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Rebecca A. Schnelle and James E. Barrett

The paclobutrazol liner dip is a plant growth regulator application technique that is becoming widespread in the commercial bedding plant industry. This technique, in which plug trays are dipped in a solution of paclobutrazol before transplant, is an efficient method for applying this growth regulator to a large number of plants. In previous studies, significant variability in size control was documented following liner dip treatments with identical solution concentrations. To elucidate the causes of this variability, three bedding plant species with varying levels of paclobutrazol sensitivity (Petunia ×hybrida, Impatiens wallerana, and Scaevola aemula) were treated with paclobutrazol liner dips under various conditions. Four factors identified in previous studies that may impact the efficacy of paclobutrazol liner dips were evaluated in this study. The age of the cuttings at the time of treatment ranged from 2 to 4 weeks after propagation. The light intensity incident to the plants from 2 h before through 2 h following the time of treatment ranged from about 1000 μmol·m-2·s-1 in a greenhouse to 5 μmol·m-2·s-1 indoors. The relative moisture content of the plug media before the treatment was saturated or at 25%, 50%, or 80% dry down by weight, based on air-dried media. The amount of time the plug media remained in the paclobutrazol solution was 10 s, 30 s, or 2 min. Data were collected on stem elongation 3 weeks after transplanting and again 2 weeks later. The results confirm that all four factors tested interact with the concentration of paclobutrazol in the dip solution to determine the control in stem elongation achieved by the treatment.

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Jennifer K. Boldt and James E. Barrett

A daminozide plus chlormequat chloride tank mix spray was applied to six Coleus cultivars or breeding lines at different times during propagation. For UF 03-8-10 and `Coco Loco', plants sprayed on day 7 or day 10 were shorter than control plants at transplant, but plants sprayed on day 13 were not. Other cultivars did not respond to single applications. Five of the six cultivars responded to application on days 7 and 13. Plants of UF 03-8-3 and `Coco Loco' were significantly shorter than control plants at transplant. Plants of UF 03-8-10, UF 03-6-1, and UF 03-17-8 were shorter than control plants at 3 weeks after transplant. `Hurricane Louise' did not respond to the tank mix. A second study found a cultivar specific response to three chemical treatments applied as a spray on day 10 of propagation. At transplant, UF 03-8-10, UF 03-8-3, UF 03-6-1, and `Coco Loco' plants sprayed with the tank mix at 2500 plus 1500 mg·L-1, respectively, were significantly shorter than the control plants. A uniconazole spray at 2 mg·L-1 reduced elongation in UF 03-8-10, UF 03-8-3, and UF 03-6-1, compared to control plants. Ethephon at 250 mg·L-1 reduced elongation in UF 03-8-10, UF 03-8-3, and `Coco Loco' plants. None of the chemical sprays reduced elongation in `Hurricane Louise' at the concentrations applied. Ethephon increased axillary branching in all cultivars, and induced lower leaf abscission in UF 03-17-8 and `Hurricane Louise'; leaf malformation in UF 03-6-1 and `Coco Loco'; and color alteration in UF 03-6-1, UF 03-8-3, and `Coco Loco'.

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James E. Barrett and Terril A. Nell

Impatiens L. wallerana Hook., Salvia splendens Sello ex Nees, Tagetes erecta L., and Petunia hybrida Vilm. plants in 610-cm3 pots were sprayed with either uniconazole or paclobutrazol at concentrations from 10 to 160 mg·liter-1. For all species, both chemicals reduced plant size compared with untreated control plants, and the effect increased with higher concentrations. Uniconazole produced smaller plants than did paclobutrazol at similar concentrations. For impatiens, salvia, and marigold, there was an interaction between chemical and concentration; the degree of difference between the effects of the chemicals was greater at higher concentrations. For these three species, uniconazole elicited a quadratic response and reached saturation within the concentrations used; however, these concentrations were still in the linear portion of the dose response curve for paclobutrazol. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-2-(1,1-dimethylethyl)-(1H-1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol); (E)-(+)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).

