improving drought tolerance in corn (zea mays l.) by ... · (chattha et al., 2015) as well as...

International Journal of Environment ISSN 2077-4505

Volume : 07| Issue : 03 | July-Sept. | 2018 Page:104-123

Corresponding Author: Rania M.A. Nassar, Agricultural Botany Dept., Fac. Agric., Cairo Univ., Giza, Egypt. E-mail: [email protected]

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Improving drought tolerance in corn (Zea mays L.) by foliar application with salicylic acid

1Farouk S., Sally A. Arafa1 and Rania M.A. Nassar2

1Agricultural Botany Dept., Fac. Agric., Mansoura Univ., Egypt. 2Agricultural Botany Dept., Fac. Agric., Cairo Univ., Giza, Egypt.

Received: 20 July 2018 / Accepted: 10 Sept. 2018/ Publication date: 30 Sept. 2018 ABSTRACT

Field experiments in split plot design were done at the Experimental Farm of Agric Botany Dept., Fac. Agric., Mansoura Univ., throughout the two seasons of 2015 and 2016 to assess the impact of different irrigation intervals and salicylic acid concentrations on maize growth, yield and its quality, and on some physiological and anatomical trials.

Drought conditions significantly decreased plant growth, photosynthetic pigments, nitrogen, phosphorous, potassium, water content, relative water content, osmotic potential, yield and its quality, while the contrary was obtained in hydrogen peroxide, lipid peroxidation, and membrane permeability, proline, soluble carbohydrates, ascorbic acid, phenol, water saturated deficient and osmotic adjustment in comparison with the control.

Foliar-applied salicylic acid, specifically 100 mg/l, significantly enhanced growth, yield and improved physiological attributes in plant shoot under normal or drought conditions compared with untreated plants. Exogenous salicylic not only mitigated the repressing impact of drought stress, however conjointly had a stimulatory impact on physiological traits and yield. It's prompt that the drought severity of maize plants was declined by 100 mg/l SA application. Key words: Irrigation intervals, Maize, Salicylic, Ultrastructure

Introduction

Maize (Zea mays L.) is an extremely important cereal grown worldwide that plays a great role

in human and animal nutrition worldwide in special in temperate and subtropical regions and it comes third in world production once wheat and rice (Modhej et al., 2014). In 2014 there is 2.22 x 108 ha of harvest area and 1.25 x 109 Mg of production around the world (FAO, 2015). The requirement for maize is projected to double between now and 2050 (Rosegrant et al., 2009).

According to FAO, there is an urgent need to enhance food production by 70% by 2050 to feed this expected population from 7 to 9.2 billion (OECD, 2010). Several recent investigations have identified environmental stresses as major threats to world food security within the twenty-first century and can become even a lot of prevalent within the coming decades because of the impacts of global change (Wassmann et al., 2009).

Drought stress is a critical problem restricts crop growth and yield worldwide through its influence on anatomical, morphological and physiological processes, that's dangerous for arable field crop and subsequent for food security (Aldesuquy and Ghanem, 2015; Kareem et al., 2017). Influence of drought on crop's performance has been widely investigated (Farouk and Abdul Qados 2010; Abd El-Mageed et al., 2017; Ghassemi-Golezani et al., 2017). Numerous plant physiological and biochemical processes are influenced by the drought lead to the overproduction of reactive oxygen species (ROS) that cause a serious problem in different metabolic processes, leading to irreparable metabolic dysfunction, that affecting crops performance and development. Antioxidant defense system has been touted as helpful for inducing plant development and counteracting the injuries of environmental stresses (Farouk et al., 2013; Aldesuquy and Ghanem, 2015). On the base of cellular responses to drought, osmotic adjustment (OA) has been found to be one amongst the foremost effective physiological strategies underlying plant resistance to drought (Zhang et al., 1999). OA as a process of active accumulation of organic osmolytes in plant cells under drought, might alter stomatal and photosynthetic adjustments, leaf development (Morgan, 1994), sustain root development

Int. J. Environ., 7(3): 104-123, 2018 ISSN: 2077-4508

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(Chimenti et al., 1996), protecting macromolecules and structures, induced injuries and high photoassimilates, and yield production of crops in stressful environments (Farouk and Abdul Qados 2010; Farouk and Ramadan Amany, 2012; Kareem et al., 2017).

In Egypt, the forthcoming water shortage, though it is currently not well recognized by agro-public is a true challenge facing agricultural development and crop production in particular, where this problem arose disputes between the Nil Basin Countries to re-divide the water among them. Under such pressing threat, irrigation water should be efficiently utilized so that water saving could be used in other agricultural activity. Drought injuries events can be mitigated through the utilization of antitranspirants to limit the water loss, so rising water use efficiency, and, yield (Tambussi and Bort, 2007).

Salicylic acid (SA) as a natural growth hormone act as a potential non enzymatic antioxidant (Faheed, 2012; Aldesuquy and Ghanem, 2015), which participates in the regulation of numerous biochemical processes in plants like, stomatal closure, ion uptake, and transpiration (Khan et al., 2012), triggered chlorophyll biosynthesis and enhances photosynthesis and photosynthetic rate (Chattha et al., 2015) as well as increased total sugar (Farahat et al., 2007) total free proline (El-Khallal et al., 2009) and oil yield (Metwally et al., 2003). Also, Salicylic acid improves plant performance under normal or stressed conditions through modulation of its growth and yield of several plants, like maize (Fardus et al., 2017; Ghassemi-Golezani, et al., 2017; Kareem et al., 2017).

Therefore, this investigation was designed to assess the role of exogenous SA application in inducing maize drought tolerance, based on changes in some traits such as growth, yield, its components and some physiological and anatomical trials. Materials and Methods Experimental site

Two field experiments were done throughout the two seasons of 2015 and 2016 at the Fac. Agric. Experimental Farm, Mansoura Univ. (latitude 30.8667, and longitude 31.1667, and mean altitude 21 m above sea level) to evaluate the impact of different irrigation intervals, viz, 15 day interval (normal irrigation); 20 day interval (mild drought) and 25 day interval (severe drought), salicylic acid concentrations (SA; 0.0, 100, 200 mg/l) and its combinations on maize growth, yield, some physiological trials and mesophyll cell ultrastructure.

