Botanical Studies (2011) 52: 183-189.
PHYSIOLOGY
Ethephon treatment promotes flower formation in bougainvillea
Fang-Yin LIU and Yu-Sen CHANG*
Department of Horticulture, National Tai-wan University, Taipei, Tai^wan, ROC (Received May 17, 2010; Accepted October 11, 2010)
ABSTRACT. Bougainvillea (Bougainvillea spp.) is an economically important ornamental flower in sub­tropical and tropical regions. This study examined bougainvillea shoots of different developmental stages, e.g., vegetative shoot, flowering shoot stage 1 with fully-developed thorn-inflorescence axis (FS1), flowering shoot stage 2 with visible flower bud (FS2), and flowering shoot stage 3 with blooming shoot (FS3) following their treatment with ethephon (2-chloroethylphosphonic acid). Experimental results indicated that ethephon treat­ment of bougainvillea's vegetative shoot accelerates its shoot maturity and enhances flower formation. The same treatment also increases endogenous ethylene production of the vegetative shoot, subsequently facilitat­ing flower formation whereby the endogenous ACC content is lower than that of reproductive shoots (FS1, FS2, and FS3). Moreover, the ethephon treatment of reproductive bougainvillea shoots increases the ACC content beyond that of the vegetative shoot. Therefore, reproductive shoots produced more ethylene than veg­etative shoots, subsequently inhibiting the development of flowers or even causing serious abscission of flower buds and leafs. This reveals that the role of ethylene in regulating the flowering control of bougainvillea is bi­directional. Results of this study demonstrate the significance of shoot maturity in the growth and flowering of the bougainvillea in which ethylene plays a major role.
Keywords: ACC content; Bougainvillea spp.; Ethephon; Ethylene; Flower formation; Shoot developmental stages.
Abbreviations: ACC, 1-aminocyclopropene-1-carboxylate; Ethephon, 2-chloroethylphosphonic acid; FS1, Flowering shoot stage 1 with the thorn-inflorescence axis developed fully; FS2, Flowering shoot stage 2 with visible flower bud; FS3, Flowering shoot stage 3 with blooming shoot.
INTRODUCTION
Bougainvillea (Bougainvillea spp.), a valued ornamen­tal shrub-vine used in landscaping, is distributed from hot sunny areas to cool damp coastal regions worldwide. In Europe and North America, bougainvillea is also popu­lar as a potted plant and in hanging baskets (Hackett and Sachs, 1967; Hackett et al., 1972). Various environmental conditions in which natural flowering of bougainvillea may occur include those of short photoperiods (Hackett and Sachs, 1968), low night temperatures (Hackett and Sachs, 1966; Norcini, 1993), high light intensity (Hackett and Sachs, 1968), water deficit (Henrard, 1976), shoot bending (Liu and Chang, 2011) and plant growth regulator use, e.g., chlormequat, daminozide (Hackett and Sachs, 1967), ancymidol (Criley, 1977), and dikegulac (Norcini et al., 1992; Norcini and Aldrich, 1994). However, some of these inductive conditions, e.g., water deficit and shoot bending, trigger ACC synthase gene expression, subse-
quently increasing ACC production and ultimately aug­menting ethylene biosynthesis (Botella et al., 2000; Steed et al., 2004; Trusov and Botella, 2006).
As a gaseous hormone, ethylene is involved in the se­nescence of many plant vegetative organs and flowers, the ripening of fruits, and the enhancement of geophyte flowering (Halevy, 1995). Ethylene accelerates maturation of the Dutch iris, inducing small bulbs to bloom earlier, though it has no obvious effect on large bulbs or on the production of ACC (Imanishi et al., 1994; Botha et al., 1998). The treatment of spring barley with the ethylene-releasing agent ethephon enhances shoot maturity and increases their number of tillers (Dathe, 1992). The appli­cation of highly-concentrated ethylene promotes the veg­etative growth of wheat, soy beans, lettuce, and potatoes, causing the flowers to bloom 10 days earlier than untreated ones (Wheeler et al., 1996). Ethylene is also responsible for the transfer from the vegetative to the flowering stage in pineapple (Min and Bartholomew, 1997; Van de Poel et al., 2009). That ethylene plays a role in promoting vegeta­tive growth in some plants is mentioned above, but most plants' flower and flower bud abscission are also highly
*Corresponding author: E-mail: yschang@ntu.edu.tw; Tel: +886-2-33664856; Fax: +886-2-33664855.
