In the previous paper8, 9), it was shown that the excitement of metabolism in blight-resistant potato tuber tissue, when infected by P. infestans, is inhibited by the pre-infectional ethanol narcosis, resulting in a reduction of the plant's resistance to P. infestans. Further studies on this point are reported in the present paper. The cut surface of halves, or slices of tuber 0.45mm thick were treated with 10% ethanol for 10min., and then washed in running water for some time. From one to four hours after treatment, the rate of O2-uptake was found to be lowered slightly (about 8%). About 20hrs. after treatment, the rate of O2-uptake in the non-anaesthetized tissue was accelerated remarkably, but in the ethanol treated tissue, such a remarkable increase in O2-uptake was not observed. So it seems to indicate that the ethanol narcosis strongly inhibits the mechanism of the acceleration of respiration induced by injury in handling. Polyphenol oxidase activity of expressed sap from ethanol-anaesthetized tissue is lower than that from non-anaesthetized tissue. The inhibitory activity of polyphenol oxidase is proportional to the O2-uptake. This coincidence seems to show that polyphenol oxidase plays a part in the respiratory enzyme system of potato tuber slice. Twenty-four hours after treatment, the extracted juice from ethanol-treated tissue showed lower pH and a greater amount of succinic and oxalic acids than that from non-treated one. It is possible that the increase in oxalic acid content is due to the conversion of ethanol to oxalic acid via acetic, succinic, fumaric, malic acids, etc., but the fact that the respiratory rate is lowered in spite of the increase in organic acid content, may be explained by the inhibition of dehydrogenase activity. The above described facts lead the writers to the conclusion that the ethanol inhibits the respiratory enzyme system and lowers the metabolic activity, with the simultaneous conversion of itself to organic acids through oxidation. The period for which the ethanol could be detected by means of Davy and Agulhon reaction in the extracted juice after treatment was about 2 days under the condition pertaining to the present experiments. The period for which the ethanol reaction was recognized in ethanol-treated tissue, was in coincidence with the period for which the resistance of tuber tissue to the infection of P. infestans was kept lowered. When the ethanol treatment was repeated 2 days after initial treatment, the appearance of necrotic brown spots was more delayed.
The known amounts of the active ingredients of Dithane, Phygon, Spergon, SR-406 and Arasan solved in solvents put into petri dishes respectively, and then exposed under dried and moist conditions in a greenhouse (average temp. 24°C-25°C.) for 1 to 7 days. The petri-dish germination was used for the determination of the ED 95 values for each ingredients with rice blast fungus, Piricularia oryzae. The decrease of fungitoxicity was observed in all chemicals under both conditions, but it was more remarkable under moist than dried condition. Among the tested chemicals, Phygon, Spergon and Arasan were relatively tolerant to the effect of weathering.
A mosaic disease of squash (Cucurbita maxima) and pumpkin (C. moschata and C. Pepo) occurs extensively in the Kanto District in Japan. Its initial spmptoms consist of faint veinclearing and green leaf mottling, developing into a mosaic. The typical veinbanding with dark green raised areas is infrequently observed. The most conspicuous and spectacular symptom is the presence of filiform leaves, infected leaves are reduced to only the veinous system with patches of green mesophyll, followed by a severe distortion of leaves, especially when the plants have been infected in their early stage of growth. The virus isolated from squash was readily transmissible by mechanical inoculation with carborundum, or by aphids, viz. Aphis gossypii and Myzus persicae, but not by cucumber beetle, Aulacophora femoralis. It was found to be seed-borne in a certain variety of squash, although the percentage of infection was low (0.6%). The virus was capable of infecting plants of 10 species in 2 families among 73 species in 25 families tested. Systemic infection was obtained on squash, pumpkin, cucumber, melon, oriental pickling melon (Cucumis Melo var. Conomon), white gourd (Benincasa hispida), white flowered gourd (Lagenaria leucantha) etc. Local necrotic spots was developed on Chenopodium album. From these results, the virus seems to be practically confined to the Cucurbitaceae. Accounts of the physical properties and identification of the virus will be given in the next paper.
1. It has been confirmed that the spore formation of Pythium ultimum is greatly promoted by some organic substance contained in corn or in carrot. 2. This substance can not be replaced by the known growth substances such as water-soluble vitamins, amino acids, bases of nucleic acids or minor-elements. 3. This substance is very unstable and can be easily inactivated by illumination or by oxidation or by alkali treatment.
