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Pure Appl. Biol., 7(4): 1301-1308, December, 2018
http://dx.doi.org/10.19045/bspab.2018.700151
Published by Bolan Society for Pure and Applied Biology 1301
Research Article
Salicylic acid an emerging growth and
flower inducing hormone in marigold
(Tagetes sp. L.)
Abdul Basit1, Kamran Shah1,2*, Mati Ur Rahman2, Libo Xing2, Xiya
Zuo2, Mingyu Han2, Noor Alam3, Fayaz Khan4, Imran Ahmed1 and
Muhammad Areeb Khalid1
1. Department of Horticulture, The University of Agriculture, Peshawar-Pakistan
2. College of Horticulture, Northwest Agriculture and Forestry University, Yangling 712100, Shaanxi-China
3. Directorate of Floriculture, DHRD, NARC, Islamabad-Pakistan
4. Department of Agriculture-Horticulture, University of Swabi, KP-Pakistan
*Corresponding author’s email: kamranshah801@nwafu.edu.cn ; kamranshah801@gmail.com
Citation
Abdul Basit, Kamran Shah, Mati Ur Rahman, Libo Xing, Xiya Zuo, Mingyu Han, Noor Alam, Fayaz Khan,
Imran Ahmed, and Muhammad Areeb Khalid. Salicylic acid an emerging growth and flower inducing hormone
in marigold (Tagetes sp. L.). Pure and Applied Biology. Vol. 7, Issue 4, pp1301-1308.
http://dx.doi.org/10.19045/bspab.2018.700151
Received: 06/06/2018 Revised: 17/08/2018 Accepted: 04/09/2018 Online First: 07/09/2018
Abstract
Salicylic acid (SA) is an emerging plant growth regulator that acts as signaling molecule in
plants under biotic and abiotic stresses. SA also exerts a stimulatory effect on different
physiological processes of plant growth but its association with leaf pigments and flowering is
less known. Current experiment was conducted to evaluate the effect of exogenous application
of different doses of SA on marigold (Tagetes sp.) in greenhouse condition. Marigold (Tagetes
sp. L) plants were randomly divided in 4 groups and treated exogenously with four different
concentrations of SA (T0: 0 (only water), T1: 40, T2: 80 and T3: 120 mg/L). The solutions were
sprayed on aerial parts of plant after 60 days of sowing. Results analysis showed that T3 (120
mg/L SA solution) showed maximum number of leaves plant-1 (30.38), highest plant height
(50.63 cm), more number of inflorescence, greater stem diameter (7.84 mm), maximum fresh
weight of flowers (11.90 g), and maximum dry weight of flower (1.25 g). Whereas, minimum
number of leaves (22.74), lowest plant height (40.8 cm), less number of inflorescence, smaller
stem diameter (4.75 mm), minimum fresh flower weight (7.13 g), and minimum dry flower
weight (0.7 g) were observed in T0. Furthermore, various leaf pigments were found higher in
T3. Present study concluded that T3 treatment of SA improved leaf pigments and morphometric
parameters in Marigold. From the aforementioned results, it is suggested that 120 mg/L
concentration of SA should be sprayed exogenously before flowering stage, on marigold plants
for better growth and flower production.
Keywords: Flower production; Growth variables; Leaf pigments; Marigold; SA
concentration; Tagetes spp
Introduction
Marigold is the most commonly grown
ornamental plant, botanical nomenclature is
Tagetes erecta L. and locally known as
Genda, which belongs to family Asteraceae
or Compositeae. It is extensively used for
general purposes, religious functions and
other ceremonies [1]. It is usually grown in
pots or in beds for mass display as well as
in mixed borders for decorative purpose
Basit et al.
