Soils and roots of satsuma mandarin in 23 orchards in Ehime Prefecture, Japan, were surveyed for the presence of vesicular-arbuscular mycorrhizal (VAM) spores and infection. The number of VAM spores in 25g soil ranged between 160-3471, and in some orchards the percentage of VAM infection in the root was very low. A higher percentage of VAM infection was observed in orchards where the sod culture system was introduced and charcoal was applied, and in the plastic green houses where tree growth was vigorous. We observed that trees in orchards which produce the 'Hinomaru Brand' of satsuma mandarin, famous for its quality, also had a high rate of VAM infection. Proliferation of VAM fungi appeared to have been suppressed in orchards where considerable amounts of fertilizers were applied. The prolonged use of phosphorus (P) fertilizer resulting in over 50 ppm of residual PO₄^3- in the soil caused low VAM infection in satsuma mandarin roots.

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Soil-root interface water potential (Ψ_s·r) of a dry soil indicates the water status at the interface between the soil and the root, but it cannot be easily measured although it is proposed as an appropriate indication of plant water stress. Using an equation of Ohm's analog, we estimated Ψ_s·r and examined the maintenance and hysteresis of Ψ_s·r as well as xylem water potential (Ψ_X) and transpiration rate (E_A) in response to soil dehydration and rehydration for cherry-plum plants (Prunus×cistena) grown in three artificial soil mixes. These mixes were made of composted bark, peat, and sand (Mix-1), peat, bark, sand, and compost (Mix-2), and peat, sawdust, and sand (Mix-3). When water was withheld and the soil matric potential (Ψ_m) was lowered, plants grown in Mix-2 maintained higher Ψ_s·r as well as higher Ψ_X. However, when the soil mix was rehydrated, Ψ_s·r was always lower during the re-wetting than during the drying cycles. The relationship between Ψ_m and Ψ_s·r showed a strong hysteresis-like behavior. Hysteresis was the largest in Mix-2 and the smallest in Mix-3. Hysteresis of Ψ_X or E_A showed a similar trend to that of Ψ_s·r. The differences among soil mixes in hysteresis of Ψ_s·r might be related to the unsaturated hydraulic conductivity of substrates.

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S-genotypes of 13 apple (Malus x domestica Borkh.) cultivars and 10 progenies of 'Megumi' were identified by S-allele-specific PCR-RFLP analysis. The S-genotypes of 'Gala' and 'Fuji' were reconfirmed by the analysis. The S-genotypes of 'Kinsei' (S₂S₉) and 'Kizashi' (S₂S₃), were inconsistent with expected S-genotypes of their parents, indicating that they are derivatives from some other pollen parents having S₉- or S₃-allele. 'Tsugaru', 'Akagi', and 'Youkou' seem to have been produced by using pollen parents possessing S₇-, S₇- or S₉-allele, respectively. The S-genotype of self-compatible 'Megumi' was identified as S₂S₉ ; no mutation occurred within either of the S-genes. The reciprocal crosses between 'Megumi' and 'Hatsuaki' (S₃S₉) resulted in fruits with seeds, whereas those between 'Megumi' and 'Redgold' (S₂S₉) or 'Megumi' and 'Kinsei' (S₂S₉) resulted in no seeds. These results indicate that the self-compatibility of 'Megumi' is not attributable to defects within the S-genes.

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The reproductive organ of parthenocarpic persimmon (Diospyros kaki Thunb. 'Hiratanenashi') was sampled from -5 to 122 days after flowering (DAF). The endogenous levels of abscisic acid (ABA) and indole-3-acetic acid (IAA) were analyzed by gas chromatograph-mass spectrometry (GC-MS), and those of gibberellin (GA)-like substances were determined by the dwarf rice bioassay. Fruitlet abscission occurred mainly from 13 to 62 DAF and peaked at 41 DAF. A relatively rapid increase of fresh weight of fruitlets occurred until 41 DAF ; thereafter, the growth rate was moderate. The weight of the calyx increased until 13 DAF. The ABA concentrations in fruitlets was higher from flowering to 28 DAF than the remainder period. The calyx at 13 DAF had the maximum ABA concentration of all parts analyzed. IAA in the ovary/fruitlet increased about 18 times in content and 5 times in concentration from -5 to 0 DAF, and decreased to less than half in content by 13 DAF. The concentration of GA-like substances in fruitlets at flowering was also high, and increased at 41 and 122 DAF. At 5 days before flowering, the calyx had a higher concentration and content of three phytohormones than the ovary. These results suggest that the genetical increases of IAA and GA-like substances in the fruitlet of the parthenocarpic persimmon during flowering may result in continued growth, but the interaction between increased ABA and decreased IAA and GA-like substances in the fruitlet before fruitlet-drop may induce its abscission.

