Cd In Nutrient Solution Research Articles

Profiling of main metabolites in root exudates and mucilage collected from maize submitted to cadmium stress.

The aim of this study was to characterize qualitatively and quantitatively the composition of the main rhizodeposits emitted from maize (Zea mays) under Cd stress, in order to discuss their role in Cd availability and tolerance. Maize was grown for 6weeks in sand at four Cd exposure levels (0, 10, 20, and 40μM Cd in nutrient solution) and two types of rhizodeposits were collected at the end of cultivation period. Mucilage and other molecules adhering to rhizospheric sand were extracted with a buffer before root exudates were collected by diffusion into water. Total carbon, proteins, amino acids, and sugars were analyzed for both rhizodeposit types and about 40 molecules were identified using GC-MS and LC-MS. Cadmium effect on plant morphology and functioning was slight, but consistent with previous works on Cd toxicity. However, rhizodeposition did tend to be impacted, with a decrease in total carbon, sugars, and amino acids correlating with an increasing Cd content. Such a decrease was not noticeable for proteins in root exudates. These observations were confirmed by the same trends in individual compound contents, although the results were generally not statistically significant. Many of the molecules determined are well-known to modify, whether directly or indirectly, Cd speciation and dynamics in the soil and could play a role in Cd tolerance.

Responses of Carbonic Anhydrase to Cadmium in the Zinc/Cadmium Hyperaccumulator Picris divaricata Vant.

A number of higher plants are able to hyperaccumulate cadmium (Cd). However, it is unknown whether cadmium (Cd) plays a biological functional role in the carbonic anhydrase (CA) of hyperaccumulators. A hydroponic experiment was conducted to explore the potentially physiological function of Cd in CA and the accumulation and tolerance of Cd in the Zn/Cd hyperaccumulator Picris divaricata Vant. P. divaricata was exposed to nutrient solutions with six Cd concentrations (0, 5, 10, 25, 50 and 75 μmol L−1). After 12 d, plants were harvested for the analysis of plant biomass, Cd concentration and CA activity. The Cd concentrations in plant increased with the increasing Cd in nutrient solution, reaching 640 and 3 100 mg kg−1 in shoot and root, respectively, at the 75 μmol L−1 Cd treatment. Meanwhile, plant growth was enhanced by the Cd treatments at 5–25 L−1, but it was significantly inhibited when the plants were exposed to solutions with higher Cd concerntrations (50 and 75 μmol L−1). Exposure to Cd significantly increased the CA activity in P. divaricata, which reached a maximum value of 21.27 U mg−1 proteins at the 25 μmol L−1 Cd treatment, and the CA activity and shoot Cd concentration were positively correlated at solutions Cd of ≤ 25 μmol L−1. Moreover, two protein bands appeared on the denatured gel electrophoresis of purified CA, indicating that P. divaricata may have CA isomers with their respective molecular weights at around 60 and 55 kDa, at least one of which is Cd-bound. In addition, trace amounts of Cd in purified CA significantly increased with the supplied Cd concentration in nutrient solution (5–25 μmol L−1). The results suggested that Cd may play a biological role by enhancing the activities and forming the active Cd-specific CA in the hyperaccumulator P. divaricata.

Cd induced redistribution of elements within leaves of the Cd/Zn hyperaccumulator Thlaspi praecox as revealed by micro-PIXE

A detailed localisation of elements within leaf tissues of hydroponically grown Cd/Zn hyperaccumulator Thlaspi praecox (Brassicaceae) was determined by micro-PIXE at Jozef Stefan Institute (Ljubljana, Slove- nia) in order to study accumulation patterns of Cd and other elements in the case of a single metal (Cd) pollution. Plants were treated with increasing concentrations of Cd in the solution (0 (control), 1, 10 and 100 lM). As expected, concentration of Cd in the leaves gradually increased with Cd concentration in the solution. In order to reveal the main Cd storage compartment space within the leaves a relative element distribution (pool) was calculated based on concentrations of elements in specific leaf tissues and their weight portions. Where present at detectable levels, Cd accumulated in the epidermal tissues (at 10 lM), but the contribution of epidermal pool decreased with increasing Cd concentration in solu- tion (at 100 lM). The opposite was observed for the mesophyll pool. In addition, in Cd treated plants, a significant decrease in mesophyll Fe pool and an increase in the epidermal Fe pool were observed. Sim- ilar effect was seen for Mn pool at 100 lM Cd treatment accompanied by increasing Zn epidermal pool with increasing Cd in nutrient solution. Altogether these results indicate repartitioning of essential mesophyll cation pools (e.g., Fe, Mn and possibly Zn) when increasing Cd contents, that are instead more intensively stored in the epidermal cells. These results confirmed micro-PIXE as effective and powerful technique providing essential information on metal localisation, repartitioning and major ele- mental stores in plants on the tissue levels that were not accessible using classical analytical tech- niques and thus complementing our current understanding of plant metal tolerance mechanisms as a whole.

Does copper reduce cadmium uptake by different rice genotypes?

A hydroponics experiment was conducted to investigate the effect of copper (Cu) on cadmium (Cd), calcium (Ca), iron (Fe), and zinc (Zn) uptake by several rice genotypes. The experiment was carried out as a 2x2x4 factorial with four rice genotypes and two levels of Cu and Cd in nutrient solution. Plants were grown in a growth chamber with controlled environment. The results showed a significant difference between the biomass of different rice genotypes (P < 0.001). The Cd and Cu concentration in the solution had no significant effect on the biomass. The addition of Cu significantly decreased Cd uptake by shoots and roots of rice (P < 0.001). The Cd concentration did not significantly influence Ca uptake by plants, whereas the Cu concentration did (P = 0.034). There was a significant influence of Cd on Fe uptake by shoots and roots (P < 0.001, P = 0.003, respectively). Zn uptake decreased significantly as the addition of Cd and Cu increased in shoots. We concluded that Cu had significant influence on Cd uptake. The possible mechanisms were discussed.