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Rebecca A. Schnelle and James E. Barrett

The influence of several environmental and cultural factors on the efficacy of paclobutrazol liner dips were evaluated for three species of bedding plants: ‘Fancy’ scaevola (Scaevola aemula), ‘Suncatcher Plum’ petunia (Petunia ×hybrida), and ‘Double Fiesta Rose’ impatiens (Impatiens walleriana). The impact of paclobutrazol concentration in the dip solution, location of treatment, root substrate moisture status, and time in the dip solution were investigated. Before the liner dip application, the rooting substrate was brought to a specific percentage of container water capacity (20%–100%). Liners were then dipped in a paclobutrazol solution of the prescribed concentration (1–16 mg·L−1) for a prescribed time interval (10–300 s) in a specific location (open-wall greenhouse, polyethylene-glazed greenhouse under 80% shade fabric, three-wall potting shed, or building interior). Plant size data were collected when the untreated control plants reached a marketable stage. Paclobutrazol concentration and root substrate moisture status had a significant effect on size control, but location and dip duration did not. Size suppression varied by species. Following a liner dip at 2 mg·L−1, scaevola, impatiens, and petunia plants were 44%, 26%, and 11% smaller than the untreated controls, respectively. Petunia plants dipped in a 8 mg·L−1 paclobutrazol solution with substrate moisture status of 100%, 90%, 80%, 70%, 50%, or 20% of container capacity were 11%, 8%, 25%, 30%, 41%, or 42% smaller than the untreated control, respectively (30 s dip duration, open-wall greenhouse). Petunia plants dipped in a solution of 8 mg·L−1 paclobutrazol for 10, 30, 120, or 300 s were all between 18% and 23% smaller than the control (50% of container capacity, open-wall greenhouse). Petunia plants dipped in an 8 mg·L−1 paclobutrazol solution in all four locations were all 20% to 21% smaller than the untreated control.

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James E. Barrett and Terril A. Nell

Bedding plant seedlings were obtained as plugs from commercial sources, transplanted into 10-cm pots, and grown using standard commercial procedures. When plants reached a marketable stage, they were treated with Hydretain, moved to a heavy shaded bench in the greenhouse, and time to first wilt was determined. At wilt, plants were given 180 ml of water, and time to second wilt was observed. Hydretain was applied directly to the media in a volume of 90 ml per pot. Hydretain dilutions in water were 1:4, 1:9, 1:14, 1:19, and 0:1 (controls). Time to first wilt in 'Red Elite' geraniums was 11, 10, 9, 10, and 5 days, respectively. For 'Little Bright Eyes' vinca, first wilt was in 7, 8, 5, 5, and 4 days; and time from treatment to second wilt was 18, 14, 11, 10, and 8 days, respectively. For 'Super Elfin Red' impatiens, first wilt was in 5, 4, 4, 3, and 3 days; and the water absorbed was 121, 167, 172, 132, and 148 ml, respectively. Second wilt was in 7, 7, 8, 5, and 5 days, respectively.

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James E. Barrett and Terril A. Nell

`V-14 Glory' poinsettias in 15-cm pots were pinched on 24 Sept. and given long days until 8 Oct. Chemical treatments were paclobutrazol drench, paclobutrazol spray, or daminozide/chlormequat (D/C) spray. Time of application was between 8 Oct. and 12 Nov. Heights ranged between 27 and 31 cm. D/C reduced bract size more than paclobutrazol spray, and for both, later treatments had greater affect. Paclobutrazol drench did not have a significant affect.

A second experiment had two cultivars, `Freedom' and `V-14'; three paclobutrazol concentrations, 0.2, 0.3 or 0.4 mg per pot; and three application times, 30 Sept., 14 Oct. or 28 Oct. Treatment on 30 Sept. produced the smallest bracts. The cultivar × concentration interaction was significant with 0.4 mg reducing bract size for `Freedom' but not `V-14'. Treatments on 28 Oct. had less effect on height than the other two dates. `Freedom' were shorter than `V-14'. and higher concentrations had more effect on `Freedom' than `V-14'.

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James E. Barrett and Terril A. Nell

Euphorbia pulcherrima cvs. Freedom, SUPJIBI, and Celebrate 2 were sprayed with paclobutrazol or a tank mix of daminozide and chlormequat at week 40, 41, 42, 43, or 44. Application time had little effect on plant size. The tank mix had greater efficacy on `Freedom' but not on the other cultivars. Interactions for bract size indicated: 1) time of application had less effect on `Freedom', 2) there was little difference between the chemicals on `SUPJIBI', but the tank mix had greater efficacy on the other cultivars, and 3) the tank mix had greater efficacy than paclobutrazol during weeks 41, 42, and 43.

`Freedom', `Celebrate 2', `SUPJIBI', and `V-14 Glory' were planted on 8 or 15 Aug. and placed under short days on 12, 19, or 26 Sept. `Freedom' reached anthesis between 30 Oct. and 6 Nov., about 5 days before `SUPJIBI' and `Celebrate 2' and 7-10 days ahead of `V-14 Glory'. `Freedom' planted in Aug. and given short days 14 days apart flowered only 7 days apart (40 to 47 days from start of short days), but when planted in Sept. flowering was in 54 days and each long day resulted in 1 day delay in flowering.

