physiological effects of salicylic acid and thiourea on growth and productivity of maize plants in...

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Physiological Effect of Salicylic Acid and Thiourea onGrowth and Productivity of Maize Plants in Sandy SoilA. A. Amin a , A. A. Abd El-Kader b , Magda A. F. Shalaby a , Fatma A. E. Gharib c , El-Sherbeny M. Rashad a & Jaime A. Teixeira da Silva da Botany Department, National Research Centre, Dokki, Cairo, Egyptb Soils and Water Use Department, National Research Centre, Dokki, Cairo, Egyptc Botany and Microbiology Department, Faculty of Science, Helwan University, Cairo, Egyptd Faculty of Agriculture and Graduate School of Agriculture, Kagawa University, Miki-cho,Ikenobe 2393, Kagawa-Ken, 761-0795, JapanAccepted author version posted online: 22 Jan 2013.

To cite this article: A. A. Amin , A. A. Abd El-Kader , Magda A. F. Shalaby , Fatma A. E. Gharib , El-Sherbeny M. Rashad &Jaime A. Teixeira da Silva (2013): Physiological Effect of Salicylic Acid and Thiourea on Growth and Productivity of MaizePlants in Sandy Soil, Communications in Soil Science and Plant Analysis, DOI:10.1080/00103624.2012.756006

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Physiological Effect of Salicylic Acid and Thiourea 1

on Growth and Productivity of Maize Plants in Sandy 2

Soil 3

A. A. Amin,1 A. A. Abd El-Kader,2 Magda A. F. Shalaby,1 Fatma A. E. Gharib,3 El-Sherbeny M. 4 Rashad,1 and Jaime A. Teixeira da Silva4 5

1 Botany Department, National Research Centre, Dokki, Cairo, Egypt 6

2 Soils and Water Use Department, National Research Centre, Dokki, Cairo, Egypt 7

3 Botany and Microbiology Department, Faculty of Science, Helwan University, Cairo, Egypt 8

4 Faculty of Agriculture and Graduate School of Agriculture, Kagawa University, Miki-cho, 9 Ikenobe 2393, Kagawa-Ken, 761-0795, Japan 10

Address correspondence to El-Sherbeny M. Rashad, Botany Department, National Research 11 Centre, Dokki, Cairo, Egypt; E-mail: [email protected]; or, Jaime A. Teixeira da 12 Silva, Faculty of Agriculture and Graduate School of Agriculture, Kagawa University, Miki-cho, 13 Ikenobe 2393, Kagawa-Ken, 761-0795, Japan; E-mail: [email protected] 14

ABSTRACT 15

This study aimed to investigate the response of vegetative growth, yield and some metabolic 16

constituents of maize grains cv. ‘Single Cross 124’ to a foliar application of salicylic acid (SA; 17

100, 200 and 400 mg L-1) and thiourea (TU; 500, 1000 and 1500 mgL-1), two bioregulators, either 18

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alone, or in combination. The foliar application of SA and TU alone significantly increased stem 19

diameter, number of leaves/plant, leaf area, total dry weight/plant, leaf area index, net assimilation 20

rate, specific leaf weight, as well as yield (i.e., ear length, ear diameter, number of grains/row, 21

number of rows/ear, 100-grains weight, grain yield/plant, grain yield/fed, harvest index and 22

shelling percentage) by increasing SA or TU concentrations up to 200 and 1500 mg L-1, 23

respectively. Salicylic acid and TU, when applied alone, significantly improved the nutritional 24

value and quality of maize grains by increasing crude protein, total soluble sugars, total free amino 25

acids and total soluble phenols. 26

Keywords: Maize (Zea mays L.), Salicylic acid, SA, Thiourea, TU, Growth characteristics, 27

Photosynthetic pigments, Yield, Biochemical constituents. 28

INTRODUCTION 29

Maize (Zea mays L.) is one of the principal food and forage crops around the world. It is the source 30

of a large number of industrial products and is grown under a wide range of climates (Wang et al., 31

2008). In recent decades, efforts have been made to improve the productivity of low-nutrient soils. 32

Inorganic fertilizers contain not only major elements necessary for plant growth, but also 33

anthropogenic sources of soil contamination with heavy metals (Sabiha-Javied et al., 2009). Maize 34

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plants are sometimes exposed to drought at different periods of growth. Super absorbent hydrogels 35

resist drought, improve soil quality (Woodhouse and Johnson, 1991), and assist with 36

environmental cleanup by reducing metal phytotoxicity by binding metals into non-toxic forms 37

