Effect of Planting Density and Gibberellic Acid on Quantitative and Qualitative
Characteristics of Solidago canadensis Tara in Egypt
Amira R. Osman
Demand on Solidago has been rising dramatically over the past few years.
Solidago canadensis L.cv. Tara belongs to family Asteraceae and grows
as wild flower in North America, Asia and Europe. It is widely used as a landscaping
flowering plant, as an excellent cut flower arrangements and bouquets with high
post harvest durability and as a dried flower. This study was carried out to
determine the response of S. canadensis L.cv. "Tara" to five Gibberellic
Acid (GA3) concentrations (control zero, 50, 100, 200 and 400 ppm)
as foliar spray and two planting densities (16 and 32 plants m-2)
and interactions between them in an attempt to increase its landscape value,
its quality as a cut flower production for reaching to maximum export value
and increase its offsets production value as a vegetative propagation method
under Egyptian conditions. The results revealed that stem height, stem circumference,
fresh and dry weight, total leaves area plant-1, inflorescence length,
percentage inflorescence length stem-1, number of flowering branches
inflorescencestem plant-1, flowering branches length inflorescence-1,
vase life, total chlorophyll and carotene contents of leaves increased significantly
by reducing planting density. While, significant delay from (120 to 125 days)
in flowering occurred due to increasing planting density. Application of 200
ppm GA3 significantly increased stem height, inflorescence length,
percentage inflorescence length stem-1 and flowering branches length
inflorescence-1, while GA3 had no effect on flowering
date. Application of 400 ppm GA3 significantly decreased stem circumference,
fresh and dry weight, number of leaves plant-1, total leaves area
plant-1, number of flowering branches inflorescencestem plant-1
and total chlorophyll. The plants treated by combination of GA3 at
100 ppm with 16 plants m-2 density recorded the best in terms of
almost all characters studied. With respect to almost all characteristics, we
can recommend that the best results were recorded in plants treated by combination
GA3 at 100 ppm with 16 plants m-2.
Received: September 02, 2013;
Accepted: November 23, 2013;
Published: March 08, 2014
Floriculture has become a profitable sub-sector of agribusiness throughout
the world in recent years. The export trade in floriculture has grown substantially
to become one of Egypt's major foreign exchange generating ventures. Quality
and yield improvement are important aims of florists. These problems can be
rectified by optimizing the production conditions and utilization of plant growth
regulators (PGRs). Solidago canadensis L.cv. "Tara" belongs to family
Asteraceae and is native to North America and Mexico (Walck
et al., 2001). It is a wild plant but also appreciated as a landscaping
easily managed plant, as an excellent cut flower with high post-harvest durability
and as a dried flower. Cultivation is preferably done under cool climate conditions,
during the vegetative growing period a 14°C night temperature and a 16°C
day temperature are best, though production has proven to be satisfactory under
much higher temperatures. In the Dutch auctions, Solidago canadensis L.cv.
"Tara" is graded by stem weight stem, length and ripeness (Anonymous,
2009). The high export value of cut flowers in Egypt encourages growers
to dramatic increases in quality of production. Good quality of Solidago
canadensis cut flower, especially for export is usually achieved by manipulating
growth factors such as temperature and light. These physical factors are very
difficult to control and perhaps expensive in Egypt. Agricultural factors such
as spacing have critical effects on quantitative and qualitative characteristics
of plants (Badi et al., 2004). Plant growth and
flowering depend on PGRs equilibrium and plants quickly respond to change of
hormonal balance (Khangoli, 2001). In some species,
the application of gibberellic acids (specifically GA3) reduces postproduction
losses by preventing leaf senescence (Han, 1997; Ranwala
et al., 2003; Ranwala and Miller, 1998).
