scholarly journals Using Paclobutrazol to Control Height of Poinsettia `Freedom'

2002 ◽  
Vol 12 (2) ◽  
pp. 232-236 ◽  
Author(s):  
Genhua Niu ◽  
Royal Heins ◽  
Will Carlson
Keyword(s):  
Plant Height ◽  
Stem Elongation ◽  
Flower Initiation ◽  
Euphorbia Pulcherrima ◽  
Application Time ◽  
Growth Retardants ◽  
Height Control ◽  
Area Reduction ◽  
Crop Development ◽  
Short Days

Late-season height control of poinsettia (Euphorbia pulcherrima) is difficult since most chemical growth retardants adversely reduce bract size when applied after first bract color. Paclobutrazol (Bonzi) controls stem elongation late in poinsettia crop development but can excessively reduce bract size if improperly applied. Two experiments were conducted to quantify how paclobutrazol application influenced height and bract area of `Freedom' poinsettia. In the first experiment, paclobutrazol was applied at 1 mg·L-1 (ppm) in 118-mL (4.0-fl oz) volumes per pot [(a.i.) 0.12 mg/pot (28,350 mg = 1.0 oz)] as a drench to a new group of plants weekly from the initiation of short days until 1 week before anthesis. Maximum reduction in height and bract area was obtained when paclobutrazol was applied immediately after short days, and the response to paclobutrazol decreased as application time was increasingly delayed toward anthesis. In the second experiment, paclobutrazol was applied weekly after first bract color as either a drench or subapplication at various concentrations. Plant height and bract area were reduced by 23% when 2 mg·L-1 [(a.i.) 0.24 mg/pot) paclobutrazol was applied through subapplication at first color. The effects of paclobutrazol on height and bract area reduction decreased as application time was progressively delayed. Concentrations lower than 1 mg·L-1 had no significant effect on height or bract area reduction, regardless of application time or method. Generally, the reduction in height and bract area was larger when paclobutrazol was applied through subapplication. The combined results from both experiments indicate that paclobutrazol drench applications after flower initiation concomitantly reduce plant height (internode extension) and bract area. Therefore, drench applications should be delayed as long as possible to limit reduction in bract size.

scholarly journals Effects of Paclobutrazol Drench Application Date on Poinsettia Height and Flowering

2001 ◽  
Vol 11 (4) ◽  
pp. 557-560 ◽  
Author(s):  
James E. Faust ◽  
Pamela C. Korczynski ◽  
Robert Klein
Keyword(s):  
Plant Height ◽  
Stem Elongation ◽  
Internode Length ◽  
Euphorbia Pulcherrima ◽  
Late Season ◽  
Area Reduction ◽  
Length Measurements ◽  
Application Date ◽  
Long Term Impact

Experiments were conducted to evaluate the effects of paclobutrazol drenches on poinsettia (Euphorbia pulcherrima) `Freedom Red' height and flowering. In 1997 and 1998, paclobutrazol drenches [(a.i.) 0.118 mg/container; (28,350 mg = 1.0 oz)] were applied to poinsettias grown under natural photoperiods on four dates from 1 Oct. to 2 Nov. On plants receiving the paclobutrazol drench application during the second week in October, bract area was reduced by 15% and 12% compared with that of the control in 1997 and 1998, respectively; however, the bract area reduction was commercially acceptable. Anthesis date was not significantly affected during either year. Plant height and internode length measurements indicate that paclobutrazol drench applications had both a rapid and a long-term impact on poinsettia stem elongation. Paclobutrazol drenches applied in late October or early November are an effective tool for controlling late-season stem elongation of `Freedom Red' poinsettias grown under natural photoperiods. These late-season applications have the least risk for negatively affecting bract size while still reducing stem elongation in the last few weeks of the crop. Chemical names used: (±)-(R*,R*)-b-[(chlorophenyl)methyl]-a-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

scholarly journals Quantification of Temperature Effects on Stem Elongation in Poinsettia

1991 ◽  
Vol 116 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Robert D. Berghage ◽  
Royal D. Heins
Keyword(s):  
Stem Elongation ◽  
Shoot Elongation ◽  
Shoot Length ◽  
Flower Initiation ◽  
Euphorbia Pulcherrima ◽  
Lateral Shoot ◽  
Richards Function ◽  
The Mean ◽  
The Difference ◽  
Short Days

