Journal of the Japanese Society for Horticultural Science
Online ISSN : 1880-358X
Print ISSN : 0013-7626
ISSN-L : 0013-7626
Volume 47 , Issue 4
Showing 1-15 articles out of 15 articles from the selected issue
  • Tadayuki KURAOKA, Kazuo IWASAKI, Takaaki ISHII
    1979 Volume 47 Issue 4 Pages 437-442
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    GA3 and ethephon were applied to satsuma mandarin (Citrus unshiu Marc.) fruit at a concentration of 100ppm 35 days before harvest. GA3 depressed the level of ABA in the flavedo during fruit maturation and senescence. On the contrary, ethephon raised the ABA level. Peroxidase activity in the flavedo decreased rapidly during fruit maturation and then leveled off towards senescence. This rapid decrease in enzyme activity was inhibited by GA3 application and accelerated by ethephon. Although there were 15 isozymes of peroxidase in the flavedo of immature fruit, some of the isozymes disappeared during fruit maturation and only 9 isozymes were finally found at harvest time. GA3 application decreased the reduction in number of peroxidase isozymes though it conversely increased the reduction in some isozymes. The activity of 2 isozymes was increased and other 2 isozymes disappeared by ethephon treatment. In general, very low activity and fewer isozymes of peroxidase were observed in the albedo as compared to those in the flavedo.
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  • Fusao MIZUTANI, Akira SUGIURA, Takashi TOMANA
    1979 Volume 47 Issue 4 Pages 443-447
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Root cyanogenesis of peach was caused by several respiratory inhibitors and some other chemicals. Monoiodoacetic acid and iodoacetamide were most effective. The chemicals other than respiratory inhibitors required relatively high concentrations for effective cyanogenesis. Root cyanogenesis of other Prunus species was also caused by monoiodoacetic acid. The rate of cyanogenesis much differed among the species. The rate may be related to the root prunasin content and β-glucosidase activity. The results suggest that root cyanogenesis takes place in Prunus fruit trees when the roots come in contact to respiratory inhibitors, naturally occurring allelopathic substances or agriculturally applied deleterious chemicals in orchard soils. Possible mechanism of cyanogenesis is briefly discussed.
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  • Yoshiyuki NIIMI, Hirotaka TORIKATA
    1979 Volume 47 Issue 4 Pages 448-453
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The relationship between berry growth and changes in respiratory rate and photosynthetic CO2-assimilation rate during the development of grape berries and seeds was studied in relation to their ripening.
    (1) The respiratory rate of berries in terms of dry weight basis became high at an early part of Stage I and thereafter decreased rapidly. When expressed on a single berry basis, the respiratory re ate increased rapidly during Stage I through Stage III, but there was a sudden drop at veraison.
    (2) The rate of gross-photosynthesis expressed on a dry weight basis showed its peak during the early part of Stage I and decreased rapidly thereafter. When expressed on a single berry basis, the rate of gross-photosynthesis showed two peaks, i.e., later part of Stage I and early part of Stage III.
    (3) The respiratory rate per seed showed its peak at the onset of Stage II. While, the rate of respiration on a dry weight basis was highest at Stage I and rapidly decreased thereafter.
    These results led to an assumption that the photosynthetic activity of berries may affect their development markedly at early stages of growth, and the second peak of respiration and gross-photosynthesis may play an important physiological role in controlling the onset of their ripening.
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  • Hideo IKEDA, Takaya OSAWA
    1979 Volume 47 Issue 4 Pages 454-462
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Twelve species of fruit vegetables were grown in solution culture in order to compare the growth and nitrogen assimilation between them, using NO3, NO3+NH4, NH4, NO3+NO2, and NO2 as nitrogen sources. The experiment consisted of 4 kinds of treatment conditions where 2 levels of nitrogen concn (2me/l designated as low-N and 12me/l as high-N) and 2 levels of solution pH (5 and 7) were combined. Plants were grown under different treatments for about 3 weeks.
    1. When plants were supplied with NO3, the growth of vegetables, in general, was better in high-N than in low-N regime, though kidney beans grew better in low-N than in high-N regime. In the NO3 treatment, solution pH exerted almost no effect on plant growth except for sweet corn which showed somewhat inhibited growth at pH 7.
