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Jong-Suk Lee and Ki-Sun Kim

In spite of its rapid growth in recent years, the floricultural industry in Korea is rather small with respect to total acreage and number of growers engaged, product value, international trade, and production facilities and technics involved. The production status will be introduced with slides. Nevertheless, variable climatic conditions of the temperate zone such as the distinctive 4 seasons favor the prosperous growth of a variety of vegetation throughout the Korean peninsular. Thus, it has been wellknown that many ornamental plants native to Korea have good potentials for horticultural use. The morphological characteristics of a few selected plants will be introduced along with slides. These plants include Aster spp, Iris spp, Gentiana soabra, Chrysanthemum zawadski, Pulsatilla koreana, Cymbidium spp, Calanthe spp, Dendrobium moniliforme, Abeliophyllum distichum, Ardisia spp, Hibiscus syriacus, and many others.

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Ki Sun Kim and Ji Ny Lee

There are many ground covers native to Korea. Liriope spicata is very promising for landscaping purposes due to its waxy and dark-green foliage fragrant and pink flowers, as well as fruit. However, seeds harvested during late fall do not germinate at all if they are sown in spring. Thus, series of experiments were conducted to undestand the physiological mechanism of dormancy breaking and germination of Liriope spicata Lour. seeds and to determine the effective methods for enhancing seed germination. Fruit were harvested in October through December. Depulped seeds germinated rapidly, indicating that one or more inhibitors may be present in the pulps of fruit and/or seeds. GA3, NaOCl, NaOH, and H2SO4 treatments and dry cold treatment had no effect on germination, whereas wet, cold seed treatment for at least 30 days promoted germination up to 75% within 15 days. Optimum conditions for germination was continuous dark and 25/20 °C alternate temperature conditions. Extracts from pulps and seeds showed a strong inhibition effects on the germination of lettuce seeds, indicating that germination inhibitors are present in pulp and seeds. Since extracts from naked seeds did not show inhibition, inhibitory substances are thought to be present in pulp and seedcoat. Pulp and seeds were extracted with water and methanol and autoclaved at 115 °C, followed by bioassay experiments. Germination inhibitors were found water soluble and heat stable by series of bioassay experiments. Diluted extracts 4 to 8 times still maintained inhibitory effects. Optimum seed harvesting time was from 22 Nov. to 1 Dec., where seed germination was high without additional seed treatments. Total phenolic compounds and ABA contents of pulp and seeds decreased by wet cold seed treatment. Changes in total phenolic compounds and ABA in from October through December were correlated with germination during the seed development. When contents of total phenolic compounds and ABA were high, seeds did not germinate at all, while low contents resulted in good seed germination.

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Wook Oh*, In Hye Cheon and Ki Sun Kim

This research was conducted to investigate the growth and flowering responses of Cyclamen persicum Mill. `Piccolo' to temperature and photosynthetic photon fluxes (PPF), and to obtain fundamental data for production of good quality pot plant. Cyclamen plants with 10 fully unfolded leaves were grown in growth chambers maintained at three day/night temperatures [20/10 (LT), 25/15 (MT), and 30/20 °C (HT)] combined with three PPF [250 (LF), 350 (MF), and 650 (HF) μmol·m-2·s-1] under 14 h-photoperiod. After 3 months, the higher the temperature was, the greater plant width was. It was the greatest under MT/MF and HT/MF. The number of leaves was greater with increasing temperature and PPF. Petiole length, leaf size, and fresh weight were higher with increase in temperature but decrease in PPF. Days to flowering were lower in MT/MF and MT/HF, but higher under LT regardless of PPF. The number of flowers was the highest under MT/MF and MT/HF, and higher under MF in each temperature treatment. Flowering period was longer in LT and MT compared with HT. Most leaves of plants grown under HT curled upward because of boron deficiency induced by higher temperature and lower humidity. Chlorophyll content was higher in medium and low temperature, except LT/HF. The lower side of leaf in low temperature was more reddish compared to that in higher temperature due to some pigments considered as anthocyanin. Photosynthesis was the highest in MT/MF, but low in MT/HF and LT/HF in accordance with the chlorophyll fluorescence (Fv/Fm) which was lower under the same environment. These results indicate that 25/15°C and 350 μmol·m-2·s-1 yielded the best pot cyclamen in this study.

