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Using Plant Growth Regulators to Improve Plant Architecture in Herbaceous Perennial Plants

Mara GrossmanM.S. student

Department of HorticultureVirginia Tech

IntroductionCommercial production of ornamental plants

Floriculture crops 4.13 billion dollars in 2010

Potted herbaceous perennials 553 million dollars(USDA, 2011)

Liners and plug seedlings over 448 million dollars (USDA, 2009)

Southwest Perennials Inc., Dallas Texas, specializes in herb and perennial liner production

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IntroductionProduction challenges for growers

Control plant growth with both physical controls and chemical controls

Plant growth regulators (PGRs) control plant height, branching and flowering.

Van Wingerden International, Inc. located in Asheville, N.C.

IntroductionUsing PGRs

Plants respond in different ways to PGRs depending on species, cultivar, growing conditions, and the PGR utilized (Gent and McAvoy,

2000)

Treating liners prior to transplant can have significant benefits for growers.

Reduced time of application and reduced chemical cost resulting in a more cost effective method of treating plants (Whitman and

Runkle, 2003)

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IntroductionControlling Branching with PGRs

Release apical dominance Increase branching and improve

quality Substitute for pinching Pinching labor intensive Pinching delays growth and

bloom

Goal is to improve plant architecture

Synthetic cytokinin

Cytokinins promote cell division in tissue culture (Miller et. al. 1955)

Application of exogenous cytokinins in many species increases the ratio of cytokinin to auxin in the plant, disrupting apical dominance which controls branching patterns and plant form, and promotes lateral bud out growth (Cline, 1991)

BA has been shown to increase number of branches in herbaceous perennials (Farris et al., 2009; Keever, 1994; Latimer and Freeborn, 2008; Martin and Singletary, 1999)

Configure, Fine Americas Inc., labeled for use on annual and perennial flowering and foliage plants and tropical plants

IntroductionBenzyladenine (BA)

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Disrupts cell wall integrity Previously labeled as Atrimmec or Atrinal Primarily has been used to reduce shoot elongation and

increase branching in woody plants (Banko and Stefani, 1995; Bell et al., 1997; Bruner et al., 2002; Sachs et al., 1975)

Little research on herbaceous plants Increased branching on Zinnia, Helianthus, Chrysanthemum,

Boston fern, Kalanchoe, and Gaillardia (Arzee et al., 1977; Carter et al., 1996; Latimer and Freeborn, 2010; Nightingale et al., 1985)

Augeo, OHP, Inc., Mainland PA, labeled for use on bedding plants, herbaceous plants, perennials, woody ornamentals and trees

IntroductionDikegulac Sodium

IntroductionRationale and significance

By testing PGRs and their effect on herbaceous perennials we will:

Improve plant production methods

Strengthen the floriculture industry

Expand our knowledge of plant growth

Improve our ability to make effective PGR recommendations to growers

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To study the effects of branching agents on herbaceous perennial crops during liner production and on finished plants

To improve plant architecture at an earlier stage of production

IntroductionResearch Objectives

Outline

• Introduction

• Exp. 1: Benzyladenine (BA)

• Exp. 2: BA in combination with IBA

• Exp. 3: Dikegulac sodium (DS)

• Exp. 4: Single vs. Multiple Applications, BA and DS

• Conclusions

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Experiment One ObjectiveEvaluate the effects of BA on the shoot and root growth of 11 herbaceous perennials during liner production and grow out of finished plants

Exp. 1: Methods and Materials Plants Studied

Agastache ‘Purple Haze’

Aster ‘Professor Kippenburg’

Campanula ‘Cherry Bells’

Cosmos atrosanguineus

Gaura lindheimeri ‘Siskiyou Pink’

Lavandula x intermedia 'Provence’

Leucanthemum x superbum 'Snowcap’

Rosmarinus officinalis 'Hill Hardy'

Salvia nemorosa ‘May Night’

Verbena bonariensis ‘Lollipop’

Veronica ‘Goodness Grows’

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Exp. 1: Methods and Materials

Exp. 1: Methods and MaterialsBA Treatments

After removal from mist BA treatments were applied as foliar sprays:

•0 mg·L-1 (control)•1 application of 300 mg·L-1

•2 applications of 300 mg·L-1

(1st application after removal from mist,2nd application two weeks after 1st application)•1 application of 600 mg·L-1

In all experiments:completely randomized design for each speciesData analyzed by ANOVA

Agastache at time of treatment

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Exp. 1: Methods and MaterialsTreatment Application

Foliar sprays at a volume of 210 ml per m2

Sprays applied evenly to square meter plots

Not actively transported in the plant

Exp. 1:Methods and MaterialsData Collection

Data collected at 0, 2, and 3-4 weeks after treatment (WAT)

Plants were then transplanted into quart size pots (1.1 liters)

Grown out for an additional 4 weeks

Data collected at 4 weeks after transplant.

