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Mauricio José Sarmiento and Jeff S. Kuehny

Gingers are tropical perennials from the Zingiberaceae family with attractive long-lived flowers that can be grown as potted plants in subtropical and temperate zones under protected conditions. Development of production practices for this new flowering pot crop is essential for optimum plant growth. The effect of photoperiod on growth and flowering was evaluated on Curcuma gracillima, C. cordata, C. alismatifolia, C. petiolata `Emperor', Curcuma `Chang Mai dwarf', Siphonichilus decora, and S. kirkii. Plants were grown under daylengths of 8, 12, 16, and 20 h. Plant height, number of new leaves, number of shoots, and leaf area were larger for plants growing under an extended daylength (16- and 20-h photo-period) than for plants under 8 and 12 h. Plants grown under an 8-h daylength approached dormancy sooner than those growing under 12, 16, or 20 h of light, and no flowering occurred.

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Michael J. Roll and Steven E. Newman

Rooting of cuttings from three cultivars of Euphorbia pulcherrima Willd. was evaluated after regulating the photoperiod during the stock plant stage. One group of stock plants was exposed to a night break (4 hours) and another group was exposed to natural daylength during September. Cuttings harvested in late September from `Freedom Red' and `Monet' stock plants grown under the 4-hour night break rooted more rapidly and had greater root mass than `Freedom Red' and `Monet' grown under natural daylength, whereas rooting of cuttings from `V-17 Angelika Marble' was not influenced by the photoperiods tested. Using a night break to prevent flower initiation of stock plants produced a higher-quality cutting when propagation took place after the critical daylength for flowering had passed.

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A.M. Wagner and J.T. Fisher

Dormancy level is an important factor in rooting stem cuttings of conifers. Eldarica pine, a Mediterranean species, is a multiple flushing pine that does not appear to express endodormancy in southern New Mexico. Photoperiod manipulations can alter the dormancy level of some conifer species; however, effects on eldarica pine are unknown. Half-sib stock plants were randomly assigned to one of three photoperiods: natural daylength (>12 hours, control), long-term (7 months) exposure to 9-hour daylength (LTSD), and 2-week exposure to 9-hour daylength (STSD). Of the cuttings from LTSD stock plants, 78% rooted; however, only 67% of the cuttings from the other two treatments rooted. Differences in rooting also were related to shoot type of the cuttings. Cuttings from expanded short shoots without a bud rooted more frequently than cuttings from branch shoots with or without a bud present. Applications of these results are discussed.

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Dan Drost, Taunya Ernst, and Brent Black

decreased from mid-October to late December as seasonal daylengths decreased ( Table 1 ). Snow days, light levels, and average high and low temperatures for the W2011 and W2012 were more similar. During W2011 trial (19 Jan. to 20 Mar.), there were 15 d with

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Ren-Huang Wang, Yu-Mei Hsu, Duane P. Bartholomew, Subbiyan Maruthasalam, and Chin-Ho Lin

induction in subtropical latitudes mainly occurs in cooler winter months, and in N latitudes typically occurs from late November through at least February, when temperatures are cooler and winter daylengths are shorter ( Bartholomew et al., 2003 ). Van

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Richard A. Criley and William S. Sakai

Seasonal flowering behavior of Heliconia wagneriana Petersen was found to be caused by short daylengths (SD) using artificial short days (8 to 9 hours) and long days as daylength extension or night break lighting with incandescent lamps. The natural time for flower initiation was estimated to be mid- to late October (11 hours 40 minutes to 11 hours 20 minutes) in Hawaii, and 120 to 150 days were required from the onset of inductive SD to inflorescence emergence. The results may be used to manipulate flower availability for flower markets.

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Rebecca L. Darnell

Containerized `Climax' and `Beckyblue' rabbiteye blueberry plants (Vaccinium ashei Reade) were exposed to 5 weeks of natural daylengths (i.e. gradually decreasing daylengths from 12 to 11 hr) or shortened daylengths (i.e. gradually decreasing daylengths from 10 to 8 hr) starting October 1. `Beckyblue' initiated twice as many flower buds under short days compared to longer days. The following spring, `Beckyblue' plants exposed to shortened photoperiods the previous fall had a greater percentage of floral budbreak (based on the number of flower buds formed within each treatment) and a shorter, more concentrated bloom period than did plants exposed to longer photoperiods the previous fall. Fresh weight per berry increased following the short fall photoperiod treatment, despite the fact that fruit number was higher. `Climax' did not respond to the photoperiod treatments in any way. Leaf carbon assimilation rates of both cultivars increased under short days, but there was no detectable effect of photoperiod on current carbon partitioning in either cultivar, suggesting that flower bud initiation is not limited by current source leaf assimilate supply under these conditions.

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Fumiko Kohyama, Catherine Whitman, and Erik S. Runkle

, C. Heins, R.D. Cameron, A.C. Carlson, W.H. 1998 Lamp type and irradiance level for daylength extensions influence flowering of Campanula carpatica ‘Blue Clips’, Coreopsis grandiflora ‘Early Sunrise’, and Coreopsis verticillata ‘Moonbeam’ J

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Leah Chaudoir and A.E. Einert

Rhizomes of Iris germanica L. `Pretty Please' were stored either dry at 21°C or potted at 10°C for 0, A, 9, 11, 13, 15, or 17 weeks. After storage, dry rhizomes were potted and placed in a forcing greenhouse. Potted rhizomes were removed from the 10°C cooler and placed in the same greenhouse. Both were forced under longdays(16 hr). A control group with no rhizome storage received natural daylength. Plants flowered without rhizome storage if grown under longdays. Four weeks of rhizome storage (cool or warm) significantly hastened flowering of potted irises over those receiving no rhizome storage, as well as producing the highest percentage of flowering plants. Potted rhizomes chilled for 17 weeks had the shortest forcing period, but only 50% of plants flowered. Plants receiving natural daylength did not flower. Greenhouse forced plants did not produce more than three flowers per scape. Foliage height at flowering decreased significantly after 15 weeks of cool rhizome storage.

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Setapong Lekawatana and Richard A. Criley

Inflorescence abortion in heliconia contributes to an economic loss to growers. In an effort to determine the cause, we manipulated temperature, daylength and light intensity. Plants of Heliconia stricta cv. Dwarf Jamaican were grown in 4 day/night temperature regimes (15/10, 20/15, 25/20 and 30/25°C) under 14 hr daylength. In a separate experiment, plants were grown in full sun, 60% and 80% shade. Both experiments had been conducted after inflorescences were induced (4 weeks of short days). Apical meristems were dissected weekly to follow inflorescence development. Leaf abscisic acid level was detected by an indirect ELISA. Significantly more inflorescences were aborted in plants grown under high temperature regimes than in plants grown under low temperature regimes and under different light intensity. Abscisic acid concentration increased in heliconia leaves under regimes that induced inflorescence abortion. The results could provide a mean to improve heliconia inflorescence production.