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.

Molecular and cytogenetic assessment of Dipterygium glaucum genotoxicity.

The aim of the present study is to assess the genotoxicity of Dipterygium glaucum grows widely in Saudi Arabia desert to produce safety herbal products. This work is considered the first and pioneer report so far due to the lack and poor evaluated reports of the plant species for their mutagensity, genotoxicity and cytogenetics effects. Cytogenetic effects of D. glaucum on mitotic in roots of Vicia faba showed reduction in mitotic activity using three extracts; water, ethanol and ethyl acetate. Chromosomal abnormalities were recorded that included stickiness of chromosomes, chromatin bridge, fragments, lagging chromosome and micronuclei. Protein bands and RAPD analyses of V. faba treated with three D. glaucum extracts revealed some newly induced proteins and DNA fragments and other disappeared. Chemical constitution of the plant species should be identified with their biological activities against human and animal cells like HeLa cancer cell line. We are recommending using additional genotoxicity tests and other toxicity tests on animal culture with different concentrations and also utilizing several drought and heat tolerant genes of the plant species in gene cloning to develop and improve other economical crop plants instead of using the species as oral herbal remedy.

Genotoxicity assessment of particulate matter emitted from heavy-duty diesel-powered vehicles using the in vivo Vicia faba L. micronucleus test.

Diesel exhaust particulate matter (PM) can have an impact on the environment due to its chemical constitution. A large number of substances such as organic compounds, sulfates, nitrogen derivatives and metals are adsorbed to the particles and desorption of these contaminants could promote genotoxic effects. The objective of this study was to assess the in vivo genotoxicity profile of diesel exhaust PM from heavy-duty engines. Extracts were obtained through leaching with pure water and chemical extraction using three organic solvents (dichloromethane, hexane, and acetone). The in vivo Vicia faba micronucleus test (ISO 29200 protocol) was used to assess the environmental impact of the samples collected from diesel exhaust PM. The solid diesel PM (soot) dissolved in water, and the different extracts, showed positive results for micronucleus formation. After the addition of EDTA, the aqueous extracts did not show a genotoxic effect. The absence of metals in the organic solvent extract indicated that organic compounds also had a genotoxic effect, which was not observed for a similar sample cleaned in a C18 column. Thus, considering the ecological importance of higher plants in relation to ecosystems (in contrast to Salmonella spp., which are commonly used in mutagenicity studies), the Vicia micronucleus test was demonstrated to be appropriate for complementing prokaryotic or in vitro tests on diesel exhaust particulate matter included in risk assessments.

Use of agro-industrial organic sludge amendment to remediate degraded soil: chemical and eco(geno)toxicological differences between fresh and stabilized sludge and establishment of application rates.

Soil degraded by coal mining activities can be remediated by amendment with agro-industrial organic sludge. However, the environmental impacts associated with this management practice must be properly addressed. In this context, the objective of this study was to evaluate the eco(geno)toxicity of a fresh and a stabilized sludge before use in a laboratory soil remediation test. Chemical analysis of the complex mixtures (degraded soil, fresh sludge, and stabilized sludge) was carried out, as well as a battery of eco(geno)toxicity tests on microbiological enzymes (fluorescein hydrolysis), earthworms, and higher plants (including Vicia faba genotoxicity test), according to published methodologies. The results of these tests showed that fresh sludge was more toxic than sludge stabilized over 6 months toward earthworms and higher plants (lettuce, corn, and wild cabbage), while phyto(geno)toxicity tests with V. faba indicated the same genotoxicity levels for the two types of sludge. In the soil remediation simulation using different mixtures of degraded soil and stabilized sludge, the proportions of 50:50% (dry weight basis) provided the lowest phyto(geno)toxicity effects and this mixture can be used for the revegetation of the contaminated site.

DNA Damage in Vicia faba by Exposure to Agricultural Soils from Tlaxcala, Mexico.

