[D-Leu¹]MC-LR and MC-LR, two microcystins differing in one amino acid, constitute a sanitary and environmental problem owing to their frequent and concomitant presence in water bodies of the Americas and their association with human intoxication during recreational exposure to cyanobacterial bloom. Present in reservoirs used for irrigation as well, they can generate problems in the development of crops such as Phaseolus vulgaris, of nutritional and economic interest to the region. Although numerous works address the toxic effects of MC-LR, information on the toxicity of [D-Leu¹]MC-LR is limited. Our objective was to study the toxic effects of [D-Leu¹]MC-LR and MC-LR (3.5 µg/ml) on P. vulgaris after a single contact at the imbibition stage. Our findings indicate that 10 days post treatment, [D-Leu¹]MC-LR generates morphological and physiological alterations more pronounced than those caused by MC-LR. In addition to the alterations produced by [D-Leu¹]MC-LR in the development of seedlings and the structure of the leaves, roots and stems, we also found alterations in leaf stomatal density and conductivity, a longer delay in the phototropic response and a decrease in the maximum curvature angles achieved with respect to that observed for MC-LR. Our findings indicate that these alterations are linked to the greater inhibition of phosphatase activity generated by [D-Leu¹]MC-LR, rather than to oxidative damage. We observed that 30 days after treatment with MC-LR, plants presented better development and recovery than those treated with [D-Leu¹]MC-LR. Further studies are required on [D-Leu¹]MC-LR and MC-LR toxicity and their underlying mechanisms of action.

Excessive levels of zinc have detrimental effects on plant physiology and morphology, hindering growth and development. This study aimed to elucidate the morphophysiological and biochemical mechanisms of Schedonorus arundinaceus in response to high concentrations of zinc exposure and to investigate the correlation between these parameters to identify potential stress biomarkers in this species. Plants were exposed to seven zinc concentrations (0-500-1000-1500-2000-2500-3000 μM) for 50 days. The results showed decreased dry weight, root area, photosynthetic pigments, root soluble proteins and stomatal conductance with increasing zinc concentrations. Conversely, proline, malondialdehyde and leaf-soluble protein content increased. Histological observations revealed altered stomata size and abnormalities in root tissue. Zinc accumulation exceeded phytotoxic thresholds (100-400 mg kg-1) even at lower concentrations, reaching a maximum of 3432 mg kg-1 in shoots. Visible Zn-P crystals were observed on leaf surfaces at the highest zinc treatment. These results suggest that S. arundinaceus possesses a notable capacity to bioaccumulate zinc, particularly in the roots. Furthermore, the strong correlation between proline levels and zinc biomass concentration suggests its potential use as a stress biomarker for zinc-induced stress in this species. Highlights: Schedonorus arundinaceus demonstrated high zinc bioaccumulation, reaching up to 3432 mg kg-1 in shoots, surpassing phytotoxic thresholds by approximately 9 times. Exposure to high zinc concentrations led to reductions in dry weight, root area, photosynthetic pigments, stomatal conductance and roots soluble proteins content, while increasing proline, malondialdehyde (MDA) and leaves soluble protein content. At the highest zinc concentration, visible Zn-P crystals were observed on leaf surfaces, highlighting a unique physiological response. Histological observations revealed altered stomata size and, indicating significant morphological adaptations in response to zinc stress. The strong correlation between proline levels and zinc bioaccumulation suggests proline as a potential biomarker for zinc-induced stress in Schedonorus arundinaceus.

La incorporación de metales pesados al medio como modo de contaminación por el uso de fertilizantes y plaguicidas es una de las problemáticas que más preocupan a las organizaciones vinculadas al monitoreo del ambiente. El cobre es un micronutriente esencial para el crecimiento vegetal, pero en elevadas concentraciones es tóxico. Las micorrizas arbusculares, participan activamente en el metabolismo de los metales pesados, aumentando la tolerancia de las plantas que crecen en sitios contaminados. Se evaluaron las respuestas morfológicas y fisiológicas de plantas de pimiento inoculadas con el hongo micorrícico arbuscular Funneliformis mosseae en concentraciones crecientes de cobre en un cultivo hidropónico. Se realizaron mediciones morfológicas (peso seco, área foliar), fisiológicas (conductancia y resistencia estomática, índice de verdor, temperatura de hoja, conductividad relativa de membranas celulares) y bioquímicas (patrón proteico, contenido de malondialdehído). Las plantas inoculadas con el hongo micorrícico arbuscular toleraron una concentración mayor de cobre que las no inoculadas y esta concentración varió según el parámetro analizado. En general, en las plantas micorrizadas se observó un aumento del umbral de tolerancia al cobre.

Heavy metals are inorganic pollutants known for their high persistence in the environment and toxic effects even at trace concentrations. These contaminants are particularly relevant in peri-urban agricultural areas, where various domestic, industrial and agricultural activities serve as sources, potentially compromising food security. Phytoremediation is a sustainable and environmentally friendly approach that employs native plants to extract or mitigate heavy metals toxicity in contaminated environments. Additionally, it holds the potential to produce valuable phytoproducts, thereby facilitating the restoration and transformation of these sites into productive landscapes. This study evaluates the response of Lippia alba (Mill.) chemotype carvone, a native aromatic plant, to high concentrations of Zn(II) and Cu(II), focusing on its growth, bioaccumulation, and physiological and biochemical responses. Both metals negatively impacted plant growth, increasing electrolyte leakage and reducing chlorophyll, carotenoids and protein content. Despite these effects, L. alba demonstrated significant tolerance, with no mortality observed, supported by antioxidant defense mechanisms such as proline and phenolic compounds accumulation. Bioaccumulation of both metals exceeded phytotoxic thresholds, reaching 1.8–5.6 times higher for Zn(II) and 10.1–15.2 times higher for Cu(II). The plant primarily accumulated metals in the roots, with minimal translocation to the shoots. These findings suggest that L. alba could be effectively utilized in revegetation and phytoremediation of soils moderately contaminated with Zn(II) and Cu(II), functioning as a phytostabilizer.