Cadmium uptake by maize from polluted river sediments covered with a clean top layer of variable thickness is discussed in relation to root distribution. Two pathways for uptake are distinguished: roots penetrating the contaminated layer or contaminants moving into the root zone. Relative Cd uptake proved to be roughly proportional to the fraction of total root length found in the contaminated layer. A deeper water table induced a deeper root development and more Cd uptake for a given thickness of clean topsoil. A model based on exponential decrease of root length density with depth is acceptable as first approximation only. Little or no evidence was found for contaminants moving into the root zone during the ten years of the experiment.
Tag: cadmium
Interactions between regenerative strategies and edaphic, climatic and topographic factors mediate mitigation or exacerbation of soil and crop toxicity in global cadmium contaminated lands
Cadmium (Cd) contamination in agroecosystems is a global concern, due to its negative influence on soil health and crop performance. Regenerative strategies have been widely recognised as vital to improve soil quality and crop yields. Yet strategies are needed that also mitigate rather than exacerbate the impacts of Cd contamination. In this context, interactions between regenerative strategies, and edaphic, climatic and topographic factors are poorly understood. This study presents a meta-analysis with effect size statistics, evaluating the interactions between regenerative strategies (biochar, manure and compost), non- regenerative strategies (sewage-sludge and fertilizer), soil properties (pH, SOM and Cd levels), climatic factors (temperature and precipitation), and elevation. In acidic or high SOM soils, fertilizer increased Cd uptake by 50% to 76%. However, biochar or compost addition in these soils reduced Cd uptake. Under high Cd contamination, biochar application increased shoot biomass, but fertilizer application decreased shoot-biomass. The application of fertilizer or sewage-sludge under higher temperatures increased Cd uptake, whereas biochar reduced Cd uptake. At wet sites, fertilizer addition increased soil Cd accumulation. At high elevations, biochar was more effective than manure at reducing Cd accumulation. We conclude that there are complex interactions between regenerative strategies and environmental conditions; determining impacts on soil and crop health. The interactions between environmental factors and use of sewage-sludge or fertilizer could exacerbate soil and plant Cd toxicity. Regenerative strategies, especially biochar, could mitigate Cd toxicity in agroecosystems.
Solvothermal synthesis of CdS–graphene composites by varying the Cd/S ratio
Graphite oxide was prepared by Hummers method and treated by ultrasonic waves to obtain graphene oxide. CdS–graphene composites were successfully synthesized via a one-step solvothermal method with different Cd/S ratios, with cadmium acetate as cadmium source, thiourea as sulfur source and ethylene glycol as reaction solvent and characterized by X-ray diffraction, scanning electron microscopy and UV–vis absorption spectra. The photoelectric characteristics of CdS–graphene composites were evaluated by transient photocurrent response and three-electrode cyclic voltammetry.
Quantitative Succinyl-Proteome Profiling of Turnip (Brassica rapa var. rapa) in Response to Cadmium Stress
Protein post-translational modification (PTM) is an efficient biological mechanism to regulate protein structure and function, but its role in plant responses to heavy metal stress is poorly understood. The present study performed quantitative succinyl-proteome profiling using liquid chromatography–mass spectrometry analysis to explore the potential roles of lysine succinylation modification in turnip seedlings in response to cadmium (Cd) stress (20 μM) under hydroponic conditions over a short time period (0–8 h). A total of 547 succinylated sites on 256 proteins were identified in the shoots of turnip seedlings. These succinylated proteins participated in various biological processes (e.g., photosynthesis, tricarboxylic acid cycle, amino acid metabolism, and response to stimulation) that occurred in diverse cellular compartments according to the functional classification, subcellular localization, and protein interaction network analysis. Quantitative analysis showed that the intensities of nine succinylation sites on eight proteins were significantly altered (p < 0.05) in turnip shoots after 8 h of Cd stress. These differentially succinylated sites were highly conserved in Brassicaceae species and mostly located in the conserved domains of the proteins. Among them, a downregulated succinylation site (K150) in the glycolate oxidase protein (Gene0282600.1), an upregulated succinylation site (K396) in the catalase 3 protein (Gene0163880.1), and a downregulated succinylation site (K197) in the glutathione S-transferase protein (Gene0315380.1) may have contributed to the altered activity of the corresponding enzymes, which suggests that lysine succinylation affects the Cd detoxification process in turnip by regulating the H2O2 accumulation and glutathione metabolism. These results provide novel insights into understanding Cd response mechanisms in plants and important protein modification information for the molecular-assisted breeding of Brassica varieties with distinct Cd tolerance and accumulation capacities.
Comparative Transcriptomics Analysis of Roots and Leaves under Cd Stress in Calotropis gigantea L.
Calotropis gigantea is often found in mining areas with heavy metal pollution. However, little is known about the physiological and molecular response mechanism of C. gigantea to Cd stress. In the present study, Cd tolerance characteristic of C. gigantea and the potential mechanisms were explored. Seed germination test results showed that C. gigantea had a certain Cd tolerance capacity. Biochemical and transcriptomic analysis indicated that the roots and leaves of C. gigantea had different responses to early Cd stress. A total of 176 and 1618 DEGs were identified in the roots and leaves of C. gigantea treated with Cd compared to the control samples, respectively. Results indicated that oxidative stress was mainly initiated in the roots of C. gigantea, whereas the leaves activated several Cd detoxification processes to cope with Cd, including the upregulation of genes involved in Cd transport (i.e., absorption, efflux, or compartmentalization), cell wall remodeling, antioxidant system, and chelation. This study provides preliminary information to understand how C. gigantea respond to Cd stress, which is useful for evaluating the potential of C. gigantea in the remediation of Cd-contaminated soils.