Journal of the Japanese Society for Horticultural Science
Online ISSN : 1880-358X
Print ISSN : 0013-7626
ISSN-L : 0013-7626
Volume 44 , Issue 3
Showing 1-15 articles out of 15 articles from the selected issue
  • Shuichiro MATSUI, Hirotaka TORIKATA
    1975 Volume 44 Issue 3 Pages 213-220
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    In contrast with naturally formed galls due to larvae of gall wasps, pseudogalls induced by injection of the larval extract into dormant buds of chestnut trees were observed morphologically to clarify whether or not active compounds contained in the extract were the substances which actually induce gall formation.
    Pseudogalls formed from stems and leaves of the susceptible variety showed intensive increment in number of cells and hypertrophy of cells and these kataplasmic changes resembled those occuring in natural galls at the initial stage of gall development at which gall tissues displayed normal increase and cells were lacking in cytoplasm due to hypertrophy. In mature natural galls collected in and after October, however, nuclei and nucleoli were observed to be enlarged and cytoplasm to be hyperplasmic, and thus the mature natural galls were cytomorphologically different from artificially induced pseudogalls with respect to these points.
    Though pseudogalls could be formed from stems of the resistant variety, they were smaller in size and displayed less increment in cell number than those of the susceptible variety. On the other hand, pseudogalls could not be formed on leaves of the resistant variety and vascular bundle systems around the injection parts became necrotic and deposited polyphenolic substances.
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  • Shuichiro MATSUI, Hirotaka TORIKATA
    1975 Volume 44 Issue 3 Pages 221-227
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Callus formation from stems, leaf stipules and leaf veins of gall wasp-susceptible and-resistant chestnut trees was studied to clarify the difference in gall growth induced by wasps in both varieties.
    Comparing with the susceptible variety “Çne-17”, the resistant variety “Ginyose” showed equal or greater callus formation when their tissues were cultured on media containing auxins or Cytokinin. Further, there were no differences between several susceptible and resistant varieties with regard to callus formation from young stems on the same media as above or on a medum containing the larval extract. A similar result was obtained from the growth of sub-cultured callus derived from stems of these varieties.
    In conclusion, it can be said that callus formation from young tissues of chestnut varieties in response to plant hormones has no relationship to their susceptibility or resistance to gall wasps.
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  • Kazuo IWASAKI
    1975 Volume 44 Issue 3 Pages 228-234
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    1. This experiment was conducted to examine the effects of oxygen levels of soil atmosphere on flowering, fruit set, growth and quality of Satsuma mandarin. Oxygen concentration in the soil air was maintained at five levels, i.e., 20 (air), 10, 5, 2 and 0 (nitrogen gas) per cent by mixing air with nitrogen gas.
    2. Lower levels of soil oxygen maintained around the rhizosphere from April 9, immediately after sprouting, to May, before flowering, exerted significant effects on the flowering time and blossom production. No flowers attained the full state of bloom at the 2 or 0 per cent soil oxygen levels.
    3. When the soil oxygen concentration was kept low from the fruit set to harvest time, the tree growth, fruit development, sugar content in the juice, and carotenoid content in the peel were markedly depressed, except that the acid content in the juice was increased at the harvest time. In the post-bloom treatment, however, higher sugar and carotenoid content and lower acid content were observed only at 0 per cent oxygen concentration.
    4. At the end of the experiment, N, K and Ca concentrations in the leaves of pre-bloom treatment and N, P, K and Ca of post-bloom treatment were lowered when grown under low soil oxygen supply.
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  • Yutaka MACHIDA, Itaru KOZAKI
    1975 Volume 44 Issue 3 Pages 235-240
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Fruit quality was quantitatively expressed by pressure resistance, refractometer readings, pH value of juice and weight of fruit in lieu of texture, sweetness, sourneess and fruit size, respectively. Statistical analyses were made on cultivar populations with respect to environmental variations which manifest themselves on individual fruits and trees as well as inter annual variations.
    Year to year variation was great in fruit weight and refractometer readings, and such variation was small for pressure resistance and the pH value of juice. Sampling errors estimated were extremely great for fruit weight compared with the other characteristics.
    The quality of Chojuro fruits collected from different regions indicated some variation in pressure resistance and pH value of juice.
    Comparing recent cultivars with old ones, it clarified that the results of quality improvement are more evident for fruit texture, expressed by pressure resistance, than for any other characteristics.