Elongation characteristics of each internode on a lateral shoot of poinsettia (Euphorbia pulcherrima Klotz) `Annette Hegg Dark Red' were determined from pinching through anthesis for plants grown with 36 day/night temperature (DT/NT) combinations between 16 and 30C. The Richards function was used to describe the elongation of each internode. The first internode developing on a lateral shoot was longer and matured faster than subsequent internodes. The length of the first internode was a function of the difference between day and night temperatures (DIF = DT - NT). Subsequent internodes elongated uniformly in the absence of flower initiation. In the absence of flower initiation, the length of an internode, after the first, was a function of DIF. Internodes were shorter as proximity to the inflorescence increased. Internode length after the start of short days was a function of DIF and the visible bud index where visible bud index = [(days from pinching to the day an internode began to elongate - days from pinching to the day of the start of flower initiation)/the number of days from pinching to visible bud]. A poinsettia lateral shoot elongation model was developed based on the derived functions for internode elongation. The model predicted lateral shoot length within one standard deviation of the mean for plants grown in a separate validation study with 16 combinations of DT/NT. The model allows the prediction of lateral shoot length on any day from pinching through anthesis based on temperature, the number of nodes on the lateral shoot, the time each internode on the lateral shoot began elongating, and the visible bud index at the start of elongation of each node.

scholarly journals Controlled Water Deficit as an Alternative to Plant Growth Retardants for Regulation of Poinsettia Stem Elongation

HortScience ◽  
2015 ◽  
Vol 50 (4) ◽  
pp. 565-569 ◽  
Author(s):  
Peter Alem ◽  
Paul A. Thomas ◽  
Marc W. van Iersel
Keyword(s):  
Drought Stress ◽  
Plant Growth ◽  
Plant Height ◽  
Water Deficit ◽  
Stem Elongation ◽  
Alternative Methods ◽  
Growth Retardants ◽  
Target Height ◽  
Height Control ◽  
Plant Growth Retardants

Production of poinsettias (Euphorbia pulcherrima) often involves intensive use of plant growth retardants (PGRs) to regulate height. Height control is necessary for visual appeal and postharvest handling. Since PGRs do not always provide consistent height control and can have unwanted side effects, there is interest in alternative methods of height control. Since turgor potential drives cell expansion, and thus stem elongation, drought stress has potential for regulating plant height. Through soil moisture sensor-controlled irrigation, the severity of drought stress can be both monitored and controlled. The objective of our study was to compare poinsettia ‘Classic Red’ height control using PGRs (spray, mixture of daminozide and chlormequat at 1000 mg·L−1 each and drench, 0.25 mg·L−1 paclobutrazol) with the use of controlled water deficit (WD). Graphical tracking of plant height, using a final target height of 43.5 cm, was used to determine when to apply PGR or controlled WD. In the WD treatment, substrate volumetric water content (θ) was reduced from 0.40 to 0.20 m3·m−3 when actual height exceeded the expected height. PGR applications (spray or drench) reduced poinsettia height to 39 cm, below the final target level of 43.5 cm. WD resulted in a height of 44.5 cm, closest to the target height, while control plants were taller (49.4 cm). There was no effect of PGR drenches or WD on bract size, while spraying PGR reduced bract size by ≈ 40%. Bract chroma was unaffected by WD or PGR treatments. There was no difference in shoot dry weight between PGR- and WD-treated plants. Lateral growth was reduced by the PGR treatments, but not by WD. These results indicate that controlled WD can be used to regulate poinsettia height.

