423
Research Journal of Agriculture and Biological Sciences, 7(6): 423-433, 2011
ISSN 1816-1561
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Effect of Foliar Application of Salicylic Acid and Chelated Zinc on Growth and
Productivity of sweet pepper (Capsicum annuum L.) Under Autumn Planting
Abou El-Yazeid, A.
Dept. of Hort., Fac. of Agric., Ain Shams Univ., Cairo, Egypt.
ABSTRACT
The field experiment was conducted to study the effect of foliar application with 50 & 100 ppm of salicylic
acid (SA) and 50 & 100 ppm chelated zinc (Zn) and their combination on some growth aspects, photosynthetic
pigments, minerals, endogenous phytohormones, fruiting and fruit quality of sweet pepper cv. California
Wonder during autumn 2009 and 2010 seasons. Results indicated that different applied treatments significantly
increased all studied growth parameters, namely, number of branches and leaves per plant, leaf area per plant
and leaf dry weight. Besides, the two concentrations of each applied salicylic acid or chelated zinc obviously
increased photosynthetic pigments, N,P,K, Zn, total sugars, total free amino acids and crude protein
concentrations in leaves of treated plants as compared with those of untreated ones. Also, all treatments
increased auxin, gibberellin and cytokinin levels in sweet pepper shoots at 95 days after transplanting during
2010 season whereas abscisic acid was decreased. Furthermore, the highest early, marketable and total yields as
well as physical characters of sweet pepper fruits were obtained with 100 ppm salicylic acid plus chelated 50
ppm zinc followed by 50 ppm SA plus 100 ppm Zn. Moreover, different applied treatments induced reduction in
the peroxidase, catalase and superoxide dismutase actives as compared with those of the untreated plants in
sweet pepper leaves at 100 days after transplanting during 2009 and 2010 seasons. In addition, chemical
composition of minerals and some bioconstituents (carbohydrates, vitamin C and total soluble solids) in sweet
pepper fruits were also increased at the same treatments. Hence, it could be recommended that foliar spraying
with salicylic acid at 100 ppm and chelated zinc at 50 ppm can be used to increase the final yield and fruit
quality of sweet pepper plant during the low temperatures of autumn plantations.
Key words: Salicylic acid, chelated zinc, photosynthetic pigments, endogenous phytohormones, peroxidase,
catalase and superoxide dismutase, growth, yield, sweet pepper.
Introduction
Sweet pepper (Capsicum annuum L.) is a member of the solanaceous fruity vegetables. It is one of the most
important, popular and favorite vegetable crops cultivated in Egypt for local consumption and exportation. It
covers a production area of 108,122 fed. in year 2009 that yielded 793,450 tons according to Ministry of
Agriculture and Land Reclamation.
Temperature is one of the major determinants of the occurrence and spread of natural plant associations.
For crops, too, low temperature is one of the most important factors restricting cultivation in a given area. Plants
are said to be cold-sensitive if they die or suffer severe damage at temperatures between 0 and 15°C. Coldtolerant plants, on the other hand, still able to grow near freezing point and are capable of surviving
temperatures as low as 10–15°C below zero. Apart from genetic factors, cold sensitivity also depends on the
stage of development and the level of metabolic activity.
The word salicylic acid (SA) was derived from Latin word “Salix”, meaning willow tree. It is ubiquitously
distributed in the whole plant kingdom and is classified under the group of plant hormones (Raskin, et al.,
1990). Most people learn of the effects of salicylic acid on flowering from the finding that a tablet of aspirin
dissolved in water will make cut flowers last longer. However, some indications of the mechanisms by which
SA may increase flower longevity can be found in the discovery that SA inhibits ethylene biosynthesis in pear
cell suspension culture by blocking the conversion of 1-aminocyclopropane-l-carboxylic acid to ethylene
(Raskin, 1992). Enzyme activities such as amylase and nitrate reductase were increased by SA application
(Sharma, et al., 1986; Chen, et al., 1993). On the other hand, SA showed synergetic effect with auxin and
gibberellins (Datta and Nanda, 1985; Zaghlool, et al., 2006). The exogenous application of SA was reported to
have an effect on a wide range of physiological processes including increased cold germination tolerance in
pepper ( Korkmaz, 2005) and chilling tolerance in cucumber (Kang and Saltveit, 2002). (Abd El-al, 2009) found
that the foliar application of salicylic acid plays a great role in improving the productivity of sweet pepper
Coresponding author: A. Abou El-Yazied, Dept. Hort., Fac. Agric., Ain Shams Univ., P.O. Box 68, Hadayek
Shoubra,11241 Cairo, Egypt.
