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Mark Roh*

The effect of bulb storage and forcing temperatures on growth, flowering, and inflorescence development and the death of inflorescence (blast) of Lachenalia aloides Engl., `Pearsonii' was investigated. Following development of about 5 florets, bulbs were stored at 10, 12.5, 15, 20, and 25 °C for 15, 30, or 45 days and forced in greenhouses at 17/15 °C and 21/19 °C. Flowering was accelerated, and leaf length and floret number were reduced, when bulbs were stored at 10, 12.5, or 15 °C for 45 days compared to storing at 20 or 25 °C. Flowering was further accelerated by forcing at 17/15 °C compared to 21/19 °C. When bulbs were stored at 10, 15, 20, or 25 °C for 4 weeks and grown in greenhouses at 17/15 °C, 21/19 °C, 25/23 °C, and 29/27 °C, the incidence of inflorescence blast was increased when bulbs were stored at 10 and 15 °C and forced at 25/23 °C compared to low temperatures. Bulbs were forced in greenhouses maintained at 18/16 °C, 22/20 °C, or 26/24 °C for 12 weeks. During forcing, plants were subjected to constant or alternating forcing temperatures at 4-week intervals. Inflorescence blast occurred when the temperature was 26/24°C during the first 4 weeks after potting. Storing Lachenalia bulbs at 10&#176 to 15 °C before potting then forcing at 17/15 °C accelerated flowering and produced quality plants with short leaves and floral stems. Inflorescence development during bulb 10 °C treatment and inflorescence blast that occurred after only 3 days of 35 °C was demonstrated using scanning electron microscopy and magnetic resonance imaging techniques.

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Brooks Whitton, Will Healy and Mark Roh

Stock plants of Aeschynanthus `Koral' were grown with irradiances of 120 or 240 μmol·s-1·m-2 at 18/17, 24/17, or 30/17C (day/night) under 12-hour thermo- and photoperiods. Tip cuttings from stock plants grown at 18/17C flowered earlier than those from stock plants grown at 24/17 or 30/17C when cuttings were forced in a glasshouse under natural days (23/18 C). No cuttings from stock plants grown at 30/17C reached the visible bud stage after 86 days, while 93% of the cuttings forced at 18/17C did reach the visible bud stage. A. `Koral' plants were grown at 18, 24, or 30C in a factorial combination of temperatures at 12-hour thermo- and photoperiods (100 μmol·s-1·m-2). After 8 weeks, only plants grown at 18/18C had visible buds. After 18 weeks, plants grown at 24/24 or 24/18C had visible buds after having unfolded =2.5 times as many leaves as plants grown at 18/18C. Rapid flowering of A. `Koral' is promoted by constant 18C under a 12-hour photoperiod.

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Ignacio Espinosa, Will Healy and Mark Roh

Shoot emergence of cold-treated Liatris spicata Willd. corms was inhibited by SC soil, delayed at 10 or 15C (7 and 5 days, respectively), and promoted at 20, 25, or 30C. Within 15 days after planting, soil at 20C promoted the highest percentage of shoot emergence (81%). Plants were grown during the first 35 days after emergence under a combination of temperature and long or short days. Flowering shoot length was increased by either short days (8 hours; SD) at 13 or 15C or a 4-hour incandescent night interruption (NI) at 18C. When planted in May, a NI at 15 or 18C decreased the time to harvest by up to 14 days, whereas in November increasing the temperature to 18C, regardless of photoperiod, decreased the days to harvest by 16 days. Plants grown during the first 35 days after emergence under natural days at 15C then placed at 13, 15, or 18C under NI until harvest did not respond to the increasing temperature. Temperature and photoperiod influence Liatris development primarily during the first 35 days of development.

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Mark S. Roh, Robert Griesbach and Roger Lawson

Flowering responses of two Anigozanthos hybrids were investigated. Flowering of 20-week old `Regal Claw' and A. manglesii x A. flavidus either from the main fan or the lateral fans was accelerated when plants received a night temp of 13 C, regardless of the photoperiod treatments. Temperature was the major factor controlling flowering of Anigo- zanthos hybrids. Flowering was accelerated from the lateral fans by treating plants at 15.5 or 18 C and a long day (LD) photoperiod. There were fewer than 2.5 branches in the stem at 18 C compared to more than 4.0 branches at 13 C. A night temp of 13 C was optimum for early flowering and for increased quality of cut flowers. At an inductive night temp of 13 C, Anigozanthos hybrids are day neutral while at 15.5 or 18 C they are quantitative LD plants.

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Jong Suk Lee and Mark S. Roh

The effect of long-term storage of lily bulbs at -2 °C and of high temperatures on plant height and floral abnormalities was investigated with Oriental hybrid lilies in 1997-2000. `Acapulco' and `Simplon' bulbs were stored frozen at -2 °C and forced in regular greenhouses with varying temperatures between 12 to 30 °C, depending on the season, and also air-conditioned greenhouses where temperatures were maintained year-round at 15.5 to 16 °C or 18 to 18.5 °C. Floral development was observed under a scanning electron microscope after -2 °C treatment. At flowering, stem length with dried and green leaves, number of leaves, and number of normal and abnormal flowers were counted. Although frozen-in storage duration affected plant height, flowering, and the number of abnormal flowers, high temperatures during summer significantly affected the speed of flowering, plant height, and the number of abnormal flowers. High temperature damage can be prevented by growing bulbs at low temperatures immediately after planting the frozen-in stored bulbs. Bulbs can be stored for 12 months to produce quality cut Oriental hybrid lily flowers.

