No description available.

No description available.

Pseudomanas syringae pv. tomato was used to investigate the role of cell wall alteration in early basal defences against microbial challenge in Arabidopsis thaliana. Wild - type DC3000 and the hrpA mutant, deficient in a structural component of the type three secretion system and consequently non-pathogenic, were used for a comparison of pathogenic and non-pathogenic interactions. A comprehensive population study was undertaken to pinpoint the crucial time, post inoculation, when bacterial populations grew in planta .The results indicated that key differences between mutant and wild - type populations occurred between 6 to 8 h post inoculation and that the hrpA mutant bacteria failed to maintain their rate of multiplication, forming a static population from 6 h after inoculation until up to twelve days after inoculation. Electron microscopy, including immunocytochemi~1and histochemical approaches were used to define changes in the cell wall between 2 and 8 h after inoculation and results indicated that similar swelling of the pectin matrix, cellulose and callose deposition could be identified in both the wild - type and mutant bacterial interactions 4 to 8 h after inoculation. Trans-vacuolar movement of arabinogalactan proteins was identified, followed by their subsequent deposition in the apoplast. Further studies using extracted intercellular wash fluid measured levels of reducing sugars, protein, and ascorbate 2 to 8 h after inoculation. Methods used included colorimetric assays and SOS - PAGE protein separation Importantly, ascorbate redox ratios differed between wild-type and mutant bacteria implicating H20 2 production as a key defence response early in the interaction. Finally confocal microscopy combined with a fluorescent probe was used to localize H20 2 to the mesophyll walls and chloroplasts in tissue challenged with the hrpA mutant. The restriction of hrp mutant bacteria appeared not to be due to any generation of antibacterial compounds, but the physical entrapment of bacterial cells in a proteinaceous and carbohydrate containing matrix.

No description available.

No description available.

Over the past few decades a significant body of work has been done to understand the ecological and health risks of synthetic pyrethroid pesticides (SPs). Recently the use of nano-encapsulated SPs has been proposed. As nanoparticles can behave very differently from dissolved chemicals, it is possible that the effects, fate and uptake of these nano-formulated pesticides could be very different from the conventional SPs. This study therefore investigated the effects of nano-encapsulation on the fate and uptake of bifenthrin, a widely used third generation synthetic pyrethroid, in soil systems. Studies were performed, using Organisation for Economic Co-operation and Development (OECD) Guidelines and similar methods, on five soil types with different properties (total organic carbon and texture) to determine dissipation half-lives in soil, soil-water partition coefficients and uptake and depuration in the earthworm Eisenia fetida using analytical grade bifenthrin, a conventional bifenthrin formulation (Capture LFR) and two nano-formulations. Persistence, sorption and uptake behavior of all the study materials varied across soil types. Generally, the persistence, sorption and uptake of bifenthrin in the conventional formulation were similar to the behavior of the non-formulated active ingredient. However, nanoencapsulation significantly affected the behavior of the bifenthrin. Results for the two nanoformulations were similar to each other but these showed enhanced persistence, decreased sorption and increased rates of uptake and depuration in the earthworms compared to the analytical grade material and the conventional formulation. We therefore anticipate that the distribution and impacts of the nanoformulation in natural soil systems will be different from currently used formulations. The observed differences in persistence and sorption behavior are possibly due to the polymer capsule ‘protecting’ the active ingredient from microbes and soil binding sites. Differences in uptake might be explained by differences in distribution of the bifenthrin within the organism (i.e., the nanoformulation is accummulating in the earthworm gut while bifenthrin in the conventional and non-formulated treatments is being internalised).

No description available.

No description available.

No description available.

No description available.