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Barrett C. Wilson, Jeff L. Sibley, and James E. Altland

A study evaluating the effects of varying levels of chilling on foliar budbreak of linden (Tilia spp.) culivars was initiated in 1999 in Auburn, Ala. [lat. 32°36'N, long. 85°29'W, elevation 709 ft (216m), USDA Hardiness Zone 8a]. Littleleaf linden (T. cordata) `Greenspire' and `Fairview' required the most chilling to produce measurable budbreak and exhibited the lowest budbreak percentages. Silver linden (T. tomentosa) `Sterling' and american linden (T. americana) `Redmond' needed the fewest hours of chilling to produce budbreak and exhibited the highest budbreak percentages. `Sterling' was the top performer in foliar budbreak percentage and in subsequent growth. Although `Redmond' attained high budbreak numbers, its overall growth during the following growing season was inferior to that of `Sterling', `Greenspire' and `Fairview'. This information can contribute to the development of regional planting recommendations, which can aid in the selection of lindens suitable for the area in which they will be grown. Calculated r2 values indicated the models used provided a good fit to the data for all cultivars.

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Experiments with' White Christmas' and `Carolyn Wharton' caladiums (Caladium × hortulanum Birdsey), croton (Codiaeum variegatum), brassaia (Brassaia actinophylla Endl.), `Annette Hegg Dark Red' poinsettia (Euphorbia pulcherrima Wind.), and `Super Elfin Red' and `Show Stopper' impatiens [Impatiens wallerana (L.) Hook.f.] determined effectiveness of paclobutrazol in solid spike form as compared to media drench applications for height control. Paclobutrazol drenches and spikes were effective for all crops tested, with a similar concentration response for all, except that drenches had greater efficacy than spikes on caladium. A reduced effect was observed when spikes were placed on the medium surface of `Super Elfin Red' impatiens, while placement in the middle of the pot or around the side was equally effective. These results indicate that the spike formulation of paclobutrazol has potential to provide adequate size control for floriculture crops with the possible exception of rapidly developing crops, such as caladiums. Chemical name used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-) penten-3-ol (paclobutrazol).

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Richard Kent Schoellhorn, James E. Barrett, and Terril A. Nell

Treatments were cultivar, uniconazole concentrations (0, 2, 4, or 8ppm), and time between dip and placement under mist (0, 10, or 60 minutes). Unrooted chrysanthemum cuttings of cultivars `Tara' and `Boaldi' were dipped in uniconazole solutions for 10 seconds. Data were taken 16 days after treatment. A quadratic relationship was found for the interaction between concentration and cultivar. `Tara': (y = 6.7277-1.532(x) + 0.119409(x2)) and `Boaldi': (y= 6.4676-0.884(x)+0.060020(x 2). Time had no significant interaction with either cultivar or uniconazole concentration.

In a second study, with uniconazole concentrations and storage time (10 minutes or 12 hours), main effects and the cultivar concentration interaction were significant.

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Paclobutrazol drench treatments were evaluated for efficacy on Caladium ×hortulanum (Birdsey) cultivars Aaron, White Christmas, and Carolyn Wharton. Drenches at 2.0 mg/pot did not reduce height of `Aaron' and `White Christmas' plants when applied 1 week after planting, but 2.0 mg applied at 3 weeks after planting did result in shorter plants. The difference for time of application may be due to the amount of roots present to take up paclobutrazol when applied. In two factorial experiments, there were no interactions between cultivar and time of application or amount of chemical. Paclobutrazol at 0.5 mg/pot resulted in plants that were shorter than the controls. Higher amounts of paclobutrazol provided additional reductions in height, but there was variation between the experiments for degree of effect with amounts >1 mg. Generally, commercially acceptable height control was provided by paclobutrazol drench treatments at 0.5 and 1.0 mg/pot applied 3 weeks after planting. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-pentan-3-ol (paclobutrazol).

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Richard K. Schoellhorn, James E. Barrett, and Terril A. Nell

Effects of photosynthetic photon flux (PPF) and temperature on quantitative axillary budbreak and elongation of pinched chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] plants were studied in three experiments. In Expt. 1, 12 commercial cultivars were compared under fall and spring environmental conditions. Spring increases in lateral shoot counts were attributable to increased PPF and air temperature. Cultivars varied from 0 to 12 lateral branches per pinched plant and by as much as 60% between seasons. There was a linear relationship between lateral branches >5 cm at 3 weeks after pinching and final branch count (y = 0.407 + 0.914(x), r 2 = 0.92). In Expt. 2, air was at 20 or 25C and the root zone was maintained at 5, 0, or –5C relative to air temperature. With air at 20C, lateral branch counts (3 weeks after pinch) declined by ≤50% with the medium at 15C relative to 25C. At 25C, lateral branch count was lower with medium at 30C than at 20C. Cultivars differed in their response to the treatments. Experiment 3 compared the interactions among temperature, PPF, and cultivar on lateral branch count. Depending on cultivar, the count increased the higher the PPF between 400 and 1400 μmol·m–2·s–1. Air temperature had no effect on lateral branch count. PPF had a stronger effect on lateral branch count than air temperature, and cultivars differed in their response.