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Three-year-old 'Nijisseiki' pear (Pyrus pyrifolia Nakai) trees were treated twice with ¹³CO₂ in October (fall). The distribution of labeled ¹³C within the tree during dormancy and remobilization in the following season were determined. After leaf-fall, about 63% of the total ¹³C recovered from the tree was distributed in the roots. At anthesis the ¹³C content from the previous season's organs showed a significant decrease : the aerial organs decreased by about 53% and the roots by nearly 60%. About 35% of the total ¹³C recovered from the trees after leaf-fall was consumed by respiration until anthesis. New shoot, flower, and root growth accounted for 8.5%, 9.9%, and 3.9% of the total ¹³C recovered from the tree after leaf-fall, respectively. One month after anthesis, the ¹³C remaining in the previous season's organs, had further decreased, having been exported to the new leaves and current shoots. The ¹³C remaining in the fruitlets dramatically decreased because of the abscission of sepals, petals, stamens, and partial pistils (style and stigma). New roots had the highest concentration of ¹³C among all new organs. These data suggest that root systems play a special role in the storage of carbohydrates in young pear trees. All organs depend on carbohydrate reserves for spring growth, especially new roots which seem to depend on reserves for a longer time.

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In an effort to develop a male sterile line of shallot (Allium cepa L. Aggregatum group), a continuous backcrossing was carried out using A. galanthum Kar. et Kir. as a cytoplasm donor and the shallot as a nucleus donor. Meiosis and fertility in the F₁ hybrids, B₁, B₂, and B₃ progenies were examined. The F₁ hybrids had low pollen fertility, whereas the B₁ plants were pollen sterile or nearly so ; the B₂ and B₃ plants were completely pollen sterile. Pollen sterility observed in the backcross progenies was attributed to nuclear-cytoplasmic incompatibility because the pollen mother cells in most of these plants underwent normal meiosis. Although the seed fertility varied considerably among the progenies at each backcross generation, it could be improved with the advancement of backcrossing. PCR-RFLP analysis of chloroplast DNA proved that all the backcross progenies had the cytoplasm from A. galanthum. These results demonstrate that there is a realizable possibility of developing a male sterile line of shallot using this genetic approach.

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Flower senescence of Torenia fournieri was investigated in relation to ethylene production and sensitivity. Ethylene production of flowers increased with flower senescence ; pistil contributed to climacteric increase of ethylene production whereas other organs such as the petal, stamen, and calyx did not. Flowers were not sensitive to ethylene on the day of anthesis, but developed sensitivity as the flower senesced. Pollination and wounding of stigma markedly accelerated abscission of flowers, which was accompanied by climacteric ethylene production. Climacteric ethylene, following pollination and stigma wounding, was mainly produced by the pistil, particularly the style with stigma. The abscission of the intact, pollinated and stigma-wounded flowers was significantly inhibited by treatment with silver thiosulfate complex (STS), an ethylene action inhibitor. These results clearly show that the flower senescence of Torenia is mainly regulated by ethylene.

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Growth rates of Phalaenopsis callus differed depending on the volume of media. Whereas callus growth on 5-ml of medium slowed after 8 weeks of culture, that on 10- and 20-ml of media grew slower after 10 and 12 weeks, respectively. Taro extract (TE), potato extract (PE), coconut water (CW), and apple extract (APE) enhanced callus growth but the effects depended on the quantity of each supplement. TE was the best additive tested on callus growth when 50 to 200 ml·1^-1 were added. Banana homogenate (BH) and peptone had little effect on callus growth, whereas sweet potato extract (SPE) proved inhibitory at all levels tested. The effects of TE, PE, and CW depended on each callus. No synergistic effects of CW, TE, PE, and APE were observed.

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The effects of high CO₂ and/or low O₂ on browning and phenolic metabolism of loquat (cv. Mogi) fruits were determined. During a 5-day CA storage in 12% CO₂ with either air or 2% O₂, internal browning and brown surface spotting developed in loquat. The symptoms increased with extended storage. Chlorogenic, neochlorogenic and 5-feruloylquinic acid contents increased to a peak 5 days after the onset of CA storage, it took caffeic acid 10 days to reach its peak. The activities of phenylalanine ammonia-lyase (PAL), 4-coumarate : CoA ligase (CL), and hydroxycinnamoyl CoA : quinate hydroxycinnamoyl transferase (CQT) had a transitory rise to a maximum in 5 days before they rapidly decreased to very low levels. No injury symptoms were found in loquat fruits during the first 5 days of storage in air or 2% O₂ CA conditions. The levels of phenolic compounds decreased constantly throughout 20 days and there were little or no changes at all in PAL, CL, and CQT activity levels. The high CO₂ may initially induce the activities of PAL, CL, and CQT and cause an accumulation of phenolic compounds. The high activity of CQT caused the degradation of chlorogenic acid which led to its end product, caffeic acid, to accumulate.

