In the U.S.. orchids rank second in valuefor potted flowering plants (between poinset-tias and chrysanthemums) and were valuedat $128 million in 2004, a 5% increase over2003 production (USDA—NASS, 2005).Commercial poinsettia and chrysanthemumproduction rely heavily on standard practicesof flower induction to fulfill market demand(Larson, 1980). In contrast, availability of mostorchids is based on the genetic diversity of thislarge family and on flowers produced at loca-tions that vary in climatic conditions.

Potted orchid production in Hawaii ranksthird in the U.S. behind California and Floridaand is. valued at $17 million (USDA—NASS,2005). Growth of Hawaii's orchid industry isattributed to increased export sales with two-thirds of Hawaii's orchid production beingexported out of the state. Demand for pottedorchids is increasing in southern and westernstates ofthe U.S.,where >90% ofpotted orchidsare sold. Hawaii orchid growers face manychallenges in producing orchids to meet themarket demand, including foreign competi-tion from The Netherlands and countries in

Received for publication 30 Sept. 2005. Acceptedfor publication 2 Nov. 2005. The author thanksJames Fang of Hilo Orchid Farm Hawaii, for kindlydonating the plants and use of greenhouse facilities;Ivan Komoda for helpful discussion on Mil/oniopsisbreeding and culture and Tsuyoshi Tsumura for ex-cellent technical assistance. Mention of trademark,proprietary product, or vendor does not constitutea guarantee or warranty of the product by the U.S.Department of Agriculture and does not imply itsapproval to the exclusion ofotherproducts orvendorsthat also may be suitable.'E-mail tmatsumoto@pbarc.ars.usda.gov .

SoutheastAsia. Hawaii orchid farms are usuallysmaller than their counterparts in Californiaand Florida and often less mechanized (HawaiiDepartment ofAgriculture, 2004). These typesof growing conditions make it economicallydifficult to modify environmental conditionssuch as the photoperiod and temperature topromote flowering.

Flowering relies on a developmentallycompetent plant to favorably perceive envi-ronmental signals to initiate the transition fromvegetative to reproductive growth (Bernier etal., 1993, Goh et al., 1982). Natural floweringseasons of orchids may be dependent uponphotoperiod, light intensity, temperature, waterrelations and plant hormones (Goh, 1985).Native to Costa Rica, Panama, Venezuela,Columbia, and Ecuador, Miltoniopsis orpansy orchid, is comprised of six species: Mbismarckii, M vexillaria, M roezlii, M pha-laenopsis, M. warscewiczii, and M. santanaei,which bloom during different times ofthe year(Baker and Baker, 1993; Sweet, 1978). Mostcultivated hybrids have M. vexillaria and Mroezlii as parents and consequently bloom dur-ing March to July (Baker and Baker, 1993).Hybrids of Milloniopsis may be mistaken forMiltonia because four of the six species werepreviously classified and registered as Miltonia(Baker and Baker, 1993). Miltoniopsis plantsconsist of one-leaved flattened pseudobulbsthat are tightly clustered and light grayishblue-green in color compared to Miltoniaplants that consist of two-leaved pseudobulbsthat are yellowish green to honey-colored andseparated by a long rhizome (Baker and Baker,1993; Sweet, 1978).

Plant growth regulators have been used suc-

cessfully to modify flowering of many orchidspecies. Auxin application to Pha/aenopsis.scliillerana or exogenous auxin supply todecapitated Aranda plants reduced floweringwhile application of anti-auxin and growthretardants stimulated Aranda flowering, sug-gesting that apical dominance and auxin sup-press flowering (Goh, 1985). The cytokininN 6-benzyladenine (BA) induced floweringof Aranthera, Aranda, Holitumara, Mokara,Dendrobium Lousiae 'Dark', Phalaenopsis,Dendrobium nodoka, and Oncidium; however,this response is highly depended on orchidvariety (Goh, 1985; Hew and Clifford, 1993).Gibberellins transformed the normal vegeta-tive shoot apex to a terminal inflorescenceof Aranda Deborah and induced floweringof Bletilla striata, Cymbidium, and Cattleyahybrids (Goh, 1985; Gob et al., 1982). Ad-dition of GA with cytokinins enhanced theflowering effect and reduced flower deformityof Phalaenop.sis and Dendrobium (Chen et al.,1997; Sakai et al., 2000). Injection of 100 mmofBA and 10 mtvi GA 3 into Dendrobium Jaque-lyn Thomas 'Uniwai Princess' pseudobulbspromoted off season flowering and increasedthe flower size and number of inflorescencesper stem in Hawaii (Sakai et al., 2000).

