Effects of copper oxide nanoparticles on germination of Sesbania virgata (FABACEAE) plants.

Nanotechnology is a field that, over the years, has been growing in several research areas, such as medicine, agriculture and cosmetics, among others. As a result, there is a continuous increase in the production, use and disposal of these materials in the environment. The behaviour and (bio) activity of these materials in the atmosphere, water and soil are not fully studied. Therefore, it is necessary to carry out an analysis of the risks of contamination, as well as the possible effects and impacts of nanoparticles (NPs) on the ecosystem. In an attempt to investigate these effects on plants, the present study aimed to investigate the impact of copper oxide nanoparticles (CuO NPs) on the seed germination process of Sesbania virgata. For this, the Sesbania virgata seeds were subjected to different concentration of CuO NPs (0, 100, 200, 300 and 400 mgL-1) and their germination and development were monitored by optical analysis (thermography and chlorophyll a fluorescence). The results show that the CuO NPs induced a reduction on the maximum emission of chlorophyll a, which was concentration-dependent. The data also showed that CuO NPs promoted an increase in the energy dissipated by non-photochemical pathways and the surface temperature of the seeds. Additionally, our findings revealed that CuO NPs caused a root growth inhibition. In summary, the present study demonstrates, for the first time, that CuO NPs can negatively affect the physiological status and development of the S. virgata plant, by altering the efficiency of the functioning of photosystem II in its initial developmental stage, depending on the concentration of CuO NPs.

Phytotoxicity of silver nanoparticles on Vicia faba: Evaluation of particle size effects on photosynthetic performance and leaf gas exchange.

Nanotechnology is an emerging field in science and engineering, which presents significant impacts on the economy, society and the environment. The nanomaterials' (NMs) production, use, and disposal is inevitably leading to their release into the environment where there are uncertainties about its fate, behaviour, and toxicity. Recent works have demonstrated that NMs can penetrate, translocate, and accumulate in plants. However, studies about the effects of the NMs on plants are still limited because most investigations are carried out in the initial stage of plant development. The present study aimed to evaluate and characterize the photochemical efficiency of photosystem II (PSII) of broad bean (Vicia faba) leaves when subjected to silver nanoparticles (AgNPs) with diameters of 20, 51, and 73 nm as well as to micrometer-size Ag particles (AgBulk). The AgNPs were characterized by transmission electron microscopy and dynamic light scattering. The analyses were performed by injecting the leaves with 100 mg L-1 aqueous solution of Ag and measuring the chlorophyll fluorescence imaging, gas exchange, thermal imaging, and reactive oxygen species (ROS) production. In addition, silver ion (Ag+) release from Ag particles was determined by dialysis. The results revealed that AgNPs induce a decrease in the photochemical efficiency of photosystem II (PSII) and an increase in the non-photochemical quenching. The data also revealed that AgNPs affected the stomatal conductance (gs) and CO2 assimilation. Further, AgNPs induced an overproduction of ROS in Vicia faba leaves. Finally, all observed effects were particle diameter-dependent, increasing with the reduction of AgNPs diameter and revealing that AgBulk caused only a small or no changes on plants. In summary, the results point out that AgNPs may negatively affect the photosynthesis process when accumulated in the leaves, and that the NPs themselves were mainly responsible since negligible Ag+ release was detected.

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 (qPd) 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.

Cytotoxic and genotoxic effects of silver nanoparticles on meristematic cells of Allium cepa roots: A close analysis of particle size dependence.

The use of silver nanoparticles (AgNPs) in commercial products has increased significantly in recent years. However, findings on the toxic effects of the AgNPs are still limited. This paper reports an investigation on the cytotoxic and genotoxic potential of the AgNPs on root cells of Allium cepa. Germination (GI), root elongation (REI), mitotic (MI), nuclear abnormality (NAI), and micronucleus index (MNI) were determined for seeds exposed to various AgNPs diameters (10, 20, 51, and 73 nm) as well as to the silver bulk (AgBulk) (micrometer-size particles) at the concentration of 100 mg·L-1. Transmission electron microscopy (TEM) provided the particle size distribution, while dynamic light scattering (DLS) was used to get the hydrodynamic size, polydispersity index, and zeta potential of the AgNPs. Laser-induced breakdown spectroscopy (LIBS) and inductively coupled plasma/optical emission spectrometry (ICP OES) were applied for quantifying the AgNPs content uptake by roots. Silver dissolution was determined by dialysis experiment. Results showed that the AgNPs penetrated the roots, affecting MI, GI, NAI, and MNI in meristematic cells. Changes in these indicators were AgNPs diameter-dependent so that cytotoxic and genotoxic effects in Allium cepa increased with the reduction of the particle diameter. The results also revealed that the AgNPs were the main responsible for the cytotoxicity and genotoxicity since negligible silver dissolution was observed.