    2. In general, fruit vegetables fertilized with NO3+NH4 grew well under any cultural conditions. Plant growth of the NO3+NH4 treatment was better than or almost equal to that of the NO3 treatment.
    3. Solution pH and nitrogen concn showed pronounced effects on growth of the plants cultured with NH4 as a nitrogen source, i.e., NH4 tended to reduce the plant growth markedly under high-N at pH 5, but not under low-N at pH 7. In comparison with NO3, the growth of kidney beans, tender soybeans, peas, tomatoes, and sweet peppers was inhibited with NH4, while the growth of sweet corn and strawberries was not. When plants were cultured with NH4, a relatively close relationship was observed between growth response and leaf NH4-N concn, i.e., the better the plant growth, the lower the NH4-N concn in leaves. In several fruit vegetables, growth responses of plants to NH4 seemed to have a relation with NH4-N/amide-N ratio or insoluble-N/total-N ratio of the leaves.
    4. In general, NH4 nutrition reduced leaf concn of K, Ca, and Mg as compared to NO3. Such reduction in concn of leaf basic elements was remarkable in sweet peppers, tomatoes, and watermelons, but only slight in sweet corn and strawberries.
    5. Growth responses of plants to NO3+NO2 and NO2 were severely affected by pH and nitrogen concn of nutrient solution, i.e., plant growth was inhibited more markedly at low pH and high N concn. However, the growth of some vegetables cultured under low-N of NO3+NO2 and under low-N of NO2 at pH 7 was comparable to that of NO3 plant. When cultured with solutions containing NO2, the growth of melones, eggplants, cucumbers, and sweet corn was relatively good, though the growth of kidney beans was markedly restricted. On the other hand, the growth of peas, tender soybeans, and tomatoes which were supplied with NO2 was good only under low-N at pH 7. Okra was the most sensitive to NO2 toxicity at pH 5, whereas at pH 7 this plant seemed to belong to a group of most NO2-tolerant vegetables. When plants were supplied with NO2, no significant interrelations were observed between growth responses and leaf concn of nitrogenous constituents and/or composition of inorganic elements in leaves.
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  • Yasutaka KANO, Tadashi ASAHIRA
    1979 Volume 47 Issue 4 Pages 463-472
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    For the purpose of precise disccusion of the role of endogenous cytokinins on the development of strawberry fruits, this research was carried out to investigate the distribution of cytokinin-like substances in strawberry fruits and the changes of the activity in fruits during fruit development in relation to achene development.
    1. Cytokinin activity was recognized in both the ethyl acetate phase and the aqueous phase which were extracted with ethyl acetate from the methanol extract of strawberry fruits. In a paper chromatography of the ammonia eluate fraction of the aqueous phase, cytokinin activity was detected at two regions, Rf 0.2-0.3 and Rf 0.6-0.8. On the other hand, in a column chromatography of the ethyl acetate fraction, the activity was recognized in one elution number (ethyl acetate 90%+methanol 10%).
    2. The majority of total activity of cytokinins in strawberry fruits was contained in achenes.
    3. Fruits grown at 20°C developed rapidly from 15 days after anthesis and matured 27 days after anthesis. Cytokinin activity in fruits was the highest 10-15 days after anthesis and decreased gradually as fruits developed. The achene of the fruits 10-15 days after anthesis was still immature as the ovule cavity was mostly occupied by the endosperm. On the other hand, the achene of the fruits 25 days after anthesis was mature as the ovule cavity was filled with the embryo.
    4. The time of maturing of fruits grown at 20°C was delayed compared to that of fruits grown at 30°C. Fifteen days after anthesis, cytokinin activity in fruits grown at 20°C was much higher than that in fruits grown at 30°C, and the achene of the fruits grown at 20°C was still immature compared to that of the fruits grown at 30°C.
    From these results, it is considered that cytokinin is actively produced in achenes when they are immature. Therefore, it is reasonable to consider that the time of maturing of fruits grown at lower temperature is suppressed because high cytokinin activity can be maintained in achenes for longer time due to their slow development.
