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Janet C. Henderson and Thomas H. Nichols

Pyracantha coccinea M.J. Roem. `Kasan' and `Lalandei' were treated with a soil drench of 30 mg a.i. chlormequat chloride per container or 0, 0.25, 0.50, or 1.00 mg a.i. uniconazole per container or with a foliar application of 3000 mg a.i. chlormequat chloride/liter or 0, 25, 50, or 100 mg a.i. uniconazole/liter. Chlormequat chloride applied as a drench did not affect growth of `Kasan' or `Lalandei' until 17 weeks after application, when `Kasan' was taller and `Lalandei' shorter than untreated plants. `Kasan' plants drenched with chlormequat chloride had more leaves with greater total leaf area and higher leaf and stem dry weights than untreated plants. However, area per leaf, root dry weight, and root: shoot ratio were not affected by the chlormequat chloride drench. In `Lalandei', the chlormequat chloride drench did not affect any of these criteria, except stem dry weight. Foliar applications of chlormequat chloride had little effect on either cultivar. Height of `Kasan' and `Lalandei' decreased with increasing uniconazole rates for both application methods. Area per leaf increased in `Kasan' but decreased in `Lalandei' receiving a drench applied to the medium. Foliar and drench applications of uniconazole both resulted in decreased stem dry weight of both cultivars. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole).

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Gary J. Wilfret

Plant growth and flower development of Easter lilies (Lilium longiflorum) were evaluated for 3 years (1988-90). Bulbs of cvs. Ace and Nellie White were soaked preplant in solutions of uniconazole at cones. of 0 to 5 ppm at durations of 1 to 5 minutes and compared to bulbs soaked in ancymidol at 5 to 40 ppm. Time of bulb soak had no effect on amount of solution absorbed and on growth and flower development. Plant height from bulbs soaked in water alone was variable among the 3 years, ranging from 56 to 70 cm for Nellie White and 55 to 89 cm for Ace. Ancymidol concs. of 5, 10, 20, and 40 ppm retarded plant height 10.8, 14.5, 33.8, and 46.2%, respectively. Uniconazole solutions at 0.625, 1.25, 2.5, 5, 10, and 20 ppm produced Nellie White plants 16.7, 70.4, 56.8, 46.9, 39.3, and 30.8% of the height of the water soaked bulbs, respectively. Response of Ace to similar uniconazole concentrations was slightly less. High uniconazole concentration (> 5 ppm) delayed flowering time and reduced the number of floral buds which developed. Variability among plants within uniconazole treatments was large and would not be acceptable commercially.

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Brian E. Whipker and P. Allen Hammer

Plant growth retardant (PGR) substrate drench treatments (mg a.i./1.5-L pot) of ancymidol at doses of 0.5 to 8, paclobutrazol from 1 to 16, and uniconazole from 0.125 to 2 were applied to tuberous-rooted dahlias (Dahlia variabilis Willd.) to compare their effectiveness for controlling height. When the first inflorescence opened, the number of days from potting until flowering, leaf canopy height, inflorescence height above the foliage, and plant diameter were recorded. Total height control achieved using PGRs was primarily due to reduced inflorescence height, rather than leaf canopy height. Paclobutrazol, ancymidol, and uniconazole at all doses reduced total plant height of the less-vigorous `Red Pigmy' by >21% compared to the untreated control, with a height of 43.5 cm for the untreated control plants. Marketable potted plants were produced with doses of 2 to 4 mg of paclobutrazol, 0.25 to 0.5 mg of uniconazole, or 0.5 mg of ancymidol. All paclobutrazol, ancymidol, and uniconazole doses reduced total plant height of the more-vigorous `Golden Emblem' by >11% compared to the untreated control, with a height of 82.1 cm for the untreated control. Marketable potted plants were produced with 4 to 8 mg of paclobutrazol, 0.5 to 1 mg of uniconazole, or 2 mg of ancymidol.

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Hermen Malik and Douglas D. Archbold

The potential for plant growth regulator (PGR) manipulation of `Chester Thornless' blackberry (fibus spp.) primocane growth was evaluated. PGR treatments included combinations of soil-applied uniconazole at 1, 5, 25, and 125 mg/plant and GA, foliar-applied one or two times at 100 ppm 3 and 4 weeks after a 25-mg/plant uniconazole application. Also, GA and BA were applied at 100 ppm alone or in combination one, two, or three times. Increasing rates of uniconazole reduced primocane length, leaflet count, and leaf, cane, and root dry weights. GA, applications reduced primocane length and increased branch elongation but failed to reverse the effects of uniconazole at 25 mg/plant, except those on branch length, leaflet count, and primocane dry weight. Only applications of BA + GA, increased both branch production and elongation and dry weights of some component tissues, while BA alone generally had no effects. Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole); N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); gibberellic acid (GA).

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Yin-Tung Wang

Hibiscus rosa-sinensis `Jane Cowl' were pruned several weeks after receiving 0.1 mg/pot uniconazole soil drenches to retard the growth. Plants then received foliar sprays of GA3 (50 ppm), KIBA (200 ppm), or PBA (200 ppm) immediately after pruning or when the lateral shoots had three leaves. Application of the above growth regulators immediately after pruning had no effect on plant growth. When treatments were delayed until the three-leaf stage, GA3 completely restored leaf production rate and partially restored shoot elongation and pedicel length. GA3 also increased leaf area, and the leaf specific weight was similar to leaves on plants not receiving uniconazole. GA3 increased flower production 175% and 65% more than plants treated with uniconazole and the untreated plants, respectively. KIBA and PBA had no effect on altering the growth of uniconazole-treated plants. Foliar application of a combination of GA3, KIBA and PBA at the three-leaf stage had an effect similar to that of GA3 alone. However, the effect of GA3 on growth appeared to be transient and repeated application may be required to maintain the restored growth of uniconazole-treated plants.

