Toxicity and accumulation of selenium by plant species from the Chihuahuan Desert
Selenium (Se) is a trace element essential for animals and humans but at high concentrations becomes toxic for most living organisms. Some areas of the United States, such as the San Joaquin Valley in California, present high Se concentrations in sediments and water, which have affected birds and waterfowl. Different techniques are used for the remediation of hazardous contaminated soils. However, most of these techniques are expensive, labor consuming, and in general, spread the contaminants to larger areas. As an alternative, phytoremediation (the use of plants to remove contaminants) is a promising technology that can potentially be applied for the restoration of polluted environments. In this research, agar and hydroponics experiments were performed in order to study different plants from the El Paso-Juarez region to determine their ability to accumulate and tolerate Se. Plants studied included L. tridentata, A. fruticosa, and C. arvensis, L. In addition, Environmental Scanning Electron Microscopy (ESEM) and Transmission Electron Microscopy (TEM) studies provided information about microscopic morphological effects of Se in plant tissues. Furthermore, X-ray absorption spectroscopy experiments were performed in order to gain information on the mechanism of selenium incorporation as well as selenium-sulfur interaction in C. arvensis L. plants. Results from these studies demonstrated that L. tridentata plants grown in hydroponics containing 5 mg Se L−1 accumulated 872, 1193, and 1264 mg Se kg−1 DW in roots, stems, and leaves, respectively. These amounts are comparable to those presented by Se accumulator plant species. In addition, A. fruticosa plants grown in agar containing 5 mg Se L−1 (from Na2SeO3) accumulated 1177, 412, and 394 mg Se kg−1 DW in roots, stems, and leaves, respectively. According to these results, A. fruticosa might be considered as a secondary Se accumulator. TEM studies indicated that in A. fruticosa, root cell vacuolization could be the mechanism by which this plant species avoids Se toxicity in other parts of the plant. ESEM analysis in A. fruticosa showed that leaves in plants treated with Se had an increase in the amount of stomata compared to the control. It was hypothesized that A. fruticosa has an increase in stomata to enhance Se volatilization and avoid the toxic effects of Se. Experiments performed with C. arvensis L. indicated, when grown in 5 mg Se L−1 in agar media, this plant was able to accumulate 453, 144, and 136 mg Se kg−1 DW in roots, stems, and leaves, respectively. (Abstract shortened by UMI.)^
Biology, Botany|Chemistry, Analytical|Environmental Sciences|Engineering, Environmental|Biology, Plant Physiology
Cruz-Jimenez, Gustavo, "Toxicity and accumulation of selenium by plant species from the Chihuahuan Desert" (2004). ETD Collection for University of Texas, El Paso. AAI3151881.