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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plants that have evolved to survive on metal-rich soils—metallophytes—have key values that must drive research of their unique properties and ultimately their conservation. The ability of metallophytes to tolerate extreme metal concentrations commends them for revegetation of mines and metal-contaminated sites. Metallophytes can also be exploited in environmental technologies, for example, phytostabilization, phytoremediation, and phytomining. Actions towards conserving metallophyte species are imperative, as metallophytes are increasingly under threat of extinction from mining activity. Although many hundreds of papers describe both the biology and applications of metallophytes, few have investigated the urgent need to conserve these unique species. This paper identifies the current state of metallophyte research, and advocates future research needs for the conservation of metallophyte biodiversity and the sustainable uses of metallophyte species in restoration, rehabilitation, contaminated site remediation, and other nascent phytotechnologies. Six fundamental questions are addressed: (1) Is enough known about the global status of metallophytes to ensure their conservation? (2) Are metallophytes threatened by the activities of the minerals industry, and can their potential for the restoration or rehabilitation of mined and disturbed land be realized? (3) What problems exist in gaining prior informed consent to access metallophyte genetic resources and how can the benefits arising from their uses be equitably shared? (4) What potential do metallophytes offer as a resource base for phytotechnologies? (5) Can genetic modification be used to “design” metallophytes to use in the remediation of contaminated land? (6) Does the prospect of using metallophytes in site remediation and restoration raise ethical issues?
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    European journal of soil science 55 (2004), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A long-term incubation experiment was established to assess the solid ⇅ solution equilibria of (Cu2+), (Pb2+) and (Ni2+) in soil pore water. The experiment comprised 23 soils spiked with 135, 300 and 75 mg kg−1 of Cu, Pb and Ni, respectively, added as nitrate salts in solution. Samples of soil pore water were extracted several times during the incubation period of 818 days and concentrations of Cu, Pb, Ni, dissolved organic carbon and major cations and anions were measured. Similar measurements were carried out on a smaller selection of historically contaminated soils to extend the range of data and assess compatibility of the measurements with the incubated soils. The chemical speciation program ‘WHAM VI’ was used to speciate metal ions in solution. A pH-dependent Freundlich equation was used to describe free ion activities, p(M2+), for Cu, Pb and Ni using total adsorbed metal, soil pH, soil organic carbon content and ionic strength as determining variables. For all three metals the greatest improvements in model fit were found when metal ions were assumed to be adsorbed exclusively on soil organic carbon rather than on the ‘whole soil’. Further improvements in the description of p(Cu2+) and p(Ni2+) were found when the ionic strength of the soil pore water was included within the model formulation. Residual standard deviations (–log10(M2+) units) for the best-fit models were 0.36, 0.53 and 0.29 for p(Cu2+), p(Pb2+) and p(Ni2+), respectively. The effects of progressive fixation of Pb, Cu and Ni on model parameterization, during the course of the experiment, were found to be small. Independent datasets from both published and unpublished sources were used to compare experimental protocols and validate the model for the determination of (M2+) in soil pore water.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth and zinc uptake of the hyperaccumulator species Thlaspi caerulescens J. & C. Presl and the non-hyperaccumulator species Thlaspi ochroleucum Boiss. & Heldr. were compared in solution culture experiments. T. caerulescens was able to tolerate 500 mmol m−3 (32.5 g m−3) Zn in solution without growth reduction, and up to 1000 mmol m−3 (65 g m−3) Zn without showing visible toxic symptoms but with a 25% decrease in dry matter (DM) yield. Up to 28 g kg−1 of Zn in shoot DM was obtained in healthy plants of T. caerulescens. In contrast, T. ochroleucum suffered severe phytotoxicity at 500 mmol m−3 Zn. Marked differences were shown in Zn uptake, distribution and redistribution between the two species. T. caerulescens had much higher concentrations of Zn in the shoots, whereas T. ochroleucum accumulated higher concentrations of Zn in the roots. When an external supply of 500 mmol m−3 Zn was withheld, 89% of the Zn accumulated previously in the roots of T. caerulescens was transported to the shoots over a 33 d period, whereas in T. ochroleucum only 32% was transported. T. caerulescens was shown to have a greater internal requirement for Zn than other plants. Increasing