E-mail: [email protected]
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Res. J. Agric. & Biol. Sci., 7(6): 423-433, 2011
plants. (Horvath, et al., 2007) reported that the application of exogenous SA could provide protection against
several types of stresses such as low temperature. The SA and other phenol derivatives are known to improve
the cold tolerance of plants. It was shown that the addition of 0.5 mM SA to the hydroponic growth solution of
young maize plants under normal growth conditions provided protection against subsequent low-temperature
stress. Besides, the obvious visual symptoms, this observation were confirmed by chlorophyll fluorescence
parameters and electrolyte leakage measurements from the leaves (Janda, et al., 1997, 1999). Thus convincing
data have accumulated about the SA-induced increase in the resistance of cucumber and rice to low temperature
(Kang and Saltveit, 2002), as well as tomato and bean plants to low and high temperature (Senaratna, et al.,
2000) and freezing on winter wheat leaves (Tasgin, et al., 2003).
Zinc application increased plant height, number of branches and leaf area on pepper (Dod, et al., 1989). (ElSeifi and Esmael, 1997) reported that zinc treatments accelerated flowering and increased weight of pods/plant
on okra. (Sawan, et al., 2001) found that Zn is required in the synthesis of tryptophan, which is a precursor in
the synthesis of indole-3-acetic acid, a hormone that inhibits abscission of squares and bolls. Also, this nutrient
has favorable effects on the photosynthetic activity of leaves and plant metabolism, which might account for
higher accumulation of metabolites in reproductive organs.
Therefore, the present study aimed to use foliar spray of salicylic acid and chelated zinc and their
combination on sweet pepper plants to improve growth and flower set as well as to increase the final yield and
quality of this plant under low temperature conditions during the autumn plantation, at Qaliobia region, in
the open field.
Materials and Methods
The field experiment was carried out during the two growing seasons of autumn 2009 and 2010, at the
experimental farm, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Egypt, in order to
investigate the effect of using foliar application of salicylic acid, chelated zinc and their combination on
vegetative growth, flowering, yield and fruit quality as well as photosynthetic pigments, minerals, enzyme
activity, total sugars, total free amino acids and crude protein of sweet pepper (Capsicum annuum L.) cv.
California Wonder in clay loam soil.
Imported sweet pepper seeds, cv. California Wonder, produced by Sun Seed Company, USA, were sown in
the shading screen nursery, using foam trays (209 eyes) on the 1st of July 2009 and 2010 seasons. Forty five
days after seed sowing, transplants were set up into the field (3-4 leaf stage). The area of the experimental plot
was 10.5 m2 consisted of five rows, each row was 3.5 m length and 0.7 m width. The plant distance was 40 cm
apart on one side. A total of 300 kg/fed. calcium superphosphate (15.5% P2O5) and 200 kg/fed. as ammonium
nitrate (33% N) were applied during soil preparation. Different recommended agricultural practices for this plant
were followed as recommended by the Ministry of Agric., Egypt. The average temperatures and R.H. % during
the growing seasons are presented in Table (A).
Table A: Average minimum, maximum and mean temperatures (Co) and R.H. % in Qaliobia during seasons of 2009 and 20010.
2009
2010
Mean
Month
Max temp.
Min temp.
Mean temp.
R.H. %
Max temp.
Min temp.
R.H. %
temp.
July
36.9
10.7
23.8
59.3
38
12.6
25.3
58.5
August
34.8
12.9
23.9
59.0
38.2
13.4
25.8
59.1
September
36.8
15.7
26.3
59.2
38.7
17.3
28.0
59.2
October
33.4
12.1
22.8
56.2
36.9
16.7
26.8
56.2
November
30.2
10.5
20.4
55.9
31.2
11.4
21.3
56.5
December
26.5
09.1
17.8
55.7
27.5
10.4
19.0
57.2
Central laboratory for Agri-climate, Dokki, Giza, Egypt.
Salicylic acid was used at three levels, namely 0 (control, sprayed with distilled water), 50 and 100 ppm,
applied as foliar application at 30, 50 and 70 days after transplanting. Also, chelated zinc (13% Zn chelated with
EDTA produced by U.A.D. Co. Egypt) was used at three levels, namely 0 (control, sprayed with distilled
water), 50 and 100 ppm, applied as foliar application at 40, 60 and 80 days after transplanting. The experiment
was arranged in a randomized complete block design with four replications.
The experiment included the following treatments:
1. Control (distilled water).
2. Salicylic acid at 50 ppm (SA50).
3. Salicylic acid at 100 ppm (SA100).
4. Chelated zinc at 50 ppm (Zn50).
5. Chelated zinc at 100 ppm (Zn100).
6. Salicylic acid at 50 ppm and chelated zinc at 50 ppm (SA50+ Zn50).
7. Salicylic acid at 50 ppm and chelated zinc at 100 ppm (SA50+ Zn100).
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8.