(Ghanshyam and Swati, 2002). 38

Salicylic acid (SA) is a phenolic compound that occurs naturally in plants at very low 39

concentrations. Phenolics participate to some extent in auxin metabolism by regulating 40

indoleacetic acid (IAA) degradation or by controlling the formation of IAA conjugates in faba 41

bean (Vicia faba L.) and maize (Zea mays L.) (El-Mergawi and Abdel-Wahed, 2007). The 42

sustained level of SA may be a prerequisite for the synthesis of auxin and/or cytokinin, as shown 43

for mustard (Brassica juncea L.) (Syeed et al. 2010). Salicylic acid is a common plant-produced 44

signal molecule responsible for inducing resistance to a number of biotic and abiotic stresses, for 45

example soybean (Glycine max L.) (Karlidag et al., 2009; Syeed and Khan, 2010) and activates the 46

defense system in grapevine berry (Vitis vinifera L. cv. ‘Chardonnay’) (Bao et al., 2009). Salicylic 47

acid participates in the regulation of stomatal closure, nutrient uptake, chlorophyll and protein 48

synthesis, inhibition of ethylene biosynthesis, transpiration, and photosynthesis [e.g., in wheat 49

(Triticum aestivum L.) seedlings (Shakirova et al., 2003) and grapevine leaves (Wang et al., 50

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2010)]. Salicylic acid induces flowering, increase flower life, retards senescence and increases cell 51

metabolic rate. Salicylic acid treatments at 0.5 mM strongly or completely suppressed the 52

cadmium (Cd)-induced up-regulation of antioxidant enzyme activities in barley (Hordeum 53

vulgare) seedlings (Metwally et al., 2003). 54

Thiourea (TU) has been identified as an effective bioregulator imparting stress tolerance to 55

crops. It imparted salinity tolerance to Brassica juncea under field conditions (Srivastava et al., 56

2009). Thiourea plays several bioregulatory roles in crop plants, as the sulfhydryl group has 57

diverse biological activities (Jocelyn, 1972). It is involved in the phloem transport of sucrose and 58

in the substrate binding site of the amino acid carrier (McCormick and Johnstone, 1990). Thiourea 59

enhances the formation of the ternary complex, sucrose H+ carrier, thus improving translocation of 60

photosynthates while increasing the photosynthetically active leaf surface during grain filling in 61

cereals and stimulating dark fixation of carbon dioxide (CO2) in chickpea (Cicer arietinum) 62

embryos (Hernández et al., 1983). 63

The potent impact of SA and TU on various areas of plant structure and function has prompted 64

many investigators to apply them to several crop plants aiming to control growth patterns and 65

development coupled with enhanced systemic resistance to various harmful agents. Salicylic acid 66

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promotes some physiological processes and inhibits others depending on its concentration, plant 67

species, developmental stage and environmental conditions (e.g., on tomato (Lycopersicon 68

esculentum Mill. cv. ‘Sun Bright’) plants (Ding and Wang, 2003; Mateo et al., 2006). In faba bean, 69

SA at 1-5 mM increased growth criteria, but application of 3-5 mM SA reduced growth in maize 70

plants (El-Mergawi and Abdel-Wahed, 2007). Salicylic acid increased the number of flowers, 71

pods/plant and seed yield of soybean [Glycine max (L.) Merr. cv. ‘Cajeme’] plants 72

(Gutierrez-Coronado et al., 1998) and enhanced the growth of wheat (Shakirova et al., 2003), 73

yellow maize (Abdel-Wahed et al., 2006) and both faba bean and maize (El-Mergawi and 74

Abdel-Wahed, 2007). In contrast, SA at relatively high doses inhibited plant growth and 75

chlorophyll content of lupine (Lupinus termis L.) (Haroun et al 1998) and wheat plants (Iqbal and 76

Ashraf, 2006). Moreover, TU significantly increased vegetative growth, protein content and yield 77

of maize (Sahu et al., 1993), onion (Allium cepa L.) (Abdul Hye et al., 2002), mustard (Sahu et al., 78

2005), clusterbean [Cyamopsis tetragonaloba (L.) Taub] (Garg et al., 2006), and wheat (Anjum, 79

2008). 80

Thus SA and TU are expected to influence the growth and yield of maize plants grown in 81

sandy soil. Therefore, the present investigation was undertaken to study the impact of spraying 82

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maize (Zea mays L.) cv. ‘Single Cross 124’ plants with different concentrations of SA and TU, 83

individually or in combination, on some morphological criteria, yield as well as some metabolic 84

constituents of the grains in a bid to find one or more suitable levels that could enhance yield 85

relative to the control. 86

MATERIALS AND METHODS 87

Two field experiments were carried out in sandy soil at El-Saff, Giza Governorate, Egypt during 88

two successive seasons of two successive years. 89

Grains of maize (Zea mays L.) cv. ‘Single Cross 124’ were sown on the 15th June in both 90

seasons and in both years. The soil was sandy in texture with low fertility and poor in nitrogen 91

content. According to the F.A.O. (1970) soil classification, it is a Regosol. The main analytical 92

data of the soil was evaluated using standard methods according Black et al. (1965), and selected 93

soil samples were characterized by pH (7.58), electrical conductivity (EC) (2.2 dS m-1), OM 94

(0.12%), total calcium carbonate (CaCO3; 12.15%) and cation exchange capacity (CEC; 4.31 95

meq/100 mg). The selected soil samples had 88.7% sand, 7.50% silt and 3.80% clay and the 96

texture of the soil was sandy. The soil phosphorus (P), Cd, lead (Pb), and iron (Fe) contents were 97

extracted using the method of Cottenie et al. (1982). Available P, Fe, Pb, and Cd soil analysis 98

