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International Journal of Horticultural Science and Technology
Vol. 7, No. 1; March 2020, pp 59-68
Print ISSN: 2322-1461 Online ISSN: 2588-3143
DOI: 10.22059/ijhst.2020.274293.275
Web Page: https:// ijhst.ut.ac.ir, Email: ijhst@ut.ac.ir
Response of Germination and Seedling Growth of Pepper
cultivars to Seed Priming by Plant Growth Regulators
Saeedeh Saeidi Tombegavani1, Bahman Zahedi2*, Sadegh Mousavi Fard2 and Ahmad
Ahmadpour3
1. MSc Student, Department of Horticulture, Lorestan University
2. Assistant Professor of Lorestan University
3. Educational Instructor of Kerman Agricultural and Natural Resources Research Center
(Received: 3 February 2019, Accepted: 3 October 2019)
Abstract
In order to study the germination and growth of pepper seeds, a factorial experiment based on
a completely randomized design with three replications was conducted. The first factor was
consisting of five cultivars of pepper (Marquiza, Cadia, California Wonder, California
Wonder 310 and California Wonder 300) and the second factor was gibberellic acid with
three levels (0 as control, 250 and 500 ppm), and the third factor was naphthalene acetic acid
with three levels (0 as control, 50 and 100 ppm). The results showed that the highest
germination percentage (89.9%- California-Wonder 310 cultivar), rate of germination (0.85-
California-Wonder 310 cultivar), shoot height (95.99 mm- California Wonder 300 cultivar),
shoot fresh weight (6.62 g- California Wonder 300 cultivar) root fresh weight (3.46g-
California Wonder 300 cultivar), root length (15.85 cm- Marquiza cultivar), leaf length (5.36
cm-Cadia cultivar) and stem diameter (26.91mm- California Wonder 300 cultivar) were
obtained from the concentration of 500 ppm GA3 and 100 ppm NAA. The maximum seed
vigor index (749.6) was detected in 0 ppm GA3 and 100 NAA in California Wonder 300
cultivar. The 500 ppm concentration of GA3 and 0 NAA in California Wonder 310 cultivar
caused the highest leaf number (3.96). No significant differences were obtained for leaf area
and leaf width among all tested concentrations. It can be concluded that seed priming of
pepper with plant hormones (GA3 and NAA) is a proper strategy for improving germination
and growth traits of pepper plants.
Keywords: Capsicum annum L., gibberellin, plant hormone, naphthalene acetic acid.
Introduction
Capsicum species from the Solanaceae
family are native to the tropical and humid
zones of Central and South America. These
species are now widely spread throughout
the tropical and sub-tropical part of the
world as the most important source of
vegetable (Zimmer et al., 2012). Among 31
wild species, 5 species (C. annuum L., C.
*Corresponding Author, Email: Zahedi.b@lu.ac.ir
chinense Jacq. C. frutescens L, C.
baccatum L. and C. pubescens) have been
domesticated (Bosland and Votava, 2012).
Germination and seedling emergence
are the critical stages in Capsicum plant
life cycle. Capsicum as a tropical crop
germinates properly at 25-27°C (Hartmann
et al., 1988) but slowly in cold
temperatures, increasing the susceptibility
of seeds and young seedlings to disease.
Rapid and uniform seedling emergence is
60 Int. J. Hort. Sci. Technol; Vol. 7, No. 1; March 2020
essential to attain early maturity, uniform
plant stands and high yield by reducing the
risk of disease attack (Cheng and Bradford,
1999). One of the major concerns related to
Capsicum cultivation is its germination
pattern. It is very important to improve the
germination of this species to establish
uniform growth and successful yield from
seed growing plants (Bewley, 1997).
Germination process is influenced by
temperature and seed moisture content.
Seed priming is a commercially successful
practice and an efficient method for
regulating the germination process. Using
this practice, we will be able to enhance
rapid and uniform emergence to achieve
high plant vigor and growth (Singh et al,
2015).
