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.
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.
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: firstname.lastname@example.org
SIBEL MANSUROGLU ET AL.,
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.,
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.,
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 &
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.,
Table 3. Effect of paclobutrazol on some flower characteristics of C. orientalis.
(mg⋅L-1) Pedicel length
(cm) Length (including spur)
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, p≤0.05 level.
Table 4. Effect of paclobutrazol on leaf and flower colorimetric values in C. orientalis.
(mg⋅L-1) L* Chroma
Hue (°) L* Chroma
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.
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
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(Received for publication 3 November 2003)