the supply of Zn from 1 to 10 mmol m−3 gave a 19% increase in the total DM of this species. liven the shoots from the 1 mmol m−3 Zn treatment which showed Zn deficiency contained 10 times greater Zn concentrations than the widely reported critical value for Zn deficiency to occur in many other plant species. The results obtained suggest that strongly expressed constitutive sequestration mechanisms exist in the hyperaccumulator T. caerulescens, which detoxify the large amount of Zn present in shoot tissues and decrease its physiological availability in the cytosol. Both T. caerulescens and T. ochroleucum had constitutively high concentrations of malate in shoots, which were little affected by different Zn treatments. Although malate may play a role in Zn chelation because of the high concentrations present, it cannot explain the species specificity of Zn tolerance and hyperaccumulation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 21 (1998), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relationship between Zn and P in the Zn hyperaccumulator Thlaspi caerulescens J. & C. Presl was investigated using hydroponic culture. Total concentrations of Zn in the shoots increased from 0·2 to 27 g kg–1 dry mass when solution Zn increased from 1 to 1000 mmol m–3. Water-soluble Zn accounted for 〉 80% of the total Zn in the shoots containing 〉 5 g Zn kg–1 dry mass. Total P was maintained at about 3 g kg–1 dry mass in the shoots containing 〈 20 g Zn kg–1 dry mass, but significantly decreased with higher Zn concentrations. Linear regression between insoluble P and insoluble Zn in the shoots produced a small slope, suggesting that co-precipitation of Zn and P was not an important detoxification mechanism in the shoots. In contrast, there was a strong correlation between insoluble P and insoluble Zn in the roots, with a linear slope of 0·3 — close to the P:Zn ratio in Zn3(PO4)2. Foliar sprays of phosphate did not affect shoot dry mass significantly, but decreased root length and root dry mass significantly at Zn concentrations in solution from 10 to 3000 mmol m–3. Foliar P was translocated to roots to enhance co-precipitation of Zn and P, although this did not enhance Zn tolerance. The results suggest that T.caerulescens possesses mechanisms which allow it to accumulate and sequester huge amounts of Zn in the shoots without causing P deficiency.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Wheat plants were grown hydroponically and fed with two sulphate sources differing in stable isotope composition, one having a δ34S of 13·7‰ and the other 4·1‰. Plant sulphur (S) isotope ratios were determined using an on-line continuous flow-isotope ratio mass spectrometer. This method greatly simplified the procedure for the measurement of S isotope ratios, and was found to be precise for samples containing 〉 1 mg S g–1 dry weight. The δ34S values of plant shoots, which had been grown on a single sulphate source, were very close to the source values, suggesting little isotope fractionation during sulphate uptake and transport from roots to shoots. By changing the sulphate sources at different growth stages, it was possible to estimate S accumulation and redistribution within different plant parts. At maturity, wheat grain derived 14, 30, 6 and 50% of its S from the accumulation during the following successive growth stages: between emergence and early stem extension, between stem extension and flag leaf emergence, between flag leaf emergence and anthesis, and after anthesis, respectively. It was estimated that 39, 32 and 52% of the S present in the flag leaves, older leaves and stems, respectively, at anthesis, was exported during the postanthesis period. These results demonstrate considerable cycling of S within wheat plants, and highlight the importance of S uptake after anthesis to the accumulation of S in grain under the experimental conditions employed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Although Arabidopsis halleri (=Cardaminopsis halleri) is known as a Zn hyperaccumulator, there have been no detailed studies on Zn accumulation, tolerance and cellular distribution in this species. In a hydroponic experiment, A. halleri grew healthily with Zn concentrations varying from 1 to 1000 μM, without showing phytotoxicity or reduction in root or shoot dry weights. The concentration of Zn in the shoots increased from 300 μg g−1 dry weight in the 1 μM Zn treatment to 32 000 μg g−1 in the 1000 μM Zn treatment. Approximately 60% of the total Zn in the shoots were water-soluble, and there was no evidence of Zn and P co-precipitation. Both citric and malic acid concentrations in the shoots were not significantly affected by the Zn treatments, whereas in the roots there was a positive response in both organic acids to increasing Zn in solution. Cellular distribution of Zn, Ca and K in frozen hydrated leaf tissues was examined using energy-dispersive X-ray microanalysis. Zinc was sequestered in the base of trichomes, whereas the middle and upper parts of trichomes were highly enriched with Ca. Mesophyll cells appeared to have more Zn than the epidermis, probably because the latter were very small in size. Similarities and differences between A. halleri and the other well-known Zn hyperaccumulator, Thlaspi caerulescens, are discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 212 (1999), S. 207-217 
