ArticlePDF Available

Abstract

Effect of paclobutrazol on flowering characteristics, leaf and flower colour of Consolida orientalis (Gay) Schröd., native to South Anatolia (Turkey) was investigated. Seeds were directly sown into soil under unheated greenhouse and natural photoperiod conditions on 17 January and paclobutrazol at concentrations of 0 (control), 125, 250 and 500 mg·L-1 was applied to plants as foliar spray, when 5% of plants had elongated first internodes. Paclobutrazol had no significant effect on the time from sowing to flowering. Plant height, length and internode length of main and secondary inflorescences, pedicel length and the number of secondary inflorescence significantly reduced with increasing concentrations of paclobutrazol. Flower number on main inflorescence at concentration of 250 mg·L-1, and stem diameter and flower number on secondary inflorescence at concentration of 500 mg·L-1 increased compared with control treatment. Paclobutrazol decreased lightness (L*) and colour saturation (chroma) values of leaves and lightness (L*) of flowers. Plants treated with paclobutrazol had darker green leaves and deeper violet flowers than that of control plants.
Pak. J. Bot., 41(5): 2323-2332, 2009.
EFFECT OF PACLOBUTRAZOL ON FLOWERING, LEAF AND
FLOWER COLOUR OF CONSOLIDA ORIENTALIS
SIBEL MANSUROGLU, OSMAN KARAGUZEL*, VELI ORTACESME
AND M. SELCUK SAYAN
Department of Landscape Architecture, Faculty of Agriculture,
Akdeniz University, 07070 Antalya, Turkey.
Abstract
Effect of paclobutrazol on flowering characteristics, leaf and flower colour of Consolida
orientalis (Gay) Schröd., native to South Anatolia (Turkey) was investigated. Seeds were directly
sown into soil under unheated greenhouse and natural photoperiod conditions on 17 January and
paclobutrazol at concentrations of 0 (control), 125, 250 and 500 mg·L-1 was applied to plants as foliar
spray, when 5% of plants had elongated first internodes. Paclobutrazol had no significant effect on the
time from sowing to flowering. Plant height, length and internode length of main and secondary
inflorescences, pedicel length and the number of secondary inflorescence significantly reduced with
increasing concentrations of paclobutrazol. Flower number on main inflorescence at concentration of
250 mg·L-1, and stem diameter and flower number on secondary inflorescence at concentration of 500
mg·L-1 increased compared with control treatment. Paclobutrazol decreased lightness (L*) and colour
saturation (chroma) values of leaves and lightness (L*) of flowers. Plants treated with paclobutrazol
had darker green leaves and deeper violet flowers than that of control plants.
Introduction
Turkey is one of the unique countries in the world in terms of plant genetic resources
and diversity (Tan, 1998). The rich plant genetic resources have provided raw materials
such as primitive land races, wild crop relatives and plant species as new sources to
improve agricultural production worldwide. Flora of Turkey is also rich for
Ranunculaceae family, particularly the species of genus Delphinium L., and Consolida
(DC.) S.F. Gray (Davis, 1965) that some of them have real potential to be used as raw
breeding material or new floricultural crops.
Consolida orientalis (Gay) Schröd. is medium to tall, stickily-hairy annual with
simple or branched stems 20-74 cm in length and laciniae numerous and linear-setaceous
leaves (Davis, 1965; Blamey & Grey-Wilson, 1998). Flowers are purplish-violet, 18-26
mm, borne in a fairly dense raceme; flower stalks shorter than the lower dissected bracts;
spur 10-12 mm long (Blamey & Grey-Wilson, 1998; Burnie, 2000). It is one of
Consolida species used in cut flower trade as dried and fresh cut flower crops and in
bedding plant designs (Armitage, 1995; Brickell & Zuk, 1997; Armitage, 2001). In
landscape surveys of Cevizli district (Antalya, South Anatolia, Turkey), a native
population of C. orientalis was observed with higher plant height, longer main and
secondary inflorescences, and higher flower numbers in comparison to samples of C.
orientalis described previously from Anatolia (Karaguzel et al., 2006). Responses of this
population to culture conditions including sowing time, growing conditions and
photoperiod treatments were investigated (Karaguzel et al., 2007; Karaguzel et al., 2009).
Results of this studies indicated that this native population has a tendency to bending in
greenhouse growing and plant height is slightly higher for using in bedding plant design.
Breeding the plant for more useful form ought to be the primary goal of a long-term study
and previous studies state that a plant growth retardant could be effective for obtaining
sturdy plant and reducing plant height in several species without decreasing flowering
quality (Larson, 1985; Davis et al., 1988; Karaguzel & Ortacesme 2002).
*Corresponding author E-mail: okaraguzel@akdeniz.edu.tr
SIBEL MANSUROGLU ET AL.,
2324
Paclobutrazol, an inhibitor of gibberellin biosynthesis or action, can significantly
retard plant growth and accelerate flowering at certain doses in several woody, perennial
and annual plants, such as Bouwardia humboldtii Hum., and Bougainvillea glabra Choisy
(Wilkinson & Richards, 1987; Karaguzel & Ortacesme, 2002), a local variety of
Pelargonium zonale L. and Pelargonium x hortorum L.H. Bailey (Cox, 1991; Nasr,
1995), and Cosmos bipinnatus Cav. and Zinnia elegans Jacq. (Mohd et al., 1988; Chen et
al., 1993). It is also utilized in order to produce compact, sturdy potted and bedding
plants, to enhance the green colour of the foliage, to strengthen flower stem and to
promote resistance of foliage to environmental stresses (Halevy, 1986). Although growth
reduction effect of paclobutrazol is common, growth reduction percentage, flowering,
leaf area and chlorophyll content, flower shape and colour responses of plants to this
chemical can vary depending on the dose or concentration, method, site of application,
species and cultivar and also growing season (Barrett & Bartuska, 1982; Menhennett,
1984; Heursel & Witt, 1985; Davis et al., 1988; Qrunfleh & Suwwan, 1988; Ripka &
Szanto, 1988; Davis & Andersen, 1989; Keever & Cox, 1989; Lee & Lee, 1990; Nasr,
1995; Karaguzel, 1999; Banon et al., 2002). With respect to the needs of ornamental
plant industry, there is limited scientific information on the responses of Ranunculaceae
members to paclobutrazol in general and on the response of C. orientalis in particular,
except a study on Anemone blanda Schott & Kotschy which stated that soil drench
application of paclobutrazol reduced excessive stem elongation in the warm greenhouse
conditions (van Leeuwen & Dop, 1990).
