The early fruit drop of ‘Starking Delicious’, ‘Mutsu’, ‘Redgold’ etc. occurred largely in the north of Akita prefecture in 1978. We tried to clarify the effects of weather conditions on the early fruit drop by investigating the weather conditions in 1978, and analyzing statistically the relationship between those in 1979-1985 and the rate of early fruit drop. In 1978, early fruit drop occurred from the 36th day after full bloom. From the 31st day after full bloom the maximum and minimum temperatures were much higher, from the 27th day to the 38th day after full bloom the duration of sunshine was less and the precipitation was more than the mean value of the previous 10 years. The rate of early fruit drop in 1979-1985 was closely correlated with the weather conditions around the 30th day after full bloom; the multiple regression equation which expresses the rate of early fruit drop was obtained using the minimum temperature, the duration of sunshine and the precipitation from the 28th day to the 34th day after full bloom. From these results, it was shown that the early fruit drop was induced by a higher minimum temperature and less sunshine. We also investigated the effects of tree vigor and pruning on the early fruit drop. To estimate the vigor of each tree, elongation of the terminal shoot was measured regularly and the mineral constituents of leaves were analyzed. The rate of early fruit drop was increased in both vigorous and weak trees, and was closely correlated with the elongation of the terminal shoot. Similar results were observed in heavily pruned trees, that is, heavy pruning increased the elongation of the terminal shoot and early fruit drop.
Peach trees, cv. ‘Sanyo Suimitsuto’, were trained to a central leader system using two species of rootstock, Pruns tomentosa Thunb. and P. persica Batsch. Growth of shoot, root and fruit were measured 6 and 8 years after the trees had been planted, when they were considered to be adult. 1. A tree on P. tomentosa produced a higher percentage of spurs (shoots shorter than 10cm) than a tree on P. persica. Such spurs completed elongation by the middle of May and produced more leaves per unit length than longer shoots. Shoots of the tree on P. persica continued to elongate until the middle of June, and were frequently longer than 20cm. 2. Newly growing white roots of P. tomentosa rootstock increased rapidly in late April and early May. Most of the white roots then disappeared in the middle of June as a result of suberization. The start of new root growth of P. persica rootstock was slower by one month than that of P. tomentosa, and a large number of white roots of P. persica rootstock were observed until the middle of July. 3. Fruits of the tree on P. tomentosa grew actively even during the period of stone hardening. They reached full ripeness 4 or 5 days earlier and were larger than those on P. persica. In 1983, the content of soluble solids in the former was higher than that in the latter, but the relationship was reversed in 1985 because of heavy rainfall and poor sunshine during late June and early July, shortly before the harvesting of the fruits on P. tomentosa. 4. From these results, we conclude that P. tomentosa is a preferable rootstock for training peach trees to a central leader system, particularly when considering fruit growth. Trees on P. persica, however, can also be successfully trained to this system by allowing the tree to bear many fruits at a younger age and by practising proper summer pruning.
Distribution of current photosynthates was studied in hardwood cuttings of ‘Delaware’ vines which were exposed to 14CO2 at different stages of rooting to clarify the involvement of photosynthesis in rooting. The 14C activity in the ethanol soluble fraction of the new shoot, upper stem, lower stem and roots were measured 6, 24 and 72 hours after 14CO2 feeding. At the early stage of rooting, nearly all of the fixed 14C remained in the new shoots, while after root appearance the amount of 14C translocated from new shoots into roots increased with time after 14CO2 feeding. This suggests that the developing roots may become a significant sink for current photosynthates. Separation of ethanolic extracts into sugar, organic acid and amino acid fractions revealed that over 90% of the 14C in each extract was found in sugars 6 hours after 14CO2 feeding, and that the percentage of radioactivity in sugars declined with time in new shoots and roots, but changed little in the upper and lower half of stems. Organic acids in the roots showed a sharp increase in the level of 14C but there was little increase in amino acids. The increased incorporation of 14C into organic and amino acids in roots seemed to be involved in the active growth of roots. The present result that a considerable amount of current photosynthates is supplied to the developing roots confirms our previous assumption that photosynthesis in hardwood cuttings of ‘Delaware’ vines plays an important role in root development during the latter half of the propagation period.