Experimental design and Soil properties:

A split plot technique in a randomized complete block design (R.C.B.D.), with three replicates, was followed during both years of this study. Irrigation intervals were randomly distributed within the main plots, whereas salicylic acid concentrations were randomly distributed within the sub-plots.

According to the aridity index, the experimental soil is fallen under arid condition (Ponce et al., 2000). The soil of the experimental field was clay loam. The mechanical and chemical analysis of the soil used was carried out in two growing seasons, according to Page et al., (1984) and given in Table (1).

Table 1: The physiochemical properties of the soil used during the two growing seasons

Soil properties 1st season

2nd season

Soil properties 1st season (meq/L)

2nd season (meq/L)

Clay % 42.0 41.3 Cations Calcium 1.1 1.2 Silt% 25.5 24.6 Magnesium 1.1 1.2 Fine Sand% 24.4 23.3 Sodium 2.2 2.3 Coarse Sand% 8.1 7.8 Potassium 0.3 0.2 Hygroscopic Water% 5.2 5.3 Anions Carbonate ---- ---- SSP% 58 59 Bicarbonate 1.2 1.3 EC dSm-! 0.52 0.54 Chloride 2.4 2.3 pH (1:1.5, soil: water) 7.43 7.42 Sulphate 1.1 1.3


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Planting material and crop husbandry:

Maize grains (cv. SC131) were manually planted in one row in dry soil in 25 and 20 of May during the two seasons, respectively. The distances between the hills were 25 cm and one plant/hill was left after 3 weeks from planting. All field practices were done as usually recommended for maize cultivation. The experimental field was fertilized with 10 m3 of chicken manure, phosphorous fertilizer as superphosphate at 15 kg P2O5 fed-1 as well as potassium fertilizer as potassium sulfate K2SO4 at the rate of 24 Kg K2O/feddan under maize rows through soil preparation. Nitrogen fertilizer as 120 kg N/fed as ammonium nitrate was added in two equal portions, after thinning and before the second irrigation. Plants were sprayed with SA concentration at 40 and 60 days after sowing, to run-off with a hand pressure sprayer after adding 1% (v/v) Tween 20 as a surfactant to ensure optimal permeation into maize leaves. All morphological, biochemical characters and ultrastructure changes were recorded at 90 days from sowing.

Data recorded: Vegetative characters:

Six randomly plants were used to determine the plant height, leaf number per plant, leaf area and shoot dry weight, then the data were averaged and recorded.

Photosynthetic pigments:

Photosynthetic pigments were extracted from the Ear leaf by methanol and determined spectrophotometrically as delineate by Lichtenthaler and Wellburn (1985).

NPK percentage in Ear leaf:

The ear leaves were wet digested, then determination of nitrogen, phosphorous and potassium by the micro Kjeldahl methods, ascorbic method plus ammonium molybdate, and flame photometer methods respectively (Page, 1984).

Oxidative impairment:

Hydrogen peroxide (mg/g FW); lipid peroxidation (µmoles MDA /g of fresh weight) and membrane permeability percentage were quantified following the method of Rao et al. (1997), Shao et al. (2005) and Goncalves et al. (2007) respectively.

Organic osmolytes and antioxidants:

Proline was determined by the modified ninhydrin methods of Magne and Larher (1992). Total soluble carbohydrates (mg/g dry weight) and ascorbic acid (mg/g fresh weight) were extracted and then determined by anthrone and 2,6- dichlorophenol Indophenole methods as described by Sadasivam and Manickam (1996). Total phenolic (mg gallic acid/g FW) compounds were quantified by the method of Julkenen-Titto (1985).

Water status:

Quantification of leaf water status in the Ear leaves was assessed by measuring the leaf water status, including water content (WC); relative water content (RWC), Water Saturated deficit (WSD); osmotic potential (OP), and osmotic adjustment (OA) during the crop productive phase. Ear leaf discs were weighted to get fresh weight (FW). The discs were floated in distilled water in a closed petri dish and determined the turgid weight (TW), and then the discs were placed in a pre-heated oven at 80 oC for assessing dry weight (DW). Finally, RWC, WSD, and LWC were calculated using the following equations:


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RWC (%) = (FW –DW/TW-DW) x 100 WSD (%) = 100 –RWC LWC (%) = (FW-DW) x 100/DW Osmotic potential (Ψ0) was determined using Shardakov methods, using a sucrose solution as

described by Taiz and Zeiger (2006). However, the osmotic adjustment was calculated as the difference in osmotic potential between stress and non-stress treatments (Blum, 1989).

Mesophyll ultrastructure:

Leaf segments (1-2 mm2) from the middle of healthy Ear leaves, were fixed in 5% glutaraldehyde for 24 hr. and washed twice using 0.1 M phosphate buffer (pH 7.2). The specimens were postfixed in 1% osmium tetroxide for 4 h at 4 0C. The samples were progressively dehydrated by ethanol gradient concentration to 100%, then in propylene oxide, embedded into beam capsules, filled with Durcupan resin, and they were polymerized at 60 0C. The thin sections were cut with a glass knife, mounted on copper grids (400 mishes) and stained with uranyl acetate and lead citrate and examined with a transmission electron microscope (Jeol JEM 1010) at 100 kV.

Yield and yield attributes:

Harvesting was done after 115 days from planting. Six plants from every treatment were taken randomly to estimate yield and its components, i.e. cob length, cob weight, grain weight per cob, 1000 grain weight. Additionally, the percentage of oil, carbohydrates, and protein

Grain oil, total proteins, and total carbohydrate percentage were estimated by the procedure outlined by AOAC (1990), Chapman and Pratt (1978) and Sadasivam and Manickam, (1996) respectively.

Statistical analysis:

All data were analyzed statistically using two-way ANOVA by using COSTAT software. Different letters show significant differences between treatments at P<0.05. The values are mean ± SE for three samples in each group. Results and Discussion Plant growth:

Data are given in Table (2) prove that all studies growth characters of maize were significantly declined with drought stress. The greatest reduction was obtained under severe drought stress, in both seasons.

