Acta Physiol Plant (2014) 36:3147–3155 DOI 10.1007/s11738-014-1662-1
ORIGINAL PAPER
Morphological and physiological response of tomato (Solanum lycopersicum L.) to natural and synthetic cytokinin sources: a comparative study Azra Yasmeen • Wasif Nouman • Shahzad Maqsood Ahmed Basra Abdul Wahid • Hafeez-ur-Rehman • Nazim Hussain • Irfan Afzal
•
Received: 13 February 2014 / Revised: 26 August 2014 / Accepted: 26 August 2014 / Published online: 2 October 2014 Ó Franciszek Go´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako´w 2014
Abstract Among the natural plant growth stimulants, moringa has attained enormous attention due to its leaf composition being enriched with cytokinin, antioxidants and minerals. Exogenous application of moringa leaf extract (MLE) improves productivity in many crops. This study investigated the potential of MLE with different dilutions, i.e., MLE0, MLE10, MLE20 and MLE30 (0, 10, 20 and 30 times diluted in water, respectively) to improve the performance of tomato. Foliage-applied water and benzylaminopurine (BAP, 50 mg L-1) were taken as controls. Among treatments, foliar-applied MLE30 produced maximum vegetative and flowering branches, number of flowers and heaviest fruits per plant of tomato in comparison with synthetic BAP and other treatments. A similar increase in vegetative and flowering branches was recorded for root-applied MLE20 including BAP. Foliageapplied MLE30 also increased chlorophyll (a) pigments and leaf total soluble proteins than other stimulants used. This increase was followed by enhanced antioxidant Communicated by A. Gniazdowska-Piekarska. A. Yasmeen (&) N. Hussain Department of Agronomy, Bahauddin Zakariya University, Multan, Pakistan e-mail:
[email protected] W. Nouman Department of Forestry & Range Management, Bahauddin Zakariya University, Multan, Pakistan S. M. A. Basra Hafeez-ur-Rehman I. Afzal Department of Crop Physiology, University of Agriculture Faisalabad, Faisalabad, Pakistan A. Wahid Department of Botany, University of Agriculture Faisalabad, Faisalabad, Pakistan
activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), total phenolics in leaves and fruit lycopene contents of tomato. In general, foliar application of MLE30 was more effective as natural biostimulant to improve growth, productivity and fruit quality of tomato as compared to synthetic BAP and its root application. Keywords Antioxidants Biostimulant Growth Plant secondary metabolites Quality
Introduction Tomato (Solanum lycopersicum L.) is a climacteric fruit and an excellent source of vitamins C and E, and other phytochemicals, b-carotene, lycopene and phenolic compounds (Raffo et al. 2002). As vegetable, the presence of high fiber content, low caloric value and large concentration of vitamins, minerals and polyphenols make the tomato an excellent nutritional and physiological crop (Dorais et al. 2008). However, the use of synthetic growth promoters to increase crop productivity reduces the nutritional quality of tomato and the grower’s choice of the use of natural bioregulators has been increasing. For instance, exogenously applied seaweed extracts increased photosynthetic pigments, proteins, phenols, total soluble sugars, starch, lycopene and vitamin C of tomato (Kumari et al. 2011). Tomato leaves were found to be green for a longer period when supplied with soil or foliage seaweed extracts (Whapham et al. 1993). Such enhancement was the result of auxin- and cytokinin-like activity and the presence of macro- and micronutrients in seaweed extracts. Likely among synthetic stimulators, cytokinin application as zeatin enhances flowering (Ramirez and Hoad 1981), as BAP (benzylaminopurine) promotes cell division, auxiliary bud