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Hye Jin Kwon, Song Kwon and Ki Sun Kim

This experiment was undertaken to characterize the physiological changes taking place during the petal senescence of Hibiscus syriacus. Five distinctive developmental stages were chronologically suggested. Flower bud dry weight increased almost linearly from Stage I to Stage IV at a rate of ≈15 mg/day. Fresh weight and fresh/dry weight ratio increased much more rapidly between Stage III and Stage IV than during the early stage of development. It showed that petal expansion was partially due to an increased water uptake. The highest osmolality (411 mmol) was found in the fully open flowers. During the subsequent senescence and collapse of the flower, from Stage IV to Stage V, there were a rapid loss of fresh and dry weight and the fall of fresh/dry weight ratio, corresponding to the wilting that characterizes early senescence. A rise in cell sap osmolality coincided with the increase in soluble sugar content and fresh/dry weight ratio, and with the expansion of Hibiscus syriacus petal. Therefore, buds at Stage III, where they are under physiological maturity, might be appropriate to harvest. Hibiscus syriacus flowers showed a small but respiratory peak at Stage IV. The maximum rate of respiration was obtained with fully open flowers (Stage IV), whereas ethylene production remained extremely low until the petals started to open. Ethylene production, ACC synthase, and ACC content increased as the fresh weight of the flowers started to decline. At Stage V, there were a loss of petal fresh weight and a considerable increase in ethylene production (9 nL/g per h). The results of the present study have shown that petal tissue at Stage IV, presenescent stage, was characterized by the increase of soluble sugar and fresh weight, which might be expected to lead to petal expansion and limit turgidity. ABA and the stomata on petal might promote the disorganization.

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Hye Jin Kwon, Song Kwon and Ki Sun Kim

Five distinctive developmental stages were chronologically suggested. Cells at Stage I and II were essentially free of cytoplasmic or vacuolar abnormalities and the cytoplasm contained numerous electron-dense mitochondria with well-developed cristae. At Stage III, there were a localized dilation of mitochondria matrix and a partial-diluted cytoplasm in mesophyll cells. At Stage IV, characterized by high levels of fresh weight and osmolality, most mesophyll cells were seen to be ruptured, resulting in a general mixing of cell contents and diluting cytoplasm. It can be explained as an irreversible senescence phenomena that tonoplast in mesophyll cell was ruptured partly, corresponding to rapid increase in petal cell size and turgidity. Petal turgidity was due to an increase of content in soluble sugar. At Stage V, there was a loss of petal fresh weight. With a loss of turgidity, most mesophyll cells have collapsed completely. There were a notable plasmolysis in vasculature. The activity of protease in petals was found to increase between Stage II and III, and then decreased rapidly at Stage IV, resulting in the decrease of total protein content before senescence. Unexpectedly, there were stomata in hibiscus petals. Ultrastructural disorganization, like as a broken tonoplast, was observed in mesophyll cells at Stage IV. ABA and the stomata on petal might promote the disorganization. The final stages of senescence involved breakdown of cellular organization leading to hydrolysis of previously separated compartments. The cellular disorganization triggered during the flowers are still in the process of opening may be one of the earliest physiological signal that senescence is under way.

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Ki Sun Kim, Arthur C. Cameron and Erik S. Runkle

We performed experiments to determine the photoperiodic response of Ceratostigma plumbaginoides Bunge., or leadwort, which is a low-growing hardy herbaceous perennial native to China with deep gentian-blue flowers. Tip cuttings were rooted in 72-cell trays and grown under a 24-hour photoperiod for 2 weeks and then transplanted into 11.4-cm pots and grown for one more week. Plants were then placed under different primary photoperiods (10, 16, or 24 hours) for 4, 6, or 8 weeks, then transferred to secondary photoperiods (10, 14, 16, or 24 hours) at a constant 20 °C. Pots were also placed under continuous 10, 14, 16, or 24 hours. Nearly all plants flowered under all treatments except under continuous 10- or 24-hour photoperiods, in which no plants flowered. Plants grown under 14 hours flowered earliest (50 days), followed by plants under the 16-hour primary treatment. The 10-hour primary treatment delayed flowering for as long as its duration, whereas the 16-hour primary photoperiod initiated rapid flowering, regardless of duration and subsequent secondary photoperiod. Flowering was also delayed when the primary photoperiod was 24 hours. Collectively, these responses indicate that Ceratostigma is an intermediate-day plant.

