Biomedical subjects

D. E. Salt

Publications and source records attributed to D. E. Salt.

4 recordsLinked to original sources

PubMed1998

PHYTOREMEDIATION.

Contaminated soils and waters pose a major environmental and human health problem, which may be partially solved by the emerging phytoremediation technology. This cost-effective plant-based approach to remediation takes advantage of the remarkable ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues. Toxic heavy metals and organic pollutants are the major targets for phytoremediation. In recent years, knowledge of the physiological and molecular mechanisms of phytoremediation began to emerge together with biological and engineering strategies designed to optimize and improve phytoremediation. In addition, several field trials confirmed the feasibility of using plants for environmental cleanup. This review concentrates on the most developed subsets of phytoremediation technology and on the biological mechanisms that make phytoremediation work.

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PubMed1997

The Role of Metal Transport and Tolerance in Nickel Hyperaccumulation by Thlaspi goesingense Halacsy.

Metal hyperaccumulators are plants that are capable of extracting metals from the soil and accumulating them to extraordinary concentrations in aboveground tissues (greater than 0.1% dry biomass Ni or Co or greater than 1% dry biomass Zn or Mn). Approximately 400 hyperaccumulator species have been identified, according to the analysis of field-collected specimens. Metal hyperaccumulators are interesting model organisms to study for the development of a phytoremediation technology, the use of plants to remove pollutant metals from soils. However, little is known about the molecular, biochemical, and physiological processes that result in the hyperaccumulator phenotype. We investigated the role of Ni tolerance and transport in Ni hyperaccumulation by Thlaspi goesingense, using plant biomass production, evapotranspiration, and protoplast viability assays, and by following short- and long-term uptake of Ni into roots and shoots. As long as both species (T. goesingense and Thlaspi arvense) were unaffected by Ni toxicity, the rates of Ni translocation from roots to shoots were the same in both the hyper- and nonaccumulator species. Our data suggest that Ni tolerance is sufficient to explain the Ni hyperaccumulator phenotype observed in hydroponically cultured T. goesingense when compared with the Ni-sensitive nonhyperaccumulator T. arvense.

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PubMed1995

MgATP-Dependent Transport of Phytochelatins Across the Tonoplast of Oat Roots.

In Cd-exposed oat (Avena sativa) roots Cd was found to be associated primarily with the phytochelatin ([gamma]-glutamylcysteinyl)3-glutamic acid [([gamma]EC)3G], with a peptide to Cd ratio of 1:3 (cysteine to Cd ratio of 1:1), even though both ([gamma]EC)2G and ([gamma]EC)3G were present in the roots. Phytochelatins are known to accumulate in the vacuoles of plant cells on exposure to Cd, but the mechanism is not clear. Here we present evidence for the transport of the phytochelatins ([gamma]EC)3G and ([gamma]EC)2G as well as the Cd complex Cd-([gamma]EC)3G across the tonoplast of oat roots. Transport of ([gamma]EC)3G had a Km, for MgATP of 0.18 mM and a Vmax of 0.7 to 1 nmol mg-1 protein min-1. Transport of ([gamma]EC)3G was also energized by MgGTP and to a lesser extent MgUTP and was highly sensitive to orthovanadate, with a 50%-inhibitory concentration of 0.9 [mu]M. The Cd complex Cd-([gamma]EC)3G and ([gamma]EC)2G were also transported in a MgATP-dependent, vanadate-sensitive manner. Therefore, this process is a candidate for the transport of both phytochelatins, and Cd as its peptide complex, from the cytoplasm into the vacuole.

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PubMed1995

Mechanisms of Cadmium Mobility and Accumulation in Indian Mustard.

Indian mustard (Brassica juncea L.), a high biomass crop plant, accumulated substantial amounts of cadmium, with bioaccumulation coefficients (concentration of Cd in dry plant tissue/concentration in solution) of up to 1100 in shoots and 6700 in roots at nonphytotoxic concentrations of Cd (0.1 [mu]g/mL) in solution. This was associated with a rapid accumulation of phytochelatins in the root, where the majority of the Cd was coordinated with sulfur ligands, probably as a Cd-S4 complex, as demonstrated by x-ray absorption spectroscopy. In contrast, Cd moving in the xylem sap was coordinated predominantly with oxygen or nitrogen ligands. Cd concentrations in the xylem sap and the rate of Cd accumulation in the leaves displayed similar saturation kinetics, suggesting that the process of Cd transport from solution through the root and into the xylem is mediated by a saturable transport system(s). However, Cd translocation to the shoot appeared to be driven by transpiration, since ABA dramatically reduced Cd accumulation in leaves. Within leaves, Cd was preferentially accumulated in trichomes on the leaf surface, and this may be a possible detoxification mechanism.

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