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  • Yoshio UCHIYAMA, Keisuke YOSHIMATSU, Takuhei IGUCHI
    1979 Volume 47 Issue 4 Pages 473-478
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The present investigation is aimed at determining the effects of soil reduction and oxygen supply from leaves to the rhizome system on the browning of the lotus rhizome surface. The results obtained are summarized as follows:
    1) When liberal amount of stable manure was applied to the soil to cause the oxidation potential of rhizosphere substances to become lowered thoroughly, the formation and the adherence of dark brown materials to the rhizome surface were considerably reduced as compared to those of controls even when the rhizome of the lotus continued to grow. In addition, the darkness of both the rhizome surface and rhizosphere materials were also reduced after the growth of the rhizome had ceased.
    2) The lotus leaves of growing rhizomes supplied its rhizome system with gaseous mixtures of high oxygen concentrations from 22 to 28% in the daytime. A liberal supply of oxygen from leaves to the rhizome system through the aerenchyma seemed to cause the browning of both the rhizome surface and rhizosphere materials.
    3) The tissues of lotus rhizomes usually maintained lower oxidation potentials than rhizosphere substances during the growth of rhizomes. However, the oxidation potentials of rhizomes were shifted to a higher range than those of rhizosphere substances when the leaves were artificially removed or naturally died. The darker the color tone of the rhizome surface, the greater the potential alteration caused by defoliation.
    4) The browning of the lotus rhizome seems to depend closely on the dynamic equilibrium between oxidizing factors derived from the leaves and reducing factors derived from the rhizosphere substances.
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  • Hisami SASAKI
    1979 Volume 47 Issue 4 Pages 479-484
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    In the present investigation, which aimed at determining the effects of various growth factors on adventitious bud formation of lettuce hypocotyl segments cultured in vitro, several sequential culture media adequate to each phase of the development of cultures were examined. Culture media that were devised for the preculture of lettuce hypocotyl segments were designated as ′initial′ media while those which are adequate to the subsequent subculture were referred to as ′transfer′ media. The results obtained are summarized as follows:
    1) With resepect to the inorganic ingredients of initial media, practically no difference in effectiveness of bud formation was recognized between White′s (W-M) and Murashige-Skoog′s (M-S) basal media, though the M-S was superior to the W-M as sources of inorganic ingredients for the subsequent subculture.
    2) From the experiment with initial media including 0.2 to 1.0% of casamino acids, it was concluded that its optimum concentration for the bud formation of lettuce hypocotyl segments widely ranged from 0.2 to 0.8%. However, the optimum range of casamino acids in the transfer medium was restricted only around 0.2%. In the comparison of NH4Cl, KNO3 NH4NO3, (NH4)2SO4 and urea, NH4NO3 added at 5 to 10mM to the initial medium showed prominent inductive effects on bud formation, which seemed nearly the same as those of casamino acids. On the other hand, it was revealed that 0.1mg/l kinetin contained in the initial and transfer media could be replaced by 100mg/l adenine without adverse effects. Uracil given in place of adenine, however, failed to produce such effects.
    4) Sucrose at 2 to 6% and maltose at 2 to 4%, which were added to the initial medium, exerted some stimulative effects on bud formation, whereas fructose showed rather detrimental effects. In the subsequent subculture, however, addition of glucose at 2 to 6%, sucrose at 2 to 8%, and fructose at 2% produced a pronounced effect on the bud formation.
    5) The optimum pHs of the culture media were revealed to range between 5.5 to 6.5 in the initial medium and around 5.5 in the transfer medium.
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  • Takaya OSAWA, Hideo IKEDA
    1979 Volume 47 Issue 4 Pages 485-491
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Eight species of vegetable crops were grown in solution culture in order to investigate the effect of potassium and calcium concentration in the nutrient solution on zinc toxicities in vegetable crops. Zinc was supplied at levels of 0.05, 3, and 10ppm. At each zinc level potassium or calcium was supplied at rates of 2, 6, and 18me/l. The pH of the nutrient solution was adjusted to 5.0. Plants were grown under different treatments for about three weeks.
    1. Zinc excess induced interveinal chlorosis on upper leaves in bean, cucumber, eggplant, pepper, cabbage, and spinach. In lettuce and celery chlorosis was induced on lower leaves. Increasing the supply of potassium and calcium reduced the severity of zinc-induced chlorosis. There was not so marked difference between the beneficial effect of potassium and that of calcium.