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Measurements included:

•Plant height•Average plant width•Lateral branches and leaders or basal branches

•Phytotoxicity•Flowering •Root and shoot dry weights•Root volume and surface area (five species)

Exp. 1:Methods and MaterialsData Collection

Exp. 1: Results and DiscussionBranching effects on finished liners

Nine of eleven crops evaluated showed an increase in branching at time of transplant.

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Agastache 3 WAT

40% increase in lateral branches

300x2Untreated 300x1 600x1

Agastache ‘Purple Haze’ at 3 WAT11.6b

16.1a17.6a 16.8a

0

5

10

15

20

Num

ber

of B

ranc

hes

Agastache Lateral Branchesat 3 WAT

Control (0) 300x1 300x2 600x1

Means followed by the same letter are not significantly different at the p<.05 level, n=6.

Gaura 4 WAT

Untreated 300x1 600x1300x2

Gaura ‘Siskyou Pink’

All BA treatments significantly increased lateral branches and leaders at 4 WAT

7.5b

9.2a 9.3a8.5a

0

2

4

6

8

10

Num

ber

of B

ranc

hes

Gaura Lateral Branches at 4WAT

Control (0) 300x1 300x2 600x1


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Lavandula 4 WAT

Increased branches at higher rates at 4WAT

Increased leaders at all rates of BA treatment

300x2Untreated 300 x1 600 x1

Lavandula x intermedia ‘Provence’

13.4c 14.3bc 15.6ab 16.9a

0

5

10

15

20

Num

ber

of B

ranc

hes

Lavandula Lateral Branchesat 4 WAT

Control (0) 300x1 300x2 600x1


Leucanthemum 4 WAT

Basal branches doubled at 4WAT

Untreated Control


1.3a

2.5b 2.9b 2.5b

0

1

2

3

4

Num

ber

of B

ranc

hes

Leucanthemum Basal Branchesat 4 WAT

Control (0) 300x1 300x2 600x1

Leucanthemum x superbum ‘Snowcap’Means followed by the same letter are not significantly different at the p<.05 level, n=6.

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Untreated 300x1 300x2 600x1

Rosemary 4 WAT

Rosmarinus 'Hill Hardy'

Lateral branches and leaders were increased with all treatments

16.9c20.4b

24.0a 24.3a

0

10

20

30

Num

ber

of B

ranc

hes

Rosemary Lateral Branchesat 4 WAT

Control (0) 300x1 300x2 600x1


Salvia 4 WAT

40% increase in basal branches with one or two applications of 300 mg·L-1

Salvia ‘May Night’

3b

4.2a3.8a

3b

0

1

2

3

4

5

Num

ber

of B

ranc

hes

Salvia Basal Branches at 4 WAT

Control (0) 300x1 300x2 600x1



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Verbena 4 WAT

Number of lateral branches was significantly increased at higher rates


Verbena bonariensis ‘Lollipop’

2.2c

3.5bc

5.3a

3.8ab

0

1

2

3

4

5

6

Num

ber

of B

ranc

hes

Verbena Lateral Branches at 4 WAT

Control (0) 300x1 300x2 600x1


Veronica 3 WAT


Veronica spicata ‘Goodness Grows’

Lateral branching increased 100-200%

Increased leaders with 600x1

2.3c

6b

9.3a

5b

0

2

4

6

8

10

Num

ber

of B

ranc

hes

Veronica Lateral Branches at 3 WAT

Control (0) 300x1 300x2 600x1


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Other Results Campanula: unresponsive to treatment with BA

Aster: phytotoxicity: tip burn

Cosmos: phytotoxicity: distorted leaves

Aster ‘Professor Anton Kippenburg’

Untreated 300x2


Exp. 1: Results and Discussion:Branching Effects After Transplant

Increased branching effects were no longer evident in most plants after growing out for four additional weeks (8 WAT)



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Effects of BA on branching after transplant, 8 weeks after treatment

Gaura 80% increase

Lavandula 85% increase (only with two apps. of 300 mg· L-1)

600x1300x2300x1Untreated


Lavandula x intermedia ‘Provence’

Gaura ‘Siskyou Pink’

Exp. 1: Results and Discussion:Effects on Roots


Leucanthemum x superbum ‘Snowcap’

Four of eleven crops evaluated showed a decrease in root dry weight at time of transplant.