Seed priming decrease necessary time
for germination and seedling emergence
and to synchronize emergence (Parera and
Cantliffe, 1994). Different priming
treatments have been created to increase
the conformity and speed of seed
germination (Finch-Savage et al, 2004).
Several types of seed priming including
hydropriming (drum priming) and osmo-
priming (Osmo-conditioning) are generally
applied to improve germination of seeds.
Hydropriming is a non-osmotic method of
seed priming that attained by continuous or
successive addition of a limited amount of
water to the seeds. Osmo-priming (Osmo-
conditioning) is the standard priming
technique to increase uniform emergence,
and growth of plants. In this technique
seeds are incubated in well-aerated
solutions such as PEG and KCl and
priming with plant growth hormones (Tian
et al, 2014). Different hormones (e.g. IAA,
GA, and NAA) are also used for seeds
priming. Plant hormones such as
gibberellins are efficient in breaking
dormancy and causing rapid germination of
seeds by antagonizing ABA activity. The
aim is activation of ABA catabolizing
enzymes and inhibition of the ABA related
biosynthesis pathways to decrease ABA
levels (Atia et al., 2009).
Naphthaleneacetic acid (NAA) is a
synthetic auxin plant hormone that
significantly enhances seed germination
(Kanmegne et al, 2007).
There are many examples for seed
priming by plant hormones, for instance
hormonal-priming of maize seeds with 100
mg L-1 GA3 for 24 h resulted in improvement
of germination rate, mean seedling
emergence time, germination index and
decrease in mean germination time (Afzal et
al, 2008). Yogananda et al. (2004) reported
that priming with GA3 (200 ppm) led to a
significant increase in germination,
germination rate and seedling vigor index,
root and shoot length and seedling dry matter
in bell pepper seeds. Seed priming with
acetylsalicylic acid and salicylic acid has
been reported to improve germination and
resulted in greater uniformity of germination
and establishment of seedlings under high
salinity conditions (Khan et al, 2009).
Therefore, the objective of the present
study was to analyze the effect of hormonal
priming with GA3 and NAA on germination
traits and some characteristics of pepper
plants and to determine the best combination
for GA3 and NAA concentrations for
improving germination and growth of
different pepper cultivars.
Material and methods
Source of Seeds
Seeds of five pepper (Capsicum annum L.)
cultivars (Marquiza, Cadia, California
wonder, California wonder 300 and
California wonder 310) were surface
sterilized in 2.5% sodium hypochlorite
solution for 10 min, then rinsed with
autoclaved water and air dried. Then, the
weight of 1000 seeds was measured.
Plant Growth Regulator priming
Plant hormonal treatments were performed
using different concentrations of GA3 and
NAA. Three levels of GA3 (0 as control,
250 and 500 ppm) and three levels of NAA
(0 as control, 50 and 100 ppm) were used
for seeds priming.
Response of Germination and Seedling Growth of Pepper cultivars to … 61
For the preparation of 250 ppm and 500
ppm GA3, 0.25 g and 0.5 g of GA3, was put
in a measuring flask and volume was
increased to 1000 mL. For making of 50
ppm and 100 ppm NAA, 0.05 g and 0.1 g
of NAA was put in a measuring flask and
volume was increased to 1000 ml.
Germination tests
Seeds were placed in Petri-dishes and
primed with different concentrations of GA3
and NAA for 6 h. Then, seeds were spread
on blotting paper for 6 h and dried at room
temperature (25 °C). After treatment with
plant hormones, seeds were prepared for
planting in trays with dimension of 7 × 15
cm. Growth medium was prepared by
mixing 1:1 peat moss and sand.
