Effect of night temperatures throughout the later part of fruit development on the diurnal fluctuation of fruit diameter and several characters of mature fruit were investigated. On the one hand, one-year-old Chojuro pear trees grown in pots were placed in growth cabinets at 15, 22, and 30°C, during the period from July 30 to September 18. On the other hand, secondary scafold limbs of ten-year-old Nijusseiki pear trees grown in the field were exposed to night temperature of 30°C from August 2 to October 3, and responses of treated fruits were compared to those of fruit exposed to natural night temperatures.
The outline of the results obtained are as follows:
1) In August the effect of high night temperature can hardly be confirmed on the growing behavior of fruits. After the end of August, however, the contraction of fruit diameter in the daytime became greater in the 30°C treatment, which resulted in sudden decrease in diurnal fruit growth. Namely, the growth increment attained within a period from the onset of treatment to the harvest was most excellent in the 22°C treatment and the control lot, followed by 30 and 15°C treatments in decreasing order.
2) In the 15°C treatment, amplitude of diurnal fluctuation was considerably depressed and the contraction of fruit diameter was also reduced earliest among these treatments. On the other hand, the disappearance of the contraction occurred several days earlier at 22°C than at 15°C. In the 15°C treatment, fruit expanded rather in the daytime than at night at the nearly maturing period. In the 30°C treatment, however, the contraction was observed even at the harvest time due to the lower rate of its reduction.
3) Total soluble solids content (refractive index) of harvested fruit was lower at night temperature of 15°C than at the others. The effect of night temperature was obscure in the 30°C treatment. On the other hand, the titratable acidity of juice was lowest at 15°C and highest at 30°C. This fact implies that the maturation of fruit was markedly decelerated at night temperature of 30°C.
4) Judging from the results with Chojuro pears, it is safely deduced that the maturation of fruit was accelerated by two to three days at night temperature of 15°C and decelerated by more than ten days at 30°C.
5) Respiratory activity per unit fresh weight decreased as the age of fruit progressed. It became more promoted with increasing night temperatures. For example, the results obtained at the night of August 29 showed that the relative respiratory rate was 174 at 30°C as compared to 100 of 22°C.
6) Relative apparent photosynthesis of Chojuro leaves was 84.4 at 30°C and 56.3 at 15°C as compared to 100 of 22°C. Further, it was observed that diurnal changes in leaf moisture content were considerably reduced in the 15°C treatment. From the results, it can reasonably be assumed that low night temperature (15°C) during the nearly maturing period exerted harmful effects on the metabolic activity of Chojuro trees.

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1. The water content and the water saturation deficit of burning Bartlett pear leaves were compared with those of healthy ones, since the leaf burn seemed to be caused by desiccation resulted from excessive transpiration. The water content expressed as percent of fresh weight of severely burning leaves was somewhat lower, although no appreciable difference existed between those of slightly burning and healthy leaves. However, the water saturation deficit of burning leaves was apparently higher, even when they were slightly injured. There observed a significant linear correlation between affected area and water saturation deficit of burning leaves.
2. In order to determine the change of water content at localized areas of Bartlett pear leaves continuously, the beta ray gauging technique was attempted. In a preliminary examination with detached leaves, the log. of the relative intensity of transmitted beta rays increased linearly, as water content of the leaf decreased and water saturation deficit of the leaf increased. And among ¹⁴C, ¹⁴⁷Pm, and ²⁰⁴Tl used as the beta ray source, ¹⁴⁷Pm was the most suitable for measuring moisture change of Bartlett pear leaves.
3. Based on the result of the measurement of moisture content in the intact Bartlett pear leaf by the beta ray gauging technique, it was concluded that the relative intensity of transmitted beta rays increased prior to the occurrence of burning symptoms. This suggests that the leaf burn of the Bartlett pear is caused by dehydration of the leaf tissues.