1302
[2]. Marigold has lots of varieties, varying
in plant height, flower size, yield and
quality. Its flowers are usually big with
globular shaped [3, 4]. Cultivation of
marigold is easy due to its wide adaptability
to various soils and climatic conditions. It
is an annual economic plant species utilized
in raw or in processed forms in modern
medicinal industry, worldwide. In addition
to the edible uses (i.e. coloring and
flavoring agent of food), marigold also
contain active ingredients and compounds
that have wide applications in nylons and
manufacturing dyes industries [5] and in
pharmacy [6]. Active ingredients of
marigold are produced and stored in its
flowers, most important of which are water-
soluble carotenoid, flavonoids, essential
oil, and mucilaginous compounds [7].
However, flavonoids of inflorescences play
a key role in the pharmacological activity
and in most cases they are categorized for
quercetin and rutin compounds [3, 4]. Its
seeds contain 15-20 % oil, 45-60 % of
which constitute calendic acid [8].
Salicylic acid (SA) is a plant hormone and
act as an antioxidant, produced by root
cells. It play a crucial role in regulating
certain physiological processes in plants
such as growth, germination,
photosynthesis and ion absorption and act
as an important signaling molecule to
various environmental stresses [9]. SA also
contributes in the regulation of biological
processes in plants and is accepted as
endogenous growth regulator due to its
phenolic nature [10]. It play a key role in
thermogenesis (heat generation in
staminate region of flower up-to 14°C
compared to normal) in Arum lily as natural
inductor, which encourages flowering in
many angiosperm’s such as Annonaceae,
Araceae, Aristolochiaceae, Cyclanthaceae,
and Nymphaccae family plants. It controls
ion uptake by roots and create fragrance in
flower to attract insect for pollination [10,
11]. The experimental results of previous
researchers showed influence of SA in
regulation of gene expression signals in the
passage of Arabidopsis leaf senescence.
Besides this, SA might function as a
gravitropism inhibition regulator of fruit
ripening [12]. SA that play a key role in
plant growth regulation and development is
actually a hormone-like substance [10, 11]
which defensive effects in contrast to
abiotic stress factors such as deadly metals
[13], low temperature, heat stress and
oxidative harm [14] has been confirmed.
The role of SA in bringing salt tolerance has
been studied in many plant species. It is also
reported that SA bring tolerance from
salinity in tomato crop [15], carrot [16] and
changes its expression in plants in response
to different environmental stresses [9, 12].
We predict that exogenous application of
SA will improve the leaf pigments and
subsequent growth parameters and hence
flowering will be enhanced. The main
objective of this investigation was to study
the effect of new generation hormone (SA)
on the vegetative growth and flowering of
marigold and to know the effect of SA on
leaf pigments and production of marigold
flower, because the role of SA in defensive
response is widely explored but its role in
leaf pigments and flowering was neglected.
Materials and methods
Experimental site
A research was held under uniform
condition in a greenhouse at Directorate of
Floriculture, DHRD, National Agricultural
Research Center, Islamabad (33.6701° N
latitude, 73.1261° E longitude).
Experimental procedure
Seeds of marigold (Tagetes sp) were
brought from Gurr Mandi Peshawar, grown
in trays under green net in semi shade,
without temperature control. Experiment
was laid out in a completely randomized
design and 48 plants were randomly
divided in 4 groups (T0, T1, T2 and T3), each
group contain 12 plants and 4 replicates
(n=3). After 35 days, the seedlings were
transplanted into 5 L pots filled with dry
leaf mold, soil and sand in a ratio of 1:1:1
(v/v/v). The pots were placed in green
house and irrigated daily to rescue humidity
of the substrate throughout the experiment.