Traits measurement
After emergence, the number of germinated
seeds was recorded on daily basis. Then,
germination percentage, mean germination
rate, seedling height (cm), root length (mm),
stem diameter (mm), leaf length (cm), leaf
width (cm) leaf number and seedling root
fresh and dry weight (after 40 days) were
calculated. Following equations were used
for calculating germination traits:
Germination % = (total number of
seeds/number of germinated seeds per day)
×100
Mean of germination rate (MGR)= ∑((number
of germinated seeds per day)n/n-1)
Seed vigor index = Germination% × Mean of
seedling height/100
In this equation, n is the number of
days.
The length of seedling and root was
measured with a caliper. Fresh and dry
weights of root and seedling were
measured using digital scales after drying
in oven at 70 °C for 48 h.
Statistical analysis
The statistical analysis was based on a
randomized completely design (CRD);
with three replications. Analysis of
variance was carried out with SAS
software. The mean comparison was
performed with Duncan's test at (p≤0.01).
Results
Germination indices
Seed germination of different cultivars was
significantly affected by priming
treatments. The results showed that the
effect of cultivar, GA3, NAA and their
interactions were significant (p≤0.01) for
germination percentage, germination rate,
and seed vigor index (Table 1). Pretreated
seeds with different concentrations of plant
hormones showed significantly higher
germination percentage as compared to
control. The highest germination
percentage (85.98%) was recorded in 500
ppm GA3 and 100 ppm NAA in California
Wonder 310 cultivar as compared to
control (31.9%). In all cultivars, the highest
germination percentage was obtained from
500 ppm GA3 and 100 ppm NAA, and the
lowest germination percentage was
recorded in control (Table 2). The
germination rate was significantly
increased by seed priming. California
Wonder 310 cultivar pretreated with 500
ppm GA3 and 100 ppm NAA exhibited
maximum germination rate (0.85) and
minimum germination rate (0.31) was
observed in unprimed California Wonder
seeds (Table 2). Seed vigor index was
significantly improved in Capsicum annum
seeds primed with GA3 and NAA as
compared to the unprimed. In general, the
maximum seed vigor index (749.6) was
attained from treatment of 0 ppm GA3 and
100 NAA in California Wonder 300 and
California Wonder cultivars as compared
to respective controls (159.1) (Table 2).
Growth characteristics
According to the obtained results, all
studied traits were affected by the seed
treatments with plant hormones and they
showed significant difference with the
control (non-primed seeds). Seedling
height (cm), root length (cm), leaf number,
62 Int. J. Hort. Sci. Technol; Vol. 7, No. 1; March 2020
stem diameter (mm), leaf length (cm), leaf
width (cm), seedling dry and fresh weights
(g) and root dry and fresh weights (g) were
significantly affected by different
concentrations of GA3 and NAA (Table 3).
It was observed that seed priming
treatments increased seed germination and
shoot height of all cultivars in the present
study. The highest shoot height achieved at
500 ppm GA3 and 100 ppm NAA in
California Wonder 300 cultivar, but the
lowest shoot height was obtained in 500
ppm GA3 and 100 ppm NAA in California
Wonder 310 cultivar (Table 4). Leaf
number was higher in the seedlings
germinated from primed seeds with GA3
than in non-primed seeds. The maximum
leaf number (3.96) was obtained from the
interaction of 500 ppm GA3 and 0 ppm
NAA in California-Wonder 310 cultivar.
The minimum leaf number (3.63) was
observed from control in California
Wonder 300 cultivar (Table 4). Leaf
number was higher in the seedlings
germinated from primed seeds with GA3
than in non-primed seeds. The maximum
leaf number (3.96) was obtained from the
interaction of 500 ppm GA3 and 0 ppm
NAA in California-Wonder 310 cultivar.
The minimum leaf number (3.63) was
observed from control in California
Wonder 300 cultivar (Table 4). In the
present study, seed priming caused
increase in shoot and root fresh weights.
The highest shoot fresh weight (6.62 g) and
root fresh weight (3.46g) were obtained
from the 500 ppm GA3 and 100 ppm NAA
in the California-Wonder 300 cultivar,
respectively (Table 4). The lowest shoot
(3.23 g) and root (1.61 g) fresh weights
were obtained from control of Cadia and
California Wonder cultivars, respectively.