Plant tissues, when infected by certain pathogenic fungi, seems to require an abundant supply of ATP in order to synthesize organic materials necessary in their defence reaction. Such an abundant supply of ATP may be accomplished by increased respiration of infected tissue, and the production of ATP is, as generally accepted, most efficient in case the oxidative phosphorylation takes place in the respiratory process. In fact, the respiration of the Helicobasidium-infected sweet potato tissues are stimulated up to two times, when the tissues are resistant, while up to 3 to 10 times, when the tissues are susceptible. Here arises a question as to whether the extraordinarily stimulated respiration of the susceptible tissue can be effective for ATP production. A series of experiments were made to obtain an answer to this question. The results are summarized below. Infected sweet potato tissues resistant susceptible Rate of respiration……increases up to 1.5 to 2 times increases up to 3 to 10 times Rate of triphenyltetrazoliumchloride reduction do. up to 1.5 times do. up to 3 times QO2CO2/QN2CO2…… 1.2 2.7 Total P…… increases by 15% increases by 20% Ba-insoluble P…… increases by 30% increases by 30% Ba-soluble, alcohol-insoluble.…… increases increases at first, decreases later on (Glucose-1-phosphate, Glucose-6-phosphate Fructose-6-phophate) Color development of section in molybdic-… ascorbic acid reagent visible after 2 or 3 days visible after 10 minutes Ipomeamarone (an uncoupler) in brown-discolored tissue…… +++ ++ in periphery of the above…… + ++ From these results, the writers conclude that, in the resistant tissues, the oxidative phosphorylation takes place in the stimulated respiratory process, while, in the susceptibe tissues, although the respirations are stimulated to an extraordinary extent, resultig in a rapid liberation of inorganic phosphate from phosphorylated intermediates.
1. This paper deals with results of some physiologial, pathological and also taxonomical studies on the causal fungus of twig blight of tree peony. The fungus was collected at first by the senior writer at Akita City, on March 15, 1952. The disease is of much economic importance but no one has yet studied about it. 2. The writers give new name Pestalotia paeoniicola Tsukamoto et Hino to the causal fungus, and propose a common name, twig blight of tree peony for the disease. 3. The first symptom of the disease is indicated by numerous, scattered, dark blackish, minute points produced on the bark of living branches. Then the infected bark becomes to gray in colour. Eventually, all the diseased brances dry out. 4. Optimum temperature of the mycelial growth of the fungus at 28° to 30°C, minimum at 8° to 10°C, maximum about 33°C, it does not grow above 35°C and 5°C., spores are produced from 15° to 35°C, the optimum temperature 28° to 30°C. Optimum hydrogenion concentration for the growth of the fungus on potato agar is pH 5.6 to 5.7.
In 1954 the writer reported on the quantitative survey of the free-auxin contained in various fungous galls and normal plants. The present article describes the results demonstrated with the regular Went's Avena test on the reformation and situation of free-auxin in the tissue of fungous gall as tabulated in Table 1. The results obtained are concluded as follows; The free-auxin in the young galls where the hymenium was not yet formed showed the maximum in quantity as compared with any other older galls. It gradually decreased as the gall formed the hymenium, and then became very small when the growth of gall reached at the grand period (see Table 2). As for the distribution of free-auxin in the gall, the upper part generally contained it in smaller quantity than the other parts, and the quantity gradually increased as the part of collection was situated lower. Such a fact may show that the free-auxin formed in gall migrates down toward the root pole. The longer the longitudinal length of the stem- and or leaf-gall is taken, the greater the quantity of auxin is diffused. Such an ability of migration, however, was not shown to be in exact proportion to the size of the piece of gall, and the remaining quantity of auxin in the piece increased as the size is taken larger (see Table 3 and 4). When the cut piece of gall was put upright in water in petri dish and held still in an incubator at 23°C., the contained auxin diffused off into the water in 6 hours or so, though a small quantity of it remained in the piece (see Table 5). On the contrary the negative result was shown as the diffusion was done in running water at 16-18°C. Rape plant infested with Albugo candida from which the auxin was eliminated according to the very procedure formed the auxin again abundantly in its stem tissue in the moist chamber at 23°C. in 24 hours. The same results were not obtained with the plant tissues infested with Exobasidium Camelliae var. gracilis and E. Symplocijaponicae (see Table 6). It seems to the writer, therefore, that the most part of auxin in the gall tissue are produced by these parasitic fungi themselves. Both cut terminals of gall piece of a certain length were connected to the dry cell of a definite voltage for a definite time (in minutes), and then they were cut vertically or crossways. The auxin of the cut tissues at each side of electric poles were measured. The result obtained showed that the tissue at the positive side contained the auxin slightly more in quantity than that at the negative. In all these experiments the fact that the node controls the migration of auxin was not taken in consideration.
Cochliobolus miyabeanus secretes pectic enzyme, xylanase and cellulase in the cultute filtrate. The optimum conditions of their activities are as follows: Pectic enzyme is in pH 7 and at 30°C., xylanase in pH 6-7 and at 30°C. and cellulase in pH 5 and at 35°C. In these enzymes, the exoenzyme is more active than the endoenzyme. In the culture, at flrst cellulase and xylanase are secreted but pectic enzyme is not, and later pectic enzyme becomes more active than the others. The toxicity of culture filtrates to rice leaves are not observed. From these results, the writer assumes that the perthophytic action of this fungus to rice plant is not due to the metabolic products like toxin, but to the action of the enzymes.