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formation and shoot multiplication (Sutter 1996). Nonetheless, crops usually supplied with natural organic source have high nutritional properties, as found in tomato juice enriched with phenolic content and hydrophilic antioxidant activity (Caris-Veyrat et al. 2004), higher contents of vitamin C and carotenoids on fresh weight basis (Vallverdu-Queralt et al. 2012). Moringa oleifera Lam. is a relatively drought-tolerant tree and produces plenty of biomass with its leaf extracts showing growth-enhancing capabilities. Moringa leaf extract (MLE) possesses high antioxidant activity and is rich in plant secondary metabolites such as total phenols and ascorbic acid, making it a potential natural growth stimulant (Yasmeen et al. 2013a). These leaf extracts are also a source of zeatin, a natural derivative of cytokinin, vitamins and several mineral elements such as Fe, K and Ca (Siddhuraju and Becker 2003). The chemical composition of MLE (on dry weight basis) has revealed that it contains 3 ng g-1 DW (trans) zeatin riboside, 181.3 ng g-1 DW (cis) zeatin riboside, 3 ng g-1 DW dihydrozeatin riboside and 305 ng g-1 DW isopentenyladenosine (Basra et al. unpublished results). Therefore, MLE as growth promoter can be a natural and viable alternative supplement to synthetic sources applied to improve productivity in crop plants (Anjorin et al. 2010; Phiri and Mbewe 2010; Basra et al. 2011; Nouman et al. 2012a, b, c; Yasmeen et al. 2012). Exogenously applied MLE through seed or plant foliage is found to improve germination, seedling growth and productivity in many crops under normal and stress conditions (Basra et al. 2011; Yasmeen et al. 2012, 2013a, b, c; Rehman et al. 2013). Such improvements in plant productivity are related to greater leaf area, alteration in source–sink relationship and delayed senescence. Likewise, increased antioxidant activities, chlorophyll, ascorbic acid and total phenolic contents play their role in improving crop resistance behavior against stress (Yasmeen et al. 2013a, b). Nonetheless, no reports are available on exogenously applied MLE on morphological and biochemical changes related to nutritional enhancement of tomato fruits when compared with synthetic growth stimulants. The present study evaluated the comparative performance of MLE as a natural source with synthetic sources of cytokinin as growth stimulant applied through foliage or root medium in improving the productivity of tomato.
Materials and methods Preparation of moringa leaf extracts (MLE) Fresh leaves of young fully grown moringa trees located at the experimental area of the Department of Forestry, Range
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Management and Wildlife, University of Agriculture, Faisalabad, Pakistan were harvested. For MLE extraction, Nouman et al. (2012a) method was followed. The frozen moringa leaves were ground in a locally fabricated extraction machine. The extract was filtered through four layers of cheese cloth and the extract was centrifuged for 15 min at 8,0009g. Previous research findings illustrated that MLE is rich in antioxidants, total phenolics, ascorbic acid and mineral contents (Nouman et al. 2014). Furthermore, MLE biochemical and nutrient profile was studied and the data were presented on fresh weight (FW) basis, as in Table 1. Experimental treatments Various MLE dilutions (MLE0, MLE10, MLE20 and MLE30) were prepared by diluting MLE with distilled water at 1:0, 1:10, 1:20 and 1:30 ratios, respectively. The extracts were kept in a refrigerator at 18 °C until use. Synthetic plant growth stimulant, benzylaminopurine (BAP) (50 mg L-1) and water spray were used as controls for comparison. The foliar- and root-applied natural (MLE) and synthetic stimulants (BAP) including water were used (25 mL per plant) twice with 1 week interval on each of these growth stages, i.e., vegetative (15 days after emergence (DAE), flowering (50 DAE), early fruiting (65 DAE) and fruit ripening (90 DAE) stages as reported by Vijitha and Mahendra (2010).
