Independent variation in copper tolerance and copper accumulation among crop species and varieties

Dianthus sylvestris subsp. sylvestris as a promising candidate for phytostabilization of copper-contaminated post-mining sites in Alpine ecosystems

The lack of remediation of inactive mine sites is a serious global concern, as they pose risks to the environment, human health, and safety. The potential of Dianthus sylvestris subsp. sylvestris to remediate post-mining sites contaminated with copper (Cu) at high altitudes, which is a challenging task for most management strategies, was explored in this study. More than 1300 mg Cu kg-1 in shoots were found in plants collected at the Monte Avanza legacy mine site (Alps). However, it is unclear whether this is due to hyperaccumulation or foliar contamination. To address this gap, field samples were washed with two different protocols, and a controlled Cu-tolerance test was conducted. While very high Cu concentrations, exceeding the Cu hyperaccumulation threshold of 300 mg kg-1, were found in samples washed with water, results for the plants cleaned with a more rigorous approach with EDTA suggested Cu exclusion strategy. Under controlled conditions, the plant showed Cu hypertolerance but did not hyperaccumulate Cu. Thus D. sylvestris presents a Cu exclusion strategy rather than hyperaccumulation potential, making it a suitable candidate for Cu phytostabilization at high altitude legacy mine sites. The study emphasizes the need for experiments under controlled conditions when assessing the phytoremediation potential.

Copper accumulation in five weed species commonly found in the understory vegetation of Mediterranean vineyards

Copper (Cu) concentration in agricultural soils often exceeds toxicological limits due to application of Cu-based fungicides. The potential of weeds for their use as functional cover plants in vineyard management and phytoremediation practices is little explored. We identified five weed species widely present in vineyards and assessed their Cu accumulation from eleven Mediterranean vineyards (soil Cu: 60-327 μg g-1) and two adjacent control sites (soil Cu: 15-30 μg g-1). Soils and plants were characterized by their physico-chemical properties and nutrient content. We applied multivariate techniques to analyze relationships between soil properties and leaf nutrient composition. Copper tolerance and accumulation traits were further tested in hydroponics using a series of CuSO4 concentrations (0.1-16 μM). Under field conditions, the highest Cu concentration in both roots and leaves were found in Lolium perenne (221 and 461 μg g-1, respectively), followed by Plantago lanceolata, Rumex obtusifolius and Taraxacum officinale (>100 μg g-1 Cu in leaves). Only one species, Trifolium repens, did not accumulate remarkable Cu concentrations. Overall, and as revealed by the multivariate analyses, leaf Cu concentration was driven by soil Cu content, soil texture, organic matter, nitrogen, and Cu uptake into roots. However, functional regression analysis and controlled experiments suggested that Cu might be additionally absorbed from the deposits on the leaf surface related to the Cu-fungicide treatments and soil dust. Our study highlights the importance of intra-specific variability in Cu accumulation among weed species in Cu-contaminated agricultural soils. Further validation of these findings under controlled conditions could provide essential insights for optimizing management and remediation strategies.

The effect of EDTA and citric acid on biochemical processes and changes in phenolic compounds profile of okra (Abelmoschus esculentus L.) under mercury stress

The present study aimed to explore the effect of synthetic and naturally occurring chelators, EDTA and citric acid (CA), respectively, on changes in physiological and biochemical factors including cell death, level of mercury ions accumulation, malondialdehyde (MDA) content, total phenol and total flavonoids, anthocyanins and DPPH free radical scavenging activity, in the leaves of okra (Abelmoschus esculentus L.) plants exposed to mercury stress. In addition, polyphenolic compounds profile was assessed by high-performance liquid chromatography. The okras were planted in completely controlled hydroponic conditions (Hoagland solution). After they reached the four-leaf stage, they were treated simultaneously with different concentrations of HgCl₂, EDTA and CA chelators, and their combination for one month. At the stage of maturity, the physiological and biochemical factors of the plant leaves were measured. The results showed that with the application of higher concentration of HgCl₂, cell death, level of shoot and root Hg²⁺ content and root MDA, total phenols and total flavonoids, anthocyanin content, and DPPH free radical scavenging activity were increased. Also, the results indicated that okra plants have high biomass and a high rate of Hg mobilization and accumulation in the shoot versus the roots (TF=2.152 for the plants treated with 60 mg L^-1 Hg²⁺), hence, can be considered as Hg hyperaccumulator plant for the phytoremediation of Hg-polluted soils and waters. In the Hg-treated plants changes in their phenolic profile were induced, and the increase of chlorogenic acid, rosmaric acid, apigenin, quercetin and rutin content was observed. The application of EDTA and CA improved the toxic effects of Hg²⁺, by modifying phenolic compounds, chelating Hg²⁺, and its proper compartmentation, while EDTA outperformed CA in this respect. Based on the results, it could be concluded that due to the high biomass and growth of okra in the presence of Hg²⁺, this plant is suitable for phytoremediation of soil and water contaminated with mercury. In addition, EDTA and CA can play a significant role in removing this toxic metal through transferring it from the culture medium to the plant.