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Effects of BA on root dry weight at time of transplant, 3 or 4 WAT

Agastache Reduced 40%

Cosmos Reduced 40%

Lavandula Reduced only with two applications of 300 mg· L-1

Leucanthemum Reduced 25-40%

Rosemary Increased

Results and Discussion:Effects on Roots

Root Measurements Media was washed off roots by hand

Then roots were scanned using WinRhizo (Regent Instruments Inc., Quebec, Canada) to analyze root surface area and volume

Roots were dried at 66°C (150°F) for 48 hours then weighed

Root surface area and volume were highly correlated with root dry weight

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Root MeasurementsCorrelation Root Dry Weight to Root Surface Area and Volume

Leucanthemum root surface area to root dry weight, bivariate fit

r² = 0.77, p<0.0001

Leucanthemum root volume to root dry weight, bivariate fit

r² = 0.78, p<0.0001

Root Dry Weight to Root Surface Area

Root Dry Weight to Root Volume

r2 p value r2 p value

Agastache 0.87 <0.0001 0.91 <0.0001Gaura 0.73 <0.0001 0.77 <0.0001

Lavandula 0.88 <0.0001 0.95 <0.0001Leucanthemum 0.77 <0.0001 0.78 <0.0001

Salvia 0.84 <0.0001 0.88 <0.0001

Root Measurements

Correlation Root Dry Weight to Root Surface Area and Volume

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Leucanthemum finished plants

Reduction in root dry weight did not affect appearance of finished plants (4 weeks after transplant)

Leucanthemum x superbum ‘Snowcap’

Untreated 600x1300x2300x1


Root Reduction in Agastache

Root dry weight reduced 40% at 3WAT

0.98a 0.82b0.58c 0.58c

0

0.5

1

1.5

Roo

t Dry

Wei

ght (

g)

Agastache Root Dry Weight (g)at 3 WAT

Control (0) 300x1 300x2 600x1


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Agastache at 8 WAT

Reduction in root dry weight of liners did not affect appearance of finished plants 4 weeks after transplant


Agastache ‘Purple Haze’

Exp. 1 Conclusions

BA is safe for use on liners after removal from mist

BA can improve branching during liner production

Decreases in root dry weight did not affect finished plant appearance

Root surface area and root volume are highly correlated with root dry weight

BA has a short term effect on most plants

This indicates a value in reapplying BA to responsive plants shortly after transplanting liners to the finished containers

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Outline

• Introduction





• Conclusions

Exp. 2: BA in combination with IBAObjective: To evaluate the effect of BA, IBA and the combination of the

two on the branching and root growth of herbaceous perennial plants during liner production and grow out of finished plants

Plants studied: Agastache ‘Tutti Frutti' Lavandula x intermedia ‘Provence’ Leucanthemum x superbum 'Snowcap' Rosmarinus ‘Hill Hardy’

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Indole-3-butyric acid (IBA),an auxin

Active ingredient in many rooting compounds

Commonly used to encourage rooting during propagation (Dole and Wilkins, 2005)

Exp. 2: BA in combination with IBA

0 mg·L-1 (control)

500 mg·L-1 BA (Configure, Fine Americas, Inc.)

1000 mg·L-1 IBA (Hortus IBA Water Soluble Salts 20% IBA , Hortus USA)

500 mg·L-1 BA plus 1000 mg·L-1 IBA

URCs

Treatments applied 1 day after removal from mist

Data collected on finished liners and finished plants

Exp. 2: BA in combination with IBA

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Exp. 2: Results Root Dry Weight of Liners

Root Dry Weight (g) 2‐3 WAT

Treatment mg∙L‐1 Agastache Lavandula Leucanthemum Rosmarinus

Control 0 0.076ab 0.018 0.131a 0.054

BA 500 0.052bc 0.023 0.102b 0.043

IBA 1000 0.078a 0.025 0.145a 0.047

BA + IBA 500/1000 0.044c 0.018 0.096b 0.041

Rate Effect 0.0224 0.1088 0.0051 0.1459

LSD 0.025 0.007 0.029 0.012


Root Dry Weight of Finished Plants

Root Dry Weight (g) Finished Plants

Treatment mg∙L‐1 Agastache Lavandula Leucanthemum Rosmarinus

Control 0 0.342 .194ab 1.13b 0.241

BA 500 0.315 .220a 1.01b 0.166

IBA 1000 0.351 .183b 1.36a 0.188

BA + IBA 500/1000 0.273 .147c 0.977b 0.169

Rate Effect 0.5366 0.0005 0.0014 0.059

LSD 0.11834 0.03067 0.19189 0.06003


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AgastacheBA+IBA treatment

Reduced height, root weight, slight phyto in liners

Reduced flower height in finished plants

BA treatment

increased branches in finished plants

no effect on root weight

BA + IBABA IBAControl

5 WAT


2 WAT

LavandulaBA+IBA treatment Reduced height, shoot weight of

liners and finished plants Reduced root weight of finished

plants

BA treatment Increased leaders of liners (NS) increase branches

of finished plants No effect on root weight

All treatments Slight phyto on liners Slight tip necrosis,

no longer evident after grow out

BA+ IBABAIBAControl

3 WAT

7 WAT

BA+ IBABA IBAControl

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Leucanthemum No effect on branching