Market demand for Miltoniopsis is highestduring Decemberto March In Hawaii, the typi-cal flowering season is in Mar. to June; however,flowering dates may vary slightly with climaticconditions and cultivars. Previous reportssuggest that flowering in Milton iop.si.s' Augres'Trinity' is controlled by a combination ofcooltemperature (14 °C) and short photoperiod of9 It (Lopez et al., 2005) or cool temperature(15 °C) alone (Matsui and Yoneda, 1997). Theadditional expense to provide cooler tempera-tures for floral induction may be prohibitivefor Miltoniopsis production. While BA andGA applications have successfully promotedflowering in otherorchid species, this is the firststudy to use plant growth regulators to modifyflowering in Miltoniopsis. Since the effect ofplant growth regulators on Milton iopsis is notknown, we used two Miltoniopsis grexes withdifferent flowering seasons. Bert Field 'Eileen'typically flowers in Hawaii in February to Mayand Rouge 'Akatsuka' flowers in March toJune. Soil drenches were more effective as amethod of plant growth regulator applicationcompared to foliar sprays (Karaguzel, et al.,2004). Therefore, we investigated the effect ofBA and GA soil drenches alone or combinedto promote earlier flowering of 'Eileen' and'Akatsuka'.

Materials and Methods

Plant materials. 'Eileen' (Miltoniopsis Mu-latto Queen x Miltoniopsis Woodlands) (RoyalHorticultural Society, 2005a) and 'Akatsuka'(Miltoniopsi.s Edmonds x Miltoniopsis Ham-burg) (Royal Horticultural Society, 2005b)plants were grown by a commercial nurseryunder covered greenhouses in Kurtistown,Hawaii, with maximum photosynthetic photonflux (PPE) of about 335 1molm 2 s 1 . Plantswere grown under natural photoperiods (19°N lat) where the longest and shortest days

I-IORTScIENCE4I(l):131-135. 2006.

Gibberellic Acid and BenzyladeninePromote Early Flowering andVegetative Growth of Milton iopsisOrchid HybridsTrade K. Matsumoto'U.S. Department ofAgriculture, Agricultural Research Service, Pacific BasinAgricultural Research Center Tropical Plant Genetic Resource ManagementUnit, P.O. Box 4487, Hilo, HI 96720Additional index words, pansy orchid, flower induction, plant growth regulators

Abstract. Flowering of Miltoniopsis orchids is influenced by a combination of cool tempera-tures and short photoperiod. To determine if application of plant growth regulators couldpromote flowering without the need for costly structural modification to control photoperiodor temperature, we used drenches of gibberellic acid (GA 3)(2.5 or 5 m\1), N6-benzyladenine(BA) (25 or 50 mm) alone or in combination. BA (25 or 50 mm) treatments promoted newvegetative shoots and decreased the number of plants with inflorescences compared to theuntreated control plants. This reduction of flowering and increased vegetative shoot produc-tion was alleviated by the addition of GA in combination with BA. However, the numberof plants with inflorescences remained less than the control. GA hastened Miltoniopsisinflorescence emergence during the first flowering season by 10.9 to 14.9 days for Bert Field'Eileen' and by 48.7 days for Rouge 'Akatsuka'. The number of 'Eileen' inflorescences pro-duced per plant increased from 2.2 to 3.0 with 2.5 mm GA treatment. Flower deformitieswere not observed in the GA treated plants, and flower size and inflorescence length wereunaffected by the GA treatment.