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  • Tetsuo SUZUKI, Shigeru OKAMOTO, Yoshiei YAMADA
    1975 Volume 44 Issue 3 Pages 241-247
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Experiments were carried out to clarify the combined effects of shading, nitrogen supply and watering on leaf color and fruit quality in relation to the changes in chlorophyll, nitrogen and water contents in the leaves of young satsuma mandarin (cv. Miyagawa-wase) trees during the summer and autumn seasons.
    1. Water content in the leaves of the wet plot was definitely higher than that of the dry plot, and it was slightly greater for the shaded trees than for the non-shaded ones. Chlorophyll content in the leaves of the shaded trees was greater than that of the non-shaded ones. It was higher for the plot where a high level of nitrogen was supplied than for that plot supplied with a low level of nitrogen, and also higher for trees grown under wet conditions than for those grown under dry conditions. Among those, the chlorophyll content of the shaded trees was distinctly high. Nitrogen content in the leaves of the non-shaded trees was markedly higher in the plot supplied with high level of nitrogen than that supplied with low level. On the contrary, in the leaves of shaded trees the difference was hardly observed. Potassium content in the leaves was slightly higher for the shaded trees.
    2. The index of leaf color was definitely higher for shaded trees than for non-shaded trees, and the leaves of shaded trees showed a dark green color. Of the non-shaded trees, the index was higher for the plot supplied with a high level of nitrogen than for the plot supplied with a low level, and also it was higher for wet soil than for dry soil. Leaf color was most affected by light intensity, followed by nitrogen supply and then by soil moisture.
    3. Growth of fruits was greater for non-shaded trees than for shaded, greater for the low level of nitrogen than for the high level, and also greater for wet soil than for dry soil. In particular shading brought about an increase in droping of young fruit and distinctly inhibited growth of the fruit. The index of fruit shape was low in the shaded trees, showing a decrease in the ratio of the transverse to longitudinal diameter, and this trend was also shown on fruits grown in the dry soil. The index of fruit color was higher for non-shaded trees than for shaded, and also higher for wet soil than for dry soil. Fruit coloring was markedly delayed for shaded trees. The proportion of rind to fruit was larger for non-shaded trees than for shaded, and also larger for the plot with the high level of nitrogen than for the one with the low level. The soluble solids content in fruit juice was higher for the non-shaded than for the shaded plot and for the plot with the high level of nitrogen than for the one with the low level. The dry soil plot displayed a little higher content than the wet soil plot. The citric acid content was higher for the shaded trees than for the non-shaded, and also for the plot with the high level of nitrogen than for the low level. Such a trend was also observed for the soil moisture variable; that is, the acid content was higher for dry soil than for wet soil.
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  • Michiro ENDO
    1975 Volume 44 Issue 3 Pages 248-259
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    This paper deals with the influence of irrigation on diurnal fluctuation of fruit diameter, size and quality of harvested fruit of the Nijusseiki pear. Moreover, the effects of bagging combined with irrigation on fruit growth behavior was studied.
    The results obtained are summarized as follows:
    1) Under dry and high temperature condition in late August, when the proper amount of water, 90l per tree, was supplied every day, the contraction of fruit diameter in the daytime was remarkably reduced, however, the daily growth and the amplitude of fluctuation in fruit size were hardly affected. Excessive irrigation (360l per tree) resulted in severe daily contraction as compared with that of non-irrigated fruits or controls, and a remarkable decrease in daily growth and reduction of the amplitude of fluctuation.
    2) Continuous measurement on daily change of fruit size after irrigation in late August revealed that the growth of fruit was advanced to large extent on the night following the irrigation. After that, however, it decreased to the same rate as that of controls, and consequently little difference in cumulative growth increment during the three days was obtained between irrigated and non-irrigated plots.
    When treated with excessive irrigation, the fruit showed no contraction but remarkable enlargement in the daytime immediately after the irrigation. After the next day, however, extreme contraction occurred, and the nocturnal enlargement amounted to only enough to recover from the daily contraction, and thus total growth was inferior to that for other treatments.
    3) In cace of suitable water supply, the size, appearance, and quality of fruit were most desirable, though fruit maturation was delayed a little. Size and appearance for non-irrigated fruit were poorer and free acid content was higher than for irrigated fruit.
