Toxicity of bisphenol A (BPA) and its analogues BPF and BPS on the free-floating macrophyte Salvinia biloba

Evidence linking the toxicity of bisphenol A (BPA) to environmental and public-health issues has led to restrictions on its use. This compound has been gradually replaced with analogues proposed as a safer alternative, normally bisphenol F (BPF) and bisphenol S (BPS), but these substitutes are structurally almost identical to BPA, suggesting they may pose similar risks. The effects of BPA and these analogues were compared for antioxidant activity, lipid peroxidation, free-radical generation, photosynthetic pigments, and chlorophyll fluorescence in Salvinia biloba Raddi (S. biloba) plants exposed to environmentally relevant and sublethal concentrations (1, 10, 50, 100 and 150 μM). Bisphenol exposure promoted alterations in most of the physiological parameters investigated, with BPS toxicity differing slightly from that of the analogues. Furthermore, S. biloba removed similar levels of BPA and BPF from aqueous solutions with ≈70% removed at the 150 μM concentration, while BPS was less effectively removed, with only 23% removed at 150 μM. These findings show that high concentrations of bisphenols (10≥) are toxic to S. biloba, and even typical environmental levels (≤1 μM) can induce metabolic changes in plants, bringing to light that both BPA and its substitutes BPF and BPS pose risks to aquatic ecosystems.

Ecophysiological mechanisms and growth of Inga vera Willd. under different water and light availability

Light and water availability can impact plant survival and growth, making ecophysiological studies crucial for understanding their tolerance and to single and combined stresses. The aimed of this study was to investigate the physiological and growth responses of Inga vera Willd. plants induced by different water regimes and light intensities. Three water regimes were implemented based on substrate water retention capacity (WRC) - 50%, 75%, and 100%, along with shading levels (SH) - 0% (full sun), 30%, and 70%. Evaluations were conducted at 25 and 50 days after applying the water regimes, and during a recovery period of 30 days when all treatments were maintained at 75% of WRC. Photochemical efficiency, gas exchange, chlorophylls indices, growth, quality of the seedlings and content proline amino acid were assessed. Overall, I. vera plants showed greater sensitivity to increased exposure to light than to low water availability. The interaction of SH + WRC was beneficial for the gas exchange and chlorophylls indices characteristics under SH 70% + WRC 75-100% at 25 and 50 days, with higher results, greater plant growth and higher proline contents for leaves and roots under SH 30% and 70% + WRC 50%, 75% and 100% at 25 and 50 days. There was no recovery effect for seedlings grown in full sun. The plants grown under shade during the recovery period maintained their values for most of the characteristics evaluated. SH 30% + WRC 75% contributed to an increase in photosynthetic metabolism and, as a result, to the quality of the seedlings.

Assessing the Fate of Superparamagnetic Iron Oxide Nanoparticles Carrying Usnic Acid as Chemical Cargo on the Soil Microbial Community

In the present study we evaluate the effect of superparamagnetic iron oxide nanoparticles (SPIONs) carrying usnic acid (UA) as chemical cargo on the soil microbial community in a dystrophic red latosol (oxysol). Herein, 500 ppm UA or SPIONs-framework carrying UA were diluted in sterile ultrapure deionized water and applied by hand sprayer on the top of the soil. The experiment was conducted in a growth chamber at 25 °C, with a relative humidity of 80% and a 16 h/8 h light-dark cycle (600 lx light intensity) for 30 days. Sterile ultrapure deionized water was used as the negative control; uncapped and oleic acid (OA) capped SPIONs were also tested to assess their potential effects. Magnetic nanostructures were synthesized by a coprecipitation method and characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), zeta potential, hydrodynamic diameter, magnetic measurements, and release kinetics of chemical cargo. Uncapped and OA-capped SPIONs did not significantly affect soil microbial community. Our results showed an impairment in the soil microbial community exposed to free UA, leading to a general decrease in negative effects on soil-based parameters when bioactive was loaded into the nanoscale magnetic carrier. Besides, compared to control, the free UA caused a significant decrease in microbial biomass C (39%), on the activity of acid protease (59%), and acid phosphatase (23%) enzymes, respectively. Free UA also reduced eukaryotic 18S rRNA gene abundance, suggesting a major impact on fungi. Our findings indicate that SPIONs as bioherbicide nanocarriers can reduce the negative impacts on soil. Therefore, nanoenabled biocides may improve agricultural productivity, which is important for food security due to the need of increasing food production.

Effects of substrates containing different concentrations of sewage sludge on physiological parameters and quality of Alibertia edulis (Rubiaceae) seedlings

Sewage sludge (SS), a solid residue of effluent treatment, is rich in organic matter and nutrients, while also containing heavy metals and other potential contaminants. The feasibility of employing SS as a substrate component for seedling production depends on its composition and dose, as well as on the tolerance limit of individual plant species. To expand the knowledge base on the use of SS in the production of plants native to the Brazilian Cerrado biome, we evaluated the physiological responses and quality of Alibertia edulis seedlings grown under distinct SS concentrations. Chlorophyll a fluorescence (ChlF), stomatal conductance (gs), leaf temperature (Lt), biomass, growth, and seedling quality were investigated. At 25%, SS improved growth, biomass, and seedling quality, while substrates containing 50% or more SS affected gs, Lt, and ChlF. Seedling quality was strongly worsened by SS at 75% and 100%, as shown by lower biomass and impaired growth, including leaf symmetry loss and leaf deformities possibly related to contaminants, particularly heavy metals. Accordingly, we conclude that SS exhibited potential as a fertilizer at concentrations below 50%, but exerted a toxic effect on seedlings at higher concentrations.

Physiological mechanisms and phytoremediation potential of the macrophyte Salvinia biloba towards a commercial formulation and an analytical standard of glyphosate

Glyphosate (Gly) is the most widely used herbicide in the world and has broad-spectrum and non-selective activity. Its indiscriminate use hence risks contamination of water bodies and can affect living organisms, especially sensitive or resistant non-target plants. Despite this, studies on physiological mechanisms and Gly remediation in Neotropical aquatic plants remain limited. This study aims to evaluate the physiological mechanisms of the aquatic macrophyte Salvinia biloba on exposure to different concentrations of a Gly commercial formulation (Gly-CF) and a Gly analytical standard (Gly-AS). Furthermore, using square-wave voltammetry (SWV), we determined whether the studied plant could remove Gly from water. Our data suggest that Gly-AS and Gly-CF induce similar physiological responses in S. biloba. However, Gly-CF was more phytotoxic. Depending on the concentration, the two forms of Gly affected the plants, decreasing the chlorophyll a and b contents and the photosystem II (PSII) photochemical activity. The data also revealed that Gly promoted oxidative stress and increased the shikimic acid concentration. At the same time, the plants removed Gly from water, with 100% removal for 1 mg L-1 Gly and above 60% removal for the other concentrations studied. Therefore, our results suggest that S. biloba may be a potential phytoremediation agent for low Gly concentrations, since 1 mg L-1 Gly was completely removed and exhibited low phytotoxicity. This study deepens our scientific understanding of the Gly impact on and the phytoremediation potential of S. biloba.