In this experiment 15N and 13C were used as tracer elements. With an increase of flowering load, percentage fruit setting and the number of shoots of spring flush decreased. The percentage fruit setting was particularly lowered by an increase of leafless inflorescences. In trees where the ratio of leaf to flower number was less than 10, the total amount of nitrogen contained in the dropped flowers was more than 10% of the nitrogen in all the fruit harvested in autumn. The percentage fruit setting of leafy inflorescences was higher and the ovary growth during 4 to 5 days of preflowering stage was greater than that of leafless inflorescences. It was also confirmed that the nitrogen which had been applied on April 20, was absorbed and translocated to new shoots as well as to flowers at anthesis. Thus it seems that the nitrogen promoted photosynthesis and increased the fruit setting. On the other hand, nitrogen which had been applied on May 8, had almost no effect on fruit setting but contributed to the development new shoots after anthesis. Most of the nitrogen which was applied on September 1, was steadily absorbed until mid November. 15N content in the leaves remained almost constant until the following February. Throughout the period from March to May, 15N content of shoots, leaves and fibrous root decreased, while that of the new leaves and flower organs increased. 15N which was applied on April 20 as well as on September 1 was uniformly distributed to plant parts such as flower organs and new shoots. Dropped flower organs contained a considerable amount of the 15N. This shows that much of the nitrogen in the flower organs was lost through flower dropping. Although a lot of 13C-photosynthates was translocated to leafy inflorescences, the total amount of 13C in the dropped flowers was greater. Among the plant parts, 13C content was highest in the new leaves through anthesis. 13C content in the old leaves decreased rapidly while that of flower organs increased.
To understand the mechanism of action of ethylene in pistillate flower induction in cucumber plants, the effects of Ethrel, an ethylene releasing reagent, and gaseous ethylene were studied. The present investigation was aimed at clarifying the site of action of ethylene in inducing pistillate flowers and the role of leaves in expression of the effect. Localized treatment of either the 1st, 2nd or 3rd leaf, or shoot tip with Ethrel stimulated the production of pistillate flowers as much as when the whole plant or both 2nd leaf and shoot tip were treated. Better yields were obtained when the shoot tip or physiologically most active leaf were subjected to the treatment. Ethrel treatment of the shoot tip or roots was effective in inducing pistillate flowers in the presence but not the absence of mature leaves. When the expanded leaves were removed from the plant, leaving only the 2nd leaf to apply Ethrel to, the subsequent time of its removal gave an indication of the time needed for the required amount of Ethrel to be translocated to the shoot tip for the production of pistillate flowers. When the 2nd leaf was removed after 6 hours, no pistillate flowers were produced, while some flowers appeared when the leaf was removed 12 to 24 hours after the treatment. As the time of removal of the leaf was delayed, the number of pistillate flowers due to Ethrel increased, when the leaf was removed 10 days after treatment almost the same number of pistillate flowers were obtained as in non-defoliated plants. Application of ethylene gas to the shoot tip alone could induce pistillate flowers, but not when all expanded leaves were detached from the plant. Also, ethylene treatment of a mature leaf failed to induce pistillate flowers. Ethrel treatment of a single leaf stimulated abundant ethylene evolution not only from the treated region, but also from the shoot tip. When Ethrel was applied to the shoot tip, ethylene evolution from the treated region was much higher in defoliated than in nondefoliated plants. This may be due to the absence of expanded leaves which act as a sink, thus causing accumulation of Ethrel in the shoot tip. These results imply that the differentiation of pistillate flower is not only controlled by ethylene but that some factor which is produced in mature leaves and migrates into the shoot tip has to be coupled with a high level of ethylene for the formation of pistillate flowers. Furthermore, the results suggest that the site of action of ethylene is the floral bud itself in a certain developmental stage.
