Two-year-old trees of ‘Miyagawa Wase’, an early maturing variety of satsuma mandarin, were planted in 1967 at various planting densities, and grown under different cultural treatments until they were 19 years old. Planting densities were 1, 250, 2, 500, 5, 000 and 10, 000 trees/ha. Cultural treatments were shallow plowing+less fertilization, deep plowing+standard fertilization, with either no pruning+no fruit thinning or pruning+fruit thinning. Effects of planting density and cultural treatment on leaf area index (LAI) were determined from data obtained during the period from 1969 to 1984 (tree age 4-to 19-year-old). LAI which gave a maximum yield was determined at each tree age, and the relation between LAI and yield was also examined. Results and conclusions were as follows: 1. The shallow plowing+less fertilization showed a slightly lower LAI level than the deep plowing+standard fertilization. The no pruning+no fruit thinning showed a slightly higher LAI level than the pruning+fruit thinning. 2. LAI increased with tree age at each planting density, and the higher the planting density, the larger the rate of increase became. After LAI had reached a maximum at each planting density, it levelled off with a large yearly fluctuation in higher planting densities. Average LAI for the levelled off values were 6.0 at 1, 250 trees/ha plot, 6.7 at 2, 500, 8.0 at 5, 000, and 8.7 at 10, 000. Thus the higher the planting density, the larger the LAI became. 3. The average maximum yield for all tree age (4-to 19-year-old) was 67t/ha, and average LAI which gave it was 6.7. Yield per unit leaf area was 1kg/m2. 4. The optimum LAI which gave the highest yield (74t/ha) was estimated to be 6.7 in the lower planting density.
Total, free, and combined acidity of fruit rind were determined on 85 samples from 70 citrus species, to reveal their genetic variations. Free acidity of rind in most samples was below 17me/100g. Total acidity of rind in all samples lay between 4 and 23me/100g. The percentage of free acidity in total acidity was between 12 and 39% with two exceptions of 45% and 58%, and the average of all samples was 22%. Combined acidity in most samples was between 3 and 11me/100g. However, that of nine samples, namely Funadoko, Yuzu, Dancy tangerine, Jimikan, Rusk citrange, Mediterranean mandarin, and Miyauchi Iyo excceded 11me/100g, up to 23.2me/100g. There were high correlation coefficients among the three acidities within each group of samples. However, when all samples were observed as a whole, free acidity and combined acidity did not correlate significantly. Total, free, and combined acid content of rind per fruit were very high in Pummelo, which has the maximum weight of fruit and rind. Sudachi with the minimum weight of fruit and rind showed the lowest content of total, free, and combined acids. Acid content tended to be higher in species with heavier fruit weight and rind weight. However, the proportion of acid in rind to acid in whole fruit had no correlation to proportion of rind weight to whole fruit weight. The acid content of rind in relation to that of whole fruit was 0.8-47.5% for free acid, 2.3-48.7% for total acid, 18.0-72.5% for combined acid. Therefore, in order to get an accurate physiological understanding of the organic acids of citrus fruits, the total, free, and combined acid content of rind tissues should also be determined when estimating those of the whole fruit.
Effects of foliar spray of 6-Benzylamino purine (BA) on the acceleration of axillary bud sprouting in satsuma (Citrus unshiu Marc. ) trees were examined to establish feasible citrus production systems necessary for year-round fruit shipment. The results obtained are as follows: 1. Meteorological conditions, i.e., duration and intensity of illumination, ambient temperature and relative humidity of the air, were regulated within the regimes favorable to shoot growth in phytotrons. Under such conditions, two successive applications of aqueous BA solutions (pH 6.8) to satsuma trees at concentrations of 100 and 200ppm at an interval of four days resulted in consistent acceleration of axillary bud sprouting. 2. The lower the ambient temperature, the greater the time lag in axillary bud sprouting, and also the slower the elongation of sprouted shoots. 3. The effect of BA on the axillary bud burst was greater when applied during naturally quiescent periods than when applied during growth flushes. It was also greater in spring than in summer. In particular, sprouting percent of BA-treated buds was about six times that of untreated buds when BA was applied at a scheduled time of heating in plastic greenhouses for early fruit shipment. 4. BA application did not induce sprouting of immature axillary buds located at basal node positions of the shoot. 5. When axillary buds sprouted luxuriantly on each shoot of the tree, some of them abscised. This may be caused by severe competition for nutrient between laterals. The abscission of such devitalized shoots implies the importance of suitable distribution of nutritive substances in a tree.
