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J.T. Lehmann and M.L. Albrecht

Armeria maritima was studied to provide guidelines for flowering potted plant production. Seed and vegetatively propagated plants were exposed to 9-hr, 13-hr, or 17-hr photoperiods. Flowering was enhanced under the 13-hr and 17-hr photoperiods. Peduncle and leaf length were shorter, and plants were more compact under short days (SD, 9-hr photoperiod) than under long days (LD). When grown under SDs then moved at monthly intervals to LDs, the degree to which the compact growth habit (CH) was expressed was dependent upon the length of exposure to SDs. Plants with the CH produced fewer inflorescences than full growth habit plants.

Plants held in cold storage (4C) flowered more profusely under LDs, but had a delay in flowering. There was more uniform flowering for plants held in cold storage than those held in a cool greenhouse (7C night temperature).

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John M. Dole and Harold F. Wilkins

Easter lily bulbs (Lilium longiflorum `Nellie White') were given 6 weeks of cold, placed in the greenhouse and subsequently divided into groups based on emergence date after placement in the greenhouse: 0-6, 7-13, 14-20 and 21-27 days. At emergence bulbs received 0, 1, 2 or 3 weeks of long days (LD). Late-emerging plants had fewer days to visible bud and anthesis from emergence than early-emerging plants; consequently, late-emerging plants flowered within 3-10 days of early emerging plants despite 14-21 days difference in emergence time. Late emerging plants were tallest and middle emerging plants had the highest leaf number. Increasing LD tended to decrease numbers of days from emergence to visible bud and anthesis and increase plant height. LD did not effect leaf or flower number. Interactions between LD and emergence date will be discussed. Experiment was repeated for three consecutive years.

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Kenneth R. Schroeder and Dennis P. Stimart

Gibberellic acid (GA3) and photoperiod were used in combination in an effort to reduce generation time of Antirrhinum majus L. Four commercial inbred lines of A. majus were started from seed and grown in a glasshouse in winter 1993-94. GA3 was applied as a foliar spray every 2 weeks at 0, 144, 289, 577, or 1155 μm starting 5 weeks after seeds were sown. Supplemental lighting (60 μmol·m–2·s–1) from 0600 to 2000 hr and night interruption from 2300 to 0300 hr was used throughout the experiment. Data were collected weekly on plant height and leaf count from the start of GA3 treatments through anthesis. Time to flowering was determined as days from seed sowing to anthesis. GA3 treatment of A. majus under a long-day photoperiod increased time to flowering, plant height and leaf count. It would appear that long-days may have overridden the floral induction effects of GA3.

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Richard A. Criley

The flowers of pakalana are initiated under long days (LD) at 18C or above. At 21 and 24C, inflorescence initiation occurs after 3 weeks of LD, and the clusters grow to 6 mm in another 2 weeks, but at 18C, about 12 weeks are required to achieve the 6-mm length. This length is critical, as a shorter stage often fails to develop further. From a length of 6 mm, clusters develop to anthesis in 3 to 4 weeks at 24C, 4 to 5 weeks at 21C, and 6 to 7 weeks at 18C. This work is important to the production of pakalana flowers for Hawaii's winter lei flower trade.

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Fumiomi Takeda, D. Michael Glenn, and Gary W. Stutte

-plugged transplants, grown in a greenhouse at high plant density, under long days, and at temperatures greater than 21 °C during day and night until late August flowered in the fall. It is likely that immature leaves in the bud or tissues that have just emerged from

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John M. Dole

`Nellie White' Easter lily bulbs (Lilium longiflorum Thunb.) were given 6 weeks of 5.5C, placed in the greenhouse, and divided into groups based on number of days to emergence: 0 to 6, 7 to 13, 14 to 20, or 21 to 27 days. At emergence, the shoots received 0, 1, 2, or 3 weeks of long days (LDs). The experiment was repeated for 3 consecutive years. Late-emerging plants had fewer days from emergence to visible bud and anthesis than early-emerging plants. Consequently, late-emerging plants flowered within 3 to 11 days of early emerging plants despite 16 to 22 days difference in emergence time. Late-emerging plants were tallest, while plants emerging in the second week had the most leaves. Flower count was not influenced by emergence date in Year 1. In Year 2, flower count decreased curvilinearly with later emergence. In Year 3, flower count was highest in plants emerging in the second week and lowest in the last week. Increasing LDs decreased the number of days from emergence to visible bud and anthesis but increased plant height. LDs did not affect leaf count in any year or flower count in Years 1 and 2. In Year 3, flower count increased with increasing weeks of LDs. LD × emergence date interactions existed, but varied from year to year.