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showed that these values were 10, 28.5, 3.5 and 0.26 mg L-1, respectively. The absorbent material 99

used was a mixture of anionic hydrogel (polyacrylamide K, polyacrylated, 30% anionicity) and 100

cationic hydrogel (polyacrylamide, allylamine hydrochloride gel, 20% cationicity) at a ratio of 2:3. 101

The experimental design was a split plot with four replications. The SA treatment occupied the 102

main plots and TU treatments were allocated at random in sub-plots. The plot area was 10.5 m2 103

(3.0 m × 3.5 m) and consisted of four rows 70 cm apart and the hills along rows were 20 cm apart. 104

Calcium super-phosphate (15.5% P2O5) was pre-sown at 100 kg fed-1. to the soil; similarly, 105

nitrogen fertilizer was applied at 120 kg N fed-1. Ammonium nitrate (33.5% N) was applied in two 106

equal doses at 21 and 35 days after sowing. 107

In both seasons, a foliar spray was applied twice to maize plants during vegetative growth (at 108

45 and 60 days from sowing), with SA at 100, 200 and 400 mg L-1 and/or TU at 500, 1000 and 109

1500 mg L-1 (i.e., singly and in combination, in all possible permutations). The interaction of 110

different concentrations of both compounds was also assessed in addition to untreated plants 111

(control). 112

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Plant growth characters measured at silky (75 days after sowing (DAS)) and milky (90 DAS) 113

stages (i.e., green yield) were: plant height (PH), stem diameter (SD), leaf number (LN), dry 114

weight/plant (DW), leaf area (cm2 plant-1) (LA) according to Bremner and Taha (1966), leaf area 115

index (LAI) according to Watson (1952), specific leaf weight (SLW) (mg cm-2) according to 116

Pearce et al. (1969), crop growth rate (CGR) (mg/cm2/days) according to Abdel-Gawad et al. 117

(1980) and net assimilation rate (NAR) (mg/cm2/day) as given by Watson (1958) 15 days after 118

each spray. The photosynthetic pigment [chlorophylls (Chl) a and b, carotenoids as well as total 119

pigments] content of fresh leaves was also determined (Saric et al., 1967) at both silky and milky 120

stages. 121

At the time of harvest (105 DAS), the mean values of yield and its related parameters, i.e., ear 122

length (EL), ear diameter (ED), row number (RN), grain number (GN), 100-grain weight 123

(100-GW), grain yield/plant (GY/P), grain yield/fed. (GY/F), harvest index (HI) and shelling 124

percentage (SHP) were determined. Grains were harvested from each treatment to determine the 125

fresh weight of grains (GFW) and percentage oil (PO) by a Soxhlet apparatus according to 126

A.O.A.C. (1975). Representative plant samples were taken from each treatment and dried in an 127

electric oven with a drift fan at 70°C for 48 h until constant dry weight was achieved. Dry samples 128

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of leaves and grains were used to determine total soluble sugars (TSS) and total carbohydrate in 129

grains (GTC) (Dubois et al., 1956). Crude protein percentage (CPP) was calculated by multiplying 130

the values of total nitrogen by 6.25 (A.O.A.C, 1988). Total phenols (TPH) were determined 131

according to Diaz and Martin (1972). The method of Plummer (1978) was used to estimate total 132

free amino acids. 133

Data for both growing seasons was carried out according to Snedecor and Cochran (1990). 134

Data was combined since the CV% for each season’s data was < 5%. Data was analyzed by 135

ANOVA, and treatment means were compared using Fisher’s least significant difference (LSD) at 136

α = 0.05. 137

RESULTS 138

Growth Parameters 139

Data presented in Tables 1, 2, and 3 show that foliar application of SA either separately at 100, 200 140

and 400 mg L-1 and TU at 500, 1000 and 1500 mg L-1 or any of their combinations, promoted 141

almost all growth criteria compared to corresponding untreated control plants (i.e., neither treated 142

with SA or TU). In all cases, the increments in growth parameters were often highly significant in 143

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comparison with untreated control plants. The most effective treatments on total dry weight/plant 144

were the combination of SA at 200 mg L-1 + TU at 1500 mg L-1 followed by TU alone at 1500 mg 145

L-1 for all growth parameters. 146

Foliar application of SA up to 200 mg L-1 significantly increased SD, LN, 4th LA, DW, LAI, 147

NAR and SLW compared to corresponding untreated control plants. 148

Furthermore, TU was more effective than SA in increasing vegetative growth of maize plants 149

at the two stages of growth (Tables 1 and 2). The increment in growth characters (i.e., PH, LN, 4th 150

LA, DW, LAI, NAR, and SLW was maximum with 1500 mg L-1 TU while Ln and CGR showed an 151

insignificant response compared to control plants at 90 DAS. 152

Regarding the combined effect of SA and TU on vegetative growth, similar significant 153

increases were obtained in some growth parameters using different concentrations of SA and TU. 154

