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

Abstract

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 133Cs, individual 88Sr, and combined 88Sr + 133Cs, 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 88Sr + 133Cs were greater than for 133Cs and 88Sr while the concentration was the same in the soil (10, 20, 40, 80, and 160 mg kg−1). The highest 88Sr + 133Cs accumulation was 2128.5 µg g−1dw, and the highest accumulation values of 133Cs and 88Sr were 1738.4 µg g−1dw and 1818.2 µg g−1dw (in 160 mg kg−1), respectively. The lowest 88Sr + 133Cs, 133Cs, and 88Sr accumulation values were 416.37 µg g−1dw, 268.90 µg g−1dw, and 354.28 µg g−1dw (10 mg kg−1), respectively. MDA content was higher under 88Sr and 133Cs stress than under 88Sr + 133Cs 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 133Cs and 88Sr than 88Sr + 133Cs stress. The 88Sr, 133Cs, and 88Sr + 133Cs 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 88Sr, 133Cs, and 88Sr + 133Cs, 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 88Sr + 133Cs contamination.