Drop impact dynamics on the hydrophobic leaf surface of an aquatic plant: a case study of Pistia stratiotes.

Pistia stratiotes is an aquatic plant with a complex structure that allows it to stay afloat. It grows quickly, and in large numbers becomes an undesirable plant as an invasive species. Describing the dynamics of a water drop splash on P. stratiotes leaves can contribute to increasing knowledge of its behavior and finding alternative methods for eradicating it or using it for the benefit of the environment. The non-wettable surface of P. stratiotes presents a complex structure-simple uniseriate trichomes and also ridges and veins. We analyzed the drop impact on a leaf placed on the water surface and recorded it by high-speed cameras. Based on the recordings, quantitative and qualitative analyses were performed. After impacting the leaf, the water drop spread until it reached its maximum surface area accompanied by the ejection of early droplets in the initial stage. Thereafter, three scenarios of water behavior were observed: (i) drop receding and stabilization; (ii) drop receding and ejection of late droplets formed in the later stage as an effect of elastic deformation of the leaf; and (iii) drop breaking apart and ejection of late droplets. The results indicated that the increasing kinetic energy of the impacting drops expressed by the Weber number and the complex leaf surface have an effect on the course of the splash. The simple uniseriate trichomes of the P. stratiotes leaf and the high energy of the falling drops were responsible for the formation and characteristics of the early droplets. The presence of ridges and veins and the leaf's mechanical response had an impact on the occurrence of late droplets.

The Effect of Silver Nanoparticles on the Digestive System, Gonad Morphology, and Physiology of Butterfly Splitfin (Ameca splendens).

The aim of this study was to determine the effects of silver nanoparticles (AgNPs) on the morphology and enzymatic activity of butterfly splitfin (Ameca splendens). Individuals of both sexes, aged about five months, were exposed to AgNPs at concentrations of 0 (control group), 0.01, 0.1, and 1.0 mg/dm3 for 42 days. On the last day of the experiment, the fish were euthanized, subjected to standard histological processing (anterior intestine, liver, and gonads), and analysed for digestive enzyme activity in the anterior intestine and oxidative stress markers in the liver. Fish in the AgNP 0.01 and 0.1 groups had the lowest anterior intestinal fold and enterocyte height. However, there were no statistically significant changes in the digestive enzyme activity in the anterior intestine. Analysis of enzymatic activity in the liver showed an increase in superoxide dismutase activity in fish in the AgNP 0.1 group. Histological analyses showed that AgNPs inhibited meiotic divisions at prophase I in a non-linear manner in ovaries and testes. In the AgNP 0.1 and 1.0 groups, the area occupied by spermatocytes was lower compared to the other groups. These results indicate that exposure to AgNPs may lead to disturbances in morphology and enzymatic activity in the liver and intestine and may lead to disruption of reproduction in populations.

The Effects of Seven-Day Exposure to Silver Nanoparticles on Fertility and Homeostasis of Zebrafish (Danio rerio).

Silver nanoparticles (AgNPs) are found in open waters, but the effect of their low concentrations on an organism's homeostasis is not fully understood. The aim of the study was to determine the short-term exposure effects of AgNPs coated by PvP (polyvinylpyrrolidone) on the homeostasis of livers and gonads in zebrafish. Sexually mature zebrafish were exposed for seven days to silver ions (0.01 mg/dm3) or AgNPs (0.01; 0.05; 0.1; 0.5; 1.0 mg/dm3). On the last day, the liver, testes, and ovaries were subjected to a histology analysis. In the liver, we analyzed the expression of the cat, gpx1a, gsr, sod1, and cyp1a genes. On the last day of the experiment, the lowest survival rate was found in the AgNPs 0.05 mg/dm3 group. The histological analysis showed that AgNPs and silver ions cause an increase in the area of hepatocytes. The highest proliferation index of hepatocytes was found in the AgNP 0.05 mg/dm3 group. Furthermore, AgNPs were found to interfere with spermatogenesis and oogonesis as well as reduce the expression levels of the cat, gpx1a, and sod1 genes in the liver compared with the control group. Based on the results, it can be concluded that exposure to AgNPs causes cytotoxic changes in zebrafish, activates the immune system, negatively affects the process of meiosis in the gonads, and generates oxidative stress.

Respiratory Burst Oxidase Homologs RBOHD and RBOHF as Key Modulating Components of Response in Turnip Mosaic Virus-Arabidopsis thaliana (L.) Heyhn System.

Turnip mosaic virus (TuMV) is one of the most important plant viruses worldwide. It has a very wide host range infecting at least 318 species in over 43 families, such as Brassicaceae, Fabaceae, Asteraceae, or Chenopodiaceae from dicotyledons. Plant NADPH oxidases, the respiratory burst oxidase homologues (RBOHs), are a major source of reactive oxygen species (ROS) during plant-microbe interactions. The functions of RBOHs in different plant-pathogen interactions have been analyzed using knockout mutants, but little focus has been given to plant-virus responses. Therefore, in this work we tested the response after mechanical inoculation with TuMV in ArabidopsisrbohD and rbohF transposon knockout mutants and analyzed ultrastructural changes after TuMV inoculation. The development of the TuMV infection cycle was promoted in rbohD plants, suggesting that RbohD plays a role in the Arabidopsis resistance response to TuMV. rbohF and rbohD/F mutants display less TuMV accumulation and a lack of virus cytoplasmic inclusions were observed; these observations suggest that RbohF promotes viral replication and increases susceptibility to TuMV. rbohD/F displayed a reduction in H2O2 but enhanced resistance similarly to rbohF. This dominant effect of the rbohF mutation could indicate that RbohF acts as a susceptibility factor. Induction of hydrogen peroxide by TuMV was partially compromised in rbohD mutants whereas it was almost completely abolished in rbohD/F, indicating that these oxidases are responsible for most of the ROS produced in this interaction. The pattern of in situ H2O2 deposition after infection of the more resistant rbohF and rbohD/F genotypes suggests a putative role of these species on systemic signal transport. The ultrastructural localization and quantification of pathogenesis-related protein 1 (PR1) indicate that ROS produced by these oxidases also influence PR1 distribution in the TuMV-A.thaliana pathosystem. Our results revealed the highest activation of PR1 in rbohD and Col-0. Thus, our findings indicate a correlation between PR1 accumulation and susceptibility to TuMV. The specific localization of PR1 in the most resistant genotypes after TuMV inoculation may indicate a connection of PR1 induction with susceptibility, which may be characteristic for this pathosystem. Our results clearly indicate the importance of NADPH oxidases RbohD and RbohF in the regulation of the TuMV infection cycle in Arabidopsis. These findings may help provide a better understanding of the mechanisms modulating A.thaliana-TuMV interactions.