Application of SA concentration, in special, 100 mg/l significantly accelerates maize plant growth regarding untreated control plants. Moreover, foliar spraying of SA mitigated the injuries of drought as compared with untreated control plants under such drought level.

A decline in plant growth under drought have previously been reported (Farouk and Abdul Qados 2010; Kareem et al., 2017), this reduction might be due to, the blocking of the vascular tissues, that obstructive translocation of water, minerals and assimilates from leaves to developed grains (Taiz and Zeigerr, 2006); and/or 2- a marked suppression of plant photosynthetic efficiency by closing stomata, inhibited ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and the impairment of ATP synthesis needed for plant growth (Lawlor and Cornic, 2002). Moreover, drought reduced cell division and elongation that ultimately reduces the plant growth, by dropping in leaf water status, assimilation of water and nitrogenous compounds and/or reduce the activity of cyclin-dependent kinases (CDKs) activities (Hussain et al., 2008; Farouk and Abdul Qados, 2010). Finally, drought reduced the uptake of essential elements and photosynthetic capacity likewise the excess accumulation of ROS, that induced oxidative injuries to deoxyribonucleic acid, lipid, and protein and finally a growth reduction (Yazdanpanah et al., 2011).


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Table 2: Plant growth parameter of maize plants as affected by drought with or without salicylic acid in the two seasons

Treatments Plant height Leaf number Leaf area Shoot DW

1st Season 2nd Season 1st Season 2nd Season 1st Season 2nd Season 1st Season 2nd Season

Irrigation intervals (days)

15 (N) 258±2.01a 257±4.82a 14.8±0.26a 15.1±0.35a 697±7.20a 688±10.21a 259±13.87a 256±13.14a

20(DI1) 237±5.20b 235±3.02b 11.8±0.48b 11.6±0.52b 613±9.03b 598±16.49b 194±13.96b 188±13.64b

25(DI2) 192±9.19c 187±13.53c 10.6±0.62c 10.6±0.60c 558±29.2c 544±32.45c 155±8.85c 152±9.78c

Salicylic acid

Water (W) 210±15.08b 217±13.90b 11.1±0.85b 11.0±0.97b 570±35.16b 542±38.39b 162±13.59c 157±14.25c

100 mg/l (SA1) 243±6.65a 241±7.12a 13.4±0.64a 13.5±0.58a 655±17.16a 653±15.07a 241±19.38a 234±17.70a

200 mg/l (SA2) 226±13.83ab 229±10.82ab 12.8±0.58a 12.8±0.63a 643±12.20a 635±13.23a 204±14.29b 205±16.29b

Interaction

N W 253±1.27ab 248±8.10ab 14.3±0.33ab 14.6±0.66ab 685±8.34ab 672±28.58ab 211±5.78c 208±6.80d

N SA1 261±5.27a 262±9.32a 15.3±0.33a 15.6±0.66a 716±15.75a 710±5.33a 306±3.10a 292±5.12a

N SA2 259±1.46a 259±8.41ab 15.0±0.57ab 15.0±0.57a 690±4.74a 683±3.99a 260±2.43b 268±9.64b

DI1 W 229±16.06bc 229±2.45ab 10.3±0.33d 10.0±0.01c 581±10.79c 538±19.99d 156±8.16e 150±10.05f

DI1 SA1 244±0.65abc 246±1.00ab 13.3±0.33bc 13.0±0.01b 631±2.09b 632±5.38bc 244±14.04b 236±12.53c

DI1 SA2 237±2.67abc 230±3.46ab 12±0.57cd 12.0±1.0b 627±9.31b 623±13.34c 183±7.81d 177±7.90e

DI2 W 168±11.21d 153±10.54d 8.6±0.33e 8.3±0.33d 444±5.73d 415±5.75e 119±1.09f 113±3.51g

DI2 SA1 217±9.46c 221±3.06bc 11.6±1.20cd 12.0±0.01b 618±20.99b 616±11.82c 175±1.20de 173±1.00ef

DI2 SA2 191±13.60d 188±3.03cd 11.6±0.33cd 11.6±0.33b 613±2.76bc 599±7.42c 170±0.28de 169±0.61ef


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Foliar spraying of SA under normal or drought condition enhanced plant growth and productivity. These results were supported by many investigators like Chattha et al. (2015); Fardus et al. (2017) and Kareem et al. (2017). The induction impact of SA application induced plant growth under normal or drought condition might have been due to SA-induced physiological processes, like; accelerated carbon assimilates, increased the biosynthesis of metabolites and maintenance of tissue water status (Habibi, 2012). SA improved mitosis and cell elongation within the apical meristems (Sakhabutdinova et al., 2003) as well as maintained RWC and photosynthetic (Mathur and Vyas, 2007). This conclusion was confirmed by our results that indicate that the SA application declined leaf water osmotic potential which resulted in increasing water uptake and leaf RWC that induced cell division and elongation. Additionally, SA application enhanced total soluble sugar accumulation that served as a substrate for accelerating initiation of leaf primordial and declined plastochron duration (Munns et al., 1979). Finally, SA strengthened antioxidant defense systems needed for mitigated the oxidative injuries (Aldesuquy and Ghanem, 2015).

Photosynthetic pigments and ion percentage:

Chlorophylls concentration and ions percentage (NPK) in maize Ear leaf in each experimental season significantly increased by imposing drought stress (Table, 3). The lowest values were obtained under severe drought stress as compared with normal irrigation treatment. Meanwhile, the data in the same table indicated that foliar spraying with SA at both concentrations accelerated the chlorophylls and ion accumulation. The most effective in this concern in most cases was 100 mg/l SA as compared with untreated plants.

Regarding the interaction, it was noticed that application of SA, in special, 100 mg/l induce the accumulation of chlorophylls and ions comparing with untreated plants under such drought stress. Under severe drought application of SA counteracted the harmful effects of drought on chlorophyll concentration and ion percentages.

