4/16/2012 1 Using Plant Growth Regulators to Improve Plant Architecture in Herbaceous Perennial Plants Mara Grossman M.S. student Department of Horticulture Virginia Tech Introduction Commercial 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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4/16/2012
1
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
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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
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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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
Leucanthemum 4 WAT
Basal branches doubled at 4WAT
Untreated Control
300x2Untreated 300x1 600x1
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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
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
Untreated 300x1 300x2 600x1
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
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Verbena 4 WAT
Number of lateral branches was significantly increased at higher rates
Untreated 300x1 300x2 600x1
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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
Veronica 3 WAT
Untreated 300x1 300x2 600x1
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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
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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
Cosmos atrosanguineus
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)
Untreated 300x1 300x2 600x1
Veronica spicata ‘Goodness Grows’
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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
600x1300x2300x1Untreated
Lavandula x intermedia ‘Provence’
Gaura ‘Siskyou Pink’
Exp. 1: Results and Discussion:Effects on Roots
600x1300x2300x1Untreated
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
Means followed by the same letter are not significantly different at the p<.05 level, n=6.
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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
800400Untreated 1600
Veronica spicata ‘Goodness Grows’
Dikegulac sodium on Veronica at 4 WAT
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
Veronica spicata ‘Goodness Grows’
Dikegulac sodium on Veronica at 4 WAT
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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
• 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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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
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.
Bell, M.L., R.A. Larson, and D.A. Bailey. 1997. Vegetative growth responses of florist azaleas to dikegulac, GA4+7, and 6-benzylamino purine. HortScience 32 (4):690-693.
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.
Dole, J.M. and H.F. Wilkins, 2005. Floriculture : principles and species. Pearson/Prentice Hall, Upper Saddle River, N.J.
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 2009. Census of Horticultural Specialties.Cited November 17, 2011. <http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Census_of_Horticulture/HORTIC.pdf>