Root dry weight reduced in liners with both BA and BA+IBA treatment

Reduced root dry weight did not affect finished plants


2 WAT

7 WAT


Rosmarinus

BA increased branches on liners, reduced branches on finished plants

Slight phyto on liners, tip damage and leaf curling

Phyto no longer evident after grow out

BA + IBABAIBAControl

3 WAT 7 WAT


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Exp. 2 Conclusions

The addition of IBA to BA did not mitigate BA’s negative rooting effects

IBA or IBA in combination with BA did not increase branching

Outline

• Introduction





• Conclusions

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Evaluate the effects dikegulac sodium on the branching of herbaceous perennial plants during liner production and grow out of finished plants

Six herbaceous perennials studied:• Aster ‘Professor Anton Kippenburg’

• Campanula punctata ‘Cherry Bells’

• Cosmos astrosanguineus

• Rosmarinus ‘Hill Hardy’

• Verbena bonariensis ‘Lollipop’

• Veronica ‘Goodness Grows’

Exp. 3: Objective


URCs into 72 size flats

Rooted under mist until roots visible on all 4 sides of plug

Augeo (18% dikegulac sodium) applied as a foliar spray at four concentrations: 0 mg·L-1

400 mg·L-1

800 mg·L-1

1600 mg·L-1

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Measurements included: height, width, branches, leaders, phytotoxicity, flowering, root and shoot dry weights.

Data were collected at 0, 2, and 3-4 weeks after treatment (WAT).

Plants were then transplanted into quart (1.1 liter) pots and grown out for an additional 4 weeks.


Exp. 3: Results and Discussion

All six crops evaluated showed an increase in branching at time of transplant.

Four of the six crops evaluated showed an increase in branching after growing out for 3-4 weeks.

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Dikegulac sodium on Aster at 3 WAT

DS Concentration mg·L-1

Number of Branches

Number of Leaders

Shoot Dry Wt (g) Height (cm)

0 17.6b 3.4b 0.29ab 11.1ab400 19.8ab 3.1b 0.31a 11.5a800 18.5b 3.6b 0.27b 10.1b

1600 23.3a 4.8a 0.19c 4.8cRate effect 0.033 0.0181 <0.0001 <0.0001

LSD 3.75 1.04 0.035 1.32


Dikegulac sodium on Aster at 3 WAT

Aster 'Professor Anton Kippenberg'

Untreated 1600

• 40 % increase in leaders and 30% increase in branches in plants treated with 1600 mg·L-1

• Significant decrease in shoot weight and height

• No differences in branching after grow out

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Dikegulac sodium on Campanulaat 3 WAT


Number of Branches

Shoot Dry Weight (g) Height (cm)

0 3.6b 0.41 9.8a400 3.0b 0.32 8.6a800 5.0a 0.38 8.8a

1600 3.8ab 0.33 7.0bRate effect 0.0132 0.1437 0.0032

LSD 1.25 0.078 1.51


Dikegulac sodium on Campanulaat 3 WAT

800 mg·L-1 dikegulac sodium increased branching with no effect on shoot or root dry weight

No differences in branching after grow out

800400Untreated 1600

Campanula punctata 'Cherry Bells'

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Dikegulac sodium on Cosmos at 3 WAT

DS Concentration mg·L-

1

Number of Branches

Number of Leaders

Shoot Dry Wt (g) Height (cm)

0 17.6b 3.4b 0.39a 22.3ab400 19.8ab 3.1b 0.35a 23.8a800 18.5b 3.6b 0.35a 20.4b

1600 23.3a 4.8a 0.29b 11.4cRate effect 0.033 0.0181 0.0115 <0.0001

LSD 3.75 1.04 0.056 3.24



1600 mg·L-1 dikegulac sodium increased numbers of branches (30%) and leaders (40%) at 3 WAT.

Florel800400Untreated 1600


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Increased leaders and branches persisted in plants treated with 1600 mg·L-1 dikegulac sodium


Cosmos atrosanguineus finished plants

Dikegulac sodium on Rosmarinusat 4 WAT


Number of Branches

Number of Leaders

Shoot Dry Wt. (g) Height (cm)

0 19.7c 1.6c 0.33a 11.3a400 22.8ab 4.0b 0.3a 11.4a800 24.7a 6.2a 0.33a 12.1a

1600 22.6abc 7.3a 0.25b 9.0bRate effect 0.0164 <0.0001 0.0005 <0.0001

LSD 2.92 1.53 0.049 1.48


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Dikegulac sodium on Rosmarinus at 4 WAT

Dikegulac sodium increased numbers of leaders (150-350%) and branches (20%).



