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Richard K. Schoellhorn and A.J. Compton

Plants, which move directly from the wild into commercial propagation, without the benefit of extensive breeding and selection, often pose production-oriented problems for growers. Vigorous plant growth, especially during the propagation phase of production is a common problem. The purpose of this work was to determine the degree of efficacy offered by chemical control of stem elongation in propagation of Porter Weed [Stachytarpheta mutabilis, S. mutabilis var. violacea, and S. urticifolia]. Tip cuttings of three Stachytarpheta species were given a 10-s dip in the following treatment solutions: daminozide (2500 and 5000 mg·L-1), daminozide and chlormequat chloride tank mix (2000 mg·L-1 ea.), paclobutrazol (2 and 4 mg·L-1), uniconazole (2 and 4 mg·L-1), distilled water, and undipped controls. Cuttings were then treated with a 0.1% IBA rooting powder and placed under intermittent mist on the propagation bench. After 2 weeks in propagation, cuttings were harvested and shoot elongation, root development, and dry weights were evaluated. The interaction of chemical and species was significant for stem elongation and dry weight; chemical effect on root development was also significant. Paclobutrazol and uniconazole offered greater control of stem elongation than daminozide, daminozide-chlormequat chloride, water, or control treatments.

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Richard K. Schoellhorn and A.J. Compton

Floricultural crops without the benefits of extensive breeding or selection often pose problems for commercial cutting and finished plant producers. The objective of this work was to determine the effects, if any, of daylength control on the growth and flowering of the following genera; Barleria cristata, Angelonia angustifolia `Pandiana', Stachytarpheta mutabilis var. violacea, Streptosolen jamesonii, Mandevilla sanderi, Dichorisandra thyrsiflora, and Pseuderanthemum laxiflorum. Daylength of 8, 10, 12, or 14 h was imposed for 20 weeks, with cuttings harvested from plants every 4 weeks. At 20 weeks, plants were evaluated for degree of flowering and plant size. Photoperiod had a significant interaction with genera grown. Compared to plants grown under 14-h daylength; flowering and growth were reduced in Stachytarpheta and Angelonia at 8- and 10-h daylength. Flowering was increased, but overall growth reduced in Pseuderanthemum, Mandevilla, Barleria, and Dichorisandra as daylength decreased. Flowering of Streptosolen was not evident under any photoperiod. Vegetative growth was greatest with 14 h daylength for all genera tested, but only increased flower number of Stachytarpheta. Production temperatures of 20 °C night and 30 °C day were maintained throughout the study, the experiment was conducted in the summer production seasons of 1997 and 1998.

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

`Improved Mefo' chrysanthemums were grown at 22C/18C and 34C/28C day/night temperature regimes to evaluate the failure of lateral bud development following pinching of this temperature sensitive cultivar. The number of viable buds on plants at the high temperatures was 40% of number at low temperature. Loss of bud viability was categorized as those buds that were: 1) absent, or 2) those in which growth was present, but inhibited. Inhibited buds were visible swellings surrounded by dense masses of secondary cell wall material. Anatomical studies were completed to verify the absence of lateral buds and determine what cellular changes imposed inhibition on those buds that did develop. A second group of experiments demonstrated that moving low-temperature plants to the high temperature caused production of viable buds to decline. Plants were moved from high temperatures to low, and reciprocally to high from low temperature. Anatomical sampling of apical meristems began at time of shift and at 1, 2, 4, and 8 days after temperature shift. High-temperature meristems possessed predominantly non-viable lateral buds, with few viable buds present.

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Kimberly A. Klock-Moore, George E. Fitzpatrick and Richard K. Schoellhorn

As the horticulture industry enters the 21st century, advances in horticulture science will continue to be more rapid and frequent creating the need for more innovative approaches in information delivery. Moreover, decentralization continues to be a widespread trend. Land-grant universities have a long tradition of providing outreach, but with the development of new telecommunication technologies, larger audiences now can be reached. Many universities throughout the world have developed distance education programs through the use of modern telecommunication technologies. However, the University of Florida has responded to the needs of place-bound students by developing off-campus resident Bachelor of Science (BS) degree programs in horticulture at three locations in the state. These off-campus programs combine on-site instruction augmented with distance education courses to giveplace-bound students a flexible, efficient, and interactive alternative to degree programs offered at the main campus.