SA at 200 mg L-1 + TU at 1500 mg L-1 enhanced growth parameters the most at the two stages of 155

growth (Table 3). 156

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Yield and Oil Content 158

Data presented in Tables 3 and 4 show that the application of SA increased maize yield (i.e., EL, 159

ED, RN, GN, 100-GW, GY/P, GY/F, HI and SHP) more than control plants. The most promising 160

results were for GY/F (increased 35.74% more than the control) and grain quality by increasing Po 161

(increased 29.32% more than the control) at 200 mg L-1 SA. 162

TU alone significantly increased maize yield and oil content. TU at 1500 mg L-1 increased 163

GY/F (increased 47.354% more than the control) while Po increased 26.35% more than the control 164

with 200 mg L-1 SA (Table 4). In all cases, the increments in maize yield and oil quality were often 165

highly significant in comparison with untreated controls. 166

Furthermore, maize yield was far more sensitive to the interaction between SA and TU. The 167

highest increase in maize yield (100-Gw, GY/P and SHP increased 18.30, 16.27 and 21.24% more 168

than their controls, respectively) were obtained by foliar application of 200 mg L-1 SA + 1500 mg 169

L-1 TU followed by 200 mg L-1 SA + 1000 mg L-1 TU for all parameters (Table 3). 170

171

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Photosynthetic Pigments 172

Data presented in Tables 5 and 6 show that Chl a and b, carotenoids and TPP in the leaves of maize 173

plants reached a maximum value at 90 DAS. Generally, foliar application of either SA or TU at 174

any concentration or their combination significantly increased the Chl a and b, carotenoids and 175

consequently the TPC more than controls at 75 and 90 DAS. The most effective concentrations 176

were 200 and 1500 mg L-1 of either SA or TU, respectively and their combination at the two stages 177

of growth. 178

Foliar spray of maize plants with SA at 100, 200 and 400 mg L-1 significantly increased 179

photosynthetic pigments compared to untreated plants (Table 5). The highest recorded value of 180

Chl a and b, carotenoids and TPP in the leaves of maize plants was obtained with 200 mg L-1 SA at 181

the two stages of growth, while TU up to 1500 mg L-1 also significantly increased these pigments 182

(Table 5). 183

Moreover, the interaction between SA and TU significantly increased Chl a and b, carotenoids and 184

Tpp content in the leaves of maize plants more than controls at the two stages of growth (Table 6), 185

the most effective treatment being SA at 200 mg L-1 + TU at 1500 mg L-1. 186

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Chemical Constituents 187

Data presented in Table 7 shows that foliar application of either SA or TU at any concentration 188

significantly increased the crude protein %, total carbohydrates in the grains and Tss percent, total 189

free amino acids and TPH contents (mg g-1) in the leaves and grains of maize compared with 190

controls at 105 DAS (i.e., the harvest date). The most effective treatment was 200 and 1500 mg L-1 191

of either SA or TU, respectively. 192

Furthermore, the results obtained indicate that the highest level of TSS, percent total amino acids 193

and phenolic compounds in maize grains was obtained for either 200 mg L-1 SA or 1500 mg L-1 194

TU. 195

DISCUSSION 196

The present study indicates that the application of SA up to 200 mg L-1 and TU up to 1500 mg L-1, 197

individually or in combination, greatly promotes the vegetative growth and dry matter production 198

of maize plants, possibly through participation in the synthesis of auxin and/or cytokinin, 199

enhancement of cell division and Chl accumulation. In lupine seedlings, SA stimulated the growth 200

through direct interference with the enzymatic activities responsible for biosynthesis and/or 201

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catabolism of growth-promoting and -inhibiting substances (El-Bahy, 2002). Similarly, low 202

concentrations of SA enhanced the growth of soybean (Gutierrez-Coronda et al., 1998), wheat 203

(Iqbal and Ashraf, 2006; Amin et al., 2008b) and maize (El-Mergawi and Abdel-Wahed, 2007), 204

whereas high concentrations inhibited the growth of lupine (Haroun et al., 1998) and wheat (Iqbal 205

and Ashraf, 2006). Thiourea showed, in this study, a much better ability than SA (200 mg L-1) to 206

promote growth and yield of maize. Thiourea increase nitrogen uptake, metabolic processed and 207

hence increased the clusterbean growth and dry matter accumulation (Burman et al., 2004). 208

Thiourea also promoted growth and photosynthetic pigments in maize (Sahu et al., 1993), onion 209

(Abdul Hye et al., 2002), clusterbean (Garg et al., 2006), two sunflower cultivars (Amin et al., 210

2008a) and wheat (Anjum, 2008). Intuitively, the combination of SA and TU more effectively 211

increased vegetative growth, dry matter production and yield of maize plants than single 212

treatments. 213

Maize yield and the quantity of oil was significantly enhanced by SA, especially at 200 mg L-1. SA 214

increased grains production/ plant and/or PO formation and consequently OY/P and OY/F. 215

Salicylic acid may increase the existing polyamine pool and subsequently retard senescence. Rice 216

grain filling, plumpness and 1000-seed weight were positively correlated with polyamine contents 217