HEIGHT CONTROL OF POT CHRYSANTHEMUMS WITH PRE- AND POST-PLANT TREATMENTS OF DAMINOZIDE AND UNICONAZOLE

1990 ◽  
Vol 70 (3) ◽  
pp. 925-930 ◽  
Author(s):  
PETER R. HICKLENTON
Keyword(s):  
Plant Height ◽  
Foliar Spray ◽  
Dry Weight ◽  
Chrysanthemum Morifolium ◽  
Growth Retardants ◽  
Dendranthema Grandiflora ◽  
Height Control ◽  
Shoot Dry Weight ◽  
Butanedioic Acid ◽  
Higher Doses

This study investigated the effects of growth retardants uniconazole [(E) - (p-chlorohenyl) -4, 4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol] and daminozide (butanedioic acid mono 2,2-dimethylhydrazide) on three chrysanthemum (Dendranthema grandiflora Tzvelev.) cultivars. Uniconazole applied as a soil drench (0.02 mg a.i. pot−1) or foliar spray (0.014 mg a.i. pot−1) 10 d after removal of the shoot tip reduced plant height at harvest in cultivars Deep Luv, Tip and Tara. Higher doses of uniconazole resulted in further plant height reduction in Tip and Tara but not in Deep Luv. Daminozide spray (14 mg a.i. pot) and uniconazole spray (0.028 or 0.056 mg a.i. pot−1) produced plants of similar height. Pre-plant dips of both growth retardants were less effective than sprays or drenches in controlling height. Flower area and flower dry weight were reduced with uniconazole drench and spray, and daminozide spray in each cultivar. Shoot dry weight was similarly affected in Tip and Tara but not in Deep Luv. Flowering was delayed in each cultivar by post-plant treatments of uniconazole drench and spray and by daminozide spray (0.08, 0.014 and 14 mg a.i. pot−1, respectively), and by daminozide and uniconazole pre-plant dips (5.0 mg L−1 and 4000 mg L−1, respectively).Key words: Sumagic, XE-1019, B-Nine, Alar, Chrysanthemum × morifolium, Dendanthema grandiflora

scholarly journals Effects of Pinching, Number of Cuttings per Pot, and Plant Growth Regulators on Height Control of Purple Firespike

2015 ◽  
Vol 25 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Amir Rezazadeh ◽  
Richard L. Harkess
Keyword(s):  
Plant Growth ◽  
Leaf Area ◽  
Plant Height ◽  
Plant Growth Regulators ◽  
Growth Regulators ◽  
Stem Elongation ◽  
Dry Weight ◽  
Maximum Height ◽  
Height Control ◽  
Leaf Dry Weight

Purple firespike (Odontonema callistachyum), native to Central America, has potential for use as a new flowering potted plant. The effects of number of pinches (zero, one, or two) and number of cuttings (one, two, or three) per 6-inch pot were evaluated on the control of plant height. Plant height was suppressed as the pinch number increased. The greatest reduction was recorded with one cutting per pot and two pinches. The maximum number of branches per pot was recorded with two pinches and three cuttings per pot. In a second experiment, plant growth regulators (PGR) were also tested for efficacy of height control; 2 weeks after pinching, foliar sprays of paclobutrazol, flurprimidol, daminozide, chlormequat, and a tank-mix of daminozide + chlormequat or media drenches of paclobutrazol, uniconazole, or flurprimidol were applied. Plant height, leaf area, and leaf dry weight were recorded at 3, 6, and 9 weeks after PGR application. Maximum height control was obtained with uniconazole drench at 8 ppm, resulting in plants 22 cm tall, 61% shorter than the untreated control (56 cm); however, it resulted in severe leaf distortion. Plant height was 56% and 46% shorter than the control using drenches of paclobutrazol at 30 ppm and flurprimidol at 15 ppm, respectively. Daminozide spray at 2000 ppm and tank-mix of daminozide + chlormequat at 4500/1500 ppm suppressed stem elongation by 20.3% and 19%, respectively. Plants treated with paclobutrazol drench at 30 ppm reduced leaf area and leaf dry weight compared with other PGRs. Chlormequat spray at tested concentrations was ineffective for controlling firespike plant growth. The most attractive potted plants were produced using a drench application of paclobutrazol at 10 or 15 ppm.

scholarly journals Early Flurprimidol Drench Applications Suppress Final Height of Four Poinsettia Cultivars

2011 ◽  
Vol 21 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Christopher J. Currey ◽  
Roberto G. Lopez
Keyword(s):  
Stem Elongation ◽  
Final Height ◽  
Foliar Spray ◽  
Euphorbia Pulcherrima ◽  
Growth Retardants ◽  
Height Ratio ◽  
Chlormequat Chloride ◽  
Area Index ◽  
Aesthetic Appearance ◽  
Plant Growth Retardants