184
Botanical Studies, Vol. 52, 2011
sensitive to the hormone. Such plants include: rose (Batista et al., 2009; Macnish et al., 2010), Christmas cactus (Serek and Reid, 1993), bougainvillea (Chang and Chen, 2001), geranium (Cameron and Reid, 2001), hibiscus (Reid et al., 2002), and kalanchoe (Zeddy et al., 2003). Ethylene trans-port can thus be bi-directional in regulating the flowering of some plants.
For several species of azalea, shoots older than 15 weeks respond to temperature, photoperiod, and Cycocel treatments (Shanks and Link, 1968) with a higher flower density than those of younger shoots. Mango shoots 8 weeks and older are more responsive to lower tempera­tures in forming flower buds than 2 or 4 week-old shoots are (Nunez-Elisea and Davenport, 1995). According to Ramina et al. (1979), the dry/fresh weight ratio and the content of soluble substances of bougainvillea increase with an increasing leaf area and with a larger number of developing inflorescences. This observation reveals that an increased assimilate accumulation in the reproductive shoots enhances flowering in bougainvillea, and indicates that the branch growth of woody plants must reach a cer­tain maturity before the flower bud forms.
The bougainvillea inflorescence originates from a de­terminate shoot adjacent to an indeterminate vegetative axillary bud at each node (Figure 1). A thorn-inflorescence refers to a typical thorn containing a developing axis. The fully developed axis is defined as inflorescence hereafter (Hackett and Sachs, 1967). Although bougainvillea has axillary buds accompanying the growth of shoots, the shoot with accelerated growth is non-flowering. Abortion of the inflorescences at various stages of shoot develop-ment is a conspicuous phenomenon in bougainvillea. It was previously mentioned that the bending of bougainvil-lea shoots increases the flowering of buds, the blossom size of flowers and the endogenous ACC content. Shoot bending also resulted in greater ethylene production, caus­ing earlier maturation and flowering. Ethylene may be an important factor in the flowering of bougainvillea (Liu and Chang, 2011). However, which shoot developmental stages of ethylene-sensitive are the least studied. The aim of this research, then, is to elucidate how shoot develop­mental stages and ethephon affect the flower formation of bougainvillea. The results will provide a basis for future research on the control of flowering in bougainvillea.
MATERIALS AND METHODS
Plant material
One-year-old seedlings of potted 'Taipei Red' bougain-villea were obtained from a commercial bougainvillea nursery and planted in 7-inch pots filled with 2,900 mL medium, composed of field soil and peat in a ratio of 7:3. The seedlings were on average 54.2 cm tall with a mean of 16.2 nodes. During the experimental period, the plants were thoroughly watered every 1 to 3 days, when the sur­face of the medium appeared slightly dry. Each pot was fertilized monthly with 3 g of 14-14-14 Osmocote.
Effect of ethephon on shoot developmental stages
The shoots were first categorized into several classes (Figure 1). Vegetative shoots that exhibited strong growth with prolific and dense leaves. Their florets did not de­velop fully on the thorn-inflorescence axis; peduncles became thorns. Flowering shoot stages (FS1 to FS3) were characterized as follows: FS1) fully developed thorn-inflorescence axes and florets with elongated peduncles that remained soft and with a tendency towards reproduc­tive growth; FS2) visible flower buds and well-developed, FS3) flower buds in full bloom on the blooming shoot. Plants at each of these four described shoot developmental stages were sprayed with 75 mg L-1 ethephon (2-chloro-ethylphosphonic acid). Ethephon was sprayed once, 50 mL per each pot. After treatment, the plants were grown in a greenhouse where the shoot developmental stage-specific effect of ethephon on flower formation, flower drop and leaf drop could be observed. Each developmental stage was represented by five potted plants. The control plants were at the vegetative shoot stage and received no ethep-hon treatment.