Table 1 Biochemical/nutrient profile of Moringa oleifera leaf extract (MLE) Antioxidant activities and nutrient composition
Activity/ concentration ± SE
Enzymatic antioxidants (IU min-1 mg-1 protein) Superoxide dismutase (SOD) EC number (1.15.1.1)
196.47 ± 3.85
Peroxidase (POD) EC number (1.11.1.7)
153.36 ± 3.43
Catalase (CAT) EC number (1.11.1.6)
57.87 ± 2.38
Non-enzymatic antioxidants Total phenolic contents (mg g-1 GAE) Ascorbic acid (m mole g-1) Nitrogen (% of FW) Phosphorous (mg kg-1 FW) Potassium (mg kg-1 FW)
43.76 ± 2.65 0.51 ± 0.13 6.06 ± 1.21 3,491 ± 12.83 4,481.4 ± 15.97
Calcium (mg kg-1 FW)
30,614.1 ± 34.31
Magnesium (mg kg-1 FW)
30,081.7 ± 23.19
Zinc (mg kg-1 FW) Copper (mg kg
-1
FW)
Iron (mg kg-1 FW)
47.21 ± 3.57 4.1 ± 0.76 601.3 ± 5.35
Manganese (mg kg-1 FW)
57.99 ± 3.17
Boron (mg kg-1 FW)
27.22 ± 1.72
Acta Physiol Plant (2014) 36:3147–3155 Table 2 Weather data recorded during the experiment (2011–2012)
Year
2011 2012
3149
Months
Observations Maximum temperature (°C)
Minimum temperature (°C)
Average temperature (°C)
Relative humidity (%)
Rainfall (mm)
Sunshine (h)
November
27.3
12.2
19.7
58.9
0
8
December
21.9
9.1
15.5
68.9
14.6
6
January February
19.6 22.1
7.3 9.9
13.5 16
68 64.1
13.5 2.2
6.1 7.3
March
27.5
14
20.8
53.5
14
7.8
April
33.5
19.1
26.3
41.7
22.9
9.2
Table 3 Physico-chemical properties of the experimental soil Soil characteristics
Results
ECe
4.03 dS m-1
pH
7.53
SAR
12.65
TSS
45.06 m mol L-1
Na?
33.14 m mol L-1
-
Cl
?
K
22.97 m mol L-1 0.47 m mol L-1
ECe electrical conductivity, TSS total soluble salts, SAR sodium adsorption ratio
Plant establishment A pot study was conducted in 2011–12 under natural wirehouse conditions, at the Department of Crop Physiology, University of Agriculture Faisalabad, Pakistan. The weather data during the experimental period were obtained from the Agro-Climatology Cell, Department of Crop Physiology, University of Agriculture Faisalabad, Pakistan (Table 2). Seeds of tomato cv. Sahil were used as plant material. Five seeds were sown in each pot (30 cm diameter, 40 cm deep) containing 15 kg substrate (50 % sand and 50 % compost) with physico-chemical properties given in Table 3. After emergence, one seedling was maintained in each pot. The experimental design was completely randomized with factorial arrangement with six replications. The tomato vegetative and reproductive branches and the number of flowers and fruits from each plant were counted weekly and averaged. At fruit ripening or maturity, i.e., 1 week after the last exogenous application, all assays were performed. The tomato fruit weight of each plant was measured. Tomato leaves were analyzed for leaf chlorophyll (a, b) contents following the protocol devised by Arnon (1949). Total soluble proteins and enzymatic antioxidants Total soluble proteins were determined by Bradford assay (Bradford 1976). The concentration (mg mL-1) of total
soluble proteins was determined from a standard curve. For the standard curve, 10, 20, 30, 40 and 50 lg mL-1 were prepared from bovine serum albumin (BSA) by adding 400 lL dye stock (Biorad, USA) and distilled water. The absorbance was recorded at 595 nm using a spectrophotometer (Cary UV–VIS-4000, Varian Inc., Australia). The absorbance for the supernatant was determined in a similar way and the total soluble protein contents were quantified by placing absorbance readings in an equation derived from the standard curve. For enzymatic antioxidants, the leaf sample (0.5 g) was extracted in 5 mL of 50 mM phosphate buffer (pH 7.8); after centrifugation at 15,0009g at 4 °C, the supernatant was stored in Eppendorf tubes for further assay. The superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity was determined by following the procedure of Giannopolitis and Ries (1977) and Chance and Maehly (1955) after measuring the absorbance at 560, 240 and 470 nm, respectively. Leaf total phenolic contents Leaf total phenolic contents were determined by following the protocol described by Singleton and Rossi (1965), revised by Waterhouse (2001), using gallic acid as reference. For extraction and preparation of samples, 0.5 g of leaf sample was homogenized in 5 mL acetone (80 %). The mixture was filtered and the volume made up to 10 mL with the addition of acetone (80 %). Then, the reaction mixture was prepared by taking 20 lL sample or standard and adding 1.58 mL distilled water and 100 lL Folin–Ciocalteu reagent within a time frame of 30 s and 8 min. Then, it was left at 40 °C for 30 min after adding and mixing 300 lL sodium carbonate (20 %). Absorbance of the reaction mixture was read at 760 nm against the blank (80 % acetone). Total phenolic contents in samples were determined by plotting the calibration curve from 100, 150, 250 and 500 mg L-1 gallic acid standard solutions and reported as gallic acid equivalent (GAE).
