In sweet pea cultivars, a day-neutral winter-flowering type, which is cultivated for cut flowers in greenhouses in Japan, shows less phenotypic variety than a long-day summer-flowering type, which is cultivated in Europe. We would like to introduce the variegated-flower phenotype, which is currently found only in the summer-flowering type cultivars, into winter-flowering plants so as to expand the phenotypic diversity of the winter-flowering plant type. As the first step, we examined the inheritance of the variegated-flower phenotype and its possible linkage with pigmentation and flowering-type phenotypes. The segregation ratios of flower pigmentation phenotypes in progenies of crosses between variegated, fully pigmented, and white-flowered plants revealed that the variegated-flower phenotype is regulated by a single recessive gene, and the phenotype is epistatically and recessively suppressed by a pigmentation gene. We confirmed that the winter-flowering type predominant in Japan is regulated by a single recessive gene, as previously reported. Our data also indicate that the genes controlling the variegation, pigmentation, and flowering type segregate independently. These findings suggest that the winter-flowering phenotype can be fixed in the generation in which the phenotype appears, whereas the variegated-flower phenotype can be fixed at the generation in which the white-flowered phenotype does not appear in the self-progeny.

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In this study, we investigated the effects of rice husk addition to the propagation media on the root growth of blueberry cuttings. The number of surviving cuttings and weight of adventitious roots formed from the scion were highest in the medium that contained 50% rice husk. The total length of adventitious roots was highest in the medium containing 25% rice husk. There was a significant correlation between the growth of the adventitious roots of blueberry cuttings and the rice husk ratio in the propagation media. The values of the root zone parameters of blueberry cuttings were estimated to reach a maximum if the medium contains about 40% rice husk. From these results, we conclude that rice husk can be utilized as a propagation medium for blueberry cuttings.

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An investigation of the tree body and soluble protein content, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in the leaves at different plant ages (6 age brackets: 5, 10, 15, 20, 25, and 30-year-old plants after division) in tree peony ‘Luo Yang Hong’ planted in the same garden was undertaken to clarify the senescence phenomenon of tree peony. The results indicated that the new branch length, leaf length, and number of flower buds increased in plants which grew 5 to 15 years after division; however, they tended to decrease after 20 years. The results showed that new branch length became shorter with plant age in ‘Luo Yang Hong’. The protein content increased until 15 years after division, and then decreased; a negative correlation between SOD and plant age and positive correlation between MDA and plant age were demonstrated.

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To identify ways to improve the winter production of ‘Kyo-temari’ parthenocarpic tomatoes without the use of heating, we compared the effect (October 2011 to March 2012) of covering a poly tunnel with a newly developed polyvinyl alcohol and polyethylene (PVA) film instead of with a conventional film, i.e., polyvinyl chloride (PVC). Light transmittance at wavelengths of 2,500–25,000 nm was lower in the PVA than in the PVC film, so it retained a higher level of heat. The daily minimum temperatures in both tunnels were 0.5–2.8°C higher than in a non-covered tunnel during the same period, and the time during which the temperature remained below 5°C was shorter in the PVA-covered tunnel. The relative humidity and daily maximum temperature in this tunnel were lower than in the PVC-covered tunnel. The number of fruits was higher in the PVA-covered tunnel. Furthermore, the proportion of small ones was larger, and their Brix was significantly higher. Thus, covering tunnels with this newly developed film can increase the number and quality of ‘Kyo-temari’ tomato fruits grown in winter using a non-heated production system.

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We examined the effects of summer fertilization and pruning on nitrogen levels in the bleeding sap and petioles of ‘Muscat of Alexandria’ grape vines under forcing culture from December. In the summer of 1999, 9 vines under soilless-culture were treated with combinations of 3 different fertilization levels with 3 pruning procedures. The effects of the summer fertilization and pruning on inorganic nitrogen levels in the bleeding sap were not clear. The summer fertilization affected the nitrate nitrogen levels in the petioles at the berry set stage in the subsequent season, since the levels of nitrate nitrogen in 10 gN·m⁻² (10 g nitrogen application·m⁻²) and 15 gN·m⁻² were higher than that in 5 gN·m⁻² in the previous summer. The effect of summer fertilization on the inorganic nitrogen level was marked in the berry set stage; however, the difference in nitrogen levels among the fertilization treatments became indistinct at veraison. The summer pruning also affected the nitrogen levels in the petioles, since the levels of nitrogen in the vines pruned the previous summer were higher than the levels in those that did not undergo summer pruning. However, the severity of winter pruning did not affect the nitrogen levels in the petioles at any of the sampling times.