Seed development in selfs and interspecific crosses of Cucurbita was observed. Endosperm growth in interspecific crosses was similar to that in selfs, but embryo growth in interspecific crosses was less than that in selfs. The difference between selfs and interspecific crosses in embryo growth after normal fertilization may result from the differences in compatibility between embryo and endosperm. In the same interspecific crosses, there was a great difference in seed development according to the parental materials used. Varietal differences are important in the success of interspecific hybridization. A medium containing half strength Murashige and Skoog′s (MS) salts with the addition of MS organics and 5g/l sucrose was suitable for the germination of 5-6mm embryos from selfs. This medium is also applicable to 1-2mm embryos from interspecific crosses. The use of parental materials with different genetic background and embryo culture can be an aid for obtaining hybrids in interspecific crosses of Cucurbita.
A comparative study was made of the effect of root temperature on water and nutrient absorption in cucumber (Cucumis sativus L.) cultivars and figleaf gourd (Cucurbita ficifolia Bouchè). These plants were preincubated at root temperatures of 12, 14, 17, 20 and 30°C for 1 or 5 days, then the rate of water and nutrient absorption was determined for the following 24 hours at the each same root temperature. In cucumber cultivars, absorption of both water and nutrients was greatly inhibited at temperatures lower than 17 or 20°C, depending on nutrient elements. Absorption of nutrients was more severely inhibited than that of water, particularly when the plants were preincubated at lower temperatures for 5 days. The difference in rates between cultivars was relatively insignificant except for P absorption, which was more significantly inhibited at 12_??_17°C in a chilling sensitive summer cultivar ‘Suyo’ than in a less sensitive spring one ‘Kurume-ochiai H’. In figleaf gourd, which is more tolerant of chilling temperatures than cucumber, both water and nutrients were absorbed at similar rates at all temperatures, being irrespective of preincubation periods. P absorption was exceptionally inhibited at 12°C after 1 day preincubation, but it became unaffected after 5 days preincubation.
Effects of various cultural conditions, such as the maturing stage, harvesting season, soil and cultivar, on total sugar content, vitamin C content and β-amylase activity were investigated with the following results. 1. Radish roots at the early maturing stage showed a higher vitamin C content and β-amylase activity than those at the late maturing stage. 2. The fluctuation of total sugar content in root juice was positively correlated with the integrated solar radiation several days before harvesting in early summer, and negatively correlated with the integrated rainfall several days before harvesting in autumn. 3. Radish roots harvested during early summer were lower in total sugar content, but higher in β-amylase activity than those harvested during late autumn when compared on the basis of the same root weight. 4. Radish roots grown in alluvial soil had a slightly higher total sugar content, vitamin C content and β-amylase activity than those grown in ando soil. 5. Shade culture, mulching treatment by plastic film, and plant density showed little effect on total sugar content, vitamin C content and β-amylase activity. 6. There was a difference in β-amylase activity among the ten cultivars of the major seven genetic groups tested, but a little difference in vitamin C content and total sugar content.
The main vascular connection observed in the fruits of melon, cucumber and Luffaacutangula Roxb. were as follows; peduncle-receptacle-pericarp (exocarp-mesocarp-endocarp)-septum-fruit axis-placenta-seed (ovule). Some vascular bundles were also observed to reach the fruit axis directly from the peduncle, although they were smaller in number and diameter than those running through the receptacle. The basic number of vascular bundles in each part was 10 each in the peduncle, receptacle and exocarp, 1 per carpel in the fruit axis and 1 per ovule in the placenta. Many vascular bundles were observed in the mesocarp and endocarp, but their basic number could not be determined. The direction of vascular bundles in each part was as follows; acropetal in the peduncle, fruit axis, receptacle, exocarp and endocarp, tangential in the mesocarp, centripetal in the septum, and centrifugal in the placenta. There were usually 5 carpels in ‘Wasada-uri’ melon although the number sometimes decreased to 4 or 3 at high night temperatures. In ovaries consisting of 5 carpels, each carpet corresponded to 2 of vascular bundles of receptacles, but in ovaries consisting of 3, 4 or 6 carpels there was no such clear correspondence. In ‘Wasada-uri’ ovaries consisting of 3, 4 and 5 carpels, 4, 8 and 5 types of carpel arrangement, respectively, were observed in relation to petals and calyxes. Among these, the typical ones were III1, IV1 and IV3 and V2 and V4 (refer to Table 2-4). Assuming that the number of carpels increased from 1 to 5 in ontogenetic differentiation as leaves or floral leaves, its sequence and arrangement seemed to be I, II1, III1, IV1 and IV3, V2 and V4 (refer to Fig. 12). From these results, it was suggested that the carpels differ congenitally in time and hence in relative position in their ontogenetic development, which consequently results in differential growth of respective carpels and respective sides of ovary and fruit.