    Excessively irrigated trees produced fruits of intermediate size with the lowest soluble solid content, and often displaying a disordered peel with an uneven rough. surface which is usually called “yuzuhada”.
    4) In general, daily irrigation time had little influence on diurnal fluctuation in fruit diameter. Growth rate of fruit, however, was slightly higher in the twice (morning and evening) irrigated trees, which was followed by trees with one time (evening or morning) irrigation.
    5) Harvested fruit size was largest for the twice irrigated plot and smallest for the morning irrigated one, while soluble solid content was highest in the latter and lowest in the former. Free acid content was remarkably higher for the non-irrigated plot as compared with the irrigated plots, among which little difference was displayed.
    6) As for the effect of irrigation together with fruit bagging on diurnal fluctuation of fruit diameter, from late June to early July the contraction in the daytime was considerably increased by irrigation and the fruit growth was also increased by five to six percent regardless of bagging.
    In late August, contraction became smaller with bagging, and this tendency was much more emphasized by irrigation. The bagged fruit showed small variation in the degree of diurnal fluctuation between the irrigated and non-irrigated plots. On the other hand, the daily growth of unbagged fruit was greatly accelerated by irrigation, and consequently their cumulative increment in three days was threefold as great as that for non-irrigated ones.
    Fruit temperature rose excessively in the non-irrigated and non-bagged plot in the daytime of this hot season, especially for the fruits exposed to sunlight.
    7) Observing the pattern of diurnal fluctuation in fruit diameter at the middle of September, the fruit developing stage was set back by irrigation. Thus, as the result, the maturation of non-bagged fruit was earliest for the non-irrigated plot.
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  • Kazuomi KADOYA, Katsuya KAMEDA, Sojiro CHIKAIZUMI, Kazuo MATSUMOTO
    1975 Volume 44 Issue 3 Pages 260-264
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Cyclic fluctuations in leaf thickness and stem diameter were examined with a differential transformer.
    Variations of leaf temperature followed the cyclings. Thus it was postulated that transpiration as well as stomatal aperture might change periodically.
    When the water condition was disturbed, cyclic oscillations of both leaf thickness and stem diameter were weakened or disappeared. The Natsudaidai seedlings in a condition of water stress responded quickly to rewatering and consequently the cyclic oscillations recovered.
    Above 70 per cent relative humidity, the cyclings were not observed but below 65 per cent they reappeared.
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  • Akira SUGIURA, Hisashi HARADA, Takashi TOMANA
    1975 Volume 44 Issue 3 Pages 265-272
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Experiments were carried out using a method of applying ethanol to remove astringency from the fruits of Japanese persimmon while still on the tree. The effects of treatments on other characteristics of these fruits were also observed.
    1. Astringent fruits were enclosed in polyethylene bags containing small amount (usually 2-5mls) of 5% to 20% ethanol, and kept on the tree. The ethanol vapors penetrated the flesh of the fruits, primarily through the skin, and successfully removed the astringency. The time required for complete loss of astringency varied with time of treatment, fruit size, concentration and amount of ethanol employed, and cultivar. For example, in the case of Hiratanenashi cultivar, only two days were required when the fruits were treated at the end of July with 5mls of 20% ethanol, whereas more than a week were required when they were treated in September with 4mls of 10% ethanol. The average time required was usually within five days. No substantial drop of fruits resulted from the treatment.
    2. The ease of astringency removal by this method was compared among 10 cultivars. Hiratanenashi and Sakushu-Mishirazu were the easiest, followed by Seishu-Mukaku, Atago, Shimpei, Saijo, Shakoku, Gionbo, Hagakushi and Yokono in that order; the astringency being very difficult to remove in the latter four.
    3. Hiratanenashi fruits were thus treated at half-monthly intervals from the middle of July to the end of September. After the loss of astringency was complete, the bags were removed and the fruit were allowed to remain on the tree until harvest time. Astringency, once removed, did not reappear. The treatment had no effect on fruit size except for July treated fruit, in which it was slightly depressed.
    The non-astringent fruits showed earlier coloration and had higher contents of reducing sugars (glucose and fructose) and malic acid, compared with the astingent ones.
    There was no difference in flesh firmness at harvest between astringent and non-astringent fruits.
    The most characteristic phenomenon associated with the loss of astringency was the browning reaction of the flesh tissue. In treated fruits, brown flecks appeared in two weeks, increasing gradually until the entire flesh became brown. However, fruit with slight astringency remaining did not develop brown coloring of the flesh. The degree of flesh browning was greater at earlier times of treatments and at higher concentrations employed.