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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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Richard O. Kelly, Zhanao Deng, Brent K. Harbaugh and Rick K. Schoellhorn

Florida is one of the top wholesale producers of bedding plants, and in 2003 was ranked fourth in annual bedding plant production and fifth in potted pansy/viola production. Evaluation of pansy cultivars is vital for continued growth of the industry. We evaluated 210 cultivars of pansy (Viola ×wittrockiana) (164 new cultivars) in replicated class tests at the University of Florida's Gulf Coast Research and Education Center at Bradenton, Fla., from 2000–04 to determine the best-of-class and use them in future trials to compare against new entries in the same class. In this report, we provide objective plant measurements of vegetative and floral characteristics as well as subjective performance ratings. Subjective ratings were on a 1 to 7 scale with the highest rating of 7 for excellent. In general, overall performance ratings (combined foliage, flower, arthropod, and disease ratings) ≥5.5 were considered outstanding. Pansy cultivars were grouped into classes based on flower color and pattern. Best-of-class selections that had an outstanding overall performance rating in one or more contested trials, never falling below 5.0 in other contested trials, were: (black class) `Accord/Banner Black Beauty', (blue shades/tints class) `Nature Blue', (blue with blotch class) `Nature Ocean', (mix class) `Panola Clear Mixture', (pink shades/tints with blotch class) `Nature Pink Shades', [purple (dark), blue-violet with white cap class] `Nature Beacon', [purple (dark), blue-violet/white face with blotch class] `Panola Purple With Face', (purple with light eye class) `Baby Bingo Lavender Blue', (white class) `Nature White', (yellow class) `Nature Yellow', (yellow with blotch and purple, blue-violet cap class) `Iona Purple & Yellow With Blotch', (yellow with blotch and red cap class) `Bingo Red & Yellow', (yellow with blotch and red cap class) `Panola Yellow With Blotch', (yellow with dark veins class) `Whiskers Yellow'. We believe these cultivars would perform well in the southern U.S. or areas of the world with similar heat and cold hardiness zones.

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Helen E. Hammond, Richard K. Schoellhorn, Sandra B. Wilson and Jeffrey G. Norcini

Two different plant growth regulators were applied to ‘Torch Flame’ blanketflower (Gaillardia pulchella) and a native blanketflower ecotype to reduce pedicel elongation and final production size. Uniconazole was applied as a spray at 60, 120, and 180 mg·L−1 or as a drench at 6, 12, and 24 mg·L−1 one and two times per plant. Ethephon was applied as a spray at 500 and 1000 mg·L−1 one and two times per plant. When applied as a spray, uniconazole had no effect on torch blanketflower, but when applied as a drench, growth indices were reduced by 12% to 30% without delayed flowering. When treated with ethephon spray, torch blanketflower was 15% to 25% more compact than untreated controls, but flowering was delayed. The blanketflower ecotype did not respond to uniconazole or Ethephon treatments, regardless of the application rate, number, or method.

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

Effects of heat stress on viable and nonviable axillary meristem development and subsequent lateral branching in 'Improved Mefo' chrysanthemum [Dendranthema ×grandiflorum Ramat. (Kitamura)] were studied. Plants grown at 33 °C day/27 °C night produced more nonviable buds than did plants grown at 23 °C day/18 °C night. A negative linear relationship {y = 28.7 + [-0.66 (x days)], r 2 = 0.70} between timing of exposure to high temperatures and the number of nonviable buds was observed. Histological examination 28 days after exposure to 33 °C/27 °C revealed that plants showed both normal and abnormal bud development. Abnormal bud development occurred as a consequence of premature differentiation of axillary meristematic tissue into nonmeristematic parenchyma tissue immediately after separation of axillary from apical meristems.

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Edwin R. Duke, Kimberly A. Klock, George E. Fitzpatrick and Richard K. Schoellhorn

Florida is one of the nation's leading states in citrus, foliage, vegetable, and ornamental crop production. The Univ. of Florida is the only public institution in the state of Florida that offers a bachelors degree in horticulture and /or environmental horticulture. The main campus in Gainesville is centrally located ≈400 to 500 miles from either end of the state. Changing population demographics within Florida have emphasized the necessity of developing programs to reach non-traditional students. Students who are place bound due to work or other responsibilities represent an increasing part of the potential market. The Univ. of Florida, recognizing the specialized needs of non-traditional students, established Bachelors of Science degree programs in environmental horticulture at the Fort Lauderdale and Milton research and education centers. The centers teach the same core curriculum being taught in Gainesville, but the centers also teach additional courses specific to their geographic location to allow for a tailored program. The off-campus facilities have teaching faculty at the centers to teach the courses and also use satellite technology to down link courses from Gainesville. The development of off-campus programs in Fort Lauderdale and Milton allow the Univ. of Florida to improve the effectiveness of educational programming to reach place-bound students.