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Terri Woods Starman

This study investigated the effects of concentration and application time of uniconazole as a spray for single- or double-pinched ornamental pepper (Capsicum annuum L. `Holiday Cheer'). Concentrations from 5.0 to 15.0 mg·liter-1 gave adequate height control, except that 15.0 mg·liter-1 reduced height excessively when applied 8, but not 10, weeks after sowing. Increasing uniconazole concentration increased red fruit percentage when applied at 10, but not 8, weeks after sowing. These results indicate that the later application was beneficial and may lessen the overdosing problem associated with triazole growth regulators. Chemical name used: (E)-(S)-1-(4-chlrophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-oll(uniconazole).

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Robert M. Frymire and Janet C. Cole

Uniform rooted cuttings of pyracantha (Pyracantha coccinea M.J. Roem. 'Lalandei') were potted into 3.8 liter containers in a pine bark:sand medium. Plants were treated with a medium drench at 0.5 mg ai per container, or a foliar spray at 150 mg ai per liter, or no uniconazole. Plants also were exposed to one of three irrigation regimes: nonstressed, stressed or acclimated. Uniconazole had little effect on leaf water potential, osmotic potential, transpiration or leaf conductance. The uniconazole drench treatments reduced plant growth and increased N, Ca, and Mn concentrations in the leaves. Foliar applications had less effect on plant growth and elemental content Acclimated and stressed plants had lower water and osmotic potentials, transpiration rates and leaf conductance than nonstressed plants on the final day of the stress cycle. Acclimated plants had higher levels of N and Mn with lower levels of Zn in the leaves than either stressed of nonstressed plants.

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Mike A. Nagao, Elodie B. Ho-a, and Judy Yoshimto

Uniconazole at 0.20 g-ram of a.i./cm of trunk diameter was applied as a drench to potted 2 year-old M. integrifolia cv. Kau trees in July 1990, and reapplied in August 1991, August 1992 and August 1993. Observations between December 1991 to December 1993 showed that elongation of newly emerging vegetative flushes was inhibitedwithin 6 months after the initial treatment. Shoots had a compact appearance, and the overall height of the trees was shorter than in untreated trees. By December 1993, diameters of the treated trees were also signficantly smaller than the controls. Uniconazole increased the number of racemes, number of racemes with mature fruit set and fruit production in young trees during the 1992 and 1993 seasons. The effect was more pronounced in 1992 compared to 1993. Results from this study show that young macadamia trees can be brought into heavier bearing at an early age with uniconazole treatments.

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Brian E. Whipker, Shravan K. Dasoju, and Michael R. Evans

Drench applications of paclobutrazol or uniconazole were applied at doses of 0, 0.0025, 0.005, 0.01, 0.02, or 0.04 mg a.i./pot (28,350 mg = 1.0 oz) to vegetatively propagated `Aurora', `Medallion Dark Red', and `Pink Satisfaction' geranium (Pelargonium ×hortorum L.H. Bailey). Geranium total plant height, leaf canopy height, and plant diameter responded similarly to drench applications of either paclobutrazol or uniconazole. There was a significant quadratic relationship between plant growth regulator (PGR) dose and total plant height and leaf canopy height for `Aurora' and `Medallion Dark Red', with total plant height and leaf canopy height being shorter as paclobutrazol or uniconazole doses increased up to 0.02 mg. However, doses of ≥0.02 mg had little additional effect on total plant height and leaf canopy height. Most of the total height control achieved by the use of PGRs was primarily due to a reduction of leaf canopy height, rather than inflorescence height. Doses of 0.005 to 0.01 mg of either PGR produced marketable sized potted plants of `Medallion Dark Red' and `Pink Satisfaction'. `Aurora', which was the most vigorous cultivar, required doses of 0.01 or 0.02 mg of either paclobutrazol or uniconazole to produce marketable sized potted plants.

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J.E. Barrett, R.K. Schoellhorn, C.A. Bartuska, D.G. Clark, and T.A. Nell

Uniconazole was applied as a spray to the surface of container media prior to planting bedding plant plugs. This medium spray was compared to a standard whole-plant spray applied 2 weeks after planting. For petunia (Petunia ×hybrida Vilm.) and coleus (Solenostemon scutellarioides L.) the efficacy of the medium spray was similar to the whole-plant spray. However, for impatiens (Impatiens wallerana Hook. f.) and vinca [Catharanthus roseus (L.) G. Don.] the medium spray had greater efficacy than the whole-plant spray. Increased concentrations of uniconazole in the medium spray decreased plant height; however, the effect of higher concentrations was greater in a medium with out pine bark compared to a medium with pine bark as a component. In the above experiments, uniconazole was applied in a volume of 200 mL·m-2. In a test where spray volume varied, there was a negative linear relationship between plant height and spray volume. Chemical name used: (E)-(+)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ane-3-ol (uniconazole).