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Gibberellic Acid Induced Flowering of Paphiopedilum (Macabre ×
glanduliferum)
T.P. Miguel and W.S. Sakai J. Fang
College of Agriculture, Forestry and Hilo Orchid Farm
Natural Resource Management, Mountain View, Hawaii 96720
University of Hawaii at Hilo USA
Hilo, Hawaii 96720
USA
Keywords: orchids, flower induction, plant growth regulators
Abstract
Because four year old Paphiopedilum (Macabre × glanduliferum) plants with
multiple shoots had not flowered, we attempted to induce flowering by use of plant
growth regulators. Twenty-five ml of 866 ppm gibberellic acid (GA3) or 500 ppm N6
-
benzyladenine (BA) or a combination of 866 ppm GA3 + 500 ppm BA or 500 ppm 1-
naphthaleneacetic acid (NAA) + 500 ppm BA or 250 ppm NAA + 500 ppm BA was
applied as a spray to run-off to the top of the plant with some drenching of the roots,
to each of 10 plants in a randomized complete block design. Ten untreated plants
served as control. The gibberellic acid treatment resulted in all 10 plants producing an
average of 3.8 inflorescences per plant. Controls and plants treated with, BA or BA +
NAA did not produce any inflorescence. BA appeared to reduce the effect of GA3 in
the combination treatment, with 6 plants producing an average of 3.2 inflorescences
per plant.
INTRODUCTION
Paphiopedilum (Orchidaceae) are among the flowering plants grown in large scale
commercial production in Hawaii. While these orchids may naturally flower during its
season, instances exist where potted flowering orchids are needed throughout the year,
and during times of high-market demand. In our experiment, a large population of the
hybrid Paphiopedilum (Macabre × glanduliferum) growing at Hilo Orchid Farm in
Mountain View, Hawaii had not flowered for over four years. These plants had multiple
growths that appeared capable of flowering, but had not done so since maturing.
Plant growth regulators have been shown to play a role in inducing several orchid
genera to initiate or produce inflorescences. Goh (1977) demonstrated that the auxin anta-
gonists maleic acid hydrazide (MH) and 2,3,5-triiodobenzoic acid (TIBA), the cytokinin,
6-benzylaminopurine (BAP), and GA3 together with BAP initiated inflorescence initials
when injected into the stems of Aranda. Similarly, BA injections into mature canes of
Dendrobium produced flowers in this genus (Sakai et al., 2000). Gibberellins were used to
stimulate flowering in Bletilla, Cymbidium, Cattleya (Goh et al., 1982). Matsumoto
(2006) showed that GA3 and BA promoted early flowering in Miltoniopsis when applied
as a drench. We used GA3, BA and NAA in our study in attempts to promote flowering in
an unbloomed population of Paphiopedilum (Macabre × glanduliferum).
MATERIALS AND METHODS
Four year old plants of Paphiopedilum (Macabre × glanduliferum) with three to
four matured growths (fans) were selected and treated at Hilo Orchid Farm. The plants
had different degrees of leaf mottling and coloration that displayed a cross sectional
representation of their parental background.
Ten plants per treatment with two blocks of five plants per treatment were set in a
randomized complete block design. Twenty-five ml of 866 ppm GA3 or 500 ppm, BA or a
combination of 866 ppm GA3 + 500 ppm BA or 500 ppm NAA + 500 ppm BA or 250
ppm NAA + 500 ppm BA was applied as a foliar spray to run off with drenching of the
roots. Ten untreated plants served as control.
Proc. XXVII IHC-S5 Ornamentals, Now!
Ed.-in-Chief: R.A. Criley
Acta Hort. 766, ISHS 2008
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RESULTS AND DISCUSSION
At 11 weeks after treatment with plant growth regulators, plants treated with GA3
and combination BA + GA3 developed inflorescences. Gibberellic acid treatment resulted
in all 10 plants producing an average of 3.8 inflorescences per plant (Fig. 1).
Inflorescences developed in the most recently matured growths as well as in the older
growths. Combination BA + GA3 treatment resulted with 6 plants yielding an average of
3.2 inflorescences per plant. Controls and plants treated with, BA or BA + NAA did not
initiate inflorescences (Table 1).
The effects of GA3 and BA + GA3 treatments on spike habit and flowering were
also observed. Flowers appeared normal in both treatments (Fig. 2). However, the GA3
resulted in longer inflorescences. The cytokinin, BA in combination with GA3 appeared to
reduce the effect of GA3 resulting in fewer spikes per plant, but developing normal
inflorescences (Fig. 3). Flowering was delayed by 14 days when compared to the GA3
alone. Goh (1977) reported a three week delay of bud initiation in Aranda when a
combination of cytokinin and GA3 was used.