The declined in photosynthetic pigments under drought is so an unremarkably ascribed phenomenon. Decline in photosynthetic pigments under drought might be related to decreased the biosynthesis of the main chlorophyll pigment complexes encoded by the cab gene family (Allakhverdiev et al., 2003), and/or to the destruction of chiral macro-aggregates of the light-harvesting chlorophyll ‘a’ or ‘b’ pigment-protein complexes that defend the chloroplasts (Lai et al. , 2007).

Salicylic acid-treated plants exhibited higher values of photosynthetic pigment than those of control or drought-stressed plants (Fardus et al., 2017). The stimulatory effect of SA acid on photosynthetic pigment concentration might be due to its role in increment triggered photosynthetic biosynthesis (Farahat et al., 2007); and conjointly due to the phenomenon of antioxidant, scavenging to provide protection to chloroplast and chlorophyll against degradation (Aldesuquy and Ghanem, 2015). Finally by increasing nitrogen percentage in shoots, that improved chlorophyll biosynthesis by encouraging pyridoxal enzyme formation, that plays a vital role in α-amino levulinic acid synthetase as a primary compound in chlorophyll synthesis (Ramadan et al., 2003).

Drought influences the availability of ions within the soil by its roles on the solubility and precipitation of ions and alters biochemical processes in the plant (Singh and Usha, 2003). Nutrient uptake by plants is mostly declined under drought conditions attributable to a considerable decline in transpiration rates coupled with impaired membrane permeability leading to reduced root-absorbing power (Levitt, 1980). SA can significantly modulate the uptake of essential ions, thereby, improve ion contents under normal or drought condition (Nazar et al., 2015). Organic osmolytes and oxidative impairment

Significant differences were observed among drought stress for organic osmolytes and oxidative impairment. Data are given in Table (4) assessed that maize plants under drought stress by inducing the hyper-accumulation of proline (Pro), soluble carbohydrates (Scar), ascorbic acid (AsA) and phenol (Phe) as compared with normal condition. That additional enhanced with the application of salicylic acid (SA) under normal or drought conditions so increased drought tolerance. The maximum concentration of organic osmolytes was noted by the application of 100 mg/l SA combined


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Table 3: Photosynthetic pigment concentration and ion percentage in the Ear leaf of maize plants as affected by drought with or without salicylic acid in the two seasons

Treatments Chlorophyll A Chlorophyll B Total chlorophyll N P K

1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season Irrigation intervals (days)