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Fruit lycopene contents
Acta Physiol Plant (2014) 36:3147–3155
LSD 0.05 p= 4.305
(a)
For determination of fruit lycopene contents, the fruit sample (1 g) was ground/homogenized in acetone–hexane (4:6) according to Fish et al. (2002). The sample was shaken for 15 min with a magnetic stirrer. Then, 3 mL of deionized water was added to each sample. The sample was again shaken on ice for 5 min. The separation of the sample into two phases was achieved by leaving it at room temperature for 5 min. The absorbance of the hexane (upper) layer was observed at 503 nm and hexane alone was used as a blank (Ravelo-Perez et al. 2008). The lycopene contents were determined by using the formula: Lycopene content (lg g-1) = (A503 - 0.0007) 9 30.3/g tissue.
Number of vegetative branches per plant
Root
Foliar
35 30
a
a 25
ab bc
c
c efg
20
bc
a
b
fg
g
15 10 5 0
All the data were subjected to analysis of variance with the use of MSTAT computer program (MSTAT Development Team 1989). Duncan’s new multiple range test at the 5 % significance level of probability was used to separate the mean (Steel et al. 1997).
Results MLE and BAP (50 mg L-1) applied through foliage or root significantly affected tomato growth, productivity and biochemical attributes. The maximum number of vegetative branches per plant was significantly similar for foliarapplied BAP and root-applied MLE0 and MLE20, followed by root-applied MLE 30 (Fig. 1a). A minimum number of vegetative branches were recorded for foliarapplied undiluted (MLE0) and MLE10 including control treatments. Flower-bearing branches were also similar and the maximum was recorded for foliar-applied synthetic and natural BAP, MLE30 and root-applied MLE20 than the control including other treatments (Fig. 1b). Nonetheless, the response was similar between sources for vegetative and flowering branches, while root application of growth stimulants was better than foliage application for these traits. The highest number of flowers (Fig. 2a) and number of fruits per plant (Fig. 2b) were produced by foliage-applied MLE30 followed by synthetic BAP and MLE20. Minimum flower and fruit weights per plant were recorded for the control, including all other treatments. Maximum fruit fresh weight was recorded for foliage-applied MLE30 (Fig. 2c). The number of fruits per plant was similar for both foliar-applied natural moringa leaf extracts (MLE30) and synthetic benzylaminopurine (BAP) sources. However, the number of fruits per plant was similar for foliar- and
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LSD 0.05 p= 2.493
Number of flowering branches per plant
Statistical analysis
(b)
30
a
25
bc 20
cd
d
d
ab
a
ab d
d 15
e
e
10 5 0
Fig. 1 Influence of exogenously applied natural moringa leaf extracts (MLE) and synthetic cytokinin benzylaminopurine (BAP, 50 mg L-1) on a the number of vegetative and b flowering branches of tomato cv. Sahil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE, respectively). Means with different letters are statistically different (p \ 0.05) from each other
root-applied MLE20 with root-applied MLE30 and minimum for water spray and other treatments. Among the biochemical attributes, total leaf soluble protein contents were significantly similar between the two cytokinin sources and highest for foliar-applied BAP, MLE30 and MLE20, followed by root-applied MLE30 and BAP with similar protein contents. Nonetheless, minimum leaf protein contents were recorded for water spray control and other treatments (Fig. 3a). Exogenously applied natural and synthetic cytokinin sources also significantly affected the antioxidant activities in tomato leaves. Maximum SOD activity was observed for foliar-applied MLE30 which was statistically similar to foliar-applied BAP (Fig. 3b), while foliar-applied MLE 30