After 4 wk grow out: 800 & 1600 mg·L-1 dikegulac sodium increased numbers of leaders (control 11 vs. treated plants 14-15) and branches (control 46 vs. treated plants 56-64).



Dikegulac sodium on Rosmarinus at 4 WAT

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Dikegulac sodium on Verbena at 3 WAT


Number of Branches

Number of Leaders


0 1.3d 1.0b 0.37a 21.1a400 9.2b 1.1b 0.36a 13.9b800 10.1b 1.4a 0.25b 10.7c

1600 12.2a 1.2ab 0.28b 7.1dRate effect <0.0001 0.042 <.0001 <.0001

LSD 1.12 0.259 0.040 1.84


Dikegulac sodium increased branching: control 1.3 vs. treated plants 9-12 branches.

Dikegulac sodium caused twisting of leaves but plants grew out of symptoms in grow out phase


Verbena bonariensis 'Lollipop'


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After 4 wk grow out, 800 and 1600 mg·L-1 dikegulac sodium increased number of branches (control 28 vs. treated plants 32 – 38).

Slight delay in flowering 800 and 1600 mg·L-1


Verbena bonariensis 'Lollipop'


Dikegulac sodium on Veronica at 4 WAT


Number of Branches

Number of Leaders


0 0.6c 1 10a 8.4a400 8.0b 1.1 7.9b 7.5a800 13.5a 1.1 7.7b 4.0b

1600 7.7b 1.2 6.6c 1.1cRate effect <0.0001 0.6504 <.0001 <.0001

LSD 2.65 0.2515 0.9933 1.2166


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dikegulac sodium increased number of branches (control 0.6 vs treated plants 7.7-13.5)

reduced height and shoot dry weight 800 and 1600 mg·L-1




After 4 wk grow out, all dikegulac sodium treatments increased branching but the 800 and 1600 mg·L-1 treatments caused excessive stunting – plants did not grow out.

Florel spray800400Untreated 1600



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Exp. 3 conclusions

Dikegulac sodium did increase branching in herbaceous perennials during liner production

PGR response varied by species

Phytotoxicity when noted was transient

Some plants showed persistent increases in branching after transplant and grow out.

Outline

• Introduction





• Conclusions

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Exp. 4: ObjectiveEvaluate the effects of timing of applications of BA and dikegulac sodium on quality of plants as liners and finished plants.

Six herbaceous perennials studied:• Sedum spectabile ‘Autumn Joy'

• Gaillardia aristata ‘Gallo Red’

• Phlox paniculata ‘Bright Eyes’

• Nepeta x faassenii ‘Walker’s Low’

• Delosperma ‘Table Mountain’

• Achillea ‘Moonshine’

Exp. 4: Methods and MaterialsDesign: Split Plot, n = 6

Main Plot = Timing PGR applications Liner: single application after removal from mist Post Transplant: single application 5-7 days after transplant Both: applications at liner AND post transplant

Sub-Plot = PGR concentration 0 mg·L-1 dikegulac sodium 400 mg·L-1 dikegulac sodium 800 mg·L-1 dikegulac sodium 1600 mg·L-1 dikegulac sodium 600 mg·L-1 BA 400 mg·L-1 dikegulac sodium + 600 mg·L-1 BA

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Exp. 4: Methods and Materials URCs

Data as finished liners and after transplant and grow out

Measurements included: height, width, branches, leaders, phytotoxicity, flowering, and shoot dry weights.

Achillea at time of liner treatment

Number of branches3 WAT 6 WAT

Application TimeLiner 8.1 28.3cPost Transplant -- z 34.7bBoth 9 y 57.7aApplication time effect 0.0102 <0.0001

PGR Concentration LinerPost

Transplant Both0 mg·L-1 2.8e 22.6 25.0d 21.4c400 mg·L-1 DS 5.7d 33.8 26.9cd 60.5b800 mg·L-1 DS 7.0c 28 36.0bc 57.4b1600 mg·L-1 DS 9.5b 27.6 26.9cd 60.9b600 mg·L-1 BA 12.8a 32.3 49.3a 53.6b400 mg·L-1 DS+ 600 mg·L-1 BA 13.4a 25.8 44.3ab 92.6aTreatment effect <0.0001 0.0695 <0.0001 <0.0001

Application Time * PGR Concentration 0.2458 <0.0001z Not treated at this timey Treated only at liner stage at this time

Sedum Number of Branches


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Height (cm)3 WAT 6 WAT

Application TimeLiner 12.4 26.2aPost Transplant -- z 23.8bBoth 12.5y 24.7bApplication time effect 0.6098 <0.001


