Nutritional requirements were studied to establish a defined medium for callus culture of paper mulberry tree (Broussonetia kazinoki Sieb.), one of the Moraceae group. In May 1971, callus was induced from the stem segments of a Broussonetia seedlng (20 cm long) on Murashige and Skoog's basal medium (MS) containing 1 mg/l 2, 4-D. In August when the callus grew to a sufficient mass of cells for subculturing, transplanting was made to MS+2, 4-D and MS+Benzyl adenine (BA). Callus grew more rapidly in the medium containing BA, so during the next 2-6 passages BA medium was adopted for subculturing. In January 1972 the callus of the sixth passage was transferred to MS basal medium not containing any growth substances, since it was known that the Broussonetia callus could be cultured on auxin-free medium. Subcultures were thereafter made on MS basal medium in 25-30 day's interval. Materials used in this experiment were obtained from stock callus that had been maintained on auxin-free medium onto December l973. Of the three basal media, MS, Walter and Skoog and White nutrient medium the first one was the most suitable for Broussonetia callus culture. Myo-inositol was found to be an essential micro-element and the optimum concentration was 100mg/l. Vitamins should be half required because even if all the three vitamins, thiamin, pyridoxin and nicotinic acid were eliminated, the callus grew to some extent, although not so much as when all of them were added. It was noticeable that the Broussonetia callus showed an autotrophic feature against auxin requirement. The addition of NAA or 2, 4-D to the basal medium gave negative effect, whereas TIBA, one of the antiauxins, increased the growth rate of callus at a low concentration (10^-6 M), although it severely depressed callus growth at a high concentration such as 10^-5 M or 10^-4 M, especially in the latter. Broussonetia callus seemed to become a habituated state against auxin requirement within a short period after inducing callus, because the callus tissue induced in ah another experiment showed the same autotrophic feature in the second passage as of the callus used in this experiment. The necrotic callus caused by high concentration of TIBA (10^-4 M) recovered growth potency if transferred to basal medium or basal medium+BA, the latter being more effective. Abscisic acid depressed callus growth at a lower concentration than TIBA.

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[in Japanese]

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[in Japanese]

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Qualitative changes in apparent stomatal aperture and transpiration rate of two potted tobacco plants (Nicotiana tabacum L. var. Bright Yellow) after topping were simultaneously measured with porometers and balances by which continuous recording were enabled (fig. 1). The experiment was conducted in the growth cabinet under the conditions of the illumination of 8800 lux from 9.00 a.m. to 5.00 p.m. and of other meteorological factors as mentioned in fig. 2. One plant was stopped watering during 12 successive days and, after severe wilting, rewatered sufficiently. Another plant was well watered every day to compensate the transpiration. 1. Each datum was compared between two plants, and the effect of soil moisture stress on stomatal opening and rate of transpiration are indicated in fig. 3. In the developing process of water stress, the stomatal opening began to decrease at pF 2.7, but the rate of transpiration began to decrease at about pF 3.4. Therefore, it was made clear that the stomatal function is more sensitive to the water shortage. 2. When water stress increased to pF 4.0, the distinct closing of stomata accompanied by transpiration depression was perceived even in the dark (fig. 3). Such a small change of aperture of stomata was easily detected by the recording porometer method but not by the infiltration method. 3. There exists a curvilinear relationship between stomatal opening and transpiration rate in the light, but it was obscure in the dark (fig. 4). A marked difference in these two curves of transpiration is caused by the existence or absence of illumination. The curve in the light indicates that the smaller the aperture operates the higher the degree of stomatal control of transpiration is. At the time when the plant is wilted and its stomatal aperture is small, actual transpiration rate shows a large depression as compared with Bange (1953)'s theoretical curve obtained by leaf disk method. Such depression may be caused by the reduction of leaf area and the change of leaf form in intact plant. The transpiration rates of recovery processes after rewatering (in dotted lines) are evidently lower than those before wilting both in the light and in the dark. 4. After rewatering, the wilted tobacco plant quickly regained its normal turgesence in external appearance. However, the recovery of full stomatal function required four days and transpiration rate did not recover enough during four days owing to the after-effect of severe wilting.

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Petiolar tissues of mature leaves of soybean plants were killed by heat and the subsequent changes in total nitrogen and free amino acids content of the petiole-treated leaves were compared with those of the petiole-untreated leaves. During the experimental period there was a consistently higher accumulation of total nitrogen in the petiole-treated leaves than in the petiole-untreated leaves. When topping treatment (a removal of a growing region of the stem) was made to the plants, however, an accumulation of total nitrogen occurred in both the petiole-treated and petiole-untreated leaves to almost the same extent. These observations suggest that the nitrogen content of a mature leaf is maintained by a counterbalance of import and export of nitrogen and that the topping treatment reduces export without seriously affecting import. Similar results were obtained with total free amino acids, indicating that amino acids may be continuously translocated from the mature (pre-senescent) leaves and the translocation of amino acids could also be reduced by the treatment. From these results it may be concluded that source and sink relationship in respect to nitrogen metabolism may generally exist between mature leaves and a growing stem apex.

