Inducible silica incrusts in cell walls of Vitis leaves

Epidermal cells of Vitis cvs attacked by powdery mildew or damaged mechanically exhibited silica deposits in the walls of the attacked and surrounding cells. Entire or parts of cell walls were vitrified to such an extent that pure, mechanically resistant silica skeletons remained after a treatment with conc. H2S04 + H2O2 at 400 °C and washing with conc. HCl. They consisted of groups of 1-20 cells of the upper epidermis with adhering parts of the corresponding palisade cells or of the lower epidermis (including stomatal cells) with adhering spongy parenchyma. Not only cell walls but also wrinkles of the upper epidermis, defense papillae and fungal haustoria were silicified. Silica accumulations were greater in resistant than in susceptible cultivars

Performance of P-P and P-U intensity probes using Scan & Paint

This paper aims to clarify the principal advantages and disadvantages of using sound intensity probes which implement different measurement principles: p-p probes versus p-u probes or Microflowns. A novel measurement technique based on scanning principles called “Scan & Paint” had been chosen to evaluate their performanc

Comparison of inverse methods and particle velocity based techniques for transfer path analysis

International audienceDirect sound field visualization is not always the best way to assess complex noise problems. Maps of sound pressure, particle velocity or intensity in the vicinity of a source might not be directly related to the pressure contribution for a given position. Transfer path analysis has been implemented for many years to evaluate this case scenario, which requires using information of the environment and the sound source. Inverse methods commonly require a detailed geometric description of the problem along with sound pressure measurements. On the other hand, particle velocity methods rely on measuring the reciprocal transfer path and the velocity close to the sources. This paper presents the theoretical bases of the two principles and compares the advantages and disadvantages of the two methods applied to real industrial applications

The role of callose deposits during infection of two downy mildew-tolerant and two-susceptible Vitis cultivars

Semithin sections of leaves from four cultivars were analysed for callose deposition after infection with Plasmopara viticola. Two of these cultivars are tolerant to this pathogen in the field (Orion, Phoenix), while the other two are susceptible (Kerner, Riesling). Callose was not detectable during the first 5 days after experimental inoculation. During late stages of the infection cycle however, callose deposits could be found in tolerant as well as in susceptible grapes. During the fungal infection of tolerant plants hyphal development stops 3 to 4 days post infection indicating that mechanisms other than callose deposition are the main factors of tolerance

The role of hairs on the wettability of grapevine (Vitis spp.) leaves

Hairs represent an important physico-chemical factor on abaxial leaf surfaces of grapevine and can influence the wettability of leaves. This was demonstrated by scanning electron micrographs and monitored with a new method using a torsion balance. Forces necessary to remove water droplets of distinct size from leaves were lower in case of pubescent (0,2-0,4 mN) compared to non-pubescent vine leaves (0,4-1,2 mN). Depending on the number of hairs and their surface structure the deposition and distribution of water droplets originating from dew and rain can be prevented due to weak adhesion. Thus, surface features enabling water droplets to pearl off may reduce the probability of infection by fungal spores

Resurgent landlordism in a student city: urban dynamics of private rental growth

Many countries have seen a remarkable revival of private-rental housing markets in recent years. Academic literature so far has focused on theorizing the political-economic drivers of reinvestment in the tenure or on charting aggregate trends. This paper adds to these literatures in several ways based on a fine-grained analysis of housing market transformations in Groningen, a medium-sized university city in The Netherlands. First, we reveal the variegated trajectories through which private-rental growth materializes on the ground and untangle the role of different types of landlords. While small-scale private landlords remain dominant, we find a clear and important trend toward property concentration. Second, we highlight variations in spatial investment strategies across landlord types. Third, we reveal how contemporary dynamics of increased landlordism play out in a medium-sized city, embedded in a context of national private rental resurgence and local housing market pressures of a growing student city