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The present studies were carried out to ascertain the role of the leaves playing in the development of tomato flowers, especially that of the ovaries.
The mature leaves of tomato seedlings were removed alternately or successively from the first to the eighth node when they reached about 50mm in length respectively.
The defoliation of mature leaves retarded the development of flowers and this resulted in the formation of the smaller flowers with small sepals, petals, anthers and ovary. The sepals and the locules number decreased.
The new leaves were removed as they emerged, above the third node, counting from the base.
The defoliation of the immature leaves accelerated the development of flowers and this resulted in the formation of the larger flowers with larger sepals, petals, anthers and ovary. The sepals and the locules number increased.
The results showed that the flower development might be controlled by proper quantities of nutrient and/or hormonal stimulus supply following removal of mature or immature leaves. The defoliation of mature leaves decreased the elaboration of carbohydrates and induced carbohydrates shortage for the development of flower buds and this resulted in the formation of smaller flowers. On the other hand, the defoliation of immature leaves depressed the vegetative growth and the decrease of the demand due to the weakened vegetative growth for the nutrient supply, in its turn, favoured the surplus nutrient mobilization to the developing flower buds and this resulted in the fasciated flower formation.

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It is generally accepted that the population of subterranean micro-organisms having a direct concern with the nitrogen metabolism of plants grown in the sand is rather scarce as compared with those in ordinary farm soil, and the ammonification as well as the nitrification processes in sand, in consequence, has been considered to be generally small. For raising of plants in sand, therefore, it is quite necessary to make clear the nitrification processes which take place in the sand, and also to get more advanced knowledge concerning the fertilizing method of nitrogen in the Suna Saibai (a type of sand culture). In this connection, the author carried out studies on the nitrogen metabolism in the Suna Saibai, e.g., the influence of water content in the sand, of the concentration of nitrogen in the sand, and the effect of applying clay (bentonite) to the sand under 30°C constant temperature condition.
1. The ammonification and the nitrification in the sand took place quite sufficieutly. The nitrification of urea was detected 4 days after application.
2. The effect of the water content of the sand upon the ammonification was relatively small, and when the concentration of applied nitrogen was 125 or 333ppm, the ammonification at the 4th day attained ca. 65 to 85% of total nitrogen.
3. When the concentration of applied nitrogen was 125ppm, the nitrification was not influenced at all by the water content of the medium. The rate of nitrification per the total nitrogen attained ca. 95 to 100% at the 20th day. When it was 333 ppm the effect of the water content became detectable only after 12 days. The nitrification occurred earliest in the plot with a water content of 30ml per 150g of the sand, next in the plot of 20ml, and finally those of both 10 and 40ml. Namely, in the plots of 10, 20, 30 and 40ml water content, the nitrification attained to 35, 60, 70 or 40% on the 12th day and 60, 90, 95 or 60% of total nitrogen, respectively on the 20th day.
4. When the water content was the most favorable (30ml of water per 150g of sand, i.e., ca. 60% of the maximum water holding capacity), the ammonification and the nitrification were remarkably influenced by the concentration of applied nitrogen, and the higher the concentration, the later these occurred. The rates of ammonification at each level of nitrogen concentration (125, 250, 500 and 1, 000ppm) were 80, 65, 50 and 35% on the 4th day, and the nitrification on the 16th day was 100, 95, 70 and 50% respectively.
5. The added bentonite was refinitely effective in each of three different kinds of nitrogen levels, (250, 500 and 1, 000ppm), inducing good effect on the ammonification and the nitrification. In the case of 250ppm of nitrogen and 30ml water per 150g of sand, the effect of supplying bentonite at four different levels (0, 0.5, 1.5 and 4.5g) could be noticed on the 12th day after application when the population of soil organisms was considered to become sufficiently large. The nitrification rates on the 16th day were 45, 80 and 100%, respective to the increased application of bentonite upon pH was as follows: When 4.5g was added, pH was 7.2 at about 60% nitrification (on the 16th day). On the other hand, when the bentonite was not added at all, the pH value remained very low, being 4.6 at about 45% nitrification (on the 16th day). Thus the effect upon the ammonification, the nitrification and upon pH caused by the addition of bentonite was quite evident.