Plant growth retardants (PGRs) are commonly applied to control poinsettia (Euphorbia pulcherrima) stem elongation to meet a target final height. Two weeks after pinching, 4-fl·oz substrate drenches containing 0.0, 0.05, 0.10, 0.15, 0.20, or 0.25 mg·L−1 flurprimidol were applied to high-vigor ‘Orion’ and low-vigor ‘Polly Pink’ poinsettia (Expt. I); while drenches containing 0.0, 0.05, 0.10, or 0.15 mg·L−1 flurprimidol or a foliar spray containing 1250 mg·L−1 daminozide and 750 mg·L−1 chlormequat chloride were applied to high-vigor ‘Classic Red’ and low-vigor ‘Freedom Salmon’ poinsettia (Expt. II). Final height of ‘Orion’ and ‘Polly's Pink’ poinsettia was suppressed by 12% to 25% and 13% to 30%, respectively, as flurprimidol concentration increased from 0.05 to 0.25 mg·L−1. Final height of ‘Classic Red’ and ‘Freedom Salmon’ was suppressed by 11% to 30% and 10% to 19%, respectively, as flurprimidol concentration increased from 0.05 to 0.15 mg·L−1. Although the daminozide and chlormequat chloride spray had no significant effect on bract area index compared with untreated plants, bract area index was smaller for all plants treated with flurprimidol. However, the bract area to height ratio of all cultivars was not impacted by any PGR application, indicating aesthetic appearance was not negatively affected with smaller bract area. Time to anthesis was delayed by up to 4 days when 0.10 mg·L−1 was applied to ‘Classic Red’, although no significant delays were observed for the remaining cultivars. Based on these results, flurprimidol may be applied as an early drench to suppress height of poinsettia without adversely impacting finished plant quality or crop timing.

scholarly journals POINSETTIA DEVELOPMENTAL AND POST-PRODUCTION RESPONSES TO GROWTH RETARDANTS AND IRRADIANCE

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1071g-1071
Author(s):  
Douglas A. Bailey ◽  
William B. Miller
Keyword(s):  
Plant Height ◽  
Growth Retardant ◽  
Production Performance ◽  
Euphorbia Pulcherrima ◽  
Growth Retardants ◽  
Water Control ◽  
Chlormequat Chloride ◽  
Leaf Drop ◽  
Post Production ◽  
Lower Irradiance

Plants of Euphorbia pulcherrima Wind. `Glory' were grown under 13.4, 8.5, or 4.0 mol·m-2·day-1 and sprayed with water (control); 2500 mg·liter-1 daminozide + 1500 mg·liter-1 chlormequat chloride (D+C); 62.5 mg·liter-1 paclobutrazol; or 4, 8, 12 or 16 mg·liter-1 uniconazole to ascertain plant developmental and pest-production responses to the treatment combinations. Days to anthesis increased as irradiance was decreased. Anthesis was delayed by the D+C treatment, while other growth retardant (GR) treatments had no effect on anthesis. Irradiance did not affect plant height at anthesis, but all GR treatments decreased height over control plants. Bract display and bract canopy display diameters declined as irradiance was decreased. Growth retardants did not affect individual bract display diameters, but all GR treatments except paclobutrazol reduced bract canopy display diameter. Plants grown under lower irradiance had fewer axillary buds develop, fewer bract displays per plant, and fewer cyathia per bract display. Cyathia abscission during a 30 day post-anthesis evaluation was not affected by treatment; however, plant leaf drop was linearly proportional to irradiance. All GR treatments increased leaf drop over controls, and the D+C treated plants had the highest leaf loss. Results indicate the irradiance and GR treatments during production can affect poinsettia crop timing, plant quality at maturity, and subsequent post-production performance.

scholarly journals Effectiveness of Plant Growth Regulators under Photoselective Greenhouse Covers

2000 ◽  
Vol 125 (6) ◽  
pp. 673-678 ◽  
Author(s):  
Anuradha Tatineni ◽  
Nihal C. Rajapakse ◽  
R. Thomas Fernandez ◽  
James R. Rieck
Keyword(s):  
Plant Height ◽  
Control Mechanism ◽  
Chrysanthemum Morifolium ◽  
Photon Flux ◽  
Gibberellin Biosynthesis ◽  
Growth Retardants ◽  
Water Control ◽  
Height Control ◽  
Height Reduction ◽  
Height Increase