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William M. Womack, James E. Barrett, and Terril A. Nell

`Prize' and `Gloria' azaleas were budded at 29C day/24C night without growth regulators. Dormant-budded plants were held at 2, 7, 13, or 18C for 0, 0.5, 1, 2, 4, 6, 8, or 10 weeks and then forced in walk-in growth chambers (29C day/24C night). A model was developed to describe the effect of cooling temperature and duration on days to marketability (eight open flowers) and percent of buds showing color. Holding at temperatures below 7C, increases days to marketability up to 7 days. Extended cooling (beyond 6 weeks) at temperatures <7C increases percent of buds showing color. Extended holding at temperatures >7C decreases buds in color due to development of bypass shoots during cooling and increased bud abortion. Plants not receiving a cool-treatment or cooled for <2 weeks do not flower uniformly. Furthermore, the percentage of plants reaching marketability dramatically decreases for plants held longer than 6 weeks at temperatures >7C. Both cultivars show similar trends, but `Gloria' has greater variability.

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Lori A. Black, Terril A. Nell, and James E. Barrett

Dormant-budded `Gloria' azaleas (Rhododendron sp.) at various maturity levels (one, eight, or 32 individual open flowers) were moved from the greenhouse to postproduction rooms. Postproduction rooms were maintained at 21 ± 1C, relative humidity 50% ± 5%, and 12 hours of daily irradiance at 12 μmol·s–1·m–2 from cool-white fluorescent lamps to simulate home conditions. Using predetermined categories, the number of tight, showing-color, candle, and open-flower inflorescences were recorded. After 2 weeks postproduction, plants chosen at the start of postproduction with eight or 32 individual open flowers had the best flowering uniformity and flower color. In a second experiment, azaleas with one, eight, or 32 individual open flowers were placed into simulated transport for 4 days at 16 ± 1C. Plants with one individual open flower had greatest longevity, but those with eight open flowers had the best overall postproduction performance. In a final experiment, azaleas at similar maturity levels were placed in simulated transport at 5, 16, or 27C for 2, 4, or 6 days. After 2 weeks postprodudion, there was no difference due to simulated-transport temperature or duration on flowering performance or flower color. Longevity was good for plants held 2, 4, or 6 days at 5C and for plants held for 2 days at 16 or 27C.

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William M. Womack, Terril A. Nell, and James E. Barrett

Dormant-budded `Prize' azaleas (Rhododendron sp.) were held at 2C, 7C, 13C, or 18C for 1, 2, 4, 6, 8, or 10 weeks then forced in walk-in growth chambers (29C day/24C night). Holding at 2C delayed flowering by 5-7 days over 7C and 13C. Plants held at 2C, 7C, or 13C for at least 4 weeks had approximately 50% buds showing color at marketability (8 open flowers). Plants held at 18C never exceeded 35% buds showing color at marketability. Increase in buds showing color was not apparent for plants were held at 7C, 13C, or 18C for more than 6 weeks; however, holding at 2C resulted in increasing percentages of buds showing color for holding periods longer than 6 weeks. Plants chilled at 13C and 18C showed significant increases in bud abortion after 8 or 10 weeks of cooling with most plants never reaching marketability (8 open flowers). These plants also had an increased proliferation of bypass shoots during cooling and forcing over other treatments.

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Thea M Edwards, Terril A. Nell, and James E. Barrett

Increased rates of senescence and ethylene related damage of potted flowering plants have been observed in supermarket produce areas where flowers and climacteric produce are displayed together. Ethylene levels in produce areas were found to average 20 ppb. An open system of clear glass chambers with fiberglass lids was designed to simulate retail supermarket conditions. The chambers were kept in postharvest rooms where light level and temperature could be controlled. In a 3 by 3 by 3 Box-Behnken design, Sunblaze `Candy' miniature potted roses were exposed to three levels of ethylene, 20, 40, and 80 ppb, for 1, 2, and 4 days. The three light levels used were: 0, 7, and 14 μmol·m-2·s-1. Ethylene damage was based on leaf and bud drop and decreased flower longevity.

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Lori A. Black, Terril A. Nell, and James E. Barrett