Acta Physiol Plant (2014) 36:3147–3155
3151
(a)
LSD 0.05p= 4.305 Root
Foliar
No of flowers per plant
120
a b
100
f f
d
de
e
80
f
c
d
d
f
60 40 20 0
LSD 0.05p= 4.667
(b)
120 a
No. of fruits per plant
100 80 e e
bc b
bcd
d
bc
a cd
e
e
60 40 20
were found for root- and foliar-applied control plants and MLE0. These antioxidant activities were statistically similar to root or foliar MLE10. No significant difference was found for leaf total phenolics between foliar-applied natural (MLE30) and synthetic (BAP) cytokinin sources, followed by foliar MLE20 and MLE10 (Fig. 4b). Minimum leaf phenolic contents were recorded in foliar- and root-applied water, MLE0 and root-applied MLE 20 which were statistically similar. Fruit lycopene contents were higher for foliarapplied MLE30 than BAP and were followed by MLE20 treatment. Minimum lycopene contents were recorded for root- and foliar-applied control, including all other treatments (Fig. 4c). Leaf chlorophyll contents were also affected by exogenously applied natural and synthetic growth stimulants as compared to the control. The highest chlorophyll a contents were found for foliar-applied BAP following MLE30 (Fig. 5a) and no improvement but even decrease was recorded for chlorophyll b contents between natural and synthetic sources as compared to water spray control (Fig. 5b).The tallest plants were observed in foliar-applied MLE30 and BAP (Fig. 5c).
Discussion
0
LSD 0.05p= 0.1977
(c)
Fruit fresh weight per plant (g)
6
a b
5
de
e 4
f f
cd c
f
cd
de
f
3 2 1 0
Fig. 2 Influence of exogenously applied natural moringa leaf extracts (MLE) and synthetic cytokinin benzylaminopurine (BAP, 50 mg L-1) on a the number of flowers, b fruits and c fruit fresh weight per plant of tomato cv. Sahil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20,30 times diluted MLE, respectively). Means with different letters are statistically different (p \ 0.05) from each other
exhibited the highest POD and CAT activities (Figs. 3c, 4a). In case of root application, no difference was found between MLE30 and synthetic BAP for SOD, POD and CAT activities. Minimum POD, SOD and CAT activities
Foliar-applied natural MLE30 and synthetic BAP improved the number of vegetative and flowering branches, number of flowers, and fruit and fruit fresh weight in tomato (Figs. 1, 2). The increased number of branches and shoot differentiation in tomato plants might be attributed to increased cell division and cell elongation in axillary buds due to release of apical dominance by cytokinin application (Mok and Mok 2001; Davies 2004). As MLE is rich in cytokinin, its exogenous application might alter the endogenous cytokinin levels, the enhanced contents stimulate cell division resulting in improved growth of fruits and shoots (Davies 1995). It is also hypothesized that cytokinin is involved in auxin-induced organogenesis by inhibiting its polar transport (Pernisova et al. 2009). Altered cytokinin production modified hormonal balance in shoots and ionic ratio such as K improves endogenous zeatin concentration in fruits and increased tomato yield by 30 % under salinity (Ghanem et al. 2011). Improved fruit weight in the present study was attributed to increased growth, as observed from increased vegetative and reproductive branches ultimately increasing the number of flowers and fruits per plant (Figs. 1, 2). The plant response to MLE varied with plant growth stage, mode of application and concentration of MLE used as observed during reproductive growth. This coincides with our previous findings in wheat where high yield response was found with foliar-applied MLE30 at the
