Dear Colleagues,

Phytoremediation is a powerful, cost-effective, and fully sustainable technology. Limitations of the technologies could be resumed in three factors—contaminant phytotoxicity, adverse environmental factors on plant growth (drought, salinity, critical climate condition, etc.), and often the slow action on contaminant treatment by the plant. Research is ongoing in clarifying involved processes (chemical, physical, and biological) to bring the development of new strategies aimed at improving phytotechnology performance. The interactions between the host plant and associated microorganisms are the basis of phytoremediation technology. Plants can develop a powerful symbiotic connection with their roots' microbial flora. This close relationship between plant and microbial physiology supports plants' development and growth subjected to biotic and abiotic stresses. Several environmental stresses, such as hydrocarbons, heavy metals, heat, cold, drought, salinity, etc., generate physiological responses from complex and coordinated interactions between the soil microorganisms, the rhizosphere's microbial community, and the host plants.

Undoubtedly, phytoremediation offers the highest environmental sustainability index, but further progress in technological efficiency is needed. A better understanding of soil microorganisms and plant-microorganism relations is essential to reaching higher economic and ecological sustainability levels. To achieve this purpose, holistic approaches using “omics” technologies (metagenomics, meta-proteomics, meta-transcriptomics, etc.) can successfully promote an improved and in-depth understanding of the plant-microorganism interactions.

This Special Issue of Plants will explore and highlight consolidated and innovative phytoremediation approaches to counteract the adverse effects of different environmental stresses on plant growth.

Two sections will be set up based on the type of contaminant approached: inorganic (including radionuclides) and organic. The sections will be further organized into two subgroups based on the experimental scale adopted: lab/greenhouse and field scale. A further section will be dedicated to the energy enhancement of phytoremediation biomass, an important step to make the technology even more sustainable.

Dr. Elisabetta Franchi
Dr. Meri Barbafieri
Prof. Dr. Raffaella Maria Balestrini
Guest Editors

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• plant-based technologies
• plant-microbe interaction
• marginal soils
• organic and inorganic contaminants
• biomass valorization
• sustainability

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.