HORTSCIENCE VOL. 41(1) FEBRUARY 2006 131

Table I. The effect of BA and GA treatments on growth, vegetative shoot production, and flowering (number of plants with visible inflorescences) on Bert Field'Eileen' and Rouge 'Akatsuka' hybrid Miltoniopsis orchids.

'Eileen' 'AkatsukaHEDiam'Vegetative Flowering HtDiamVegetative Flowering

Treatment Leaves7(cm)(cm)shoots'(%)Leaves(cm)(cm)shoots(%)Control 9.0 ab38.4 ab19.0 a0.21 c9610.7 be45.8 a25.3 a0.39 c8825 mm BA 9.4 a39.8 ab17.5 ab2.71 a5811.5 a44.0 ab22.8b1.89 a3850 mm BA 9.0 ab37.1 ab16.4 be1.86b3311.5 a43.8 abc22.2b1.74 a442.5 mm GA 8.6 ab37.0 ab17.5ab0.20 c8410.2 cd41.6bcd21.7 be0.31 c885mM GA 8.5 b36.8 b16.5 be0.20 c969.7 d43.4 abc21.4bc0.30 c8925 mm BA, 2.5 mm GA9.0 ab36.5 b16.0 be0.56 c7411.2 ab41.0 cd21.1 be1.64 ab7350 mm BA, 5mM GA8.7 ab34.4 c15.3c0.52 c3910.5 cd39.2 d19.8c0.96 be59MSE' 0.8111.934.320.73 0.8111.337.220.87'Maximum pseudobulb height and diameter.'Maximum number of leaves.'Number of new shoots.'Mean separation in columns by Tukey's multiple range test at P 0.05. Any two means within a column not followed by the same letter are significantly dif-ferent at P <0.05.'Mean square error.

inclusive of civil twilight are 14.1 and 11.75 hrespectively. Civil twilight begins in the morn-ing and ends in the evening when the center ofthe sun is 6° below the horizon. The monthlytemperature mean was 19.0 to 21.9 °C, withminimum temperature ranges from 12.2 to 17.5°C and maximum temperature ranges from27.2 to 31.5 °C, with coolest temperatures inFebruary and warmest in July or August.

Plants were clonally propagated in vitro,transplanted from flasks to rooting cubes for8 months and transplanted to 10-cm pots inFebruary through March 2003 and 2004 forexperiments 1 and 2 respectively. Plants weregrown in a mixture of 50% fir bark (I to 1.3cm particle size), 25% coconut husk (1.3 to 1.9cm particle size, washed thoroughly in water)and 25% black volcanic cinder (1 to 1.3 cmparticle size). Plants were fertilized with 0.8to 1.6 g of Nutricote 13N-5.7P-10.8K plusmicronutrients (Chisso-Asahi Fertilizer Co.Ltd., Tokyo, Japan) 1 month after transplant-ing and foliar fertilized and irrigated with 85ppm N; 13.7 ppm P; 74.7 ppm K, twice aweekthrough an overhead boom watering system.Pots were flushed with water once every 2weeks to prevent salt build up.

Commercially, Miltoniopsis plants areshipped in various stages of inflorescencedevelopment and flower opening dependentupon customer preference. The first indica-tion of flowering is inflorescence emergence.Thus, flowering in the study was consideredto occur when the inflorescence emerged fromthe leaf axis and was visible without dissec-tion (Lopez et al., 2005). Miltoniopsis plantstypically flower approximately one year afterbeing transplant to pots from rooting cubes andare approximately two years old since beingtransplanted from the flask. These inflores-cences will be referred to as the first floweringseason. Inflorescences from plants left in thepots for an additional year will be referred toas the second flowering season.

