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Hyeon-Hye Kim and Kiyoshi Ohkawa

As a new product in the floricultural market, Zephyra elegans D. Don, shows great potential. It is a new product, so there is little known about its physiology. In this study, the growth cycles and the effects of day/night temperatures on flowering control of this new product were investigated. Stems elongated gradually during the growing season but more slowly after flowering. Original corm fresh weight decreased with increasing daughter corm fresh weight. Druing the growing season, the original corm dies after producing usually one daughter corm. The high ambient temperature of summer adversely effected shoot emergence. The optimum day/night temperature regimes for shoot emergence was 15/10 °C and for growth and flowering it was 20/15 °C. Under these conditions, it is possible to produce Zephyra elegans D. Don year-round.

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Kiyoshi Ohkawa, Youichi Kasahara, and Jung-Nam Suh

The effects of silver-containing compounds used for prolonging the vase life of cut rose (Rosa hybrida L. `Asami Red') flowers were investigated. Silver nitrate and RNA-Ag+tris (a ribonucleic acid-silver complex and trishydroxymethylaminomethane) increased the vase life by 2.7 days and prevented bent neck of cut rose flowers compared with the control, whereas silver thiosulfate (STS) did not have a significant effect on longevity. Fresh weights of the rose stems pretreated with silver nitrate or RNA-Ag+tris were maintained along with longer vase life. There were higher amounts of Ag+ in the basal parts of the stem in these treatments compared with STS treatment. Bacterial count at the cut surface of stems treated with either silver nitrate or RNA-Ag+tris were lower than STS-treated or control stems. These results indicated that the primary effect of silver-containing compounds on `Asami Red' roses was antimicrobial.

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Paola Yañez, Hajime Ohno, and Kiyoshi Ohkawa

Photoperiodic response and vase life of 28 cultivars of ornamental sunflower (Helianthus annuus) were evaluated. Plants were grown in a glasshouse under 16-hour long-day (LD) or 11.5-hour shortday (SD) conditions. Most cultivars (82%) reached visible flower bud stage earlier under SD than LD. All cultivars flowered under both SD and LD conditions, but in 26 cultivars (92.9%) flowering was significantly delayed under LD, demonstrating them to be quantitative SD plants. The delay was variable among the cultivars. A 14-day or greater hastening of flowering was found under SD in 18 cultivars. Photoperiod had no effect on flowering of `Lemon Eclair' and `Moonshadow'; these cultivars are day-neutral (DN) plants. For some cultivars the LD photoperiod increased plant height and the number of nodes and leaves. Vase life varied from 6.8 to 11.2 days depending on the cultivar, but no photoperiodic effect was found.

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Jung Nam Suh, Kiyoshi Ohkawa, and Beyoung Hwa Kwack

Response of cut Cymbidium flowers to emasculation was investigated. All Cymbidium cultivars that we examined produced ethylene during senescence. There were marked cultivar differences in the changes of fresh weight, ethylene production, and lip coloration after emasculation. In the case of `Venus', flower emasculation did not alter fresh weight, ethylene production, or lip coloration. There were differences in ACC oxidase in vivo activity among the three cultivars before and after emasculation. There was a correlation between the initial ACC oxidase activity and time to lip coloration in the emasculated flowers, but not in control flowers. It was suggested that the initial ACC oxidase activity of the column may be related to flower response to emasculation rather than vase life during senescence.

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Kiyoshi Ohkawa, T. Yoshizumi, M. Korenaga, and K. Kanematsu

The effects of seedling age and temperature regimes and durations on the reversal of Eustoma grandiflorum (Raf.) Shin. heat-induced rosette formation were clarified. When E. grandiflorum seedlings were grown in a natural-light phytotron (600-800 μmol·m-2·s-1) for 4 weeks at 33/28C (12-h day/12-h night) from germination to the four true-leaf stage, the optimum temperature and duration required to break rosette formation was 15C for 4 weeks with continuous illumination (35 μmol·m-2·s-1). However, when seedlings were grown for 12 weeks at 33/28C from germination to the eight true-leaf stage. shoot elongation required 6 weeks at 10C.

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Kiyoshi Ohkawa, Hyeon-Hye Kim, Emiko Nitta, and Yukinori Fukazawa

Leucocoryne, a native to Chile, has violet, blue, or white flowers and is increasing in popularity as a cut flower. The effects of storage temperature and duration on flower bud development, shoot emergence, and anthesis were investigated. Bulbs stored at 20 to 30 °C for 22 weeks produced 3.4 flower stems per bulb between March and April. Bulbs stored at 20 °C flowered earliest, followed by those stored at 25 °C. Bulbs stored at 30 °C flowered last. After 16 weeks of storage at 20 °C, a further 2 weeks dry storage at 15 °C before planting resulted in 1 month earlier flowering with no reduction of the number of flowering stems. As dry storage at 20 °C increased to 11 months, the time to emergence and flowering decreased. After dry storage at 20 °C for 12 months, the primary flower stems aborted and secondary stems then developed. Secondary and tertiary flower stems tend to commence flower bud development after the flower bud on the primary flower stem has reached the gynoecium or anther and ovule stage of initiation.

Open access

Shinsaku Takayama, Masanaru Misawa, Yoshiki Takashige, Hiroshi Tsumori, and Kiyoshi Ohkawa

Abstract

The transplanting to soil of bulblets of Lilium longiflorum Thunb., L. × formolongi, L. speciosum Thunb., and L. auratum Lindl., grown on Murashige and Skoog’s medium, was investigated in relation to dormancy. Leaf emergence from tissue-cultured bulblets was inhibited after transplanting into soil without low-temperature treatment. To break dormancy, low temperature (5°C) treatment for 70 days was required when bulblets were produced in the medium with 30 g/liter sucrose, while 120 to 140 days were required when bulblets were produced in the medium with 90 g/liter sucrose. In vitro-produced bulblets of L. longiflorum grew well in soil and about 40% of the bulblets flowered in a year.