1-Aminocyclopropene-1-carboxylate (ACC) con­tent
ACC measurements were determined from 1 cm in-ternodes segments of the tested plants (cut from 10 cm below the apical bud). The method developed by Lizada and Yang (1979) was modified to perform the analyses. All samples were washed in test tubes with 5 mL of 80% EtOH for subsequent extraction in a hot water bath at 70°C for 20 minutes, followed by centrifuging. This procedure was repeated twice, and the mixture of the two extracts was further concentrated in a vacuum until it became anhydrous. Distilled water was then added to the concen­trated sample to a final volume of 1 mL. The prepared
Figure 1. Sketch map of different stages of shoot development in bougainvillea (A) Florets on thorn-inflorescence axis do not fully develop, and peduncle becomes a thorn (B) Thorn-inflores­cence axis fully develops, peduncle elongates and remains soft (C) Flowering shoot with visible flower bud (D) Flowering shoot with fully blooming shoot.
Liu and Chang ― Shoot developmental stages of bougainvillea
185
samples were stored in test tubes at 0°C to be analyzed within two weeks.
To perform the analyses, 0.5 mL supernatant was mixed
with 0.1 mL HgCl2 (50 mM) twice: 0.1 mL ACC (100 mM) was added to one system; nothing was added to the other. Their final volumes were each brought to 1.8 mL with distilled water; the mixture was placed in test tubes sealed with sleeve stoppers. While the tubes were sub-merged in crushed ice, 100 [iL of a mixture (2:1, v/v) of iced 5% NaOCl and saturated NaOH was added to each test tube. The contents were vortexed for 5 seconds and then each tube was returned to the crushed ice for 2.5 minutes. They were then vibrated for 1 second and 1 mL of the gas was extracted for analysis using a GC-14A gas chromatograph (Shimazdu, Japan).
Ethylene production rate
Three leaves previously treated with ethephon were detached from three samples (replicates) for each stage of shoot development on days 1, 3 and 7, and were then incu­bated in a 25 mL sealed plastic jar at temperatures ranging from 20-28°C for 2 h. Following incubation, air samples were taken from the headspace for ethylene analysis by a Shimadzu GC-14A gas chromatograph. Ethylene produc­tion rates were calculated and expressed as nL g-1 h-1.
Experimental design and statistical analyses
During the experiment, weekly records were made of the number of nodes and time of the first flower bud, num­ber of flower buds, flower drops, flower bud drops and leaf drops. The experimental design was based on complete randomized design (CRD). The results were statistically analyzed based on analysis of variance (ANOVA) to test the least significant difference (LSD) for evaluating wheth­er the results of various treatments differ from each other (P<0.05). CoStat 6.2 (CoHorrt Software, Monterey, CA, USA) was used for conducting the analyses and SigmaPlot 8.0 (Systat software, Inc., Richmond, CA, USA) was used for graphic plotting of the results.
RESULTS
Effect of ethephon on flower formation
Shoots at various degrees of maturity (Figure 1) were treated using the ethylene-releasing agent ethephon in or­der to observe how ethylene affected shoot developmental stages of bougainvillea. Bougainvillea treated with ethep-hon during the vegetative shoot stage resulted in a short­ened flower formation time and an increase in the number of flower buds (19.3 days and 5.4 flower buds, respectively (Table 1) compared to the untreated control group.
Effect of ethephon on flowering
During the vegetative shoot stage, bougainvillea treated with ethephon had more flower buds and flowers than the untreated control group. Plants treated with ethephon dur­ing the vegetative shoot stage and the FS1 stage with fully developed thorn-inflorescence axes exhibited 0% flower and flower bud drop. The application of ethephon during the FS2 stage when flower buds were visable, or the FS3 stage with blooming shoots, resulted in a flower drop of 85% (FS2) and 100% (FS3), ultimately reaching 100% after 7 days; whereas the flower bud drop had already reached 100% by 3 days. Treating the plant with ethephon during FS2 and FS3 stages caused an obvious flower and
Table 1. Effect of ethephon (75 mg L-1) on flower formation at different stages of shoot development in bougainvillea.
