The aim of this study is to clarify the roles of NAD⁺-dependent sorbitol dehydrogenase (NAD-SDH) and NADP⁺-dependent sorbitol-6-phosphate dehydrogenase (S6PDH) in fruit development, and the regulatory mechanism (s) underlying their expression during development using loquat as the study material. The cDNA of NAD-SDH, cloned from loquat fruit, consisted of 1, 572 bp and contained an open reading frame of 1, 023 bp capable of encoding a protein of 371 amino acids. The deduced amino acid sequence has 97.8% identity to that of an apple fruit. The activity of NAD-SDH is a function of fruit development, i.e. the increase in protein of this enzyme synchronized consistently with that of activity showing no posttranslational modification throughout the developmental stages. Furthermore, NAD-SDH activity correlated with the mRNA levels, indicating that the key regulatory step of the activity is at the transcriptional level. The increase in NAD-SDH with fruit development plays a dominantly important role during fruit maturation and sugar accumulation. The trend of S6PDH activity during fruit development paralleled that of NAD-SDH activity. It correlated with protein and mRNA levels revealing that the regulation of the activity is mainly at the transcriptional level like NAD-SDH. However, the role of S6PDH in fruit is not yet clear.

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An experiment was conducted under green house conditions to observe the distribution of vesicular-arbuscular mycorrhizal (VAM) hyphae between plants. Special acrylic root boxes with three compartments were constructed. The two outer compartments, into which the trifoliate orange (Poncirus trifoliata Raf.) seedlings and Bahia grass (Paspalum notatum Flugge.) were transplanted, were separated from the center compartment by a barrier made of a nylon screen of 37μm mesh. The inoculation with a VAM fungus, Gigaspora margarita Becker and Hall, was done in the center compartment. The density of hyphae, percentage of infection, and the number of spores were higher in the Bahia grass compartment than those in the compartment with trifoliate orange. A petri dish experiment showed that although the Bahia grass and trifoliate orange root exudates stimulated the hyphal growth of G. margarita, the length of hyphae in the Bahia grass treatment was longer than that of the trifoliate orange. In this experiment it was possible to observe in detail the distribution of hyphae in the rhizosphere of two plants under intercropping system conditions. These hyphae would be related to the interconnection between plants to promote a network system ; the formation and development of this network system is influenced by some root exudates.

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Transgenic potato microtubers were created in which the expression of sucrose synthase (Susy) was altered by introducing a chimeric gene containing the coding region of Susy that is linked to the patatin promoter in sense (S) or antisense (AS) orientation. The analysis of transgenic microtubers showed that Susy activity and starch content increased in S plants 8, 22, and 30 transformed with the chimeric sense gene ; they decreased in AS plants 3 and 10 transformed with the antisense gene. RT-PCR analysis revealed that the level of mRNA for Susy increased in S plants, and decreased in AS plants. There was a little change in the expression of genes for ADP-glucose pyrophosphorylase (AGPase), one of key enzymes in starch biosynthesis. The level of mRNA for AGPase and the activity of the enzyme increased in S 8 plant, but decreased in AS 3 plant.

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Effects of covering with film which has a low transmittance in the far-red (FR) region on bulb development of Allium wakegi Araki during summer were investigated. After planting the bulbs on July 6 and 28, the plants were grown under tunnels covered with FR-intercepting film, clear film combined with a layer of white cheesecloth, or without film. Fresh weight of basal leaf sheath and the bulbing ratio (maximum diameter of the basal leaf sheath/minimum neck diameter) under the clear film and without film increased with time after planting, but these increases were suppressed under the FR-intercepting film. Formation of bulb scales, swollen bladeless leaves, was also suppressed under the FR-intercepting film. When bulbs were planted on July 28, all plants grown under the clear film and without film formed bulb scales, whereas no plants grown under the FR-intercepting film formed them. Plants grown under the FR-intercepting film had the highest leaf chlorophyll content of those under the three treatments. The interception of FR light did not reduce leaf length or shoot fresh weight. These results indicate that the covering with the FR-intercepting film is useful for summer cultivation of A. wakegi because it inhibits bulb development without impairing other characteristics, such as leaf color, leaf length, and shoot fresh weight.

