WP4 Metals in the Environment: Chemistry and Fate Issues
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HAM-1117-848648) Molecular Analyses of Cadmium Toxicity in Arabidopsis, Sorghum, and Tobacco.

Dunkerley, Ray¹, Hamissou, Mijitaba¹, ¹ Jacksonville State University, Jacksonville, Alabama, USA

ABSTRACT- Cadmium is a non essential heavy metal pollutant of the environment, resulting from agricultural practices, mining, and industrial activities. It is also released into the environment by automobile exhaust gases. Because of its high water solubility, Cd is readily available for uptake by plants and aquatic animals. In plants, Cd has been shown to interfere with the uptake, transport, and use of several essential elements causing complex nutrient deficiency symptoms. Cd appears to be absorbed passively and then translocated freely through the rest of the plant body. Several plant species are known to uptake and store Cd in their chloroplast, therefore affecting various aspects of photosynthesis. Like other heavy metals, the toxic actions of Cd are believed to be exerted on metabolic enzymes by altering their active sites. Cd toxicity in plants is also characterized by a rapid increase in reactive oxygen species (ROS) creating therefore conditions for secondary oxidative stress. The objectives of this research are to investigate the effects of Cd on the activities of ROS scavenger molecules, superoxide dismutase (SOD) and peroxidase (PO) enzymes and on the photosynthetic activities of isolated chloroplasts in arabidospsi thaliana, sorghum bicolor, Nicotiana tobacum challenged with elevated concentrations of Cd. Plants were grown in potted soil and Hoagland pH 6.9 and feed with various concentrations of CdCl2 for 14 days. Toxicity index chlorosis was recodered daily. Biomass accumulation, SOD, POD, and chloroplasts activities were determined at the conclusion of the experiments Preliminary data indicated that Cd causes more chlorosis to tobacco than arabidopsis or sorghum. Citrate dehydrogenase activities were higher in sorghum; PO activities were higher in tobacco; and photosynthetic activities declined as Cd concentrations were increased.

Key words: Cadmium toxixity, Oxidative stress, Toxicity, Arabidopsis, sorghum, tobacco