Treatments. (Expt. 1) On 12 Nov. 2003,8 months after being transplanted to 10 cmpots (about 1.5 years from in vitro culture),'Eileen' plants had an average of three pseu-dobulbs per pot and 'Akatsuka' plants hadan average of two pseudobulbs per pot. BA(N6-benzyladenine) and GA were dissolved

in 95% ethanol at the concentrations listed foreach treatment, and distilled water was addedto a final concentration of 10% ethanol. Thepotting medium of 'Eileen' and 'Akatsuka'plants was drenched with 50 mL of the fol-lowing treatments; 10% ethanol water solution(control), BA (25 or 50 mm), GA (2.5 or 5mm) or combination of BA and GA (50 mmBA and 5 mm GA or 25 mm BA and 2.5 mmGA,) (Table I). To ensure complete saturationof the potting medium with the plant growthregulator solution, excess solution that passedthrough the pot was collected and reappliedto the medium for a total of 3 times. Plantswere monitored from 9 May 2003 to 21 June2004 every 2 weeks for number of leaves,pseudobuib height from the soil line to theleaftip, pseudobulb diameter perpendicular tothe leaf axis and number of vegetative shootsor visible inflorescences. The experimentwas a completely randomized design with 25plants per treatment. The data were analyzedby ANOVA or 1-test analysis using SigmaStat(Systat Software, Point Richmond, Calif.).

Experiment 2. On 17 Nov. 2004, the experi-ment was repeated to confirm the effect of 2.5mm GA observed in Expt. 1 and to determineif the 2.5 mm GA 3 treatment could promoteflowering during the second flowering sea-son. Since foliar damage and slight flowerdeformities was observed in all treatmentscontaining 10% ethanol and not observed inother plants in the greenhouse, 2.5 mm GA was dissolved in sodium hydroxide (NaOH)instead of ethanol for a final concentrationof 0.026 N NaOH. The potting medium of'Eileen' plants 8 months after transplant to10 cm pots and 'Akatsuka' plants 1 year and8 months after transplant to 10 cm pots weredrenched with either 2.5 mm GA or watercontaining 0.026 N NaOH as a control. Inflo-rescence emergence was monitored weekly,and inflorescence length and flower heightand width were measured after all flowers onthe inflorescence were fully opened. Days toinflorescence emergence was defined as thenumber of days until the first inflorescencewas visible for each plant. The experimentwas completely randomized with 40 plantsper treatment. The data were analyzed bytest analysis using SigmaStat.

Results

Growth of MiltoniopsisExperiment 1. Milton iopsis plants are sym-

podial in growth. At the start of plant growthregulator treatments on 12 Nov. 2003, 'Akat-suka' plants had an average of two pseudobulbsper pot and 'Eileen' had three pseudobulbsper pot. The older pseudobulbs maintained aconstant height and diameter although slightreduction was observed in the diameter beforegrowth of new vegetative shoots from thebasal buds. The pseudobulbs that produced theinflorescences observed in this study emergedin May through July of 2003. Growth of theimmature vegetative shoots proceeded withsimultaneous increase in number of leaves,pseudobulb height and diameter. Inflorescencesemerged from the top one to four lateral leafaxes after the pseudobulb reached a maximumheight and diameter. The pseudobulb heightincreased until it reached a maximum height,an average of 8 weeks before inflorescenceemergence. Pseudobuib diameter continuedto expand and reached a maximum diameter,an average of 4 weeks before inflorescenceemergence.

BA and GA, effect on plant stature andinflorescence emergence

Since flowering of Miltoniopsis is associ-ated with growth of the orchid pseudobulb,we monitored the effect of the plant growthregulator treatments on each pseudobulb todetermine the maximum number of leaves,pseudobulb height and diameter, and vegetativeshoot emergence of each plant. Although we

Table 2. Number ofdays to inflorescence emergencefor Bert Field 'Eileen' and Rouge 'Akatsuka'Miltoniopsis orchid hybrids following soildrenches with GA treatments in 2004.

Treatment'Eileen''Akatsuka'Control 114.9 al183.0 a2.5 mm GA104.0 b134.3 c5 m GA107.9ab162.1 bMSE 102.1494.0'Mean separation in columns by Tukey's multiplerange test at P 0.05. Any two means within a col-umn not followed by the same letter are significantlydifferent at P <0.05.Mean square error.