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Characteristics of mineral uptake in spray chrysanthemums grown under a hydroponic system were investigated in relation to growing seasons and developmental stages. The amounts of N, P, K, Ca, and Mg, taken up per plant, differed markedly over the growing seasons and between 'Sei Aloha' and 'Talk'. However, the ratios of P, K, Ca, and Mg to N uptake were similar over both the growing seasons and cultivars. The ratios obtained from the nutrient solution analyses were P/N 13.3±0.4%, K/N 102.6±3.4%, Ca/N 29.6±0.7% and Mg/N 10.0±0.4%. The ratios corresponded to those estimated via plant tissue analyses. Uptake of 4.3-5.2mg N fertilizer led to an increase of 1g in fresh weight. The rate of N uptake steadily rose after planting until flower buds became visible. The upward trend continued during bud development but decreased rapidly towards harvest. The ratios of P/N and K/N decreased from 16.2% and 134.2% to 8.4% and 69.5%, respectively, from the vegetative growth to the flowering stages. The ratios of Ca/N and Mg/N varied slightly.

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The mechanism of unilateral cross incompatibility in the reciprocal crossings between several evergreen azalea species and R. japonicum f. flavum behavior of pollen tube growth in the styles was studied. In crossings using evergreen azalea as seed parents, straight, thin pollen tubes elongated into the lower portion of style within 96 hr after pollination, but in those using R. japonicum f. flavum as seed parents, the pollen tube with abnormal morphology were arrested in the upper portion of the styles. These results indicate that the cross incompatibility of R. japonicum f. flavum×evergreen azaleas is accompanied by abnormal pollen tubes and a restriction of their growth in the upper portion of the style.

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The concentrations of ethanol and acetaldehyde in bell pepper fruit were very low during storage at 1%, 3%, 5%, and 10% O₂, and air at 20°C. At 0% O₂, ethanol and acetaldehyde to a lesser extent, rapidly accumulated in its tissue. The activity of alcohol dehydrogenase (ADH) was about 10 times that of pyruvate decarboxylase (PDC) during storage. The ADH activity greatly increased in the fruit exposed to 1% and 3% O₂, but in those exposed to 0%, 5%, and 10% O₂ it was slightly higher than that of the control. The PDC activity greatly increased in the fruit exposed to 1%, 3%, and 5% O₂, while those of fruits exposed to 0% and 10% O₂ were slightly higher than that of the control. ADH transcripts in the fruit exposed to 5% and 10% O₂ or air were not detectable, whereas those in the fruit exposed to 1% O₂ were significantly higher than those in 0% and 3% O₂ on day 1 at 20°C. The discrepancy of the enzyme activities and their product levels are discussed.

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We investigated the molecular response of harvested cucumber (Cucumis sativus L.) fruit to postharvest water stress. Using RT-PCR, we isolated CUPG1 cDNA, a cDNA clone encoding polygalacturonase (PG) that is inducible by water stress in cucumber fruit and characterized the expression of the gene with respect to hormonal control. The full length sequence determined by RACE-PCR, encoded a deduced protein of 435 amino acids that contained several common conserved domains as reported for PGs. The CUPG1 gene expression was also induced by exogenous ethylene but not by the application of abscisic acid (ABA). The level of CUPG1 mRNA induced by water stress, was reduced by 50% in fruits pre-treated with 1-methyl-cyclopropene (MCP), a strong inhibitor of ethylene action, which suggests that the expression of CUPG1 gene could be induced by a direct mechanism through water stress and an indirect mechanism mediated through ethylene produced in response to water stress. We conclude that water loss in harvested cucumber fruit results not only in physical changes but also leads to molecular responses, including PG gene expression.

