Physiological Responses and Phytoremediation Abilities of Cucumber (Cucumis sativus L.) under Cesium and Strontium Contaminated Soils

Soils contaminated with radionuclides pose a long-term radiation hazard to human health through food chain exposure and other pathways. The uptake, accumulation, and distribution of Cs-133, individual Sr-88, and combined Sr-88 + Cs-133, with their physiological and biochemical responses in greenhouse-potted soil-based cucumber (Cucumis sativus L.), were studied. The results from the present study revealed that the uptake, accumulation, TF, and BCF ability of cucumber for Sr-88 + Cs-133 were greater than for Cs-133 and Sr-88 while the concentration was the same in the soil (10, 20, 40, 80, and 160 mg kg(-1)). The highest Sr-88 + Cs-133 accumulation was 2128.5 mu g g(-1)dw, and the highest accumulation values of Cs-133 and Sr-88 were 1738.4 mu g g(-1)dw and 1818.2 mu g g(-1)dw (in 160 mg kg(-1)), respectively. The lowest Sr-88 + Cs-133, Cs-133, and Sr-88 accumulation values were 416.37 mu g g(-1)dw, 268.90 mu g g(-1)dw, and 354.28 mu g g(-1)dw (10 mg kg(-1)), respectively. MDA content was higher under Sr-88 and Cs-133 stress than under Sr-88 + Cs-133 stress. Chlorophyll content increased at 10 and 20 mg kg(-1); however, it decreased with increasing concentrations (40, 80, and 160 mg kg(-1)). Proline content and the activities of CAT, POD, and SOD were lower under Cs-133 and Sr-88 than Sr-88 + Cs-133 stress. The Sr-88, Cs-133, and Sr-88 + Cs-133 treatment concentrations sequentially induced some enzymes over 60 days of exposure, suggesting that this complex of antioxidant enzymes-CAT, POD, and SOD-works in combination to reduce the impact of toxicity of Sr-88, Cs-133, and Sr-88 + Cs-133, especially in young leaves. It is concluded that cucumber reveals considerable phytoremediation capabilities due to unique growth potential in contaminated substrate and is suitable for the bioreclamation of degraded soils. The plant is especially applicable for efficient phytoextraction of Sr-88 + Cs-133 contamination.