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Zn Uptake (zn + uptake)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Biokinetics of cadmium and zinc in a marine bacterium: Influences of metal interaction and pre-exposure

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2008
Dongshi Chen
Abstract The uptake kinetics of Cd and Zn, as influenced by metal interaction and metal pre-exposure, was examined in the gram-positive marine bacterium Bacillus firmus over a wide range of ambient free-Cd and -Zn concentrations. Bacteria were exposed to experimental media with different concentrations of Cd and Zn over a short, 15-min period. Zinc was found to be an effective competitive inhibitor of Cd uptake when the Zn2+ concentration ([Zn2+]) was increased to 10,8 M, whereas the Cd concentration (ranging from 10,9 to 10,6 M) did not affect Zn uptake. Inhibition of Cd uptake was dependent on [Zn2+] instead of the [Zn2+] to Cd2+ concentration ratio. Cadmium uptake at different [Zn2+] was significantly inhibited by a sulfur ligand (SH) blocker (N -ethylmaleimide) and a Ca-channel blocker (lanthanum), suggesting that competition between Cd and Zn most likely occurred via binding to the same transport sites. Cadmium efflux also was determined in the presence of different [Zn2+]. A biphasic depuration of Cd was found when [Zn2+] was greater than 10,8 M, whereas the calculated Cd efflux rate was independent of [Zn2+]. We further exposed B. firmus at different Cd or Zn concentrations for 24 h, then determined the metal uptake and efflux kinetics as well as the metallothionein (MT) induction. Both the Cd and Zn cellular concentrations increased with greater exposed metal concentration, but the MT levels and efflux were little affected by the elevated metal concentration. To some extent, however, the Cd uptake was reduced with an elevated intracellular Zn concentration, suggesting that at high Cd concentrations, intracellular Zn can suppress the Cd uptake in B. firmus. These results help to understand the interactions of metals in the marine environments. [source]

Grain mineral concentrations and yield of wheat grown under organic and conventional management

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2004
MH Ryan
Abstract On the low-P soils in southeastern Australia, organic crops differ from conventional ones primarily in the use of relatively insoluble, as opposed to soluble, P fertilisers and in the non-use of herbicides. As organic management, particularly elimination of soluble fertilisers, is often claimed to enhance grain mineral concentrations, we examined grain from wheat on paired organic and conventional farms in two sets of experiments: (1) four pairs of commercial crops (1991,1993); and (2) fertiliser experiments on one farm pair where nil fertiliser was compared with 40 kg ha,1 of P as either relatively insoluble reactive phosphate rock or more soluble superphosphate (1991 and 1992). All wheat was grown following a 2,6 year legume-based pasture phase. Both conventional management and the superphosphate treatment greatly increased yields but reduced colonisation by mycorrhizal fungi. While only minor variations occurred in grain N, K, Mg, Ca, S and Fe concentrations, conventional grain had lower Zn and Cu but higher Mn and P than organic grain. These differences were ascribed to: soluble P fertilisers increasing P uptake but reducing mycorrhizal colonisation and thereby reducing Zn uptake and enhancing Mn uptake; dilution of Cu in heavier crops; and past lime applications on the organic farm decreasing Mn availability. These variations in grain minerals had nutritional implications primarily favouring the organic grain; however, organic management and, specifically, elimination of soluble fertilisers did not induce dramatic increases in grain mineral concentrations. In addition, organic management was coupled with yield reductions of 17,84 per cent due to P limitation and weeds. The impact of large regional variations in the characteristics of organic and conventional systems on the general applicability of the results from this study and other similar studies is discussed. Copyright © 2004 Society of Chemical Industry [source]

Transport interactions between cadmium and zinc in roots of bread and durum wheat seedlings

PHYSIOLOGIA PLANTARUM, Issue 1 2002
Jonathan J. Hart
Field studies have shown that the addition of Zn to Cd-containing soils can help reduce accumulation of Cd in crop plants. To understand the mechanisms involved, this study used 109Cd and 65Zn to examine the transport interactions of Zn and Cd at the root cell plasma membrane of bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum). Results showed that Cd2+ uptake was inhibited by Zn2+ and Zn2+ uptake was inhibited by Cd2+. Concentration-dependent uptake of both Cd2+ and Zn2+ consisted of a combination of linear binding by cell walls and saturable, Michaelis-Menten influx across the plasma membrane. Saturable influx data from experiments with and without 10 µm concentrations of the corresponding inhibiting ion were converted to double reciprocal plots. The results revealed a competitive interaction between Cd2+ and Zn2+, confirming that Cd2+ and Zn2+ share a common transport system at the root cell plasma membrane in both bread and durum wheat. The study suggests that breeding or agronomic strategies that aim to decrease Cd uptake or increase Zn uptake must take into account the potential accompanying change in transport of the competing ion. [source]

Phytoremediation: The uptake of metals and metalloids by rhodes grass grown on metal-contaminated soil

REMEDIATION, Issue 2 2005
Scott M. Keeling
An experiment was performed to examine the phytoremediation potential of Rhodes grass (Chloris gayana Kunth cv. ,Pioneer'). The study sought to determine substrate tolerance, biomass production, and plant uptake of antimony (Sb), arsenic (As), cadmium (Cd), lead (Pb), silver (Ag), and zinc (Zn). The plants were grown on weight percent mixtures (5 percent, 15 percent, 25 percent, 35 percent, 50 percent) of a vertisol soil and base-metal mine tailings (7,2,040 ,g/g As, , 30 ,g/g Cd, 30,12,000 ,g/g Pb, and 72,4,120 ,g/g Zn). The 5 percent and 15 percent amendment of mine tailings increased the biomass production of Rhodes grass (from 0.1 g/plant to , 3.5 g/plant) without appreciably elevating plant concentrations of the elements. Plant growth decreased by greater than 50 percent for the substrate containing greater than 25 percent tailings (3,023 ,g/g Pb and 1,084 ,g/g Zn). Reduced biomass production coincided with maximal Zn uptake by Rhodes grass (249.8 ,g/g), indicating tailings induced phytotoxicity. The total concentrations of metals and metalloids tolerated by Rhodes grass in the plant-growth medium indicated hypertolerance to elevated As, Pb, and Zn concentrations. Partial extraction of the plant-growth medium determined that plant-available Pb was ten times higher than Ag, As, Cd, and Zn availability. However, Rhodes grass accumulated low levels of Pb, in addition to As and Cd, over the experimental range, indicating low fodder toxicity risk to browsing livestock. This study concludes that if there are no invasive species issues associated with conservation land uses, Rhodes grass is well suited to metalliferous mined land revegetation and would therefore be highly effective for such programs in subtropical and tropical Australia. © 2005 Wiley Periodicals, Inc. [source]