Spraying of SA (Aldrich, St.Louis, MO,
Pure Appl. Biol., 7(4): 1301-1308, December, 2018
http://dx.doi.org/10.19045/bspab.2018.700151
1303
USA) was performed on day 60 of seed
sowing (before the reproductive stage) on
aerial parts of marigold. The spray was
repeated after 1 week (day 67). The 4
different concentrations of SA solutions in
T0, T1, T2 and T3 were 0, 40, 80 and 120
mg/L, respectively [17]. A total of 100 ml
solution was sprayed on each plant, each
time. The inflorescences were initiated and
harvested after 90 days of sowing (DAS)
with the appearance of the 1st flowers held
twice in a week until plant senescence (120
DAS). The data regarding various variables
in each treatment was calculated and
average was taken. Studied traits include,
number of leaves pant-1, which were
calculated by counting total no of leaves per
plant. Plant height (cm) was noted from the
soil surface to the tip of the plant, measured
by measuring tape. Number of
inflorescence was observed by counting
total number of flowers plant-1. Stem
diameter (mm) was calculated at the base of
the stem with vernier caliper [7]. Fresh
weight of flower (g) was noted with digital
balance (Shimadzu, model AY220, Japan),
while dry weight of flower (g) was
determined by drying inflorescences in an
oven at 40°C with air circulation until
constant weight was achieved [5].
Leaf pigments
Leaf pigments were determined according
to the procedure reported in [18, 19] and
using the following equations.
Statistical analysis
The data recorded for various variables was
subjected to analysis of variance (ANOVA)
suitable for completely randomized design
using statistics 8.1 software package
(Statistix®, Analytical Software Inc,
Tallahassee FL, USA). Significant findings
were tested by least significant difference
(LSD) [13]. P < 0.05 was considered
significant [20].
Results and discussion
Number of leaves plant-1
Leaves play a very important role in
photosynthesis which results in an
increased yield. Our findings indicate that a
different concentration of SA influences the
number of leaves per plant. The highest
number of leaves at each harvest were
recorded in treatment T3 (30.38), followed
by T2 (26.7), which was at far with T1
(25.33) while lowest number of leaves
(22.74) was recorded in control (T0) (Figure
1A). SA due to its defensive aspect induced
a protective mechanism in plants
physiology under unfavorable
environment, especially in response to
different pathogens and abiotic stresses. SA
fixed functions of certain enzymes directly
and defensive control genes also induce
precise changes in chloroplast structure and
leaf number which play a vital role in plant
energy status. Subsequently, plant uses two
photo-systems that reduce NADPH and
generate ATP thus used enough energy to
form organic compounds (assimilates),
translocation and storage of which enable
plants to increased number of leaves
beneficially. SA is a phenolic nature
compound and its application on zinnia
produced profound increase in number of
leaves. Moreover, it is involved in
regulation of growth processes of plants,
such as in ornamental plants, and stimulate
leaves in young shoots [21]. Similarly, [5]
revealed that number of leaves in African
violet increases with higher concentration
of SA.
Plant height (cm)
Height of marigold plant was influenced by
various levels of SA foliar application. Our
result showed that maximum plant height
was observed in treatment T3 (50.63 cm),
followed by T1 (47.13 cm) and T2 (44.1
cm). While, minimum plant height (40.8
cm) was noted in plants treated with (T0)
tape water (Figure 1B). SA is a phenolic
compound that enables plants to survive
under challenging soil and environmental
Basit et al.
1304
situations. SA plays key roles in regulation
of various physiological and developmental
processes of plants [21]. Different
concentration of SA increases most of
nutritional and hormonal regulation in
plants [22]. Increased plant height in
marigold with the application of SA could
be the increased rubisco chemical action
and photosynthetic rate. According to [23],
SA cause an increase in plant growth with
increasing cell division in both stem and
root, hence increasing plant height (~23%)
under greenhouse and field condition.
Furthermore, foliar application of SA
treatment on African violets increased
length of petioles and improved height in
onion [7].