The occurrence of ‘Rind yellow spot’, a physiologial disorder of ‘Naruto’ (Citrusmedioglobosa Hort. ex Tanaka), which appears during maturation period, was studied in relation to time of flowering and position of fruit in the tree canopy. Gibbrellic acid (GA3) spraying and shading treatments were also performed to reduce the disorder. 1. Fruit developed from flowers opening early in the season matured earlier than those from late-opening flowers, and consequently were more susceptible to the disorder. 2. GA treatment of young fruits in mid-June considerably reduced the occurrence of the disorder, with only a slight delay in fruit coloration and a reduction of acid concentration. 3. The occurrence of the disorder was greater for fruits harvested from east-south side, upper parts or outside of the tree canopy, than those harvested from west-north side, lower parts or inside. 4. Shading treatment with cheese cloth during furit development reduced the incidence, although it also slightly decreased fruit growth and delayed coloration.
In vitro conditions for germination and pollen tube elongation of freshly collected and stored kiwifruit pollen were studied. 1. The optimum temperature for the germination of fresh pollen was 30°C; whereas that for tube elongation was 25°C. 2. The optimum sucrose concentrations in the medium ranged from 5 to 15% for pollen germination and tube elongation. Glucose and fructose were inferior to sucrose under the same conditions. 3. The optimum pH for pollen germination and tube growth was 4.0. 4. Additions of boric acid (2 to 1, 000ppm) to 1% agar medium, adjusted to pH 5.5, and containing 10% sucrose accelerated pollen tube growth. 5. Kiwifruit pollen remained viable two weeks when stored at 4°C with silica gel as a desiccant. Pollen preserved in hexane at 4°C retained a high germination capacity even after one year.
IAA (indole-3-acetic acid) added to MS (Murashige and Skoog) medium was quantified by HPLC (high performance liquid chromatography) during storage of the media under various conditions. Illumination (5, 000lx) of the media with fluorescent white lamps degraded IAA significantly, but temperature treatment (25°C) under the dark condition had no strong effect on IAA degradation. Under the light conditions (5, 000lx) at 25°C where in vitro rooting and shoot growth of Musa apices were enhanced well by adding IAA, the amount of IAA decreased papidly and almost no IAA was detected 8 days after treatment. The effect of IAA on morphogenesis of Musa apices was clearly observed in the present study. These facts suggest that shoot apices of Musa on the media absorb and use IAA at initial times after inoculation.
Activities and roles of the sorbitol-related enzymes, NAD+-dependent Sorbitol dehydrogenase, sorbitol oxidase, NADP+-dependent sorbitol dehydrogenase and sorbitol-6-P dehydrogenase, and acid invertase were studied in Japanese pear (Pyrus serotina Reder var. culta Rehder) fruit. NAD+-dependent sorbitol dehydrogenase that converts sorbitol to fructose had the highest activity of the 4 enzymes throughout the developing season. The activity rose in June, decreased with fruit expansion, and increased again with fruit maturation. Fluctuation in the enzyme activity correlated with the accumulation of fructose in immature fruit. This enzyme was suggested to be important for sorbitolmetabolism and sugar accumulation in Japanese pear fruit. Sorbitol oxidase activity, which was about one-tenth that of NAD+-dependent sorbitol dehydrogenase, had high activity in immature fruit, decreased with fruit expansion and increased again with fruit maturation. Sorbitol-6-P dehydrogenase and NADP+-dependent sorbitol dehydrogenase activities were detected a little. The differences in sorbitol metabolism among Rosaceae plants were discussed, based on the seasonal fluctuations of these enzyme activities. Acid invertase activity was distinctly higher than that of sorbitol-related enzymes in fruit, and its role in sugar translocation and metabolism was discussed.