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Spray applications of two oxathiin systemic fungicides, carboxin (50% 5, 6-dihydro-2-methyl-1, 4-oxathiin-3-carboxanilide) and oxycarboxin (50% 5, 6-dihydro-2-methyl-1, 4-oxathiin-3-carboxanilide-4, 4-dioxide) were tested to protect flue-cured tobacco from leaf damage induced by air pollution oxidants. Bel W3 (cigar wrapper tobacco) was used for the tests in an ozone exposure chamber, and MC (flue-cured tobacco) for the field tests, respectively. 1. Among the concentrations tested, 1, 000 ppm solution of carboxin and 500 ppm solution of oxycarboxin were most effective in reducing ozone injury. Carboxin higher than 1, 000 ppm however, caused yellowish chlorotic lesions in the young leaves. For escaping from ozone damage the chemicals were most effective on about 5th day after application and not still so effective on the next day of spplication. The effect of sprayed chemicals was found to persist about 10 days. Oxycarboxin sprayed only to lower epidermal surface of a leaf produced same effect as that sprayed to both surfaces. Whereas, the protecting effect by spraying the compound only to upper epidermal surface decreased by approximately half of that by spraying to both surfaces. Those results suggest that the chemicals neither translocate from the sprayed leaves to other nor from one part to the other half beyond the midrib within a leaf. 2. Spray application of oxycarboxin in 1, 500-fold diluted solution (333 ppm) was found to protect field-grown tobacco effectively from oxidant injury. The chemicals was found to produce no damage on treated leaves and no effect was detected on both yield and quality of harvested leaves as well. Carboxin and NF-69 (mixture of oxycarboxin and thiophanate-methyl in the ratio of 1:3.67) delayed leaf maturity remarkably, although oxycarboxin produced no effect in this respect. 3. From the results obtained here, it is indicated that oxycarboxin can be applied as an effective protectant against weather fleck to flue-cured tobacco.

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The primary objective of this research was to elucidate the differences in movement of assimilates between types of stem termination in soybean varieties. Tokachinagaha, Koganejiro and Harosoy were examined as an example of determinate, intermediate and indeterminate types, respectively. These varieties have approximately the same maturity and similar yield potential in Hokkaido(N 42-45°). Koganejiro has been bred from cross between Tokachinagaha and Shika No. 4(indeterminate, originated in north-eastern China), having a intermediate trait on the time of stem termination after flowering. Feeding was done at three growing stages, intial flowering, young pod development and pod filling. Either the 4th (L-4), the 8th (L-8) or 12th (L-12) trifoliated leaf from the bottom of the main stem was fed. The leaves were allowed to photosynthesize ¹⁴CO₂ (50μCi in each plant) for 15 min. under midday solar radiation. After remaining for 24 hours in the natural conditions, the plants were divided into various parts at each node on the main stem and each branch, and their radioactivities were determined. 1. Efficiency of ¹⁴C assimilation (defined as ratio, total ¹⁴C divided by fed leaf area) became higher with smaller leaf area and lower with larger one among varieties, among leaf positions and irrespective of leaf age (Fig. 1). 2. Translocation rate ¹⁴C-assimilates was ranged from 20% to 50% at the initial stage of flowering. Tokachinagaha showed the highest rate, followed by Koganejiro and Harosoy, and rate of L-4 was higher than that of L-8. At the stage of young pod development, differences between varieties in the rate became smaller, ranged 50% to 60%. Further, at the stage of pod filling the translocation rate from L-12 showed about 80% in each variety, and Harosoy showed higher value than those of other varieties (Tab. 1). 3. Specific activities of ¹⁴C in various parts of plant at the initial stage of lowering are shown in Fig. 2. The pattern of activity was simillar between varieties, and the strongest sink was the metabolically active organs, closely located fed leaf. 4. Distribution patterns of ¹⁴C-assimilates in each stage of growth were as follows. At the initial stage of flowering, Harosoy showed lower percent distribution from L-4 to branch or from L-8 to underground part, and higher from L-8 to forthcoming parts, comparing with other two varieties (Tab. 2). At the stage of young pod development, 30% to 40% of ¹⁴C-assimilates which were seemed to be tentative storage were found in the main stem in each variety, when ¹⁴C was fed from leaves of main stem (Tab. 3). On the other hand, when ¹⁴C was fed from leaf of branch, about 70% of ¹⁴C were distributed to pods of respective branch, and only 9% remained in the stem of branch (Tab. 4). At the stage of pod filling, 80% to 90% of ¹⁴C-assimilates were distributed to pods and seeds. While in Tokochinagaha they were translocated manly in the pods and seeds of the node where fed leaf attached, in Harosoy ¹⁴C was fed at L-12 they were translocated mainly to the pods and seeds located under, and when it was fed at L-8 they were moved preferably to those of branches (Tab. 5). 5. It was of interest that the distribution of ¹⁴C-assimilates into pods and seeds in each node on the main stem was intensively controlled by phyllotaxis in determinate type of variety, Tokachinagaha, comparing with other varieties, as shown in Fig. 3. 6. Based on these observations, it was surmised that mobility of ¹⁴C-assimilates of determinate type is higher than those of the indeterminate type at the vegetative stage, but at the reproductive stage especially at the pod filling stage it is reversed among growth types.