Table 1. Analysis of effects of different concentration of the GA3 and NAA on germination characteristics
of five cultivars of pepper
s.o.v
df
Mean squares
Germination (%)
Germination Rate
Seed Vigor Index
Cultivar
4
80.79**
0.008**
55752.21**
Gibberellin (GA3)
2
13577.89**
1.35**
1500041.73**
Naphthaleneacetic acid (NAA)
2
1465.77**
0.146**
273252.46**
Cultivar× GA3
8
60.15**
0.006**
6313.74**
Cultivar× NAA
8
5.33**
0.0005**
2971.92**
GA3× NAA
4
180.04**
0.018**
40629.40**
Cultivar× GA3× NAA
16
11.59**
0.001**
1706.79**
Experimental error
90
1.43**
0.0001**
239.15
C.V
-
2.29**
2.29**
4.03
*, ** = Significant at 5 % and 1%, respectively, NS= Non-significant
The effect of pepper cultivars and the
interaction between pepper cultivars and
plant hormones were not significant for dry
weight traits of five pepper cultivars, but the
single effect of GA3 and NAA on this trait
was significant (p≤0.01) (Table 3). The
concentration of 500 ppm GA3 showed the
highest shoot (0.58 g) and root (0.28 g) dry
weights and the lowest shoot (0.44 g) and
root (0.22 g) dry weights were observed in
control. In NAA treatments, the highest
shoot (0.53g) and root (0.23) dry weights
were observed in 100 ppm NAA and the
lowest shoot (0.42g) and root (0.16g) dry
weights were observed in the control (Table
5). Seed priming significantly affected the
stem diameter. The highest stem diameter
(26.91 mm) was found in the concentration
of 500 ppm GA3 and 100 ppm NAA in
Cadia cultivar and the lowest stem diameter
(12.92 mm) obtained from control in the
California Wonder 300 cultivar (Table 4).
Leaf length but not leaf width was
significantly affected by seed priming. Leaf
Response of Germination and Seedling Growth of Pepper cultivars to … 63
length of plants from primed seeds was
significantly improved compared to the
control. The concentration of 500 ppm GA3
and 100 ppm NAA exhibited the highest leaf
length (5.36cm) in the Cadia cultivar but
control treatment showed lowest stem
diameter (75.7 cm) in California Wonder 300
cultivar (Table 4).
Table 2. Interaction effect of different concentration of the GA3 and NAA on germination characteristics
of five cultivars of pepper
In a column, means with the same letters are not significantly different
Table 3. Analysis of effects of different concentration of the GA3 and NAA on growth characteristics of
five cultivars of pepper
s.o.v
df
Mean squares
Plant
height
(cm)
Root
length
(cm)
Leaf
number
Leaf area
(cm2)
Shoot
fresh
weight
(gr)
Shoot
dry
weight
(gr)
Root
fresh
weight
(gr)
Root
dry
weight
(gr)
Stem
diameter(mm)
Leaf
length
(cm)
Leaf
width
(cm)
Cultivar
4
815.56**
1.97**
0.024ns
10044.72ns
4.52**
0.054ns
1.13**
0.01ns
2.87**