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The effects of the application timing and concentration of N-(2-chloro-4-pyridyl)-N’-phenylurea (CPPU) on fruit quality of ‘Shine Muscat’ grape were investigated. Spraying the bunch with 2 ppm CPPU before blooming or 10 ppm CPPU application in addition to 25 ppm GA₃ at full bloom significantly improved the tightness of the fruit bunch and decreased pericarp browning. Sensory tests revealed spraying the bunch with 2 ppm CPPU before blooming and 10 ppm CPPU application in addition to 25 ppm GA₃ at full bloom decreased the hardness of the flesh, increased the hardness of the pericarp, and decreased the palatability of the berry. Spraying the bunch with 2 ppm CPPU before blooming and 10 ppm CPPU application in addition to 25 ppm GA₃ at 10–15 days after full bloom markedly increased the hardness of the pericarp. Spraying the bunch with 2 ppm CPPU before blooming significantly increased the thickness of layers of epidermal and subepidermal cells. These results suggest that spraying the bunch with 2 ppm CPPU before blooming, dipping the bunch in a mixed solution of 25 ppm GA₃ and 5 ppm CPPU at full bloom, and dipping the bunch in a solution of 25 ppm GA₃ 10–15 days after full bloom, switching from the standard methods in Shimane prefecture (dipping the bunch in a mixed solution of 25 ppm GA₃ and 3 ppm CPPU at full bloom and dipping the bunch in a solution of 25 ppm GA₃ 10–15 days after full bloom), are effective for improving marketability.

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To elucidate the roles of plant growth regulators during fruit development in highbush blueberry (Vaccinium corymbosum L.), we investigated indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations, ethylene evolution in fruits during fruiting to ripening in ‘Berkeley’, and the ABA concentration and ethylene evolution at color stages of fruits in ‘Earliblue’, ‘Berkeley’, and ‘Jersey’. The IAA concentration increased during seed enlargement. During the maturation stage, the change in the ABA concentration resembled that of ethylene evolution. Ethylene evolution peaked at the same or one color stage earlier than the ABA concentration. The ABA concentration increased simultaneously with ethylene evolution in ‘Earliblue’ and ‘Berkeley’, and the ABA concentration increased later than ethylene evolution in ‘Jersey’. Furthermore, color stages with each of the ABA concentration and respiration rate peak, which is earlier, differed among cultivars. The relationship between ABA and anthocyanin concentrations seems to differ among cultivars. It was found that the ABA concentration changed simultaneously with fruit firmness as well as total soluble solid contents.

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Effects of the wavelength of night-break light on the inhibition of flower bud differentiation in chrysanthemum were investigated using the cultivars ‘Arajin2’ and ‘Iwanohakusen’. Wavelengths of 516, 593, 630, 663, 684, and 705 nm of light were produced using LED lamps. Effective wavelengths for inhibition in both ‘Arajin2’ and ‘Iwanohakusen’ were 593, 630, and 663 nm, and the most effective wavelength was 630 nm in ‘Arajin2’ and 593 and 630 nm in ‘Iwanohakusen’, respectively. The effectiveness of red light or a mixture of red and far-red light as a night-break light was compared using ‘Arajin2’ and ‘Iwanohakusen’. No difference in the inhibition of flower bud differentiation was observed in ‘Arajin2’, whereas the mixed light of red light and far-red light was more effective than red light to inhibit flower bud differentiation of ‘Iwanohakusen’.

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In experiment 1, ‘Kosui’ and ‘Gold Nijisseiki’ pear cuttings that had accumulated various amounts of chilling were treated with 0.5 and 1.0% hydrogen cyanamide or 2.5 and 10.0% hydrogen peroxide. Although the effect of both regents on promoting budbreak depended on their concentration and chilling accumulation, hydrogen cyanamide was more effective than hydrogen peroxide in most chilling values. One point zero percent hydrogen cyanamide applied at Chill Unit (CU) 600 was the most effective for breaking bud dormancy among the treatments. In experiment 2, 0.5 and 1.0% hydrogen cyanamide were used to treat adult ‘Kosui’, ‘Hosui’, ‘Gold Nijisseiki’, and ‘Niitaka’ trees at CU300, 600, 900, and 1,500, and thereafter the percentage of budbreak, pollen development, and the flowering period were observed. The response of budbreak in flower buds to hydrogen cyanamide varies with chilling accumulation and the cultivar. The effective period for ‘Kosui’ and ‘Gold Nijisseiki’ was during CU300 to 900, that of ‘Hosui’ was CU600 to 900, and that of ‘Niitaka’ was CU900. Clear differences in the breaking of bud dormancy were observed among these hydrogen cyanamide treatments. However, pollen growth and flowering were over 2 days earlier than in the untreated control due to the treatment irrespective of broken/unbroken dormancy.

