This investigation was made in order to simplify bloom date estimation by using the same method regardless of differences in region and date. The correlation between the mean air temperature and the development velocity, difined as the percentage of the reciprocal of the number of days between bud break and blooming, was determined in 12 apple cultivars at the Aomori Apple Experiment Station. The correlations were very high in all the apple cultivars examined.
Simple regression equations were derived and used to calculate the developmental zero and the total effective temperature as follows: the developmental zero was calculated as the temperature at which the development velocity was zero, the total effective temperature was calculated by subtracting the developmental zero from the value of the temperature at which the development velocity was a hundred.
Using these two values, the apple bloom date was calculated in four other regions. Calculations were as follows: if the daily mean air temperature after the bud break date was higher than the developmental zero, then the positive difference between these temperatures, i. e. the effective temperature, was accumulated. When the accumulated value exceeded the total effective temperature, then that date was regarded as the calculated bloom date. In all apple cultivars, the difference between the calculated bloom date and the actual bloom date was nearly always less than two or three days.
The apple cv.‘Starking Delicious’, in which bud break had not been recorded, was grown in a growth chamber in the winter to compare the actual bloom date and the calculated bloom date using the same two values as described above. The difference between the two dates was only one day.
The method described appears to be a very good way of estimating the bloom date in any apple cultivar.

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Cork spot and bitter pit are the main spotting disorders of apple fruit in Japan, but it is difficult to separate these two disorders macroscopically, as intermediate symptoms are sometimes found. In this paper, the morphology of both disorders was compared microscopically and macroscopically.
Under climatic conditions of the Morioka district, cork spot appeared at the immature stage of fruit development, from mid-August to early September, while bitter pit appeared at the mature stage and during storage.
When analysed microscopically, it was found that cell collapse in the discolored cortical tissue of bitter pit was more severe than in that of cork spot.
When examined during the harvest season, intact cells in the discolored tissue of cork spot affected fruit were significantly smaller than those of the neighboring sound tissue. This may be due to a retardation of cell enlargement in the discolored tissue after the occurrence of the disorder. In contrast, no difference in cell sizee were found between the discolored and sound tissues in fruit affected by bitter p t which appeared after the mature stage.
Starch grains in the discolored cortical tissue of cork spot disappeared just after the occurrence of the disorder.
Small, specialized cells, approx. 50μm in diameter, appeared in the intercellular space of the discolored cortical tissue of cork spot. In rare cases, a layer of these small cells surrounded the discolored tissue. Formation of these small cells may have been stimulated by tissue injury caused by the disorder. A similar type of small cells was also found arround mechanically crushed cortical tissue.
No small cells were found in the discolored cortical tissue of bitter pit. The ability to induce the formation of small cells may have already ceased before the mature stage of fruit development during which this disorder appeared.
These microscopic differences between cork spot and bitter pit may be related mainly to the stage of fruit development at which each disorder occurred. The ‘intermediate’type was seldom found when using these differences as the basis of classification.
The occurrence of each disorder differed among cultivars and strains. Almost all spots found on ‘Tohko’, ‘Redgold’, ‘York Imperial’and ‘Aori No. 3’were cork spot, and those found on ‘Ohrin’ and ‘Tsugaru’ were due to bitter pit. Both disorders were found on ‘Starking Delicious’, ‘Megumi’, ‘Jonathan’ and ‘Fuji’.
Spots caused by cork spot were usually more than 5mm in diameter, while those caused by bitter pit were generally less than 5mm. However, spots of about 3mm in diameter caused by cork spot, and of about 10mm in diameter caused by bitter pit were sometimes found.