2.78**
0.33ns
(GA3)
2
1738.14**
116.31**
0.29**
8989.94ns
23.67**
0.170**
5.91**
0.04**
15.58**
15.85**
0.05ns
(NAA)
2
1513.16**
25.70**
0.69**
9347.86ns
8.13**
0.128**
2.03**
0.03**
5.62**
5.36**
0.05ns
Cultivar× GA3
8
1885.01**
1.31**
0.068**
10028.97ns
0.181**
0.028ns
0.04**
0.007ns
0.12**
0.21**
0.67ns
Cultivar× NAA
8
83.36**
0.49**
0.037*
9983.25ns
0.477**
0.008ns
0.051**
0.002ns
0.27**
0.72**
0.67ns
GA3× NAA
4
53.09**
1.067**
0.099**
10027.01ns
0.206**
0.003ns
0.119**
0.002ns
0.18**
0.81**
0.11ns
Cultivar×
GA3× NAA
16
66.35**
0.95**
0.036**
9954.85ns
0.100**
0.005ns
0.025**
0.001ns
0.053**
0.035**
1.35ns
Experimental
error
90
6.27
0.064
0.014
9970.266
0.020
0.025
0.005
0.006
0.019
0.01
1.86
C.V
-
3.98
2.35
3
19.35
3.04
21.33
3.04
21.33
2.51
2.51
6.82
*, ** = Significant at 5 % and 1%, respectively, NS= Non-significant
Factor
Mean comparison
Germination (%)
Germination Rate
Seed Vigor Index
NAA
NAA
NAA
0 ppm
50 ppm
100 ppm
0 ppm
50
ppm
100
ppm
0 ppm
50 ppm
100 ppm
Marquiza
GA3(0 ppm)
33.98uv
40.3opq
38.58qrs
0.33uv
0.40pq
0.38qrs
17401uv
224.9r-t
209.31rst
GA3(250 ppm)
42.38no
48.55k
50.96jk
0.42op
0.48 l
0.50jk
274.25o
318.53n
364.87lm
GA3(500 ppm)
53.38hi
65.09e
76.92c
0.53hi
0.65e
0.76c
426.2 lm
477.16i
697.68c
Cadia
GA3(0 ppm)
32.83uv
37.84rs
39.75pqr
0.32uv
0.37rs
0.39qrs
159.1v
206.52st
238.7pqr
GA3(250 ppm)
43.59mn
49.44jk
50.66jk
0.43no
0.49kl
0.50jkl
266.71op
326.03n
357.78m
GA3(500 ppm)
61.50f
66.37e
79.90b
0.61f
0.66e
0.79b
426.27j
326.03hi
643.46de
California
wonder
GA3(0 ppm)
31.97v
33.74uv
39.80pqr
0.31v
0.33uv
0.39rq
160.57v
311.2rst
270.17o
GA3(250 ppm)
43.19mn
48.63k
52.14ij
0.43no
0.48kl
0.52ij
275.32o
489.07kl
418.42jk
GA3(500 ppm)
66.23e
71.96d
81.24b
0.66e
0.71d
0.81b
424.70j
596.37f
737.21b
California
wonder 310
GA3(0 ppm)
32.97uv
34.62u
39.07qrs
0.32uv
0.34u
0.39qrs
204.98st
225.4rst
259.3opq
GA3(250 ppm)
45.34lm
49.05k
54.83gh
0.45mn
0.49kl
0.54gh
312.80n
354.84m
435.58j
GA3(500 ppm)
64.21e
76.37c
85.98a
0.64e
0.76c
0.85a
508.9gh
623.92e
749.64b
California
wonder 300
GA3(0 ppm)
35.07tu
37.07st
42.07nop
0.35tu
0.37st
0.42op
200.90tu
235.5qrs
306.79n
GA3(250 ppm)
46.13 l
50.92jk
55.75g
0.46m
0.50ik
0.55g
324.62n
402.97jk
501.43hi
GA3(500 ppm)
65e
73.50d
81.15b
0.65e
0.73d
0.81b
531.39g
664.13d
819.22a
64 Int. J. Hort. Sci. Technol; Vol. 7, No. 1; March 2020
Table 4. Interaction effect of different concentration of the GA3 and NAA on growth characteristics of five
cultivars of pepper
Factor
Mean comparison
Plant height
(cm)
Root length
(cm)
Leaf number
Stem diameter
(mm)
Shoot fresh
weight (gr)
Leaf length
(cm)
Root fresh
weight (gr)
NAA
NAA
NAA
NAA
NAA
NAA
NAA
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