Gibberellins, especially gibberellic acid (GA3) play an important role in the
growth and development of plants. Gibberellins are classified as diverse group
of plant hormones that enhance some physiological or biochemical pathways in
plants. The use of GA3 for boosting the growth and vigor of various horticultural
plants is very old known and well documented (Gul et
al., 2006). Gibberelic acid 3 improves yield and quality of ornamental
plants via plant growth incitation and stem elongation (Fathipour
and Esmaellpour, 2000). Gibberelic acid 3 enhances plant growth and internode
length by increasing the cell division and enlargement. It also increases cell
size, stem height, stem thickness and number of leaves. Other studies on the
effect of GA3 on ornamental plants showed that, GA3 accelerated flowering and
enhanced plant height (Gul et al., 2006). Plant
responses to Plant Growth Regulators (PGRs) are highly variable: therefore,
all PGRs must be examined in different species, cultivars and even at various
developmental stages before useful recommendations can be developed (Gent
and McAvoy, 2000).
The experiment was undertaken to estimate the proper planting density and concentrations
of GA3 for quantitative and qualitative characteristics of Solidago
MATERIALS AND METHODS
The experiment was carried out in two successive seasons, started in February
2012 and ended in July of the same year and repeated during the same period
of time in 2013, in Meniat bani Mansour village, Etey Ellbaroud, El-Behira Governorate,
Egypt (30" 54' 34, 87" N and 30" 42' 33, 78" E) in an open private commercial
field provided with drip irrigation fertigation system.
Plant material: Rooted cutting of Solidago canadensis L. cv.
"Tara" (Fig. 1) of length 5 cm with eight to nine leaves per
cutting (Fig. 2) were planted in beds of length 6 m and width
1 m in sand clay loam soil composed of Sand: Clay: Silt at 65: 25: 10 v/v, respectively,
two planting densities were used 16 and 32 plants m-2 (Fig.
3). Soil analysis was carried out in the soil testing laboratory, Desert
Development Center, American University in Cairo (Table 1).
Five concentrations of (GA3) Gibberellic Acid were used as a foliar
spray application at a concentration of 0, 50, 100, 200 and 400 ppm. Gibberellic
Acid was applied four times in the morning till running off point: the first
spray was applied 45 days after planting, then three applications one week apart.
||Inflorescence of Solidago canadensis L. cv. "Tara"
||Rooted cutting of Solidago canadensis L. cv. "Tara"
of length 5 cm with eight to nine leaves per cutting
||Net (12.5x12.5 cm) for adapted planting density
||General view of Solidago canadensis L. cv. "Tara" plants
at open field
Irrigation and lighting systems: Plants were irrigated using drip irrigation
system and grown under natural temperature (Fig. 4) and controlled
day lengths of (16-18 lighting hours per day) using Tungsten lamps for extending
day length from 9 Pm to 3 Am (at a rate of 15 watts m-2) with cyclic
lighting of 15 min on and 15 min off. The lamps were fixed at 2.5 m from soil
surface. Solidago stays rosette when minimum temperature and day length
are less than 15°C and 12 h, the influence of day length over the rosette
formation is stronger than the influence of cold temperatures. With the usage
of lighting and heating, a program of year round production is possible (Highsun
Express Plugs, 2008), also he mentioned that, the application of lighting
and heating (temperature over 10°C and light 16 h) after pruning back the
plants, Solidago keeps producing flower stalks. When the stalks reach
to 30-40 cm or your target stem length, stop lighting and then Solidago
grows generative and forms its flowers.
Fertilizing system: Two weeks after planting, ammonium nitrate at a
rate of 0.5 g L-1 was added to the irrigation water to all treatments
for one month then substituted by calcium nitrate at 0.5 g L-1, when
the plants height reached 25 cm a compound fertilizer of N: P2O5:K2O
(13:3:42) was used at the rate of 0.5 g L-1.
Statistical analysis of data: The experimental design was a Randomized
Complete Block Design (RCBD) in factorial experiment with three replicates:
each replicate contained three samples, the main effect was the planning density
and sub effect was the (GA3) Gibberellic Acid concentrations. Data
were subjected to Analysis of Variance (ANOVA) using the SAS program (SAS,
2002) and the mean values were compared using Tukey's test at p=0.05 level
(Snedecor and Cochran, 1974).