Cadmium Accumulation by Water Hyacinth and Salvinia Under Different Sulfur Concentrations

Cadmium (Cd) accumulation by water hyacinth and salvinia under different sulfur (S) concentrations was studied. Plants were exposed during six days to 0 and 5 μM of Cd in nutrient solution with 0, 400 and 800 μM of S, and then S and Cd contents in tops and roots were determined. Sulfur content was always higher in S-treated plants, independent of the presence of Cd. Cadmium content in Cd-treated plants increased with the addition of S to the nutrient solution in both species. Water hyacinth roots accumulate an average of 1.4 time more Cd than those of salvinia. The increase in S concentration from 400 to 800 μM, however, usually did not result in additional increase in S nor in Cd accumulation. The molar Cd/S ratio after Cd treatment reached average values of about 4.8 in roots and 2.6 in tops in comparison to their respective controls. Both species, therefore, were Cd accumulators and the accumulation was larger in the roots under presence of S. Since water hyacinth produced larger root mass and accumulated more Cd, it showed larger capacity to remove Cd from aquatic systems contaminated with this metal, especially if S is available.

Fitotoxidez de cádmio para Eucalyptus maculata e E. urophylla em solução nutritiva

Estudaram-se os efeitos de doses crescentes de Cd em solução nutritiva no crescimento e absorção mineral de mudas de Eucalyptus maculata e E. urophylla e respectivos sintomas de fitotoxidez em casa de vegetação. Mudas foram mantidas por cinco semanas em vasos contendo 2 L de solução nutritiva de Clark, adicionando-se 0, 45, 90, 135 e 180 miM de Cd fornecido como CdSO4. Após uma semana de exposição aos tratamentos, E. maculata exibiu pontuações avermelhadas nas nervuras, clorose internerval, necrose, murchamento das folhas e escurecimento das raízes. Além desses sintomas, E. urophylla apresentou morte das gemas apicais e acentuada queda de folhas. A dose crítica de Cd para reduzir em 10% a matéria seca da parte aérea foi baixa; 2,4 miM e 1,5 miM de Cd para E. maculata e E. urophylla, respectivamente. Os níveis críticos de toxidez na parte aérea foram de 14,5 mg kg-1 em E. maculata e 10,8 mg kg-1 de Cd em E. urophylla. Esses resultados indicaram que E. maculata é provavelmente menos sensível ao Cd do que E. urophylla. Foi também observado que o Cd reduziu a translocação de Cu em até 24 e 43% em E. maculata e E. urophylla, respectivamente. A translocação de Fe caiu de 36% em média, nas duas espécies no controle para apenas 12% com 180 miM Cd. A elevação nas doses de Cd reduziu os teores de Ca e Mg na parte aérea das espécies, atingindo-se teores de Mg abaixo da faixa considerada adequada em E. urophylla. Ficaram evidenciadas a fitotoxidez de Cd no Eucalyptus e a relação desta com a diminuição da translocação de Cu e Fe e com a diminuição dos teores foliares de Mg.

Effects of sulfate on cadmium uptake by Swiss chard : II. Effects due to sulfate addition to soil

Sulfate complexation of Cd in nutrient solution has been shown to have little impact on Cd uptake by plants. This study examined the effect of sulfate added to soil on Cd concentrations in soil solution and Cd uptake by Swiss chard (Beta vulgaris L. cv. Fordhook Giant). Swiss chard was grown in soil which was wetted with complete nutrient solution containing equivalent salt concentrations of NaNO3 or Na2SO4. Plant growth was reduced by increasing both NO3 and SO4 concentrations in soil solution, with growth reductions similar for both salts. The Cd concentration in soil solution increased P< 0.05) more consistently with increasing concentrations of SO4 compared to NO3 in soil solution. Solution speciation, calculated with GEOCHEM-PC, showed significant increases of Cd2+ activities with increasing salt rates. Shoot Cd content in 19-day-old Swiss chard plants was marginally but significantly P <0.05) increased with increasing SO4 concentration but no effect was observed with increasing NO3 concentration. These results are compared with earlier work on the marked effect of Cl- salinity on Cd availability in Swiss chard. Possible mechanisms explaining the smaller effect of SO4 compared to Cl on Cd availability are proposed.

Efficiency of h+‐atpase activity on cadmium uptake by four cultivars of lettuce

Abstract Cadmium (Cd) uptake by lettuce (Lactuca sativa L.) was studied in a hydroponic solution study at concentrations approaching the total concentration in contaminated soil solutions. Four cultivars of lettuce were tested (Divina, Reine de Mai, Melina, and J.44). Ten 12‐day old seedlings, pretreated in 0.5 μM CdCl2 solution, were labelled with carrier free 109CdCl2 (from 0.05 μM to 5 μM Cd in nutrient solution) in the presence and absence of metabolic inhibitors, DNP and DCCD. Cadmium taken up by the roots was determined after a 30 min desorption in unlabelled CdCl2 solution. In the absence of metabolic inhibitors and at 5 μM Cd, root absorbed from 2.5 to 8 mg Cd/g root dry weight. Exchangeable Cd measured after desorption represented less than 1% of the total Cd absorbed by the root. Cadmium absorption in presence of DNP showed that approximately 80% of the Cd enters the cell through an active process. This mechanism seems to be directly associated with H+‐ATPase as observed with DCCD inhibition. Va...