Effects of Paclobutrazol Drench Application Date on Poinsettia Height and Flowering

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).

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Using Paclobutrazol to Control Height of Poinsettia `Freedom'

HortTechnology ◽

10.21273/horttech.12.2.232 ◽

2002 ◽

Vol 12 (2) ◽

pp. 232-236 ◽

Cited By ~ 2

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.

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294 Quantifying the Effect of Application Date of Paclobutrazol Drenches on Poinsettia Stem Elongation and Bract Size

HortScience ◽

10.21273/hortsci.34.3.493b ◽

1999 ◽

Vol 34 (3) ◽

pp. 493B-493

Author(s):

Pamela Korczynski ◽

James E. Faust ◽

Robert Klein

Keyword(s):

Plant Height ◽

Stem Elongation ◽

Internode Length ◽

Node Number ◽

Application Date

Paclobutrazol drenches (1 ppm, 118.4 mL per pot) were applied to Poinsettia `Freedom' Red' on 1, 11, 21, and 31 Oct. in 1997 and 1998. Plant heights were recorded twice weekly throughout the experiment, and internode length and bract area were measured at harvest. The total bract area of the three true bracts and the top three transitional bracts was reduced by 5.8%, 13.6%, 4.2%, and 2.3% for the 1, 11, 21, and 31 Oct. application dates, respectively; however, all plants were highly marketable. At the time of each drench application, the most newly unfolded leaf was marked. The internode lengths for the three internodes below this leaf and the internodes that developed after the drench application were typically between 5 and 10 mm in length, while the internode lengths of the control plants were typically 10 to 25 mm, depending on node number. Plant height increased 62, 51, 47 and 19 mm following application on the 1, 11, 21, and 31 Oct. application dates, respectively. The 1, 11, 21, and 31 Oct. drench applications reduced total stem elongation from 1 Oct. to anthesis by 64%, 49%, 28%, and 15%, respectively. Paclobutrazol drenches did not affect time to anthesis.

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Study on the Regulatory Effects of GA3 on Soybean Internode Elongation

Plants ◽

10.3390/plants10081737 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1737

Author(s):

Fuxin Shan ◽

Rui Zhang ◽

Jin Zhang ◽

Chang Wang ◽

Xiaochen Lyu ◽

...

Keyword(s):

Plant Height ◽

Apical Meristem ◽

Stem Elongation ◽

Internode Length ◽

Internode Elongation ◽

Primary Xylem ◽

Dwarf Cultivar ◽

Leaves And Roots ◽

Soybean Plants ◽

Regulatory Effects

Excessive plant height is an important factor that can lead to lodging, which is closely related to soybean yield. Gibberellins are widely used as plant growth regulators in agricultural production. Gibberellic acid (GA3), one of the most effective active gibberellins, has been used to regulate plant height and increase yields. The mechanism through which GA3 regulates internode elongation has been extensively investigated. In 2019 and 2020, we applied GA3 to the stems, leaves, and roots of two soybean cultivars, Heinong 48 (a high-stalk cultivar) and Henong 60 (a dwarf cultivar), and GA3 was also applied to plants whose apical meristem was removed or to girded plants to compare the internode length and stem GA3 content of soybean plants under different treatments. These results suggested that the application of GA3 to the stems, leaves, and roots of soybean increased the internode length and GA3 content in the stems. Application of GA3 decreased the proportion of the pith in the soybean stems and primary xylem while increasing the proportion of secondary xylem. The apical meristem is an important site of GA3 synthesis in soybean stems and is involved in the regulation of stem elongation. GA3 was shown to be transported acropetally through the xylem and laterally between the xylem and phloem in soybean stems. We conclude that the GA3 level in stems is an important factor affecting internode elongation.

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Crisis Phones - Suicide Prevention Versus Suggestion/Contagion Effects

Crisis ◽

10.1027/0227-5910/a000313 ◽

2015 ◽

Vol 36 (3) ◽

pp. 220-224 ◽

Cited By ~ 3

Author(s):

Steven Stack

Keyword(s):

Suicide Prevention ◽

Contagion Effects ◽

Long Term Impact

Abstract. Background: There has been no systematic work on the short- or long-term impact of the installation of crisis phones on suicides from bridges. The present study addresses this issue. Method: Data refer to 219 suicides from 1954 through 2013 on the Skyway Bridge in St. Petersburg, Florida. Six crisis phones with signs were installed in July 1999. Results: In the first decade after installation, the phones were used by 27 suicidal persons and credited with preventing 26 or 2.6 suicides a year. However, the net suicide count increased from 48 in the 13 years before installation of phones to 106 the following 13 years or by 4.5 additional suicides/year (t =3.512, p < .001). Conclusion: Although the phones prevented some suicides, there was a net increase after installation. The findings are interpreted with reference to suggestion/contagion effects including the emergence of a controversial bridge suicide blog.

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