1. The sulfur oxidation by Thiobacillus thiooxidans was inhibited by long chain fatty acids at neutral and alkaline pH. The rate of inhibition seems to depend on their solubility in water. 2. Although DNAase, RNAase, lipase, cellulase and proteases did not inhibit the sulfur oxidation, lysozyme and snake venom enzymes caused inhibition which was enhanced by NaOH treatment. The optical density of cell suspension did not decrease but increased with the addition of lysozyme. Various experiments designed for lysis of the intact cell with lysozyme was not successful. An interpretation of inhibitory action of lysozyme is that lysozyme, a basic protein, acts as a cementing substance to aggregate cells and prevents them from accessing onto solid sulfur. The mode of action of snake venom enzymes was discussed in relation to the inhibition of sulfur oxidation by long chain fatty acids which would be possibly liberated from the cell surface by the action of venom enzymes. 3. Isolated cell wall of T. thiooxidans was rapidly disintegrated by the action of trypsin and after the digestion, fibrous structure in the residual material was observed electron-microscopically.
Chloroplasts of four species of Spirogyra are examined by cytochemical methods for the possible presence of DNA. Both the Feulgen reaction and methyl green-pyronin staining indicate the presence within the chloroplast of many DNA-containing bodies. These bodies are spherical or somewhat ellipsoidal in form, approximately one micron in diameter. They are located around the pyrenoid or linearly arranged in the central zone of the chloroplast. The size and location of these bodies are somewhat different in each species. These bodies resemble the DNA-containing bodies in the chloroplast of Chlamy-domonas which were previously reported by Ris & Plaut.
In the present experiment, it was found that Pharbitis plant is very radiosensitive in the early stage, especially for initiation and development of flower primordia. At the irradiation doses below 1000 R, especially those ranging from 450 to 660 R, gamma-rays inhibited the flower initiation considerably. On the other hand, the growth of seedlings were scarcely affected. Furthermore, acute irradiations with low doses of gamma-rays (below 330 R) promoted the flower initiation, when the seedlings were irradiated before a single flower-inductive dark period. The influence of gamma-rays on the flower initiation was different depending mainly on the time when the seedlings were irradiated: the reversion of flower-buds to vegetative ones, and the appearance of various malformed types of flower-buds were observed. And a definite relationship between the occurrence of the malformation and the time of irradiation was found.
The histochemical and structural changes during the conjugation process of Spirogyra were observed in relation to carbohydrate metabolism. The degree of staining with 2, 3, 4-triphenyltetrazolium chloride or with osmic acid was higher in the vegetative cells than in the conjugating cells. In the conjugating cells, conjugation tube was most strongly stained. The outer slime layer disappeared and the cell wall swelled during the conjugationprocess. The amount of hot-water soluble but acetone or ethyl alcohol insoluble carbohydrate fraction decreased during the process.
The growth retardants CCC and B-Nine, and the fungicides PMA and 8-HQ when sprayed to young tomato plants reduced the transpiration water loss by 20-35%, induced a reduction in stomatal width by 10-33% and delayed the wilting of plants due to soil drought by about a week. The order of effectiveness of these chemicals in inducing stomatal closure and in delaying the wilting of plants is: PMA>CCC>B-Nine>8-HQ. The significance and the mechanism of the chemical closure of stomata in relation to the survival of plants under conditions of soil drought is discussed.
The photosynthetic activity in the different portions of leaf blade and in both upper and lower epidermal surfaces of intact tobacco leaves (Nicotiana tabacum “Bright Yellow”) was measured at various stages of leaf growth, using an infrared carbon dioxide analyzer. The photosynthetic activity and the growth rate of apical, middle and basal portions of the leaf varied markedly with the stage of leaf development. The activity increased with the proceedings of leaf age and reached a maximum after the stage of full expansion of respective portions. Therefore, in early expanding stage of the leaf it was difficult to point out which portion of a leaf might have the highest activity. After the termination of the expansion of the basal portion, however, the photosynthetic activity of individual portions had a steady tendency, that the activity was high in the basal, low in the apical, and medium in the middle portion. The photosynthetic activity on the upper epidermal surface was usually low in older leaves, but the activity rised temporarily soon after the turning up of light and then fell down rapidly. On the lower epidermal surface, the saturation level of the photosynthesis-light intensity curve shifted to lower with the proceedings of leaf age, but no detectable change of the level was observed with the upper epidermal surface. Both the saturated light intensity and the amount of fixed CO2 per unit leaf area were nearly independent of the direction of illumination, from above or below.