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(Yang et al., 1996). The application SA has been reported to increase growth, essential oil yield 218

and total polyamine content of basil (Ocimum basilicum L.) and marjoram (Majorana hortensis) 219

plants (Gharib, 2006), yield and components of maize (Abdel-Wahed et al., 2006) and wheat 220

plants (Iqbal and Ashraf, 2006; Amin et al., 2008b). According to several authors, there was a 221

correlation between the stimulatory effect due to lower concentration of salicylate compounds on 222

growth and increases in the content and activity levels of endogenous growth and hormones 223

promoters; indole acetic acid, gibberellin and cytokinins compounds and antagonized the growth 224

inhibitory effect of abcisic acid while high concentration had opposite effect inducing growth 225

promoters. It might attribute to the effect on inhibiting growth promoters biosynthesis and/or 226

promoting its destruction or it might be due to the antagonistic of effect with the stimulatory action 227

of promoters through transformation of active forms into inactive forms, such effect led to the 228

hormonal imbalance thus changes in the endogenous growth hormones control and coordinate 229

plant growth: Zaky (1985) on linum, Leslie and Romani (1986) on radish seedlings, and Kord and 230

Hathout (1992) on tomato plants. Thiourea increased yield more effectively than SA by enhancing 231

photosynthetic activity, accumulating dry matter and, consequently, increased translocation and 232

accumulation of certain metabolites in plant organs, which affected their yield and its components 233

(Tables 2, 5, 7). Thiourea significantly increased the yield of maize (Sahu et al., 1993), onion 234

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(Abdul Hye et al., 2002), clusterbean (Burman et al., 2004; Garg et al., 2006), mustard (Sahu et al., 235

2005), soybean (Jagetiya and Kaur, 2006) and OY/F of two sunflower cultivars (Iqbal and Asharf, 236

2006; Amin et al., 2008a). 237

In this study, the combination of SA at 200 mg L-1+ TU at 1500 mg L-1 was the best treatment to 238

increase the yield of maize plants. 239

Photosynthetic pigments of maize leaves were significantly enhanced by the application of SA or 240

TU and/or their combination (Tables 5, 6). SA and TU might concomitantly increase cell 241

metabolic rate and retard senescence by protecting and preventing chloroplasts from senescing and 242

retarding Chl destruction and/or increase Chl biosynthesis. SA participates in the regulation of 243

stomatal closure, nutrient uptake and Chl synthesis (Khan et al., 2003; Shakirova et al., 2003). SA 244

significantly increased Chl content in wheat (Amin et al., 2008b), maize (El-Mergawi and 245

Abdel-Wahed, 2007), two mustard cultivars (Syeed et al., 2010) and grapevine (Wang et al., 246

2010), whereas SA at 10-3 and 10-4 M negatively affected stomatal index and stomatal density of 247

pepper (Mendoza et al., 2002). Haroun et al. (1998) working on Lupinus termis showed that 248

salicylates at lower concentration (2.5 mM) caused significant increases in Chl content, while a 249

higher concentration (10 mM) inhibited it. The lower concentration enhanced the total 250

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photosynthetic activity (either photosystem I or II). Thiourea may increase N levels (structural 251

component of Chl) and enhance Chl accumulation, which would lead to a higher rate of 252

photosynthesis. The promotive effects of TU on photosynthetic pigments were observed for 253

clusterbean (Burman et al., 2004) and sunflower (Amin et al., 2008a). Similarly, in this study, the 254

combination of SA at 200 mg/l and TU at 1500 mg L-1 was the treatment that most increased the 255

photosynthetic pigments of maize leaves. 256

A foliar application of either SA or TU increased the CP, TSS, FAA and TPH in the dry grain of 257

maize, possibly due to the bioregulatory effect on enzymatic activity and translocation processes 258

from leaves to grains, linking or converting to other plant metabolites. A low dose of SA (2.5 mM) 259

significantly increased total carbohydrate content in lupine seeds (Haroun et al. 1998) while higher 260

doses (5 and 10 mM) significantly decreased total carbohydrate content in maize grains 261

(Abdel-Wahed et al., 2006). Salicylic acid increased the level of N, proteins and nitrate reductase 262

activity in Phaseolus vulgaris (Sarangthem and Singh, 2003), enhanced nutrient uptake, total free 263

amino acid as well as total polyamine contents in basil and marjoram plants (Gharib, 2006), and 264

enhanced N, P, K uptake and total soluble sugars of wheat grains (Amin et al., 2008b). Increased 265

mineral nutrient content seem to be involved in the mechanism of stress-tolerance and played an 266

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important role in enhancing the activity of enzymes responsible for drought resistance (Cherki et 267

al., 2002). On the other hand, TU significantly increased the content of total sugar, protein, and 268

total phenolic compounds (Burman et al., 2004; Garg et al., 2006; Anjum, 2008). Thus, combined 269

treatments of SA at 200 mg L-1 and TU at 1500 mg L-1 may be effective for enhancing TS, TFAA 270

and TPH. Salicylic acid typically alleviates the effects of heavy metal stress, for example, as seen 271

with Bromus tomentellus germination and growth under cadmium stress (Saberi et al., 2011), or 272

salt stress, as seen with Artemisia annua L. (Aftab et al., 2011). SA also serves as an enhancer of in 273

vitro organogenesis, in addition to its stress-modulating role (e.g., Malabadi et al., 2008). 274