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Bulbing response of two accessions of shallot and two accessions of A.×wakegi collected in Indonesia and two A.×wakegi accessions in Japan to daylength and temperature was investigated. All accessions formed bulbs under a 16-hr photoperiod. Both species also formed bulbs under a 12-hr daylength ; A.×wakegi formed bulbs even in an 8-hr daylength. Temperature of 20°C more promoted bulbing in both species than at 25 and 30°C.

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ACC (1-aminocyclopropane-1-carboxylate) synthase cDNA (AD-ACS1), isolated from kiwifruit 'Hayward', was expressed as a fusion protein coupled with glutathione S-transferase (GST) in Escherichia coli. The fusion protein exhibited ACC synthase activity. Northern blot analyses showed that the transcripts hybridized with AD-ACS1 accumulated only in the outer pericarp after a 24-hr ethylene treatment.

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Eextremely early maturing satsuma mandarin cultivars bear fruits with a few polyembryonic seeds which develop into very weak seedlings. Thus, breeding of extremely early maturing satsumas has been difficult. We conducted experiments to obtain seeds and promote seedling growth. The extremely early maturing satsuma mandarins : 'Miyamoto wase', 'Yamakawa wase', 'Ichifumiwase', 'Shirahama No.1', 'Haraguchi wase', 'Ooura wase', 'Takabayashi wase' and 'Kusumoto wase' which produce a few seeds were crossed with 'Kawano Natsudaidai' and other citrus species as pollen parents. The optimum temperature regimes for pollination to increase seed count are 31 to 32°C during the day and 15°C at night. Foliar applications of the growth regulators, daminozide and paclobutrazol, 10 days before anthesis effectively increased the number of seeds/fruit. Embryo bud grafting and inarching were effective methods for inducing vegetative growth. Shiikuwasha rootstock had the highest percentage of bud take and the greatest growth increament of embryo bud growth among the six rootstocks tested, but the hypocotyl diamater remained small. The growth of embryo bud grafts was promoted by inarching with rootstock of rough lemon.

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Relative light intensities in an apple (Malus domestice Borkh.) tree canopy were determined by measuring light quantity : photometrically (illuminance, lx), radiometrically (radiation, W·m^-2), and in quantum terms (photosynthetic photon flux, μmol·m^-2·s^-1). There was a strong positive correlation between relative illuminance and relative photosynthetic photon flux, measured on an overcast day. Relative photosynthetic photon flux was, however, 6.0% higher than relative illuminance. A strong correlation was also found between relative illuminance and relative cumulative photosynthetic photon for one day ; the latter was higher by 6.7% on an overcast day and 6.8% on a clear day. There was a strong positive correlation between the relative cumulative photosynthetic photon and the relative cumulative amount of global solar radiation for one day, while that of relative cumulative photosynthetic photon was 11% lower than relative cumulative amount of global solar radiation.

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The effects of shading on the translocation of ¹³C-photosynthates between 3- or 4-year old branches on mature trees during the rapid growth stage of cherry, pear and Japanese persimmon were investigated. 1. In all fruit trees, a very small quantity of ¹³C-photosynthates was exported into neighbouring lateral branches for 44 to 72 hours after a basal or terminal lateral branch was exposed to labelled CO₂. 2. When branches except that fed with ¹³CO₂ were shaded to about 50% of full sunlight from 5 days before to 3 days after the exposure, ¹³C-photosynthates did not translocate into the shaded branches in all three species. 3. The data on the distribution of ¹³C atom % ecxess among several organs within branches fed with ¹³CO₂ indicated the transport of photosynthates from the older branches to younger shoots was predominantly acropetal. 4. Therefore, we believe that the carbon budget of the 3- or 4-year-old lateral branches has the characteristics of a closed system during this phase of rapid fruit growth. Improvement of light environment around fruit bearing portion will be important at the stage, because photosynthates synthesized by leaves on adjacent, lower lateral branches do not contribute much to fruit growth.