Transplant Both0 mg·L-1 13.6a 26.1a 25.1ab 25.4cd400 mg·L-1 DS 13.0abc 27.3a 25.1ab 29.6a800 mg·L-1 DS 13.3ab 26.1a 23.5ab 23.4d1600 mg·L-1 DS 10.1d 22.5b 20.4c 16.0e600 mg·L-1 BA 12.4bc 27.7a 25.9a 28.0ab400 mg·L-1 DS+ 600 mg·L-1 BA 12.3c 27.6a 23.0b 26.0bcTreatment effect <0.0001 0.0021 0.0007 <0.0001


Sedum Height


Shoot Weight (g)3 WAT 6 WAT

Application TimeLiner 0.664 10.0aPost Transplant -- z 7.0cBoth 0.722 y 8.32bApplication time effect 0.0127 <0.0001


Transplant Both0 mg·L-1 0.692bc 10.3 7.91b 10.0ab400 mg·L-1 DS 0.752ab 10.6 6.78cd 10.1ab800 mg·L-1 DS 0.627cd 10.5 6.14d 6.24c1600 mg·L-1 DS 0.583d 8.0 4.80e 3.23d600 mg·L-1 BA 0.780a 10.1 9.02a 10.8a400 mg·L-1 DS+ 600 mg·L-1 BA 0.723ab 10.7 7.13bc 9.47bTreatment effect <0.0001 0.0532 <0.0001 <0.0001


Sedum Shoot Weight


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DS 800x2DS 400x2Untreated DS 1600x2 BA 600x2 DS400 + BA 600x2

DS 800DS 400Untreated DS 1600 BA 600 DS400 + BA 600

DS 800DS 400Untreated DS 1600 BA 600 DS400 + BA 600

Both

Post Transplant

Liner

Phlox Number of BranchesNumber of branches

2 WAT 6 WATApplication Time

Liner 3.6 10.4Post Transplant -- z 11.4Both 3.1y 11.4Application time effect 0.2771 0.3554


Transplant Both0 mg·L-1 2.1c 9.6 10.1 8.8c

400 mg·L-1 DS 2.0c 9.4 11.8 7.6c

800 mg·L-1 DS 2.7bc 9.5 11.5 10.3bc

1600 mg·L-1 DS 4.5a 10.4 11.3 16.8a

600 mg·L-1 BA 3.8ab 13 11.6 13.8ab

400 mg·L-1 DS+ 600 mg·L-1 BA 5.2a 10.8 11.9 11.3bc

Treatment effect 0.0003 0.2473 0.9329 0.0007

Application Time * PGR Concentration 0.2242 0.0317z Not treated at this time

y Treated only at liner stage at this time


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Flower Stalk Height (cm)6 WAT

Application TimeLiner 17.1Post Transplant 18Both 16.1Application time effect 0.1629

PGR Concentration Mean0 mg·L-1 19.5a400 mg·L-1 DS 16.4bc800 mg·L-1 DS 15.6c1600 mg·L-1 DS 16.2bc600 mg·L-1 BA 18.9ab400 mg·L-1 DS+ 600 mg·L-1 BA 15.5cTreatment effect 0.0150

Application Time * Treatment 0.1891

Phlox Flower Stalk Height

Means followed by the same letter are not significantly different at the p<.05 level, n=6

Both

Post Transplant

Liner

DS 800DS 400Untreated DS 1600 BA 600DS400 + BA 600

DS 800DS 400Untreated DS 1600 BA 600DS400 + BA 600

DS 800x2DS 400x2Untr DS 1600x2 BA 600x2DS400 + BA 600x2

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Nepeta Number of BranchesNumber of branches


Liner 16.3 171bPost Transplant -- z 200aBoth 17.6 y 213aApplication time effect 0.025 0.0001


Transplant Both0 mg·L-1 15.4c 179a 159cd 151b400 mg·L-1 DS 15.8c 169a 192bc 171b800 mg·L-1 DS 17.9ab 179a 213b 169b1600 mg·L-1 DS 18.7a 127b 144d 242a600 mg·L-1 BA 16.7bc 181a 294a 261a400 mg·L-1 DS+ 600 mg·L-1 BA 17.3abc 191a 196bc 285aTreatment effect 0.0067 0.0188 <0.0001 0.0001

Application Time * PGR Concentration 0.1139 <0.0001z Not treated at this time




Application TimeLiner 0.365 8.03aPost Transplant -- z 7.41bBoth 0.337y 6.97cApplication time effect 0.0877 <0.0001


