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Soil pollution by heavy metals from industrial and anthropogenic activities is prevalent and a serious threat to ecosystems and humans. To immobilize heavy metal toxicity using trees is an effective and low-cost method for soil remediation. The present study was aimed to assess the most suitable bioindicator of trace elements including copper (Cu), cadmium (Cd), and lead (Pb) among Morus alba and Eucalyptus camaldulensis plant species at seven different sites in Faisalabad, an industrial city of Pakistan during the summer and winter seasons. Samples from the leaf, bark, deposited dust, and soil of both subjected species was collected for the assessment of metals accumulation. The recorded data showed that the trend of heavy metal concentration in soil, deposited dust, bark, and the leaf of both species was Pb > Cu > Cd. Generally, the maximum concentration of Cd, Cu, and Pb was recorded at the building material processing area during both seasons in both subjected species. Moreover, the highest concentration of Cd and Pb was recorded in leaf samples, while the highest concentration of Cu was recorded in dust samples. These results suggesting the idea that tree leaves can be used as a good indicator of Cd, and Pb concentration. In the case of Cu, a highly significant correlation (P < 0.05) was found between Cu concentration in deposited dust and leaves of both species during both growing seasons, indicating that the main source of Cu accumulation is atmospheric dust. Moreover, the summer season was more sensitive for the exposure of Cd, Cu, and Pb while, M. alba was proved as a good bioindicator and bioaccumulator for all recorded heavy metals during both seasons. According to the obtained results, M. alba trees are more likely to capture Cd, Cu, and Pb from the air, so planting these trees in industrial areas with such atmosphere pollutants would be beneficial. [ABSTRACT FROM AUTHOR]

Heavy metal toxicity causes a remarkable decline in the growth and yield of numerous plant species in the agricultural system. Cadmium (Cd) among the other heavy metals is the most distinguished lethal heavy metal as its higher water solubility, relative mobility, and phytotoxicity. Silicon (Si), as a second most abundant element, has been reported to mitigate numerous abiotic stresses, comprising heavy metal stress in plants. The 2-repeated studies were conducted to disclose the protective role of silica gel derived from sodium silicate (Na2SiO3) at the rate of 1 and 3 mmol L−1 on the root morphological characters of wheat plants grown in cultured medium with three levels of Cd toxicities (0, 50, and 200 µmol L−1). The results of our studies demonstrated a remarkable alteration in morphological traits of wheat roots with both levels of Cd toxicities through incorporating an excessive amount of reactive oxygen species (ROS), by lipid peroxidation, by limitation of essential nutrient availability, and by the accumulation of the high contents of Cd in root cells. While the introduction of Si nanoparticles at the rate of 1 and 3 mmol L−1 in the cultured medium having Cd toxicities remarkably demolished Cd adversity by shifting the balance between antioxidant enzymes and oxidants of ROS. Moreover, Si significantly increased cations concentrations in root tips that compete with Cd ions for exchange sites and reduced Cd uptake and accumulation by roots. Being an effective beneficial element, Si improved root morphological characters by strengthening the antioxidative defense system and by hindering ROS in root tissues grown in a cultured medium with different toxicities of Cd. [ABSTRACT FROM AUTHOR]

Silicon (Si), as a quasi-essential element, has a vital role in alleviating the damaging effects of various environmental stresses on plants. Cadmium (Cd) stress is severe abiotic stress, especially in acidic ecological conditions, and Si can demolish the toxicity induced by Cd as well as acidic pH on plants. Based on these hypotheses, we demonstrated 2-repeated experiments to unfold the effects of Si as silica gel on the root morphology and physiology of wheat seedling under Cd as well as acidic stresses. For this purpose, we used nine treatments with three levels of Si nanoparticles (0, 1, and 3 mmol L−1) derived from sodium silicate (Na2SiO3) against three concentrations of Cd (0, 50, and 200 µmol L−1) in the form of cadmium chloride (CdCl2) with three replications were arranged in a complete randomized design. The pH of the nutrient solution was adjusted at 5. The averages of three random replications showed that the mutual impacts of Si and Cd in acidic pH on wheat roots depend on the concentrations of Si and Cd. The collective or particular influence of low or high levels of Si (1 or 3 mM) and acidic pH (5) improved the development of wheat roots, and the collective influence was more significant than that of a single parallel treatment. The combined effects of low or high concentrations of Cd (50 or 200 µM) and acidic pH significantly reduced root growth and biomass while increased antioxidants, and reactive oxygen species (ROS) contents. The incorporation of Si (1 or 3 mmol L−1) in Cd-contaminated acidic nutrient solution promoted the wheat root growth, decreased ROS contents, and further increased the antioxidants in the wheat roots compared with Cd single treatments in acidic pH. The demolishing effects were better with a high level of Si (3 mM) than the low level of Si (1 Mm). In conclusion, we could suggest Si as an effective beneficial nutrient that could participate actively in several morphological and physiological activities of roots in wheat plants grown under Cd and acidic pH stresses. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s41742-021-00340-2 [ABSTRACT FROM AUTHOR]