1) In the presFent paper, the writers described the results of investigations on the starch accumulation in the area surrounding the spots on the leaves of rice plants affected by Cochliobolus miyabeanus. 2) After the inoculation, the starch disappeared in the area around the spots within 20 hours and then it began to accumulate in the area surrounding the zone where starch disappeared. The starch accumulation increased with the development of spotted area. After several days, the value of starch accumulation index, the ratio of area of starch accumulation to the spotted area, became constant, while the concentration of starch continued to increase. It seems that the effect of infection gives rise to some abnormal physiological changes in the host immediately after the invasion of parasite. 3) The area of starch accumulation was small in the early morning, but increased rapidly with the increase of insolation and remained constant until the sunset, while the concentration increased markedly in the evening. Under rainy or cloudy weather, starch decreased or disappeared around the spot. By keeping plants in a dark place for 24 hours, the starch disappeared. However, in some samples collected on the 10 th day after the inoculation, starch was still detectable. 4) In plants cultured with nutrient solution containing excess amount of manganese or decreased amount of nitrogen and also in Akiochi plants (rice plants physiologically declined in autumn), the starch accumulation was promoted. Generally, it seems that in the surrounding zone of spots revealed on plants grown under abnormal nutritional condition, starch accumulates greatly. 5) Judging from the results of our experiments, it may be suggested that the accumulated starch around the spotted area is assimilatory, and that the mechanism of this abnormal starch accumulation is partially based on the increased activity of starch assimilating enzymes, e. g. phosphorylase etc., in the surrounding area of spot.
The present paper deals with some ecological experiments of the oospores of Peronospora schleideni which may play an important role in the primary infection of downy mildew of onion. The causal fungus seems to be a physiological species of Peronospora schleideni Unger specialized in the size of oospores, the habit of their germination and the pathogenicity. The oospores are produced in the tissue of affected leaves under the air temperature above 17°C, and, it is likely that the formation is related to the age of the leaves. The germination of the oospore occurs in the water, in the soil and on the leaves of seedlings. The oospore germinates at 20°C-30°C, fails to germinate in the temperature range below 12°C and above 40°C.The germination is also accelerated by the pretreament with KMnO4 or low temperature. In conclusion, the oospores existing in the soil become a source of the primary infection against the seedlings in seedbed.
Orange fruit rind extract has a stimulative effect on the spore germination of Penicillium digitatum (Green mold of citrus fruit). The stimulative factor was readily extracted from the rind by water and absorbed by activated charcoal (active carbon). The component of the extract from the rind absorbed by charcoal was released by 60-80% acetone. The concentrated material from acetone extract had the stimulative effect on the spore germination of P. digitatum only when added with the filtrate (charcoal treated extract) or with very small amount of the phosphates. Thus, the phosphoric compounds were found to be the chemicals to activate the germination stimulant. It is suggested that the factor to stimulate the spore germination of P. digitatum seems to consist of two fractions, namely the one which is absorbed by charcoal and the other is not, or that the factor would be separated in two components by charcoal treatment and would recover by adding the phosphate compounds.
Drops of conidia suspension of Piricularia oryzae were mounted on the detached leaf pieces of rice plant, at the points pricked by capillary glass tube, and kept at 25-28°C for 24 hrs. in the moist chamber. These drops were then collected and centrifuged for 20minutes by 3000rpm. The supernatant of these drops showed strong inhibiting action against the germination of conidia of this fungus. The active principle, phytoalexin of Müller, is considered to be produced by the host plant as a result of interaction between rice plant and the blast fungus P. oyyzae. In the experiment to see the quantitative difference of phytoalexin prodcution between resistant or susceptible varieties of rice plant to blast fungus, it was shown that phytoalexin was more vigorously produced in the resistant varieties (Kameji and Norin No. 22)than in the susceptible ones (Asahi and Omachi).
The present paper deals with the influence of the treatment with narcotics, high temperature or of abnormal environmental conditions on the susceptibility of Cucurbita Pepo to Pythium ultimum. The change in the tissue respiration under the ether narcosis is also reported. The young seedlings of highly resistant variety “Amakuri” which was treated with ether, ethanol or chloroform, became susceptible to the disease. In the tissues of the seedling treated with ether, unlike those of nontreated, the Pythium hyhae were not checked their growth. The susceptibility of the seedling also increased by the treatment with high temperature. The respiration of the tissue of the host plant decreased when the seedling was treated with ether. This may suggest that the metabolic activity in the host cells is reduced by narcosis. From these results, it is recognized in the pumpkin seedlings that there exists a functional resistance of protoplasma of the host cells which can be easily abated by treating with narcotics and high temperature.
1. The so-called “septa” that were seen in the fresh conidia of Helminthosporium oryzae (Perfect stage: Cochliobolus miyabeanus) have entirely varished, when observed soon after germination. Each component cell of the conidia rounded up into a spherical body, linked together forming a necklacelike chain. Before germination, these spherical bodies fill completely the integument of conidia, and the area of contact of two bodies gives an optical appearance of cross wall. In this respect the present fungus resembles that of Cercospora beticola and Septoria apii-graveolentis, as reported by Frandsen (1955) and MacMillan et al. (1942) respectively. 2. Later, the chain of spherical bodies are in most cases severed into two fragments, generally at the central part. The bodies in a chain are tied to each other with slender connectors. 3. As germination advances, the spherieal bodies, one by one from the innermost in the chain, lose their contents and become vacant, apparently sending nutrients to the germ tube. 4. When conidia are cut or pressed, the spherical bodies are often separated from the chain. The disjunct single bodies, thus split out of the conidial integument, are still able to germinate. 5. Lining the chitinous, brown integument of the conidium a colorless, non-chitinous membrane is oberved. This inner membrane is dissoluble in chloral hydrate solution. 6. Shrivelled conidia, not only old viable ones but also those killed with alcohol, could expand in water or with expired air. The expansibility seems to be due to the nature of the inner membrane of the conidia.