The objective of this study was to investigate the effect of paclobutrazol on
flowering characteristics, leaf and flower colour of C. orientalis native to South Anatolia
under unheated plastic greenhouse and natural photoperiod conditions.
Material and Methods
Plant material: In this study, plants propagated from seeds collected from a native
population of C. orientalis in Cevizli (altitude 1200 m) district of Antalya province
(South Anatolia, Turkey) were used as plant material. Seeds were harvested in July 2001,
and non-standard seeds were discarded in the laboratory. The selected seed lots were
dusted with captan and stored at room temperature under conditions of relative humidity
until sowing dates.
Experimental site and procedures: Experiment was carried out in an unheated plastic
greenhouse at the Research and Application Station of the Faculty of Agriculture, Akdeniz
University, Antalya, Turkey (36º 53' N, 30º 42' E), between January and May 2002.
Greenhouse soil was a loam having a pH of 7.6, and consisted of 16.4% of CaCO3,
1.6% of organic matter, and 50.2 and 81.7 mg·kg-1 of available phosphorus (P) and
potassium (K), respectively. The soil was solarized for two months during June and July
2002, and dug 20 cm in depth two weeks before sowing. Then, 12 plots measuring
1.2*0.6 m-2 were prepared with 0.5 m distances and they were assigned to four
paclobutrazol concentrations with three replicates within completely randomized
experimental design (Gomez & Gomez, 1984). Five days before sowing date, the dose of
composed fertilizer (15:15:15; N:P:K) at 30 g·m-2 was applied to experimental plots and
mixed with the soil to a depth of 20 cm on 17 January 2002. Three sowing lines 1.5-2 cm
in depth were prepared in each experimental plot with a distance of 20 cm, and 2 g seeds
per 100 cm sowing line were sown considering the results of previous germination tests
and suggestions for culture lines of C. orientalis (Armitage, 1995). On 24 February 2002,
EFFECT OF PACLOBUTRAZOL ON CONSOLIDA ORIENTALIS 2325
seedlings were reduced to ~7.5 cm distances between plants on sowing lines and
provided a planting density of 45 plants per square meter, when seedlings reached to 5-
7.5 cm height. Plants were watered by hand as needed and grown without applying any
additional fertilizer or pesticide during growing period. When 5% of the plants had
elongated first internodes, paclobutrazol at concentrations of 0 (control), 125, 250 and
500 mg·L-1 was applied to plants as a foliar spray with minimal runoff on 28 March 2002.
The concentrations were obtained by diluting a concentrated suspension of paclobutrazol
and control plants were sprayed with an equal amount of tap water.
Data collection: Air temperatures and photosynthetically active radiation (PAR, in 400-700
nm) were recorded in the greenhouse during experimental period. Plant heights were
measured from 4 April to 2 May at one-week intervals. Days to flower (first 2-5 basal
flowers opened on the main inflorescences of 50% of plants) were estimated relative to
sowing date. Plant height at flowering (height from soil to top of plant) and stem diameter
(10 cm above the soil) were measured on the dates when 90% of flowers on the main
inflorescences were opened. At the same growth stage, measurements on length (length
from connecting point with stem to the top of inflorescence), diameter (5 cm above the
connecting point of inflorescence with stem) and internode length (mean of first tree
internode lengths) were made and flower numbers were counted in the main inflorescences.
For determining the flower characteristics, pedicel length, corolla diameter and corolla
length (including spur) were also measured at the same growth stage. When all flowers of
the first three secondary inflorescences opened, secondary inflorescence numbers were
counted and data was also gathered on secondary inflorescence length and internode length,
diameter and flower number as described for main inflorescences. For the colour
measurements, leaf and flower samples were taken in the middle part of stems and main
inflorescences when all flowers on the main inflorescences opened. In the measurements,
CIELAB L*, a* and b* coordinates were used. Colour coordinates in leaves and corollas
were measured with a calibrated Minolta CR-200 colorimeter at mid point of the leaves and
corollas. Chroma (colour saturation) was calculated as (a*2+b*2)1/2 and the hue angle was
calculated as (arctan b*/a* in degree).
Data analysis: Data on the changes in the plant heights were plotted with standard error
(SE) using Microsoft Excel software. The remaining data relating to the characteristics
considered in this study were analyzed by ANOVA using SPSS 9.0 for Windows and
means were compared using Duncan’s multiple range tests at a significance level of 5%.
Results and Discussion
Plant growth and main inflorescence characteristics: Monthly average greenhouse
temperatures and daily total photosynthetically active radiation (PAR, in 400-700 nm)
measured in greenhouse in January, February, March and May were 16.8°C and 6.18
mol·m-2·d-1, 18.8°C and 9.09 mol·m-2·d-1, 19.7°C and 10.76 mol·m-2·d-1 and 20.5°C and
12.74 mol·m-2·d-1, respectively. Data show that the inhibitory effect of paclobutrazol on
plant height could be seen seven days after treatments (in measurement on 4 April) with
slight differences between concentrations (Fig. 1). Two weeks after treatments,
significant differences were observed in plant height, and plants treated with
paclobutrazol continued to grow with shorter plant heights throughout the experimental
period compared to control plants with significant differences between concentration at
125 mg·L-1 and concentrations at 250 and 500 mg·L-1 (Fig. 1).
SIBEL MANSUROGLU ET AL.,
2326
0
10
20
30
40
50
60
70
80
90
4 Apr.
11 Apr.
18 Apr.
25 Apr.
2 Ma
y
Measurement date
Plant height (cm)
Fig. 1. Effects of paclobutrazol on plant height in C. orientalis [ Control (), 125 mg·L-1 (), 250
mg·L-1 (S), 500 mg·L-1 (¯)]. Vertical bars represent standard error (SE) when larger than the symbols.
The ANOVA results showed no significant effect (P=0.952) induced by
paclobutrazol treatment on days to flower and plants treated with different paclobutrazol
concentrations flowered within 90.7or 91.3 days after sowing (Table 1). Previous studies
reveal that the days to flower responses of plant species and cultivars to paclobutrazol are
quite different. Paclobutrazol did not affect days to flowering in Episcia cupreata (Hook.)
Hanst.Pink Panther’, P. x hortorum ‘Tours Truly’ and Angelonia angustifolia Benth.
(Stamps & Henny, 1986; Tayama & Carver, 1990; Miller & Armitage, 2002). Ecker et
al., (1992) found that while the time to flowering in Matthiola incana (L.) R. Br.
