78 and 33 kDa in the leaf tissue under cadmium stress.

Pteridophyte Aerospora of India

Abstract Spores belonging to 43 taxa of pteridophytes were observed from the ambient air of 11 localities in India. It is suggested that pteridophyte spores could be listed among viable particulate air pollutants, especially in the light of the earlier reports regarding their allergenicity.

Changes in uptake of calcium caused by phytotoxicity of cadmium in Salvinia molesta

The effect of Ca on the uptake of Cd by root and leaves of Salvinia molesta was investigated at different time intervals and under different photoperiods. For detailed study on uptake and interaction, 15Ca and 109Cd were used and it was found that there was a higher uptake of 45Ca in the root and leaves at 48 h and a concurrent reduction in 109Cd content at 48 h suggesting alterations in Ca functions due to the phytotoxicity of Cd. Ultrastructural changes due to cadmium toxicity included swirling of thylakoid membranes of the chloroplasts as well as detachment of the tips of trichomes from the leaf.

Development of Fern Sporangia: a Fluorescence Microscopy Study

The utility of fluorescence microscopy for studying development of fern spores is investigated. Changes in the fluorescence characteristics during the developmental stages of fern sporangia can be attributed to the changes in the chemical composition of the cell wall. Bright blue autofluorescence of the spores indicated the presence of sporopollenin. The sporangial walls and the spores autofluoresced yellow under blue light excitation. Fluorescence microscopy is a useful addition to light, scanning, and transmission electron microscopy because living specimens can be studied owing to their fluorescence properties.

Effects of long-term low-dose exposure to cadmium during the entire life cycle of Ceratopteris thalictroides, a water fern

The effects of chronic low-dose exposure of the aquatic fern Ceratopteris thalictroides in culture to cadmium during different stages of the entire life cycle (gametophyte, juvenile sporophyte, mature sporophytes and spores) were studied. Dose-dependent toxicity manifestations, including ultrastructural pathomorphological changes were detected in all stages, with gametophytes being the most sensitive. Cumulative systemic effects were indicated by the impaired germination of spores from plants life-long exposed to 0.1 mg/L Cd, which did not affect spore germination in the first generation. Morphological studies also showed that even at 0.1 mg/L Cd, long-term exposure caused adverse effects on growth and differentiation. The differential sensitivity of various stages of the same plant, to the same level of toxicant indicated that data for safety evaluation of entire life cycle are needed while fixing ecologically safe environmental limits.