0 ppm
50 ppm
100 ppm
Marquiza
GA3
(0 ppm)
45mno
48.33qrs
59.76rst
8.67stu
9.35opq
9.04o-r
3.66ij
4b-h
3.96c-h
13.57pq
14.84o
14.32op
3.23op
3.71n
3.58no
8.14pq
8.9o
8.59op
1.69pq
1.85o
1.79op
GA3
(250 ppm)
44.23st
56.3nop
57.76no
10.44j-m
10.86hij
11.76de
4.20abc
3.96c-h
3.93c-h
17.25jkl
17.49i-l
19.09 def
4.31ijk
4.37hij
4.77def
10.35jkl
10.49h-j
11.45def
2.15jkl
2.18h-k
2.38def
GA3
(500 ppm)
58.43no
65.64i-l
74.10ef
11.22e-h
12.56c
15.85a
3.96c-h
4.20abc
4.06a-f
18.49d-h
19.54d
24.18b
4.62d-h
4.88de
6.04b
11.09d-h
11.72d
14.51b
2.31d-h
2.24d
3.02b
Cadia
GA3
(0 ppm)
66.97h-k
70.62f-i
72.30fg
8.24u
8.84q-t
9.68no
3.77a-d
4.15a-d
4.11hij
12.92q
14.62o
16.02mn
3.23p
3.65n
4lm
7.75q
8.77o
9.61mn
1.61q
1.82o
2mn
GA3
(250 ppm)
64klm
67.45g-k
82.76bc
9.98mn
10.67ijk
11.38e-h
3.85c-h
3.85f-j
3.97f-j
16.31lm
17.57i-h
18.79d-g
4.07klm
4.39hij
4.69d-g
9.78lm
10.54h-j
11.27d-g
2.03lm
2.19h-k
2.34d-g
GA3
(500 ppm)
46.35rs
59.7mno
60.80lmn
11.62def
11.75de
12.54c
3.8a-d
4.12a-d
4.15f-j
18.5d-g
19.59d
21.46c
4.62d-h
4.89d
5.36c
11.1d-h
11.75d
12.87c
2.31d-h
2.44d
2.68c
California wonder
GA3
(0 ppm)
47.70rs
45.05rst
49.95qr
8.45tu
9.32o-r
9.68no
3.65d-i
3.85f-j
3.90ij
13.4pq
16.7klm
18.1g-j
4.25op
4.17jkl
4.52f-i
8.04pq
10.02klm
10.86e-i
1.67pq
2.08klm
2.26f-j
GA3
(250 ppm)
68.25g-k
69.20f-k
77.85de
10.56j-l
11.30e-h
11.72def
3.95c-h
4.15a-d
3.95c-h
17k-m
21.4c
21.4c
4.27i-l
5.35c
5.35c
10.2j-m
12.84c
12.84c
2.12j-m
2.76c
2.67c
GA3
(500 ppm)
64.2klm
71.20fgh
66.15h-k
11.03ghi
11.57def
12.60c
3.85ab
4.20abc
4.25f-j
17.1k-m
22.1c
24.2b
4.27i-l
5.52c
6.05b
10.26j-m
13.26c
14.52b
2.13j-m
2.76c
3.02b
California wonder 310
GA3
(0 ppm)
52.70pq
56.6nop
55.96nop
8.81rst
9.40op
9.74no
3.76a-f
4.13a-d
4.10hij
16.57kl
m
17.36i-l
17.7g-k
4.14jkl
4.34h-k
4.42g-j
9.94klm
10.41i-l
10.62h-k
2.07klm
2.17il
2.21g-k
GA3
(250 ppm)
44.83st
46.43rs
38.84u
10.07l-n
10.45j-m
11.31e-h
3.9a
3.9d-i
4.26d-i
18.39e-i
19.28de
21.18c
4.59e-h
4.82de
5.29c
11.03e-i
11.57de
12.7c
2.29e-i
2.41de
2.64c
GA3
(500 ppm)
69.36f-i
80.94dc
87.11b
11.56d-g
11.55d-g
12.66c
3.96a
4.06a-f
4.26c-h
21.13c
21.78c
23.24b
5.28c
5.44c
5.81b
12.67c
13.07c
13.94b
2.64c
2.72c
2.90b
California wonder 300
GA3
(0 ppm)
64.76jkl
67.53g-k
84.40bc
8.42tu
8.42tu
10.05lmn
3.63j
3.9d-i
4.14a-d
15.27no
16.94klm
19.44de
3.81mn
4.23i-l
4.86de
9.16no
10.16klm
11.66de
1.90no
2.11klm
2.43de
GA3
(250 ppm)
41.40tu
55.53op
57.43nop
10.3k-m
10.3k-m
12.07d
3.86f-j
4.03a-g
4.13a-d
18.76d-g
21.35c
23.99b
4.69d-g
5.23c
5.99b
11.26d-g
12.81c
14.39b
2.34d-g
2.66c
2.99b
GA3
(500 ppm)
76.92de
84.09bc
95.59a
11.65d-f
11.65d-f
13.60b
4.13a-d
4.16abc
4.23ab
21.79c
24.09b
26.91a
5.44c
6.02b
6.72a
13.07c
14.45b
16.14a
2.72c
3.01b