The mineral nutrient absorbency among 6 different rootstock species (P. persica Batsch., P. tomentosa Thunb., P. japonica Thunb., P. glandulosa Thunb. and P. triloba Lindl.) was tested by sand culture and the influence of these rootstock species on the mineral nutrient contents in scion leaves was investigated with ‘Okubo’ peach, ‘Okitsu’ nectarine and ‘Oishi-wase’ plum trees under field condition. 1. In 6 rootstocks propagated by cuttings, P, Ca and Mg contents in leaves of P. persica were higher than in the other rootstocks. K content in leaves of P. japonica and P. glandulosa was lower than in P. persica while that of P. triloba was higher than in P. persica. Mn content in leves of P. tomentosa, P. japonica and P. glandulosa was higher than in P. persica. 2. In ‘Okubo’ peach, ‘Okitsu’ nectarine and ‘Oishi-wase’ plum grafted on several rootstocks, the mineral nutrient component of their leaves reflected the absorbency of rootstocks accurately. Mn content in leaves of ‘Okubo’ peach trees grafted on P. tomentosa, P. japonica, P. glandulosa and P. toriloba was higher than in trees grafted on P. persica. In ‘Okitsu’ nectarine and ‘Oishi-wase’ plum trees grafted on P. tomentosa and japonica, Mn content in the leaves was excessively higher than that of trees on P. persica. K content in leaves of ‘Okubo’ peach, ‘Okitsu’ nectarine and ‘Oishi-wase’ plum trees grafted on P. japonica was lower than others and Mg content in trees grafted on P. tomentosa was lower than in others. 3. Abnormal leaf rolling or leaf senescence was observed with ‘Okubo’ peach trees grafted on P. japonica, and ‘Okitsu’ nectarine trees grafted on P. tomentosa or P. japonica.
Japanese persimmon cv. ‘Nishimurawase’ is a pollination variant non-astringent(PVNA) type, and de-astringency has not been achieved along with decreased capability of seed formation. This decreased capability has been researched from the point of view of male gamete sterility, germination percentage and germination rate of pollen, previously. In this paper, the development of embryosac from the mother cell to complete formation was investigated in order to understand the relationship between capability of seed formatiom and female sterility. Embryosac mother cells and tetrasporangii were formed 18 and 12 days before bloom. The embryosac reached maturity 4 days before bloom. There were 3 phases in the development: the first phase, characterized by extension and no enlargement, extended from embryosac mother cell to tetrasporangium, the second phase, characterized by rapid enlargement, extended to the nuclear division of embryosac cells, and the third phase, characterized by rapid extension, extended to completion of the embryosac. Embryosac abortion and degeneration were observed, at rates reaching 22.5%, after the tetrasporangium or embryosac cell formation phases. There might be only six fertile embryosacs in a ‘Nishimurawase’ fruit judging from the percentage of embryosc abortions and degenerations.
Callus formation and plant regeneration from leaf mesophyll protoplasts were examined with 3 vareties of Chrythanthemum moriforium, 1 variety of C. coronarium and 3 varieties of Lactuca sativa. The protoplasts were isolated by incubating eaf slices in an enzyme solution containing 1% Cellulase Onozuka R-10, 0.2% Macerozyme R-10, 10% mannitol and 0.1% CaCl2• 2H2O(pH5.5) for 16 hours at 25°C without shaking, and cultured in modified Murashige and Skoog′s medium. During a culture period, cultures were diluted with an equal volume of fresh medium once a week. This treatment was essential for sustaining cell division and colony formation. Callus formation was found in C. moriforium and L. sativa, but in C. coronarium, cell division could not be induced. Callus formation of the former two species was influenced by nitrogen sources. Callus formation of C. moriforuim was inhibited by NH4NO3 and stimulated by Ca(NO3)2•4H2O. On the other hand, the contrary tendency was found in L. sativa. Shoot buds were induced by transferring callus of L. sativa onto regeneration medium containing 0.5ppm NAA and 1.0ppm BA. The frequency of shoot regeneration was different among 3 varieties of L. sativa. In one variety, Akachirimenchisha, shoot buds were regenerated from all calluses.