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Christopher B. Cerveny, James L. Gibson and James E. Barrett

Orange Jasmine (Murraya paniculata L. Jack) and Texas Star [Tecoma stans (L.) Juss.] are two tropical ornamentals which have become popular in the specialty floriculture crop market because of their outstanding flower characteristics. Unfortunately they are difficult to root and little has been published on how to propagate them effectively. Therefore, the objective of our experiment was to determine the optimum physiological age of stem tissue necessary to effectively root 2-node stem cuttings. Forty-five cm shoots of Murraya were harvested on 27 June and 7 Sept. 2005, and divided into 2-node stem cuttings representing the top, middle, and bottom sections of the stem (soft-wood, semi-hardwood, and hardwood, respectively). Cuttings were measured for stem length and diameter, dipped in a 1,500 mg·L–1 solution containing indolebutyric acid (IBA) 1%: napthaleneacetic acid (NAA) 0.5%, and propagated under mist for 10 weeks in a 4 perlite: 1 vermiculite substrate (by volume). Tecoma followed a similar regime but were harvested once on 13 Sept. and evaluated 4 weeks after planting. Both species were evaluated for percent survival and rooting quality on a 1 to 5 scale; 1 = poor, 5 = best. Stem quality differences in Tecoma cuttings were shown, but did not influence rooting performance or percent survival. Murrayacuttings indicated a similar trend suggesting that age of tissue is not an important factor when propagating these species. However, when comparing the two harvest dates, data from Murraya cuttings showed an increase in survival from 79% and 95% and an increase in rooting quality from 2.72 to 4.26 when harvested in June compared to Sept., respectively. Cuttings harvested in Sept. were also shown to be 17% shorter with a 126% larger diameter than those harvested in June. These data suggest a trend toward a seasonal effect when harvesting cuttings of Murraya paniculatain Florida. Further studies should be conducted to verify this trend and to identify the ideal season for propagation.

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Terril A. Nell, Ria T. Leonard and James E. Barrett

Production irradiance levels on growth, light compensation point (LCP), dark respiration (DR), and interior longevity of potted chrysanthemum (Demfranthema grandiflora Tzvelev. cvs. Iridon and Mountain Peak) and poinsettia (Euphorbia pulcherrima Wind. cvs. Annette Hegg Dark Red and Gutbier V-10 Amy) were determined. LCP and DR were measured at anthesis and during acclimatization to interior conditions (10 μmol·s-1·m-2). Days to flowering, inflorescence diameter, total chlorophyll, and interior longevity of chrysanthemum increased when maintained at a mean maximum photosynthetic photon flux density (PPFD) of 500 μmol·s-1·m-2 compared to plants shifted to 300 or 100 μmol·s-1·m-2 8 weeks after planting. LCP and DR were highest at anthesis and were reduced 38% and 49%, respectively, for chrysanthemum and 19% and 42%, respectively, for poinsettia within 3 days in interior conditions. Chrysanthemum plants shifted to 300 μmol·s1·m-2 during production had lower LCP and DR rates at anthesis and throughout time in interior conditions compared to plants maintained at 500 μmol·s-1·m-2. The acclimatization of chrysanthemum to reduced production PPFD is of little significance because interior longevity is reduced. No differences were found in the LCP or DR of poinsettia or chrysanthemum cultivars that differ in interior performance, demonstrating that these physiological characteristics are not good indicators of interior longevity for chrysanthemum and poinsettia.

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Terril A. Nell, Ria T. Leonard and James E. Barrett

Postproduction characteristics of the new poinsettia cultivar `Freedom', as influenced by production and postproduction treatments, were evaluated. In one study, plants were grown under three production irradiance levels consisting of 450, 675 or 900 μmol s-1m-2 at 18/24C or 22/28C night/day temperatures and moved at anthesis to postproduction conditions (10 μmol s-1m-2 for 12 hr/day, 21±2C). Anthesis was delayed, plant height and diameter decreased, and a reduction in the number and development of cyathia occurred when maintained at low production temperature and irradiance. Leaf drop, which was minimal after 30 days postproduction (< 25%), was unaffected by production treatments, while cyathia drop was accelerated by low production irradiance and temperature, but not reduced after 30 days.

Leaf retention and quality in postproduction conditions are excellent. Cyathia drop averages 40 to 50% after 2 weeks in postproduction conditions. Bracts and leaves maintain their color well, with only slight fading after 30 days. Plants exhibit slight epinasty after shipping, but recover within a couple of days. These characteristics of `Freedom' make it a promising variety for the future.