Transfer of radiocesium from rhizosphere soil to four cruciferous vegetables in association with a Bacillus pumilus strain and root exudation.

This study was carried out to assess the effect of Bacillus pumilus on the roots of four cruciferous vegetables with different root structures in regard to enhancement of 137Cs bioavailability in contaminated rhizosphere soil. Results revealed that B. pumilus inoculation did not enhance the plant biomass of vegetables, although it increased root volume and root surface areas of all vegetables except turnip. The pH changes due to rhizosphere acidification by B. pumilus inoculation and root exudation did not affect the bioavailability of 137Cs. However, concentrations of 137Cs in plant tissues and soil-to-plant transfer values increased as a result of the larger root volume and root surface area of vegetables due to inoculation. Moreover, leafy vegetables, which possessed larger root volume and root surface areas, had a higher 137Cs transfer value than root vegetables.

Growth and (137)Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan.

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.

Transfer of radiocesium to four cruciferous vegetables as influenced by organic amendment under different field conditions in Fukushima Prefecture.

Soil-to-plant transfer of radiocesium ((137)Cs) in four cruciferous vegetables as influenced by cattle manure-based compost amendment was investigated. Komatsuna, mustard, radish and turnip were cultivated in three different (137)Cs-contaminated fields at Nihonmatsu City in Fukushima Prefecture from June to August 2012. Results revealed that organic compost amendments stimulated plant biomass production and tended to induce higher (137)Cs concentration in the cruciferous vegetables in most cases. Among the studied sites, Takanishi soil possessing low exchangeable potassium (0.10 cmolc kg(-1)) was associated with an increased concentration of (137)Cs in plants. Radiocesium transfer factor (TF) values of the vegetables ranged from 0.025 to 0.119. The increase in (137)Cs TFs was dependent on larger plant biomass production, high organic matter content, and high sand content in the studied soils. Average (137)Cs TF values for all study sites and compost treatments were higher in Komatsuna (0.072) and radish (0.059), which exhibited a higher biomass production compared to mustard and turnip. The transferability of (137)Cs to vegetables from soils was in the order Komatsuna > radish > mustard > turnip. The highest (137)Cs TF value (0.071) of all vegetables was recorded for a field where the soil had high organic matter content and a high clay proportion of 470 g kg(-1) consisting of Al-vermiculite clay mineral.