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The effects of the irradiation time and light intensity for night-break using compact self-ballasted fluorescent lamps of red light on the flowering and spray formation of spray-type chrysanthemums were investigated with two types of cultivar, the autumn-flowering cultivar ‘Lineka Dark’ and the summer-to-autumn-flowering cultivar ‘Koiaromu’. Compact self-ballasted fluorescent lamps of red light (21 W), which have rich red light with a peak wavelength of 660 nm developed as a trial model, and incandescent lamps (75 W) as a control were used for light sources. The minimum photosynthetic photon flux density (PPFD) for the inhibition of flower bud initiation, resulting in normal spray flower formation, by irradiation with the compact self-ballasted fluorescent lamps of red light was smaller than that by irradiation with incandescent lamps under the same night-break time. In the autumn-flowering cultivar, the minimum PPFD for the inhibition of flower bud initiation was identified under 1-h night-break treatment with compact self-ballasted fluorescent lamps of red light, whereas no value was indicated with incandescent lamps. In the autumn-flowering and summer-to-autumn-flowering cultivars, as the product of the minimum PPFD and irradiation time was almost constant by irradiation with compact self-ballasted fluorescent lamps of red light, it is considered that the minimum PPFD is inversely related to the irradiation time on minimum fluence. These results indicate that the product of the minimum PPFD and irradiation time can be explained by the Bunsen-Roscoe law of reciprocity.

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The relation between the night-break-lighting period and light irradiance intensity to inhibit flower initiation in chrysanthemum was investigated using ‘Iwanohakusen’ and ‘Jinba’, major summer-to-autumn and autumn flowering cultivars in Japan, respectively. Plants were subjected to night-break with different light irradiance intensities for 20 to 60 or 70 days from planting. The required light irradiance intensity to inhibit flower initiation was evaluated by the number of nodes on the main stem at flowering. The required light irradiance intensity increased as the night-break-lighting period became longer in both cultivars. In ‘Iwanohakusen’, flowering could not be prevented by night-break when the lighting period reached 60 days. On the other hand, flower initiation in ‘Jinba’ was inhibited successfully by night-break even though the lighting period reached 70 days. These results indicate that the light irradiance intensity of night-break should be higher when the lighting period is longer than a threshold, depending on cultivars.

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On the assumption that consumers treat cut flowers continuously with sugar, the effects of continuous treatments with glucose, sucrose, fructose, and trehalose at different concentrations were investigated on the vase life of cut tulip flowers. Continuous treatments with all 4 sugars extended the vase life of cut flowers of ‘Ile de France’. Continuous treatments with glucose, sucrose, and fructose were more effective than that with trehalose. However, all continuous treatments except for that with 1% glucose caused damage to leaves to various extents. Continuous treatment with 1% glucose increased the relative fresh weight of cut flowers in all 12 cultivars examined, and significantly extended the vase life of cut flowers in 9 cultivars. On the other hand, the effects of pulse treatments with glucose were also investigated based on the assumption that producers treat cut flowers for a short period with sugars before shipping. However, such pulse treatments had no effects on the vase life of cut flowers of ‘Ile de France’. Thus, continuous treatment with 1% glucose is effective for extending the vase life of tulip cut flowers.

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The Perilla (Perilla frutescens L.) leaf has a short shelf life caused by browning, which occurs several days after harvest. The objective of this study was to identify the role of reactive oxygen species on browning of freshly harvested Perilla leaves by measuring their hydrogen peroxide (H₂O₂) content. Delayed light emission was measured as an indicator of photosystem degradation caused by physiological stress prior to the development of visible symptoms (wilting and browning). Leaves stored at 3°C at a low humidity (approximately 60%) lost weight at a rate of more than 25% per day, and were judged to be at the limit of marketability because of wilting before exhibiting browning. Under high-humidity storage (over 95%) at 3°C, browning occurred variably among leaves from 4 to 8 days after harvest. Browning occurred consistently when weight loss reached 26.3 1.1%. The content of H₂O₂ in leaves determined following serial weight losses of 10% revealed that browning leaves contained more than twice the H₂O₂ of leaves before browning, suggesting that increasing levels of H₂O₂ may induce browning in Perilla leaves. Weight loss was significantly correlated with values of delayed light emission (r = 0.67). Quick (several seconds), non-destructive measurement of delayed light emission can be a useful indicator of differing senescence rates in Perilla leaves.

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