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Acta Physiol Plant (2014) 36:3147–3155
(a)
LSD 0.05 p= 0.150
Total Soluble Protein (mg g-1 )
7 6
d
bc a
e
d
d d
(a) Root
15
ab d d
LSD 0.05p= 0.638
Foliar c
a
5 4 3 2
CAT (IU min -1 mg-1 protein)
Root
d cd
12
Foliar
bcdbcd cd d
bc bc
b
a
bc b
9
6
3
1
0 0
(b)
LSD 0.05p= 0.078 LSD 0.05p= 0.170
(b)
50
3
2
de de
de e
de
de
abc bcd a ab bcd cde
1
0
LSD 0.05p= 0.181
POD (IU min -1 mg-1 protein)
90
ih
gh
f e
d
b
c
a
cb
70 60 50 40 30 20 10 0
Fig. 3 Influence of exogenously applied natural moringa leaf extracts (MLE) and synthetic cytokinin benzylaminopurine (BAP, 50 mg L-1) on leaf a total soluble protein content, b SOD and c POD activity of tomato cv. Sahil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE, respectively). Means with different letters are statistically different (p \ 0.05) from each other
heading stage than at the tillering, jointing and booting stages (Yasmeen et al. 2012). Enhanced response was attributed to extended leaf duration, contributing to
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45
d
cd
cd
bcd
b
b
bcd
bc
cd
cd
35 30 25 20 15 10 5 0
(c)
100
80
Leaf total phenolics (mg GAE g-1 )
4
LSD 0.05p= 0.218
Fruit lycopene contents (µg g-1 )
SOD (IU min -1 mg-1 protein)
5
40
a
a
(c)
60 50
h gh
fg i
f i
e c
d
a e
b
40 30 20 10 0
Fig. 4 Influence of exogenously applied natural moringa leaf extracts (MLE) and synthetic cytokinin benzylaminopurine (BAP, 50 mg L-1) on leaf a CAT activity, b total phenolic contents and c fruit lycopene contents of tomato cv. Sahil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE, respectively). Means with different letters are statistically different (p \ 0.05) from each other
assimilates’ translocation toward grains to amplify carbohydrate supply during the reproductive phase (Yasmeen et al. 2012) as observed by increased fruit size and tomato
Acta Physiol Plant (2014) 36:3147–3155
3153
LSD 0.05p= 0.045
(a) Foliar
Root
Leaf chlorophyll a (mg g-1 )
2.5 2.0
c
a
b
c
d
e f
1.5
g h
h
i
1.0
g
0.5 0.0
LSD 0.05p= 0.064
(b)
Leaf chlorophyll b (mg g-1 )
2.5 2.0 a
1.5
b d
de
1.0
c
c e
f
g
h
0.5
i
i
0.0
LSD 0.05p= 0.078
(c)
Plant height (m)
5 4
a
b b c
3 g
e
f f
a b
c
d
2 1 0
Fig. 5 Influence of exogenously applied natural moringa leaf extracts (MLE) and synthetic cytokinin benzylaminopurine (BAP, 50 mg L-1) on leaf a chlorophyll a, b chlorophyll b and c plant height of tomato cv. Sahil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE, respectively). Means with different letters are statistically different (p \ 0.05) from each other
fresh weight for foliar-applied MLE tomato plants. MLE30 might result in improved growth by physiological events, such as enhanced tissue nutrient status and cytokinin levels inducing stay green characteristic due to greater chlorophyll a content (Fig. 5a, b). Thus, exogenous application of MLE would have additional beneficial effects on the crops as reported for seaweed extracts (Wu and Lin 2000). Enhancement in chlorophyll a due to foliar- and rootapplied MLE and BAP in our study (Fig. 5a) corresponds to increased chlorophyll a, b and carotenoid contents reported by foliar-applied and soil drench ? foliar treatments in tomato (Kumari et al. 2011). Similar increased levels of photosynthetic pigments in tomato leaves with the application of Ascophyllum nodosum extract (Whapham et al. 1993) and in maize (Zea mays) and bean (Phaseolus mungo) by the application of Sargassum seaweed extract (Lingakumar et al. 2004) are reported. Higher soluble protein contents of tomato leaf in the present study have also been reported in maize