The aim of this research was to quantify some POPs, such as p,p' DDT, p,p' DDE, and PCBs in agricultural soils of Tlaxcala, Mexico and evaluate their capacity for eliciting DNA damage, using Vicia faba as bioindicator. The values of ΣDDTs and ΣPCBs ranged from 8-24 to 118-26,983 µg/kg, respectively. The samples T1 (HQ = 9.3) and T2 (HQ = 53.9) showed concentrations of ΣPCBs higher than Canadian guidelines (SQGE = 500 µg/kg). The genotoxicity testing produced percentages of DNA fragmentation higher than negative control and statistically significant (p < 0.05), both in agricultural soils and organic extracts. The soils T2, T3, N4, and N5 showed a DICA from 2.6 to 3.1 times, statistically higher (p < 0.05) than negative control. In general, the agricultural soils have greater genotoxic capacity than the organic extracts, suggesting a potential risk to biota that depends upon this ecosystem.

Evaluation of the genotoxic potential of reactive black 5 solutions subjected to decolorizing treatments by three fungal strains.

The genotoxic potential of solutions of the textile dye "Reactive Black 5" that were subjected to decolorizing treatments with the fungal strains Coriolopsis polyzona MUCL33483, Penicillium sp. MUBA001 and Pycnoporus sp. MUBA002 was tested. The genotoxicity of the solutions was determined by evaluation of micronuclei formation in Vicia faba root cells and calculation of a damage index (MN(ID)). Non-treated Reactive Black 5 solutions (50-1000 ppm) caused a statistically significant increase in micronuclei formation and, by then, in damage index. Solutions of dye treated with C. polyzona MUCL33483 and Pycnoporus sp. MUBA002 showed color loss, probably due to enzymatic breakdown of the colorant, but maintenance or even an increase in genotoxicity. On the other hand, the Penicillium sp. strain MUBA001 caused decolorization of the dye, apparently by adsorption on mycelia, and, for solutions that initially contained 50 ppm of colorant, an elimination of the genotoxicity was observed after three weeks of treatment.

Hydrogen sulphide, a novel gasotransmitter involved in guard cell signalling.

Hydrogen sulphide (H(2) S) has been proposed as the third gasotransmitter. In animal cells, H(2) S has been implicated in several physiological processes. H(2) S is endogenously synthesized in both animals and plants by enzymes with l-Cys desulphydrase activity in the conversion of l-Cys to H(2) S, pyruvate and ammonia. The participation of H(2) S in both stomatal movement regulation and abscisic acid (ABA)-dependent induction of stomatal closure was studied in epidermal strips of three plant species (Vicia faba, Arabidopsis thaliana and Impatiens walleriana). The effect of H(2) S on stomatal movement was contrasted with leaf relative water content (RWC) measurements of whole plants subjected to water stress. In this work we report that exogenous H(2) S induces stomatal closure and this effect is impaired by the ATP-binding cassette (ABC) transporter inhibitor glibenclamide; scavenging H(2) S or inhibition of the enzyme responsible for endogenous H(2) S synthesis partially blocks ABA-dependent stomatal closure; and H(2) S treatment increases RWC and protects plants against drought stress. Our results indicate that H(2) S induces stomatal closure and participates in ABA-dependent signalling, possibly through the regulation of ABC transporters in guard cells.

Nitric oxide-induced phosphatidic acid accumulation: a role for phospholipases C and D in stomatal closure.

Stomatal closure is regulated by a complex network of signalling events involving numerous intermediates, among them nitric oxide (NO). Little is known about the signalling events occurring downstream of NO. Previous studies have shown that NO modulates cytosolic calcium concentration and the activation of plasma membrane ion channels. Here we provide evidence that supports the involvement of the lipid second messenger phosphatidic acid (PA) in NO signalling during stomatal closure. PA levels in Vicia faba epidermal peels increased upon NO treatment to maximum levels within 30 min, subsequently decreasing to control levels at 60 min. PA can be generated via phospholipase D (PLD) or via phospholipase C (PLC) in concerted action with diacylglycerol kinase (DGK). Our results showed that NO-induced PA is produced via the activation of both pathways. NO-induced stomatal closure was blocked either when PLC or PLD activity was inhibited. We have shown that PLC- and PLD-derived PA represents a downstream component of NO signalling cascade during stomatal closure.