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Clivia miniata, native to Natal, is one of the valuable flowering pot plants in Japan. The plants are usually grown under glass during winter months and produce flowers in April. When the room temperature is raised by over-heating, they fail to produce flowers. It is known by our previous study that the flower initiation occurs in April and all florets in an inflorescence develop to the carpel primordia forming stage in October, but the flower do not unfold until the following Spring.
The authors assumed that the plant requires a certain duration of low temperature after that stage in order to elongate its scape and to produce normal flower.
The present study was conducted to clarify the effect of low temperature given after the completion of the floral organs on successive flowering.
1. When a plant was kept above 20°C continuously, the plant failed in the emergence of flower bud. Good flowering was obtained when a plant had received 50 days of natural cold under frost protection from the middle of January and again transferred to warm temperature above 20°C. The cumulative hours below 10°C during this cold period amounted approximately to 1, 000 hours.
2. In orders to determine the critical temperature for the chilling effect, plants were treated with constant temperature of 10°, 15° or 20°C for 60 days from the latter part of October and then were shifted to above 20°C. As a result, scape elongation and normal flowering were observed in plants treated at 10°C and not in those treated at 15°C. However, when the duration was shorter than 45 days, the chilling effects were insufficient even in the treatment at 10°C.
3. Insufficient chilling, either by imperfect degree or duration of cold, brought a check of scape elongation and, as the result, anthesis occurred in the low position being surrounded by the whorl of foliage leaves.
4. After the chilling requirement was fully satisfied and the flower bud just emerged, warm temperature promoted the subsequent flowering. Long days by supplemental lighting after shifting to warm temperature showed the compensatory effect for the insufficient chilling.
5. With the object to force the plant for Christmas flowering, chilling treatments at 10°C for 60 days beginning from August 20 and September 20 were given. The treatment from August 20 showed little effect on the flower development, whereas the treatments from September 20 brought a favourable effect and enabled to produce flower in Christmas. Treatment at 6°C in continuous darkness gave the similar effect as treatment at 10°C under light.

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An effect of low temperature on the flower bud formation in iris ‘Wedgwood’ is affected by the physiological condition of bulbs. In the present study, some factors influencing the response of bulbs to low temperature were examined.
In order to examine the effect of low temperature on the flower bud formation, the bulbs were treated with low temperature of 10°C for 20, 35 and 50 days from August 12, 27, September 11, 26 and October 11 respectively. Earlier flower bud initiation was observed in the bulbs which treated in earlier time when the duration of treatment was the same, though the speed of the development of flower bud was accelerated with the treatment in later time. When the treatment started on August 12, flower bud development was most advanced in the bulbs which treated for 50 days, while it was most advanced in the bulbs which treated for 35 days when the treatment started on September 11. The number of leaves formed before the flower bud formation was reduced with increasing duration of the low temperature treatment. When the same duration of the low temperature was given, a similar number of leaves was formed before the flower bud formation independently of the time of treatment; however, the number of leaves formed after low temperature treatment, before the flower bud formation, decreased as the time of treatment advanced. The growth of the first leaves was accelerated but ceased early when the low temperature was started on late time or the duration of the treatment was long.
In the bulbs which produced in warm, cool and cold regions in Japan and treated with low temperature at 10°C for 35 days, flower bud formation was advanced in those produced in warm region and was delayed in cold region. The rest period of those bulbs that not received the low temperature was differed by the difference of the regions where bulbs were produced, and the rest terminated early in the bulbs produced in warm region and late in those produced in cold region.
It was found that the bulbs whose scales were removed prior to low temperature treatment at 13°C for 45 days did not form flower buds, while those whose scales were removed after the treatment formed flower buds.
From the results above mentioned, it might be said that iris bulbs have become to form flower bud early with shorter treatment of low temperature as the age of bulbs advanced after the rest had terminated. On the flower bud formation, the difference in the response of bulbs, which produced in different regions in Japan, might be partly due to the difference in the rest periods of those bulbs. Scales might also have some influence on the flower bud initiation relating to the low temperature effect.