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Flower color and floral pigments were evaluated on an intersubgeneric hybrid (9027-2), obtained by crossing R. kiusianum Makino cv. Shirobana-miyamakirishima×R. indicum (L.) Sweet cv. Hakata-jiro, and R. japonicum f. flavum. The flowers of the 9027-2 were pale yellow at full bloom. The absorption peaks detected in the extracts from the petals of R. japonicum f. flavum and 9027-2 are considered to be β-carotene and that this pigment was inherited by 9027-2 from R. japonicum f. flavum. The 9027-2 was confirmed as the hybrid between (R. kiusianum cv. Shirobana-miyamakirishima×R. indicum cv. Hakata-jiro) hybrid No.1 and R. japonicum f. flavum No.1 by isozyme analysis.

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Effects of high temperature and/or controlled transpiration by polyvinyl chloride bagging and/or by spraying with 10% wax, an anti-transpirant, or 500ppm abscisic acid on the occurrence of watercore fruit in Japanese pear 'Hosui' (Pyrus pyrifolia Nakai) were examined. The most severe case of watercore occurred on fruits which were covered with polyvinyl chloride bag from 90 days after full bloom to harvest. Fruits covered with polyvinyl chloride bags containing water from 30 days after full bloom to harvest also succumbed to severe watercore, whereas those sprayed with 10% wax, a transpiration inhibitor, became pithy, had a low specific gravity, and exhibited more watercore than those of the control. Abscisic acid at 500ppm had no significant effect on watercore. Thus, we conclude that the occurrence of watercore correlated closely with high temperature and/or the high rates of transpiration by the fruit.

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Four seedless 'Pione' grapevines, treated with gibberellic acid, which bore well-[vine A and B, superior berry coloration (SBC)] and poorly-[vine C and D, inferior berry coloration (IBC)] colored berries annually were studied. Berry development, root growth and activity, and diffusive resistance and photosynthetic rates of leaves on each vine were recorded. Although leaf area per shoot, yield and cluster weight differed, the differences between the SBC and IBC vines were not significant. The index of skin coloration, based on a color chart was significantly lower on IBC vines than that on SBC vines three weeks after veraison and during the ripening stage. At harvest, anthocyanin content of berry skins in IBC vines was less than 50% of the SBC vines. Changes in color and/or anthocyanin level of the skins closely correlated to changes in total soluble solids contents of berries. In IBC leaves, the water saturation deficit remained low in spite of the low water content after veraison, whereas the diffusive resistance tended to increase. At veraison, leaves at the 2nd and 7th nodes above a cluster borne on vine A exhibited a relatively high photosynthetic rate, whereas leaves at comparable position on vine B, it was slightly slower. On vine C, a high photosynthetic rate was observed in the leaf only at the 7th node. One month after veraison, leaves on only vine A maintained its high photosynthetic rate, irrespective of leaf position. Although they had a similar canopy area, the dry weight of IBC roots was lighter than that of SBC roots. White roots of SBC grew vigorously before veraison, whereas those of IBC began to grow three weeks after veraison. The total length of white and suberized roots was shorter in IBC vines than in SBC vines. Three weeks after veraison, the activity of white root estimated from triphenyltetrazolium chloride (TTC) reduction was significantly lower in vines of IBC than in that of SBC.