In growing Japanese radish cv. ‘Gensuke’ during summer, “hollow root”-lengthwise hollowness in the central portion of the root-frequently occurs, which has been attributed partly to high soil temperature. In these experiments, effects of heating and cooling the soil at specified stages of the plant′s growth on the weight increase of the root and the occurence of hollow roots were investigated. 1. In the heating experiments, plants were subjected to soil-heating treatments for 15 days and to soil-cooling treatment for the other 45 days. During the heating period, weight increase of the roots was slowed with one exception, while the occurrence of hollow roots was conspicuous when plants were subjected to heating during the first and second 15 days after sowing. 2. In the cooling experiments, plants were subjected to soil-cooling treatment for 15 days and to soil-heating treatment for the other 45 days. Weight increase of the roots for 15 days was notably accelerated when they were subjected to cooling treatment during the second 15 days after sowing, and the occurrence of hollow roots was low. From these results, following conclusions were drawn: the formation of secondary meristems in the central portion of the root is strongly influenced by the soil temperature, particularly from the 16th day to the 30th day after sowing; high temperature during that time tends to hinder that formation. Consequently, lysigenous intercellular spaces developed in the central portion of the root are not filled with parenchymatous cells, derived from the secondary meristems, thus causing high occurrence of hollow roots as was observed in the heating treatment during the same period.
Photosynthesis and translocation and distribution of photosynthates in ‘Donner’ strawberry plants were investigated, extending from the stage of vegetative growth to that of imposed dormancy. 1. Photosynthetic capacity of individual leaves decreased little until the deepest stage of true dormancy, as compared with the stage of vegetative growth. While, photosynthetic capacity of intact plants at and after the deepest stage of true dormancy decreased to one third or lower of that at the vegetative stage. This decrease was almost parallel with that of total leaf area. The contribution rate of each of the 3 upper unfolded leaves, except the uppermost one, was 20-25% and higher than the rates of the lower leaves. 2. When plants were kept for 15h in a glasshouse without heating after being fed with 14CO2, respiratory loss of assimilated 14C decreased gradually from 70-54% at the stage of vegetative growth to 31% at the stage of imposed dormancy. Also, the total accumulation and translocation of 14C into sinks decreased from 21 and 45% at the stage of induction of dormancy to 15 and 22% at the stage of imposed dormancy. When plants were kept at 18°C after feeding, the values of such parameters changed little with the time of feeding. 3. The distribution pattern of 14C was affected little by the temperature during translocation, and seemed to be influenced mainly by the relative strength of sinks. Thus the percentage distribution to young leaves was high during vegetative growth and decreased towards the stage of imposed dormancy, while the percentage distribution to the roots changed inversely to that at the vegetative stage. In bearing plants, however, flower clusters behaved as stronger sinks than roots. 4. Amounts of 14C accumulated in the respective sinks were influenced mainly by the total 14C assimilated by the source leaf, rather than by the percentages accumulated or distributed to the sinks. Thus 14C was accumulated in large quantities in the respective sinks from the stage of vegetative growth through induction of dormancy, when 14C accumulated in the leaves exceeded that in the roots, reaching about half of 14C assimilated. But at and after the deepest stage of true dormancy, when total accumulation decreased, 14C accumulated in the leaves decreased markedly, while nearly half of the total was still distributed to the roots.