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To elucidate the characteristics of color development in apple cvs ‘Starking Delicious’ (‘SD’), ‘Fuji’ and‘ Mutsu’, the effeccts of light on anthocyanin synthesis and L-phenylalanine ammonia-lyase (PAL) activity were investigated. Irradiation with white light and simultaneous irradiation with white and ultraviolet light with an emission peak at 312nm (white+UV 312) were used. When the whole fruit skin was examined, ‘SD’ produced higher anthocyanin levels than ‘Fuji’especially under white light. In skin disks, however, anthocyanin synthesis was increased in ‘Fuji’to the same level as in ‘SD’. The yellow-colored cultivar, ‘Mutsu’, did not respond to white light, and only produced a small amount of anthocyanin under white+UV 312 light. In whole fruit skin at least, there was a close correlation between anthocyanin synthesis and PAL activity. In skin disks, PAL activity was far higher than in whole fruit skin, however, anthocyanin synthesis did not show a similar increase in PAL activity. In ‘Mutsu’, white light did not induce anthocyanin synthesis although it stimulated PAL activity to the same extent as the white+ UV 312 light.

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To clarify the process of growth and nutrient absorption from nursury stock to mature peach tree, the trees cultivated under the same conditions were lifted and separated into constituent parts every year during the first 5 years and every other year thereafter, and then were weighed and analyzed. The results obtained were as follows:
1. The amount of annual dry matter production increased every year for the first 7 years, and then reached a constant value by the reason that the increment of tree parts decreased thereafter while fruit yield further increased. Fruit yield and dry matter weight of fallen leaves increased for the first 9 years in proportion to expansion of the tree crown, and then reached a constant in 11 years of age.
2. Young branches and fine roots had higher contents of nutrient than older branches and roots regardless of age of trees, but nutrient contents in all parts of tree varied significanthy from one year to another.
3. The yearly variation in the amount of annual nutrient absorption and the amount of stored nutrient after the growing season showed a different pattern for each nutrient element.
4. The amounts of nutrient elements absorbed by the 11 year-old tree were 104kg of N, 25kg of P₂O₅, 131kg of K₂O, 109kg of CaO, and 23kg of MgO under the condition that the trees were planted at a rate of 212 trees per ha and produced 28t fruit per ha. The amounts of N, P₂O₅ and CaO absorbed reached a constant after 9 years of cultivation, but the amount of K₂O increased until 11 years of age because of increasing fruit production.

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Dry matter production in pineapple plants which were transplanted to the field in September could be divided into four stages: 1) the first stage of early plant growth; 2) the second stage of middle plant growth; 3) the third stage of fruitlet differentiation; 4) the fourth stage of fruitlet growth. These stages were strongly affected by the climate of the season.
At harvest, the total dry weight per plant of ‘Mitsubishi’ was heavier than that of ‘Hawaii’. However, the dry weight of the fruit was lower. This shows that translocation of photosynthates to the fruit was more active in ‘Hawaii’ than in ‘Mitsubishi’.
Leaf area index (LAI) increased rapidly in the latter half of the second stage and reached a maximum of 6.5 in the third stage. The maximum value remained almost unchanged until the fourth stage.
Seasonal changes of the crop growth rate (CGR) showed bimodal curves with two peaks. The first peak appeared in the second stage (October) and the second one in the fourth stage from May to June. The maximum CGR was 8.1-8.2gm^-2
Net assimilation rate (NAR) were similar to those of CGR. Maximum NAR was observed in the second stage (August) and the value was 2.40 to 2.55gm^-2 day^-1. NAR was largest when the LAI was 2 to 3. CGR reached a maximum when LAI was 3 to 4. Optimum LAI was estimated to be 3.01.
Relative growth rate (RGR) was closely correlated with NAR. Efficiency of solar energy utilization was 0.2% in the first stage and reached a maximum of 1.2% in December. Flower bud initiation began from this time.
Active accumulation of photosynthates in the fruit was observed when LAI was kept at 3.01 and when flower bud induction treatment was practiced. Analyses of dry matter production of pineapple plants and the structure of the community showed that to achieve a short leaf length and narrow angle of leaf emergence were necessary community with high productivity. Thus, breeding should be carried out to select plants with these characteristics.