Figure 1. Effect of exogenous spray of different levels of SA on (A) Number of leaves and
(B) plant height (cm). Data presented as a-d Means ± SD, bars lacking a common
superscript differ significantly from one another (P ≤ 0.05). T1, T2, T3 are different
treatment groups while T0 is control
Stem diameter (mm)
The data presented in (Figure 2A) revealed
highly significant result for stem diameter
in marigold plant exposed to different level
of SA. Highest stem diameter was recorded
in T3 (7.84 mm) followed by T2 (6.5 mm)
and T1 (5.7 mm). While the thinnest stem
diameter was recorded in treatment T0 (4.75
mm). The increase in stem diameter by
applying SA may be attributed to the
enhanced absorption of ions and minerals
by plant. SA also improves plant
performance by formation of certain
enzymes in plant, thus stimulating
chlorophyll synthesis and photosynthetic
activities, which progresses plant growth
[9]. Hence, application of SA
concentrations causes an increase in stem
diameter (Figure 2A) and plant height
(Figure 1B) [24]. Similarly, [25] reported
that different treatments of acetyl SA on
potato plants encouraged plant growth and
number of leaves per plant.
Number of inflorescence plant-1
SA foliar application showed significant
difference for number of inflorescence per
plant (Figure 2B) in marigold (Tagetes sp).
Maximum number of inflorescence was
recorded in treatment T3 (9.7) followed by
T2 (7.7) and T1 (6.33) while minimum
number of inflorescence was noted in T0
(5.00). These results are in line with [5]
who reported that increased concentration
of SA results in greater number of
inflorescences per plant. SA is considered
as new generation hormone, which induces
thermogenesis in staminate region of
flower up to 14°C, that induces and boost
flowering in plant [10, 11]. These results
are in agreement with those of [27] who
have studied the effect of exogenous SA
application on growth of Calendula
officinalis under salinity stress. Similarly,
[5] described that foliar application of SA
in Saintpaulia, cause an increase in the
number of flowers. SA enhances
transcription and translation of mRNA and
protein [26] that help in developing new
groups of isozymes enhance the number of
flower buds [27].
cbba
0
10
20
30
40
T0 T1 T2 T3
No of leaves
A
dbca
0
20
40
60
T0 T1 T2 T3
Plant Height (mm)
B
Pure Appl. Biol., 7(4): 1301-1308, December, 2018
http://dx.doi.org/10.19045/bspab.2018.700151
1305
Fresh flower weight (g)
Fresh weight of inflorescence of marigold
was influenced by spraying various
concentration of SA solution on marigold
(Tagetes sp). Maximum fresh weight was
recorded in treatment T3 (11.90 g) followed
by T2 (10.1 g) and T1 (8.3 g), while
minimum fresh flower weight (7.13 g) was
recorded in T0 (Figure 2C). According to
[28], SA might have changed the bio-
physical characteristics of plant cell wall.
SA and auxin have a synergistic effect to
promote photosynthesis and favored
translocation of phot-assimilates into
flowers. Present results are in agreement
with the results of [5] in marigold and [29]
in tuberose. Furthermore, SA enhances cell
division in stem and leaves which is a
leading cause of increase in number of
inflorescence [7].
Dry flower weight (g)
Application of exogenous SA also
influenced significant variations in dry
weight of inflorescence. Maximum dry
weight of marigold flower was recorded in
treatment T3 (1.25 g) followed by T2 (1.09
g) and T1 (1.01 g), while minimum dry
weight was recorded in T0 (0.7 g) (Figure
2D). Application of SA significantly
increased the dry weight of flower by
improving photosynthetic efficiency [9],
stabilization of chlorophyll and assimilates
translocation from source to sink [27]
which ultimately enhanced dry weight of
flower [28]. Furthermore, SA acts as
defense hormone that could reduce the
abiotic stress in leaves which ultimately
leads to increase amount of dry matter
contents production in marigold flowers
[30]. Similar results were also reported by
[31] in marigold.