In conclusion, SA and TU can be easily applied as a foliar application to maize plants in the field. 275

Application of SA at 200 mg L-1 and TU at 1500 mg L-1, singly or in combination, resulted in a 276

significant increase in every morphological attribute, particularly grain yield and quality. The use 277

of SA and TU as bioregulatory compounds thus open up a new avenue for increasing maize yield, 278

improving quality and provides an easy applicable solution to ensure sustainable agriculture in 279

sandy soil, extending the culture of this crop to other arid and semi-arid zones around the world. 280

281

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429

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Table 1. Effect of salicylic acid and thiourea on growth characters of maize plants at (A) 75 and 430 (B) 90 days from sowing (combined analysis of two seasons). 431

432

Growth characters

Treatments (mg L-1)

Total dry

weight (g)

plant-1

4th leaf area

(cm2 )

Number of

leaves

plant-1

Stem

diameter

(cm)

Plant height

(cm)

B A B A B A B A B A

279.0

1

189.0

8

401.2

6

369.1

0

15.7

2

15.0

1

1.9

4

1.6

6

269.8

1

176.0

1

0.0

Salic

ylic

acid

297.1

7

209.6

8

489.6

2

445.2

9

16.9

0

16.2

1

2.2

2

1.7

8

279.2

7

181.1

6

100

333.3239.2496.4466.316.916.42.41.8264.3174.2200

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4 5 4 8 7 7 1 6 5 5

319.2

6

212.4

9

446.8

0

406.4

7

15.8

9

15.7

0

2.3

6

1.8

1

258.4

6

165.3

4

400

17.09 20.01 41.54 37.08 N.S. 0.66

0.2

8

0.1

1

5.31 1.80 L.S.D. at 5%

282.4

2

190.5

9

413.0

1

376.2

8

15.8

7

15.4

5

1.8

6

1.5

9

266.6

8

177.4

5

0.0

Thio

urea

301.1

5

223.3

0

499.2

9

469.6

1

16.9

8

16.3

6

1.9

9

1.7

2

281.4

9

189.3

6

500

329.6

0

230.1

2

506.3

0

480.4

8

17.3

3

16.6

2

2.1

1

1.7

8

290.2

0

196.2

7

100

0

356.7246.2522.4492.217.617.12.21.8296.9199.1150

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6 8 1 3 0 1 9 0 1 8 0

19.02 31.80 67.80 49.33 N.S. 0.80

0.1

3

0.1

2

13.81 10.90 L.S.D. at 5%

433

434

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Table 2. Effect of salicylic acid and thiourea on growth characters of maize plants at (A) 75, (B) 90 435 and (C) 105 days from sowing (combined analysis of two seasons). 436

437

Growth characters

Treatments (mg L-1)

Specific leaf

weight

(mg/cm2/day)

Net assimilation

rate

(mg/cm2/day)

Leaf area

index (LAI)

Crop growth

rate

(mg/cm2/day)

B A B - C A - B B A B - C A - B

5.67 5.38 4.82 4.67 4.68 3.31 5.44 5.52 0.0

Salic

ylic

acid

6.48 5.60 5.69 6.03 5.62 4.49 5.82 6.61 100

6.84 6.72 5.77 6.44 5.76 4.62 5.93 6.70 200

6.79 6.34 5.37 5.86 5.59 4.40 5.71 5.89 400

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0.69 0.21 0.44 1.15 0.82 1.01 n.s. n.s. L.S.D. at 5%

5.74 5.56 4.90 4.78 4.70 3.48 5.38 5.60 0.0

Thio

urea

7.44 6.60 5.62 5.90 5.84 4.69 6.10 6.47 500

7.54 7.32 5.84 6.11 5.89 5.76 6.22 6.62 1000

8.36 7.68 5.89 6. 54 5.96 5.82 6.34 7.08 1500

1.67 1.02 0.64 1.10 1.11 1.16 n.s. n.s. L.S.D. at 5%

A : Silky stage (at 75 days from sowing)

B : Milky stage (at 90 days from sowing)

C : Ripe stage (at 105 days from sowing)

438

439

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Table 3. Effect of interaction between salicylic acid and thiourea on growth characters and yield 440 of maize plants at (A) 75, (B) 90 and (C) 105 days from sowing (combined analysis of two 441 seasons). 442

443

Yield of maize plants Growth characters of maize plants

Treatments

(mg L-1) Shelli

ng %

Grai

n

yield

(g)

plant

-1

100

grain

s

weig

ht (g)

Total dry

weight (g)

plant-1

4th leaf area

(cm2 )

Stem

diameter

(cm)

Plant height

(cm)

C C C B A B A B A B A

salicyl

ic acid

Thiour

ea

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72.31

239.

61

38.8

0

256.

67

189.