Treatment
Mean days to first flower buds
Mean node of first flower buds
Number of flower buds
Control
40.71a2
22.4 a
11.8 b
Vegetative shoot
21.4 b
21.6 a
17.2 a
LSD0.05
3.2
4.1
10.9
1Each value represents the mean of five replicates. 2Significant differences between treatments are designated by letters a and b (LSD test, P<0.05).
Table 2. Effect of ethephon (75 mg L-1) on the flower drop, flower bud drop and leaf drop percentage of different shoot develop­mental stages of bougainvillea.
Treatment
Thorn-inflorescence at treatment
Flower drops (%) Days after treatment
Flower buds drops (%) Days after treatment
Leaf drops (%) Days after treatment
Bloom No.
Bud No.
Total No.
3
7
3
7
3
7
Control
11.81b2
16.6 b
28.4
0.0
c
0.0
0.0
0.0
3.7 d
23.5
c
Vegetative shoot
17.2 a
22.6 a
39.8
0.0
c
0.0
0.0
0.0
7.4 d
20.9
c
FS1
--
--
--
0.0
c
0.0
0.0
0.0
23.7 c
44.9
b
FS2
--
--
--
85.0
b
100.0
100.0
100.0
62.0 b
90.0
a
FS3
--
--
--
100.0
a
100.0
100.0
100.0
100.0 a
100.0
a
LSD0.05
10.9
1.1
―
2.5
―
―
―
11.2
19.1
1Each value represents the mean of five replicates.
2Significant differences between treatments are designated by letters a, b, c and d (LSD test, P<0.05). FS1: Flowering shoot stage 1 with the thorn-inflorescence axis developed fully; FS2: Flowering shoot stage 2 with visible flower bud; FS3: Flowering shoot stage 3 with blooming shoot. Control plant was at the vegetative shoot stage without ethephon treatment.
186
Botanical Studies, Vol. 52, 2011
flower bud drop (Table 2). The leaf drop was insignificant for both the control and for the ethephon treated plants at the vegetative shoot stage. After 3 days, the leaf drop was 3.7% for the control and 7.4% for the treated plants at the vegetative shoot stage; after 7 days, the leaf and flower drop were 23.5%, and 20.9%, respectively. Treating bougainvillea at developmental stages FS1, FS2, and FS3 with 75 mg L-1 ethephon, resulted in a leaf drop of 23.7%, 62.0%, 100%, respectively, after 3 days and 44.9%, 90.0%, 100%, respectively, after 7 days.
ACC content of shoot developmental stages
Vegetative shoots of bougainvillea contained less ACC (0.045 nmole g-1) than the FS1 stage (0.243 nmole g-1), the FS2 (0.295 nmole g-1) and the FS3 stage (0.735 nmole g-1) (Figure 2).
Effect of ethephon on ethylene production
The FS3 stage of bougainvillea contained more ethyl-ene (2.17 nL g-1 h-1) than the FS2 stage (2.01 nL g-1 h-1), the FS1 stage (1.82 nL g-1 h-1), the vegetative stage (1.72 nL g-1 h-1) and the control (1.21 nL g-1 h-1) at 7 days. Ethylene in-creased with an increasing duration of the ethephon treat-ment (Figure 3).