Right- and left-handedness in phyllotaxis was observed in 6 varieties, which belong to 6 species in 4 genera of Solanaceae plants. Seedlings with right- and left-handed phyllotactic spirals in the main stem were almost equally frequent. Relationships between the right- and left-handedness of phyllotaxis and flower arrangement on the inflorescences in egg plant were observed to be the same as in tomto. On plant of left-handedness, the first five flowers developed to the left, right, left, right and left sides from the inflorescence axis, respectively. On plant of right-handedness, the reverse was true. It was reconfirmed by SEM observation that flowers developmental order and arrangement in the first inflorescence of tomato plant were the same as reported in a previous paper (9). From these observations, the fundamental inflorescence type of tomato and egg plant was recognized again as scorpioid cyme.
When stigmatic sap or stylar sap collected by centrifugation was placed on the stylar canals of bisected pistils of Lilium longiflorum, or when pollen grains were pre-soaked in the stigmatic sap, growth of pollen tubes in the style was accelerated even inn self-combination. When stylar sap collected from cross-pollinated styles was placed on the stylar canals of the bisected pistils, the growth of incompatible pollen tubes was significantly promoted more than by the placement of the sap from non- or self-pollinated styles. Changes in constituents of the stylar sap after pollination were also examined. Protein content in the sap decreased in the upper 4/5 of the style in 24 hrs after pollination. Stylar sap eluted through Sephadex G-150 column showed two peaks of carbohydrates, i.e., a broad band of high molecular weight and a narrow band of low molecular weight. After cross-pollination, both peaks were lowered, while after self-pollination only the peak of low molecular weight was lowered. These results suggest that the movement of stylar sap from the stylar tissue to the stylar canal is different between self- and cross-combinations, and that the inhibitory substance for the pollen tubes is absent even in self-combination, and that certain proteoglycans are related to self-incompatibility.
Time of flower bud differentiation in 18 lily species native to Japan was surveyed and the species classified into 4 groups as follows. Type 1-a. L. rubellum and L. dauricum. Flower buds were initiated in early fall and completed in early winter within bulbs, before sprouting. Type 1-b. L. concolor var. pulchellum (Chosenhimeyuri), L. japonicum, L. maculatum (native to Sadoga-shima) and L. hansonii. Flower buds were initiated in late fall within bulbs, before sprouting and completed next spring when the plants sprouted from the ground. Type 2-a. L. longiflorum, L. alexandrae, L. nobilissimum, L. speciosum, L. auraturn, L. platyphyllum, L. leichtlinii var. maximowiczii, L. medeoloides, L. callosum, L. brownii, L. concolor (Tosahimeyuri) and L. maculatum (native to Miyake-jima). Flower buds were initiated just after sprouting. Type 2-b. L. lancifolium and L. henryi. Flower buds were initiated about one month after sprouting.
Bulbs of ‘Blue Magic’ were exposed to ethylene at different times following harvest to investigate effects of ethylene on dormancy breaking and flowering. When bulbs were in a state of dormancy, ethylene showed a slight promotive effect on their sprouting but little effect on flowering. After bulbs experienced high temperature and their dormancy was broken, ethylene increased markedly the flowering percentage, even when using bulbs of 7cm size which were too small to induce flower buds. Ethylene may cause non-dormant bulbs, emerged from dormancy, to progress from a juvenile phase into the stage of ripeness to flower and thus augment the accelerating effects of low temperature following ethylene treatment. As a result, high flowering percentage can be obtained in early forcing of Dutch iris.
