The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity

Kwan, K.H.M.; Smith, Steven G.

doi:10.1016/0269-7491(88)90004-8

Cited by 20 publications

(12 citation statements)

References 17 publications

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“…The flow rate of the pump was adjusted to achieve: {a) dilution of the metal stock solution to the desired concentrations of 0-2/^M Tl or 1-5 /iM Cd; and (6) a total flow rate of 4 cm^ min"^ to result in two complete renewals of nutrients and metal every 24 h. It was found from a preliminary experiment that these flow rates were suflicient to maintain metal concentrations at the outlets of the flowthrough units within 85 % of the nominal concentrations throughout the experiments. In Lemna minor, Tl is over one order of magnitude more toxic than Cd (Kwan, 1988;Kwan & Smith, 1988) and, as a consequence, using the same exposure concentrations in long term uptake studies could prove misleading if one of the elements exerted a greater toxic stress than the other. It was therefore decided to set the exposure concentrations of Tl and Cd near to their respective ECg,, values.…”

Section: Accumulation and Depuration Of CD And Tl As A Function Of Timementioning

confidence: 99%

“…The concentration of stable Cd and TI in Lemna tissues and growth medium were determined by flame and electrothermal atomic absorption spectroscopy (Varian AA-1475 with G7A-95 Graphite Tube Atomizer) according to procedures described previously (Kwan, 1988;Kwan & Smith, 1988). Briefly, Lemna was digested in a minimal volume of analytical grade nitric acid, evaporated to dryness and made up to volume with 1 M HNO3.…”

Section: Radioassay and Determination Of CD And Timentioning

confidence: 99%

“…Stock cultures of Lemna minor were maintained under constant conditions as described by Kwan & Smith (1988) and Kwan (1988). Briefly, this involved growing the plant in half-strength Steinberg medium (Steinberg, 1946) adjusted to pH6-0±0-l and continuous illumination with an irradiance of minimum of four replicates were used.…”

Section: Culturesmentioning

confidence: 99%

“…It has been previously established that in Lemna minor, Tl is over one order of magnitude more toxic than Cd (Kwan & Smith, 1988;Kwan, 1988). The difference in toxicity may stem, at least in part, from; {a) the bioavailability of the elements to the plant, (b) the relative amounts of Cd and Tl accumulated by the plant, (c) their relative distribution between the cell wall bound fraction and that which accumulates within the plasma membrane and {d) the relative distribution of Cd and Tl within the cells of the plant and their chemical forms.…”

Section: Introductionmentioning

confidence: 99%

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Some aspects of the kinetics of cadmium and thallium uptake by fronds of Lemna minor L.

Kwan

Smith

1991

New Phytologist

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SUMMARYA Study of influx and accumulation of Tl and Cd by Lemna minor has revealed a number of contrasting features which arise from the basic physico-chemical properties of the two elements. Short-term influx of Cd over a range of concentration (0-1-10 //.M) followed a linear trend while that of Tl over the same range produced a profile with a plateau at the higher concentrations, indicating saturation of the absorption mechanisms. Application of Ca and K antagonists aiming to indicate the nature of the absorption mechanisms did not reveal any consistent trends. Long-term exposure of the plant to Cd and Tl produced steady-state concentrations after 250 and 140 h respectively, by which stage Lemna had accumulated nearly twice as much Cd than Tl. It appears that a significant amount of Cd is probably in the Donnan free-space and strongly bound to cell constituents from which the element is depurated slowly and continuously in Cd-free medium. It is concluded that Tl is tenaciously held in the plant tissues, perhaps in the cell vacuole, as 80 % of the steady-state concentration is retained by the plant even after 140 h in Tl-free medium. The influence of several external physical and chemical factors further emphasizes the contrasting nature of the two elements; Tl uptake is almost entirely an active process and ion activity of Tl is relatively unaffected by changes in pH and ligand concentration. Cd uptake involves both active and passive components, ion activity is markedly reduced at low H"^ ion concentrations and in the presence of ligands, such as EDTA. Inhibition of uptake was found for both elements in the presence of competing ions.

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Section: Accumulation and Depuration Of CD And Tl As A Function Of Timementioning

confidence: 99%

Section: Radioassay and Determination Of CD And Timentioning

confidence: 99%

Section: Culturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Some aspects of the kinetics of cadmium and thallium uptake by fronds of Lemna minor L.

Kwan

Smith

1991

New Phytologist

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“…Stock cultures of Lemna minor were maintained under constant conditions as described elsewhere (Kwan andSmith, 1988 andK wan, 1988). Briefly, this involved growing the plant in half strength Steinberg medium (Steinberg, 1946), adjusted to pH 6.0 ± 0.1 and under continuous illumination with an intensity of I ,400 lux.…”

Section: Methodsmentioning

confidence: 99%

Accumulated forms of thallium and cadmium inLemna minor. II. Relationship between duration of exposure and metal-protein binding

Kwan

Smith

1990

Chemical Speciation & Bioavailability

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Gel filtration chromatography (with Sephadex G25, G50 and G100) was used to separate the different forms of thallium (TI) and cadmium (Cd) in the cytosol fraction of Lemna minor and to examine the influence of the duration of metal exposure on the speciation of the two elements. A major proportion of Cd in the soluble phase was found to be bound to three groups of proteinaceous and polypeptide fractions; two of these, the high molecular weight protein fraction (Mr > 150,000) and the low polypeptide sized moieties of about Mr 1,SOO or less were constitutive entities, whereas the intermediate sized fraction (Mr 7,000-8,000) could only be detected in plants previously exposed to Cd. After 12 days of exposure to Cd this fraction accounted for the greatest part of the bound Cd in Lemna tissues. Extending the period of exposure from 18 hours to 12 days resulted in a shift in the distribution of Cd between the low and intermediate fractions. Evidence for Tl-protein binding was limited and confined to the high molecular weight fraction, and most of the Tl in the soluble phase was present in a form closely allied to the free ion. The contrasting behaviour between the two elements has been interpreted in terms of the differences in their physicochemical properties.

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Thallium

Filipov¹

2015

Hamilton &Amp; Hardy's Industrial Toxicology

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The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity

Cited by 20 publications

References 17 publications

Some aspects of the kinetics of cadmium and thallium uptake by fronds of Lemna minor L.

Some aspects of the kinetics of cadmium and thallium uptake by fronds of Lemna minor L.

Accumulated forms of thallium and cadmium inLemna minor. II. Relationship between duration of exposure and metal-protein binding

Thallium

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