DISCUSSION
Ethephon was applied at four developmental stages of shoots to observe the stage-specific effect of ethylene on bougainvillea flower formation. According to the results, when bougainvillea is in the vegetative growth stage, its ACC content is relatively low. Additionally, spraying
Figure 3. Effect of different stages of shoot development on ethylene production (nL g-1 h-1) treated with ethephon (75 mg L-1). FS1: Flowering shoot stage 1 with the thorn-inflorescence axis fully developed; FS2: Flowering shoot stage 2 with visible flower bud; FS3: Flowering shoot stage 3 with blooming shoot. Control plant was at the vegetative shoot stage without ethephon treatment. The vertical bars represent the mean 士 standard error (n = 3). Significant differences between treatments are desig­nated by letters a, b, c and d (LSD test, P<0.05).
ethephon increases endogenous ethylene production, sub­sequently accelerating maturation of the shoots. When the shoots are in the reproductive growth stage (FS1 to FS3), the increasing ACC content causes the sprayed ethephon to adversely impact shoot development because excessive ethylene leads to serious leaf and flower drop. The above observation indicates ethylene's bi-directional movement in adjusting bougainvillea's flowering.
This phenomenon is related to the observation by Day et al. (2002) that the age and size of woody plants affects their development; in addition, various maturing shoots may have different hormone distributions. Moreover, this observation is also related to nutrient diversion as proposed by Sachs (1977). As is hypothesized, there is competition for nutrients between bougainvillea's young leaves and flowering buds. Notably, a situation in which a nutrient originally destined for the growth of young leaves is directed to a location where flowering buds are develop-ing, suppresses the shoot growth. Tse et al. (1974) men­tioned that treating the bougainvillea, in which all young leaves with PBA (N-benzyl-a-(tetrahydro-2H-pyran-2yl)-adenine) have been removed, causes the plant to increasing accumulation of assimilates at the tip. Ramina et al. (1979) also confirmed that PBA treatment increases the soluble solid and cumulative dry weight of bougainvillea. Thus, the floral axis tips receive information on the accumulation of assimilates, and in addition, the increasing accumula­tion of assimilates facilitates the formation of flowering buds. Li et al. (2000) also noted that the mature shoot of bamboo affects the nutrient distribution within the plant; a larger number of mature shoots increases production. Zhou and Xi (1993) observed that treating the mature shoot with
Figure 2. ACC content (nmole g-1) at different stages of shoot development in bougainvillea. FS1: Flowering shoot stage 1 with the thorn-inflorescence axis fully developed; FS2: Flow­ering shoot stage 2 with visible flower bud; FS3: Flowering shoot stage 3 with blooming shoot. The vertical bars represent the mean 士 standard error (n = 3). Significant differences be­tween treatments are designated by letters a, b and c (LSD test, P<0.05).
Liu and Chang ― Shoot developmental stages of bougainvillea
187
mixtalol causes different photosynthesis activities and production. This observation indicates that responses to chemical reagents for the plant fluctuate at various growth stages.
Treating mustard plants with ethephon at their vegeta­tive growth stage transfers assimilates to their reproductive organs, increases their photosynthesis rate and dry weight and enhances flower formation (Khan, 2005). Ethylene biosynthesis was also promoted in vegetative bud forma­tion in wild-type tobacco (Ma and Li, 2006). According to Lin et al. (2005), a significant amount of ACC of culture medium promotes flowering in bamboo. Some studies have attributed the flowering of Bromeliaceae to the increasing endogenous ethylene production and endogenous ACC content that raises the plant sensitivity to ethylene (Min and Bartholomew, 1993; Min and Bartholomew, 1996). We found similar results with bougainvillea: it had low ACC content during vegetative growth and the application of ethephon enhanced ethylene, thus promoting plant ma­turity and the formation of flowering buds. Bougainvillea contains a higher endogenous ACC content during the re­productive growth stages FS1, FS2, and FS3, than during the vegetative growth stage. Additionally, the application of ethephon causes a serious flower bud, flower and leaf drop, in which ethylene increases with an extended treat­ment. Moreover, treating bougainvillea with STS when its flowers are fully blooming alleviates the problem of flower and leaf drop and increases flower longevity (Chang and Chen, 2001). The present study also confirmed that the use of the inhibitor 1-MCP to treat bougainvillea after flower­ing increases flower longevity (data not shown).