Stem height, stem circumference, fresh weight, dry weight, number of leaves
plant-1, total leaves area plant-1, inflorescence length,
percentage of inflorescence length stem-1, number of flowering stem
plant-1, number of flowering branches inflorescencestem plant-1,
flowering branches length inflorescence-1, days to flowering, vase
life, number of offsets, chlorophyll a, chlorophyll b, total chlorophyll and
caroten were recorded. In this study the values are means of two seasons, 2012
and 2013 were presented in results part.
Chlorophyll a, chlorophyll b, total chlorophyll and carotene contents of leaves
were assayed in the commercial cut stage1/3 open inflorescence according (Wintermans
and de Mots, 1965), absorption at 662, 644 and 440 nm were detected using
spectrophotometer (UNICO 3200). Vase life, the stem were cut to a uniform length
and lower leaves were removed leaving only few upper leaves after that, the
stems were put in 250 mL conical flask containing distilled water at (room temperature
30°C±2 and 75% humidity) until wilting.
RESULTS AND DISCUSSION
Vegetative growth: The analysis of variance showed that, the F-values
of planting density, GA3 concentration and interactions between them
were significant at level 0.05 of significance. In general, all data on means
of Solidago canadensis L. cv. "Tara" stem height, stem circumference,
fresh weight, dry weight and total leaves area per plant were reduced significantly
by increasing planting density from 16-32 plants m-2 (Table
2). The reduction in parameters might be due to the excessive competition
between plants on nutrients and water and reduction in light intensity and light
penetration to lower leaves (Rahnama and Bakhshandeh 2006;
Bugbee and Salisbury 1988; Osman
et al., 2011).
Stem height increased significantly by increasing GA3 concentration
reaching its peak at 200 ppm GA3 (94.33 cm) and then declined at
higher concentration and the highest stem length was achieved at 200 ppm GA3
combined with 16 plants m-2 (101.22 cm). Table 2
same results were reported by Kazaz and Karaguzel (2010),
Patil et al. (1996) and Pobudkiewicz
and Novak (1992) in goldenrod, they reported that the GA3 treatments
increased plant height in goldenrod plants.
||Effect of planting density (D), GA3 concentration
(ppm) and their interactions (DxGA3) on vegetative growth of
Solidago canadensis Tara
|Values are means of two seasons, 2012 and 2013, L.S.D0.05
= Least significant differences at 0.05 probability, Means with the same
letter are not significantly different (p = 0.05) according to Tukey
This result might be due to that the Gibberellins (GA3) play important
roles in several processes including shoot elongation, cell division, cell elongation
and increase in the internodal length (Roberts et al.,
1999; Kende and Zeevaart, 1997).
Stem circumference increased by increasing GA3 concentration compared
to control then decreased at higher concentration: which is agreement with Karaguzel
and Mansuroglu (2003) in Consolida orientalis however, this difference
was found not significant except the result at 400 ppm GA3 was decreased
significant. The best Stem circumference (2.03 and 2 cm) was found by combination
GA3 concentration at 50 ppm with 16-32 plants m-2, respectively
Number of leaves per plant and total leaf area decreased significantly by increasing
GA3 concentration. The reduction in total leaf area might be due
to the reduction in total number of leaves per plant which due to increase in
the internodal length (Roberts et al., 1999)
in Roses confirmed the effect of GA3 on increasing of internode length.