when 1 and 0.5 % Sargassum seaweed extract is applied (Lingakumar et al. 2004) and in sorghum (Sorghum bicolor) with 1.5 % liquid extract Hydroclathrus clathratus (Ashok et al. 2004). This increase in protein contents might be due to enhanced availability of minerals, which facilitated the source efficiency of leaves. The use of diluted extract caused greater increase in protein contents, due to enhanced nutrient supply facilitating carbon supply for protein synthesis as indicated by high chlorophyll contents (Anantharaj and Venkatesalu 2001). Improved enzymatic and non-enzymatic antioxidant activity of tomato leaves, particularly of SOD, POD, CAT and total phenolic contents, was recorded with foliarapplied MLE30 (Figs. 2, 3). The improved antioxidant activities might be due to higher antioxidants in moringa leaves (Nouman et al. 2012b; Yasmeen et al. 2013a). Yang and Poovaiah (2000) reported that SOD scavenges superoxide, which in turn gives H2O2 and O2-. Here, CAT and POD scavenged these reactive oxygen species in concert with phenolic compounds. This indicates that the nutritional quality of tomato may be linked with high phenolic contents to oxidative stress measured in tomato leaves. Such increase in antioxidant activities shows the strong defense mechanism, which may induce stress tolerance in plants leading to higher yield and fruit quality (Mittler 2002; Yasmeen et al. 2013a). A similar increase in antioxidant activity and phenolics had been reported in organically grown tomatoes (Oliveira et al. 2013). Injurious effects, i.e., age-related molecular degeneration, cancer and cardiovascular disorders in humans caused by various substances can be counteracted by improving
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lycopene contents (Dorais et al. 2008). Foliar application of diluted MLE30 and root-applied MLE0 produced the highest lycopene content as compared to the control. Similarly, the highest contents of lycopene in tomato fruit were produced by soil-applied 10 % seaweed extract (Kumari et al. 2011). It is evident that cytokinin-like substances or cytokinin present in aqueous extract of moringa leaf or Sargassum johnstonii extract facilitates the mobilization of nutrients to the fruit and improves lycopene contents (Kumari et al. 2011). Conclusion The present study suggests that between growth stimulants, foliar-applied MLE30 relatively improved flowering response and fruit weight of tomato in comparison to BAP. This was attributed to the growth-promoting composition of MLE, enhancing leaf phenolics and antioxidant activities affecting growth and fruit lycopene contents of tomato. Nonetheless, foliar application of MLE at optimized concentration can be a pragmatic alternative and natural source of biostimulant to improve the performance of tomato. Author contribution Azra Yasmeen: PhD student who planned and conducted this experiment and submitted in her PhD thesis. Wasif Nouman: conducted antioxidants’ and phenolics’ analysis. Shahzad Maqsood Ahmen Basra: Chairman of the PhD supervisory committee, who guided and supervised the project. Abdul Wahid: PhD supervisory committee member, who guided and co-supervised the project. Hafeez-ur-Rehman: assisted in the growth and yield analysis. Irfan Afzal: assisted in conducting lycopene analysis. Nazim Hussain: assisted in managing inputs such as seed, fertilizer and irrigation. Acknowledgments This research article is part of a PhD thesis. The authors are grateful to the Higher Education Commission, Pakistan, for providing financial support for this research work under the Indigenous PhD Fellowship Scheme Batch-IV.
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