Natural flowering occurs when plants are exposed to inductive stress conditions, e.g., water deficit and shoot bending (Henrard, 1976). According to our results, how­ever, young bougainvillea plants (e.g., vegetative growth stage) are already sensitive to external flowering formation agents (e.g., ethephon or ethylene). Young plants may still need to develop certain sensitivity towards natural flower­ing formation. The above observations are consistent with those of Van de Poel et al. (2009). The sensitivity of an ac­tive ingredient and the magnitude of the evoked response is related to the ethylene receptor and signal transduction physiology (Trewavas, 1991). However, although bou-gainvillea plants at the vegetative shoot stage can sense externally-applied ethylene and transfer the signal result­ing in flowering, they do not yet respond toward natural flowering. From this developmental stage, the ability to synthesize ethylene de novo (at the level of the axillary buds) appears to be a primary controlling factor to respond to natural flowering formation. Importantly, no flowering occurs if young plants can not yet increase their ethylene production (at the level of the axillary buds) in response to natural flowering formation.
The results presented here demonstrate that the devel­opmental stage of bougainvillea shoots significantly af­fects its flower development. With respect to maturity of the shoots, above observations confirm that bougainvillea
has a low ACC content during the vegetative growth peri­od. Applying ethephon at this developmental stage would thus increase ethylene production, as well as promote shoot maturity and flower bud maturity. During the repro國 ductive stages FS1to FS3, these plants have a higher ACC content, explaining why ethylene inhibits the development of flowering buds. Moreover, applying ethephon adversely impacts the subsequent development of flowering buds; excessive ethylene leads to a serious leaf drop and flower drop. Therefore, adequately controlling the response of bougainvillea to ethylene during its different shoot devel­opment stages would greatly facilitate the flower control.
Acknowledgements. This research was supported by Council of Agriculture, Executive Yuan, Taiwan, Repub­lic of China. Dagmar Frisch is appreciated for his editorial assistance.
LITERATURE CITED
Batista, R.J. da Rocha., J.A.S. Grossi, J.I. Ribeiro Junior, and F.L. Finger. 2009. Rose flower longevity in response to ethylene and 1-methylcyclopropene (1-MCP). Acta Hortic. 847: 363-368.
Botella, J.R., A.S. Cavallaro, and C.I. Cazzonelli. 2000. Towards the production of transgenic pineapple to control flowering and ripening. Acta Hortic. 529: 115-122.
Botha, M.L., C.S. Whitehead, and A.H. Halevy. 1998. Effect
of octanoic acid on ethylene-mediated flower induction in Dutch iris. Plant Growth Regul. 25: 47-51.
Cameron, A.C. and M.S. Reid. 2001. 1-MCP blocks ethylene-induced petal abscission of Pelargonium peltatum but the effect is transient. Postharv. Biol. Technol. 22: 169-177.
Chang, Y.S. and H.C. Chen. 2001. Variability between silver thiosulfate and 1-naphthaleneacetic acid applications in pro­longing bract longevity of potted bougainvillea. Sci. Hortic. 87: 217-224.
Criley, R.A. 1977. Year around flowering of double Bougain-villea: effect of daylength and growth retardants. J. Amer. Soc. Hortic. Sci. 102: 775-778.
Dathe, W. 1992. Effects of jasmonic acid and ethephon on tiller­ing to maturity in spring barley. Ann. Bot. 69: 237-241.
Day, M.E., M.S. Greenwood, and C. Diaz-sala. 2002. Age and size related trends in woody plant shoot development: regulatory pathways and evidence for genetic control. Tree
Physiol. 22: 507-513.
Hackett, W.P. and R.M. Sachs. 1966. Flowering in Bougain-villlea 'San Diego Red'. Proc. Amer. Soc. Hortic. Sci. 88:
606-612.
Hackett, W.P. and R.M. Sachs. 1967. Chemical control of flow­ering in Bougainvilllea 'San Diego Red'. Proc. Amer. Soc. Hortic. Sci. 90: 361-364.
Hackett, W.P. and R.M. Sachs. 1968. Experimental separation of inflorescence development from initiation in Bougainvillea.
Proc. Amer. Soc. Hortic. Sci. 92: 615-621.