15 (N) 1.944± 0.09a

1.554± 0.23ab

0.811± 0.05a

1.179± 0.19a

2.755± 0.12a

2.734± 0.10a

2.15± 0.03a

2.13± 0.04a

0.570± 0.01a

0.559± 0.01a

2.73± 0.05a

2.67± 0.05a

20(DI1) 1.759± 0.07ab

1.876± 0.13a

0.737± 0.08ab

0.610± 0.06b

2.496± 0.06b

2.487± 0.16ab

2.01± 0.03b

1.95± 0.02b

0.530± 0.01b

0.525± 0.01a

2.44± 0.06b

2.50± 0.07b

25(DI2) 1.682± 0.14b

1.357± 0.14b

0.741± 0.07ab

0.514± 0.08b

2.342± 0.15b

1.871± 0.190b

1.52± 0.10c

1.47± 0.10c

0.423± 0.02c

0.415± 0.02b

2.17± 0.08c

2.12± 0.06c

Salicylic acid

Water (W) 1.886± 0.06b

1.192± 0.19b

0.667± 0.05b

0.830± 0.23a

2.471± 0.04ab

2.023± 0.26b

1.71± 0.12c

1.70± 0.13b

0.466± 0.03c

0.462± 0.03b

2.27± 0.10b

2.29± 0.09b

100 mg/l (SA1) 1.733± 0.13a

1.952± 0.10a

0.930± 0.06a

0.648± 0.06a

2.663± 0.13a

2.600± 0.12a

2.06± 0.08a

2.01± 0.09a

0.537± 0.01a

0.530± 0.02a

2.61± 0.08a

2.58± 0.07a

200 mg/l (SA2) 1.766± 0.13a

1.643± 0.14a

0.692± 0.05b

0.825± 0.14a

2.459± 0.17ab

2.468± 0.24a

1.91± 0.10b

1.84± 0.10b

0.520± 0.01b

0.507± 0.02a

2.47± 0.10a

2.44± 0.11ab

Interaction

N W 1.758± 0.09ab

1.070±0.39bc 0.766± 0.11abc

1.448± 0.54a

2.525± 0.05ab

2.519± 0.16ab

2.00± 0.03bcd

2.05± 0.04abc

0.543± 0.01cd

0.543± 0.00a

2.58± 0.07ab

2.49± 0.08abc

N SA1 2.161± 0.18a

2.116± 0.11a

0.901± 0.11ab

0.883± 0.02abc

3.063± 0.29a

3.000± 0.12a

2.26± 0.01a

2.24± 0.01a

0.589± 0.01a

0.572± 0.01a

2.87± 0.05a

2.78± 0.03a

N SA2 1.911± 0.13ab

1.477± 0.44abc

0.766± 0.04abc

1.205± 0.28ab

2.667± 0.17ab

2.683± 0.16ab

2.19± 0.01ab

2.10± 0.09ab

0.577± 0.01ab

0.561± 0.02a

2.76± 0.02a

2.76± 0.02a

DI1 W 1.892± 0.13ab

1.683± 0.34ab

0.528± 0.02c

0.714± 0.15bc

2.420± 0.11ab

2.397± 0.50ab

1.89± 0.02cd

1.86± 0.01bc

0.510± 0.01e

0.502± 0.01ab

2.31± 0.07bc

2.38± 0.17bc

DI1 SA1 1.600± 0.12ab

2.160± 0.06a

0.976± 0.15a

0.428± 0.02c

2.577± 0.03ab

2.588± 0.08ab

2.13± 0.02ab

2.03± 0.02abc

0.557± 0.01bc

0.557± 0.01a

2.62± 0.05ab

2.64± 0.03ab

DI1 SA2 1.784± 0.10ab

1.785± 0.15ab

0.707± 0.05abc

0.689± 0.051bc

2.491± 0.15ab

2.475± 0.21ab

2.01± 0.01bc

1.96± 0.02abc

0.524± 0.01de

0.516± 0.01ab

2.40± 0.11bc

2.49± 0.09abc

DI2 W 2.000± 0.11ab

0.823± 0.07c

0.705± 0.08abc

0.330± 0.04d

2.468± 0.04ab

1.153± 0.11c

1.23± 0.01f

1.19± 0.04e

0.345± 0.01g

0.342± 0.04c

1.93± 0.05d

2.00± 0.05e

DI2 SA1 1.437± 0.12b

1.580± 0.10abc

0.912± 0.13ab

0.632± 0.02bc

2.349± 0.05ab

2.213± 0.11b

1.78± 0.13d

1.76± 0.22c

0.466± 0.01f

0.460± 0.03b

2.33± 0.04bc

2.31± 0.06cd

DI2 SA2 1.602± 0.38ab

1.667± 0.08ab

0.605± 0.137bc

0.580± 0.22bc

2.207± 0.52b

2.248± 0.14b

1.54± 0.16e

1.48± 0.09d

0.458± 0.01f

0.445± 0.02b

2.24± 0.21c

2.06± 0.13de


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with severe drought stress in comparison with drought or SA application alone. Regarding oxidative stress criteria, the data in Table (4) assessed that hydrogen peroxide

(H2O2), lipid peroxidation (MDA), and membrane permeability percentage (MP %) significantly increased under drought stress, but significantly reduced by foliar application of SA. Conjointly the data in the same table assessed that under drought stress application of SA counteract the injuries effect of drought on oxidative impairment criteria that reduced its concentration as compared with untreated plants under such drought stress level.

Carotenoid concentration was significantly declined with drought and increased by SA foliar application in special at 100 mg/l. Additionally; the application of SA under drought stress alleviated the injuries of drought on carotenoid by increasing its concentration as compared with untreated plants under moderate and severe drought stress.

As the drought prevails stomata closure progressively as a result of which photosynthesis and water use efficiency terminated to decline. Chloroplasts produce a high amount of reactive oxygen species (ROS), under stress condition (Asada, 2000). Stomatal closure causing a decline in leaf CO2 concentration that might, in turn, resulted in a decline in the concentration of NADP+ available to accept electrons from PSI and/or PSII and so generation of ROS, like H2O2. On the contrary, SA-supplemented drought-stressed showed enhanced activity CAT, SOD, POD than those under drought treatment without SA, which suggests an unambiguous role of SA in scavenging H2O2 under drought (Li et al., 2014; Rohman et al., 2015).

The cell membrane is that the primary sites of impact to cells to different stress conditions (Aldesuquy and Ghanem, 2015). In this regard, lipid peroxidation and membrane permeability could consider as widely used stress indications of plant membranes. In the present investigation, drought-induced MDA accumulation and MP% of maize plants. These results are in accordance with those obtained by Farouk et al. (2013) and Aldesuquy and Ghanem (2015). ROS can react with unsaturated fatty acids to cause lipid peroxidation of essential membrane lipids resulting in leakage of cellular contents, and cell death (Sridharan et al., 2009). Under drought, electrolyte leakage might be attributed to the injuries of cell membranes, that becomes more permeable due to less water availability (Almeselmani et al., 2012). Masoumi et al. (2010) and Rahbarian et al. (2010) found that MP increased by drought in maize cultivar. There were many reports about the impact of SA in counteracting the oxidative injuries (Aldesuquy and Ghanem, 2015). Studies showed that SA prevented the damages to the unsaturated fatty acids, while the penetration of the membrane reduced the protection of the thylakoid membrane under stress condition (Borsani et al., 2001), resulted in decreasing in lipid peroxidation and membrane permeability of maize as compared with normal plants (Li et al., 2014; Aldesuquy and Ghanem, 2015; Fardus et al., 2017). Higher accumulation of H2O2 causes oxidative stress in plants. In this study, with the increase in drought severity, H2O2 increased. Foliar spraying with SA reduced H2O2 significantly under drought stress condition. Exogenous SA treated plant have decreased the amount of H2O2 were observed by the other researchers (Erdal et al., 2011; Hasanuzzaman et al., 2014).

It is well known from this investigation that the organic osmolytes were increased in under drought and/or SA treatments, whenever their interactions had an additive impact. Proline “Pro” has multiple functions, like osmotic adjustment, stabilization of enzymes/ proteins, maintain acceptable NADP+/NADPH ratios and detoxifies excess ROS (Iqbal et al., 2014), thereby inducing stress tolerance (Jain et al., 2001).

Enhancement in the accumulation of proline in drought and/or SA treated plants might have resulted from an increased biosynthesizing gene expression. Proline accumulation under the experimental condition results from changes in the activities of proline synthesizing and degrading enzymes (Misra and Saxena, 2009) and the up- and down-regulation of genes responsible for proline biosynthesis (Ahmad et al., 2016). Recently, proline metabolism under SA application is less known and need more studies. The increment in proline under SA may be due to rising nitrogen in the plant that is taken into account the main constituent of proline (El-Tayeb, 2005).

Soluble carbohydrates contributed the foremost to the leaf osmotic potential, and that they furthermore appeared to be necessary within the leaf osmotic adjustment under drought. The rising in soluble carbohydrates under drought or SA application might successively play a vital role in inducing the cytoplasm osmotic pressure. The present hypothesis is that soluble carbohydrates act as osmotica and/or protect specific macromolecules and assist in the stabilization of membrane structure.