The relationship between leaf temperature before watering and the water temperature which causes leaf injury was examined by dipping the excised leaves of African violet, Saintpaulia ionantha Wendl. cv. ‘Beth Elen’ in water kept at constant temperature. 1. When the leaves kept at 30°C for 24 hr were dipped in 15°C water for 30 sec, the degree of injury of the outer leaves was greater than that of the inner leaves. 2. Leaves kept at 20°, 25° and 30°C for 24 hr were dipped in water of 5°, 10°, 15°, 20°, 25° and 30°C for 30sec. Leaf injury was caused by dipping the leaves in water kept at a 5°_??_10°C lower than the leaf temperature. Furthermore the degree of injury became severe with increasing difference between the leaf temperature and the water temperature. 3. When the leaves kept at 30°C for 24 hr were dipped in 15°C water for 1, 15, 30, 45 and 60sec, injury resulted even by dipping for 1sec, due to the rapid drop in leaf temperature. 4. Leaf temperature was decreased gradually from 30°C to 15°C in 5°C steps by dipping in water for a short time. It was found that leaf injury resulted from a dipping time of 15sec, but not of 30sec or longer.
Chilling sensitivity of eggplant fruit after harvest was examined in relation to soil moisture and fertilizer application during cultivation. Chilling sensitivity was higher in fruit grown under wet conditions throughout the period of fruit development than that under dry conditions. When soil moisture was changed from a dry to a wet condition 3 days before harvest, high chilling sensitivity was observed in the fruit after harvest. Chilling sensitivity of eggplant fruit seemed to be considerably affected by soil moisture just before harvest. Chilling sensitivity seemed to be higher in the fruit grown with insufficient nitrogen and phosphorus fertilizers than that under the conventional application. A double application of these fertilizers had little effect on the chilling sensitivity. No consistent trend of chilling sensitivity was observed in the fruit grown under different applications of potassium fertilizer.
The changes in fruit constituents and other characteristics of persimmon fruits treated with ethanol alone or ethanol plus ethylene were examined during de-astringency and ripening at various temperatures ranging from 5° to 40°C. 1. There was a rapid decrease in tannin concentration at high temperatures with a 1.9-fold decrease for each 10°C rise in temperature. 2. A gradual decrease in flesh firmness occurred during the early holding period at 15° to 40°C. At 10°C the firmness decreased slowly and at a very slow or almost undetectable rate at 5°C. Later, there was a rapid decrease in firmness, but no significant difference was found in the rate of decrease at temperatures of 5° to 25°C. At 10°C, however, this rapid decrease in firmness began earlier than at 15° to 30°C and the softening fruits appeared to become water-logged in theflesh region. 3. The decrease in peel chlorophyll concentration was rapid at 15°C and slow at both 5° and 30°C. The increase in peel carotenoid concentration was rapid as the temperature was increased from 5° to 30°C, and in this case no appreciable amount of lycopene was found in the peel. 4. The decrease in flesh firmness began earlier in ethylene-treated fruits than in untreated ones. The softening accelerated by ethylene treatment remained at a constant level during holding at any temperature thereafter. 5. The concentration of ethanol vapor within packed cartons rose quickly to a peak about 1 hour after the application of the ethanolic solution and then decreased rapidly. These changes were more apparent with higher temperatures. The penetration of applied ethanol into fruits was almost complete within less than 3 days even at a low temperature of 10°C.