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The effect of planting density on the flower bud formation on 'Starking Delicious' apple trees (Malus domestica Borkh.) grafted on dwarfing M.9 and M.26 and semidwarfing M.7 and MM.106 rootstocks and trained to a central leader was studied. 1. As planting density increased, the number of flower buds per tree and the percent of flower bud formation decreased, but the number of flower buds per hectare tended to increase. 2. The relationship between the number of flower buds per tree (Z) and the planting density (ρ) could be represented by the following reciprocal equation. 1/Z=(1.46ρ+82.7)10^-6 (1) Also, the relationship between the number of flower buds per hectare (δ) and the planting density (ρ) could be represented by the following reciprocal equation. 1/δ=1.46·10^-6+82.7·10^-6/ρ (3) 3. The number of flower buds per tree and the percent of flower buds formed were negatively correlated to the tree height/spread ratio, indicating that the decrease of flower bud formation with an increased planting density was closely related to the upright form of the trees. 4. The vertical distribution of flower buds was closely related to the attenuation pattern of relative solar radiation along the canopy profile, indicating that the decrease of flower bud formation with an increased planting density was caused by decreasing of relative solar radiation. 5. In the 5th leaf of trees on M.9, an inhibition of 5% and more in flower buds formation occurred at higher density. As the trees aged, the inhibition shifted to the lower density plot. This shifting rate was accelerated in trees on M.26, M.7, and MM.106, compared with trees on M.9. The relationship between the percent of flower buds formed (φ) and the planting density (ρ) could be represented by the following reciprocal equation from the age of 6 years for trees/M.9 and 5 years for trees on other rootstocks, 1/φ=A_φρ+B_φ (4) where φ is 0≤φ≤100, and A_φ and B_φ depend on the tree age and rootstocks. 6. The φ remains constant at a lower LAI (F), whereas it decreased abruptly at a certain LAI. The relationship between the F and the φ could be approximated with the following two equations, In case of 0<F≤-b/2a, φ=-(b²/4a)+c (5) In case of F≥-b/2a, φ=aF²+bF+c (6) where a, b and c depend on the tree age and rootstocks. 7. LAI at which φ begins to decrease is defined as the critical LAI (Fφ_cri); Fφ_cri is expressed by the following equation. Fφ_cri=-b/2a (7) The Fφ_cri estimated by Eq. (7) had values of 1.9&acd;2.1, regardless of tree age and rootstocks. 8. The relationship between the planting density (ρ_cri) and the number of flower buds per tree (u_cri) at Fφ_cri, regardless of tree age and rootstocks, could be expressed as follows : ρ_cri=1.5×10⁴·u_cri^-0.92 (10)

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To breed pummelo (Citrus grandis [L.] Osb.) varieies with a few seeds, a female parent 'Tosa-Buntan' and a male parent 'Suisho-Buntan' were crossed ; the seed weight and the chromosome number of the progenies were determined from 1996 to 1998 inclusive. The weight of full developed seeds peaked between 301mg to 330mg. Those which weighed less than 30mg were considered to be unfertilized ovules. About 20% of partially developed seeds weighed between 31 to 180mg. Embryos rescued from seeds, weighing between 61 and 180mg, germinated better under embryo culture than when sown in plug trays. Hence, embryo culture is an effective means of obtaining seedlings from these poorly developed seeds. Furthermore, about 15% of them were not diploid. Chromosome counts of 128 embryo cultured seedlings derived from seeds weighing between 61 and 180mg revealed that there were 109 diploids, eight triploids, three tetraploid, and eight aneuploids. The aneuploids had chromosome numbers of 2n=17, 19, and 28.

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The effects of planting densities of cabbage plug transplants in the field on the uniformity of their initial growth and head size at harvest were investigated. The following results were obtained : 1. Head size uniformity decreased with small within-row spacing (WRS) from the beginning of head formation. 2. Unevenness of initial-growth of high-density transplants resulted in a decrease of uniform head size at harvest. This lack of uniformity is attributed to the initial differences in growth which increased with time. 3. Retarding harvest time did not improve growth uniformity. 4. Gaps within the row and the slow growth of some plants promoted the growth of adjacent plants. This tendency was strong under high densities. Hence, growth uniformity was decreased with time. Head size uniformity at harvest decreased when WRS was small. The degree of the decrease was controlled by the initial-growth uniformity of transplants. Thus, we conclude that avoiding the creation both of gaps and of underdeveloped stock in the field is indispensable to maintain head uniformity under dense planting conditions of about 30-cm WRS. Producing uniform transplants and promoting the establishment of transplants are important to obtain uniform cabbage head size at harvest.

