Masao Fukutomi

Histochemical changes of the epidermal cell wall of barley leaves infected by erysiphe graminis hordei

Chemical changes in the epidermal cell wall of barley leaves attacked byErysiphe graminis hordei were investigated by means of histochemical techniques and electron microscope. A very narrow area in the cuticle which was not stained by Sudan III was detected around the penetration point of this fungus. This is to indicate that the cuticle was changed either enzymatically or mechanically at the penetration point. According to the procedures using zinc-chloriodide and Schiffs reagent, it was obvious that the area of cellulose layer corresponding to the halo changed chemically, which suggested that the halo was attributable to the degeneration of the cellulose layer by the fungal enzyme, probably the cellulase. Electron micrographs showed that the cell wall around the penetration point was prominently electron dense and indicated an enzymic degeneration of the host cell wall.

Effect of the host-specific toxin from Alternaria kikuchiana on the ultrastructure of plasma membranes of cells in leaves of Japanese pear☆

Abstract Alternaria kikuchiana , causal fungus of the black spot disease of Japanese pear, produces a host-specific toxin (AK-toxin) which caused immediate changes in permeability of susceptible leaf tissues. The first obvious change in ultrastructure of susceptible cells in the vascular bundle sheath and in the mesophyll was an invagination of plasma membranes, evident by 1 h after exposure. There were still more invaginated plasma membranes by 3 and 6 h after exposure, when a high percentage of susceptible cells showed such changes. There was no obvious effect of toxin on cellular organelles of susceptible leaves after 1, 3 and 6 h of treatment; the organelles appeared to be normal even in cells with invagination of plasma membranes. After 10 h of toxin exposure, leaf cells were necrotic, but the cellular membrane systems still maintained much of their original structures. The degeneration that was evident may have been from secondary effects of toxin. The spaces between susceptible cell walls and invaginated membranes contained many lomasome-like vesicles, membrane fragments and darkly stained materials. Rolands staining method indicated that the vesicles were fragments from invaginated plasma membranes. However, ultrastructural changes in unit membranes of invaginated plasma membranes were not observed. Cells of resistant leaf tissues were not affected by toxin. These results are compatible with the hypothesis that the plasma membrane is the site of an initial effect of AK-toxin.

An electron microscopic observation of conidium and hypha of Erysiphe graminis hordei

The fine structure of conidia and hyphae ofErysiphe graminis hordei, attacking leaves of barley, were investigated. The cell walls of conidia and hyphae were relatively thin and consisted of two layers, the inner and outer layers. The surface of conidia was not smooth and the thickness of cell walls was irregular. A nucleus, mitochondria, endoplasmic reticula and vacuoles in plasma were identified. The vacuoles in conidia were tightly packed with fine granules. Such granules in vacuoles, however, were not observed in hyphal cells. A lamellar structure was located in conidia, but not in hyphal cells. This structure may be specific in conidia of this fungus, but its function is not yet known. Many glycogen granules were observed in endoplasm of conidia, which were scattered or congregated in groups. In hyphae, however, they were extremely few. Hyphal septa were connected directly with the inner layer of cell walls. These had simple septal pore. The Woronin bodies were detected in the endoplasm in the vicinity of hyphal septa.

Fine structure of antheridia and oogonia of Phytophthora macrospora, the downy mildew fungus of rice plants

In the present paper fine structure of antheridium and oogonium ofPhytophthora macrospora (Sacc.)S. Ito etI. Tanaka, the downy mildew fungus of rice plants was discussed. Before the fertilization some nuclei and a large number of mitochondria were scattered in the cytoplasm of the antheridium. Many lipid granules were observed in the peripheral region, but vacuoles did not appear at this stage of antheridium. Many mitochondria were associated in the neighborhood of the fertilization pore. The wall at the pore was very thin, but the wall surrounding the pore was slightly swollen towards the inside. In the oogonium, many nuclei, mitochondria and cytoplasmic matrix were observed at the peripheral part. A large number of lipid granules was found in the oogonium, but they were more numerous in the peripheral region. The vacuoles developed as the oogonium matured. They were enveloped by tonoplast and contained vacuolar matrix. Many electron dense granules were in contact with the tonoplast or free in the vacuoles, and they were larger in the central part. As stated above, wall at the fertilization pore was thin. However, the oogonial wall surrounding the pore swelled protruding into the oogonium. An electron-dense layer was recognized between the antheridial and oogonial wall, and the walls of both the organs were closely in contact with each other.

An observation on fine structure of conidia of sphaerotheca pannosa (wallr.) lév. attacking leaves of roses

Fine structures of conidia ofSphaerotheca pannosa, the causal fungus of powdery mildew of rose plants were investigated. The cell wall of conidia was relatively thin and consisted of two layers. Nuclei, mitochondria, endoplasmic reticula and vacuoles were identified in the conidia, and there were many unknown vesicles just inside the plasma membrane. Usually the conidia were uninucleate, but before the germination the nucleus divided into two. Vacuole held a number of osmiophilic globules which were located along the tonoplast, and in large magnifications they appeared as aggregation of small electron-transparent globules when fixed with KMnO4 solution. In a germ tube one large mitochondrion and many endoplasmic reticula were found.

How much cost should reciprocators pay in order to distinguish the opponent's cooperation from the opponent's defection?

Reciprocity is a potential mechanism that encourages the evolution of cooperation. We consider the case where reciprocators’ cognitive ability of distinguishing the opponents cooperation from the opponents defection imposes a recognition cost. While it is natural to consider how recognition accuracy depends upon the magnitude of the recognition cost, it is rather unclear which amounts of the recognition cost paid by the reciprocator are most likely to evolve. By using the evolutionarily stable strategy analysis, we herein tackle this problem and show that the condition under which reciprocators can resist the invasion of unconditional defectors is most relaxed when they have perfect perception. We further consider a game with three strategies played by unconditional defectors and two types of heterogeneous reciprocators with different perceptual abilities. Our analysis shows that only when execution error rates are large enough, it is possible for reciprocators with lower perceptual ability to resist the invasion of both the unconditional defectors and reciprocators with higher perceptual abilities. These findings advance our understanding of the evolution of perception and its eminent role in the evolution of cooperative behavior.