Seed Cd Concentration Research Articles

Effect of Zero-Valent Iron Application on Cadmium Uptake in Rice Plants Grown in Cadmium-Contaminated Soils

ABSTRACT Cadmium (Cd) contamination in soils is a serious problem for crop production in the world. Zero-valent iron [Fe (0)] is a reactive material with reducing power capable of stabilizing toxic elements in a solution. In the present study, we examined the effect of zero-valent iron [Fe (0)] application on Cd accumulation in rice plants growing in Cd-contaminated paddy soils. The application of 1.0 and 0.5 mg Fe (0) per 100 g soils significantly reduced the Cd concentration in seeds and leaves by less than 10% and 20% of those without Fe (0) application, respectively. The form of Cd in soil was determined by sequential extraction. The Fe (0) application increased the free-oxides-occluded (less available) Cd content, and decreased the exchangeable and iron-manganese-oxides-bound (more available) Cd content, in Cd-contaminated soils. Thus, this study clearly showed that the application of Fe (0) is a promising approach for remediation of Cd-contaminated paddy soils.

Role of roots in differences in seed cadmium concentration among soybean cultivars—proof by grafting experiment

Soybean cultivars show significant differences in cadmium (Cd) concentrations in seeds, due primarily to genetics, not environmental factors. We previously suggested that low-Cd cultivars accumulate Cd in their roots and thus prevent its translocation to the rest of the plant. Through grafting experiments, we drew the following conclusions about Cd absorption and translocation: (1) The amount of Cd accumulated in shoots is determined by the Cd accumulation capacity of roots: cultivars with a small capacity to accumulate Cd in roots translocate more Cd and accumulate it in shoots; (2) The Cd concentration in shoots is determined by the Cd accumulation capacity of roots and the shoot productive ability of the scion cultivar; (3) The Cd tolerance of shoots differs among cultivars. Enrei, with a high-Cd accumulation capacity of roots, had a low Cd tolerance of shoots compared with Suzuyutaka and Hatayutaka, with a low Cd accumulation capacity of roots; (4) Cultivars differ in their distribution of Cd to seed; (5) These results show that seed Cd concentration is influenced by the differences among cultivars in ease of translocation of Cd to seed and in Cd accumulation capacity of roots.

Remediation of cadmium-contaminated paddy soils by washing with chemicals: Effect of soil washing on cadmium uptake by soybean

We conducted a pot experiment to evaluate the effect of soil washing with CaCl(2) on Cd absorption by two soybean cultivars. The results were as follows: (1) Soybean growth was not significantly different in washed and unwashed soils, but the seed Cd concentration for both cultivars decreased significantly, up to 25%, in the washed soils compared with the unwashed soils. (2) In the washed soils, the Cd concentration in the soil solution indicated an obviously lower value from sowing to the flowering stage; however, the change in Cd speciation was not evident in the CaCl(2)-washed soil solution. Consequently, the effect of soil washing using CaCl(2) on Cd-contaminated paddy soils can be expected to continue after a CaCl(2)-washed paddy field is converted to an upland field.

For a successful pea production on polluted soils, inoculation with beneficial microbes requires active interaction between the microbial components and the plant

We conducted a pot experiment to study the effect of inoculation with Glomus intraradices isolate BEG141, Rhizobium leguminosarum bv. viciae strain G and Pseudomonas brassicacearum strain Am3 on three genotypes of Pisum sativum L. (VIR3429, VIR4488, VIR8456) grown in the presence of cadmium (Cd) elevated (5.4 mg Cd kg−1) and unpolluted (4.8 µg Cd kg−1) soils. Shoot and seed biomass and phosphorus (P) accumulation in seeds were lower in plants grown in the Cd polluted soil, and Cd uptake was higher than in plants grown in the non-polluted soil. There were differences between pea genotypes with respect to their uptake of Cd. Glomus intraradices inoculation increased mycorrhizal colonization of roots only in the polluted soil. Inoculation with R. leguminosarum or P. brassicacearum had no effect on plant growth or mycorrhizal colonization. A positive mycorrhizal effect existed on shoot and seed biomass in genotype VIR3429 grown in the polluted soil and on shoot biomass in genotype VIR4788 grown in the non-polluted soil. The VIR8456 treatment did not induce any response to inoculation with the mycorrhizal fungus in the soils. Seed P concentration increased in the non-polluted soil after inoculation with R. leguminosarum and the mixture of three inocula. Glomus intraradices and P. brassicacearum increased Cd concentration and total Cd in seeds of plants grown in the polluted soil. The results illustrate that 1) the ability of G. intraradices to improve pea growth in Cd polluted soil significantly depends on plant genotype, and 2) optimization of inoculations with beneficial microbes requires active interaction between the microbial components and the plant under specific soil conditions.