Paphiopedilum (Macabre × glanduliferum) is an intersectional hybrid derived
from species that bloom from the late spring to the early fall (Hamilton, 1990). Applying
GA3 and BA + GA3 in the fall (September) encouraged Paphiopedilum (Macabre ×
glanduliferum) to flower in the winter (January). This suggests that using GA3, or the
combination of BA + GA3 on mature fans may induce flowering on growths that would
not normally flower until the following spring.
It previously appeared that the apical meristem of Paphiopedilum senesced if it
did not flower. However, the fact that GA3 induced flowering in the two and three year
old growths of Paphiopedilum (Macabre × glanduliferum) suggests that the apical
meristem in Paphiopedilum can become dormant and remain dormant for many years.
This is a new finding.
The combination BA + GA3 treatment stimulated inflorescence development in the
most recently matured fans of Paphiopedilum (Macabre × glanduliferum), and not as
many in the older growths as those in the GA3 treatment. Using GA3 alone and at the 866
ppm concentration encouraged flowering in all competent shoots, but at the expense of
abnormal inflorescences. Using BA added to GA3, or using growth retardants may be
useful in reducing the effect of GA3 and decrease inflorescence length.
CONCLUSIONS
GA3 and BA + GA3 promoted flowering in Paphiopedilum (Macabre ×
glanduliferum). Orchid growers may choose this relatively easy method to control
flowering of their plants. Further study can lead to application rates for other
Paphiopedilum hybrids and can help the industry reduce production time and produce
flowering plants to meet high market-demand periods.
The concentration of the GA3 applications warrants future study as the results
gained by the GA3 treatments may be species or grex specific. Earlier work with
Paphiopedilum showed that low concentrations of gibberellins applied at 10 ppm with a 1
or 2 second foliar spray each week resulted in little gain in the flowering time of the first
bloom (Smith, 1958). GA3 reduced the time of inflorescence emergence in certain
cultivars of Miltoniopsis, and it was suggested that higher concentrations of GA3 may be
required to promote inflorescence induction in older plants (Matsumoto, 2006).
Future research will involve the use of varied concentrations of GA3 and BA +
GA3 in combination and tests of their effect on other sections in Paphiopedilum or related
genera. Studies will also be made of GA3 treatment followed by treatment with growth
retardants to reduce flower stem length.
ACKNOWLEDGEMENTS
Our research was made possible through a grant from the United States
Department of Agriculture, Agricultural Research Service – Pacific West Area, “Develop-
ment of Post Harvest Technologies and Value Added Products to Improve and Promote
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Agricultural Development in Hawaii” #5320-43000-014-01S. The authors wish to thank
the USDA, Pacific Basin Agriculture Research Center, Mr. Dave Wright and the staff of
Hilo Orchid Farm and Tilden-Christain Miguel, student research assistant.
Literature Cited
Goh, C.J., Strauss, M.S. and Arditti, J. 1982. Flower induction and physiology of orchids.
p.214-241. In: J. Arditti (ed.), Orchid biology: Reviews and Perspectives. vol. 2.
Cornell Univ. Press, Ithaca, N.Y.
Goh, C.J. 1977. Regulation of floral initiation and development in an Orchid hybrid
Aranda Deborah. Ann. Bot. 41:763-769.
Hamilton, R.M. 1990. Flowering months of orchid species under cultivation. p.375-377.
In: J. Arditti (ed.), Orchid biology: Reviews and Perspectives. vol. 5. Timber Press,
Oregon.
Sakai, W.S., Adams, C. and Braun, G. 2000. Pseudobulb injected growth regulators as
aids for year around production of Hawaiian Dendrobium orchid cut flowers. Acta
Hort. 541:215-200.
Matsumoto, T.K. 2006. Gibberellic acid and benzyladenine promote early flowering and
vegetative growth of Miltoniopsis Orchid hybrids. HortScience 41(1):131-135.
Smith, D.E. 1958. Effect of gibberellins on certain orchids. Amer. Orchid Soc. Bull.
27:742-747.
Tables
Table 1. Inflorescences produced in Paphiopedilum (Macabre × glanduliferum) 11 weeks
after treatment with plant growth regulators.
Treatment No. plants
treated
No. plants with
inflorescences
Total no. of
inflorescences
Inflorescences
per plant
Control 10 0 0 0
BA 10 0 0 0
BA + NAA 10 0 0 0
GA3 + BA 10 6 19 3.17
GA3 10 10 38 3.80
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Figurese
Fig. 1. Flowering of Paph. (Macabre × glanduliferum). Control plants (on left) with no
inflorescences and those treated with GA3 (on right) producing inflorescences.
Fig. 2. Normal appearing flower of Paph. (Macabre × glanduliferum).
Fig. 3. Effects of GA3 (on left) and combination BA + GA3 (on right). Note the elongated
inflorescence resulting from application of GA3 alone.