9.
Salicylic acid at 100 ppm and chelated zinc at 50 ppm (SA100+ Zn50).
Salicylic acid at 100 ppm and chelated zinc at 100 ppm (SA100+ Zn100).
Studied Characteristics:
Vegetative characteristics: six plants were chosen at random from four replications (from the inner rows) at
90 days after transplanting to study the following parameters: number of branches and leaves/plant, total leaf
area using the disk method according to (Derieux, et al., 1973) and leaf dry weight. Sample of each treatment
were dried in an oven at 70°C till the constant weight.
Chemical analysis: photosynthetic pigments, i.e., chlorophyll a, b and carotenoids, were determined, in the
fourth leaf from four plants, at 95 days after transplanting, colorimetrically as described by (Inskeep and Bloom,
1985). Total nitrogen, phosphorus and potassium were determined, in the fourth leaf, at 100 days after
transplanting and in fruits at harvest according the methods described by (Horneck and Miller, 1998; Sandell,
1950; Horneck and Hanson, 1998), respectively. Also, Zn concentration and uptake in leaves were determined
according to (Black, et al., 1965; Chapman and Pratt, 1961). Total free amino acids and total sugars were
determined in leaves according to (Rosad, 1957; Tomas and Dutcher, 1924). Total carbohydrates were
determined in fruits according to (Dubios, et al., 1956). Crude protein was calculated in leaves and fruits
according to the following equation: Crude protein (%) = Total nitrogen x 6.25 (A.O.A.C., 1990). Assay of
peroxidase, catalase and superoxide dismutase were determined in leaves according to (Kong, et al., 1999). In
fruits, total soluble solids (T.S.S.) were measured using a hand refractometer, vitamin C and titratable acidity
were determined according to the methods described by the (A.O.A.C., 1990).
Endogenous phytohormones were quantitatively determined in sweet pepper shoots at 95 days after
transplanting in the second season using High-Performance Liquid Chromatography (HPLC) according to
(Koshioka, et al., 1983) for auxin (IAA), gibberellic acid (GA3) and abscisi acid (ABA), while, cytokinins were
determined according to (Nicander, et al., 1993).
Yield: fruit setting percentage, plant samples from ten randomly selected plants were collected (number of
fruits per plant / number of flowers per plant using ten labelled plants from the 2nd and 3rd ridges in each plot).
The pepper fruits were harvested every 7 days.. Early yield was considered as the number of first four pickings,
marketable and estimated total yield per plant and feddan were recorded.
Fruit physical characters: ten fruits from each plot were taken at various intervals; fruit diameter, length,
size and flesh thickness were measured.
Statistical Analysis:
All data were subjected to the analysis of variance (ANOVA) using least significant difference (LSD) at
0.05 according to (Snedecor and Cochran, 1990).
Results and Discussion
Vegetative Characteristics:
The growth parameters of sweet pepper plants, i,e., number of branches and leaves, total leaf area, and dry
weight of leaves per plant, were significantly increased by all foliar applications with salicylic acid or chelated
zinc at 90 days after transplanting during two seasons as shown in Table (1). The interaction effect between
salicylic acid and chelated zinc foliar application with all concentrations gave the highest values of growth
parameters as compared with either individual foliar application or control plants. The maximum stimulatory
effect existed in plants treated with 100 ppm salicylic acid and chelated zinc at 50 ppm as foliar application
during the two seasons.
It could be concluded that sowing pepper seeds cv. California Wonder on the first of July
affected the vegetative growth due to low temperatures during the growth of the field open. As mentioned in
Table (A), the meteorological data showed that the average day air temperature during Aug., Sep., Oct., Nov.
and Dec. of 2009 season were 23.9, 26.3, 22.8, 20.4 and 17.8 ºC; meanwhile, it was 25.8, 28.0, 26.8, 21.3 and
17.3 ºC for Aug., Sep., Oct., Nov. and Dec. of 2009/2010 season, respectively. In addition, the relative humidity
was 59.0, 59.1, 56.20, 55.85 and 55.65 for Aug., Sep., Oct., Nov. and Dec. of 2009 season and 59.1, 59.2, 56.15,
56.45 and 57.15 for Aug., Sep., Oct., Nov. and Dec. of 2010 season, respectively. In other words, the
temperatures prevailing during the autumn plantation, at Qaliobia region, were the not favorable for pepper
plants grown in the open field and the tested treatments sustained plants to grow under these conditions.