Tne effect of plant density on the growth of seedlings of Spiranthes sinensis Ames and Liparis nervosa Lindl. in symbiotic cultures with Rhizoctonia isolates, effective for these orchids, was investigated using an oat medium containing the decoction of 25g/l oat grains and 1% agar. In high plant densitis, the weigth of individual seedlings increased in proportion to the quantity of medium per plant, but the rate of fresh weight increase was lowered with a decrease in plant density. The point where maximum fresh weight per individual seedling was obtained, i.e. the threshold where the density effect disappeared, was at a very low plant density: 60ml/plant for S. sinensis and 30ml/ plant for L. nervosa. The dry weight of mycelia per culturing flask also increased wich a decrease of plant density. It is considered that the effect of plant density on the growth of seedlings is, with respect to the oat medium, mainly dependent on the amounts of nutrients in the medium. Competition among aerial parts did not take part in the effect.
This study was undertaken to compare growth and nutrient uptake of Cattleya hydrid, Lc. Pacific South×Bc. Deesse, grown with different composts and fertilizers. 1. Cattleya plants showed good growth by customary practice, i.e., potting in sphagnum moss with 3 applications of 2.5g of rapeseed oil cake+bone meal (1:1, v/v) mix (376.5mg nitrogen). The ratios of uptake to application of nitrogen, phoshorus, potassium, calcium and magnesium were 19.3, 2.7, 149.7, 16.5 and 85.2%, respectively. 2. Cattleya plants, grown in Bora (pumice)+peat moss (1:1, v/v) mix and given 3 applications of 2.5g of rapeseed oil cake+bonedmeal (1:1, v/v) mix (376.5mg nitrogen), also showed good growth. 3.Cattleya plants were grown with nutrient solutions of various concentrations. Concentrations of nitrogen, phosphorus, potassium, calcium and magnesium in standard nutrient solution were 231, 46.5, 117.3, 80.1 and 12.2ppm, respectively. Cattleya plants, grown in Bora+peat moss (1:1) mix and given 20ml of standard nutrient solution weekly 40 times (184.8mg nitrogen), equaled those by customary practice in growth. The ratios of uptake to application of nitrogen and phosphorus were 45.9 and 39.80, respectively. The ratios of potassium, calcium and magnesium were 226.6, 208.8 and 804.30, respectively. Concentrations of potassium, calcium and magnesium in the standard nutrient solution used in this study seemed to be low for growth of Cattleya plants as compared to those of nitrogen and phosphorus. A concentration of one third of the standard nutrient solution was inadequate for growth of Cattleya plants. 4. Cattleya plants, grown in hemlock and given 20ml standard nutrient soultion weekly 40 times (184.8mg nitrogen), equaled those by customary practice in growth. The ratios of uptake to application of 5 elements were similar to those in plants grown in Bora+ peat moss (1:1) mix and given standard nutrient solution. 5. Up to 43% of the potassium present in the whole plant was found in the lead bulb (new leaf+new pseudobulb). It may be considered that applications of rapeseed oil cake+bone meal mix alone are inadequate for good growth of a Cattleya plant, because the rapeseed oil cake+bone meal mix contains a low percentage of potassium.
The value of Agapanthus africanus as cut floweres has recently been recognized. There is now a need to study how to force the flowering time. In this study, the growth periodicity of plants grown outdoors was clarified and the effect of temperature on the initiation and development of flower buds was investigated. Shoot apices of plants grown outdoors were in the vegetative state in October and began to flatten and broaden in middle or late November. Following the initiation of spath leaves at year end, the growth of the apices ceased until early March, when the initial of first floret appeared. In early May, the first floret of an inflorescence reached the carpel primordia stage and the flower bud appeared outward amid the whorl of foliage leaves. Pollen formation occurred in early or middle June and anthesis was completed at the end of June. Although flower formation was inhibited when the plants were placed at or above 20°C from September onwards, shifting to 10°C or 15°C caused them to initiate flower buds. After flower initiation, the higher temperature resulted in earlier flowering, accompanied by some depression in flower size and scape length. In a trial for commercial forcing, cropping of flowers in March, 3 month earlier than the natural flowering time, was attained by keeping plants at min. 20°C from the end of November onward. Application of long days of 16 hours, in addition, advanced the flowering.
