Adsorption of Cadmium by Brassica juncea (L.) Czern. and Brassica pekinensis (Lour.) Rupr in Pot Experiment

Heavy metal pollution in farmland threatens human life. It is not clear whether crops can adsorb heavy metals. In this study, the cadmium accumulation and tolerance in Chinese cabbage Brassica pekinensis (cv. Xiaoza-56) and the known Cd-accumulator Brassica juncea in hydroponics and pot experiment were investigated. Furthermore, we evaluated their potential on the phytoextraction of Cd-contaminated soil. The hydroponics with 1–50 μM Cd concentrations showed that both B. juncea and B. pekinensis had high Cd accumulation and tolerance with translocation factor closed to 1 at Cd levels < 25 μM. The pot study conducted with 5 to 100 mg Cd kg−1 soil indicated that B. juncea showed less tolerance and accumulation to Cd than B. pekinensis, especially at higher Cd levels. The bioconcentration factor was much higher than 1 in both B. juncea and B. pekinensis grown in <40 mg Cd kg−1 soil without showing biomass reduction. In the model evaluation, the ability of B. juncea and B. pekinensis to reduce the initial soil Cd concentration of 20 and 5 mg kg−1 to specific targets with a lower or higher biomass of 4 or 20 t ha−1, respectively. The above results indicate that B. juncea and B. pekinensis (cv. Xiaoza-56), which the latter is a better candidate for Cd phytoextraction in moderated Cd-contaminated soil. The results provide a reference for Cd pollution control.

Accumulation of cadmium and zinc in barley regenerants on a provocative soil background with cadmium

Background. An effective way to obtain barley (Hordeum vulgare L.) genotypes stress-tolerant to cadmium, with a low level of toxic ion accumulation in grain, is the selection of cells in selective in vitro systems, based on somaclonal variability, which promotes the formation of specific and nonspecific adaptive mechanisms.Materials and methods. The object of the study was cv. ‘999-93’, developed by selection from a hybrid combination of spring barley (Luly × Conrad) × 2867-80, and its regenerated forms in seed reproductions of the 3–5th generation, induced in the process of cell selection on media with cadmium, aluminum and polyethylene glycol. The plants were grown under normal soil conditions and against a provocative background for cadmium.Results. The contribution of the environment-forming activity in the roots of the studied genotypes to inactivation of toxic ions appeared insignificant. The total removal of cadmium by plants against a provocative background increased 22.5 times, reaching 5.8–10.3 mg/kg of dry phytomass when distributed among organs: roots (91.9–93.4%) > stems (5.9–7.8%) > grain (0.5–0.8%). The amount of toxic metal in grain increased 11 times in the original form and 2.8–6.8 times in regenerants. The negative effect of excess cadmium in the soil on the accumulation of zinc in barley was shown. There was no gradation in the importance of organs for zinc accumulation or any presence of functional barriers preventing this. Regenerants induced on selective media with cadmium had the greatest adaptive advantages to stress: pronounced barrier functions of roots, minimal accumulation of toxic ions in aerial organs, and high seed productivity (they exceeded the original genotype by 35.5%). Adaptive reactions associated with the limitation of cadmium accumulation in plant tissues of regenerants, obtained by in vitro selections with aluminum and an osmotic, were shown to be weak.