The stimulatory effect of SA and Zn on different estimated characteristics of sweet pepper growth could be
attributed to the satisfactory effect of these components upon the photosynthetic pigments (Table 2), minerals
and bioconstituents (Table 3), endogenous phytohormones (Table 4) and activity of antioxident enzymes (Table
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5). In agreement with our results, (Gharib, 2007) on basil and (marjoram and Fathy, et al., 2000) on eggplant
mentioned that salicylic acid increased plant height, number of branches and leaves per plant and dry weight.
(Lei, et al., 2010) indicated that SA could alleviate the injury caused by low temperature on cucumber
seedlings. (Han, et al., 2011) reported that soybean growth correlated positively with concentrations of Zn.
Table 1: Effect of foliar application of salicylic acid and chelated zinc on vegetative characteristics of sweet pepper plant at 90 days after
transplanting in the two seasons (2009 and 2010).
Leaf area (cm2)/plant
Leaf dry weight
Treatments
No. Branches / plant
No. Leaves / plant
(g/plant)
2009 Season
Control
18.45
99.48
544.93
26.65
SA50
19.78
98.24
562.08
28.21
SA100
23.57
103.39
588.35
30.67
Zn50
21.76
105.15
601.34
29.91
Zn100
24.43
111.34
638.44
29.43
SA50+ Zn50
25.15
113.64
653.96
31.54
SA50+ Zn100
25.64
114.44
692.75
30.75
SA100 + Zn50
26.14
117.67
743.67
31.69
SA100+ Zn100
25.38
112.43
719.55
30.89
L.S.D. at 5%
3.03
6.99
48.97
1.65
2010 Season
Control
22.11
96.58
443.86
26.67
SA50
23.30
97.76
576.63
27.34
SA100
25.66
104.54
585.40
30.25
Zn50
22.57
112.95
609.29
29.21
Zn100
23.38
117.64
652.76
29.63
SA50+ Zn50
26.95
120.23
631.43
30.72
SA50+ Zn100
27.40
121.75
625.89
30.79
SA100 + Zn50
28.69
125.88
754.67
33.17
SA100+ Zn100
25.39
122.53
731.26
31.27
L.S.D. at 5%
2.35
7.78
35.87
1.72
Photosynthetic Pigments:
Data in Table (2) indicate that different photosynthetic pigments, chlorophyll a, b and carotenoids,
positively responded to the different foliar applications with salicylic acid and (or) chelated zinc during the two
assigned seasons. Also, the interaction between salicylic acid and chelated zinc gave the highest value in the
respect, comparing with the control plants. The present results are in agreement with those of (Sweify and
Abdel-Wahid, 2008) they found that application of SA increased chlorophyll a and b as well as carotenoids in
Syngonium podphyllum plants. Moreover, salicylic acid significantly increased chlorophyll a & b and
carotenoids (Shakirova, et al., 2003; Abdel-Wahed, et al., 2006; El-Mergawi, et al., 2007; Zaki and Radwan,
2011).
Table 2: Effect of foliar application of salicylic acid and chelated zinc on photosynthetic pigments (mg/g fresh weight) of sweet pepper
leaves at 95 days after transplanting in the two seasons (2009 and 2010).
Chlorophyll
a
Chlorophyll
b
Control
SA50
SA100
Zn50
Zn100
SA50+ Zn50
SA50+ Zn100
SA100 + Zn50
SA100+ Zn100
L.S.D. at 5%
0.511
0.565
0.587
0.578
0.590
0.612
0.623
0.647
0.689
0.061
0.318
0.322
0.354
0.367
0.385
0.411
0.418
0.434
0.445
0.033
Control
SA50
SA100
Zn50
Zn100
SA50+ Zn50
SA50+ Zn100
SA100 + Zn50
SA100+ Zn100
L.S.D. at 5%
0.545
0.552
0.564
0.568
0.583
0.622
0.631
0.643
0.678
0.087
0.332
0.345
0.360
0.378
0.382
0.423
0.428
0.442
0.461
0.043
Treatments
Chlorophyll
a+b
Carotenoids
0.829
0.887
0.941
0.945
0.975
1.023
1.041
1.081
1.134
0.124
0.367
0.377
0.387
0.393
0.396
0.498
0.511
0.522
0.535
0.112
0.877
0.897
0.924
0.946
0.965
1.045
1.059
1.085
1.139
0.153
0.354
0.366
0.380
0.387
0.392
0.450
0.533
0.542
0.557
0.134
2009 Season
2010Season
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This stimulative effect of the combination of SA and Zn might be due to their antioxidantal scavenging
effect to protect chloroplasts and prevent chlorophyll degradation by the toxic reactive oxygen radicals (Bowler,
et al., 1992; Aono, et al., 1993).