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Investigations were carried out in order to clarify the effect of gibberellic acid (GA₃) on the flowering, inflorescence morphology, and pollen germination in 6 triploid cultivars: ‘Egu-imo’; ‘Hasuba-imo’; ‘Ishikawa-wase’; ‘Oyazeme’; ‘Taikoban’; ‘Daikichi’, 2 diploid cultivars: ‘Tono-imo’; ‘Takenoko-imo’, and colchicineinduced tetraploids from ‘Takenoko-imo’ of taros (Colocasia esculenta Schott) cultivated in Japan.
GA₃ was applied either by soaking apical buds in the seed corms of 8 cultivars in each aqueous solution of 0, 250, 500, and 1000ppm for 2 hours a day before planting, or by dropping 1-2ml of 500ppm on the bases of petioles of the young plants in ‘Takenoko-imo’ and its induced tetraploids four times at intervals of 2, 5, 7 days commencing with the 3-leaf stage.
Among the 8 cultivars and induced tetraploids treated, flowering occurred in 6 cultivars except in ‘Hasuba-imo’ and ‘Tono-imo’, in the induced tetraploids, and the untreated ‘Egu-imo’. There were differences in the reaction to the three concentrations of GA₃ among cultivars.
The percentage of plants flowered was 100% both in ‘Takenoko-imo’ and its induced tetraploids treated by dropping, and 6.7-84.6% in 6 cultivars treated by soaking. The number of inflorescences per plant was about one in ‘Ishikawa-wase’, ‘Oyazeme’ and ‘Taikoban’ with a lower percentage of plants flowered, and was more than 2.5 in ‘Egu-imo’ and ‘Daikichi’ with a higher percentage of plants flowered, while it was 14.5 in ‘Takenoko-imo’ and 7.4 in its induced tetraploids treated by dropping.
The earliest inflorescence development was observed in ‘Takenoko imo’ treated by soaking after 10 weeks from treatment, while the latest was recorded in ‘Ishikawa -wase’ and ‘Oyazeme’ after 13 weeks. Treated ‘Egu-imo’ produced inflorescences more than 3 weeks ahead of the untreated ones. The duration of inflorescence flowering was 1-4 weeks in 3 cultivars and was about 9 weeks in 2 cultivars and both ‘Takenoko-imo’ and its induced tetraploids.
In ‘Egu-imo’ the inflorescences which were produced on treated plants at almost the same time as those on untreated plants were similar in both the length of floral parts and the number of florets. The early-produced inflorescences, however, were fewer in the number of florets, compared with those of the late-produced inflorescences. All treated cultivars except ‘Hasuba-imo’ and ‘Tono-imo’ also gave rise to a number of bract-like deformities with no spadaces.
Triploid cultivars: ‘Ishikawa-wase’, ‘Oyazeme’ and ‘Taikoban’ did not extrude any pollen at all, while the pollen sheddings from triploid cultivars: ‘Egu-imo’ and ‘Daikichi’, a diploid cultivar ‘Takenoko-imo’ and its induced tetraploids were inconsistent. Percentage of pollen germination of their triploid cultivars was very poor and none of the pollens of their early-produced inflorescences germinated. On the other hand, the pollens of diploid ‘Takenoko-imo’ germinated more than those of triploid cultivars, giving 24.7% in germination percentage.

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The resting spores of clubroot can survive in soil for several years, and it is very difficult to control the disease chemically. In this study we examined the effect of cultivating resistant plants on reducing the number of resting spores in soil.
1. In the autumn of 1980, field soil was inoculated with resting spores of clubroot to a density of 5×10⁶ per 1ml fresh soil. From 1981 to 1984 several kinds of crops, including resistant strains, were cultivated during the spring season, and susceptible Chinese cabbage or turnip was cultivated in the autumn season.
2. When spinach and sorghum were cultivated in spring, there was little decrease in the level of diseases in susceptible turnips compared with the continuous cultivation of susceptible strains.
3. When resistant kale and turnip strains were grown, the incidence of disease was suppressed drastically, so as to be of no practical problem.
4. After four years cultivation, the density of resting spores in soil was estimated to be about 5×10⁵/ml in the sorghum plot, 5×10³/ml in the kale plot and less than 5×10³/ml in the turnip plot, while the density of spores in the continuous cultivation plot was estimated to be more than 5×10⁶/ml.
From these results it is concluded that resistant strains of Cruciferous crops induce spore germination but suppress disease development in roots, and as a consequence have a greater effect in reducing the number of clubroot spores in soil.