Figure 2. Effect of exogenous spray of different levels of SA on (A) stem diameter (mm)
(B) number of inflorescence (cm) (C) fresh flower weight (g) and (D) dry flower weight
(g). Data presented as a-d Means ± SD, bars lacking a common superscript differ
significantly from one another (P ≤ 0.05). T1, T2, T3 are different treatment groups while
T0 is control
dcba
0
2
4
6
8
10
T0 T1 T2 T3
Stem Diameter (mm)
A
dcba
0
5
10
15
T0 T1 T2 T3
Number of inflorescence
(cm)
B
dc
b
a
0
5
10
15
T0 T1 T2 T3
Fresh flower weight (g)
C
c
bba
0
0.5
1
1.5
T0 T1 T2 T3
dry flower weight (g)
D
Basit et al.
1306
Leaf pigments
Effect of SA exogenous application on leaf
pigments is shown in (Figure 3). It is
evident from the (Figure 3A) that there is a
positive association between SA
application and chlorophyll-a content of
leaf. Higher chlorophyll-a content (20.62
µg.ml-1) was recorded in T3, while lower
(13.87 µg.ml-1) was recorded in T0.
Furthermore, statistical analysis showed a
significant increase with increase in level of
SA application. Effect of exogenous
application of SA on leaf chlorophyll-b
pigment is shown in (Figure 3B). An
increase in level of SA application
significantly increases chlorophyll-b
content. However highest chlorophyll-b
content was recorded in T3 (16.58 µg.ml-1)
as compared to T0 (5.88 µg.ml-1).
Furthermore, leaf total chlorophyll
pigments were also influenced by SA
application. A positive association between
leaf total chlorophyll content and SA were
observed. Moreover, higher trend of total
chlorophyll (37.21 µg.ml-1) was observed
in T3, while lower in T0 (19.76 µg.ml-1)
(Figure 3C). The carotenoid contents were
also increased by SA application on
marigold plants as shown in (Figure 3D). In
comparison with T0 (1.07 µg.ml-1), T3
showed higher concentration of leaf
carotenoid pigments (7.67 µg.ml-1). SA
enhances cell division in leaf surface [32]
and effect photosynthetic pigments and
their derivatives [33, 34] which have a
direct relationship with cell division and
leaf pigment contents [35]. SA molecules
also increased respiration rate and
production of energy for synthesis of more
pigments. SA increases stomatal
transpiration which is responsible for
regulating growth, production, green color
in foliage and flowering [11]. The pathway
of biosynthesis of photosynthetic pigments
and their derivatives are linked together and
have direct co-relationship with hormones
[36].
Figure 3. Effect of exogenous spray of different levels of SA on (A) Leaf chlorophyll-a
(μg/ml) (B) Leaf chlorophyll-b (μg/ml) (C) Leaf total chlorophyll (μg/ml) and (D) Leaf
carotenoid (μg/ml). Data presented as a-d Means ± SEM, bars lacking a common
superscript differ significantly from one another (P ≤ 0.05). T1, T2, T3 are different
treatment groups while T0 is control
Pure Appl. Biol., 7(4): 1301-1308, December, 2018
http://dx.doi.org/10.19045/bspab.2018.700151
1307
Conclusions
In this study, results showed that SA plays an
important role in plant growth, influencing leaf
pigments and enhancing flower quality. The
best result was recorded in treatment T3 (120
mg/L) closely followed by T2 (80 mg/L). This
study provides deep understanding and new
role of new generation hormone (SA) in flower
induction, leaf pigments, and growth of
marigold plant, thus could help the researchers
to investigate the molecular approach in future
research.
Authors’ contributions
Conceived and designed the experiments: A
Basit & K Shah, Performed the experiments: A
Basit, K Shah, MA Khalid & F Khan, Analyzed
the data: A Basit, K Shah, MU Rehman, L Xing
& I Ahmed, Contributed materials/ analysis/
tools: A Basit, K Shah & N Alam, Wrote the
paper: A Basit, K Shah, X Zuo & M Han.
Acknowledgement
We acknowledge Tasneem Akhtar (School of
life Sciences, USTC) for insightful discussions
and constructive comments.
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