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The effect of planting density on the leaf growth of 'Starking Delicious' apple trees (Malus domestica Borkh.), grafted on dwarfing (M.9 and M.26) and semi-dwarfing (M.7 and MM.106) rootstocks, was studied. 1. On all four rootstocks, the mean area per leaf and the mean dry weight per leaf tended to decrease, but the specific leaf area (SLA) increased, as the density increased. 2. On all rootstocks, the leaf dry weight per tree, the leaf area per tree, and the leaf number per tree decreased, but the leaf area index (LAI) increased, as the density increased. 3. The relationship between the planting density (ρ) and the leaf area per tree (u), the leaf dry weight per tree (w) or the LAI (F) could be represented by the following reciprocal equations, 1/u=A_uρ+B_u (4) 1/w=A_wρ+B_w (5) 1/F=A_u+B_u/ρ (7) where A_u, B_u, A_w and B_w depend on the tree age and rootstocks. 4. The relationship between the trunk cross-sectional area (θ) and the leaf area or the leaf dry weight per tree could be prescribed by the following equations, u=H′θ^h (8) w=H″θ^h (9) where H′, h′, H″ and h″depend on the tree age and rootstocks. 5. When the LAI at the optimum planting density (ρ_opt) is defined as optimum LAI (F_opt), the F_opt can be expressed by the following equation, F_opt=ρ_opt/(A_uρ_opt+B_u). (10) Based on A_u and B_u obtained from Eqs. (4) and (8), and ρ_opt obtained from Eq. (3), the F_opt estimated by Eq. (10) had values of 3∿4, regardless of tree age and rootstocks. 6. No relationship was found between the fruit yield per hectare and the LAI. However, a high correlation coefficient (r=+0.865^**) exists between the fruit yield per hectare and the fruit production rate per unit leaf area, independent of tree age and rootstock, indicating that fruit yield per hectare depends on fruit production rate per unit leaf area.

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The effect of seaweed extracts on the hyphal growth of a vesicular-arbuscular mycorrhizal (VAM) fungus, Gigaspora ramisporophora Spain, and its development on trifoliate orange roots was investigated. The seaweeds, Konbu (Laminaria japonica Areschoug) and Wakame (Undaria pinnatifida Suringar), were extracted with 75% methanol (MeOH) ; these crude extracts were fractionated by a flash chromatograph equipped with a Chromatorex ODS DM1020T column (20x250mm) and eluted with 0, 10, 25, 50 and 100% MeOH. Both crude extracts had no effect on hyphal growth of VAM fungi. However, the 25 and 50% MeOH eluates of Konbu (0.1 and 0.3gDW), and the 10 and 25% MeOH eluates of Wakame (0.1 and 0.3gDW) stimulated the growth of VAM hyphae. The most effective hyphal growth stimulation was in the 25% MeOH eluates of Konbu (0.3gDW). Crude extracts of Wakame (1.0gDW) and Konbu (0.2 and 1.0gDW) increased the percentage of VAM infection of trifoliate orange roots, compared with the control. The 25% MeOH eluates of Konbu (1.0gDW) and Wakame (1.0gDW) significantly stimulated the percentage of VAM infection as compared with the crude extracts. The crude extracts and 25% MeOH eluates from both seaweeds had no significant effect on the growth of trifoliate orange seedlings, compared with the control. The results suggest that the extracts, particularly the 25% MeOH eluates obtained from both seaweeds, contain growth stimulatory substances for VAM fungi, and that the eluates applied to the soil stimulate VAM development in trifoliate orange roots.

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The internal ethylene concentration (IEC), 1-aminocyclopropane-1-carboxylate (ACC) contents, N-malonyl-ACC (MACC) contents, ACC synthase activities, and ACC oxidase activities were determined on intact (early-maturing) and detached 'Tsugaru' and 'Akane' Apples to study the mechanism of ethylene biosynthesis. The effects of plant growth regulators, amino acids, and minerals on ethylene evolution by sliced and whole fruits were also examined. The IEC in 'Tsugaru' fruit rapidly increased from late August to September, reaching 300 μl·l^-1 and 800 μl·l^-1 in intact and detached fruit, respectively. In contrast, the attached fruit of 'Akane', IEC was only 5.6 μl·l^-1 at its climacteric peak, whereas in detached fruits, it was less than 10 μl·l^-1 during storage. ACC content and ACC synthase activity were both higher in 'Tsugaru' than they were in 'Akane' fruit. These results indicate that ethylene biosynthesis in both cultivars is regulated by ACC synthase activity, as reported previously for other cultivars, such as 'Fuji' and 'Senshu' (Suzuki, et al., 1997). Flesh slices dipped in 10 and 100 ppm GA₃ had slightly reduced ethylene evolution. In whole fruit similarly treated with GA₃, the ethylene evolution significantly decreased 2 weeks after treatment in comparison with the control ; the decrease continued throughout the treatment period. Treatment with 10 mM or 100 mM aspartic acid and 100 mM glutamine significantly reduced the ethylene evolution in sliced tissue, whereas 100 ppm Ca and NH₄ -N tended to reduce ethylene evolution ; contrarily, the same treatments at 300 ppm stimulated it.