The best number of leaves per plant after control Table 2
(49.22 and 49.88), were found by combination GA3 concentration at
(50 ppm) with (16 plants m-2 and 32 plants m-2), respectively
after (44.22 and 43.22) were found by combination GA3 concentration
at (100 ppm) with (16-32 plants m-2), respectively. The best total
leaf area after control (283.44 and 186.89 cm2) were found by combination
GA3 concentration at (50 and 100 ppm) with 16 plants m-2,
The highest fresh weight after control (53.55 and 50.44 g) Table
2 were found by combination GA3 concentration at (100 and 50
ppm) with (16 plants m-2), respectively. These results might be due
to effect of GA3 and planting density on vegetative and flowering
growth that agreement with Kumar and Singh (2003) they
showed spraying of 100 ppm GA3 increased fresh flower weight in Carnation,
GA3 may be also promote cell growth by causing decrease in the osmotic
potential of cells (Attia, 2004) on Zantedeshia aethopica
that reflected on enhancing leaf bud development as well as blade area and its
fresh and dry weight.
The highest dry weight after control (42 and 41.88 g) Table 2
were found by combination GA3 concentration at (100 ppm) with (32
and 16 plants m-2), respectively. Similar results were obtained by
Wakchaure et al. (2008) in goldenrod.
Flowering characteristics: The analysis of variance showed that, the
F-values of planting density, GA3 concentration and interactions
between them were significant at level 0.05 of significance. Generally, All
data on means of Solidago canadensis L. inflorescences length, percentage
inflorescences length stem-1, number of flowering branches inflorescencestem
plant-1 and flowering branches length inflorescence-1
reduced significantly by increasing planting density from 16-32 plants m-2
(Table 3). The reduction in parameters might be due to the
competition between plants on nutrients and water which led to reduction in
vegetative growth then reflected at flowering growth (Bugbee
and Salisbury 1988; Osman et al., 2008)
in carthamus tinctorius while, a significant delay in flowering occurred
due to increasing planting density from 120.15-125 days (Table
3). This result might be due to plant response to light intensity due to
tight spacing which cause delay in emergence of flowers that agreement with
Sloan et al. (2003) in sunflower and (Osman
et al., 2011) in solidago.
Inflorescences length and percentage inflorescences length stem-1
increased significantly by increasing GA3 concentration compared
to control reaching its peak at (100 and 200 ppm) GA3 (56.83 and
59.55 cm) and (57.22 and 54.83%), respectively then declined at higher concentration.
The highest inflorescence length (66.88 cm) was achieved at 200 ppm GA3
combined with 16 plants m-2 and the best percentage inflorescences
length stem-1 (58.44 and 57.11%) were obtained at (100 ppm GA3
combined with 32 plants m-2 and 200 ppm GA3 combined with
16 plants m-2), respectively (Table 3). These results
might be due to GA3 enhances plant growth by increasing the cell
division, cell elongation and cell size which agreement with Gul
et al. (2006).
Number of flowering stem plant-1 increased by increasing GA3
concentration compared to control however, this difference increased was not
significant. The highest number of flowering stem plant-1 (3.44,
3.33 and 3) were found by combination GA3 concentration at (400,
100 and 200 ppm) with 16 plants m-2, respectively (Table
3). This result agreement with Wakchaure et al.
(2008) he reported that GA3 treatment improved the yield and
flower quality parameters in goldenrod. Number of flowering branches inflorescencestem
plant-1 decreased significantly by increasing GA3 concentration.
The highest numbers of flowering branches inflorescencestem plant-1
after control (31.22 and 28.77). Table 3 were found by combination
GA3 concentration at (50 and 100 ppm) with 16 plants m-2,
respectively. These results might be due to the effect of GA3 on
increase in the nternodal length (Roberts et al.,
1999) in Roses.
Flowering branches length inflorescence-1 increased significantly
by increasing GA3 concentration compared to control then decreased
at higher concentration. The highest flowering branches length inflorescence-1
(29.55 and 24.66 cm) were found by combination GA3 concentration
at (200 and 100 ppm) with 16 plants m-2, respectively (Table
3) (Roberts et al., 1999).
||Effect of planting density (D), GA3 concentration
(ppm) and their interactions (DxGA3) on flowering characteristics
of Solidago canadensis "Tara"
|L.S.D0.05: Least significant differences at 0.05
probability, Means with the same letter are not significantly different
(p≤0.05) according to Tukey Values are means of two seasons, 2012 and
Increased GA3 concentration led to delay in flowering however the
difference was not significant. This result might be due to the role of GA3
as a component of flowering stimulus since it can be a substitute of long day
or cold requirements needed for flowering (Taiz and Zeiger,
2002) and (Brooking and Cohen, 2002). The earliest
flowering (118.89 days) table 3 was found by combination GA3 concentration
at 400 ppm with 16 plants m-2. Similar results were reported by Patil
et al. (1996) in goldenrod.
