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| Effects of nano titanium dioxide on the toxicity of Chinese cabbage under cadmium stress |
| Received:December 25, 2019 |
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| KeyWord:TiO2 nanoparticles;Cd;Chinese cabbage;phytotoxicity;oxidative damage;antioxidant enzyme activity |
| Author Name | Affiliation | E-mail | | WANG Miao-miao | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | QIANG Li-wen | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | qianglw@126.com | | WANG Wei | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | ZHANG Ke-qiang | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | SUN Bin-bin | College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China | |
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| Abstract: |
| To investigate the effects of titanium dioxide nanoparticles(TiO2 NPs)on plant growth and physiology under cadmium(Cd) stress, Chinese cabbage(Brassica rapa var. glabra)was used as a research subject in hydroponic experiments. The biomass, malondialdehyde(MDA), chlorophyll, activities of antioxidant enzymes, ultrastructure, and contents of Cd and Ti in Chinese cabbage roots and shoots were determined. The results showed that with the increase of TiO2 NPs, the growth of Chinese cabbage seedlings was further inhibited under Cd stress, as the height and dry weight of plant decreased by 5.31% and 29.79%(P<0.05), respectively. After TiO2 NPs exposure, the Cd contents in the roots and shoots of the Chinese cabbages increased by 64.86% and 58.30%(P<0.05), respectively. TiO2 NPs exposure significantly enhanced the MDA content, activities of catalase(CAT), superoxide dismutase(SOD), and peroxidase(POD)in Chinese cabbage seedlings under Cd stress. Under a single stress degree of Cd, we found blurred and disorderly arranged chloroplast particles and lamellas. Under TiO2 NPs and Cd co-exposure, a large number of TiO2 NPs aggregated in the cytoplasm of Chinese cabbage root and leaf cells. We also observed that the ultrastructure of Chinese cabbage cells was significantly damaged under TiO2 NPs and Cd co-exposure, including folded and collapsed cell walls, irregular chloroplasts, dilated and disorganized grana thylakoids lamellae, and a significant reduction in chlorophyll content. Our results indicated that TiO2 NPs act as a carrier of Cd bioaccumulation, significantly promoting the absorption of Cd in the roots of Chinese cabbage and transporting them to the ground above. The accumulation of TiO2 NPs and Cd resulted in membrane lipid peroxidation and damages to the chloroplast structure and antioxidant systems of the Chinese cabbage seedlings, which ultimately increased the inhibitory effect of Cd exposure on the growth of Chinese cabbage. |
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