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The effects of covering fruits with polyethylene bags and spraying with Ethephon and calcium carbonate (Clefnon : 95% pure calcium carbonate) on the transpiration rate and the occurrence of watercore in the Japanese pear 'Housui' were studied. 1. Pears which were covered with polyethylene bags or sprayed with Ethephon had more symptoms of watercore than did the non-treated, control fruits. 2. Fruits sprayed with 3% Clefnon produced less watercore symptoms than did the non-treated fruits, especially after eight treatments at 2-week intervals after flowering. A 1% Clefnon solution was less effective than the 3% one. However, eight applications of 3% Clefnon at 2-week intervals after flowering to reduce watercore and surface residue of calcium carbonate at harvest. No differences in fruit quality were detected between treated and non-treated fruits. 3. The temperature of the fruit surface treated with Clefnon was cooler than that of the non-treated fruit ; whereas it was warmer on fruits sprayed with Ethephon than the control fruit. We believe that Clefnon promoted the transpiration rate of the fruit but Ethephon did not. We attribute the inhibition of watercore by Clefnon to this acceleration of the transpiration rates.

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A survey was taken on the occurrence of black root rot of chestnut, the amount of roots and the soil properties in two red-yellow soils and in Andosol. Furthermore, an experiment was done to compare the differences in growth of chestnut seedlings among these soil species and a granite weathered sandy soil. 1. The occurrence of the black root rot was more extensive in the chestnut groves on the brown forest soil that had been improved topographically and where red-yellow soil constituted the topsoil. In contrast, the occurrence was significantly less in groves on Andosol. 2. In Andosol, the amounts of fine root below 1 mm in diameter were more numerous than in the red-yellow soil. 3. In the three phase distribution, the red-yellow soil had a larger solid phase volume and a smaller gaseous phase volume than the Andosol. Soil water tension throughout the year fluctuated more in the red-yellow soil than it did in Andosol. 4. Potted chestnut seedlings had more roots less than 5 mm diameter and more mycorrhiza-infected roots in the Andosol compared to those grown on red-yellow soil. These findings suggest that in the Andosol, the occurrence of black root rot is less frequent because the chestnut trees undergo less water stress. This reduced water stress in the Andosol is attributed to the presence of more fine roots, minimizing soil moisture fluctuation throughout the year compared to the red-yellow soil and granitic, sandy soils.

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Black root rot disease of chestnut (Castanea crenata Sieb, et Zucc.) is caused by the fungi (Macrophoma castaneicola and Didymosporium radicicola). To establish methods for controlling black root rot of chestnut trees, resistant rootstocks were sought among seedlings of shibaguri (wild species of Castanea crenata Sieb. et Zucc.) and chestnut cultivars. A survey on the presence of the black root rot in chestnut cultivars that had been grafted on native shibaguri and those field-grafted onto open-pollinated seedlings of cultivars derived by direct seeding in the field was conducted. 1. No one of the open-pollinated shibaguri seedlings found in five prefectures was resistant to black root rot ; neither were the nine cultivars tested. 2. Fewer field-grafted cultivars on shibaguri seedlings were infected with black root rot than clonally grafted nursery plants which were transplanted. 3. Trees of 'Tsukuba' on 2-years-old seedlings derived from direct seeding in the field were attacked by black root rot more frequently than were the transplanted nursery plants of the same cultivar. 4. That less black root rot infection on chestnut cultivars grafted on native shibaguri rootstocks is attributed to the better development of their rootstocks. However, more older trees tend succumb to the disease because the fungi seem to spread from one trees to the next in the orchard.

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The relationship between tree age and each tree growth parameter and that among the dry weights (DW) of each organ were examined in 5-, 10- and 24-year-old Fuyu tree (Diospyros kaki L.), a total of 23 trees. The trunk cross-sectional area (TCSA), total shoot length (TSL), shoot number per tree (SN), and DW of each organ increased with the age of the tree. The percentage dry weight of leaves, current shoots, and fine roots were lower, and those of old branches and thick roots were higher in the 24-year-old trees than they were in the younger ones. The dry weight ratio of fine roots to rootstocks was lower in older trees but the top-root ratio did not vary with age. A significant correlation was observed between each tree growth parameter and DW of scion and rootstock. TCSA, TSL, leaf number, and area were correlated with DW of each organ, but the correlation coefficient between the area occupied by the tree canopy and DW of each organ was somewhat low. The regression equation between scion DW (Y kg) and TCSA (X cm²) was : Y=-3.577+0.230X (r=0.936) The regression equation between rootstock DW (Y kg) and TCSA (X cm²) was : Y=-1.708+0.128X (r=0.932) Furthermore, a highly significant correlation was observed between scion DW (X kg) and rootstock DW (Y kg), and the regression equation between them was : Y=1.029+0.529X (r=0.943) In conclusion, scion DW and rootstock DW can be estimated from TCSA easily with a high precision.