132 HORTSCIENCE VOL. 41(1) FEBRUARY 2006

0 - /- I.0..........

//• 0* - I0 • •• _-1'

/7-

I -•-- Control0 2.5mM GA

-- 5mMGA-7

Mar 01 Apr 01 May 01 Jun 01 Jul 01

Date

80

60

40

20

detected more leaves on BA treated 'Akatsuka'plants, the BA and GA treatments did notsignificantly change or decrease the maximalheight and diameter of the pseudobulbs inboth 'Eileen' and 'Akatsuka' plants (Table I).Application of BA treatments consistently in-creased vegetative shoot production in 'Eileen'treated with 25 mm BA (2.71 shoots) and 50mM BA (1.86 shoots) and 'Akatsuka' plantstreated with 25 mm BA (1.89 shoots) and 50mm BA (1.74 shoots). These vegetative shootsdeveloped normally into pseudobuibs and didnot produce inflorescences during the courseof the experiment. The pseudobulbs that didproduce inflorescences were similarto those incontrol plants that emerged during May to Juneof 2003. BA treatments resulted in a decreasein the number of plants with inflorescences andthis decrease in flowering was alleviated by theaddition of GA,. Of'Eileen' plants treated with25 mm BA, 58% produced inflorescences andthe addition of 2.5 mm GA resulted in 74%plants with inflorescences. Treatment with25 or 50 mtvi BA resulted in 38% and 44% of'Akatsuka' plants with inflorescences. For thesame BAtreatments supplemented with 2.5 and5.0 mm GA, respectively, the number of plantswith inflorescences increased to 73% and 59%(Table 1). However, with the addition of GA,the number of plants with inflorescences wasstill less than the control suggesting that BAinhibited inflorescence emergence and this wasalleviated by GA..

GA effect on inflorescence emergenceExperiment I. Inflorescences were pro-

duced by 96% of 'Eileen' control plants and5 mm GA treated plants while 84% of theplants treated with 2.5 mm GA, (Table I). Of'Akatsuka'plants treated with 0 (control) or2.5mm GA3, 88% to 89% produced inflorescences.The GA 3 treatments were the only treatmentsthat did not significantly alter the total numberof plants with inflorescences. Therefore, wedetermined if GA,affected the number of daysfrom treatment to inflorescence emergence(Table 2). The inflorescence of 'Eileen' plantstreated with 2.5 mm GA emerged an averageof 10.9 d earlier than untreated control plants.The effect of GA on 'Akatsuka' plants wasgreater, with inflorescences emerging from 2.5and 5 mm GA, treated plants, 48.7 and 20.9 dearlier than control.

Comparing the percentage of plants withinflorescences to the total number of treatedplants, we observed that on 17 Feb. 2004 only4% of the control 'Eileen' plants had inflores-cences relative to 56% of plants treated with2.5 mtvi GA, and 24% of 5mM GA treatedplants (Fig. 1). By 29 Mar. 2004 there was nodifference between the control and 5 mm GA treatments (96% plants with inflorescences).Inflorescences of 'Akatsuka' plants treatedwith 2.5 mm GA, emerged on 15 Mar. 2004at 69% while inflorescences of control plantsdid not emerge until 29 Mar. 2004 at 4% (Fig.2). By 7 June 2004 the number of floweringplants of control (88%) was similar to thoseobserved in 2.5 mtvi (88%) and 5 mm (89%)GA treated plants (Fig. 2). These data suggestthat GA treatments did not affect the overall

flowering but reduced the time for inflorescenceemergence.