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In the vegetative strawberry plants with a single leaf retained per plant and fed with ¹⁴CO₂, the current export of ¹⁴C-assimilates was small from the half- and just fully-unfolded leaves, but it increased from the expanded old leaves, reaching about 45% from the 40-day-old leaves. The percentage export of about 45 from the old expanded leaves and the change in percentage export with the leaf age were little affected by the position of leaves on the stem and the extent of new apical growth.
On the contrary, the distribution pattern of ¹⁴C-assimilates varied much with the position of leaves and depending on relative capacities of sinks. When the leaves differing in age but on the same position on the stem were fed, the percentages distribution to the roots and new apical growth were minimal and maximal from the 10-day-old leaves, respectively, although the number of apical developing leaves was greatest in the plants fed to the 40-day-old leaves.
In the intact plants with 7 leaves, in which L 7 was the uppermost and just fully-unfolded leaf at feeding, the percentages export from the expanded leaves, L 1 to 5, were also 40 to 50. The percentage distribution to the new apical growth was greater from upper leaves, ranging from 40 from L 1 to 85 from L 7, and the reverse was true for the roots, ranging from 75 from L 1 to 29 from L 7. The phyllotaxis of 2/5 did not affect the distribution pattern perhaps because the anastomosis developed well in the crown.
Although nothing but a case study, in the plant set upright and irradiated from just above, the contribution rate to the total production of photoassimilates was greatest for L 5 with the percentage value of 25 followed by 21 for L 6, although the photosynthetic capacity (measured with detached leaves under the uniform conditions) differed little between L 1 to L 5 and somewhat lower in L 6 and 7, while the leaf area was greatest in L 5 and 6. The extent of mutual shading was also estimated with the ratios of the photosynthetic rates of leaves in situ on the plant to those of detached leaves, and it was shown to be about 20% in the 3 upper leaves, while it increased in lower leaves, reaching 67% in L 1.

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Mycorrhizae of horticultural plants currently being cultivated in Japan were investigated.
Endomycorrhizae were formed in roots of almost all kinds of fruit trees, vegetable crops and flowers and ornamental plants. Of the flowers and ornamental plants examined, azalea had so called ericalean and cymbidium orchidaceous mycorrhiza. Other horticultural plants had VA mycorrhizae. Only in stock plants were no mycorrhiza observed. Ectomycorrhizae were not found in any of the plants examined.
VA mycorrhizal fungi penetrated the root through the root hairs or epidermal cells and then formed vesicules and arbuscules in the cortical tissue. VA mycorrhizal infection was not found in the growing part, stele and root tissue near the stem. Both intercellular and intracellular vesicules were formed. Arbuscules were formed in the cortical cells. Vesicules were 50 to 100μm in diameter and had various forms. VA mycorrhizae of satsuma mandarin grafted onto trifoliate orange had small vesicules which were 10μm in diameter. Arbuscules (branched hyphae) were formed immediately after infection.
Vesicules and arbuscules were not observed in ericalean and orchidaceous mycorrhiza. In these the hyphae, which were smaller than in VA mycorrhiza, had septa and were coiled in cortical cells.

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Freesia corms were either subjected to smoke or ethylene to break dormancy, and the corms were stored dry at room temperatures following the treatment. For the determination of depth of dormancy, they were planted at different times for the sprouting test. The differentiation of leaves on their uppermost axillary buds and formation of roots on their basal parts were also observed. To determine the chilling response, the treated and non-treated corms were transferred to wet cool storage at 10°C for 5 weeks at different times, and later planted in pots and grown.
Non-treated corms showed resumption of leaf differentiation on their uppermost buds followed by root formation and rapid sprouting after planting on August 31, while ethylene or smoke pre-treated corms attained the same state on August 17 or July 20, respectively, i. e. 2 or 6 weeks earlier. This fact demonstrates the promotive effect of smoke or ethylene on the breaking of dormancy.
At the end of chilling, sprouting and differentiation of flower-buds were most advanced in the smoke-treated corms, followed by ethylene-treated ones, and then by non-treated ones. When smoke or ethylene treated corms were transferred to the chilling on August 17 or August 31, respectively, they all flowered and exhibited full chilling response. On the other hand, only 86% of the non-treated corms flowered even when they were chilled on September 14.
Full chilling response was obtained when corms were chilled after roots appeared on their basal parts. Thus, root formation is a good indicator of the starting time of chilling.