188
Botanical Studies, Vol. 52, 2011
Hackett, W.P., R.M. Sachs, and J. DeBie. 1972. Growing bou-
gainvillae as a flowering pot plant. Florist Rev. 150: 56-57. Halevy, A.H. 1995. The use of plant bioregulators in ornamental
crops. Acta Hortic. 394: 37-43.
Henrard, G. 1976. Automatic irrigation by the Chapin system. Its application to pot plant culture of Bougainvillea glabra, Eu­phorbia pulcherrima and Stephanotisfloribunda. Bulletin des Recherches Agronomiques de Gembloux. 11: 135-148. (in French, with an English summary)
Imanishi, H., A.H. Halevy, A.M. Kofranek, S. Han, and M.S. Reid. 1994. Respiration and carbohydrate changes during ethylene mediated flower induction in Dutch iris. Sci. Hor-
tic. 59: 275-284.
Khan, N.A. 2005. The influence of exogenous ethylene on growth and photosynthesis of mustard (Brassica juncea)
following defoliation. Sci. Hortic. 105: 499-505. Li, R., M.J.A. Werger, H. de Kroon, H.J. During, and Z.C.
Zhong. 2000. Interactions between shoot age structure, nu­trient availability and physiological integration in the giant bamboo Phyllostachys pubescens. Plant Biol. 2: 437-446.
Lin, C.S., C.C. Lin, and W.C. Chang. 2005. Shoot regeneration,
re-flowering and post flowering survival in bamboo inflo­rescence culture. Plant Cell Tissue Organ Cult. 82: 243-249.
Liu, F.Y. and Y.S. Chang. 2011. Effects of shoot bending on ACC content, ethylene production, growth and flowering of bougainvillea. Plant Growth Regul. 63: 37-44.
Lizada, M.C.C. and S.F. Yang. 1979. A simple and sensitive as­say for 1-aminocyclopropane-1-carboxylic acid. Anal. Bio-chem. 100: 140-145.
Ma, Q.H. and Y.L. Li. 2006. Inhibition of ethylene biosynthesis enhances vegetative bud formation without affecting growth and development of transgenic tobacco plants. J. Plant Growth Regul. 25: 101-109.
Macnish, A.J., R.T. Leonard, A.M. Borda, and T.A. Nell.
2010. Genotypic variation in the postharvest performance and eth-ylene sensitivity of cut rose flowers. HortSci. 45: 790-796.
Min, X.J. and D.P. Bartholomew. 1993. Effects of growth regu­lators on ethylene production and floral initiation of pine­apple. Acta Hortic. 334: 101-112.
Min, X.J. and D.P. Bartholomew. 1996. Effect of plant growth regulators on ethylene production, 1-aminocyclopropane-l-carboxylic acid oxidase activity, and initiation of inflores­cence development of pineapple. J. Plant Growth Regul. 15:121-128.
Min, X.J. and D.P. Bartholomew. 1997. Temperature affects eth-ylene metabolism and fruit initiation and size of pineapple.Acta Hortic. 425: 329-338.
Norcini, J.G. 1993. How to grow a great Bougainvillea. Grower
Talks 62: 62-64.
Norcini, J.G. and J.H. Aldrich. 1994. Flowering response of
Bougainvillea cultivars to dikegulac. HortSci. 29: 282-284.
Norcini, J.G., J.M. McDowell, and J.H. Aldrich. 1992. Effect of
dikegulac on flowering and growth of Bougainvillea 'Rain­bow Gold'. HortSci. 28: 119-121.
Nunez-Elisea, R. and T.L. Davenport. 1995. Effect of leaf age, duration of cool temperature treatment, and photoperiod on bud dormancy release and floral initiation in mango. Sci. Hortic. 62: 63-73.
Ramina, A., W.P. Hackett, and R.M. Sachs. 1979. Flowering in Bougainvillea a function of assimilate supply and nutrition diversion. Plant Physiol. 64: 810-813.
Reid, M.S., B. Wollenweber, and M. Serek. 2002. Carbon bal­ance and ethylene in the postharvest life of flowering hibis­cus. Postharv. Biol. Technol. 25: 227-233.