    2. Increasing the supply of potassium and calcium was effective in alleviating the growth reduction of vegetable crops due to zinc excess. This effect was generally more marked with calcium than with potassium.
    3. With increasing zinc level in the nutrient solution the zinc concentration in leaves of vegetable crops increased. Increasing the supply of potassium and calcium suppressed excessive accumulation of zinc in leaves. The influence of calcium was generally stronger than that of potassium. In any vegetable crops, regardless of potassium and calcium treatments, zinc concentration in leaves was closely related to the growth reduction due to zinc toxicities.
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  • Mamoru KUSUMOTO
    1979 Volume 47 Issue 4 Pages 492-501
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Cattleya plantlets about 5mm in height were subcultured on the basal medium supplemented with selected combinations of growth regulators and organic nutrient sources so as to find the culture medium most effective for in vitro propagation of Cattleya plantlets. The reuslts obtained are as follows:
    1) Some synergistic effects were recognized in each of the four selected combinations of growth regulators added to the basal medium. When combined with 2, 4-D, however, the other growth factors exerted stimulative effects on the plantlet development only within a narrow range of their concentrations.
    2) The development of Cattleya, like that of Cymbidium, was divided into four stages, i.e., protocorm formation, protocorm proliferation, shoot formation, and plantlet growth. The developing Cattleya seemed to require different media compositions that were specific to each stage of plant development.
    3) The culture media most effective for plantlet growth included 0.1 to 1.0mg/l kinetin and 1.0 to 5.0mg/l NAA or 0.1 to 0.5mg/l kinetin and 0.1mg/l 2, 4-D.
    4) Shoot formation of propagules was promoted most effectively by using culture media containing 6-benzyladenine at 1.0mg/l and NAA at 0.5mg/l or kinetin at 0.1mg/l and 2, 4-D at 0.1mg/l.
    5) Protocorm proliferation was stimulated most effectively by 5.0mg/l 6-benzyladenine and 0.1mg/l NAA which were added in combination to the basal medium.
    6) The culture media, containing kinetin at 0.1 to 5.0mg/l and 2, 4-D at 0.5mg/l or 6-benzyladenine at 0.5 to 5.0mg/l and 2, 4-D at 0.5 to 1.0mg/l, formed large numbers of protocorms around the apical and axillary meristems of the shoot. Relatively high concentrations of growth regulators induced the formation of protocorms or callus-like protocorms even at the root tip and on the leaf surface.
    7) With respect to organic supplements, banana juice stimulated the growth of plantlets while raw coconut milk promoted the shoot formation and protocorm proliferation of Cattleya.
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  • Mamoru KUSUMOTO
    1979 Volume 47 Issue 4 Pages 502-510
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    In order to obtain Cattleya protocorms that are uniform in both physiological and morphological aspects, in vitro tissue culture method was employed. Shoot apexes were aseptically dissected out of the newly developed buds and subcultured on solid and in liquid media. Several combinations of growth regulators and organic nutrient sources were added to the culture media to look for the composition of medium most effective for organogenesis and proliferation of protocorms. The results obtained are shown below.
    1) Four selected combinations of growth regulators each proved effective when they were added to the basal medium at proper concentrations. If growth regulators were combined with 2, 4-D, however, effective concentration of growth factors fell within a narrow range.
    2) The composition of culture media most effective for the proliferation of protocorms was fairly different from that most suitable for shoot formation of propagules.
    3) Supplementation of BA combined with NAA was most effective for protocorm proliferation. That is, the media including BA at 5.0mg/l and NAA at 1.0mg/l caused maximum proliferation of proctocorms, though wider ranges of media concentrations were also capable of exerting stimulative effects. Besides, addition of BA alone at 0.1mg/l to the culture medium showed noticeable effects on the proliferation of protocorms.
    4) Shoot formation of propagules was most stimulated by supplementation of BA at 0.1mg/l combined with 2, 4-D at 0.1mg/l. In the combination of 6-benzyladenine with NAA, however, the culture media were effective for shoot formations within a relataively wide range of concentrations, e.g., BA at 0.1 to 1.0mg/l and NAA at 0.5 to 1.0mg/l.
