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Harry K. Tayama and Stephen A. Carver

Residual activity of a single uniconazole spray (15 mg a.i./liter), uniconazole drench (600 μg a.i./pot), and daminozide spray (5000 mg a.i./liter) were compared to an untreated control using the `Bright Golden Anne' chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura]. Based on weekly internode growth, spray and drench treatments with daminozide and uniconazole remained active for 2 to 2.5 and 3 to 3.5 weeks, respectively. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); (E)-1-(p-chlorophenyl)-4,4-diemethyl 1-2(1,2,4-triazol-2-yl)-l-penten-3-01 (uniconazole).

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Harry K. Tayama and Stephen A. Carver

Uniconazole spray or drench applications to `Yours Truly' zonal geranium (Pelargonium × hortorum L.H. Bailey) and `Bright Golden Anne' and Yellow Favor' chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitamura] were made to evaluate efficacy and identify optimum application concentrations. Spray applications at 10 mg a.i./liter retarded stem elongation in unpinched zonal geranium comparable to chlormequat at 1500 mg a.i./liter. `Bright Golden Anne' was more sensitive to uniconazole than `Yellow Favor'. Uniconazole spray concentrations of 20 to 30 mg a.i./liter retarded plant height equal to daminozide at 5000 mg a.i./liter. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); (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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Stephen A. Carver and Harry K. Tayama

The influence of poinsettia (Euphorbia pulcherrima Wild. ex Klotzsch) stock plant shoot maturity on subsequent splitting of cuttings taken from the shoots was evaluated. Terminal cuttings (7.5 cm) taken from `Lilo' poinsettia stock plant axillary shoots that had 4, 8, or 12 nodes were rooted, planted, then observed for initial signs of splitting (conversion of the vegetative terminal buds into floral buds). The percentages of cuttings that split were 22, 77, and 100 for those taken from shoots with 4, 8, and 12 nodes, respectively. By implication, cuttings should be taken just as stock plant axillaries reach a size adequate for propagation to help reduce the incidence of splitting.

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Harry K. Tayama and Stephen A. Carver

A series of crop-specific, resin-coated, controlled-release fertilizer formulations, including: Sierra Geranium Mix 13-12-11 Plus Minors, Sierra Chrysanthemum Mix 12-10-17 Plus Minors, and Sierra Poinsettia Mix 12-12-15 Plus Minors were preplant-incorporated into Metro Mix 350 growing medium for the production of potted zonal geraniums, chrysanthemum, and poinsettia. Plant growth and foliar nutritional responses were compared to those obtained from plants produced with a standard resin-coated, controlled-release Osmocote formulation (19N-6P-12K), water-soluble Peters 20N-10P-20K, and a combination of water-soluble and resin-coated treatments. Crops produced with specialty resin-coated mixes (at recommended rate = l×) were equal in growth and flowering characteristics to those produced with Osmocote (1×), water-soluble (200 ppm nitrogen), or a combination of water-soluble (200 ppm nitrogen) and resin-coated (0.5×) fertilizer treatments. Foliar analyses revealed elemental concentrations in resin-coated fertilizer-treated plants were below those in water-soluble or combination treatments, but were within a range to support satisfactory quality crop production.

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Stephen A. Carver, Michael Knee, and Harry K. Tayama

Dendranthema grandiflora `Spirit' and `Iridon' were grown in a 2-factor experimental design consisting of 3 nitrogen rate/source treatments (100 mg/liter N (25% NH4 +}, 400 mg/liter N (25% NH4 +}, and 400 mg/liter N {5% NH4 +}), and 2 fertilizer termination treatments (bud-color and harvest) Evaluation of various production characteristics including plant and flower size, days to flower, leaf number and size, and leaf, shoot, flower and root fresh/dry weight, revealed few significant differences among treatments. High foliar N content in all treatments (ranging from 6.1 to 8.5%) may provide an explanation for the apparent lack of differential treatment production response. However, there were significant treatment differences in floral and foliar postharvest keeping quality. High NH4 + grown plants declined 1-2 weeks sooner than other treatments, and plants fertilized to harvest declined 0.5-1 week sooner than those fertilized to bud color. Root fresh and dry weights measured 2 weeks into postproduction disclosed significant differences between treatments that mirrored foliar and floral longevity. Results of a satellite study in which root and stem hydraulic conductivity, root total soluble carbohydrates, starch, and protein content, and water loss rate during postharvest will be presented.