    The browning phenomenon was observed in fruits only when they remained on the tree; it was not observed in fruits detached and stored for one month.
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  • Takaya OSAWA, Hideo IKEDA
    1975 Volume 44 Issue 3 Pages 273-280
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Cucumber, pepper, celery, and lettuce were grown in solution culture in order to investigate nitrite toxicities in comparison with ammonium toxicities. Nitrite or ammonium was supplied in combination with nitrate in various proportions, with the total nitrogen concentration being held constant at 12me/l. The pH of the solution was adjusted to two levels, 7.5 or 5.0. Plants were grown under different treatments for three to four weeks.
    1. Nitrite toxicity symptoms, such as leaf wilting and root browning, occurred much more severely at pH 5.0 than at pH 7.5. On the other hand, ammonium was. less injurious than nitrite, but induced slight root browning in some species at pH 7.5.
    2. At pH 7.5 the relative tolerance of vegetable crops to nitrite evaluated on the basis of growth response was in the following order: cucumber>celery>pepper> lettuce. At pH 7.5 each vegetable crop showed better growth with ammonium than with nitrite, and the growth of lettuce was stimulated by ammonium treatments. The order of relative preference or tolerance of vegetable crops to ammonium at pH. 7.5 was as follows: lettuce>cucumber>celery>pepper. At pH 5.0 nitrite inhibited the plant growth much more markedly than at pH 7.5 and caused the death of plants in nitrite sensitive species. Ammonium treatments at pH 5.0, however, did not affect the plant growth so markedly.
    3. At pH 7.5 the concentration of ammonium nitrogen and amide nitrogen in. plants generally increased with the increasing proportion of nitrite or ammonium in the solution. In nitrite treatments, nitrite sensitive species tended to accumulate more ammonium nitrogen and amide nitrogen in both leaves and roots. On the other hand, the more the species was sensitive to ammonium, the more the accumulation of these constituents in roots increased in ammonium treatments. However, the difference of growth response of a crop to nitrite and ammonium treatments could not be explained solely on the basis of accumulation of these constituents in plants.
    4. As to inorganic constituents in leaves of plants grown at pH 7.5, ammoniumm treatments decreased the concentration of cation elements such as K, Ca, and Mg, while nitrite treatments decreased that of various elements, P, K, Ca, Mg, and Fe.
    5. In another solution culture experiment, the increasing concentration of nitrate in the solution at a given pH level did not alleviate the growth inhibition of vegetable crops caused by nitrite, and the absolute concentration of nitrite appeared to be the dominant factor in the growth inhibition.
    6. From these results, it seems that at a relatively high pH level there is a similarity between nitrite and ammonium toxicities with respect to the accumulation of ammonium nitrogen and amide nitrogen in plants. Compared with ammonium, however, nitrite induces serious injury to roots, which may be the main cause of nitrite toxicities especially at low pH.
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  • Eisuke MATSUO
    1975 Volume 44 Issue 3 Pages 281-285
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The experiment was carried out to clarify the effect of temperature and light treatments on the type of leaves developing from scale bulblets. The Easter Lily cultivar “Hinomoto” was scaled at 25 or 15°C in darkness for 5 months prior to a growth production phase. On 1/15/74 the newly developed bulblets (scale bulblets) were planted in peatmoss and then grown for 75 days at constant temperatures of 25, 20, 15 or 10°C in darkness or in continuous illumination by fluorescent tubes (NEC, FL-20-BR).
    The development of foliage scales on the scale bulblets was greater in light than in darkness and was independent of the previous scaling or subsequent growing temperature treatments. In light, when the lily was scaled at 15°C, foliage scales developed almost equally regardless of the subsequent growing temperature treatment. When scaled at 25°C, however, the lower the growing temperature was, the greater the development of foliage scales was. Independent of growing temperatures, new bulblets with foliage scales were more numerous when scaled at 15°C than at 25°C.
    In darkness, bulblets formed foliage scales to a greater degree at 10°C than at any other growing temperature. These foliage scales developed particularly at the end of the experiment. At 25°C (growing temperature), scale bulblets in darkness bolted or developed stems with foliage leaves to the same degree as in light and were independent of the original scaling temperatures. At the growing temperatures of 20, 15 or 10°C, more bolted bulblets were observed when originally scaled at 25°C than at 15°C. At the growing temperatures of 20 or 15°C, bolting occurred to a greater degree in light than in darkness.