    5) Supplementation of 2, 4-D alone at concentrations over 0.5mg/l killed the protocorms completely, though combination of kinetin or 6-benzyladenine with 2, 4-D seemed to alleviate the toxic effect of 2, 4-D.
    6) Organic supplements such as banana juice and raw coconut milk produced a prominent proliferation of protocorms. Effects of organic supplements on shoot formation, however, were less than those of growth regulators. Addition of yeast extract to the culture media rather inhibited the shoot formation of propagules.
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  • Akira SAKAI, Satoshi MIWA
    1979 Volume 47 Issue 4 Pages 511-516
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Frost resistance of Erica and Calluna which are native to Europe and South Africa was investigated at the Gotemba Branch of the Shizuoka Agricultural Experiment Station located in a high altitude cool region of Shizuoka Prefecture. The Erica and Calluna plants introduced from Europe were overwintering in the experimental field. The Plants of both the genera from South Africa and Europe were planted in the pots arranged in a greenhouse whose daily minimum air temperature was kept within a range from 3 to 5°C.
    Dormant twigs of those plants were collected in late January, transferred to Sapporo, Hokkaido and then precooled to harden for 15 days at temperatures from -1 to -3°C. Frost resistance of the dormant twigs was examined after they had acquired hardiness fully.
    Most Erica plants introduced from Europe survived freezing temperatures from -15 to -20°C, while Calluna from Europe survived temperatures as low as near -30°C. On the other hand, most Erica plants introduced from the south-western Cape district, South Africa, hardly survived freezing temperatures of -5 to -8°C. Erica cerinthoides which is distributed widely in South Africa showed the greatest hardiness of all the species tested. It seems practically feasible and meaningful to set up a project aiming at selecting hardier Erica plants among those collected from different localities with various climatic conditions throughout South Africa. Physiological characteristics pertaining to plant hardiness are discussed in the present paper with reference to geographical distribution of species in question.
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  • Akira ISHIDA, Masao MASUI, Akira NUKAYA, Takayasu OGURA
    1979 Volume 47 Issue 4 Pages 517-523
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Experiments were conducted to determine the effect of diluted sea water on the growth and flowering of the ‘Sunlight’ rose cultivar. One-year old ‘Sunlight’ cuttings or ‘Sunlight’ grafted onto Rosa multiflora rootstocks were planted in a wooden container (40×40×20cm) filled with sand or soil. Sea water diluted with Hoagland′s solution and also tap water was used for both sand and soil cultures. Each solution contained 0, 100, 250, 500, 1000, 2000 and 3000ppm Cl. Treatments were continued for approximately 60 days beginning April 30, 1974. Salt injury was not found at 0, 100 and 250ppm Cl. In grafted plants, injury developed in both sand and soil cultures above 500ppm Cl. On own-root plants, injury was observed above 500ppm Cl in sand culture and above 1000ppm Cl in soil culture. The degree of injury was intensified as sea water was raised from 500 or 1000 to 3000ppm Cl. Symptoms such as interveinal chlorosis, marginal and tip burns, and dieback first appeared on the lower leaves and progressed upwards. They further developed on the current shoots of severely injured plants. Generally the injury was more severe in sand than in soil cultures, and on grafted plants than on own-root plants, and highly correlated with Na and Cl in old and young leaves. The Cl and exchangeable K, Mg and Na, and EC values of the soil increased with increasing sea water concentrations.
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  • Shoichi ICHIHASHI
    1979 Volume 47 Issue 4 Pages 524-536
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Some effects of mineral components of culture medium, i.e. total ionic concentration, Cation/Anion ratio, NH+4/NO3- ratio, and minor elements, affecting the growth of Bletilla striata seedlings were investigated.
    1. Total ionic concentration of medium has markedly affected the growth of seedlings. At the level of 20meq/l, the growth of roots was more stimulated than that of shoots, and the roots produced were healthy in appearance.
    At the level of 40meq/l, both shoot and root grew well in the case where the ratio of Ca++ to K+ was held within an appropriate range.
    At the level of 60meq/l, the fresh weight of the shoot was heavier than that produced at lower ionic concentrations. However, their root growth was inferior to that achieved at lower nutrient levels and globular seedlings were observed.