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In the previous paper the present writer reported that there are two thermo-reactive processes in corm formation of freesia, viz., the process of induction of physiological states for corm formation and the process of development of corm shown as the thickening growth of stem, and that the phenomenon in both cases resembles to vernalization in flower formation. This study was carried out to clarify the effect of the heat treatment after the chilling on the pupation of freesia employing cormlets of ‘Rijnveld′s Golden Yellow’.
When the freesia cormlets pretreated at 5° or 9°C for 20 to 40 days were subjected to the heat treatment at 25° to 35°C for 10 to 40 days, the percentage of pupation decreased as shown in Table 1 to 3. Therefore, it is sure that the high temperature above 25°C suppress the low temperature induction for corm formation, and that the higher the temperature and the longer the period of treatment, the more effective it is for the suppression.
When the cormlets were subjected to the chilling at 9° or 5°C for 102 long days, the pupation was scarcely suppressed by the heat treatment at 30°C for 20 to 30 days.
In this experiment the cormlets, pretreated by low temperature and then stored under neutral temperature of 20-21°C for 10 to 30 days, were subjected to the heat treatment at 30°C for 20 to 30 days. In the cormlets mentioned above the suppression for pupation was less than that of cormlets treated with high temperature just after the chilling treatment. Therefore it is sure that the physiological states for corm formation is stabilized under 20-21°C storage for 10 to 30 days.
The heat treatment given prior to the chilling was effective for the pupation and the percentage of pupation decreased according to the degrees of the induction for corm formation.
In the fifth experiment the cormlets, the chilling induction of which was vanished by the heat treatment, were subjected again to low temperature of 9°C for 30 days. It showed that the cormlets subjected again to the chilling treatment formed new corms.
From the results of investigation in these experiments it seems that the physiological states for corm formation which were induced by the chilling and vanished by the heat treatment are only quantitative and reversible within a certain range.
The aforesaid phenomena in corm formation of freesia resemble to vernalization, devernalization and revernalization in flower formation.

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In order to make clear the effect of light quantity on anthocyanin formation of carnation flowers, some experiments using detached petals just before pigmentation were conducted under various conditions of artificial light. The detached petals were cultured in medium of glass wool soaked with 4% sucrose solution.
Both growth and anthocyanin content of the cultured petals reached to peak on 16 to 20 days after the beginning of culture.
Efficiency of the anthocyanin formation per radiant energy during the culture increased as the petal grows and reached maximum in the petals of about 12th day after the beginning of culture.
The width of petals and the amount of anthocyanins increased with the increase of either light intensity or light duration, but the growth of petals in width was remarkable at lower intensity.
The saturation .of anthocyanin formation was attained at the irradiation of about 8, 000 lux in light intensity.
In the case of irradiation in which total amount of radiant energy as adjusted to be equal, the combination of low intensity and long duration resulted higher value in the anthocyanin formation than that of inverse condition, and short cyclic irradiation was more effective in the anthocyanin formation than long cyclic irradiation.