    These results indicate the following: 1) When new bulblets are devoloped at a higher temperature, they bolt more easily than when developed at a lower temperature and the coolly formed bulblets tend to develop foliage scales. 2) Light during bulblet growth induces the bulblet to form foliage scales and this light response is promoted by low temperature. 3) In darkness, a growing temperature of 10°C induces foliage scale development.
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  • Kuniyoshi KONISHI
    1975 Volume 44 Issue 3 Pages 286-293
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The effects of the cold storage of rooted cuttings which had not yet assumed the rosette form, and the effects of growth temperature on stem elongation and flowering in chrysanthemum were studied.
    In Experiment 1 the rooted cuttings of cv. ‘Okayamaheiwa’ which had been stored at 1-3°C for 0, 10, 20, and 40 days were planted in a heated greenhouse on Nov. 30, and were grown under long-day conditions. After 10 days they were pinched and transferred to short-day conditions. On the same day night temperature treatments of 5, 10, 15, and 20°C were initiated.
    Under low night temperature conditions, plants unchilled or chilled for shorter periods assumed the rosette form, while those chilled for longer periods elongated and flowered well. Under high temperature conditions, however, the unchilled plants elongated and flowered as well as those chilled for longer periods.
    In Experiment 2, the pinched rooted cuttings of cvs. ‘Uchusen’ and ‘Tamaorihime’ were stored at 1-3°C for 40 days, and planted with the unchilled cuttings in the heated greenhouse under long-day conditionson, on Nov. 16. After 20 days they were transferred to short-day conditions and night temperature treatments of 5, 10, 15, and 20°C were initiated. The results obtained were essentially the same asin Experiment 1.
    These results show that the growth activity of the chrysanthemum plant becomes lower during the winter season, and the temperature range within which the plant can elongate is narrow. A plant in this state can elongate and flower nly at higher temperatures. When the plant is exposed to low temperatures, its growth activity is increased. Thus the plants exposed to low temperatures elongate and flower at lower temperatures as well as at higher ones.
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  • Yutaka MORI, Atsushi HASEGAWA, Kunio KANO
    1975 Volume 44 Issue 3 Pages 294-302
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The present studies were carried out in order to develop techniques for clonal propagati on of freesia by meristem culture. Cultivar “Rijnveld′s Golden Yellow” was used.
    The following results were obtained;
    1. Only the axillary buds of corm formed good callus and other tissues such as cortex, cortex and central cylinder, or the base of new stem failed to form callus. The culture medium favourable for callus formati on was constituted as follows: Hyponex (7-6-19) 2g, bacto-peptore 2g, bacto-tryptone 2g, myo-inositol 100mg, thiamin-HCl 0.4mg, NAA 2mg, sucrose 30g, agar 10g, water 1000ml.
    2. Multiplication of callus was possible via the above-mentioned medium for which Sucrose was revised from 30g to 10-20g and NAA revised from 2mg to 0-2mg, the medium being supplemented with Kinetin 2-20mg.
    3. Differentiation of shoot and root from callus occurred after spherical shoot primordia were formed. The formation of shoot primordia was promoted by supplementing the medium with Sucrose 20g, NAA 0-2mg and Kinetin 20mg. The number of shoot primordia increased remarkably through subculture. The shoot primordium morphologically resembled the early stages of corm originating from seed.
    4. Shoot growth from the shoot primordium occurred for a medium containing IAA 0.2-1mg and Kinetin 2mg. After shoot growth, roots were formed easily at the base of a shoot by placing it in a medium containing NAA 2-10mg.
    5. The plantlets obtained were planted in the 15cm clay pots, and after six months, new corms were produced. Then these corms were planted in the fall, and they flowered normally in the following spring.
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  • Naoki YAMAUCHI, Takahisa MINAMIDE, Kuniyasu OGATA
    1975 Volume 44 Issue 3 Pages 303-307
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The object of this experiment is to determine the changes of ascorbic acid and its decomposed products in several fruits and vegetables during storage at 1°C and to reveal the relation between the occurrence of chilling injury and the decrease of ascorbic acid.