‘Lavender’ increased with increasing paclobutrazol concentrations; flowering time of
‘Midget-Red’ was not affected. In contrast, paclobutrazol reduced the time to flowering
in P. zonale and promoted early flowering in Z. elegans (Chen et al., 1993; Nasr, 1995).
Foliar sprays of paclobutrazol significantly affected plant height (p<0.001), main
inflorescence length (p<0.001) and internode length of main inflorescence (P=0.014).
Data on these characteristics indicated that paclobutrazol led to a linear reduction in the
height or the length of measured plant attributes, with a greater effect being observed at
increasing concentrations (Table 1). While the mean highest plant height was recorded
85.7 cm for control plants, mean plant height in the plants treated with 500 mg·L-1
paclobutrazol decreased to 39.8 cm with a reduction rate of 215.3%. Similar decreasing
trends were recorded in length and internode length of main inflorescences with the
reduction rates of 214.8% and 184.6%, respectively (Table 1). These reduction rates can
be interpreted to indicate C. orientalis is more sensitive to spray application of
paclobutrazol than some of other plant species such as Camellia X williamsii W.W. Sn.,
Lupinus varius L., and B. glabra (Wilkinson & Richards, 1988; Karaguzel & Ortacesme,
2002; Karaguzel et al., 2004).
EFFECT OF PACLOBUTRAZOL ON CONSOLIDA ORIENTALIS 2327
Results indicated that paclobutrazol treatments had slight but significant effect
(P=0.039) on plant stem diameter, but had no effect (P=0.429) on main inflorescence
diameter (Table 1). In the plant stem diameter values, significant difference was only
recorded at concentration of 500 mg·L-1 in which plant stem diameter significantly
increased compared to other concentrations including control treatment. However,
paclobutrazol treatments had no significant effect on main inflorescence diameter. In L.
varius, it was found that paclobutrazol applied either foliar spray or soil drench resulted
in increases in both stem and main inflorescence diameters (Karaguzel et al., 2004).
Flower numbers of the main inflorescence were significantly affected by
paclobutrazol treatment (P=0.030) (Table 1). With an increase in the concentration of
paclobutrazol, flower numbers increased. However, the highest flower numbers were
obtained with the second concentration (250 mg·L-1). Previous studies indicate that the
effects of paclobutrazol on flower number could vary due to plant species, dose and
method of application. It was stated that spray treatments increased, while drench
treatments reduced the total number of open flowers in C. X williamsii (Wilkinson &
Richards, 1988). Matsoukis et al., (2001) found that the number of flowers per plant
increased to a maximum as drenched paclobutrazol concentration increased to 80 mg·L-1,
but higher concentrations resulted in a decrease in the number of flowers per plant in a
subspecies of Lantana camara L. Results are quite similar to findings of previous studies
that spray application of paclobutrazol at 250 mg·L-1 concentration increased the number
of flowers compared to control treatments in B. glabra and L. varius (Karaguzel &
Ortacesme, 2002; Karaguzel et al., 2004).
Secondary inflorescence characteristics: Secondary inflorescence growth and
characteristics are also important in determining ornamental value for these kinds of plants
species. The ANOVA results indicated that paclobutrazol treatments had significant effect
(P=0.019) on the number of secondary inflorescences per plant (Table 2). The number of
secondary inflorescences linearly decreased with increasing concentrations of
paclobutrazol. While the highest number of secondary inflorescencewas counted in control
plants with 9.1 inflorescences/plant, this value decreased to 7.1 inflorescences/plant in the
plants treated with paclobutrazol at 500 mg·L-1 (Table 2). Previous studies state that branch
and shoot or secondary inflorescence responses of plants to paclobutrazol could also vary
depending on species or cultivar, dose or concentration and application method. Davis et
al., (1988) reported that triazoles had little effect on shoot number per plant in some plants
species, but in others shoot number was substantially reduced. Paclobutrazol applied as a
soil drench inhibited lateral shoot production in Plectranthus australis R. Br. (Wang &
Blessington, 1990) and increased lateral shoot numbers in Gardenia jasminoides Ellis (De
Baerdemaeker et al., 1994). Application of paclobutrazol either as media drench or foliar
spray resulted in an increase in the number of lateral shoots per plant in Bougainvillea
spectabilis Willd. (Karaguzel, 1999), but spray treatments increased and media drenches
reduced lateral shoot production in B. glabra ‘Sanderiana’ (Karaguzel & Ortacesme, 2002).
As in the main inflorescences, spray treatment of paclobutrazol at different
concentrations resulted in significant and linear decreases in lengths and internode
lengths of secondary inflorescences (Table 2). The secondary inflorescences were 32.1
cm long on average in control plants. In the plants treated with 500 mg·L-1 paclobutrazol,
this value decreased to 21.5 cm with a reduction rate of 149.3%, and similar decreasing
trend was recorded in internode length with a reduction rate of 175.0%. In contrast,
number of flowers on secondary inflorescences increased with increasing paclobutrazol
SIBEL MANSUROGLU ET AL.,
2328
concentrations and the highest flower numbers (21.4 flowers/inflorescence) were counted
in plants treated with 500 mg·L-1 paclobutrazol (Table 2). However, paclobutrazol
treatment had no significant effect (P=0.673) on secondary inflorescence diameter as
being recorded for main inflorescences. Reduction rates in length and internode length of
secondary inflorescences were lower than that of main inflorescences. Concentration, in
which the highest flower numbers were counted, was also higher in secondary
inflorescences. These differing responses are possibly due to the consumption of
paclobutrazol absorbed via leaves first mainly for reducing plant height and length of
main inflorescence in the relatively short time and less amount of paclobutrazol remained
to reduce inflorescence length and increase flower number in secondary inflorescences.
Therefore higher concentration of paclobutrazol was needed to reduce length and
increase flower number in secondary inflorescences.
Flower characteristics: Data on flower characteristics showed that paclobutrazol
treatments significantly affected pedicel lengths (Table 3). As in the height and length
related characteristics considered in this study, pedicel lengths were linearly decreased with
increasing concentrations of paclobutrazol. While mean pedicel length in control plants was
1.7 cm, this value decreased to 1.2 cm in the plants treated with 500 mg·L-1 paclobutrazol
with a reduction rate of 141.7%. However, paclobutrazol treatments did not result in
significant differences in corolla diameters and lengths (including spurs) (Table 3). Results
from previous studies indicate that paclobutrazol reduced length of peduncles in
Callistephus chinensis (L.) Nees, Calendula officinalis L., Portulaca grandiflora Hook.and
G. jamesonii (Qrunfleh & Suwwan, 1988; Lee & Lee, 1990), and the length of pedicel in
Hibiscus rosa-sinensis L., (Wang & Gregg, 1991). Flower size responses of plants to
paclobutrazol can vary depending on species and cultivars. Qrunfleh & Suwwan (1988)
reported that paclobutrazol reduced flower diameters in P. grandiflora, but flower sizes in
C. chinensis and C. officinalis were not affected. Also, it is stated that paclobutrazol
treatments resulted in significant decreases in flower diameter in cultivars of Rhododendron
simsii Planch., and Rhododendron obtusum (Lindl.) Planch. (Heursel & Witt, 1985; Keever
et al., 1990), and had no significant effect on flower size in H. rosa-sinensis (Wang &
Gregg, 1991).