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A mechanism of rest of vegetative bud, a developmental process of flower bud and an effect of chilling on sprouting and flowering in some ornamental trees and shrubs have been studied by the authors since 1968 with the object of controlling a flowering of the plants.
The experiment presented here was taken to clarify the above problems in dwarf ornamental peach ‘Amendo’ (Prunus persica SIEB. et ZUCC.) generally grown as a pot plant. The results obtained are summarized as follows:
1. Under natural environment, vegetative buds began to rest in early September, and the rest became deepest from late November to late December. The buds emerged from the rest from late December to early January.
2. It required 6 weeks of low temperature (0°-5°C) to break the deep rest of vegetative buds. The buds in early or late stage of the rest became to resume growth after 2 to 4 weeks of the low temperature, and the result suggests that they have less cold requirement than those in the deep rest.
3. Flower initiation occurred in axillary buds of current-year shoots in mid September, and sepals and petals in the flower buds were formed from late September to early October. Pistil formation, started in late October, was completed in late November. After that, the flower buds discontinued development and remained at the completion stage of pistil until mid February or later.
4. When plants were exposed to low temperature (0°-5°C) for 6 weeks after the completion of pistil and thereafter were shifted to high temperature (15°C or above), the flower bud resumed development and grew well into flower. Low temperature treatment given before pistil formation was ineffective on the ripening of flower buds.
5. When plants were stored at 0°-5°C for 6 weeks from late November and then forced at minimum night temperature of 15°C, flowering pot plants of commercial value were produced in late January to early February. Potted plants, which were placed outdoors until mid January or later and then were transferred into greenhouse kept above 15°C without additional chilling, took flowers within 4 weeks after the transferance.

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The quantity of aluminum and phosphorus contained in Hydrangea macrophylla DC. changes from the raising period to the flowering time. The present investigation was undertaken to make clear the feature of this change and its influence on sepal color, using the scarlet-flowered cultivars ‘King George’ and ‘Prima’.
During the raising period from June to December prior to forcing, the potted plants were grown in acid soil of pH5.7, prepared by mixing equal parts of red loam (Kanto-loam) and well-decayed manure. The considerable amounts of aluminum and phosphorus were absorbed and accumulated during this raising period, but the large portion of them, i.e. 70-80 per cent of total amount was lost through the defoliation in late fall. On December 12, the amount of aluminum in ‘King George’ and ‘Prima’ was no more than 0.55mg and 0.707mg per plant, respectively.
On December 25, the plants were divided into two different soil plots. One plot was repotted with the acid soil of pH6.05 similarly prepared to the soil previously used and the other with the alkline soil of pH7.50 prepared by addition of calcium hydroxide to the sandy loam soil. All pots were then transferred to a greenhouse and forced at the temperature of 15-25°C until flowering.
The sepal color of plants grown in the alkaline soil during the forcing period was clear scarlet, while the color of these in the acid soil was dark blue or mauve. Absorption maxima of spectra of the blue sepals were 557mμ in ‘King George’ and 582mμ in ‘Prima’, whereas those of the scarlet sepals were 532mμ and 540mμ, respectively. Moreover, the distribution of spots of the scarlet sepals on Hunter′s color diagram was clearly separated from those of the blue sepal.
The concentration of aluminum in each plant part, in particular in flower part of those grown in the acid soil, was much higher than that in the alkaline soil. The values of the former were 985ppm and 1, 258ppm, and those of the latter were 430 ppm and 335ppm for each variety. By contrast, the concentration of phosphorus absorbed was inversely correlated. It was much lower in the acid soil plot as compared with alkaline soil plot. The ratios of the concentration of aluminum to phosphorus of ‘King George’ and ‘Prima’ in the acid soil were 0.334 and 0.434, whereas those in the alkaline soil were only 0.106 and 0.094 respectively.
Furthermore, the concentration of water soluble aluminum in plants, which plays presumably an important role for the formation of the blue aluminum-anthocyanin complex, was much higher in plant of the acid soil plot than in the alkaline soil. The percentages of it to total aluminum in flower part were 27-38 per cent in the acid soil and only 7-8 per cent in the alkaline soil.
On the basis of these evidences it was considered that, within plants, some of aluminum absorbed is combined with phosphorous and turns into insoluble compound and, in addition to this change, the much less absorption of aluminum in the alkaline soil may prevent the formation of blue aluminum-anthocyanin complex, thus leading to the clear scarlet color.