Minerals and Some Bioconstituents:
Data in Table (3) clearly indicate that foliar application with salicylic acid and (or) chelated zinc increased
N, P and K percent as well as Zn concentrations and uptake in sweet pepper leaves compared with those of
control plants in both seasons. Also, it could be noticed that SA at 100 ppm plus Zn at 50 ppm was superior in
this respect. Application of salicylic acid at 150 mg l-1 increased the uptake of N, P and K in wheat grains over
the control (Zaghlool, et al., 2001). In addition, (Cakmak, 2008) reported that zinc enhanced P accumulation in
plants.
On the other hand, foliar application with the two concentrations of SA and Zn gave the best value of total
sugars, total free amino acids and crude protein content in leaves of sweet pepper plants at 100 days after
transplanting during the two seasons. In this respect, high content of total sugars and some bioconstituents may
be a direct result for high rates of photosynthesis with great efficiency. That was preceded with large
photosynthetic area (Table, 1) and high content of photosynthetic pigments (Table, 2).
These results are in agreement with those obtained by (Shakivora, et al., 2003; Rashad, 2003). (Sarang, et
al., 2003) found also that the N and protein content, increased in Phaseolus vulgaris by foliar application of
salicylic acid at 0.1%. Additionally, the main function of anti-oxidants such as SA and Zn was the protection of
cell membranes and their binding transporter proteins (H+-ATP ase–membrane pumps), maintained their
structure and function against the toxic and destructive effects reactive oxygen species (ROS) during stress, in
turn, more absorption and translocation of minerals (Dicknson , et al., 1991).
Table 3: Effect of foliar application of salicylic acid and chelated zinc on minerals (D.W.%) and bio-constituents of sweet pepper leaves at
100 days after transplanting in the two seasons (2009 and 2010).
Total
Zn
Total free
Crude
N
P
K
Zn (ppm)
sugars
Treatments
(ppm)
amino acids
protein
%
%
%
uptake
(mg/g
cons.
(mg/g)
(%)
F.W)
2009 Season
Control
1.75
0.406
4.17
51.30
341.15
12.66
22.18
10.94
SA50
1.82
0.411
4.25
52.43
430.45
14.80
29.27
11.38
SA100
1.87
0.428
4.36
55.40
591.12
15.76
33.70
11.69
Zn50
1.94
0.431
4.42
55.80
552.98
13.80
31.82
12.13
Zn100
1.98
0.436
4.50
62.14
585.98
14.11
32.25
12.38
SA50+ Zn50
2.07
0.442
4.66
64.15
740.29
15.70
35.40
12.94
SA50+ Zn100
2.16
0.453
4.68
64.68
695.31
16.94
37.65
13.50
SA100 + Zn50
2.36
0.458
4.84
68.40
799.60
20.75
38.70
14.75
SA100+ Zn100
2.22
0.451
4.70
63.32
689.55
18.10
36.43
13.88
L.S.D. at 5%
0.28
0.021
0.12
4.18
22.74
1.25
3.54
1.15
2010 Season
Control
1.77
0.414
4.20
52.16
347.91
13.12
23.25
11.06
SA50
1.81
0.418
4.23
54.80
457.03
15.77
26.70
11.31
SA100
1.88
0.422
4.32
55.75
627.19
16.48
32.64
11.75
Zn50
1.96
0.429
4.38
60.11
613.72
14.17
33.15
12.25
Zn100
2.01
0.436
4.41
63.27
672.56
14.88
34.56
12.56
SA50+ Zn50
2.08
0.438
4.48
65.84
771.64
16.75
36.71
13.00
SA50+ Zn100
2.14
0.446
4.55
66.42
783.09
17.64
38.14
13.38
SA100 + Zn50
2.33
0.453
4.68
69.70
848.25
22.70
39.46
14.56
SA100+ Zn100
2.25
0.450
4.64
62.69
706.52
19.24
37.22
14.06
L.S.D. at 5%
0.34
0.224
0.11
4.22
25.18
1.31
4.06
1.87
Endogenous Phytohormones:
Endogenous phytohormones of sweet pepper leaves as affected by foliar application with salicylic acid or
chelated zinc are shown in Table(4). According to these results, all promoters (auxins, gibberellins and
cytokinins) were improved by application of salicylic acid and chelated zinc, but, abscisic acid was decreased.
Foliar application with salicylic acid at 100 ppm and chelated zinc at 50 ppm gave the maximum values in
auxins, gibberellins and cytokinins while it gave the highest reduction of abscisic acid in leaves of sweet pepper
at 95 days after transplanting during 2010 season. These data could also be of great influence upon different
vegetative and reproductive growth. Moreover, it has been reported that SA showed synergetic effect with auxin
and gibberellins (Datta and Nanda, 1985). Applied SA induced changeable in endogenous phytohormones of
tomato and other plants (Raskin, 1992; Mostafa , et al., 1996). In addition, The sustained level of salicylic acid
may be a prerequisite for the synthesis of auxin and (or) cytokinin (Metwally, et al., 2003).
