Can Biostimulants Increase Resilience of Hydroponically-Grown Tomato to Combined Water and Nutrient Stress?

In the current experiment, tomato (Solanum lycopersicum cv. Nostymi F1) was cultivated in an open hydroponic system under optimal or stress conditions caused by reducing the supply of nutrient solution by 35–40% and treated with biostimulants to test whether their application can increase crop resilience to combined shortage of nutrients and water. The four different biostimulant treatments were: (i) no biostimulant application, (ii) treatment with the protein-based biostimulants COUPÉ REGENERACIÓN Plus and PROCUAJE RADICULAR provided by EDYPRO, (iii) treatment with a novel biostimulant based on strigolactones, provided by STRIGOLAB and (iv) treatment with MAXICROP, a commercial product consisting of seaweed extracts. Combined stress significantly reduced NO3−, P, and K in the root zone of tomato plants. However, the application of the strigolactone-based biostimulant to stressed plants maintained NO3− in the root zone to similar levels with non-stressed plants during the first and third months of cultivation. The biostimulants did not increase the vegetative plant biomass at 70 and 120 days after transplanting (DAT). The strigolactone-based biostimulant increased early leaf area development (70 DAT) and early fruit production compared to untreated plants but had no effect on total tomato yield (120 DAT). Maxicrop also increased early fruit yield, while Edypro decreased early and total yield compared to the control plants, an effect ascribed to overdosing, as the application rate was that suggested for soil-grown crops, while the plants were cultivated on an inert substrate. Strigolactone-based biostimulant and Maxicrop could be further studied by testing multiple applications during the cropping period.

Influence of the seeding rate and substrates on the cultivation of oil radish microgreens

In 2 series of experiments, the influence of population density and substrates on the growth and development of microgreens in oil radish was studied. In the optimum zone were crops with a density of 5 and 7 g of seeds per container with an area of 144 cm2. At higher seeding densities, the plants lagged significantly behind in growth. Their average height was 1.5 times less, and the average mass of microgreens per 1 g of sown seeds decreased 2-2.5 times. A new inert substrate, foam glass, was tested. Possessing high porosity, it provided an optimal water-air regime for plants. Comparison of growing microgreens on soil and foam glass showed the advantage of foam glass — the mass of plants on it was slightly larger. Despite the optimal air-water regime created by the foamglass, the diameter of the stones of 1.5-3 cm turned out to be excessively large and created inconvenience for growing microgreens.

Influence of the seeding rate and substrates on the cultivation of oil radish microgreens

In 2 series of experiments, the influence of population density and substrates on the growth and development of microgreens in oil radish was studied. In the optimum zone were crops with a density of 5 and 7 g of seeds per container with an area of 144 cm2. At higher seeding densities, the plants lagged significantly behind in growth. Their average height was 1.5 times less, and the average mass of microgreens per 1 g of sown seeds decreased 2-2.5 times. A new inert substrate, foam glass, was tested. Possessing high porosity, it provided an optimal water-air regime for plants. Comparison of growing microgreens on soil and foam glass showed the advantage of foam glass — the mass of plants on it was slightly larger. Despite the optimal air-water regime created by the foam glass, the diameter of the stones of 1.5-3 cm turned out to be excessively large and created inconvenience for growing microgreens.

Novel Method for Surface Tension Measurement: the Drop-Bounce Method

The surface tension of liquids at high temperatures is generally measured with the well-established oscillating drop method in a contactless environment. However, technical difficulties in surface tension measurements make it hard to apply the oscillating drop method to the aerodynamic levitation (ADL) system, the most reliable levitation technique for liquids with low electrical conductivity. In this study, we developed a novel drop–bounce method that can be used within an ADL system to measure the surface tension of liquids. A levitated molten sample was first dropped onto an inert substrate through a splittable nozzle. The rebounded sample’s oscillatory motion behaved as it would under microgravity conditions during its free-fall, and oscillations were obtained only in the l=2, m=0 mode. Fourier transformation of the oscillation pattern provided resonant frequency of the l=2, m=0 mode and enabled the calculation of the surface tension of the sample under knowledge of its mass. Furthermore, a short experimental duration of less than 50 ms significantly reduced the possibility of surface evaporation in the sample. Our measured surface tension data from 1354 K to 1827 K for gold exhibited a standard deviation of 13.4 mJ/m2 and were consistent with the data published by Egry et al. under microgravity conditions, with a maximum deviation of 1.5% between the two fitted linear equations.