Leaf and flower colours: Data on leaf colorimetric values indicated that paclobutrazol
treatment significantly affected L*(lightness) and chroma (colour saturation) values of
leaves, but it had no significant effect (P=0.125) on hue angle (Table 4). At all
paclobutrazol concentrations, L* values of leaves significantly decreased compared with
control treatment without significant differences between concentrations at 125, 250 and
500 mg·L-1 (Table 4). At the same time, paclobutrazol treatments at 125 and 250 mg·L-1
significantly decreased chroma values of leaves related to control plants, but there was no
significant difference in chroma values measured in control plants and plants treated with
paclobutrazol at 500 mg·L-1 (Table 4). As a result, it can be concluded that paclobutrazol
produced darker foliage in C. orientalis. In general, similar results are mentioned by
Halevy (1986) and Davis et al., (1988). It is also reported that paclobutrazol intensified
leaf colour in Azalea, Fuchsia L. and Poinsettia (Witt, 1986), darkened the foliage in
different cultivars of R. simsii (Heursel & Witt 1985), increased chlorophyll content in G.
jamesonii (Lee & Lee, 1990), and produce a darker foliage in Dianthus caryophyllus L.
‘Mondriaan’ (Banon et al., 2002).
EFFECT OF PACLOBUTRAZOL ON CONSOLIDA ORIENTALIS 2329
SIBEL MANSUROGLU ET AL.,
2330
Table 3. Effect of paclobutrazol on some flower characteristics of C. orientalis.
Corolla
Concentration
(mgL-1) Pedicel length
(cm) Diameter
(cm) Length (including spur)
(cm)
Control 1.7 a 2.1 2.1
125 1.6 ab 2.1 2.0
250 1.4 bc 2.1 2.0
500 1.2 c 2.2 1.9
Probability > F
Concentration 0.003 0.715 0.078
Mean separation within columns by Duncan’s multiple range test, p0.05 level.
Table 4. Effect of paclobutrazol on leaf and flower colorimetric values in C. orientalis.
Leaf Flower
Concentration
(mgL-1) L* Chroma
Hue (°) L* Chroma
Hue (°)
Control 38.04 a 23.49 a 147.38 40.72 a 35.44 302.93
125 33.56 b 16.41 b 146.79 37.67 ab 34.78 302.37
250 33.35 b 16.64 b 147.67 36.80 ab 34.94 301.20
500 33.93 b 18.18 ab 146.57 35.43 b 34.27 301.40
Probability > F
Concentration <0.001 <0.001 0.125 0.018 0.853 0.189
L* = Lightness, Chroma = Saturation (a*2+b*2)1/2, Hue (°) = Arctan (b*/a*).
Mean separation within columns by Duncan’s multiple range test, p 0.05 level.
Paclobutrazol had significant effect (P=0.018) on only L* (lightness) values of
flowers and there were no significant differences in chroma and hue angle values of
flowers caused by paclobutrazol treatments (Table 4). L* values of flowers linearly
decreased with increasing concentration of paclobutrazol, but chroma values and hue
angles (in degree) were constant with slight and non significant differences at all
concentrations (Table 4). However, paclobutrazol treatments resulted in deeper violet
flowers with lower L* values than that of control plants. Previous studies showed that
flower colour responses of plants to paclobutrazol can also vary with plant species and
growing season. Paclobutrazol can intensify flower colour in Azalea, Fuchsia and
Poinsettia without reducing the size of flowers (Witt, 1986), but did not affect blossom
colour of some R. simsii cultivars (Heursel & Witt, 1985). Banon et al., (2002) found that
paclobutrazol significantly affected flower colour of D. caryophyllus ‘Mondriaan’ in
winter cycle of cultivation, whereas there were no significant differences caused by
paclobutrazol treatments in flower colorimetric values of flowers in spring cultivation.
Taking the results of this study as a whole, it is evident that C. orientalis is growth,
flowering and leaf and flower colour sensitive to spray application of paclobutrazol. This
chemical can easily be used to produce sturdy plants with reduced excessive plant
growth, increased flower numbers and darkened leaf and flower colours in C. orientalis.
Acknowledgement
This study was supported by the Administration Unit of Scientific Research Projects
of Akdeniz University (Project No. 21.01.0104.09).
EFFECT OF PACLOBUTRAZOL ON CONSOLIDA ORIENTALIS 2331
References
Armitage, A.M. 1995. Specialty cut flowers. Timber Press, Portland, Oregon.
Armitage, A.M. 2001. Armitage’s manual of annuals, biennials, and half-hardy perennials. Timber
Press, Portland, Oregon.
Banon, S.A., E.A. Gonzalez, J.A. Cano, J.A. Franco and Fernandez. 2002. Growth, development
and color response of potted Dianthus caryophyllus cv. Mondriaan to paclobutrazol treatment.
Scientia Horticulturae, 94: 371-177.
Barrett, J.E. and C.A. Bartuska. 1982. PP333 effects on stem elongation dependent on site of
application. HortScience, 17: 737-738.
Blamey, M. and C. Grey-Wilson. 1998. Mediterranean Wild Flowers. HarperCollins, London.
Brickell, C. and J.D. Zuk. 1997. A-Z Encyclopedia of Garden Plants-The American Horticultural
Society. DK Publishing Inc., New York.
Burnie, D. 2000. Wild flowers of the Mediterranean. Dorling Kindersley, London.
Chen, C.L., G.J. Keever and C.F. Deneke. 1993. Growth and flowering of triazole-treated Zinnia
(Zinnia elegans) and Marigold (Tagetes erecta). Plant Growth Regulat. Soc. of Amer.-Qrtly.,
21: 169-179.
Cox, D.A. 1991. Gibberellic acid reverses effects of excess paclobutrazol on Geranium.
HortScience, 26(1): 39-40.
Davis, P.H. 1965. Ranunculaceae. In: Flora of Turkey and The East Aegean Islands. (Ed.): P.H.