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Table 4: Effect of foliar application of salicylic acid and chelated zinc on endogenous phytohormones (µg/10g FW) of sweet pepper shoots
at 95 days after transplanting in the second season ( 2010).
Promoters
Inhibitors
Treatments
Auxins
Gibberellins
Cytokinins
Abscisic acid
Control
28.67
125.40
6.42
0.948
SA50
32.40
133.25
6.68
0.564
SA100
40.18
135.60
6.77
0.536
Zn50
40.38
137.75
7.18
0.517
Zn100
41.51
140.18
8.14
0.428
SA50+ Zn50
42.63
139.69
8.96
0.419
SA50+ Zn100
45.78
142.77
9.54
0.318
SA100 + Zn50
46.84
148.70
9.76
0.304
SA100+ Zn100
43.73
136.15
8.42
0.325
Antioxidant Enzyme activities:
Plants possess antioxidant system in the form of enzymes such as peroxidase (POX), catalase (CAT) and
superoxide dismutase (SOD). Data in Table (5) clearly show that different applied treatments induced increases
in the peroxidase, catalase and superoxide dismutase activities as compared with control plants in leaves of
sweet pepper at 100 days after transplanting during 2009 and 2010 seasons. These increases might be due to
their direct scavenging function against the toxic free radicals and their promotional effects on synthesis of
internal protective antioxidants. Similar results were obtained by (Noctor and Foyer, 1998; Xu, et al., 2006). In
addition, (Sarang, et al., 2003) found that the N and protein content as well as nitrate reductase activity were
increased in Phaseolus vulgaris by foliar application of salicylic acid at 0.1%'. (Hayat and Ahmad, 2007) found
that application of SA or ASA to maize plants caused a decrease in net photosynthesis under normal growth
conditions (22/20 oC); however, it induced chilling tolerance at low temperatures (2 oC) by activating
antioxidant enzymes. In this respect, (Jing-Hua, et al., 2008) found that the suitable exogenous SA (1.0 mmol/L)
enhanced cold tolerance in watermelon through activations of antioxidative capacity, such as, guaiacol
peroxidase (G-POD), ascorbate peroxidase (ASA-POD), catalase (CAT), superoxide dismutase (SOD) and
glutathione reductase (GR). The activities of antioxidative enzymes were significantly increased cold tolerance
in watermelon after being treated with suitable exogenous SA (1.0 mmol/L). However, higher concentration of
exogenous SA decreased the activity of antioxidative enzymes, consequently, weakened the capacity of cold
tolerance in watermelon.
Table 5: Effect of foliar application of salicylic acid and chelated zinc on enzyme activity (µg/g FW/ h ) of sweet pepper leaves at 100 days
after transplanting in the two seasons (2009 and 2010).
Treatments
Peroxidase
Catalase
Superoxide
dismutase
Seasons
2009
2010
2009
2010
2009
2010
Control
124.0
143.0
92.7
89.9
208.2
196.9
SA50
143.2
145.4
112.5
110.8
216.4
194.9
SA100
157.8
166.2
102.2
109.6
217.0
215.2
Zn50
144.6
153.4
106.8
113.9
220.0
214.8
Zn100
161.5
165.6
120.0
110.9
232.3
221.0
SA50+ Zn50
175.7
182.7
123.4
126.9
221.4
230.9
SA50+ Zn100
190.3
196.4
135.5
121.5
249.5
246.8
SA100 + Zn50
184.7
199.1
139.8
132.8
267.9
159.5
SA100+ Zn100
185.4
198.8
135.2
128.9
267.5
155.9
Yield:
Data in Table (6) indicate that significant increases in fruit set, early, marketable and estimated total yield
were existed with the tested foliar applications during the two assigned seasons compared to control treatment.
The combination treatments gave the highest values especially SA at 100 ppm plus Zn at 50 ppm which ranked
the first in this respect.