Experiment 2. To determine if the effect ofGA, on inflorescence emergence is reproduc-ible, we treated 40 'Eileen' plants approachingthe first flowering season with 2.5 mm GA,'Akatsuka' plants approaching the first flower-ing season season were not available for ex-perimentation. Therefore, we treated 40 plantsapproaching the second flowering season todetermine if 2.5 mtvi GA would have the sameeffect on promoting inflorescence emergenceon these olderplants. Inflorescences of'Eileen'

a)()

U)0(I)()09-Ca).0Cl)>

(I)CCo

3-

U)0Cci)()Cl)ci)0

C

a).0(0>-C

CO

CCo

0

emerged on 2 Feb. 2005 with 63% of the GA,treated plants with visible inflorescencescompared to 37% of the control plants (Fig.3). 'Akatsuka' inflorescence emergence com-menced on 28 Mar. 2005 with 20% of the GA treated plants with inflorescences and none ofthe control plants. Inflorescence emergence wasobserved 1 week earlier in 'Akatsuka' plantstreated with GA,. Inflorescences emergedfrom 'Akatsuka' control plants an average of161.7 d after treatment compared 155.1 d forplants treated with 2.5 mm GA.. However, thisdifference was not significant (P = 0.13). The

/ 080 --0

//-

1 /60

40

20

/ S Control/ 0 2.5mM GA

/-i'---

Feb 02Feb 16Mar 01Mar 15Mar 29

Date

Fig. I. Percentage of Bert Field 'Eileen' plants with visible inflorescences following treatment with 0(control), 2.5, or 5 mm GA, soil drenches on 12 Nov. 2003. Plants were monitored every 2 weeks from17 Feb. 2004 to 29 Mar. 2004.

i['III

Fig. 2. Percentage of Rouge 'Akatsuka' plants with visible inflorescences following treatment with 0(control) or 2.5 mrvi GA

'soil drenches on 12 Nov. 2003. Plants were monitored every 2 weeks from

I Mar. 2004 to 12 June 2004.

HORTSCIENCE VOL. 41(1) FEBRUARY 2006 133

80

60

40

100

.r. r, .r o000000

20-•-- Control

0 2.5mMGA

Feb 01Mar 01 Apr 01May 01 Jun 01

Date

WC)Ca)C)U)a)0

C

a).0.Q)

>

C,)

C

a-

number of inflorescences per plant was alsonot significantly different in control plants,with 2.9 inflorescences per plants compared 3inflorescences per plant for GA treated plants(P = 0.78). These data suggest that the 2.5 mMGA does promote inflorescence emergenceof Milioniopsis plants approaching the firstflowering season.

The mean number of days to inflorescenceemergence of 'Eileen' was reduced to 91.2 din plants treated with 2.5 mm GA3 , an aver-age of 14.5 d less than control plants whichflowered in 105.7 d (P = 0.006). The numberof inflorescences per plant was increased in'Eileen' plants treated with GA to an aver-age of 3 inflorescences per plant comparedto 2.2 inflorescences per control plant (P =0.02). Flower deformities were not observedin plants treated with GA and no significantdifferences were observed in the length of theinflorescence or in the width and length of theflower (data not shown).

Discussion

A soil drench application of 2.5 mm GA,effectively reduced the time of inflorescenceemergence in 'Eileen' by 10.9 (Expt. I) or14.5 (Expt 2) d compared to the controls and in'Akatsuka' by 48.7 d (Expt. 1) during the firstflowering season. However, this treatment wasineffective in hastening inflorescence emergencein 'Akatsuka' plants during the second flower-ing season. Since these plants contain a greaternumber of pseudobulbs per plant compared toplants in the first flowering season, allocation ofthe GA may result in less GA per pseudobuiband the GA 3 effect on inflorescence emergencemay be decreased. Higher concentrations ofGA may be required to promote inflorescenceemergence in olderplants with a greater numberof pseudobulbs per pot.

Promotion of inflorescence emergence byGA is more effective in 'Akatsuka' plantsthan 'Eileen' plants. Differences in the effec-tiveness of GA on inflorescence emergenceof these grexes may be due to the differencesin the response to temperature during floraldevelopment as a result of the different geneticbackgrounds. Previous reports indicate thatflowering in Miltoniopsis Augres 'Trinity' ispromoted by short days and cool temperatures(Lopez et al., 2005). The natural flowering sea-son for 'Akatsuka' (mid Mar. through June) isslightly later than the natural flowering seasonof 'Eileen' (February to May), and at a timeof year where the average daily temperature isincreasing. This may be similar to the situationin Phalaenopsis where GA applications effec-tively promoted the development of flowersduring normally inhibitory high temperatures.This was due to the promotion of longitudinalgrowth of the flower primordium by GA application (Chen et al., 1994, 1997). Treat-ment of Phalaenopsis flowering shoots withGA at warmer temperatures increases levelsof the active GA: required for the promotionof flower development to the same extent aslevels found in flowering shoots grown at cooltemperatures (Su et al., 2001).