Davis. Vol 1, Edinburgh University, Edinburgh, United Kingdom, pp. 94-134.
Davis, T.D., G.L. Steffens and N. Sankha. 1988. Triazole plant growth regulators. In: Horticultural
Reviews. (Ed.): J. Janick. Vol. 10, pp. 63-105.
Davis, T.D. and A.S. Andersen. 1989. Growth retardants as aids in adapting new floricultural crops
to pot culture. Acta Horticulturae, 252: 77-85.
De Baerdemaeker, C.I., J.M. van Huylenbroeck and P.C. Debergh. 1994. Influence of paclobutrazol
and photoperiod on growth and flowering of Gardenia jasminoides Ellis cultivar 'Wetchii'.
Scientia Horticulturae, 58: 315-324.
Ecker, R., A. Barzilay, L. Afgin and A.A. Watad. 1992. Growth and flowering responses of
Methiola incana L. R. Br. to paclobutrazol. HortScience, 27: 1330.
Gomez, K.A. and A.A. Gomez. 1984. Statistical Procedures for Agricultural Research. Second
Edition, John Wiley & Sons, New York.
Halevy, A.H. 1986. Recent advances in the use of growth substances in ornamental horticulture.
Plant Growth Substances 1985, Heidelberg, Berlin, West Germany, pp. 391-398.
Heursel, J. and H.H. Witt. 1985. Bonzi-a new growth regulator for evergreen azaleas. Deutscher
Gartenbau, 39(37): 1742-1746.
Karaguzel, O. 1999. The effects of paclobutrazole on growth and flowering of Bougainvillea
spectabilis WİLLD. Turkish Journal of Agriculture and Forestry, 23 (Supplement 2): 527-
532.
Karaguzel, O. and V. Ortacesme. 2002. Influence of paclobutrazol on the growth and flowering of
Bougainvillea glabra ‘Sanderiana’. Ziraat Fakultesi Dergisi, Akdeniz Universitesi, 15(1): 79-
84.
Karaguzel, O., I. Baktir, S. Cakmakci and V. Ortacesme. 2004. Growth and flowering responses of
Lupinus varius L. to paclobutrazol. HortScience, 39(7): 1659-1663.
Karaguzel, O., S. Mansuroglu, M.S. Sayan and E. Yildirim. 2006. Relations between different
native ecological conditions and growth and flowering characteristics of Consolida orientalis
Populations. Ziraat Fakultesi Dergisi, Akdeniz Universitesi, 19(2): 235-244.
Karaguzel, O. S. Mansuroglu, M.S. Sayan and S.G. Tascioglu. 2007. Effects of growing conditions
and sowing time on the growth and flowering characteristics of native Consolida orientalis
Population. Ziraat Fakultesi Dergisi, Akdeniz Universitesi, 19(2): 235-244.
Karaguzel, O. S. Mansuroglu, M.S. Sayan, E. Yildirim and A. Benliay. 2009. Effects of
photoperiod and sowing times interaction on growth and flowering of Consolida orientalis
native to South Anatolia. Acta Horticulturae, 807: 681-686.
SIBEL MANSUROGLU ET AL.,
2332
Keever, G.J. and D.A. Cox. 1989. Growth inhibition in Marigold following drench and foliar-
applied paclobutrazol. HortScience 24: 390.
Keever, G.J., W.J. Foster and J.C. Stephenson. 1990. Paclobutrazol inhibits growth of woody
landscape plants. Journal of Environmental Horticulture, 8(1): 41-47.
Larson, R.A. 1985. Growth regulators in floriculture. In: Janick J. (Ed.), Hortcultural Reviews Vol.
7, pp. 400-481.
Lee, P.O. and J.S. Lee. 1990. Effects of ancymidol and paclobutrazol on growth and flowering of
potted gerbera. Journal of the Korean Society for Horticultural Science, 31(3): 300-304.
Matsoukis, A.S., A. Sereli-Chronopoulou, I.D. Dimopoulus and A. Kamoutsis. 2001. Responses of
Lantana camara subsp. camara to paclobutrazol and shading. Canadian Journal of Plant
Science, 81(4): 761-764.
Menhennett, R. 1984. Comparison of a new triazole retardant paclobutrazol (PP 333) with
ancymidol, chlorphonium chloride, daminozide and piproctanyl bromide on stem extension
and inflorescence development in Chrysanthemum morifolium Ramat. Scientia Horticulturae,
24(3-4): 349-358.
Miller, A. and A.M. Armitage. 2002. Temperature, irradiance, photoperiod and growth retardants
influence greenhouse production of Angelonia angustifolia Benth. Angel Mist Series.
HortScience, 37: 319-321.
Mohd, A., S. Gauri, A.K. Muthoo, M. Ahmad and G. Shanker. 1988. Effect of paclobutrazol on
growth and flowering of Cosmos (Cosmos bipinnatus). Punjab Horticultural Journal, 28: 105-
108.
Nasr, M.N. 1995. Effects of methods of application and concentrations of paclobutrazol on
Pelargonium zonale (L) as a pot plant. Alaxandria Journal of Agricultural Research, 40(3):
261-279.
Qrunfleh, M.M. and M.A. Suwwan. 1988. Response of three summer annuals to paclobutrazol
application. Advances in Horticultural Science, 2(1): 15-18.
Ripka, G. and B. Szanto. 1988. Studies on the effect of a new growth regulator on greenhouse
ornamentals. Novenyvedelem, 24(9): 415-418.
Stamps, R.H. and R.J. Henny. 1986. Paclobutrazol and night interruption lighting affect Episcia
growth and flowering. HortScience, 21: 1005-1006.
Tan, A. 1998. Current status of plant genetic resources conservation in Turkey. In: Zincirci N., Z.
Kaya, Y. Anikster, W.T. Adams (Eds.). The Proceedings of International symposium on In
Situ Conservation of Plant Genetic Diversity, Central Research Institute for Field Crops,
Ankara.
Tayama, H.K. and S.A. Carver. 1990. Zonal geranium growth and flowering responses to six
growth regulators. HortScience, 25: 82-83.
van Leeuwen, P.J. and A.J. Dop. 1990. Effects of storage, cooling and greenhouse conditions on
Anemone blanda, Fritillaria meleagris and Oxalis adenophylla for use as pot plant. Acta
Horticulturae, 266: 101-107.
Wang, Y.T. and T.M. Blessington. 1990. Growth of four tropical foliage species treated with
paclobutrazol and uniconazole. HortScience, 25(2): 202-204.