Foliar Spray Application of Chlorella vulgaris Extract: Effect on the Growth of Lettuce Seedlings

Lettuce seedlings often require the use of fertilizers for their cultivation management to achieve appropriate yield. However, for eco-sustainable chemical-fertilizers-free agronomy, the implementation of totally organic farming often cannot support lettuce productivity, therefore new natural biostimulants able to increase lettuce yield could be considered of great interest. In this preliminary work, the foliar spray application of a Chlorella vulgaris extract in lettuce seedlings was investigated in order to achieve better yield performance. Its biostimulant effect was evaluated by monitoring the morphobiometric parameters, chlorophylls, carotenoids, total protein contents, and several enzymatic activities involved in primary and secondary metabolisms of the plant. The experimental trials were carried out by growing lettuce seedlings on inert substrate (pumice) with a 16 h photoperiod for 21 days. The treatment consisted of three consecutive applications by foliar spraying using a concentration of the C. vulgaris extract, corresponding to 1 mg Corg L−1, which were performed one week apart. The results showed that the C. vulgaris extract positively influenced the growth of lettuce seedlings, by increasing the fresh and dry weights, chlorophylls, carotenoids, protein content, and ashes at shoot level. From a biochemical point of view, primary and secondary metabolisms of shoots, in particular nitrogen metabolism, were positively influenced. At the root level, the extract increased dry matter, proteins, and ash content.

Surface-bound reactive oxygen species generating nanozymes for selective antibacterial action

Acting by producing reactive oxygen species (ROS) in situ, nanozymes are promising as antimicrobials. ROS’ intrinsic inability to distinguish bacteria from mammalian cells, however, deprives nanozymes of the selectivity necessary for an ideal antimicrobial. Here we report that nanozymes that generate surface-bound ROS selectively kill bacteria over mammalian cells. This result is robust across three distinct nanozymes that universally generate surface-bound ROS, with an oxidase-like silver-palladium bimetallic alloy nanocage, AgPd0.38, being the lead model. The selectivity is attributable to both the surface-bound nature of ROS these nanozymes generate and an unexpected antidote role of endocytosis. Though surface-bound, the ROS on AgPd0.38 efficiently eliminated antibiotic-resistant bacteria and effectively delayed the onset of bacterial resistance emergence. When used as coating additives, AgPd0.38 enabled an inert substrate to inhibit biofilm formation and suppress infection-related immune responses in mouse models. This work opens an avenue toward biocompatible nanozymes and may have implication in our fight against antimicrobial resistance.

Phenotypic and genotypic virulence features of staphylococcal strains isolated from difficult-to-treat skin and soft tissue infections

Chronic infections represent an important burden on the healthcare system and have a significant impact on the patients’ quality of life. While Staphylococcus spp. are commensal bacteria, they can become pathogenic, leading to various types of infections. In this study we aimed to characterize the virulence profiles of staphylococcal strains involved in difficult-to-treat skin and soft tissue infections, from both phenotypic and genotypic points of view. Phenotypic ability of the strains to secrete soluble virulence factors was assessed by a culturing dependent assay and their capacity to develop biofilms on inert substrate was screened by an adapted crystal violet microtiter method. We also tested the presence of several virulence genes by PCR. Most of the studied strains were isolated from purulent secretions of acne lesions and frequently secreted two or three soluble virulence factors. Most frequently secreted soluble virulence factors were caseinase (89%), lipase (71%) and lecithinase (67%). Almost half of the strains produced a well-represented biofilm. The molecular characterization showed the presence of the genes cna, hlg, clfA, and clfB. Staphylococcal strains that produce difficult-to-treat skin and soft tissue infections seem to be characterized by an enhanced ability to produce different soluble virulence factors and to develop biofilms in vitro. Further studies need to be developed in other Staphylococcus spp. infections in order to confirm this hypothesis.