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The process of development of gladiolus corms was studied by histological procedures.
Cormlets of cv. ‘Traveller’, the average weight of which was about 0.3g, were planted on April 22, and were sampled at weekly intervals until September 11. At each sampling date, a batch of 10 corms was fixed and examined microscopically.
The results of investigations are summarized as follows:
1. In the rest period, the mother cormlet had three sheath leaves and one foliage leaf of 1-1.5mm long in its main bud. After growth of one week, origination of daughter corm was brought about by the thickening growth of internodes between the outermost sheath leaf and the first foliage leaf.
2. In early stage of growth, for 9 weeks after planting, the development of daughter corms depended mostly upon cell multiplication in cortex and stele. In the next stage, from the 9-th to the 14-th week after planting, thickening growth was caused by cell division in the cortex and cell enlargement in cortex and stele. After the 14-th week, in the third stage, corm enlargement was mainly depended upon enlargement of cells in the cortex.
3. Increase in the number of cells at the initial stage of corm development was brought about by the activity of the apical meristem. On the contrary, successive thickening growth was caused by actively dividing cells which diffused in permanent tissues of daughter corms. Both chromosomes and storage starch grains were found simultaneously in the mitotic cells. These dividing cells did not form any meristematic tissue, but diffused in permanent tissues of cortex and stele.
4. These facts show that the pattern of thickening growth of gladiolus corms is “diffuse thickening growth”, which is one of the thickening growth patterns observed in monocotyledons.

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Experiments on seed germination of some palms (Cocos nucifera, Phoenix humilis var. hanceana, and P. sylvestris) were carried out during 1968 to 1971.
(1) The fruit of Cocos nucifera has a hard endocarp which is surrounded by the thick fibrous mesocarp. However, endocarp is slightly thin around the germination pore. The uppermost part of cotyledon remains inside the seed after germination and absorbs nutrients. Then, it grows to fill up the cavity of the seed. On the other hand the plumle and radicle, which escape from the hard inner coat, break the exocarp after the growth in the fibrous layer of the mesocarp. The distance from the coleoptile enclosing the growing point to the haustorium body remaining in the seed is very short. The germination process of the other two Phoenix species is similar to that of Cocos nucifera, but the cylindrical coleoptile lies at a certain distance from haustorium body.
(2) 80% germination was the maximum at 35°C and 60% at 30°C in Cocos nucifera. And the maximum germination was 92% and 80% at 30°C in Phoenix humilis var. hanceana and P. sylvestris respectively.
(3) The optimum temperature was 30 to 35°C for the seed germination of Cocos nucifera and Phoenix sylvestris, while it was 30°C for P. humilis var. hanceana.
(4) The minimum number of days to the germination was 107, 25 and 15 in Cocos nucifera, Phoenix humilis var. hanceana and P. sylvestris, respectively.
(5) The most preferable medium for seedage was vermiculite or sand in Phoenix humilis var. hanceana. However, there was no difference among the mediums for seedage in P. sylvestris.