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We investigated the effects of high temperature treatment (40°C three weeks) on dormant rice seeds of Hadsaduri (Oryza sativa cv.) which was known as a variety of deep dormancy and results obtained are summarized as follows; 1. The seed of which dormancy was broken by high temperature treatment could germinate under both aerobic and anaerobic conditions, whereas dormant seed could not germinate under the anaerobic condition. 2. Warburg manometric techniques were used for the determination of respiratory gas exchange. In the case of non-dormant seeds, the amount of released carbon dioxide always exceeded that of oxygen uptake. Whereas the dormant seeds showed nearly the same amount of oxygen uptake and carbon dioxide release. 3. Determination of ethyl alcohol was carried out by gas chromatography. Non-dormant seeds usually produced more amount of ethyl alcohol than dormant seeds. When both dormant and non-dormant seeds were incubated under nitrogen gas at 30°C, the same tendency as above was observed. 4. When non-dormant seeds were co-treated with sodium iodoacetate, which was known as one of the inhibitors of enzyme SH group, at 5mM and 10mM concentrations, the production of ethyl alcohol was inhibited. Germination of hulled rice of non-dormant seeds was not affected up to the concentraton to 10mM under aerobic condition, but almost completely inhibited at 5mM under submerged condition. From the facts described above, it might be possible to consider that the dormant rice seed had the aerobic respiratory pathway but had not an active anaerobic respiratory pathway sufficient for germination. Effects of high temperature treatment on breaking the dormancy of rice seed may be attributed to the activation of anaerobic respiration.

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Application of gibberellin at different staged of growth induced female or sterile spikelets in the tassel. Treatments at early reproductive stages were most effective in producing tassels with many female spikelets. Sterile tassels were produced in latter treatments. The female spikelets induced by gibberellin had an upper female floret and a lower aborted floret. The upper female floret had a pistil and three rudimentary stamens. This structure was the same as a female spikelet of the ear. From these observations and the fact that both the stamens and the pistil differentiate in the florets of the tassel, it is concluded that gibberellin induces female spikelets through the promotion of the pistl development and inhibition of the stamen.

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These studies in series were devoted to clarify the characteristics of the white belly kernel which had an opaque part at the ventral portion of its endosperm. In this experiment, white belly kernels were cut transversely with a razor blade and scanning electronic photographs were taken. The experimental materials used were Norin-8, Kinmaze, Sekai-1, Gohyakumangoku (white core rice) and Sinthurumochi (glutinous rice) of Japonica type variety and Keikyakusen and Kouketuzu (glutinous rice) of Indica type variety. The following results were obtained. 1. The translucent parts of endosperm tissue of white belly kernels were easily pervious to light, but the opaque parts of endosperm tissue of these kernels were difficult to transmit light (fig. 3, 6). The permeability of light in the individual endosperm cell varied from opaque parts to translucent parts (fig. 4, 8). 2. The compound starch granules in translucent parts of white belly kernel endosperm were polygonal in shape and tightly packed with no air spaces among them (fig. 12), whereas those in opaque part of this endosperm were round in shape and loosely packed with many intergranular air spaces (fig. 10, 13, 15, 23). 3. The compound starch granules, which located the outerside of opaque parts, were easily broken into many single starch granules by the mechanical stress (fig. 15-16). 4. The opaque parts of white core, milky white, and opaque kernels had round in shape, loosely packed compound starch granules resembled with those of white belly kernels (fig. 19-22). 5. The glutinous rice had micropores on the inside surface of the single starch granules and hollows on the outer surface of compound granules, which were absent in non-glutinous rice starch granules (fig. 25-27). 6. The endosperm cells in 5-day old kernels had uniform round compound starch granules which were loosely filled with many air spaces (fig. 28-29). The endosperm cells in 16-day old kernels were packed by compound starch granules which were varied in shape and size (fig. 30-32). In more developing kernels, the compound starch granules were tightly packed in the endosperm cell and no air space was observed among the granules. Then, the endosperm tissue became translucence ( fig. 33). 7. The starch granules of endosperm had two types, i. e., one was the large compound starch granule which was composed of many single starch granules and another was the small compound starch granules which were composed of several single starch granules. Among the compound starch granules, the globular protein body were embedded (fig. 37). 8. From these results, because of the loose structure and the high proportion of inter-granular air spaces, the opaqueness of endosperm tissue would be caused by light scattering.

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