112

Table 4: Oxidative impairment, organic osmolytes and antioxidant compounds in the Ear leaf of maize plants as affected by drought with or without salicylic acid in the two seasons

Treatments H2O2 MDA MP Proline

Soluble carbohydrates

Ascorbic Phenol Carotenoids

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season


15 (N) 24.92± 0.32b

25.22± 0.31c

6.23± 0.60c

5.44± 0.66c

57.34± 1.26b

57.32± 1.07

2.68± 0.24c

2.89± 0.18c

29.62± 1.48c

28.480± 1.07c

0.320± 0.01c

0.307± 0.01c

11.09± 0.69c

11.613± 0.34c

0.248± 0.01a

0.277± 0.01a

20(DI1) 29.04± 1.77ab

27.94± 0.55b

9.43± 0.74b

8.79± 0.46b

67.41± 2.42a

66.31± 2.41b

3.87± 0.30b

3.78± 0.16b

36.86± 0.88b

35.48± 0.83b

0.373± 0.01b

0.360± 0.00b

15.14± 1.61b

14.350± 0.72b

0.221± 0.00ab

0.246± 0.01ab

25(DI2) 32.89± 3.07a

31.36± 1.53a

12.26± 1.53a

11.48± 1.25a

71.74± 2.76a

71.24± 1.82a

4.35± 0.31a

4.37± 0.18a

65.43± 3.78a

62.34± 3.89a

0.455± 0.02a

0.498± 0.01a

18.92± 1.61a

16.982± 1.21a

0.181± 0.01b

0.168± 0.01b

Salicylic acid

Water (W) 33.09± 3.06a

30.79± 1.75a

12.12± 1.62a

10.91± 1.19a

71.08± 2.84a

70.56± 2.92a

3.21± 0.35b

3.33± 0.27b

38.66± 5.07c

38.26± 4.72bc

0.357± 0.02ab

0.361± 0.02b

11.62± 0.73b

11.77± 0.38b

0.214± 0.01ab

0.204± 0.02b

100 mg/l (SA1) 26.34± 0.72b

26.54± 0.57b

7.42± 0.99b

6.72± 0.98b

60.35± 2.83b

61.16± 1.90b

3.96± 0.38a

4.02± 0.22a

49.35± 6.74a

47.09± 6.49a

0.407± 0.02a

0.420± 0.03a

15.55± 1.66a

15.33± 1.05a

0.228± 0.01a

0.250± 0.01a

200 mg/l (SA2) 27.41± 1.85b

27.20± 0.62b

8.38± 0.61b

8.09± 0.98b

65.05± 2.33b

63.14± 2.10b

3.74± 0.35a

3.69± 0.27ab

43.89± 5.33b

40.95± 5.21b

0.384± 0.02a

0.384± 0.02b

17.98± 1.90a

15.83± 1.19a

0.207± 0.01ab

0.237± 0.01a

Interaction

N W 25.50± 0.57b

25.65± 0.47de

7.50± 0.19bcd

7.09± 0.29bc

60.83± 0.29cde

59.18± 1.76ef

1.81± 0.06b

2.42± 0.46e

24.48± 1.46d

26.54± 1.00c

0.284± 0.01c

0.286± 0.03d

8.80± 0.50d

10.77± 0.89c

0.228± 0.02ab

0.258± 0.01ab

N SA1 23.95± 0.14b

24.50± 0.30e

4.40± 0.58d

3.24± 1.10d

52.78± 1.04e

55.85± 2.37f

3.24± 0.32ab

3.31± 0.07cde

33.47± 0.87cd

31.14± 2.54c

0.346± 0.01bc

0.336± 0.01cd

11.78± 0.41cd

11.83± 0.21c

0.266± 0.02a

0.283± 0.04a

N SA2 25.31± 0.41b

25.51± 0.68de

7.9± 1.15cd

6.00± 0.21cd

58.40± 0.95de

56.92± 1.45ef

3.00± 0.04ab

2.95± 0.05de

30.91± 1.39cd

27.75± 0.82c

0.328± 0.01bc

0.298± 0.01d

12.70± 1.07cd

12.23± 0.16c

0.250± 0.02a

0.288± 0.00a

DI1 W 32.83± 5.12ab

29.81± 0.81b

11.60± 1.62b

10.55± 0.20b

75.18± 3.11ab

75.19± 0.24ab

3.37± 0.15a

3.53± 0.16bcd

34.53± 1.75c

33.80± 1.19bc

0.365± 0.02bc

0.342± 0.01cd

12.54± 0.02cd

11.98± 0.31c

0.209± 0.01abc

0.231± 0.04ab

DI1 SA1 26.98± 0.08b

26.80± 0.28cde

8.18± 0.52bcd

7.50± 0.07bc

61.21± 0.17cde

61.10± 1.29def

3.98± 0.43a

3.98± 0.16abc

38.53± 1.16c

37.51± 0.81bc

0.392± 0.02ab

0.370± 0.02c

15.66± 4.23bc

15.77± 1.21b

0.241± 0.02ab

0.271± 0.01a

DI1 SA2 27.30± 0.79b

27.21± 0.54bcde

8.50± 0.48bcd

8.33± 0.13bc

65.83± 3.20bcd

62.63± 2.89de

3.88± 0.94a

3.82± 0.48abcd

37.51± 0.78c

35.14± 1.64bc

0.362± 0.01bc

0.367± 0.01c

17.21± 2.76bc

15.28± 0.66b

0.213± 0.00abc

0.237± 0.01ab

DI2 W 40.93± 5.18a

36.90± 1.93a

17.26± 2.23a

15.10± 0.95a

77.23± 2.74a

77.32± 0.90a

4.07± 0.04a

4.04± 0.08abc

56.98± 5.15b

54.44± 7.48ab

0.422± 0.02ab

0.456± 0.03b

13.53± 0.25bcd

12.57± 0.20c

0.206± 0.01abc

0.124± 0.01c

DI2 SA1 28.11± 1.29b

28.31± 0.35bcd

9.67± 1.99bc

9.42± 0.65bc

67.07±6.60bcd 66.53± 2.80cd

4.65± 0.99a

4.78± 0.22a

76.06± 1.75a

72.63± 0.35a

0.482± 0.04a

0.554± 0.01a

19.21± 1.11ab

18.40± 0.98a

0.178± 0.01bc

0.194± 0.02b

DI2 SA2 29.63± 6.00b

28.86± 1.08bc

9.85± 0.79bc

9.93± 2.75b

70.93±3.79abc 69.87± 0.81bc

4.34± 0.35a

4.30± 0.44ab

63.26± 6.87b

59.96± 6.22ab

0.462± 0.054a

0.485± 0.01b

24.03± 1.55a

19.97± 1.23a

0.158± 0.01c

0.185± 0.09bc


113

The accumulation of soluble carbohydrates was attributed to the increased carbon use efficiency coupled with a reduction in cellular metabolism (Schnapp et al., 1990).