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Seasonal changes in dry matter accumulation and partitioning in the shoots, roots, and leaves in 5-year-old 'Kousui' and 'Housui' Japanese pear (Pyrus pyrifolia Nakai) trees on 'Yamanasi' rootstocks grown in a restricted root beds (160 l/tree) under a transparent film were investigated. Scion top and total tree fresh and dry weights increased significantly in both cultivars as the growing season proceeded ; the annual fresh and dry weights gains, respectively, per tree were 18kg (82 t/ha) and 3.37 kg (15 t/ha) for 'Kousui' and 21 kg (96 t/ha) and 3.75 kg (17 t/ha) for 'Housui'. 'Housui' trees consistently outyielded those of 'Kousui'. Likewise, the annual dry matter gains per unit leaf dry weight and per unit leaf area which increased significantly during the growing season, respectively, were 6.33 kg and 0.54 kg in 'Kousui' and 6.59 kg and 0.53 kg in 'Housui' ; there are no significant differences in weights between the cultivars. In 'Kousui' and 'Housui', the percentages of assimilates partitioned into current shoot, leaf and fine root increased as the shoots elongated. Fruits assimilated dry matter fastest during their enlargement period. After harvest, the percentage of assimilates partitioned into old wood increased until autumnal leaf fall. In both cultivars, the percentages of assimilates partitioned into the fruit, current shoot, old wood, leaf, and roots were about 31, 18, 16, 15, and 19%, respectively. Dry matter gains per unit leaf dry weight per day were high from mid-April to early September in both cultivars ; subsequently, they decreased until leaf fall. Dry matter accumulation was rapid during early June to early August after which the rate gradually decreased untill leaf fall. About 42 and 44% of the dry matter produced during the year were gained in early July, whereas 79 and 85% were gained prior to early September in 'Kousui' and 'Housui', respectively.

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Varietal differences of pollen tube growth among self-, cross-incompatible and cross-compatible pollinations were investigated by semi vitro assay using detached styles in Japanese pear (Pyrus serotina Rehd. var. culta Rehd.) cultivars. Among the 52 self-compatible and -incompatible cultivars, the pollen tubes grew in considerably different ways. The percentages of styles with protruding pollen tubes from the basal cut end ranged from 0 to 47. Pollen tubes of 'Shinsetsu', Nihonyamanashi, self-compatible 'Osa-Nijisseiki', and self-compatible strains obtained from 'Osa-Nijisseiki' grew well, and those of 'Okusankitsu', 'Yasato', 'Kikusui', 'Nijisseiki', and 'Kisui' did intermediately, whereas pollen tubes of 'Shinsui', 'Chojuro', 'Kimizukawase', 'Hohsui', 'Kohsui', and 'Kohzo' grew poorly. Similar tendencies were observed when the number of pollen tubes protruding from the basal cut end among cultivars was counted. Generally, pollen tubes of cultivars derived from 'Nijisseiki' grew better than did those of 'Kohsui' and 'Shinsui', indicating that the rate of pollen tube elongation of cultivars is a heritable character. In cross-incompatible and -compatible pollination combinations, the pollen tubes grew quite differently, depending on the parental combinations. The percentages of styles with protruding pollen tubes from the cut end ranged from 0 to 40 in cross-incompatible combinations, and from 26 to 97 in cross-compatible ones. By using excised styles shortened to 1/2 or 1/3 of the original length, the percentage of styles with protruding pollen tubes from the cut end improved. The growth of self-and cross-incompatible pollen tubes became much better so that the promotion patterns were classified as follows : 1) tube elongation becomes better as the style is shortened ; 2) tube elongation becomes better but there are no differences between 1/2 and 1/3 reduction in style length ; 3) pollen tube elongation becomes better only in the 1/3 style length, and 4) no change was found. These differences indicate that the inhibition of pollen tube growth occurs in different parts of the style among respective cultivars.

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To regenerate plants by ovary culture of pea (Pisum sativum L.), the effects of the developmental stage of explants and cultural conditions on seed formation and germination were investigated. 1. The more mature the explants were, the more frequently they formed seed and germinated in an ovary, ovule and embryo culture. Among these three culture methods, the ovary culture regenerated plants most efficiently. Therefore, it seems suitable for accelerating generation turn-over by in vitro culture of the pea. 2. When an excised ovary was cultured before anthesis, the ovule failed to grow, whereas after anthesis, the older the ovary was, the faster the ovules grew and germinated. 3. Ovules of 'Misasa', 'Oranda' and 'Kishu-usui' grew and germinated in an ovary culture. 4. In an ovary culture, the ovule germinated faster at 25°C than at 20°C. 5. The addition of NAA 0.5 mg·liter^-1, NAA 1.0 mg·liter^-1 or BA 1.0 mg·liter^-1 to the medium promoted the growth of the ovule in an ovary culture but the addition of GA₃ 0.5 mg·liter^-1 suppressed it. 6. By changing the stopper of the test tube to cotton instead of aluminum foil after germination of the 'Misasa' ovule in an ovary culture, shoots grew well ; 100% of the plants flowered and bore fruit in vitro.