Wang, Y.T. and L.L. Gregg. 1991. Modification of hibiscus growth by treating unrooted cuttings
and potted plants with uniconazole or paclobutrazol. Journal of Plant Growth Regulation,
10(1): 47-51.
Wilkinson, R.J. and D. Richards. 1987. Effects of paclobutrazol on growth and flowering of
Bouvardia humboldtii. HortScience, 22: 444-445.
Wilkinson, R.J. and D. Richards. 1988. Influence of paclobutrazol on the growth and flowering of
Camellia x Williamsii. HortScience, 23(2): 359-360.
Witt, H.H. 1986. Bonzi promises economy. Deutscher Gartenbau, 40(6): 239-243.
(Received for publication 3 November 2003)
... The vegetative growth suppression will direct the translocation of nutrient supply and photosynthate products to meristematic areas, which will initiate flower formation [7]. PBZ application was reported very effective in suppressing vegetative growth, increasing and accelerating flowering of both annual and perennial plants [8]. ...
... Gibberellins play a role in the process of cell elongation so that the application of PBZ results in shorter internodes and shoots [15,10]. This growth inhibition will direct the translocation of nutrient supply and photosynthate products to meristematic areas, which will initiate flower formation [8]. The stability of increasing the shoots number in each harvest period is needed to reduce fluctuations in yields in each harvest period. ...
... (Table 3). Chlorophyll content decreased again in year II, both in control and PBZ treatments compared to year I (0.16-0.22%), but some PBZ treatments had higher chlorophyll content than control, especially in PBZ treatment of 2500 ppm (8 WAH) and 5000 ppm (8,14 and 16 WAH). Chlorophyll content in year III (2016) was almost the same in year II (2015), ranging from 0.08-0.15%. ...
Article
Full-text available
The main problem in clove cultivation is yield fluctuation which occurred every 2-4 years. It is usually caused by internal factors such as photosynthates, nutrition, and plant growth regulators that control the flowering process. The study was conducted from January to December 2015 on +30 years old-cloves at a farmer’s plantation in Sumedang, West Java. The trial was arranged in a randomized block design with three replications. The treatment consisted of 13 treatments of paclobutrazol application: (1) control, (2) 2500 ppm paclobutrazol, given eight weeks after harvest (WAH); (3) 2500 ppm paclobutrazol, 10 WAH, (4) Paclobutrazol 2500 ppm, 12 WAH. (5) 2500 ppm paclobutrazol, 14 WAH, (6) Paclobutrazol 2500 ppm, 16 WAH, (7) Paclobutrazol 2500 ppm, 18 WAH, (8) 5000 ppm paclobutrazol, 8 WAH, (9) Paclobutrazol 5000 ppm, 10 WAH, (10) 5000 ppm paclobutrazol, 12 WAH, (11) Paclobutrazol 5000 ppm, 14 WAH, (12) 5000 ppm paclobutrazol, 16 WAH, and (13) 5000 ppm paclobutrazol, 18 WAH. Results indicated that paclobutrazol 5000 ppm applied at 16 WAH gave a higher new shoot number and yield than control within three consecutive years (2014, 2015, and 2016). The range of chlorophyll content was 0.08-0.15%.
... A plant growth regulator belonging to the triazole family, paclobutrazol has been proven to shield a number of crops against environmental stressors such as heat radiation, drought, and cold. By inhibiting the synthesis of ent-kaurene in the metabolic pathway involved in gibberellin manufacturing, paclobutrazol prevents the creation of gibberellins, which reduces the quantity of active gibberellins produced and, as a consequence, reducing internodal growth and inhibits the stem elongation (Mansuroglu et al., 2009;Ahmad et al., 2014;Tesfahun, 2018 andArya andFatmi, 2022). ...
... Similarly, Mansuroglu et al., 2009;Ahmad et al., 2014;Tesfahun, 2018 ...
... Rademacher (2000) reported that CCC is a plant growth retardant regulating the plant height physiologically mainly through reducing cell elongation and cell division. Plant growth retardants reduce unwanted shoot elongation through inhibition of the formation of growth active gibberellins (Mansuroglu et al., 2009). Present study corroborated with earlier findings. ...
... It clearly indicated that CCC reduced the number of tendrils might be due to arresting the apical dominance and reducing the shoot elongation through anti-gibberellin activity. Mansuroglu et al. (2009) reported that most plant growth retardants inhibit the formation of growth active gibberellins and can thus be used to reduce unwanted shoot elongation. Present study corroborated with earlier findings. ...
Article
Background: Horsegram is considered as poor man’s crop and it has high nutritive value for human being. Apart from its photo and thermo sensitive in nature, formation of tendrils with excessive vegetative growth is major constraints and reason for poor yield. The tendrils act as sink and utilize photo-assimilates for its continuous growth. Hence, a strategy is required for reduction of vegetative growth and tendril formation for yield improvement. The current study is aimed to enhancement of yield in horsegram through physiological approach. Methods: An experiment was conducted to study the impact of plant growth regulators and nutrients viz., brassinolide (1 ppm), CCC (250 ppm), nutrient consortium (K2SO4 (0.5%) + MAP (0.5%) + FeSO4 (0.5%) + boric acid (0.3%) and TNAU Horsegram Wonder (1%) on growth, physiological traits and yield of horsegram (Macrotyloma uniflorum) variety Paiyur 2 under rainfed condition during 2018 - 2020. Plant growth regulators and nutrient consortium were used as foliar spray at flowering stage (50 days after sowing) under field condition. Result: TNAU Horsegram Wonder showed supremacy to enhance photosynthetic rate, SPAD value, soluble protein and yield compared to other treatments. Early flowering and reduced number of tendrils were observed in CCC nutrient consortium and TNAU Horsegram Wonder treatments. Foliar spray of 1% TNAU Horsegram Wonder recorded highest SPAD value of 22.8 which is on par with BL nutrient consortium. Highest photosynthetic rate of 16.94 µmol m-2 s-1 and lowest number of tendrils (2.6) were registered by 1% TNAU Horsegram Wonder. Foliar application of TNAU Horsegram Wonder at flowering stage registered highest grain yield of 1090 kg ha-1 and increased yield of 23% over control with BC ratio of 2.24.
... Among them, paclobutrazol has gained popularity in tree fruit crops. Growth retardants often work by inhibiting the formation of growth-active gibberellins (GAs), which helps reduce unwanted shoot elongation (Singh, 2004;Mansuroglu et al., 2009) [27,19] . Besides controlling growth, these chemicals can also be employed in ornamental crops to enhance foliage color, strengthen flower stems, stimulate flowering, and improve resistance against environmental stresses (Kahar, 2008) [14] . ...