Genotypic Differences in Cadmium Concentration and Distribution of Soybean and Rice

In order to investigate the genotypic differences in seed cadmium (Cd) concentration in soybean and rice, 17 soybean and 49 rice varieties were cultivated in Cd-polluted soils or water culture containing Cd. Significant differences in seed Cd concentration were found among soybean and rice varieties. A high level of inheritance of the seed Cd concentration was revealed for soybean. The physiological mechanism underlying the Cd translocation to shoots and seeds in soybean was involved in Cd retention in the roots. The commercial rice varieties (e.g., Koshihikari) were categorized into the low grain Cd group. On the other hand, several indica or indica-japonica rice varieties accumulated considerably high Cd concentrations in grains as well as straws, when they were cultivated under upland conditions, suggesting that these varieties would be most responsive to phytoremediation of Cd-polluted paddy fields. There was no correlation of the Cd concentration between younger shoots and mature seeds in the rice cultivars, so it may be impossible to use rice for evaluating the genotypic variation in seed Cd concentration using relatively younger shoots. On the other hand, a positive correlation between them was found in the soybean cultivars, so it may be possible to evaluate the genotypic variation in soybean seed Cd concentration using relatively younger soybean shoots. Interactions between Cd and other metals (Cu, Fe, Mn, and Zn) in terms of their uptake and translocation to shoots were found among the rice and soybean cultivars.

Genotypic Variation in Shoot Cadmium Concentration in Rice and Soybean in Soils with Different Levels of Cadmium Contamination

A pot experiment was conducted to investigate whether the shoot cadmium (Cd) concentration in 11 rice and 10 soybean cultivars varied among 4 soils with different levels of Cd contamination. Significant differences in shoot Cd concentration were found among rice or soybean cultivars grown in the 4 soils. The ranking of the rice cultivars for the shoot Cd concentration varied considerably among the soils. On the other hand, the soybean cultivars were ranked similarly in terms of shoot Cd concentration in the 4 soils. Significant and positive correlations were found between the Cd and Zn concentrations and between the Cd and Mn concentrations in the shoot of rice cultivars, when they were grown in 2 soils with relatively moderate levels of Cd contamination. The shoot Cd concentration in the soybean cultivars, however, was not correlated with the concentrations determined for any of the metals (Zn, Mn, Cu, and Fe) across the 4 soils. Significant and positive correlations between the concentrations of Cd in younger shoots and mature seeds were detected among the soybean cultivars in 2 soils used, unlike among the rice cultivars, indicating that it may be difficult to evaluate the genotypic variation in seed Cd concentration using relatively younger shoots in the case of rice. These results revealed that genotypic differences in shoot Cd concentration in rice or soybean are variable or invariable among soils, respectively.

Effects of Cadmium and Mixed Heavy Metals on Rice Growth in Liaoning, China

Joint effects of Cd and other heavy metals (Pb, Cu, Zn and As) on the growth and development of rice plants and the uptake of these heavy metals by rice were studied using the pot-culture method combined with chemical and statistical analyses. The results showed that the growth and development of rice plants were strongly influenced by the double-element combined pollution. There was an average decrease in the height of rice plants of 4.0–5.0 cm, and grain yield was decreased by 20.0–30.0%, compared with the control. The uptake of Cd by rice plants was promoted due to the interactions between Cd and the other heavy metals added to the soil. The Cd concentration in roots, stems/leaves and seeds increased 31.6–47.7, 16.7–61.5 and 19.6–78.6%, respectively. Due to interactions, uptake of Pb, Cu and Zn by roots and stems/leaves was inhibited, accumulation of Pb, Cu and Zn in seeds was increased, uptake of As by roots was promoted and uptake of As by stems/leaves was inhibited. In particular, the upward transporting ability of the heavy metals absorbed by rice plants was significantly increased.

Accumulation of cadmium and selected elements in flax seed grown on a calcareous soil

Seed of flax (Linum usitatissimum L.) grown on calcareous and neutral soils sometimes accumulates relatively high concentrations of Cd. The influence of a post-flowering application of NH4NO3 (115 mg N kg-1), CdSO4 (1 mg Cd kg-1), FeEDDHA (2 mg Fe kg-1), NaH2PO4 (120 mg P kg-1) and ZnSO4 (8 mg Zn kg-1) on seed accumulation of Cd, Fe, N, Mn, P and Zn by flax grown on a Calciaquoll was studied in two experiments under greenhouse conditions. Seed yields were increased by the N and Zn treatments, and the N×Zn interaction was positive. Zinc deficiency delayed flowering and boll formation by up to 20 days and reduced seed size. In the absence of added Cd, seed accumulated up to 0.33 mg Cd kg-1. This Cd accumulation was reduced by approximately 50 and 17% by added Zn and Fe, respectively, but was little affected by P fertilizer and post-flowering N stress. In the presence of added Cd, seed Cd exceeded 3.3 mg Cd kg-1, and the antagonistic effects of Fe and Zn on seed Cd were absent. Seed N, P, Fe and Zn concentrations were increased on average by 10, 45, 31 and 97% by the N, P, Fe and Zn fertilizer treatments, respectively. FeEDDHA reduced seed Mn concentration by approximately 58%. However, seed Mn concentration was much less than that found in vegetative tissue at flowering. Soil-applied Zn may reduce seed Cd concentration in flax under field conditions, and may increase marketability of flax for food use.