Such increments in flowering and fruit yield due to treating the plants with salicylic acid and chelated zinc
treatments might be connected with their effect on increasing the vegetative growth parameters (Table, 1)
photosynthetic pigments (Table, 2) minerals and some bioconstituents (Table, 3) which affect plant growth and
in turn increased it’s productivity. This fact offered an explanation for SA induced resistance of plants to low
temperature (Hayat and Ahmed, 2007). Similar results were obtained by SA on broad bean and dry bean
(Awasthi, et al., 1997; Zaghlool, et al., 2001), respectively), also, by Zn on tomato (Fathy, et al., 2000). Surface
application of Zn after flowering was ineffective. In addition, foliar application of salicylic acid significantly
increased yield and its components of maize (Abdel-Wahed, et al., 2006) and basil and marjoram plants
(Gharib, 2006). Han, et al., 2011) reported that soybean yields correlated positively and best with concentrations
of Zn. Foliar sprays resulted in greater yield responses and Zn-use efficiency than other methods.
429
Res. J. Agric. & Biol. Sci., 7(6): 423-433, 2011
Table 6: Effect of foliar application of salicylic acid and chelated zinc on flowering and fruiting of sweet pepper plants in the two seasons
(2009 and 2010).
Early yield (g/
Marketable yield
Total yield
Estimated total
Treatments
Fruit set (%)
plant)
(g/ plant)
(g/plant)
yield (ton/fed.)
2009 Season
Control
38.37
127
655
911
12.36
SA50
38.67
133
674
973
13.21
SA100
42.97
137
680
994
13.49
Zn50
43.92
140
677
1080
14.66
Zn100
43.74
151
699
1184
16.07
SA50 + Zn50
39.93
154
705
1132
15.36
SA50 + Zn100
38.64
167
751
1153
15.65
SA100 + Zn50
42.18
176
850
1220
16.56
SA100 + Zn100
40.80
169
800
1197
16.25
L.S.D. at 5%
2.15
12
46
49
1.35
2010 Season
Control
39.10
133
655
888
12.05
SA50
39.05
137
674
905
12.28
SA100
42.71
142
680
931
12.64
Zn50
43.36
156
677
1023
13.88
Zn100
42.41
163
685
1100
14.93
SA50 + Zn50
42.95
172
691
1147
15.57
SA50 + Zn100
40.41
179
743
1184
16.07
SA100 + Zn50
41.59
188
881
1201
16.30
SA100 + Zn100
40.74
181
816
1174
15.93
L.S.D. at 5%
1.66
13
37
63
1.27
Fruit quality:
Concerning physical characters, data presented in Table (7) and Figure (1) indicate that the different
sprayed treatments increased physical characters (diameter, length, size and flesh thickness) of sweet pepper
fruits. Also, it could be noticed that SA at 100 ppm plus Zn at 50 ppm gave the highest values of physical
characters of sweet pepper fruits followed by SA at 50 ppm plus Zn at 100 ppm. Such increments in physical
characters might be agents due to the effect of different treatments on vegetative growth (Table 7).
As for the mineral and bioconstituents, data presented in Table (8) indicate that different sprayed treatments
increased N, P, K, crude protein and total carbohydrate concentrations of sweet pepper fruits. Also, it could be
noticed that SA at 100 ppm plus Zn at 50 ppm gave the highest values of these constituents. Such increments in
chemical fruit quality agents due to the effect of different treatments are connected with the increase in
photosynthetic pigments which in turn affect the rate of organic compound assimilation and consequently
increased such assayed organic constituents.
Table 7: Effect of foliar application of salicylic acid and chelated zinc on the physical characters of sweet pepper fruits in the two seasons
(2009 and 2010).
Flesh thickness
Treatments
Diameter (cm)
Length (cm)
Size (cm3)
(mm)
2009 Season
Control
4.8
5.7
141.3
0.341
SA50
4.9
5.5
152.1
0.348
SA100
5.1
5.3
157.2
0.354
Zn50
5.8
6.1
174.1
0.361
Zn100
5.4
6.7
185.7
0.358
SA50+ Zn50
5.5
6.7
207.0
0.365
SA50+ Zn100
5.6
6.9
216.4
0.367
SA100 + Zn50
5.8
8.0
229.4
0.374
SA100+ Zn100
5.6
7.6
218.8
0.370
L.S.D. at 5%
0.5
0.5
27.0
0.024
2010 Season
Control
4.2
5.1
131.8
0.344
SA50
4.1
6.3
140.6
0.343
SA100
4.9
5.9
144.6
0.349
Zn50
5.5
6.6
150.7
0.355
Zn100
5.6
6.9
179.3
0.362
SA50+ Zn50
5.7
6.9
185.4
0.362
SA50+ Zn100
5.6
7.0
202.4
0.365
SA100 + Zn50
5.7
8.2
218.4
0.368
SA100+ Zn100
5.5
7.3
212.9
0.366
L.S.D. at 5%
0.4
0.5
37.1
0.022
430
Res. J. Agric. & Biol. Sci., 7(6): 423-433, 2011
Fig. 1: Effect of foliar application of salicylic acid and chelated zing on the physical Character of sweet pepper
fruits in the second season 2010.