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A research work was conducted to find out the ability of pH meter value applying simplified physical method in stead of a chemical method applying the titrated acid contents in Satsuma mandarin fruit.
Then nitrogen, phosphate, potassium and combined acid contents in fruit juice were measured to research the causes of their dispersions as well as a relation of pH value and titrated acid contents, and an analysis of these relations was tried.
In addition to that, in order to know if sense factor to acidity is influenced by pH or by free acid contents, citric acid and potassium citrate were mixed and the organoleptic test was carried out. And the relation of acidity between pH and free acid contents was investigated.
The results were as follows:
1. In case of applying the regression straight line and the second regression curved line to estimate free acid contents from pH value, an error of about ±0.2-0.3% acid contents was measured. Therefore it is difficult to estimate exactly the relation.
2. A high positive correlation coefficient in the regression line was recognized in the relation between pH value and combined acid contents/free acid contents.
In any area or strain of satsuma mandarin, the slope and the constant articles agreed almost respectively.
3. The residual free acid % in the relation of pH and free acid contents was larger in order of phosphate, nitrogen, potassium, combined acid and particularly when the combined acid, potassium contents were increased, the positive residual was caused, and when they were decreased, the negative residual was given rise.
4. A high positive correlation was obtained between the combined acid contents and the potassium contents. Particularly in sweet summer orange the correlation coefficient was 0.922.
5. A low negative correlation was obtained between the free acid and nitrogen contents. The free acid contents could only explain as much as about 23% (at the coefficient of determination R²=0.233) in N, P, K contents in fruit juice.
6. Particulary 0.64, a high positive correlation coefficient value was obtained between pH and nitrogen contents.
The determination coefficient of 0.51 for pH value was obtained by nitrogen, phosphate and potassium contents, therefore pH value could explain about a half by the nitrogen, phosphate, potassium contents.
7. At the same citric acid content, when citric potassium was added more, the acidity was softened a little.
At the same pH value, high citric acid contents strengthened acidity naturally.
So far as this experiment was conducted, even if pH value was changed by additional citric acid potassium, the influence of the free acid contents on acidity was greater than that of pH value.

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Citric acid metabolism in Satsuma mandarin fruits (Citrus unshiu MARCOVITCH, cv. KATAYAMA) with or without curing was investigated during 90 days by injecting with citrate-1, 5-¹⁴C (0.1μCi, pH 3.5) into the fruit segments.
1. It was found that the injected citrate-¹⁴C was readily translocated to the areas of peel which was in contact with the injected segment. No radioactivity was found in all segments except the injected segment of the fruit throughout the storage period.
2. The content of titratable acid in each segment of a fruit continued to decrease independently during storage. Therefore it made a great difference in the titratable acid content in each segment of a fruit at the end of storage.
3. The cumulative radioactivity of respired ¹⁴CO₂ continued to increase after injection with the substrate and the curve leveled off within 10 days. The cumulative radioactivity evolved by cured fruits was lower than that of non-cured fruits during 10 days after injection.
4. The injected citrate-¹⁴C was decarboxylated rapidly within 10 days and the radioactivities in ethanol soluble fractions in the peels and pulps decreased gradually for the subsequent 80 days.
It may be concluded that the endogenous acids or their salts in the vesicles of the segment were not translocated into another segments and were catabolized in si-tu during storage of Satsuma mandarin fruits.

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It has been known that eggplant fruits show the typical symptoms of chilling injury when they are stored at low but non-freezing temperature. Using this material authors have been studying the mechanism of chilling injury, and the present paper reports a general aspect of the occurrence of injury and a microscopic observation of the pitting development. Cultivar ‘Senryo’ was mainly used and stored at 1°, 6°, 10° and 20°C in perforated polyethylene bags.
The fruits harvested in July showed a severe pitting at 1° and 6°C, and transferring of low temperature-stored fruits to 20°C hastened the development of the injury. At 10° and 20°C of storage temperature no pitting was found. When low temperature-stored fruits were transferred to 20°C rapid decay developed starting mostly with calyx part. The incidence of the decay was faster in the fruits stored at low temperature for longer period, while the storage within 3 days at 1°C did not show effect. Even 10°C of storage temperature showed a negative effect when the fruits had been kept for 5 days or more, and the fruits transferred to 20°C decayed more rapidly than that stored at steady 20°C.
In the fruits harvested in October, no pitting was found during the storage at 6°C and after transferring from 6°C to 20°C. The calyx decay, too, delayed as compared with the fruits harvested in July. Some other observations, using cultivars other than Senryo, also suggested that the fruits harvested in cool season are less sensitive to low storage temperature.
Considering the incidence of decay at the elevated temperature, storage temperature above 10°C is recommended for the fruits harvested in warm season, while 10°C or below may be preferable for the cool season fruits.
Under the microscope it was found that the pitting injury commenced with deformation and browning of the cells which locate several layers inside surface, and the water loss from the surface had no relation to the pitting at the first stage of the injury development.

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