The yearly trend of seasonality of fresh fruit consumption was analyzed, using the Annual Reports on “The family income and expenditure survey” (1963-1984), issued by Statistic Bureau, Management and Coordination Agency, Japan, by a statistical method which was newly developed in our previous paper. Following to the analysis, the yearly trend of monthly relative consumption was also analyzed by the maximum marginal likelihood method for smoothing serial data in order to estimate the main factors responsible for the change of seasonality of fresh fruit consumption. Seven fruit species analyzed included satsuma mandarin, apple. Oriental pear, peach, persimmon and Natsudaidai. Results obtained are as follows; 1. Current seasonal concentrations of fresh fruit consumption were confirmed to remain extremely high, with peach taking the lead. 2. Linear regression of the trend of seasonal concentrations in years showed that grape was under the trend of year-round consumption, whereas apple was under the trend of season consumption. Analysis by maximum marginal likelihood analysis method for smoothing serial data showed that the yearly changes of seasonal concentrations of all the other 5 fruit species showed significantly bending trend. For example satsuma mandarin was recently under the trend of season consumption following the previous trend of year-round consumption. 3. Mean consumption time was found to exhibit a significant shift for the 3 species. In the cases of grape and satsuma mandarin, consumption time was of the trend of advance, whereas in the case of peach, consumption time was of the trend of regression. 4. Analysis of the trend of monthly relative consumption of satsuma mandarin in years showed that bending trend, from decrease to increase, of seasonal concentration of the consumption coincided with the pattern of relative consumption in December, the month during which the largest consumption was recorded. Significant advance of consumption time should be forced by the increasing trends of relative consumption in Aug. to Nov. and the decreasing trends of relative consumption in Feb. to Apr. 5. Through the determination of the main factors controlling the increase and decrease of the relative consumption in each month, the analysis of the trend of monthly relative consumption should enable to identify the key factors responsible for the change of seasonality of the consumption of each fresh fruit.
The inclusion of an ethylene absorbent in the polyethylene bag is known to be effective in extending the storage period of persimmon. The polygalacturonase (PG) activity in the persimmon fruit placed in polyethylene bags with or without abosrbent was compared during storage at room temperature (about 20°C) and 5°C. PG is considered to decrease the quality and hardness of persimmon fruit during storage by its action on the pectic substances. Therefore, the activity of PG has been used as an index of the quality and hardness of the fruit. The PG activity in the insoluble fraction of persimmon fruit was higher in the presence than in the absence of an ethylene absorbent at room temperature. In contrast, no significant differences were observed in its activity in the soluble fraction. PG activity in the soluble fraction at 5°C tended to be higher than at room temperature in the presence of an ethylene absorbent. Although ethylene absorbent prevents the decomposition of total pectin at room temperature, PG activity was hardly affected by temperature or the presence of ethylene absorbent. It may be concluded that the effect of ethylene absorbent on PG is less significant than that of invertase (10) and that PG is not closely related to the softening of the fruits.
Effects of harvesting time, storage temperature and pre-storage warming were studied in relation to the subsequent development of ‘Rind yellow spot’ of Naruto (Citrusmedioglobosa Hort. ex Tanaka), a physiological rind disorder during storage. 1. When the fruit was harvested before full color developed, no incidence of the disorder was found during storage, but when harvested after that, the disorder became increasingly severe. 2. The disorder occurred much more severely on fruit stored at 2_??_10°C than at 15 °C. The disorder developed rapidly on fruit stored at 10°C during the first half of the storage period, while at 2°C storage it increased remarkably only in the second half. 3. Warming treatment at 25°C or 35°C before cold storage reduced the incidence of the disorder. Although the effect of treatment for 6 hours was slight, a marked effect was observed with treatment for 24 hours. Electrolyte leakage from rind disks was reduced when the fruit was warmed before cold storage. 4. It is suggested that the disorder appears to be a kind of chilling injury, and that its development is closely associated with storage temperature and can be prevented by pre-storage warming treatment.