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Peanut (Arachis hypogaea L.) genotypes may differ greatly with regard to cadmium (Cd) accumulation, but the underlying mechanisms remain unclear. To determine the key factors that may contribute to Cd re-distribution and accumulation in peanut genotypes with different Cd accumulating patterns, a split-pot soil experiment was conducted with three common Chinese peanut cultivars (Fenghua-6, Huayu-20, and Huayu-23). The growth medium was separated into pod and root zones with varied Cd concentrations in each zone to determine the re-distribution of Cd after it is taken up via different routes. The peanut cultivars were divided into two groups based on Cd translocation efficiency as follows: (1) high internal Cd translocation efficiency cultivar (Fenghua-6) and (2) low internal Cd translocation efficiency cultivars (Huayu-20 and Huayu-23). Compared with Fenghua-6, low Cd translocation cultivars Huayu-20 and Huayu-23 showed higher biomass production, especially in stems and leaves, leading to dilution of metal concentrations. Results also showed that Cd concentration in roots increased significantly with increasing Cd concentrations in soils when Cd was applied in the root zone. However, there were no significant differences in the root Cd concentrations between different pod zone Cd treatments and the control, suggesting that root uptake, rather than pod uptake, is responsible for Cd accumulation in the roots of peanuts. Significant differences of Cd distribution were observed between pod and root zone Cd exposure treatments. The three peanut cultivars revealed higher kernel over total Cd fractions for pod than for root zone Cd exposure if only extra applied Cd was considered. This suggests that uptake through peg and pod shell might, at least partially, be responsible for the variation in Cd re-distribution and accumulation among peanut cultivars. Cd uptake by plants via two routes (i.e., via roots and via pegs and pods, respectively) and internal Cd translocation appear to be important mechanisms in determining Cd accumulation in the kernels of peanuts.

Generally, soil heavy metal contamination consists of a mixture of heavy metals. Soil chemical properties and interaction with other pollutants in soil affect the external heavy metal bioavailability. Moreover, interaction with other pollutants accumulated in organisms may change the toxicity of each pollutant. Therefore, the hypotheses was tested that addition of Cd or Pb to Cu-contaminated soil would lead to an increase in tissue Cu accumulation in the earthworm, Dendrobaena veneta, caused by (i) induction of metallothionein by Cd, or (ii) an increase in Cu concentration in soil solution due to the exchange of adsorbed Cu for Pb. Tissue heavy metal concentrations were determined after exposure in contaminated soils for 3 or 21 days. Considerable amounts of Cu, Cd, and Pb were accumulated, indicating that these heavy metals were available for uptake by D. veneta. Both Cd and Pb, however, did not significantly affect tissue Cu accumulation.

Soil salinity and plant genotype may affect bioavailability of Cd and Zn to wheat. The aim of this study was to investigate the relationship between concentrations of Zn and Cd in saline soil solutions and in different wheat genotypes. A greenhouse experiment with four bread wheat genotypes (Triticum aestivum L. cv. Rushan, Kavir, Cross, and Falat), and a durum wheat (Triticum durum L. cv. Durum), at four salinity levels of irrigation water (0, 60, 120, and 180 mM NaCI) in triplicate was conducted. After 45 d of growth, the shoots were harvested, and Zn and Cd concentrations were determined in the shoots. Speciation of Cd and Zn in saturation paste extract was modeled using MINTEQA2. A significant (P < 0.05) correlation was observed between model results and Cd and Zn species measured using Amberlite resin. Cadmium and Zn speciation in MINTEQA2-calculated soil solution was affected by salinity but not by wheat genotype. The major Cd species present in MINTEQA2-calculated soil solution were free Cd2+, CdCl+, and CdSO40, that increased with increasing salinity. Free Zn2+ was the dominant Zn-species for all salinities and decreased with increasing salinity. Increasing salinity resulted in significant increases and decreases in shoot Cd and Zn concentrations, respectively, of the Zn-inefficient genotypes. Cadmium concentrations in shoots of Durum and Kavir genotypes were best predicted by CdCl+ concentrations in solution. In contrast, free Zn2+ ion concentrations in MINTEQA2 calculated soil solution were best related to shoot Zn concentrations in Zn-efficient genotypes. Under saline conditions, Zn and Cd speciation effects on bioavailability thus depend on both plant genotype and the metal of interest. [ABSTRACT FROM AUTHOR]

Salinity and Zn deficiency in soils are two factors that may change the phytoavailability of Zn and Cd. The aim of this study was to determine the effects of salinity and Zn application on soil Cd and Zn solubility and their concentration in wheat shoots. A greenhouse experiment with wheat (Triticum aestivum L. cv. Rushan) consisting of two levels of Zn (0 and 15 mg Zn kg-1, in the form of ZnSO4), and five salinity levels of irrigation water (0, 60, 120, and 180 mM NaCl, and 120 mM NaNO3) in triplicate was conducted. Wheat was seeded in pots. After 45 d of growth, the shoots were harvested, and Zn and Cd concentrations were determined. After harvesting, electrical conductivity (EC), pH, and concentrations of anions and cations were determined in soil saturation extracts. Concentrations of Cd and Zn species in soil solution were predicted using the speciation program MINTEQA2. Increasing salinity increased total Cd (CDT), Cd2+, CdCl+, CdHCO3+, and CdCl20 concentrations in the soil solution, whereas no such effect was found for the NaNO3 treatment. Higher salinity decreased the total Zn (ZnT) and free Zn2+ concentrations in the soil solution and decreased Zn concentrations in the wheat shoots. With application of Zn fertilizer, shoot Cd concentrations decreased by 11 to 90%, whereas Zn concentration increased by 75 to 103%. Increasing salinity of irrigation water decreased shoot dry matter, especially if no ZnSO4 was applied. Application of Zn had a positive effect on salt tolerance of plant and increased dry matter of shoot. [ABSTRACT FROM AUTHOR]