Transplant Both0 mg·L-1 0.346 7.55ab 8.11a 7.77bc400 mg·L-1 DS 0.321 8.38a 8.59a 7.19c800 mg·L-1 DS 0.350 8.09ab 7.71a 5.85d1600 mg·L-1 DS 0.325 7.25b 3.24b 3.21e600 mg·L-1 BA 0.387 8.46a 8.20a 9.31a400 mg·L-1 DS+ 600 mg·L-1 BA 0.376 8.46a 8.61a 8.49abTreatment effect 0.117 0.0431 <0.0001 <0.0001


Nepeta Shoot Weight


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Application TimeLiner 22.5 15.7aPost Transplant -- z 13.2bBoth 21.1y 13.2bApplication time effect 0.0004 0.0015


Transplant Both0 mg·L-1 22.4a 17.4a 19.0a 13.8ab400 mg·L-1 DS 22.0a 14.6b 10.8b 15.4ab800 mg·L-1 DS 21.8a 17.2ab 15.2a 11.0bc1600 mg·L-1 DS 18.9b 11.2c 9.6b 7.0c600 mg·L-1 BA 22.8a 15.8ab 16.2a 18.2a400 mg·L-1 DS+ 600 mg·L-1 BA 22.9a 18.2a 8.6b 14.0abTreatment effect <0.0001 0.0002 <0.0001 0.001


Nepeta Height


DS 800DS 400Untreated DS 1600 BA 600 DS400 +BA 600

Both

Post Transplant

Liner


DS 800x2DS 400x2Untreated DS 1600x2 BA 600x2DS400 + BA 600x2

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Gaillardia Number of BranchesNumber of branches


Liner 5.8 30.8bPost Transplant -- z 29.0bBoth 6.1y 53.0aApplication time effect 0.3635 <0.0001


Transplant Both0 mg·L-1 4.8b 28.5b 22.7bc 37.7b400 mg·L-1 DS 5.7b 35.7a 31.2b 40.5b800 mg·L-1 DS 5.1b 32.8ab 31.0b 39.7b1600 mg·L-1 DS 2.5c 19.7c 13.2c 11.8c600 mg·L-1 BA 8.7a 33.4ab 26.8b 100a400 mg·L-1 DS+ 600 mg·L-1 BA 9.1a 34.7ab 49.2a 88.0aTreatment effect <0.0001 0.0006 <0.0001 <0.0001




Application TimeLiner 6.8 14.0aPost Transplant -- z 12.7bBoth 7.2y 11.9cApplication time effect 0.1016 <0.0001


Transplant Both0 mg·L-1 7.7a 14.4a 15.4a 15.0a400 mg·L-1 DS 7.4ab 14.1a 13.9ab 14.8a800 mg·L-1 DS 7.6ab 14.4a 12.4bc 9.6c1600 mg·L-1 DS 6.4c 11.4b 8.9d 4.6d600 mg·L-1 BA 6.8bc 15.1a 14.1a 15.3a400 mg·L-1 DS+ 600 mg·L-1 BA 6.3c 14.9a 11.8c 12.3bTreatment effect 0.0022 0.0002 <0.0001 <0.0001


Gaillardia Height


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Application TimeLiner 0.329 4.27aPost Transplant -- z 3.59bBoth 0.332 y 3.57bApplication time effect 0.7808 <0.0001


Transplant Both0 mg·L-1 0.326bc 4.28a 4.79a 4.64b

400 mg·L-1 DS 0.341ab 4.81a 4.38ab 4.05b

800 mg·L-1 DS 0.297cd 4.54a 3.03d 2.02c

1600 mg·L-1 DS 0.274d 2.49b 1.58e 0.688d

600 mg·L-1 BA 0.374a 4.73a 4.10bc 6.12a

400 mg·L-1 DS+ 600 mg·L-1 BA 0.374a 4.73a 3.67c 3.90b

Treatment effect <0.0001 <0.0001 <0.0001 <0.0001

Application Time * PGR Concentration 0.1367 <0.0001z Not treated at this time


Gaillardia Shoot Weight


Days to First Flower8 WAT

Application TimeLiner 64.7bPost Transplant 49.6aBoth NAApplication time effect <0.0001


Transplant Both0 mg·L-1 48.5d 52.4 53.5b400 mg·L-1 DS 52.4d 48.3 47.9b800 mg·L-1 DS 64.8c 47.8 82.0a1600 mg·L-1 DS 82.0a 49 NA600 mg·L-1 BA 70.5b 50.5 NA400 mg·L-1 DS+ 600 mg·L-1 BA 70.3b 50 NATreatment effect <0.0001 0.6533 0.0003

Application Time * PGR Concentration <0.0001

Gaillardia Days to First Flower


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Both

Post Transplant

Liner

DS 800DS 400Untreated DS 1600 BA 600DS400 +BA 600

DS 800x2DS 400x2Untreated DS 1600x2 BA 600x2DS400 + BA 600x2

Branching Effects on Delosperma and AchilleaDelosperma•No increased branches with any treatment