Responses to selected chemical growth retardants (daminozide, paclobutrazol, and prohexadione-Ca) and GA1 and GA3 under photoselective greenhouse covers with various phytochrome photoequilibrium estimates (φe) were evaluated using `Bright Golden Anne' chrysanthemum [Dendranthema ×grandiflora Kitam. (syn. Chrysanthemum morifolium Ramat.)] as the model plant to better understand the height control mechanism by far red (FR) light depleted environments. Plant height linearly decreased as φe increased from 0.72 to 0.83. The rate of height decrease of daminozide treated plants was less than that of water (control) or GA3-treated plants. The rate of height reduction was not different between control and GA3-treated plants among chambers with various φe. Both paclobutrazol and prohexadione-Ca reduced plant height regardless of φe, but the height reduction by paclobutrazol was more than that by prohexadioneCa. The combination of paclobutrazol and prohexadione-Ca reduced plant height more than either alone. GA1 reversed the height reduction caused by paclobutrazol and prohexadione-Ca regardless of φe, but the height increase by GA1 was more when it was applied with prohexadione-Ca than when applied alone. Results show that photoselective covers with high φe were effective in controlling height of chrysanthemums without chemical growth retardants. The linear relationship between plant height and φe suggests that effectiveness of photoselective covers increased as φe increased. The photosynthetic photon flux (PPF) transmission of photoselective covers decreased as the φe increased because of the increasing dye concentration. Identifying photoselective covers that effectively filter out FR light from sunlight and reduce plant height while minimizing the PPF reduction is critical for commercial success of photoselective covers. Gibberellins are, at least partially, involved in height control by photoselective covers. Photoselective greenhouse covers did not reduce responsiveness to gibberellins, and it appears that the mechanism may be to suppress gibberellin biosynthesis. Results also suggest that increased metabolism of GA1 to GA8 was not the mechanism of height control by photoselective covers. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) [daminozide]; (±)-(R*,R*)-b-((4-chlorophenyl)methyl)-a-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol [paclobutrazol]; 3,5-dioxo-4-(1-oxopropyl)cyclohexanecarboxylic acid [prohexadione-Ca]; gibberellic acid [GA].

scholarly journals Effects of GA3 on Poinsettia Over-retarded with Paclobutrazol

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 822D-822
Author(s):  
Amy D. McDaniel* ◽  
Yin-Tung Wang
Keyword(s):  
Stem Elongation ◽  
Foliar Spray ◽  
Euphorbia Pulcherrima ◽  
Excellent Quality ◽  
Short Days

A study was initiated to determine the effect of GA3 as a counter measure to restore the growth of over-retarded poinsettia. Euphorbia pulcherrima `Sonora Red' plants were treated once foliarly with paclobutrazol at 40 or 80 mg·L-1 one week following pinching. Four weeks later, plants receiving the 80 mg·L-1 rate were treated once foliarly with GA3 at 0, 10, 20, 30 or 40 mg·L-1. The effect of GA3 was visible within 3 days of application. GA3 between 10 and 40 mg·L-1 caused long internodes, excessive stem elongation, as well as small leaves and bracts, resulting in unmarketable plants. Plants receiving 10 mg·L-1 GA3 were nearly twice the height of the over-retarded plants (31 vs. 17 cm), with increasingly taller plants at higher concentrations, up to 30 mg·L-1. In a second experiment, single-stemed plants were treated with one foliar spray of 50 or 150 mg·L-1 paclobutrazol two weeks following the beginning of short days. After another 3 weeks, the overdosed plants were then foliarly treated once with 0, 3, 5, 10, or 15 mg·L-1 GA3. GA3 at all rates promoted stem elongation and resulted in large bracts and much increased inflorescence diameter. The 15 mg·L-1 GA3 rate resulted in undesirable long internodes on the upper stem. Plants that received 3, 5, or 10 mg·L-1 GA3 were of excellent quality, with their heights and inflorescence sizes similar to those of plants receiving 50 mg·L-1 paclobutrazol (26 cm). Parallel experiments using `Burgundy Cortez' had similar results.

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