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Ki Sun Kim, Art Cameron and Erik S. Runkle

Echinacea purpurea Moench., or purple coneflower, has been classified both as an intermediate-day plant and a short-day/long-day plant by different research groups. We performed experiments to determine at what developmental stage Echinacea`Magnus' became sensitive to inductive photoperiods, and identified photoperiods that induced the most rapid flowering. Seedlings were raised under continuous light in 128-cell plug trays, then were transplanted into 11.4-cm plastic pots. Plants were transferred to 10-hour short days (sd) once seedlings developed 3, 4, 5, 6, 7, or 8 true leaves. After 4 or 6 weeks of sd treatment (primary induction), plants were moved to 16- or 24-hour photoperiods until flowering (secondary induction). Plants were also grown under continuous 10-, 14-, and 24-hour photoperiods to serve as controls. At least 4 leaves were required for flower induction; flowering was delayed and the percentage was low when plants had 3 leaves at the beginning of primary induction. Plants under continuous 14-hour photoperiods had the highest flower percentage (100%) and flowered earliest (87 days). Plants under continuous 10- and 24-hour photoperiods did not flower. Four weeks of sd followed by 16-hour photoperiods induced complete flowering and in an average of 95 days. However, 6 weeks sd was required for 100% flowering when the final photoperiod was 24 hours.

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Su-Jeong Kim*, Chun-Woo Nam, Dong-Lim Yoo, Seung-Yeol Ryu and Ki-Sun Kim

Iris hollandica `Blue Magic' was treated with deionazed water as a control, 3% sucrose (Suc), 3% sucrose plus 0.4 mm silver thiosulphate (Suc+STS), 3% sucrose plus 200 mg·L-1 8-hydroxyquinoline sulphate (Suc+HQS) and 3% sucrose plus 100 mg·L-1 benzyl amino-purine (Suc+BA) for 4hrs and then transferred to tap water. The vase life treated with Suc+BA was extended 4 days longer than that of control. The treatment Suc+STS or Suc+HQS did not improve vase life. The amounts of water uptake and transpiration by all treatments decreased after harvest, but those values were higher in cut iris treated with Suc+BA than in those with control. Cut flowers treated with by Suc+BA markedly improved water balance, comparing with control which was quickly changed to minus value. Anthocyanin content in petals of cut flower treated with Suc+BA was 3.5 fold higher than that of control. The treatment by Suc+BA delayed discoloration in petals and senescence of cut Iris. Peroxidase (POD) activities of all treatments were reached maximum at 4th day after treatment and decreased thereafter. POD activity was highest when the cut iris was treated with Suc+BA. These results show that the use of Suc+BA is most effective treatment for improving the vase life and quality of cut Iris flowers.

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Wook Oh, In Hye Cheon, Ki Sun Kim and Erik S. Runkle

This study was carried out to examine the effect of photosynthetic daily light integral (DLI) on the growth and flowering of cyclamen (Cyclamen persicum Mill. ‘Metis Scarlet Red’). Plants with six fully unfolded leaves were grown at 24/16 °C (12 h/12 h) under an 8- or 16-h photoperiod at a photosynthetic photon flux of 50, 100, 150, 200, and 300 μmol·m−2·s−1, which provided seven DLIs: 1.4, 2.9, 4.3, 5.8, 8.6, 11.5, and 17.3 mol·m−2·d−1. Days to first flower decreased from 133 to 75 as DLI increased from 1.4 to 17.3 mol·m−2·d−1, although the acceleration of flowering was less pronounced when the DLI was greater than 5.8 mol·m−2·d−1. Mean leaf and flower number increased from 8.7 to 28.0 and from 0 to 14.7, respectively, as DLI increased from 1.4 to 11.5 mol·m−2·d−1, but there was no further increase under a DLI of 17.3 mol·m−2·d−1. Total dry weight and net photosynthetic rate showed a similar trend as leaf and flower number. We conclude that supplemental lighting can accelerate greenhouse production of potted cyclamen under a low ambient DLI (i.e., less than 12 mol·m−2·d−1).

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Su-Jeong Kim, Chun-Woo Nam, Dong-Lim Yoo, Jong-Taek Suh, Myoung-Rae Cho and Ki-Sun Kim

This study was conducted to overcome the problems occurring in soil cultured Sandersonia, such as secondary tuber formation, tuber russeting, browning and surface cracking. For the tuber production, soilless culture medium compositions (peatmoss, perlite, cocopeat) and harvesting times [4, 6, 8, 10, and 12 weeks after flowering time (WAF)] were compared. The mother tubers were planted and grown in a plastic box (40 × 60 × 23 cm) under a PE film house with shading in summer season. The tuber number and weight were higher in peatmoss-based media of peatmoss, 1 peatmoss: 1 perlite, and 2 peatmoss: 1 perlite (by volume) than in the other media. Particularly, the plant height and the numbers of leaf and flower were also higher. The contents of total nitrogen and phosphorus in leaves were lower when the tubers were grown in perlite. Leaf area index per plant reached the maximum at 8 WAF and decreased thereafter. The optimal harvesting time for tuber production was 8-10 WAF.