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The applicability of slow sand filtration as a disinfection system for the recirculating nutrient solution in a Nutrient Film Technique (NFT) growing tomato was evaluated. The recirculating nutrient solution was filtered through a slow sand filter installed between the nutrient solution tank and the culture bed ; the filtrate was supplied to the hydroponic system. The pH of the filtrate was maintained at around 7 by the buffer action of the filter sand. The dissolved oxygen concentration in the nutrient solution decreased by 10&acd;30% through filtration ; but the tomato plants did not show any O₂ deficiency symptoms. The influence of sand filtration on electrical conductivity (EC) value was small. Nitrate-N and Mg concentrations in the nutrient solution declined slightly by filtration ; part of K in the solution was seemingly exchanged by Ca, previously held by the sand. NH₄-N, P, Fe and Mn concentrations in the filtrate did not change quickly after their addition to the water layer. Mn in the filtrate was undetected. Young leaves of tomato plants grown in NFT with this slow sand filtration system became yellow, indicating that some micronutrient, probably Mn, was deficient. The slow sand filtration system removed most fungi and bacteria added to the NFT tank. The maximum concentration of Fusarium oxysporum detected in the filtrate was about 0.1% of that in the tank ; 0.6% for Pseudomonas solanacearum. Escherichia coli was not detected in spite of the initial concentration of 2.0×10⁶ cfu·ml^-1 in the tank. The top layer of about 1cm thick from the sand layer was scraped bimonthly to re-establish the original filtration rate.

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To establish a practical method to evaluate the freezing tolerance of leafy vegetables, the relationship between freezing tolerance of intact komatsuna and spinach plants, cold-acclimated at different temperatures and electrolyte leakage from leaf tissues was determined. In both komatsuna and spinach, the freezing tolerance correlated well with electrolyte leakage from leaf tissues, especially with the leaf area that was damaged by freezing during cold acclimation (i.e, high, middle and low temperature treatments). However, the temperature at which 50% of electrolytes leaked from tissues occurs (T_EL50) was consistently lower by 2 to 4°C than the temperature at which 50% of leaf area was injured. When freezing tolelance as determind by the electrolyte leakage from leaf tissues was compared with that of the whole plant, at T_EL50 almost all leaves were severely injured and recovery of plant growth was substantially delayed. Because freezing tolerance of whole plants is expressed as the temperature at which the leaves are slightly injured and recovery is not seriously affected. Consequently, the freezing tolerance of whole plants of komatsuna and spinach may best be expressed as the T_EL15 or T_EL20 (at which temperature only 15 to 20% of the electrolytes leak from leaf tissues). The maximum of 100% electrolyte leakage is obtained from ground tissues or tissues subjected to a freeze/thaw cycle to -80°C.

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The effect of nitrogen (N) concentrations of hydroponic nutrient solution on the occurrence and development of downy mildew (Pseudoperonospora cubensis) in susceptible and resistant cucumber (Cucumis sativus L.) cultivars was investigated. A susceptible cultivar 'Pretty' and a resistant one 'Poinsett' were grown in hydroponic systems with three N levels (NO₃-N : 4, 8 and 16 me·liter^-1) in the nutrient solution, with or without fruit to change the nutrient condition of plant. In both cultivars, higher N levels of the nutrient solution and complete blossom thinning treatment tended to increase the shoot dry weight and leaf N content. The cultivar-specific resistance, shoot dry weight and leaf N content of both cultivars did not affect the number of days to appearance of the disease symptom under the high humidity condition subsequent to the start of treatments. However, the total lesion area of both cultivars correlated more closely with shoot dry weight than with leaf N content, indicating that the plant growth rate is a predominant factor governing the expansion of lesion area. Despite the similarity in shoot dry weight and leaf N content between cultivars, the lesion area of leaves of 'Poinsett' expanded slower than that of 'Pretty' and this resistance was not influenced by leaf N content. These results suggest the difficulty in suppressing the development of downy mildew in both cucumber cultivars by controlling the N concentrations (NO₃-N : 4 to 16 me·liter^-1) of hydroponic nutrient solution and leaf N content.