    1) Excluding sweet pepper which shows only pitting injury on the surface of peel, the decrease of L-ascorbic acid (ASA) content and the increase of 2.3-diketo-L-gulonic acid (DKG) content were observed with the advance of browning in okura, sweet potato, egg plant and banana fruits.
    2) ASA content decreased and DKG content, on the other hand, rapidly increased during the storage at 1°C in okuras. Phenolic compounds, to form brown pigments, decreased at the fourth day when the symptom of chilling injury were observed in fruits during the storage at 1°C.
    3) When shikimic acid, chlorogenic acid and dopa as browning substrates were added to okura peel tissues at 1°C, the browning in tissues advanced, but DKG content was rather decrease. On the other hand, the addition of oxalic acid that is a final product in ascorbic acid oxidation effectively caused the accumulation of L-dehydro-ascorbic acid (DHA) and DKG content.
    It is possible to conclude from the result above that increasing of DKG content with the advance of chilling injury in okuras was due to direct or indirect effect of oxalic acid.
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  • Masanori MIYAZAKI, Shinzo KUNISATO
    1975 Volume 44 Issue 3 Pages 308-312
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    The present study was carried out with sand culture to investigate the influence of nitrogen, phosphorus, potassium, calcium and magnesium levels in culture solution on the nitrate-nitrogen content in tomato fruits, by using Fireball variety.
    When tomato plant was grown on culture solution containing either low levels of NO3-N or potassium or high level of calcium, NO3-N content in the fruit was markedly low as compared to the control. In cases of the former two, NO3-N content was always low during the immature through full-ripe stages. On the other hand, the content in the fruit grown on a high level of calcium was as high as that of the control at the immature stage, but decreased during the ripening period. The content of NO3-N in the leaf was also reduced by these conditions.
    When tomato plant was grown on either low levels of NO3-N or potassium, or high level of calcium, it was found that the amount of NO3-N absorbed by a plant was low. The contents of total-nitrogen, potassium and organic acids were low and the contents of calcium and reducing sugar were high in the ripe fruit.
    When the tomato plant free from NO3-N was supplied with potassium or calcium nitrates as nitrogen sources in culture solution, NO3-N content in the fruit supplied with the potassium salt became much higher after 1 and 5 days of supply than in the fruit supplied with the calcium salt. NO3-N contents in the leaf and calyx supplied with potassium nitrate were also higher than with calcium nitrate, but the differences of indexes of the contents in these between potassium and calcium nitrates were not too remarkable as in the fruit between potassium and calcium nitrates.
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  • Masanori MIYAZAKI, Shinzo KUNISATO
    1975 Volume 44 Issue 3 Pages 313-320
    Published: 1975
    Released: July 05, 2007
    JOURNALS FREE ACCESS
    Chico, one of the low nitrate accumulating varieties, was grown in the field and the effects of fertilizing and managing practices were studied on NO3-N content in tomato fruit.
    As to the effect of fertilizing, it became obvious that NO3-N content in ripe fruits tended to decrease by decreasing the amount of applied nitrogen and potash, and considerable decrease of NO3-N content was observed by increasing the amount of applied lime. Tomato fruit grown with the split application of slow-acting nitrogen fertilizer and nitrogen fertilizer containing nitrification inhibitor contained low level of NO3-N.
    For the purpose of reduing NO3-N level in the soil by soil disinfection, one of the test fields was flooded during the previous winter season and drained in the early spring, and another one of the fields was sterilized with chloropicrin. As a result, NO3-N contents in the soils and those in the fruits grown in the treated fields were actually lower. It was also confirmed that the flooding practice accelerated leaching of NO3-N in the soil, and chloropicrin treatment greatly inhibited the nitrification.
    Based on the above knowledge, Chico was tested as to the practical ways for reducing NO3-N content in the fruits. Chico was grown in the field which had been flooded during the previous winter season or had been previously sterilized with chrolopicrin, by fertilizing high level of lime and split application of crotonyliden diurea or ammonium sulfate with thiourea. The result obtained was satisfactory, i.e., NO3-N content in the fruit was always below 3ppm throughout the harvest season, and the fruit yield did not decrease.
    The conditions of the modified cultivation to lower NO3-N content in tomato fruit described in the previous paper, i.e., “lowering NO3-N level in the fruit at the breaker stage”, and “lowering the level during the subsequent ripening process” were realized by management practice mentioned in this paper and the introduction of the low nitrate accumulating varieties.
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