Table 8: Effect of foliar application of salicylic acid and chelated zinc on NPK and some bio-constituents of sweet pepper fruits in the two
seasons (2009 and 2010).
Crude protein
Total carbohydrates
Treatments
N%
P%
K%
(%)
(mg/g D.W.)
2009 Season
Control
1.32
0.374
2.31
8.25
612.25
SA50
1.36
0.380
2.43
8.50
621.16
SA100
1.38
0.391
2.45
8.63
632.24
Zn50
1.40
0.396
2.52
8.75
642.64
Zn100
1.42
0.405
2.57
8.88
646.80
SA50+ Zn50
1.46
0.411
2.62
9.13
651.85
SA50+ Zn100
1.47
0.418
2.69
9.19
667.74
SA100 + Zn50
1.52
0.426
2.82
9.50
684.24
SA100+ Zn100
1.48
0.409
2.75
9.25
674.65
L.S.D. at 5%
0.41
0.030
0.12
1.12
26.14
2010 Season
Control
1.34
0.368
2.36
8.38
618.72
SA50
1.35
0.386
2.40
8.44
622.11
SA100
1.39
0.395
2.41
8.69
631.90
Zn50
1.43
0.402
2.49
8.94
636.84
Zn100
1.44
0.408
2.60
9.00
644.16
SA50+ Zn50
1.45
0.412
2.64
9.06
651.42
SA50+ Zn100
1.48
0.422
2.67
9.25
666.33
SA100 + Zn50
1.54
0.431
2.86
9.63
689.28
SA100+ Zn100
1.49
0.416
2.80
9.31
675.13
L.S.D. at 5%
0.39
0.050
0.14
1.13
28.76
In addition, data in Table (9) showed that all treatments increased the amount of vitamin C, total soluble
solids and titratable acidity in sweet pepper fruits during the two seasons. Also it could be noticed that the
highest increase of vitamin C was existed with the application of SA at 100 ppm plus Zn at 50 ppm.
Such increment in fruit parameters due to salicylic acid and Zn treatments may be attributed to the role of
them on increasing the vegetative growth (Table 1), photosynthetic pigments and uptake of N, P, K (Table, 3).
431
Res. J. Agric. & Biol. Sci., 7(6): 423-433, 2011
The same results nearly were obtained for SA in tomato (Fathy, et al., 2000) and for bean (Zaghlool, et al.,
2001). In this respect, (Hayat and Ahmed, 2007) found that salicylic acid is a plant growth regulator that
increases plant bioproductivity.
Table 9: Effect of foliar application of salicylic acid and chelated zinc on fruit vitamin C, TSS and titratable acidity of sweet pepper in the
two seasons (2009 and 2010).
Vitamin C
Treatments
Total soluble solids (%)
Titratable acidity (%)
(mg/100g F.W)
2009 Season
Control
107.20
3.11
0.346
SA50
113.40
3.54
0.355
SA100
116.18
3.62
0.361
Zn50
115.78
3.70
0.368
Zn100
119.95
3.73
0.371
SA50+ Zn50
126.33
3.78
0.377
SA50+ Zn100
129.65
3.81
0.379
SA100 + Zn50
133.42
3.96
0.386
SA100+ Zn100
131.70
3.84
0.384
L.S.D. at 5%
4.32
0.87
0.060
2010 Season
Control
110.62
3.23
0.351
SA50
111.94
3.60
0.356
SA100
117.40
3.65
0.365
Zn50
122.66
3.79
0.371
Zn100
121.45
3.82
0.374
SA50+ Zn50
123.15
3.86
0.376
SA50+ Zn100
128.80
3.92
0.380
SA100 + Zn50
134.78
3.97
0.389
SA100+ Zn100
132.18
3.91
0.381
L.S.D. at 5%
5.12
0.92
0.050
In conclusion, long term exposure to low temperature prolonged cell cycle duration and resulted in a
decreased plant growth. The foliar application of salicylic acid and chelated zinc treatments were generally
effective in alleviating the injury caused by low temperature through stimulating the vegetative growth,
photosynthetic pigments, minerals and bioconstituents, endogenous phytohormones and enzymatic antioxidant
activities which could be reflected on yield and quality of sweet pepper fruit. Foliar spraying with salicylic acid
at 100 ppm combined with chelated zinc at 50 ppm being the most effective. However, further investigations are
required to elucidate the possible role of salicylic acid and chelated zinc on plant growth regulating activity. It is
postulated that the foliar spraying with salicylic acid plus chelated zinc at low temperature during autumn
planting may positively regulated the pepper growth and thus improved the productivity.
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