Sachs, R.M. 1977. Nutrient diversion: an hypothesis to explain the chemical control of flowering. HortSci. 12: 220-222.
Serek, M. and M.S. Reid. 1993. Anti-ethylene treatments for potted christmas cactus-efficacy of inhibitors of ethylene action and biosynthesis. HortSci. 28: 1180-1181.
Shanks, J.B. and C.B. Link. 1968. Some factors affecting growth and flower initiation of greenhouse azalea. Proc. Amer. Soc. Hortic. Sci. 92: 603-614.
Steed, C.L., L.K. Taylor, and M.A. Harrison. 2004. Red light
regulation of ethylene biosynthesis and gravitropism in etio­lated pea stems. Plant Growth Regul. 43: 117-125.
Trewavas, A. 1991. How do plant growth substances work?
Plant Cell Environ. 14: 1-12.
Trusov, Y. and J.R. Botella. 2006. Silencing of the ACC syn­thase gene ACACS2 causes delayed flowering in pineapple (Ananas comosus L. Merr.). J. Exp. Bot. 57: 3953-3960.
Tse, A.T.Y., A. Ramina, W.P. Hackett, and R.M. Sachs. 1974.
Enhanced inflorescence development in bougainvillea 'San Diego Red' by removal of young leaves and cytokinin treat­ments. Plant Physiol. 54: 404-407.
Van de Poel, B., J. Ceusters, and M.P. De Proft. 2009. Determi­nation of pineapple (Ananas comosus, MD-2 hybrid culti-var) plant maturity, the efficiency of flowering induction agents and the use of activated carbon. Sci. Hortic. 120:58-63.
Wheeler, R.M., B.V. Peterson, J.C. Sager, and W.M. Knott.
1996. Ethylene production by plans in a closed environ­ment. Adv. Space Res. 18: 193-196.
Zeddy, K., C.E. Sisler, T. Winkelmann, and M. Serek. 2003.
Efficacy of new inhibitors of ethylene perception in im­provement of display life of Kalanchoe (Kalanchoe bloss-feladiana Poelln.) flowers. Postharv. Biol. Technol. 30:169-176.
Zhou, W.J. and H.F. Xi. 1993. Effects of mixtalol and pa-clobutrazol on photosynthesis and yield of rape (Brassica
napus). J. Plant Growth Regul. 12: 157-161.
Liu and Chang ― Shoot developmental stages of bougainvillea
189
益收生長素促進九重葛花芽之形成
劉芳吟 張育森
國立台灣大學園藝學研究所
九重葛為熱帶及亞熱帶重要的觀賞盆花。以不同枝條成熟度的九重葛枝條(營養生長枝條、刺花序
軸肥大的枝條、花苞可見的枝條、已開花枝條)處理益收生長素(ethephon)，觀察不同枝條成熟度對九
重葛生長及開花之影響。結果顯示：九重葛在營養生長時期，施用ethephon可以加速枝條成熟，促進
九重葛的花芽形成，顯示出乙烯會促進九重葛的花芽形成，且因營養生長時期其內生ACC含量低於生
殖生長階段，故此時處理ethephon可提高九重葛內生乙烯含量而達到促進花芽形成之效果；而在生殖
生長時期(刺花序軸肥大、花苞可見和盛花)，因此時內生ACC含量高於營養生長階段，故此時處理
ethephon會因過多的乙烯而抑制花芽發育，反而不利之後花苞的發育，甚至會造成嚴重的落苞及落葉現
象。故推論在不同枝條成熟度處理乙烯對九重葛花芽形成有不同的影響，在營養生長時期乙烯可促進九
重葛花芽形成，但在生殖生長時期則否，在九重葛花期調節上具有雙向之作用。由以上結果可得知枝條
成熟度的時期對九重葛的花芽形成甚為重要，而乙烯扮演一關鍵之角色。
關鍵詞：ACC含量；九重葛；益收生長素；乙烯；花芽形成；枝條成熟度。