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Susceptible and resistant cucumber cultivars (Cucumis sativus L.) were grown with different nutrient solutions to examine the relationship between the characteristics of plant (shoot dry weight, osmotic pressure of petiole sap, and leaf mineral content) and the occurrence and development of cucumber downy mildew (Pseudoperonospora cubensis). Exp.1. The administration of different solutions (1/8, 1/2, 1(control), 3/2 unit of Enshi-shoho, nitrate-N at 20 or 2 me·liter^-1 and potassium at 12 or 1 me·liter^-1) revealed that more days to appearance of symptom was required by the resistant 'Poinsett' than the susceptible 'Pretty', independent of the leaf mineral contents. The total lesion area in 'Pretty' was bigger than that in 'Poinsett', but both of them were highly correlated with shoot dry weight but not to the leaf N or K content. When both cultivars were grown under a low K regime, the osmotic pressure of the petiole sap and leaf P, Ca and Mg content were the highest of all treatments ; the rate of lesion area in total leaf area, especially in 'Pretty' was significantly lower than that in control. Exp.2. The effect of double concentration of P, Ca and Mg (8, 16, 8 me·liter^-1) and osmotic pressure (4 or 8×10⁴Pa) of the nutrient solution were investigated. Doubling the osmotic pressure of the nutrient solution (2 units or adding NaCl to 1 unit of Enshi-shoho solution) increased the osmotic pressure of petiole sap, and suppressed the total lesion area in both cultivars. Hence, the total lesion areas of both cultivars were negatively correlated with the osmotic pressure of petiole sap. Especially doubling the Enshi-shoho to 8×10⁴Pa delayed the appearance of symptom and suppressed the total lesion area of 'Pretty' but yet shoot dry weight was unaffected. These results indicate that increasing the osmotic pressure of nutrient solution was more effective in suppressing expansion of lesion area of cucumber downy mildew than the increasing leaf mineral contents.

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Bulbs of Tulipa gesneriana L. 'Gander' were 1) stored at 20°C dry for 4-26 weeks and then chilled at 2°C for 8 weeks, or 2) stored at 20°C for 8 weeks and then chilled at -2°, 2°, 5° or 9°C for 6-36 weeks. The bulbs were forced and grown hydroponically at 20°C under 12-hr photoperiod. Relative growth rate from planting to anthesis was calculated for newly developing organs (shoots, floral organs, and daughter bulbs). The duration of storage at 20°C affected only the dry weights of new organs at planting much, and scarcely affected the number of days from planting to anthesis and the relative growth rates. The bulbs chilled for 6 weeks at -2° or 2°C flowered earlier and had higher relative growth rates of new organs than the bulbs chilled at 5° or 9°C. However, when the duration of chilling at 5° or 9°C was extended, the growth of new organs more advanced at planting and the flowering was earlier. Longer chilling resulted in 1) a decrease in dry weights of shoots and floral organs at anthesis in the bulbs chilled at -2° and 2°C, 2) failure to flower in the bulbs chilled at 5° and 9°C, and 3) an increase in dry weight at anthesis of daughter bulbs which is competitive with shoots at any temperatures. The enlargement of daughter bulbs at planting in the bulbs chilled at 2°, 5° and 9°C or their increased relative growth rate in the bulbs chilled at -2°C resulted in an increase in dry weight of daughter bulbs at anthesis. In these experiments, most of growth indexes i.e. number of days from planting to anthesis, dry weights of new organs at planting and anthesis, and relative growth rates of new organs, correlated nonlinearly with the duration of bulb storage at 20°C and chilling at different temperatures.

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A total of 134 Lilium japonicum plants were collected from 39 localities in Japan. Between November 1996 and July 1997, the plants were simultaneously cultured in a field, while their morphological and physiological characters were recorded and compared between accessions of the plants. Nine of the characters recorded were associated with a geographical region or cline. 86 flowered plants were divided into five groups by a principle component analysis based on eight of the nine characters. The groups suggested the following five geographical types : 1. Wakayama and Mie Prefecture (Kii-peninsula) type : late flowering, mid-size, narrow leaves, requiring more than eight weeks from emergence to anthesis ; 2. Ranging from Shizuoka to Hyogo Prefecture type : medium flowering, mid-size, narrow leaves ; 3. Ranging from Gifu and Ishikawa to Yamaguchi and Ehime Prefecture type : late flowering, large size, wide leaves ; 4. Ranging from Niigata to Tottori and Nara Prefecture type : slightly early flowering, slightly small size, wide leaves ; 5. Discontinuous Miyazaki and Tokushima Prefectures type : early flowering, small to mid-size, deeper color of perianth. Each area in types of 1 and 5 was separated, whereas areas in type of 2, 3, and 4 overlapped from the Kinki region northward to the Chubu region.

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