70

401.

81

351.

61

1.6

6

1.5

2

259.

11

180.

26

0.0

0.0

76.21

262.

32

39.7

1

278.

58

196.

61

432.

72

360.

30

1.7

9

1.6

7

270.

33

190.

64

100

80.49

271.

84

43.5

4

301.

30

211.

33

469.

45

379.

49

2.2

3

1.7

7

266.

67

187.

45

200

79.30

268.

93

41.6

2

290.

49

199.

42

450.

36

366.

58

2.0

2

1.7

2

264.

56

176.

08

400

76.58

241.

75

39.4

6

267.

21

194.

62

411.

54

359.

21

1.7

2

1.5

9

278.

90

189.

30

0.0

500

80.67

264.

60

41.3

8

296.

12

198.

11

447.

63

376.

39

1.8

0

1.6

9

282.

10

196.

21

100

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85.82

272.

58

44.6

0

332.

91

230.

97

468.

81

389.

20

2.2

9

1.7

6

270.

40

190.

23

200

82.76

269.

67

42.2

9

312.

06

221.

60

459.

72

380.

61

2.1

2

1.7

0

269.

50

183.

36

400

79.90

244.

49

40.2

1

272.

80

196.

88

426.

90

364.

48

1.7

6

1.5

3

280.

68

194.

47

0.0

1000

81.13

269.

30

42.3

3

337.

70

229.

79

458.

10

378.

75

2.0

5

1.6

6

287.

59

198.

60

100

87.58

276.

51

45.5

5

356.

50

249.

51

472.

26

389.

66

2.3

3

1.8

0

274.

41

191.

23

200

84.60

271.

19

43.6

4

350.

60

238.

60

460.

70

386.

57

2.1

9

1.7

8

270.

13

187.

24

400

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80.30

248.

33

40.6

6

296.

40

201.

42

433.

30

369.

84

1.7

9

1.5

5

284.

45

196.

63

0.0

1500

82.49

271.

42

42.7

0

339.

30

219.

33

466.

79

372.

11

2.1

6

1.7

1

289.

70

201.

38

100

87.67

278.

60

45.9

0

366.

10

261.

71

482.

61

390.

32

2.3

8

1.8

2

279.

49

194.

63

200

86.21

274.

26

43.8

8

359.

20

244.

52

478.

58

388.

39

2.2

9

1.7

8

276.

31

192.

52

400

4.22 5.71 0.56 9.54 4.88 9.69 7.64

0.1

3

0.0

2

5.34 3.91 L.S.D. at 5%

A : Silky stage (after 75 days from sowing)

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B : Milky stage (after 90 days from sowing)

C : Ripe stage (after 105 days from sowing)

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Table 4. Effect of salicylic acid and thiourea on yield of maize plants at 105 days from sowing 446 (combined analysis of two seasons). 447

448

Yield of maize plants

Treatments (mg L-1) Oi

l %

Shelli

ng %

Harv

est

index

Grain

yield/f

ed.

(ton)

Grain

yield/pl

ant (g)

100

grai

ns

weig

ht

(g)

No.

grai

ns

/ro

w

No.

row

s

/ear

Ear

diame

ter

(cm)

Ear

leng

th

(cm

)

4.9

8

72.54 0.59 3.33 243.80

38.8

0

41.

99

13.

66

1.59

22.3

0

0.0

Salic

ylic

acid

5.7

4

79.36 0.70 3.92 268.36

40.7

8

42.

30

14.

36

2.62

23.6

9

10

0

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6.4

4

82.37 0.76 4.52 279.22

43.7

2

43.

81

14.

51

2.89

24.7

8

20

0

5.9

0

80.42 0.72 4.11 274.64

42.6

4

43.

62

14.

42

2.76

23.8

7

40

0

0.6

7

5.76 0.11 0.49 24.06 1.93 n.s. n.s. 1.01 0.34 L.S.D. at 5%

5.0

1

73.06 0.60 3.40 244.40

39.3

7

41.

52

13.

80

1.66

22.9

1

0.0

Thio

urea

5.8

7

80.55 0.74 4.09 270.32

41.6

0

43.

69

14.

58

2.56

23.0

9

50

0

6.0

6

83.64 0.76 4.40 276.26

43.5

6

44.

48

16.

69

2.67

24.1

6

10

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6.3

3

86.30 0.79 5.01 281.01

44.5

2

44.

76

16.