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Cucumber fruits and turnip roots were harvested and held at 25°C with the moisture content which was left decreasing for the first two days but was controlledwith little change for the following two days. In both plant organs after two days of storage, the proportion of the total tissue volume occupied by gas space became slightly lower. The mean pressure of gas decreased in cucumber fruits and increased slightly in turnip roots. During the next two days, the gas space developed remarkably in the tissue and the mean pressure of gas rose significantly. These changes were ascribable largely to the accumulation of gas at a pressure of 1.3 bar (0.3 bar above an ambient pressure) and above. The gas space was present as bubbles mainly in cells. The volume of both stored organs decreased for the first two days but increased afterwards.
We concluded that the increase in volume of stored cucumber fruits and turnip roots was induced by accumulation of gas under pressure largely in cells. This accumulation of gas was regarded as a cause of further various phenomena concurrently observed in storage such as disappearance of wilting state, a decrease in specific gravity and development of spongy or pithy tissues.

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As a result of previous studies on tomato fruit, further examinations were carried out on the physiological response of fruits to limited levels of vibration. In this report, eggplant, apple, Japanese pear, satsuma mandarin (Citrus unshiu Marc.), natsumikan (C. natsudaidai Hayata) and grape fruits were used. The effect of vibration at 1G, 2G and 3G for 1 hour or 5 hours on the respiration rate was determined during and after vibration.
In general, the respiration rate increased rapidly from the beginning of vibration, and continued to increase during vibration. The rate also continued to increase for a period after vibration. The elevated respiration rate fell once, then showed a small rise, and returned gradually to the initial level.
When the vibration time was short, the increase in rate of respiration was proportional to the intensity of vibration. However, for the longer vibration time, the increase in the rate of respiration was lower at 3G than that at 1G. This observation seemed to suggest that some physiological disorder may have occurred in fruit exposed to the more intensive vibration exceeding the limited level of vibration for every fruit.
The respiration rate of eggplant and apple fruits seemed to be more sensitive to vibration than that of the others. The respiration rate of grape fruit harvested at earlier maturity was more sensitive to vibration than that of fruit harvested at later maturity.
In addition, changes in internal gas concentrations during vibration were determined in Japanese pear and tomato fruits vibrated at 1G and 3G for 5 hours. High levels of carbon dioxide and low levels of oxygen were detected in both fruits, and high levels of ethylene were detected in tomato fruit.

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The type of calcium (Ca) compounds in plant tissues and their changes during storage were determined in several kinds of fruits and vegetables. The four types of Ca compounds extracted were as follows: water soluble Ca(F-I: mainly water soluble organic acid salts and Ca ion), 1N-sodium chloride soluble Ca(F-II: Ca-pectate and Ca-carbonate), 2%-acetic acid soluble Ca(F-III: Ca-phosphate), and 5%-hydrochloric acid soluble Ca(F-IV: Ca-oxalate).
1. The composition of the four types of Ca compound was different in the various fruits and vegetables. The predominant types were as follows: F-IV in spinach, F-I in parsley, radish seedling and mume (Japanese apricot) fruit and F-I and F-II in banana and tomato fruits.
2. In spinach leaves, the composition varied with the age of leaves; relatively high levels of F-II and F-III as well as F-IV were found in young (inner) leaves, while the level of F-IV increased in mature (outer) leaves.
3. During storage at 20°C for one week, the composition of Ca did not change in radish seedlings, but in banana and tomato fruits F-I increased with ripening.
4. In spinach which contains much F-IV Ca, and in parsley which contains much F-I Ca, changes in the content of ascorbic acid and in the composition of Ca compounds were determined during storage at 1°C and 20°C. In both species there was no clear change in Ca compounds at 1°C. However, in stored at 20°C there were a sharp decrease in F-I Ca and an increase in F-IV Ca, accompanied by a decrease in ascorbic acid content. In spinach stored at 20°C, Ca compounds did not change, while ascorbic acid content decreased.

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