Chitin localisation and retention in the exit tubes of the holocarpic oomycete Anisolpidium rosenvingei

The finding of the enigmatic pathogen Anisolpidium rosenvingei in the filamentous brown macroalga Pylaiella littoralis presented a unique opportunity to histochemically study the distribution of chitin in this little-known pathogen using FUNGALASE™-F, a fluorescein-labelled chitinase. Chitin was found localised to the exit tube of this pathogen, which infects exclusively reproductive cells of its host. The cytological and phylogenetic implications of this finding are discussed. This paper also reports the first record of this pathogen in the United Kingdom, on the west coast of Scotland.

Non-Uniform Velocity Distributions in Bipolar Plate PEM Electrolysis Cell

The rate of hydrogen production within the PEM electrolysis cell is influenced by the temperature, the velocity distributions, and the pressure distribution. In order to design and use a PEM electrolyzer cell effectively, analytical and/or numerical models for the device are necessary so that the system may be optimized. Numerical simulations of three-dimensional water flow were performed for the purpose of examining pressure and velocity distributions in the bipolar plate of a simplified PEM electrolysis cell. The flow range in the present study is assumed to be hydrodynamically stable and steady. The numerical results show that the pressure drops diagonally from the inlet tube to the exit tube. The velocity distribution is very non-uniform in the channels. A minimum of the peak values of mainstream velocity component in the channels develops in the middle of the plate. The maximum of these peak values appears in the channel near the exit tube. The lines along which the mainstream velocity component is a peak in the channel almost overlay with each other, except that a minor difference can be noticed in the channel near the exit tube.

A new and unusual species of Haptoglossa

Haptoglossa elegans, isolated from soil and organic debris in New Zealand forests, is described as new. This species has no motile stage. The protoplasm inside the thallus cleaves into spherical cysts that are expelled en masse to the exterior through a solitary exit tube. Cysts are two sizes. Small cysts produce elongate, unbranched, tapering gun cells. Large cysts produce identical but larger cells; alternatively large cysts produce Y-shaped gun cells. Haptoglossa elegans is a common and aggressive parasite of bdelloid rotifers but unlike all other species of Haptoglossa, it does not attack nematodes.

Observation of Flow in a Ring Inlet Chamber

We present the results of visualization and quantitative measurements of the flow in a simplified model ring chamber of the type used in axial-flow turbomachinery (see Fig. 1) to distribute flow entering a machine radially to the blading. The observations reveal that above a critical Reynolds number the flow swirls circumferentially around the ring chamber. The device then performs much like a vortex valve, a strong vortex being created in the exit tube beyond the center body. It is shown that the pressure loss in this case can be calculated fairly well using an analysis similar to that of Binnie and Hookings [1]. The exit-tube vortex is also responsible for the occurrence of a piercing whistling sound the frequency of which can be estimated using Vonnegut’s [2] theory for the vortex whistle. Observations are also presented for the symmetric flow situation which occurs at subcritical Reynolds numbers and for the case where swirl in the ring chamber is prevented by a baffle.

The ultrastructure of Polymyxa betae zoospore exit-tube differentiation

Zoosporangia of Polymyxa betae Keskin are plurilobate and develop cross walls. During ripening they show dark zones at the contact points with the host cell wall at the light microscope level. With the electron microscope these zones appear to correspond to single uninucleate compartments separated by a wall from the zoosporangium itself. These compartments give rise to exit tubes while the zoosporangial contents differentiate into zoospores. At the beginning of exit-tube formation, the thallus wall in contact with the host cell wall becomes thinner and softened. At the same time, thallus cytoplasm shows membrane-bound vesicles, the endoplasmic reticulum increases, and vacuoles enlarge. Vesicles are concentrated in the area of exit-tube formation and this suggests that they are involved both in host and thallus wall lysis. Wall microfibril profiles indicate that at this point mechanical forces have also been applied. A papilla, surrounded by a wall which appears to be continuous with the inner layer of the zoosporangium wall, is formed. The papilla elongates and becomes tubular, forming the zoospore exit tube. The same lytic and mechanical sequence described for thallus and host cell wall demolition at the site of exit-tube emission, also takes place in the demolition of zoosporangial cross walls.

A new species of Olpidium parasitic on cucumber roots

Olpidium cucurbitacearum sp. n., from roots of Cucumis sativus L. var. Windermoor Wonder, is described. The fungus is distinguished from other Olpidium spp. by its zoospore and resting spore morphology and its restriction to cucurbitaceous hosts, and from species of Pleotrachelus Zopf by the typical occurrence of a single exit tube per sporangium.

The ultrastructure of Olpidium brassicae. I. Formation of sporangia

The ultrastructure of Olpidium brassicae was observed in epidermal cells of lettuce roots from 8 h after inoculation with zoospores until the thalli matured, at 72 h. In early stages of growth the thallus is completely surrounded by the host cytoplasm and separated from it by the thallus ectoplast. A thallus wall begins to form after 36 h and consists of three layers. The thallus contains the usual organelles, a nucleus (many nuclei after about 24 h), mitochondria, ribosomes, and lipid globules. Membrane-bounded structures, the multivesicular bodies, occur throughout the life cycle and are thought to be involved in synthesis of glycogen and lipid, and at a later stage in cleavage of the thallus protoplasm into zoospore protoplasts. One kinetosome in each zoospore protoplast produces a flagellum that is pushed into the cleavage vacuole. An exit tube originates from a bulge in the thallus wall and is closed by an elaborate plug.

OÖSPORE GERMINATION IN ALBUGO CANDIDA

In addition to the well-known sessile vesicular zoosporangial type of oöspore germination in Albugo candida (Lév.) Kuntze, a second type is described. This consists of an exit tube one to two and a half times the length of the diameter of the oöspore and about one quarter of its width, at the end of which the vesicular zoosporangium is produced. Best results were secured by soaking the oöspores for 7 to 10 days in water at 10° to 12 °C and then changing to fresh water. The oöspore material came from hypertrophied inflorescences of rape (Brassica napus L. var. annua Koch).