The localization of lipolytic acyl hydrolase (LAH) in chloroplasts was studied and the change in LAH activity determined in relation to the advance of senescence in spinach leaves stored at 25°C. Chloroplast fractions were prepared by differential centrifugation and sucrose density gradient centrifugation. From the distribution of chlorophyll and marker enzyme activity, it was found that the LAH was contained in broken as well as intact chloroplasts, suggesting that it may be localized in the chloroplast thylakoids. The LAH activity of spinach chloroplasts increased after 3 days of storage coinciding with the beginning of leaf yellowing, then decreased with the advance of yellowing. It is inferred from these results that the chloroplast LAH together with lipoxygenase, degrades the chloroplast lipids with the fatty acid hydroperoxides formed being involved in chlorophyll degradation.
Water convolvulus (Ipomoea aquatica Forsk.) is widely distributed as leafy vegetables in South-East Asia including southern area in Japan. It shows chilling injury manifested as browning of young leaves (2-3 immature leaves located at top part of each vine) and young stems (top part of each vine) when stored at temperatures about below 9°C. In the present study, the changes of K+ leakage, free amino acid contents, phenylpropanoid contents, and some enzyme activities relating to the biosynthesis of phenylpropanoids were inveatigated with reference to the chilling injury. The materials were sealed in polyethylene bags (0.03mm thickness) and stored at 1, 6, 9, 12, 15, 20, and 30°C. A break point of Arrhenius plot for K+leakage in young and mature leaves was found between 10 and 16°C, whereas the matured leaves showed only a little chilling-sensitivity. A marked increase of the rate of K+ leakage occurred in young leaves stored at 1°C, preceding the appearance of browning. As the contents of phenylpropanoids such as t-cinnamic, p-coumaric, caffeic and chlorogenic acids were investigated, they increased before the occurrence of chilling injury and then tended to decline almost simultaneously with the development of chilling injury. They also increased at 15°C, but the rise delayed and the extent was considerably lower than that at 1°C. Among the enzymes relating to the biosynthesis of chlorogenic acid, a main substrate of browning, hydroxycinnamoyl CoA ligase (CL) activity increased in both of 1°C and 15°C storages, then the increase was faster at 1°C reaching to a peak before the occurrence of chilling injury. Hydroxycinnamoyl CoA: quinate hydroxycinnamoyl transferase (CQT) activity showed a markedly higher increase in the 1°C storage. On the results, we present a conclusion of the low temperature induced browning mechanism as follows; exposure to low temperature leads to a rise of phenolic contents through activation of the enzymes such as CL and CQT. The accumulated phenolics induce the browning after its enzymic oxidation.
A simple CA storage method using both ethylene-acetaldehyde (E•A) removing agent and seal-packaging with plastic film bags was applied to mature-green Japanese apricot (Mume)(Prunus mume Sieb. et Zucc.) and green Kabosu fruits (Citrus sphaerocarpa hort. ex Tanaka). The effects of each gas level in the sealpackaged bag (ethylene, acetaldehyde and carbon dioxide) on the keeping quality and physiological injury were examined by using the film properties as parameter. (1) Mature-green Mume could be stored at 20°C for more than 9 days by this method. (2) The physiological injury on mature-green Mume increased remarkably at a carbon dioxide level of about 20% and occured in almost all fruits at higher than 25%. Whereas in the presence of E•A removing agent, the physiological injury was suppressed remarkably and the ratio of injured fruits was 0-4% at a carbon dioxide level below 25%. (3) When green Kabosu fruits were stored at 5°C by this method, degreening and the physiological injury were not detected for more than 4 months. (4) The physiological injury on Kabosu fruits increased remarkably at an acetaldehyde concentration above 2ppm and rached 100% at 10ppm. (5) The level of carbon dioxide in seal-packaged bag had a significant influence on ethylene and acetaldehyde production, and it was determined by both the respiration of fruit and the gas permeability of film.