3.46a
In a column, means with the same letters are not significantly different
Response of Germination and Seedling Growth of Pepper cultivars to … 65
Table 5. Effect of different concentration of the GA3 and NAA on shoot and root dry weight
Traits
Mean comparison
GA3
NAA
0 ppm
250 ppm
500 ppm
0 ppm
50 ppm
100 ppm
Shoot dry weight (gr)
0.44c
0.5b
0.56a
0.45c
0.52b
0.58a
Root dry weight (gr)
0.22c
0.25b
0.28a
0.21c
0.26b
0.29a
In a row, means with the same letters are not significantly different
Discussion
Germination percentage
According to Rouhi et al. (2012), increase in
the rate of germination and germination
percentage are likely dependent on
gibberellin activity. In fact, gibberellins
stimulate hydrolysis enzymes, especially
alpha-amylase, which results in seed
germination (Yamaguchi, 2008). Different
reports indicated that seed priming increases
the percentage and uniformity of seeds
germination (Kaya et al., 2006; Ghassemi-
Golezani et al., 2008). Yogananda et al.
(2004) reported that treatment of pepper
seeds with 200 ppm gibberellic acid is the
best concentration for percentage of
germination (91.75%) when compared with
its lower concentrations. Similar results were
also obtained in the present study.
Furthermore, a combination of gibberellic
acid + cytokinin and 40 ppm naphthalene
acetic acid had a significant improving effect
on pepper germination (81.5%) in
comparison with the control treatment.
Germination rate
Priming with plant hormone caused a
positive effect on germination rate of
pepper seeds. Eisvand et al. (2015) showed
that in carrot seeds, germination rate
increases in response to priming with
gibberellic acid and salicylic acid (100
ppm). Tabatabaei (2014) reported that seed
priming with gibberellic acid and salicylic
acid increased the seed germination rate of
wheat plants.
Seed vigor index
The seeds vigor index can be improved by
seed priming, which increases the rate and
uniformity of germination (Demir and Van
De Venter, 1999). Our results are similar to
those studies that showed that seed priming
enhances seed vigor index in plants. It has
been shown that gibberellic acid (100 ppm)
can increase the vigor index of chickpea
seeds (Eisvand et al., 2015). Furthermore,
it has been shown that lamb's seed priming
(hydropriming and salicylic acid priming)
increases the rate and percentage of
germination and seed vigor index
(Mohammadi and Shekari, 2015).
Shoot height
It seems that the increase in stem length is
due to an increase in the length of the
internodes. Mohammadi and Shakari
(2015) reported that priming of lentil seed
(hydropriming and salicylic acid) increases
the length of stems and roots. Basra et al.