    ISSN: 1573-5036
    Keywords: legume ; nitrogen ; N2-fixation ; pea ; sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A S-deficient soil was used in pot experiments to investigate the effects of S addition on growth and N2-fixation in pea (Pisum sativum L.). Addition of 100 mg S pot−1 increased seed yield by more than 2-fold. Numbers of pods formed were the most sensitive yield component affected by S deficiency. Sulphur addition also increased the concentration of N in leaves and stems, and the total content of N in the shoots. The amounts of N fixed by pea were determined at four growth stages from stem elongation to maturity, using the 15N dilution technique. Sulphur addition doubled the amount of N fixed at all growth stages. In contrast, leaf chlorophyll content and shoot dry weight were increased significantly by S addition only after the flowering and pod fill stage, respectively. Pea roots were found to have high concentrations of S, reaching approximately 10 mg g−1 dry weight and being 2.6–4.4 times the S concentration in the shoots under S-sufficient conditions. These results suggest that roots/nodules of pea have a high demand for S, and that N2-fixation is very sensitive to S deficiency. The effects of S deficiency on pea growth were likely to be caused by the shortage of N, due to decreased N2-fixation.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5036
    Keywords: diagnosis ; glutathione ; N:S ratio ; sulphur ; sulphate ; wheat variety
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sulphur deficiency has become increasingly widespread in wheat in the U.K. Growth, nutrient content and biochemical responses to S and N supply of a breadmaking wheat variety (Hereward) and a non-breadmaking variety (Riband) were investigated in a pot experiment. Shoot dry matter (DM) at stem extension (Zadok's GS 37) and at maturity was increased markedly by S. Grain production of the Riband variety was more susceptible to the imbalance of N to S than the Hereward variety. At GS 37, the concentrations of total S and sulphate-S of shoots, chlorophyll meter readings and the concentrations of glutathione of the uppermost fully expanded leaves were increased significantly by increasing S supply, whereas the concentrations of nitrate and amides were decreased by S. The greatest relative changes in response to S supply were those of the glutathione and asparagine concentrations. Riband also showed greater response to S than Hereward. Critical values of various diagnostic indices at GS 37 were derived from the relationships between DM yield and different indices. The two varieties showed similar diagnostic curves except that for the ratio of total N to total S (N:S) in shoots. Either total S or sulphate-S can be used alone as a good indicator of deficiency, and with values of 1500 and 190 mg kg-1 DM in shoots for the two indices respectively. There was also a well defined relationship between DM yield and the glutathione concentration, with a critical value of 240 nmol g-1 FW. There were no advantages of using % of total S as sulphate-S. Shoot N:S ratio was found to be less accurate in predicting S deficiency than total S or sulphate-S. For prognostic purposes, a much higher S status at GS 37 was required to ensure no losses of DM yield due to S deficiency at maturity.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-5036
    Keywords: glucosinolate content ; N application ; oilseed rape ; S application ; S uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sulphur (S) uptake and distribution in double low (Cobra) and single low (Bienvenu) winter oilseed rape were studied in field experiments at Cockle Park, Northumberland, at a site where the S supply was adequate. Total S uptake at maturity of between 80–100 kg ha-1 was similar in both varieties. Applications of S at a rate of 100 kg ha-1 increased S uptake by 10–15 kg ha-1. while applications of nitrogen (N) at a rate of 300 kg ha-1 increased S uptake by 29–34 kg ha-1. Sulphur distribution in the vegetative tissues varied little between the two varieties but the distribution within the pods differed significantly between the two varieties. In Bienvenu 65.8% of pod S was located in the seeds, while in Cobra 57.4 and 68.8% in the 1988–89 and 1989–90 seasons, respectively, was retained in the pod walls. The high S content of the seeds of Bienvenu was due to their high glucosinolate content, whereas the high content of S in the pod walls of Cobra was associated with the presence of free SO4 2-, which accounted for 70.6 to 89.4% of total S in the pod walls. The percentages of total plant S present in the pods were significantly increased by N applications and slightly decreased by S applications.
    Type of Medium: Electronic Resource
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