... Among them, paclobutrazol has gained popularity in tree fruit crops. Growth retardants often work by inhibiting the formation of growth-active gibberellins (GAs), which helps reduce unwanted shoot elongation (Singh, 2004;Mansuroglu et al., 2009) [27,19] . Besides controlling growth, these chemicals can also be employed in ornamental crops to enhance foliage color, strengthen flower stems, stimulate flowering, and improve resistance against environmental stresses (Kahar, 2008) [14] . ...
Article
Full-text available
The investigation titled "Effect of growth retardants on dwarfism and flowering of papaya (Carica papaya L.) cv. GJP 1" was conducted at the Fruit Research Station, Lalbaug, Junagadh Agricultural University, Junagadh during the year 2022-23. The experiment followed a Randomized Block Design with three replications and included 10 treatments: T1 (Control), T2 (Ethrel 150 ppm), T3 (Ethrel 250 ppm), T4 (Ethrel 350 ppm), T5 (Cycocel 750 ppm), T6 (Cycocel 1500 ppm), T7 (Cycocel 3000 ppm), T8 (Paclobutrazol 250 ppm), T9 (Paclobutrazol 500 ppm), and T10 (Paclobutrazol 1000 ppm). The results of the study showed that the treatment with Cycocel 3000 ppm resulted in the smallest plant height (142.44 cm), shortest average internodal length (2.87 cm), lowest bearing height (63.97 cm), height of the plant at the time of bearing (105.90 cm), leaf stalk length (46.51 cm), and shortest time to first flowering (61.83 days) and first fruit set (66.61 days). Additionally, this treatment exhibited a male-to-female ratio (plant) of 0.89 and the highest number of leaves (33.74).
... Paclobutrazol is a growth retardant which interferes with the biosynthesis of gibberellins a classical plant hormone that promote vegetative growth in plants. Paclobutrazol treated plants caused the level of gibberellins to decline in plant, as a result, stem elongation was inhibited and the plants became shorter in height (Hua et al. 2014;Jagadhane et al. 2016;Kim, 1991;Mansurgolu et al. 2009;Setia et al. 1995) [3,4,5,6,8] . Paclobutrazol modified the canopy structure of a plants by enhancing the number of branches (primary, secondary and tertiary) (Setia et al., 1995) [8] . ...
... Calendula grows up 60 cm in height and produces large yellow and orange flowers. Flowers are harvested continuously and new flowers are formed after the harvest [1][2][3][4]. In other words, continuous harvesting of flowers is possible as long as climate conditions are available. ...
Article
A field experiment was carried out to investigate the effect of different method of applying Paclobutrazol on plant growth and flower yield of Calendula (Calendula officinalis L.) cv. Bon Bon, during November 2022 to February 2023 at Floriculture Research Field, Department of Horticulture, Sam Higginbottom University of Agriculture Technology and Sciences, Pryagraj (U.P.). Different methods of applying Paclobutrazol viz., T0 No Treatment, T1 Paclobutrazol@ 50 ppm as Foliar application, T2 Paclobutrazol@ 100 ppm as Foliar application, T3 Paclobutrazol@ 150 ppm as Foliar application, T4 Paclobutrazol@ 200 ppm as Foliar application, T5 Paclobutrazol@ 50 ppm as Soil drenching, T6 Paclobutrazol@ 100 ppm as Soil drenching, T7 Paclobutrazol@ 150 ppm as Soil drenching and T8 Paclobutrazol@ 200 ppm as Soil drenching was applied to assess the vegetative, floral and yield characteristics of Calendula . The experiment was laid out in complete randomised block design with nine treatments and three replications. The result for growth and flower yield of Calendula (Calendula officinalis L.) showed significant difference for the various treatment applied as soil application as a paclobutrazol as well as foliar application. In general paclobutrazol@ 200 ppm as Soil drenching and foliar application improved the different growth and flower yield parameters suggest its efficacy of application. in comparison to plants that had other treatments applied, the plant's height is reduced, making it smaller and more dwarflike, and the number of lateral branches is increased, increasing the flower yield. When compared to foliar application, the soil drenching method of application was found to be more effective because plant roots absorb more of the substance. This is because plants are less capable of absorbing the substance because of higher rates of evapotranspiration in foliar application.
... The result of our study was partially according to the latter, the application of PBZ was found to reduce the P. lactiflora flower diameter in S3 and S4. When the flower color was considered, treatment of P. lactiflora with PBZ was found to yield lighter violet flowers than that of the control, not consistent with Consolida orientalis [38]. However, the loss of flower color was observed in the other plant growth retardants, for example, spraying Chrysanthemum morifolium with daminozide exhibited a significant loss of color [39], and applying prohexadione-Ca was found to significantly decrease the petal coloration of Rosa hybrida [40], associated with the reduction in anthocyanin. ...
Article
Full-text available
Herbaceous peony (Paeonia lactiflora Pall.) is an important ornamental plant worldwide. In its natural state, P. lactiflora often manifests traits like rapidly elongating internodal growth, loose plant types, and soft inflorescence stems. However, very little has been known about the measures for controlling these traits. This study investigated the effect of applying paclobutrazol (PBZ) on the plant growth and flower quality in P. lactiflora. The results indicated that PBZ application reduced the plant height (8.05%), plant crown width (14.72%), and leaf area (10.90%), but increased the leaf thickness (18.18%) and stem diameter (over 11%) in P. lactiflora. Meanwhile, PBZ application was also found to increase the chlorophyll (Chl) a (29.63%), Chl b (33.33%), Chl a+b (30.56%), SPAD (27.32%), relative water content (0.47%), soluble sugar (5.09%) and activities of three antioxidant enzymes (superoxide dismutase 169.66%, peroxidase 3.59%, catalase 319.30%), but decreased the relative electrical conductivity (18.52%). Additionally, the application of PBZ was found to affect the flowering quality of P. lactiflora, increasing the flower diameter and fresh weight only in the flower-bud stage. This initiates the bloom stage, where there was a decrease in the total content of the aromatic compounds except for the flower-bud stage, and faded the flower color by reducing the content of anthocyanin. These results demonstrated that the application of PBZ can regulate the P. lactiflora plant types with no significant decrease in its ornamental values. This might provide a theoretical basis for further applying PBZ in P. lactiflora for use in urban landscape spaces.