GA treatments of certain Cypripedium andCattleya plants resulted in earlier floweringcompared to control plants (Smith, 1958).Growth retardants known to inhibit GAsynthesis or antagonize GA effects such as,paclobutrazol and uniconazole, progressivelydelayed flowering of Pha/aenopsis orchidplants at increasing concentrations of bothretardants during the second bloom season(Wang and Hsu, 1994). GA promotes flowerdevelopment in Arabidopsis by inhibitingthe DELLA repressor proteins and increas-ing the expression of floral homeotic genes,APETALA3 (AP3), PISTILLATA (P1) and

AGAMOUS (AG) (Yu et al., 2004). MADS-box genes, which are often associated with thefloral transition of the meristem, have beenisolated from Aranda 'Deborah' using AG as aprobe (Lu eta!, 1993) and by differential displayanalysis in Dendrobium (Yu and Goh, 2000a,2000b; reviewed in Mudalige and Kuehnle,2004) suggesting a similar GA pathway foundin Arabidopsis may exist in orchids.

Applications of GA (Chen etal., 1997) orBA (Sakai et al., 2000) treatment to increaseflowering often results in deformed flowersand usually require the combination of bothfor normal flower development. However,we observed that low dose (2.5 mm) of GA is effective in promoting flowering withoutdeleterious effects to flower development. Lackof flower deformities may also be attributed tothe GA treatment being applied months beforeflower development. This long period betweentreatment and response has been previouslyobserved in Cypripedium x Glenarm andCypripedium x Maudiae (Smith, 1958).

Application of BA treatments promotedvegetative growth instead offlowering and thiseffect was alleviated by the addition of GA

3-

We observed that the majority of floweringpseudobuibs did not produce new vegetativeshoots, and in pseudobulbs that did producenew vegetative shoots inflorescence emer-gence was delayed. In Phalaenopsis, flowerprimordial elongation promoted by GA, isfully prevented by BA treatments (Chen etal., 1997).

A working hypothesis of flowering in Mi!-toniopsis may be that GA, application can pro-mote uniform inflorescence emergence throughthe increase in GA in the floral meristem andprevents the development of vegetative shootshowever; this will require further investigation.From this study we conclude that GA 3 alone iseffective in promoting inflorescence emergencein Miltoniopsis.

Literature Cited

Baker, C. and M. Baker. 1993. Miltoniopsis. Amer.Orchid Soc. Bul. 62:794-799.

Bernier, G., A. Havelange, C. Houssa, A. Petitjean,and P. Lejeune. 1993. Physiological signals thatinduce flowering. Plant Cell 5:1147-1155.

Chen,W.S., H.Y. Lie, Z.H. Liu, L. Yang, and W.H.Chen. 1994. Gibberellin and temperature influ-ence carbohydrate content and flowering inPhalaenopsis. Physiol. Plant. 90:391-395.

Chen, W.S., H.Y. Chang, W.H. Chen, and Y.S. Lin.1997. Gibberellic acid and cytokinin affectPhalaenopsis flower morphology at high tem-perature. HortScience 32:1069-1073.

Goh, C.J. 1985. Flowering in tropical orchids. Proc.Eleventh World Orchid Conf. p.166-173.

Goh, C.J., M.S. Strauss, and J. Arditti. 1982. Flowerinduction and physiology oforchids, p.214-241.In: J. Arditti (ed.). Orchid biology: Reviewsand Perspectives. vol. 2. Cornell Univ. Press,Ithaca, N.Y.