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Harry K. Tayama and Stephen A. Carver

Two experiments were conducted to compare the efficacy of uniconazole (10-ppm spray and drench), paclobutrazol (15-ppm spray and drench), triapenthenol (132-ppm spray and drench), chlormequat (1500-ppm spray only), ethephon (500-ppm spray only), and chlormequat + daminozide (2500 + 1500 ppm spray only) combination for controlling stem elongation of zonal (cutting) geraniums [Pelargonium hortorum (L.H. Bailey)]. Additionally, the effect of these materials on days to anthesis, inflorescence number, and phytotoxicity was evaluated. Spray applications provided effective height control and did not affect days to anthesis or inflorescence number. Drench applications severely restricted growth and reduced inflorescence number, but did not delay flowering. None of the treatments was phytotoxic. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-l,2,4-triazole-1-ethanol (paclobutrazol); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat); α-cyclopropyl-α-(4-meth-oxyphenyl)-5-pyrimidinemethanol (ancymidol); (2-chloroethyl) phosphoric acid (ethephon); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); β-(cyclohexylmethylene)-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (triapenthenol); (E)-1-(p-chlorophenyl)-4,4-diemethyl 1-2(1,2,4-triazol-2-yl)-1-penten-3-o1 (uniconazole).

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N.R. Bhat, Thomas L. Prince, Harry K. Tayama, and Stephen A. Carver

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Yusef S. Siraj-Ali, Harry K. Tayama, Thomas L. Prince, and Stephen A. Carver

The relationship between poinsettia (Euphorbia pulcherrima Willd. ex Kl.) maturity and premature flower bud initiation (splitting) was evaluated. Changes in root growth, phyllotaxy, and heterophylly of `Annette Hegg Dark Red' poinsettia stock plants and cuttings in response to repeated severe pruning (hedging) and the chemical growth regulators gibberellic acid (GA4+7), PBA, or ethephon were evaluated. Cuttings taken from hedged stock plants exhibited a phyllotaxy of 1/3 to 2/5, extensive root growth (characteristics of juvenility in poinsettia), and a low level of splitting (34%). Cuttings taken from nonhedged stock plants exhibited a phyllotaxy of 3/8, reduced root growth (characteristics of maturity in poinsettia), and a high level of splitting 177%). There was a moderate negative correlation (-0.75) between root growth and splitting and a strong positive correlation (0.94) between splitting and phyllotaxy. Cuttings treated with gibberellic acid or PBA exhibited elliptic to ovate leaves (a juvenile characteristic) and levels of splitting ranging from 20% to 90%, depending on concentration and application timing. Untreated cuttings and those treated with ethephon exhibited lobed leaves (an adult characteristic) and levels of splitting ranging from 82% to 100%. Names of the chemical growth regulators were: trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid 1,-4a-lactone (GA4+7); N-(phenylmethyl)-9-)tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (2-chloroethyl) phosphonic acid (ethephon).

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Yusef S. Siraj Ali, Harry K. Tayama, Thomas L. Prince, and Stephen A. Carver

Experiments were conducted with poinsettia [Euphorbia pulcherrima (Willd. ex. Klotzsch)] to determine the 1) existence of developmental phases from seedling establishment to flower induction and 2) characteristics that may be used to delineate the phases. The characteristics evaluated were flowering and rooting ability, heterophylly and other leaf characteristics, phyllotaxy, and internode characteristics. Two developmental phases, juvenility and maturity, were identified. The transition between these phases occurred in poinsettias that were 6 to 8 weeks old, following establishment. Mean values for flowering ability, rooting ability, phyllotaxy, and heterophylly differed for the two developmental phases, rendering them the most useful of the characteristics evaluated for identifying developmental phases in poinsettia.