    2. The requirement for cation was lower than that of anion, and the partial replacement of cation by sodium had no effects. However, that of anion by chlorine caused a decrease of growth.
    3. The ratio of NH4+ to NO3- has markedly affected the growth of seedlings, and it may be required to maintain the ratio below 1.0 for better plant growth. Irrespective of concentration of nitrate ions or total ions, the growth of root was excellent at lower levels of NH4+.
    The optimum ratio of NH4+ to NO3- increased from 40/60 to 70/60 as total ionic concentration increases. The optimum ratio for the growth of both shoot and root seems to be about 40/60 or less.
    4. The addition of minor elements to the basal medium caused inhibition of seedling growth. Inhibitory effects were caused by addition of minor elements except Fe-EDTA, though alleviated by the addition of Fe-EDTA.
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  • Naoki YAMAUCHI, Kuniyasu OGATA
    1979 Volume 47 Issue 4 Pages 537-545
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The purpose of this experiment is to elucidate the role of L-ascorbic acid (ASA) in the metabolism of phenolic substances, especially in the seed of sweet pepper fruit affected by chilling injury which sometimes takes place under 1°C storage conditions. In the previous paper, two electron transport systems involving ASA were assumed to function in the seed of sweet pepper fruit. One of them (System I) is the electron transport sequence; substrates … G-6-P, GSSG, ASA: coenzyme …NAD: enzyme … G-6-P dehydrogenase … glutathione reductase … dehydroascorbate reductase … ascorbate oxidase; and the other (System II) is the sequence; substrates … ASA, chlorogenic acid, coenzyme … NAD(P)H, enzyme … oxidized ascorbate reductase, polyphenol oxidase.
    The present paper deals mainly with the electron transport through the ASA path involved in the respiratory systems of sweet pepper seeds. In addition, time-course changes in functioning of System I and System II during the storage at 1°C was also investigated. The results obtained are summarized as follows:
    1. Glutathione reductase and dehydroascorbate reductase which both are supposed to be the components of System I were proved to function actually in the sweet pepper seed. The activity of these enzymes first decreased on the 2nd day of the storage at 1°C and subsequently increased gradually with progress of time.
    2. A rapid but consistent oxygen uptake was achieved by both System I and System II. This oxygen uptake remained linear throughout most of the course examined and was fairly inhibited by the application of diethyldithiocarbamate and thiourea. These compounds are known as inhibitors of terminal oxidase, ascorbate oxidase, and polyphenol oxidase which are components of System I and/or System II. These facts may indicate that sweet pepper seeds actually include System I and System II as the parts of their electron transport systems.
    3. Oxygen uptake by System I markedly increased after the beginning of the 1°C storage and reached its peak at the time of manifestation of chilling injury, though it gradually decreased thereafter. Oxygen uptake by System II, on the other hand, increased temporarily at the beginning of the storage at 1°C and then decreased sharply with progress of chilling injury.
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  • Toru MAOTANI, Yoshiomi HASE, Ryoji MATSUMOTO
    1979 Volume 47 Issue 4 Pages 546-552
    Published: 1979
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The purpose of this study is to elucidate the mechanism of increase in bitterness of natsudaidai (Citrus natsudaidai Hayata) fruit caused by freezing and also to devise a method of determining the naringin content as related to the organoleptic taste.
    1. Most of the naringin contained in the pulp segment was soluble in water. Only a little insoluble naringin was detected in natsudaidai fruit.
    2. The increase in bitterness of frozen pulp segments depended on (1) an increase in naringin content of the juice exuded in the juice sacs from the sac membrane that was injured by freezing and (2) the exudation of large quantities of naringin from this membrane, especially from the stalk tissue, caused by chewing.
    3. Naringin content of the pulp juice squeezed with a hand juice wringer was closely related with bitterness of the pulp.
    4. Not so strict conditions were required for the measurement of naringin content by the modified Davis method that a linear regression curve, i.e., Y=0.12+4.27 X, could be used in most naringin determinations.
    5. From the results obtained, it seems feasible to determine the bitterness of pulp segments even at the site of citrus growing areas. Sample juices squeezed with hand juice wringers may turn yellow when treated with Davis reagents, and then naringin content can be determined by spectrophotometry or with a color chart.
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