Hawaii Department of Agriculture, AgricultureDevelopment Division. 2004. Market outlookreport. Hawaii's potted orchids. Hawaii Dept.Agr. Honolulu.

Hew, C.S. and P.E. Clifford. 1993. Plant growthregulators and the orchid cut-flower industry.Plant Growth Regulat. 13:231-239.

Karaguzel, 0., I. Baktir, S. Cakamakci, and V. Orta-

Fig. 3. Percentage of Bert Field 'Eileen' plants with visible inflorescences following treatment with 0(control) or 2.5 mM GA soil drenches on 17 Nov 2004. Plants were monitored weekly from 8 Feb.2005 to 17 May 2005.

134 HORTSCIENCE VOL. 41(1) FEBRUARY 2006

cesme. 2004. Growth and flowering response ofLupinus varius L. to paclobutrazol. HortScience39:1659-1663.

Larson, R.A. 1980. Introduction to floriculture.Academic Press, Orlando, Fla.

Lopez, R.G., E.S. Runkle, and R.D. Hems. 2005.Flowering of the orchid Milloniopsis Augres'Trinity' is influenced by photoperiod and tem-perature. Acta Hort. 683:175-179.

Lu, Z.X., M. Wu, C.S. Loh, C.Y. Yeong, and C.J.Goh. 1993. Nucleotide sequence of a flower-specific MADS box cDNA clone from orchid.Plant Mol. Biol. 23:901-904.

Matsui, N. and K. Yoneda. 1997. Effect of summertemperatures on growth and flowering of Mi/to-nia. J. Jpn. Soc. Hort. Sci. 66:597-605.

Mudalige, R.G. and A.R. Kuehnle. 2004. Orchidbiotechnology in production and improvement.HortScience. 39:11-17.

Royal Horticultural Society. 2005a. The intema-

tional orchid register. 8 Aug. 2005. http://www.rhs.org.uklplants/registerpages/orchiddetails .asp?lD=75845.

Royal Horticultural Society. 2005b. The interna-tional orchid register. 8 Aug. 2005. http://www.rhs.org.uklplants/registerpages/orchiddetails .asp?1D29 176.

Sakai, W.S., C. Adams, and G. Braun. 2000. Pseudo-bulb injected growth regulators as aids for yeararound production of Hawaiian Dendrobiumorchid cutfiowers. Acta Hort. 541:215-220.

Smith, D.E. 1958. Effect of gibberellins on certainorchids. Amer. Orchid Soc. Bul. 27:742-747.

Su, W.R., W.S. Chen, M. Koshioka, L.N. Mander,L.S. Hung, W.H. Chen, Y.M. Fu, and K.L.Huang. 2001. Changes in gibberellin levels inthe flowering shoot of Phalaenopsis hybridaunder high temperature conditions when flowerdevelopment is blocked. Plant Physiol. Biochem.39:45-50.

Sweet, H.R. 1978. The Milionia complex inhorticul-ture. Amer. Orchid Soc. Bul. 47:917-925.

U.S. Department of Agriculture, National Agricul-tural Statistics Service. 2005. Floriculture Crops2004 Summary. USDA, Wash., D.C.

Wang,Y.T. andT.Y. Hsu. 1994. Flowering and growthofPhalaenopsis orchids following growth retar-dant applications. I-IortScience 29:285-288.

Yu, H., and C. J. Goh. 2000a. Differential geneexpression during floral transition in an orchidhybrid Dendrobium Madame Thong-In. PlantCell Rpt. 19:926-931.

Yu, H., and C. J. Goh. 2000b. Identification andcharacterization of three orchid MADS-boxgenes of the API/AGL9 subfamily during floraltransition. Plant Physiol. 123:1325-1336.

Yu, H., T. Ito, Y. Zhao, J. Peng, P. Kumar, and E.M.Meyerowitz. 2004. Floral homeotic genes aretargets of gibberellin signaling in flower develop-ment. Proc. NatI. Acad. Sci. 101:7827-7832.

HORTSC!ENCE VOL. 41(1) FEBRUARY 2006 135