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Sandra M. Reed, Younghee Joung and Mark Roh

The genus Clethra contains many ornamental species, of which the most adaptable and cold hardy is C. alnifolia L. The objective of this study was to obtain hybrids between C. alnifolia and three other ornamental Clethra species, C. acuminata Michx., C. fargesii Franch., and C. pringlei S. Wats. Viable plants were obtained from reciprocal crosses between C. alnifolia and C. fargesii, and from crosses between C. alnifolia and the other two species when C. alnifolia was used as the maternal parent. Randomly amplified polymorphic DNA (RAPD) markers were used to verify hybridity and to compare hybrids to their parents. In all cases, the hybrids had more RAPD markers in common with C. alnifolia than with their other parent. Close clustering by neighbor-joining analysis of RAPD markers and the morphological resemblance of C. alnifolia × C. acuminata and C. fargesii × C. alnifolia plants to their paternal parent indicated that these plants were of hybrid origin. The C. alnifolia × C. pringlei plants resembled C. alnifolia in many respects, but they stayed green much later in the year than did C. alnifolia with leaves remaining on the plants throughout the winter. These foliage characteristics were presumed to reflect the contribution of the evergreen C. pringlei, and thus were regarded as evidence of hybridity.

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Jong Suk Lee and Mark S. Roh

The effect of long-term storage of lily bulbs at -2 °C (frozen storage) and of high forcing temperatures on plant height and floral abnormalities was investigated with Oriental hybrid lilies from 1998 to 2000. `Acapulco' and `Simplon' bulbs were stored frozen at -2 °C for various lengths of time and were forced in fan- and pad-cooled greenhouses with temperatures ranging from 11 to 31 °C, depending on the season. The same cultivars were also forced in greenhouses and maintained year-round under refrigerated air conditioning with day/night temperatures of 16/15.5 °C or 18.5/18 °C. Floral development immediately after storage and at different intervals thereafter was observed by scanning electron microscopy (SEM). The prolonged frozen storage reduced the number of flowers. High greenhouse forcing temperatures during summer significantly accelerated flowering, resulted in short plants, and increased the number of abnormal flowers. Forcing at a low temperature (15.5 °C) after planting the frozen stored bulbs resulted in longer cut stems than those forced at 25 °C for 30 days after potting. Bulbs can be stored up to 9 months and still produce high-quality Oriental hybrid lilies.

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Brooks Whitton, Will Healy and Mark Roh

Aeschynanthus `Koral' plants were grown in photoperiods of 8 to 14 hours (8 hours of natural daylight plus 0 to 6 hours of incandescent light of 3 μmol·m-2s-1) beginning January, March, or June. The number of weeks to anthesis and the number of leaves on flowering shoots were not affected by photoperiod but differed based on when treatments commenced. Flowering was inhibited, regardless of photoperiod, when the daily temperature differential was larger than 10C. To study the interaction of photoperiod and temperature, Aeschynanthus `Koral' plants were grown under photoperiods of 12 or 24 hours (daylight fluorescent lamps at 4.3 mol·m-2·day-1) at 18 or 24C. After 8 weeks, plants grown at 18C had fewer nodes before the first flower bud than plants grown at 24C. Aeschynanthus `Koral' was day-neutral at 18C, but responded as a long-day plant at 24C.

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Mark Roh, Roger Lawson, Jong Suk Lee, Jeung Keun Suh, Richard A. Criley and Pimchai Apavatjrut

Sixteen accessions of Curcuma germplasm and several selected accessions of Curcuma were evaluated for use as potted plants or as cut flowers. Curcuma alismatifolia Gagnep. and C. thorelii Gagnep. `Chiang Mai Snow' met standards for cut flower and pot plant use, respectively. Furthermore, C. parviflora Will. `White Angel' proved to be a good selection for potted plant production. Optimum storage temperatures of rhizomes were studied in relation to greenhouse forcing and carbohydrate changes. It is recommended to store rhizomes at 25 to 30 °C after harvest for 2 to 3 months to break dormancy. Plants of C. parviflora `White Angel' flowered in 50 to 89 days and C. `CMU Pride' flowered in 104 days after potting, and were acceptable as potted plants. Plants of C. alismatifolia flowered 96 to 133 days after potting with floral stem length suitable for use as a cut flower. A high level of boron or manganese may cause the burn at the margin of the leaves (marginal leaf burn) observed on old leaves of `CMU Pride' at flowering. The level of ethanol-soluble fructose, glucose, and sucrose in elongated rhizomes with emerged short shoots of Curcuma was higher than the level in rhizomes and increased as storage temperatures increased. Accelerated leaf emergence may be associated with the increase in the glucose and fructose content. Based on the similar morphological characters between C. thorelli `Chiang Mai Snow' and C. parviflora `White Angel', identification of Curcuma accessions is required in future studies.