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To establish a cultivation system for the production of high quality cucumbers (Cucumis sativus L. cv. Kagafutokyuri), differences in nitrogen levels in the leaves between a non-bitter line and a bitter line and in the leaves and fruits between the bitter ones and the non-bitter ones were compared. A percentage of bitter fruit was higher in the bitter line than in the non-bitter line. Stem length, leaf weight, and root weight per plant were larger in the former than in the latter. The total leaf nitrogen and amino acid-N levels were higher in the bitter line than in the non-bitter line, but the nitrate ion level was lower in the former than in the latter. On plants grafted on Cucurbita ficifolia Bouche, the leaves on the upper node were more bitter than those in the lower node. The degree of bitterness of the upper leaf or fruit corresponded to the total nitrogen and amino acid-N levels. We concluded from these results that high total nitrogen and amino acid-nitrogen levels in the leaf induce bitterness in leaves and fruits by promoting nitrogen metabolism, which in turn favors the enzymatic synthesis of cucurbitacin C, the bitter factor.

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The conditions to eliminate the operation of acclimatization of tissue-cultured strawberry plantlets were examined. Strawberry plantlets cultured in the rooting medium following propagation culture were transplanted into small pots without the operation of acclimatization, and were raised on the shelf system with manual irrigation. The percentage of plantlets taking root and surviving in the pots after transplantation increased, as the culture period in the rooting medium was lengthened. And, the survival percentage of the plantlets, cultured for 54 days in the rooting medium, after potting reached 95 to 100%. Even in cases where the plantlets were cultured for only 35 days in the rooting medium, the plantlets which had five or more leaves, or whose longest roots measured 40 mm or more were all able to survive after potting. In the suitable season for potting, from late April to early June, the plantlets, cultured for 54 days in the rooting medium, were potted several times without the operation of acclimatization, and were raised with cheesecloth cover and water spraying three times per day by microsprinklers. Consequently, 96 to 100% of these plantlets survived, indicating that the operation of acclimatization of well-cultured strawberry plantlets is not necessary prior to transplanting them into the field.

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The growth of the pod and the number of seed on in vitro cultured pea (Pisum sativum L. var. Kinusaya) were examined. When the pod or immature seed born in vitro was cultured, the effect of the developmental stage of the explants on the period for alternation of generation was investigated. Combining the data, a way of accelerating generation turn-over in vitro and the use in practical breeding were considered. The results obtained are ; 1. Pea cultivars produced 2.0-2.4 seeds per plant in vitro. 2. The enlargement and ripening of seed in vitro were advanced at 25°C than were those at 20°C. 3. When 25-day old pods or 30-day old seeds after anthesis were picked and re-cultured in vitro, the alternation of generation of the pea was completed in 82 days. 4. The plants set many pods in vitro, when the previous pod was removed at an early developmental stage. 5. The seed ripened in vitro could be sowed in the field without acclimation. These results indicate that by accelerating the generation turn-over by in vitro pod culture, the breeding period of the pea can be shortened.

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The effects of low temperature on the sugar and ascorbic acid contents of Komatsuna (Brassica campestris L.) plants grown under limited solar radiation in the greenhouse were evaluated. Komatsuna plants were grown in a greenhouse in which the mean air temperature was maintained between 13°C and 15°C (defined as the "cool temperature" condition). The solar radiation in the greenhouse fluctuated between 2 and 4 MJ/m²·day^-1 during the experiment. When Komatsuna plants grew to about 20cm height, they were transferred to a greenhouse in which the mean air temperature flucturated between 2°C and 3°C (defined as the "cold temperature" or "cold treatment"). The total sugar contents in leaf blades and in petioles of Komatsuna plants increased rapidly as a function of the cold treatment. The total ascorbic acid content in the leaf blades increased rapidly after the initiation of cold treatment, whereas that content in the petioles increased gradually. On the other hand, the composition of the leaf blades and petioles in the Komatsuna plants did not change when grown continuously in the cool plot. The data show that cold treatment promoted the per unit area production of the total sugar and total ascorbic acid. These results indicate that cold treatment could improve the nutritional qualities of Komatsuna plants, even under limited solar radiation in winter.

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The effects of air temperature and light intensity on β-carotene concentration in spinach and lettuce leaves were investigated to seek means of enhancing β-carotene concentration in these crops. β-carotene concentrations in these crops decreased with increasing fresh weight, independent of air temperature and light intensity treatments. During a certain period of growth, the effects of air temperature and/or light intensity were not clear because there were differences in growth among the treatments. On a fresh weight basis, β-carotene concentration increased in plants exposed to low air temperature and/or high light intensity. Low air temperature and/or high light intensity are valuable factors for increasing β-carotene concentration in leafy vegetables because they are nutritions and are sold fresh. Though the β-carotene concentration in spinach and lettuce are different, the effects of air temperature and light intensity on β-carotene concentration are the same. These results indicate that the principle for increasing β-carotene concentration is applicable to other leafy vegetables.