Chapter
Although Xanthostemon chrysanthus (F. Muell.) Benth. is not a local species, it is often preferred as an ornamental tree in Malaysian cities due to its unique yellow inflorescence. Previous studies have shown that X. chrysanthus was able to grow in sub-optimal urban soils. However, under local climate conditions, the flowering of the species is unpredictable and always less abundant than in its native range. Thus, an experiment to evaluate the potential of paclobutrazol (PBZ) and potassium nitrate (KNO3) for improving the flowering of the species was conducted. Three dosages of PBZ (0, 0.125, and 0.25 g/L/tree) and KNO3 (0, 100, and 200 g/tree) were combined and tested on X. chrysanthus aged approximately six years old after planting at Metropolitan Batu Park, Kuala Lumpur. PBZ application was made only once by soil drenching, in the early stages of the experiment in March 2012. The first application of KNO3 was carried out concurrently with PBZ treatment, and the following application was repeated at three-month intervals, i.e. in June 2012, September 2021, and December 2012. Inflorescence size was significantly bigger with 0.125 g/L PBZ coupled with 100 g KNO3 than that of other treatments. However, mean flower abundance was significantly improved with 0.25 g/L PBZ combined with 100 g KNO3. Our previous studies also noted that tree height and leaf size were decreased with the presence of PBZ, however, no abnormal leaf formation was observed, suggesting that the PBZ dosages used were appropriate for the species. Treatment with 0.25 g/L PBZ coupled with 100 g KNO3 potentially improves the flower abundance without detrimental effects, thus increasing the attractive appearance of X. chrysanthus trees.
Article
Full-text available
Plant height and lateral shoot growth of Camellia × Williamsii ‘Waterlily’ and ‘Debbie’ were controlled effectively by foliar sprays or media drenches of paclobutrazol. A single foliar application of 500 mg·liter –1 paclobutrazol reduced height of both cultivars by ≈30%, and plants were considered commercially acceptable. The response did not carry over into subsequent years. Some rates of paclobutrazol increased the total number of open flowers, but there was a varied effect on flower abscission. Paclobutrazol treatment could prove a useful technique for the commercial production of camellias for temporary use as indoor flowering pot plants before subsequent planting in the landscape. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1 H -1,2,4-triazole-1-ethanol (paclobutrazol, ICI-PP333).
Article
Full-text available
Chemical growth retardants commonly are applied to bedding plants to produce more compact plants and extend marketability (4). Paclobutrazol (PP333), a gibberellin biosynthesis inhibitor currently labeled for use on poinsettia, has been effective in retarding growth of numerous flowering pótted crops (2,5), foliage plants (3), and annual bedding plants (1).
Article
Full-text available
Episcia cupreata (Hook.) Hanst. ‘Pink Panther’ plants were drenched with 0, 0.07, or 0.21 mg a.i. paclobutrazol and given night interruption lighting (NIL) of 4 hr (2200-0200 hr) at 2.6 μmol·s ⁻¹ ·m ⁻² or no light interruption. Paclobutrazol and NIL did not affect days to first flowering, while flower numbers per plant increased exponentially over time on paclobutrazol-treated and control plants. NIL increased flowers per plant from day 47 on. Flower longevity was greater on paclobutrazol-treated plants than controls. Plant size (canopy radius) was reduced by paclobutrazol, which caused a greater flower density per canopy area. Chemical name used: ( R *, R *)-(±) β-[(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-1 H -l,2,4-triazole-1-ethanol (paclobutrazol).
Article
Full-text available
The effects of paclobutrazol were examined in respect to the growth and flowering of Bougainvillea spectabilis WILLD under conditions of long and short natural photoperiods. In the middle of July and at the beginning of November, doses of paclobutrazol; 0 (control), 10, 20, 30 and 50 mg a.e./pot soil drench, and 0 (control), 125, 250, 500 and 1000 ppm foliage spray, were applied to plants grown in 18 cm pots (h=16.5 cm). With the application of paclobutrazol in the form of soil drench and foliage spray, the time from application to flowering decreased slightly under the long photoperiod conditions but this effect did not occur under short photoperiod conditions. Paclobutrazol in the form of soil drench and foliage spray greatly decreased the length of shoots, decreased the number of flowers per plant and increased the number of shoots per plant even at the lowest doses and concentrations with both long and short photoperiods. It was found that the duration of growth suppression was greater when paclobutrazol was applied in the form of soil drench.
Article
Full-text available
Container-grown Phaseolus vulgaris L. and Chrysanthemum morifolium Ramat. were treated with the growth retardant PP333 [(2RS, 3RS)-l-(4-chlorophenyl)- 4,4-dimethyl-2-l,2,4-triazol-l-yl-)pentan-3-ol] by applying the chemical to the soil, whole shoot, mature leaves, or stem. Regardless of application site, PP333 resulted in reduced stem elongation compared to untreated plants. However, more retardation occurred when the chemical was applied to the stem than when applied to the leaves. Results indicated that in foliar applications the chemical taken up by the stem was more important than that contacting the leaves.
Article
Paclobutrazol, applied as a spray or drench, suppressed growth of 8 woody landscape species. Magnitude of growth inhibition was directly correlated with application rate, whereas both magnitude and duration of growth inhibition was influenced by application method. Generally, paclobutrazol when applied as a drench suppressed growth to a greater degree than did spray applications. Flowering or fruiting of 3 species was generally promoted with paclobutrazol, while phytotoxicity symptoms were observed on 4 species.
Chapter
The use of plant growth regulators (PGR) for the manipulation of growth and development in ornamentals is more common than in most other commercial crops. The number and variety of practical uses to which PGR can be put, is also probably greater in ornamentals than in food and plantation crops relative to the very small percentage of the total agricultural and horticultural growing area. There are several reasons for this: (1) the number and variety of cultivated ornamental species are probably greater than the total of all other cultivated plants. (2) The cropping of cut flowers and potted plants often has to be accurately timed for specific occasions, such as pointsettias for Christmas and Lilium longiflorum for Easter. (3) The shape of the plants contributes to their ornamental value, i.e., size and color of flowers and foliage, length and strength of stems, branching pattern, etc. These traits can be manipulated by PGR. (4) Flowers and flowering potted-plants are very vulnerable and are often short-lived. Flowers are often harvested and shipped in the bud stage and are intended to continue to develop even after being purchased by the customer. PGR are used both to promote flower development and opening and to extend their longevity. (5) There are two economical factors which justify the extensive use of PGR in ornamentals. First, since ornamentals are luxury commodities, their relatively high prices can cover the cost of certain treatments, such as those with PGR that are too expensive to use for food crops. Second, it is probably easier to secure official clearance for the use of new PGR in ornamentals than in edible crops.