Fortunately, plants have developed numerous protecting strategies to eliminate ROS, that are effective at different levels of stress-induced deterioration. The antioxidant defense strategy, including both enzymatic and non-enzymatic that work joined to manage the cascades of uncontrolled oxidation and protect the cells from oxidative damage (Gill and Tuteja, 2010). However, supplementation with SA under stress showed a significant increase of both AsA which indicated a clear role of SA in producing nonenzymatic antioxidant. SA might take part in the regeneration of AsA by up-regulating the related enzymes, i.e. MDHAR and DHAR (Fardus et al., 2017). Accordingly, drought and/or SA caused marked an increment in the total amount of phenolic substances (Farouk et al., 2013; Aldesuquy and Ghanem, 2015), that might participate in ROS scavenging in order to counteract stress-associated oxidative stress (Sgherri et al., 2003). Carotenoids, that are essential components of the chloroplasts of plants serve as accessory light-harvesting pigments and play a vital role in protecting the chloroplasts against the destructive impact of excess light and act as quenchers to prevent the formation and damaging effect of singlet oxygen (Sies and Stahl, 1995). Aldesuquy and Ghanem (2015) found that the SA application increased carotenoid concentration in plant tissues.

Leaf water relations parameters:

Progressively increasing drought significantly affected all water relations parameters (Table 5). Osmotic potential, (Ψs), declined (became more negative) progressively with prolonged irrigation intervals, therefore, the values were the lowest at high drought level. Likewise, water content (WC); relative water content, (RWC), and water saturated deficiency (WSD) declined with increasing drought stress. The decline was more pronounced in severe drought. Osmotic adjustment (OA) capacity of maize Ear leaf increased significantly with increasing drought stress regardless of stress levels. SA foliar spray increased (less negative values), OP, WC, and RWC in maize ear leaf as compared with unsprayed plants meanwhile declined WSD in maize leaf. OA significantly enhanced in corn leaf with the SA application due to maintaining the turgor potential of the leaf. As considered in the interaction between SA and drought, the date in Table (5) verified that the SA application under normal or drought condition improved leaf water status. It is noted that application of SA increased significantly WC and RWC under control, and then declined under high drought level. Alternatively, SA foliar spray nullifies the injuries impact of drought on water content.

Maize treated with SA has some tolerance-avoiding strategies, like OA and a decline in leaf osmotic potential, to sustain their water status at values just like those of the control plant (Table 5). OA could be a strategy used for sustaining turgor and reducing the harmful impacts of drought on plant tissue (Rhodes and Hanson, 1993). Generally, OA involves the net accumulation of organic or inorganic osmolytes; total soluble sugars, proline (Munns, 2005; Farouk and Abdul Qados 2010; Farouk, 2011) in a cell in response to drought. Consequently, the cell osmotic potential declines, that successively attracts water into the cell and enable turgor to be maintained (Blum et al., 1996).

Upon exposure to drought stress, numerous plants accumulate compatible solutes that are non-toxic at high concentrations (Chen and Murata, 2008). It is usually proved that the rise in cellular osmolarity that outcomes from the build-up osmolytes are accompanied by the influx of water into, or at least a reduced efflux from, cells, so maintaining the turgor essential for cell enlargement. Although the accumulation of solutes enhanced in each non-stressed and stressed plants due to foliar-applied SA, the leaf osmotic potential was not substantially finding, it is plausible to propose that changes in organic solute accumulation, caused a slight change in leaf osmotic potential which resulted in improved leaf turgor potential and therefore assist in osmoregulatory processes. In the present investigation, foliar application of SA considerably declined leaf osmotic potential in the stressed plants because of its role in increasing compatible organic solutes. The lower osmotic potential under drought or the SA application may occur for various potential reasons: lower water content, that might cause greater osmolytes concentration, greater tissue elasticity, and/or active accumulation of solutes. (Atteya 2003)

Drought stress decreases RWC, LWCA, and LWC. These findings are in line with those of Farouk and Abdul Qados (2010). The high amount of water status parameters was shown in control, SA foliar application. Our findings are in good accordance with Alam et al. (2013). The results of an


114

Table 5: Ear leaf water status of maize plants as affected by drought with or without salicylic acid in the two seasons

Treatments Water content% RWC% WSD OP OA 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season 1st

Season 2nd

Season Irrigation intervals (days)