Achillea•Increased branches only with 2 applications of 600 mg·L-1 BA•Stunting with 2 applications of 800 or 1600 mg·L-1 dikegulac sodium

BA 600x2Untreated

Achillea finished plants treated twice

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Exp. 4: Conclusions

In responsive plants, two treatments caused an increase in branches compared to one treatment

BA increased branches without reducing height or causing phytotoxicity

The combination of BA and dikegulac sodium was effective at increasing branches in 4 of 6 plants studied

Two applications of 1600 mg·L-1 dikegulac sodium caused stunting in most plants studied

Both BA and dikegulac sodium caused flower delay in Gaillardia

Outline

• Introduction





• Conclusions

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Research Objectives To study the effects of branching agents on herbaceous

perennial crops during liner production and on finished plants

To improve plant architecture at an earlier stage of production

Conclusions Treating perennial liners BA and dikegulac sodium before

transplant changed plant architecture by increasing the numbers of branches

Liner quality can be improved with application of PGRs

Results varied by species, as was expected (Gent and McAvoy, 2000)

BA and dikegulac sodium have a short period of activity in plants

A second application of PGRs after transplanting liners may be beneficial

Phytotoxicity is generally transient

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Future Work Timing of application

Multiple applications

Cytokinin analysis

•Dr. Joyce Latimer•Dr. Holly Scoggins•Dr. Eric Ervin•John Freeborn•Jeff Burr•Velva Groover•John James•Shawn Appling•Kevin Harris•Carly Reynolds•J.B. Snelson•Brianna Swanson

Thanks to:

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ReferencesArzee, T., H. LangenDSer and J. Gressel. 1977. Effect of dikegulac, a new growth regulator, on apical growth and development of three Compositae. Bot. Gaz. 138(1):18–28.

Banko, T.J. and M.A. Stefani. 1995. Cutless and Atrimmec for controlling growth of woody landscape plants in containers. J. Environ. Hort.13 (1):22-26.

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Bruner, L.L., G.J. Keever, J.R. Kessler, Jr., and C.H. Gilliam. 2002. Atrimmec suppresses shoot length and promotes branching of Lonicera x heckrottii ‘Goldflame’ (Goldflame honeysuckle). J. Environ. Hort. 20(2):3-76.

Carter, J., B.P. Singh and W. Whitehead. 1996. Dikegulac, but not benzyladenine, enhances the aesthetic quality of Boston fern. HortScience 31:978-980.

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Farris, M.E., G.J. Keever, J.R. Kessler, and J.W. Olive. 2009. Benzyladenine and cyclanilide promote shoot development and flowering of Coreopsis verticillata 'Moonbeam'. J. Environ. Hort. 27(3):176-182.

Gent, M.P.N. and R.J. McAvoy. 2000. Plant growth retardants in ornamental horticulture: a critical appraisal, p. 89-130. In Basra, A.S. (ed.) Plant growth regulators in agriculture and horticulture: their role and commercial uses. Food Products Press, Binghamton.

Keever, G.J. 1994. BA-induced offset formation in Hosta. J. Environ. Hort. 12 (1):36-39.

Latimer, J. and J. Freeborn. 2008. Enhance branching of Echinacea with PGRs. Greenhouse Product News 18(4):24–28.

ReferencesLatimer, J.G. and J. Freeborn. 2010. Branching enhancers, BAigure (6-BA) and DSgeo (dikegulac sodium), affect branching of herbaceous perennials. Proc. Plant Growth Regulat. Soc. Amer. 37:148-152.

Miller, C. O.; Skoog, F.; Von Saltza, M. H.; Strong, F. M. 1955. Kinetin, a Cell Division Factor from Deoxyribonucleic acid. J. Am. Chem. Soc. 77:1392.

Martin, S. and S. Singletary. 1999. N-6 Benzyladenine increases lateral offshoots in a number of perennial species. Proc. Intl. Plant Prop. Soc. 49:329-334.

Nightingale, A.E., S.E. Cross and M.T. Longnecker. 1985. Dikegulac alters growth and flowering of Kalanchoe. HortScience 20:722-724.

Sachs, R.M., H. Hield, and J. DeBie. 1975. Dikegulac: a promising new foliar-applied growth regulator for woody species. HortScience 10 (4):367-369.

Whitman, C. and E. Runkle. 2003. PGR rates and timing for plug production. Greenhouse Product News 13(12):38-43.

USDA 2011. Floriculture Crops 2010 Summary. Cited November 17, 2011. <http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1072>

USDA 2009. Census of Horticultural Specialties.Cited November 17, 2011. <http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Census_of_Horticulture/HORTIC.pdf>

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For More Information:

Mara Grossman: [email protected]

http://www.horticulture.vt.edu/floriculture

Questions?

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