Can the Chlorophyll-a Fluorescence be Useful in Identifying Acclimated Young Plants from Two Populations of Cecropia Pachystachya Trec. (Urticaceae), Under Elevated CO2 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.

How does aquatic macrophyte Salvinia auriculata respond to nanoceria upon an increased CO2 source? A Fourier transform-infrared photoacoustic spectroscopy and chlorophyll a fluorescence study

With the continued increase of technological uses of cerium oxide nanoparticles (CeO₂ NPs or nanoceria) and their unregulated disposal, the accumulation of nanoceria in the environment is inevitable. Concomitantly, atmospheric carbon dioxide (CO₂) levels continue to rise, increasing the concentrations of bicarbonate ions in aquatic ecosystems. This study investigates the influence of CeO₂ NPs (from 0 to 100 μgL^-1) in the presence and absence of an elevated bicarbonate (HCO₃^-) ion concentration (1 mM), on vibrational biochemical parameters and photosystem II (PSII) activity in leaf discs of Salvinia auriculata. Fourier transform-infrared photoacoustic spectroscopy (FTIR-PAS) was capable of diagnostic use to understand biochemical and metabolic changes in leaves submitted to the CeO₂ NPs and also detected interactive responses between CeO₂ NPs and HCO₃^- exposure at the tissue level. The results showed that the higher CeO₂ NPs levels in the presence of HCO₃^- increased the non-photochemical quenching (NPQ) and coefficient of photochemical quenching in dark (qP_d) compared to the absence of HCO₃. Moreover, the presence of HCO₃^- significantly decreased the NPQ at all levels of CeO₂ NPs demonstrating that HCO₃^- exposure may change the non-radiative process involved in the operation of the photosynthetic apparatus. Overall, the results of this study are useful for providing baseline information on the interactive effects of CeO₂ NPs and elevated HCO₃^- ion concentration on photosynthetic systems.