Vase life, offset production and chemical analyses: All data on means
of Solidago vase life, number of offsets plant-1, chlorophyll
a, chlorophyll b, total chlorophyll and carotene contents of leaves in reduced
significantly by increasing planting density from 16-32 plants m-2
and were positively significant affected by GA3 its peak at 100 ppm
GA3 (11 days, 2.77 offsets plant-1, 8.17, 11.94, 20.11and
2.89 mg L-1), respectively then declined at higher concentration
and the highest values of chlorophyll b, total chlorophyll and carotene contents
of leaves (12.8, 20.98 and 3.72 mg L-1), respectively were achieved
by combination GA3 concentration at 100 ppm with 16 plants m-2
(Table 4). These results could be explained through the role
of planting density and GA3 in stimulating the vegetative growth, as mentioned
previously and hence high accumulation rate of metabolic components especially
carbohydrates such as chlorophyll and carotene.
||Effect of planting density (D), GA3 concentration
(ppm) and their interactions (DxGA3) on vase life, offset production
and chemical analyses of Solidago canadensis "Tara"
|Values are means of two seasons, 2012 and 2013 , LSD0.05:
Least significant differences at 0.05 probability, Means with the same letter
are not significantly different (p≤0.05) according to Tukey
That result was confirmed with the result obtained by Taiz
and Zeiger (2002) and EL-Ashry et al. (1998)
on Strelitizia reginae.
The GA3 application pre-harvest significantly increased vase life
of Solidago inflorescence in comparison with the control and the peak
at 100 ppm GA3 (11 days) then declined at higher concentration and
the longest vase life was observed (12 days) by combination GA3 at
100 ppm with 16 plants m-2 (Table 4). Improving
the postharvest quality of Solidago inflorescence by using GA3
could be explained through the role of GA3 Improving water balance,
fresh weight (EL-Saka et al., 2002) and hence
high accumulation of carbohydrates in stem and leaves which consequently increased
the vase life (Hassan et al., 2003).
Number of offsets per Solidago plant was positively affected by GA3
application in comparison with the control. GA3 at (50 and 100 ppm)
were more effective (3.11 and 2.77), respectively and the highest number of
offsets per plant (3.44 and 3) were found by combination GA3 at (50
and 100 ppm) with 16 plants m-2 (Table 4). These
results could be explained through the role of GA3 and planting density
in stimulating the vegetative and flowering growth in Solidago plant,
as mentioned previously, consequently the plants could produce good plants which
can store large amount of food in produce more number of offsets per plant,
in addition the long day condition (Highsun Express Plugs,
2008) which more available in July under open felid in Egypt condition,
that led to more vegetative growth translated into more offsets.
With respect to almost all characteristics for Solidago canadensis "Tara"
cut flower, we can recommend that the best results were recorded in plants treated
by combination of GA3 at 100 ppm with 16 plants m-2 since
it gave stem height (90.66 cm), stem circumference (1.95 cm), fresh and dry
weight (53.55 and 41.88 g), respectively, inflorescence length (54 cm), percentage
inflorescence length stem-1 (56%), number of flowering stem plant-1
(3.33), number of flowering branches inflorescencestem plant-1 (28.77),
flowering branches length inflorescence-1 (24.66 cm), days to flowering
(121 days), total chlorophyll and carotene contents of leaves (20.98 and 3.72
mg L-1), respectively vase life (12 days) and number of offsets plant-1
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