1. In order to determine the distribution of calcium in the tissue, detached primary leaves of barley, inserted in water or inorganic salt solutions and inoculated with powdery mildew conidia, were immersed in oxalo-alcohol solution and then fixed with formalin-aceto-alcohol. After the green color of the leaves was removed in the fixative, the entire leaves were observed under microscope and the following facts were noticed. (1) In very young leaves every epidermal cell contains many small crystals of calcium oxalate, while in mature leaves crystals are scanty in most of the epidermal cells, except those in the apical part of the leaves. (2) Crystals of calcium oxalate are found mainly in the protoplasm along the side walls of epidermal cells. (3) Crystals are often observed abundantly on the outer surface of the guard cells and auxiliary cells and in the epidermal cells near the stomatal cells. No crystals are found on the surface of mesophyll cells facing the substomatal chamber. These findings suggest that calcium in the leaf tissue may move from mesophyll cells, passing through epidermal cells, to auxiliary cells and guard cells, from which it exudes out. (4) Mesophyll cells contain generally few crystals, while in strongly chlorotic or weakened leaves some of the mesophyll cells are filled with crystals. (5) In the epidermal cells inserted with haustoria, abundant crystals are found around the vesicle of the haustoria and on the inner surface of epidermal cells around the penetration pore made by the haustoria. In the weakened leaves crystals are scarce in these parts. 2. In view of the preceding observations, the following accounts may be stated, concerning the relation between calcium in the host cell and barley susceptibility to the powdery mildew. (1) Increased susceptibility of leaves inserted in calcium salt solutions, as reported in the previous paper, is probably due to the action of calcium protecting the surface of the host protoplasm in contact with the haustorium. Susceptibility reduction by potassium, soda, ammonium and lithium salts seems to be related to thier action to drive calcium away from the protoplasm around the haustorium, making development and function of the haustorium inadequate. (2) The fact that very young leaves are highly susceptible on their whole surfaces and they become resistant except the apical part and the auxiliary cells as they grow, may be interpreted by the even and uneven calcium distribution in the epidermis, respectively of the young leaves and older ones. (3) High susceptibility of auxiliary cells seems to be related to abundant quantity of calcium, translocated from the surrounding epidermal cells.
The writer already reported that large quantity of free auxin was contained in the gall tissue of the stem and leaf of Youngia japonica infected with Protomyces inouyei, though the determination of the hormonal substance was not yet done. This article deals with the results of experimental studies on the production of auxin and its identification regarding 3 species of Protomyces fungi. Four kinds of solvents such as ether, chloroform, ethyl-alcohol and water, were used for obtaining extract from the gall formed by the infection of Protomyces inouyei. With these extracts Went's Avena-test was carried out. The ether solvent was found to be better for the purpose of extraction than others, as shown in Table 1. When Protomyces was cultured in Czapek's solution or in the same one containing 1g of L-tryptophane in substitution for KNO3 as a N source, the filtrate from the latter medium alone was ascertained by the Avena-test to contain a considerable quantity of auxin. The material fungi were cultured in Czapek's medium containing tryptophane, at 26°C. for 30 days, and their filtrates were concentrated to one half. The filtrates were then extracted with trebled volume of ether, and the dry yellowish extract was obtained from P. pachydermus and the yellowish brown one from other two fungi. The yellowish brown extract showed typical IAA color reaction with Gordon and Weber's reagent, while the yellowish one never showed the reaction. For analysing the extract one-dimentional paperchromatography was applied under the condition as described in the foot-note of Table 4. The reddish pink spots at Rf 0.54 and 0.55 developed by isopropanol-ammonia-water solvent mixture and also the spots at 0.79 and 0.80 developed by ethanol solvent were all identified as IAA, by comparing with the Rf value shown by synthetic IAA as the control. The IAA spots appeared was found to be smaller in area than other spots. Figure 1 shows the data of analysis of these extracts by the paperchromatographic bioassay method. The results also clearly show the presence of IAA similarly to the experimental data mentioned above. It seems to the writer that Protomyces may produce tryptamine and indoleacetaldehyde as the intermediates in the metabolic process of tryptophane, because some similar spots to the very intermediates in respect of color reaction and Rf value were shown in the paperchromatogram. Protomyces fungi were proved to have lower activity in IAA metabolic production from tryptophane than certain various fungi belonging to Ustilago, Taphrina, Exobasidium, Fusarium etc. as far as the writer's experiments concerned.
A new antifungal antibiotic was found from the culture filtrate of a bacterium, which had been isolated from the spot of Helminthosporium blight of rice plant. The bacterium is Bacillus funicularis Cluyver et Van Niel, and the antibiotic produced by the bacterium inhibits the germination of the conidia of Cochliobolus miyabeanus. This substance is named “Funicularin” temporalily. Bouillon medium is one of the most suitable media for the production of the antibiotic and the optimum conditions for the production are 4 days culture at 25-30°C. in the medium with the initial pH 6-7. The method of extraction and purification of this antibiotic is shown in Fig. 1. When B. funicularis was successively cultured in the medium containig Funicularin, the production of the substance markedly increases. The susceptibility of rice seedlings to Helminthosporium blight appears to be lowered by the immersion of roots in the culture filtrate, the index of the disease spot enlargement being considerably smaller than that of the nontreated.