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Milton E. Tignor, Frederick S. Davies, Wayne B. Sherman, and John M. Davis

Poncirus trifoliata (L.) Raf. seeds were germinated in perlite under intermittent mist at about 25 °C and natural daylight in a greenhouse. Two-week-old seedlings were then transferred into a growth chamber at 25 °C and 16-hour daylength for 1 week. Tissue samples were collected at 0, 6, 24, 168, and 504 hours after temperature equilibration at 10 °C. Freezing tolerance at –6.7 °C, as determined by electrolyte leakage, and stem (leaves attached) water potential (ψx), measured using a pressure chamber, was recorded for a subset of seedlings for each time interval. Red coloration (apparently anthocyanin) developed at the petiole leaflet junction and buds after 48 hours at 10 °C and gradually occurred throughout the leaves during further exposure. Complementary DNA clones for phenylalanine ammonia lyase (PAL), 4-coumarate: coA ligase (4CL), and chalcone synthase (CHS) were used to probe RNA isolated from the leaves. No increase in steady-state messenger RNA level was detected. Increases in freeze hardiness occurred within 6 hours in the leaves, and continued for up to 1 week. Water potential initially decreased from –0.6 to –2.0 MPa after 6 hours, then returned to –0.6 MPa after 1 week. Thus, Poncirus trifoliata seedlings freeze-acclimate significantly after only 6 hours at 10 °C.

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Peter R. Hicklenton, Suzie M. Newman, and Lindsay J. Davies

The effects of night temperature (NT) and photosynthetic photon flux (PPF) on time to flower and flower yield in `Bristol Fairy' and `Bridal Veil' Gypsophila paniculata L. (perennial baby's breath) were studied in controlled environments. Plants were grown with nights at 8, 12, 16, and 20C and 450 or 710 μmol·s-1·m-2 photosynthetic photon flux (PPF). Days were at 20C. In both cultivars, the times from the start of treatments to visible bud and from visible bud to anthesis were delayed at the lower PPF and at an NT <20C. The delays in `Bristol Fairy' were greater than those in `Bridal Veil'. Failure of `Bristol Fairy' plants to reach anthesis was common at SC NT and either 450 or 710 μmol·s-1·m-2 PPF; whereas in `Bridal Veil', nearly all plants flowered, regardless of environmental conditions. Flower yield (measured as fresh weight of inflorescences) decreased with NT in `Bristol Fairy' but was highest at 8 or 12C in `Bridal Veil'. In a second experiment using the same cultivars, the effect of curtailing long-day (LD) conditions at various stages on stem elongation and flower yield was investigated. `Bristol Fairy' required more LD cycles (>56) than `Bridal Veil' for maximum stem elongation and flower yield. Terminating LD conditions before the start of inflorescence expansion resulted in lower yields and shorter plants in both cultivars.

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John M. Dole and Harold F. Wilkins

Easter lily (Lilium longiflorum Thunb. `Nellie White') bulbs were exposed to 1, 2, 3, 4, 5, or 6 weeks of cold before shoot emergence; 0, 1, 2, 3, 4, 5, or 6 weeks of long days (LD) upon shoot emergence; or a combination of cold followed by LD: 1/5 (weeks cold/weeks LD), 2/4,3/3,4/2, or 5/1. Experiments were repeated for three consecutive years. LD did not substitute equally for cold; at least 3 weeks of cold were required before LD treatments resulted in anthesis. Depending on the year, 100% of the plants flowered when treated with 3 to 6 weeks of cold alone or in combination with LD. Days to first flower anthesis from planting increased with decreasing weeks of cold in years 1 and 3, but was similar for all treatments in year 2. Decreasing weeks of cold in combination with LD, however, decreased days to anthesis in years 1 and 2, but had no effect in year 3. Regardless of LD, days from emergence to visible bud increased with decreasing weeks of cold in all years, and days to emergence from placement in the greenhouse increased with decreasing cold in years 1 and 3, but not in year 2. Increasing weeks of cold, regardless of LD, decreased leaf count, but had no effect on plant height. Flower count was unaffected by cold when combined with LD, but was significantly reduced by increasing weeks of cold.

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Daedre S. Craig and Erik S. Runkle

subsequently grown under non-inductive long days [natural daylength extended from 0600 to 2200 hr by high-pressure sodium (HPS) lamps] in a research greenhouse at 20 °C until transfer to the NI treatments. African marigold and dahlia were transferred to NI