(2006) reported that rice seed priming with
salicylic acid and gibberellic acid enhances
germination rate and seedling growth.
Root length
Some concentrations of gibberellic acid
increased seedling length, root length, the
fresh and dry weights of maize (Zea mays
L.) root under salinity stress conditions
(Ghodrat et al., 2010). Priming with Indole
butyric acid and naphthaleneacetic acid has
been reported to promote the length of root
and shoot in a concentration of 50 ppm in
Asparagus (Yuan-Yuan et al., 2010). The
significant increase in the shoot and root
length in primed seeds may be due to its
involvement in cell elongation or cell
division and the meristematic growth
(Khan et al., 1992). Moreover, seed
treatments with plant hormones such as
IAA, IBA and NAA enhance root
formation and development (De Castro et
al., 2000).
66 Int. J. Hort. Sci. Technol; Vol. 7, No. 1; March 2020
Leaf number and leaf area
In accordance with finding of present study,
treatment with 200 ppm gibberellic acid in
comparison with control increased plant
height, the number of leaves and number of
primary and secondary branches of eggplant
(Gavaskar and Anburani, 2004). In our
study, the effect of seed priming on leaf area
was not significant, which is not in
agreement with other studies. Chaudhary et
al. (2006) reported that plant growth
regulators had a significant effect on growth
of pepper cultivars (Jwala and Suryamukhi)
and the concentration of 40 ppm NAA
produced the highest leaf area index in
pepper cultivars. Rana and Singh (2012)
studied the effect of plant growth regulators
on growth, yield, and quality of pepper fruit;
they showed that priming with 50 ppm NAA
significantly increases plant height, number
of branches and leaf area.
Fresh and dry weight
Priming has a positive effect on the fresh
and dry weights of shoot and root in pepper
seedlings, which is in agreement with the
previous reports. Hydropriming and
hormonal priming with gibberellic acid and
salicylic acid increased the dry and fresh
weights of carrot root (Eisvand et al.,
2015). Hydropriming (for 24 h) and
osmopriming (with 4% mannitol) in
chickpea seeds caused elongated roots and
stems and increased dry weight as
compared to un-primed seeds (Kaur et al.,
2005). One of the reasons for the increase
of dry weight by gibberellic acid hormones
is probably due to increase in growth and
cell division by influencing the synthesis
and activity of the auxin and cytokinin.
Siddik et al. (2015) showed that NAA
significantly improves morphological
characteristics such as plant height, leaf
number per plant, number of branches per
plant, fresh and dry weights of root and
shoot in sesame. The results of
Vijayakumari (2002) indicated that shoot
and root weights were improved by seed
priming with 200 ppm gibberellic acid.
Stem diameter
The results of present study showed that
stem diameter in all cultivars increased by
higher gibberellic acid concentrations, so
that the maximum stem diameter was
observed in 500 ppm gibberellic acid.
These results are in accordance with the
study of Saravaiya et al. (2010), who
reported that seed treatment with 5 mg/L
gibberellic acid increases plant height,
plant volume, stem length, stem diameter
and dry weight of cabbage.
Leaf length and width
In the present study the highest leaf length
was obtained from the interaction of high
levels of gibberellic acid and NAA. These
results are in consistent with the study of
Vijayakumari (2002) on Andrographis
paniculata plant but the width of the leaf
was not affected by priming with
gibberellic acid and NAA.
Conclusion
In conclusion, different concentrations of
plant hormones caused a significant
improving effect on germination and
growth of pepper seedlings. In the present
investigation, the highest germination
percentage and germination rate were
observed in parsley cultivar due to
hormonal priming treatments as compared
with control in other studied cultivars. The
growth of treated pepper cultivars was
better than unprimed seedlings. Therefore,
the use of gibberellic acid and NAA alone
or in combination can be an effective
approach to improve germination and
growth of pepper plants. The involved
mechanism at physiological and
biochemical levels for this improvement in
pepper seedlings needs to be studied in
future.
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