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Various media were tested for in vitro germination of pollen grains of radish and Brassica campestris. The basal medium contained 50 mg·liter^-1 H₃BO₃, 100 mg·liter^-1 CaCl₂ and the pH was adjusted to pH 5.8. Species of pollen grains tested were : radish (Raphanus sativus L.) 'Harumaki Minowase', 'Ryujin Miura', 'Motohashikei Taibyou Minowase', and four of Brassica campestris L. 'Hiroshimana' and 'Santousai' (non-heading chinese cabbage, pekinensis group), 'Mibuna' (japonica group), and Pak-choi 'Chingensai' (chinensis group). The results obtained were as follows ; 1. The basal medium containing 0.43M sucrose yielded the highest germination rate of radish pollen compared to that at 0.29 or 0.58M sucrose. 2. Among the media adjusted between pH 5.8∿12.0, pH 9.0 gave the best pollen germination. 3. Germination rate was improved by using buffer solutions of pH 8.0 and 8.5, such as Taps, Tris, MES, boric acid or phosphoric acid buffer compared to distilled water. Taps and Tris buffers were most effective, followed by boric acid and barbital buffers. 4. Cholic acid, cetylmethyl ammonium bromide and sodium lauryl sulfate promoted pollen germination of radish. 5. Pollen grains of mother plants of the same age grown under 10∿25°C during May∿June, and October∿December had the best germination rate, whereas those obtained between July∿September had the poorest rate.

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Reciprocal crosses between Hydrangea macrophylla f. hortensia (Lam.) Rehd. and H. arborescens L. were made to introduce useful characters of H. arborescens into H. macrophylla. The experimental results are summarized as follows. 1. Pollen grains of H. macrophylla and H. arborescens were stored at -20°C, 5°C, and 20°C with CaCl₂. The pollen viability was tested by in vitro pollen germination : the pollen grains, stored at -20°C, retained germination capacity for a long term, but those stored at 5°C and 20°C lost their capacity within 5 months and 5 days, respectively ; however, when the pollen grains of both species were stored at -20°C for 11 months, over 36% of the pollens of H. macrophylla germinated, whereas none of the pollens of H. arborescens did. 2. Fresh and stored pollens of both species germinated well on the stigma in self-, intraspecific, and interspecific pollinations and the pollen tubes elongated straightforwardly to the ovary. 3. In self-and intraspecific crosses, both Hydrangea species easily set capsules and produced many mature seeds. However, the number of seed per capsule depended on cross combinations : H. macrophylla produced 10 to 54 mature seeds, whereas H. arborescens produced 19 to 31 seeds. 4. Mature seeds from self- and intraspecific crosses germinated well under in vitro and in vivo ; 58 to 85% of H. macrophylla and 14 to 52% of H. arborescens seed germinated. Pubescence was observed on the first true leaf of the latter seedlings but not on that of the former. Pubescence is an important criterion for distinguishing H. macrophylla from H. arborescens. 5. A few mature seeds were produced from 3 of 5 interspecific crosses of H. macrophylla×H. arborescens, but no seeds were produced in the reciprocal crosses. The seeds germinated in vitro and the resulting seedling showed arrested growth after the development of cotyledons, and then it died. 6. In the interspecific crosses of H. macrophylla×H. arborescens, seedlings were obtained by rescuing and culturing ovules excised 60 to 150 days after pollination, but all seedlings died after the cotyledons developed. In the reciprocal crosses, only one seedling was obtained from ovules excised 60 days after pollination but it died at the cotyledonal stage. 7. Adventitious buds formed on the cotyledons of seedlings which were obtained through ovule culture of the interspecific crosses between H. macrophylla and H. arborescens. When buds were excised and transplanted to the basal medium supplemented with 1mg/l BA, they grew into plantlets. Because the leaves on these plantlets are pubescent, they seem to be hybrids between H. macrophylla and H. arborescens.

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Shoots of 24 rose varieties were inoculated in vitro with Agrobacterium tumefaciens (crown gall bacteria) to test for their resistance. The resistance to crown gall disease was classified into two phenotypes in this study : the resistance to tumor formation and to tumor development. The variety 'PEKcougel' was the most resistant, no tumor was formed. The yellow varieties 'Dukat' and 'Golden Emblem' were not resistant to tumor formation and development, 87% and 65%, forming galls, which grew to 3.62 and 2.43 (mm×mm), respectively. Whereas, 100% and 95% of 'White Dream' and 'Purple Rain' stems developed tumors respectively ; only 7% of 'Lifirane' developed tumors. However, once infected, tumor of 'Lifirane' grew to 4.75 (mm×mm). 'Lifirane' was the most resistant to tumor formation, but it was not resistant to tumor development. In Hybrid Tea varieties, the disease incidence and tumor sizes ranged from 0 to 65% and from 0 to 4.75 (mm×mm), respectively.

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