70

2.77

24.2

3

15

00

0.7

7

6.62 0.13 0.59 25.55 2.20 n.s. n.s. 0.80 0.17 L.S.D. at 5%

449

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Table 5. Effect of salicylic acid and thiourea on photosynthetic pigments contents (mg/g fresh 451 weight) in the leaves of maize plants at 75 and 90 days from sowing (combined analysis of two 452 seasons). 453

454

Milky stage (90 days after

sowing)

Silky stage (75 days after

sowing)

Treatments (mg L-1) Total

pigmen

ts

Carotenoi

ds

Chl

. b

Chl

. a

Total

pigmen

ts

Carotenoi

ds

Chl

. b

Chl

. a

2.42 0.52

0.4

1

1.4

9

2.17 0.42

0.3

6

1.3

9

0.0

Salic

ylic

acid

2.68 0.61

0.4

8

1.5

9

2.40 0.48

0.4

2

1.5

0

100

3.02 0.70 0.61.72.79 0.58 0.51.6200

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0 2 2 9

2.87 0.66

0.5

4

1.6

7

2.63 0.52

0.4

9

1.6

2

400

0.12 0.08

0.0

6

0.1

0

0.09 0.04

0.0

5

0.0

9

L.S.D. at 5%

2.44 0.50

0.4

3

1.5

1

2.18 0.43

0.3

5

1.4

0

0.0

Thio

urea

2.75 0.59

0.5

3

1.6

3

2.53 0.49

0.4

8

1.5

6

500

2.95 0.68

0.6

0

1.6

7

2.73 0.56

0.5

3

1.6

4

100

0

3.10 0.72 0.61.72.88 0.59 0.51.7150

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8 0 7 2 0

0.13 0.09

0.0

9

0.1

1

0.15 0.05

0.1

2

0.1

4

L.S.D. at 5%

455

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Table 6. Effect of interaction between salicylic acid and thiourea on photosynthetic pigments 457 contents (mg/g fresh weight) in the leaves of maize plants at 75 and 90 days from sowing 458 (combined analysis of two seasons). 459

460

Milky stage (90 days after sowing) Silky stage (75 days after sowing)

Treatments (mg

L-1)

Total

pigment

s

Carotenoid

s

Chl.

b

Chl.

a

Total

pigment

s

Carotenoid

s

Chl.

b

Chl.

a

Salicyli

c acid

Thioure

a

2.45 0.54

0.4

2

1.4

9

2.36 0.51

0.3

9

1.4

6

0.0

0.0

2.66 0.56

0.4

6

1.6

4

2.56 0.53

0.4

4

1.5

9

100

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2.91 0.64

0.5

3

1.7

4

2.81 0.59

0.5

0

1.7

2

200

2.77 0.59

0.4

9

1.6

9

2.69 0.56

0.4

7

1.6

6

400

2.58 0.56

0.4

7

1.5

5

2.48 0.53

0.4

4

1.5

1

0.0

500

2.82 0.60

0.5

1

1.7

1

2.74 0.58

0.4

9

1.6

7

100

3.04 0.67

0.5

6

1.8

1

2.96 0.63

0.5

4

1.7

9

200

2.94 0.65

0.5

3

1.7

6

2.82 0.60

0.5

2

1.7

0

400

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2.67 0.59

0.4

9

1.5

9

2.58 0.55

0.4

7

1.5

6

0.0

1000

2.96 0.66

0.5

3

1.7

7

2.82 0.59

0.5

1

1.7

2

100

3.13 0.70

0.5

7

1.8

6

3.07 0.67

0.5

6

1.8

4

200

3.04 0.68

0.5

6

1.8

0

2.94 0.64

0.5

3

1.7

7

400

2.79 0.61

0.5

1

1.6

7

2.69 0.58

0.5

0

1.6

1

0.0

1500

3.03 0.68

0.5

4

1.8

1

2.99 0.67

0.5

3

1.7

9

100

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3.24 0.73

0.6

0

1.9

1

3.17 0.70

0.5

8

1.8

9

200

3.14 0.71

0.5

7

1.8

6

3.06 0.69

0.5

5

1.8

2

400

0.05 0.01

0.0

4

0.0

4

0.06 0.02

0.0

5

0.0

5

L.S.D. at 5%

461

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Table 7. Effect of salicylic acid and thiourea on chemical constituents of maize plants at 105 days 463 from sowing (combined analysis of two seasons). 464

465

Chemical constituents of maize plants

Treatments (mg L-1)

Phenols

(mg/g)

Free amino

acids

Total soluble

sugars %

Total

carbohydra

te

Crude

protei

n %

Grain

s

Leave

s

Grain

s

Leave

s

Grain

s

Leave

s

Grains

Grain

s

4.02 3.81 20.11 19.52 28.09 32.82 75.67 7.69 0.0

Salic

ylic

acid

4.91 5.34 25.41 21.32 31.62 36.71 77.83 8.26 100

5.58 6.51 34.39 26.71 35.28 47.55 80.41 10.44 200

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3.87 6.40 29.40 24.56 33.46 39.60 79.59 9.39 400

1.01 1.26 5.21 1.44 3.40 4.02 2.01 0.51 L.S.D. at 5%

3.68 2.31 18.90 16.47 22.90 34.40 76.44 7.76 0.0

Thio

urea

4.29 2.72 22.55 17.59 25.61 38.63 78.89 8.39 500

4.30 2.88 26.67 18.36 27.52 43.27 80.01 9.64

100

0

4.36 3.51 32.46 18.93 29.34 50.61 80.39 9.89

150

0

n.s. 0.41 3.43 1.13 3.01 4.20 2.34 0.60 L.S.D. at 5%

466

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physiological effects of salicylic acid and thiourea on growth and productivity of maize plants in...

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