In Vivo and In Vitro Studies on Heavy Metal Tolerance in Plants

Dear Colleagues,

Much has already been done to improve water, soil and air quality; however, existing emission standards and the lack of reasonable pollution management in transport and industry sectors result in only a slow decrease in global heavy metal (e.g., cobalt, chromium, lead, nickel, cadmium, mercury, arsenic, copper) pollution. Physical and chemical methods that have repeatedly been protested against or restricted have not been very effective in cleaning contaminated ecosystems. Biological methods, including the use of plants, are the most effective in removing metals from the environment. The natural potential of plants, e.g., metallophytes and hyperaccumulators that exhibit evolutionary adaptation to high concentrations of heavy metals in the soil, should be explored. Phytoremediation is an eco-friendly and sustainable mode of toxic heavy metal removal, and utilizes plants to remediate contaminated soil and water. Therefore, demands for fast-growing, metal-tolerant plants with high biomass are not diminishing. Such plants could also find use in a recently developed technology called plant-assisted (phyto-assisted) bioremediation, exploiting the synergistic action between plant root systems and microorganisms and leading to the conversion, removal or retention of heavy metals in sediments or water.

Plant tissue cultures, including cells in suspensions, callus, and organ culture (e.g., hairy roots) serve as model plant systems. Both in vitro cultures and in vivo studies offer a range of experimental advantages which are obviously not without drawbacks and limitations. Although heavy metal distribution as well as transcriptomic and metabolic profiles could vary depending on the specificity of the plant material and growth/culture conditions, conventional in vitro culture experiments are an excellent tool to predict the responses of plants to heavy metals. Well-designed experiments can reduce the cost and time required for subsequent whole-plant procedures in the field.

In this Special Issue, we will engage in a discussion of these topics and try to point out the validity and complementarity of both types of research. We welcome the submission of papers contributing to the knowledge on the mechanisms of heavy metal tolerance (basic science), as well as those on phytoremediation and bioremediation (applied sciences) and any other aspects related to the topic.

Dr. Aneta Słomka
Dr. Ewa Muszyńska
Guest Editors

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• metallophytes
• hyperaccumulators
• heavy metal tolerance
• phytoremediation
• bioremediation
• in vitro culture
• in vivo studies

Title: Tolerance to Zn and Cd in artificial polyploid of the pseudometallophyte Arabidopsis arenosa
Authors: Aneta Słomka
Affiliation: Faculty of Biology, Institute of Botany, Jagiellonian University in Kraków, 9 Gronostajowa St., 30-387 Cracow, Poland

Title: Lonchocarpus cultratus, a tropical woody plant, as a potential phytoremediator of manganese-contaminated areas
Authors: Lucas Anjos de Souza
Affiliation: Instituto Federal Goiano - Campus Rio Verde
Abstract: Human activities are increasing the environmental contamination by different pollutants, such as the trace element manganese (Mn). The phytoremediation potential of woody plants, especially from tropical areas, is little known. Therefore, this study aimed to evaluate the development and phytoremediation capacity of Lonchocarpus cultratus, a Brazilian savanna tree, under exposure to increasing manganese (Mn) concentrations in soil. Plants were grown in soil containing 49 (control), 56, 74, 105 mg kg-1 for six months, and their physiology, development and phytoremediation capacity were assessed. The Mn accumulation in plants, which initially ranged from 339 to 1523 mg kg-1 in the different organs, was risen in roots (30%), stems (225%) and leaves (33%) by increasing soil Mn levels. The stem and root biomasses were maintained in plants challenged by the increased Mn level in soil. By contrast, the leaf biomass decreased (28–53%) concurrently to increases in the leaf Mn concentration that, in turns, was inversely correlated with the photochemical quenching (r=-59.57%, p<0.01). Gas exchange-related variables were not affected by Mn levels. In conclusion, L. cultratus is able to accumulate high Mn concentrations, in which stems were the greatest hub for the Mn excess. However, an increased entrance of Mn in plants affects negatively the biomass production due to decreases in the photochemical quenching efficiency. Moreover, leaves were the most sensitive organ to Mn excess, probably due to changes in the pattern of biomass allocation (for stems and roots in detriment of leaves), when photosynthate production was impacted in L. cultratus.