Cadmium tolerance and detoxification in Myriophyllum aquaticum : physiological responses, chemical forms, and subcellula
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RESEARCH ARTICLE
Cadmium tolerance and detoxification in Myriophyllum aquaticum: physiological responses, chemical forms, and subcellular distribution Guoxin Li 1
&
Qingsong Li 1 & Lei Wang 1 & Dandan Zhang 2
Received: 18 October 2019 / Accepted: 23 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Submerged macrophytes have been found to be promising in removing cadmium (Cd) from aquatic ecosystems; however, the mechanism of Cd detoxification in these plants is still poorly understood. In the present study, Cd chemical forms and subcellular distributing behaviors in Myriophyllum aquaticum and the physiological mechanism underlying M. aquaticum in response to Cd stress were explored. During the study, M. aquaticum was grown in a hydroponic system and was treated under different concentrations of Cd (0, 0.01, 0.05, 0.25, and 1.25 mg/L) for 14 days. The differential centrifugation suggested that most Cd was split in the soluble fraction (57.40–66.25%) and bound to the cell wall (24.92–38.57%). Furthermore, Cd in M. aquaticum was primarily present in NaCl-extractable Cd (51.76–91.15% in leaves and 58.71–84.76% in stems), followed by acetic acid– extractable Cd (5.17–22.42% in leaves and 9.54–16.56% in stems) and HCl-extractable Cd (0.80–12.23% in leaves and 3.56– 18.87% in stems). The malondialdehyde (MDA) and hydrogen peroxide (H2O2) concentrations in M. aquaticum were noticeably increased under each Cd concentration. The activities of catalase (CAT), guaiacol peroxidase (POD), and superoxide dismutase (SOD) in leaves were initially increased under relatively low concentrations of Cd but were decreased further with the increasing concentrations of Cd. The ascorbate (AsA), glutathione (GSH), and nitric oxide (NO) concentrations in stems increased with increasing Cd concentrations. Taken together, our results indicate that M. aquaticum can be used successfully for phytoremediation of Cd-contaminated water, and the detoxification mechanisms in M. aquaticum include enzymatic and nonenzymatic antioxidants, subcellular partitioning, and the formation of different chemical forms of Cd. Keywords Cadmium . Myriophyllum aquaticum . Subcellular distribution . Chemical forms . Physiological responses
Introduction The contamination of aquatic ecosystems due to heavy metals has been extensively highlighted in recent decades (Chen et al. 2019). In order to be specific, cadmium (Cd) refers to the most phytotoxic element with no known biological functions in various types of plants. The main sources of Cd contamination are industrial development, mining, and application of sewage sludge and phosphate fertilizer to the land (Shi et al. 2016). Responsible Editor: Gangrong Shi * Guoxin Li [email protected] 1
College of Environmental Sciences and Engineering, Xiamen University of Technology, Xiamen, China
2
Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
Plants under the influence of Cd contamination display damaged photosynthetic system, promoted senescence, and defe
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