15 (N) 95.09± 0.52a

93.98± 0.49a

85.65± 3.59a

80.84± 3.16a

14.34± 3.59c

19.15± 3.16c

-0.359± 0.03c

-0.344± 0.02c

0.095± 0.03c

0.079± 0.02c

20(DI1) 93.39± 0.68b

89.50± 1.63b

72.32± 3.75b

69.75± 3.03b

27.67± 3.75b

30.24± 3.03b

-0.425± 0.02b

-0.396± 0.02b

0.160± 0.02b

0.131± 0.02b

25(DI2) 88.07± 1.20c

91.74± 0.62c

59.20± 4.36c

61.38± 4.73c

40.79± 4.36a

38.61± 4.73a

-0.554± 0.03a

-0.505± 0.03a

0.290± 0.03a

0.240± 0.03a

Salicylic acid

Water (W) 92.83± 0.18a

89.99± 1.43c

60.23± 5.27c

57.69± 4.06b

39.76± 5.27a

42.30± 4.06a

-0.355± 0.02c

-0.329± 0.01c

0.091± 0.02c

0.064± 0.01c

100 mg/l (SA1) 92.09± 1.61a

93.65± 0.43a

83.58± 4.03a

79.05± 2.42a

16.41± 4.03c

20.94± 2.42b

-0.550± 0.02a

-0.510± 0.02a

0.285± 0.02a

0.245± 0.02a

200 mg/l (SA2) 91.62± 1.67a

91.58± 1.22b

73.36± 3.38b

75.23± 3.25a

26.63± 2.02b

24.76± 3.25b

-0.433± 0.03b

-0.406± 0.02b

0.169± 0.03b

0.141± 0.02b

Interaction

N W 93.09± 0.12bc

92.86± 0.13b

77.38± 5.39bc

70.41± 0.79bc

22.61± 5.39cd

29.58± 0.70cd

-0.264± 0.01h

-0.264± 0.01f

.000± 0.00h

0.000± 0.00g

N SA1 96.41± 0.32a

93.21± 0.26b

93.91± 7.36a

86.11± 2.09a

6.08± 7.36e

13.88± 2.09e

-0.475± 0.02d

-0.443± 0.02c

0.211± 0.01d

0.178± 0.01d

N SA2 95.77± 0.17ab

95.88± 0.35a

85.65± 1.84ab

86.00± 5.83a

14.34± 1.84de

13.99± 5.83e

-0.339± 0.01g

-0.324± 0.01e

0.075± 0.01g

0.059± 0.01f

DI1 W 93.01± 0.46bc

84.30± 0.25d

60.77± 0.61d

59.77± 1.08d

39.22± 0.61b

40.22± 1.08b

-0.370± 0.01fg

-0.332± 0.01e

0.106± 0.01fg

0.067± 0.01f

DI1 SA1 93.07± 2.21bc

95.04± 0.65ab

85.61± 2.14ab

78.62± 4.32ab

14.38±2. 14de

21.37± 4.32de

-0.515± 0.00c

-0.482± 0.01b

0.250± 0.01c

0.217± 0.01c

DI1 SA2 94.08± 0.41abc

89.16± 1.68c

70.59± 2.83cd

70.86± 0.76bc

29.40± 2.83bc

29.13± 0.76cd

-0.389± 0.01f

-0.374± 0.01d

0.125± 0.01f

0.109± 0.01e

DI2 W 92.39± 0.13c

92.81± 0.61b

42.54± 0.37e

42.88± 2.02e

57.45± 0.37a

57.11± 2.02a

-0.430± 0.01e

-0.391± 0.01d

0.166± 0.01e

0.126± 0.01e

DI2 SA1 86.80± 1.61d

92.70± 0.47b

71.23± 2.28cd

72.43± 0.84bc

28.76± 2.28bc

27.56± 0.84cd

-0.659± 0.01a

-0.605± 0.01a

0.395± 0.01a

0.340± 0.01a

DI2 SA2 85.01± 0.01d

89.71± 1.01c

63.83± 1.24d

68.84± 2.19c

36.16± 1.24b

31.15± 2.19c

-0.572± 0.01b

-0.520± 0.01b

0.308± 0.01b

0.255± 0.01b


115

experiment by Fardus et al. (2017) that indicate the exogenous application of 300 µM SA was found to increase the RWC. Leaf ultrastructure

Figure (1) clearly indicates that maize cell under a normal condition having a typical chloroplast, nucleus, and mitochondrion (Fig 1A). Chloroplasts exhibited a typical structure with well-developed granum and stromal thylakoids, with a tiny osmophilic plastoglobule (Fig. 1I). Typical mitochondria (Fig 1M) and a clear nucleus with nucleolus (Fig 1E). Drought stress distorted cell organelles as indicated in Figure (1 B, F, J, N). The chloroplast and thylakoids were swollen and the granum stacky disintegration accompanied with increasing the size of plastoglobules. The chloroplast membrane was dissolved (Fig 1J). The nucleus changed to crescent in shape (Fig 1F). Moreover, the mitochondria size and the number were reduced markedly (Fig. 1N).

Fig. 1: Ultrastructural changes of maize mesophyll tissue under normal (A, E, I, M), SA treatment (C, G, K, O); drought (B, F, J, N) and SA under drought (D, H, L, P).

Chl, chloroplasts, GL grana lamella; Mi Mitochondria, N Nucleous, NU Necululus, Pg Plastoglobulies


116

Foliar application of SA under normal condition did not significant changes the ultrastructure of cell organelles, except the increasing in chloroplast size (Fig 1K) as well as the size and the shape of both nucleous (Fig. 1G) and mitochondria (Fig 1O). meanwhile, application of SA under severe drought stress reversed the ultrastructural alterations of cell organelles (Fig 1 D, H, L, P) compared to normal and drought- stressed plants. The shape of chloroplast changes slightly from elongated oval to almost oval, well aligned internal lamellar system and fewer plastoglobules (Fig. 1 L).

Ultra-structural alterations under drought may be a useful tool for unveiling the fundamental strategies involved in conferring stress tolerance (Atkin and Macherel, 2009). Under control conditions, chloroplasts generally had normal rectangular shapes and typical membrane system. However, drought caused the most important alterations (Yusuf et al., 2008; Zhang et al., 2015). The distortions of grana stacking and swelling of thylakoids caused by drought within this study probably attributable to a change in the ionic composition of the stroma.

The increment in the plastoglobule size under drought, provide in this investigation is also a formal indicator of environmental stress effects. (Austin et al., 2006). The raising plastoglobule size ascertained within the drought-stressed plants is may be one of all the adaptive strategies that will prevent or mitigate the oxidative injuries mediated under drought. Alternatively, SA nullifies this ultrastructural injury by protecting the photosynthetic membrane system from oxidative stress. Chloroplasts and thylakoids in maize by the SA application were maintaining their typical shapes like those of control. Large chloroplasts with no swelling, and only minor dilations of the thylakoids in SA and drought-treated plants are the concrete indication of less oxidative stress.

Under control conditions, the mitochondria had well-organized cristae and an intact structure. Additionally, drought-affected plant cells had a tiny and the lowest number of mitochondria. However, SA treatment enhanced the size and number of mitochondria under control or stressed conditions to meet the needs of desired ATP under droughts (Silva et al., 2010), and additionally these organelles responses to stress by synthesis of many specific mitochondrial stress proteins (Rizhsky et al., 2004). Yield and yield attributes:

Data observed in Table (6) clearly show that all yield and its quality represented as cob length, cob weight, and grain weight per cob, 1000 grain weight, oil, carbohydrates and protein percentage, significantly declined by increasing irrigation intervals. The greatest reduction was observed at severe drought (irrigation every 25 days).

Application of SA in special 100 mg/l significantly increased all yield and yield quality comparing with untreated control plants. Foliar application of 100 mg/l SA under drought stress alleviated the injuries impact of drought by improving yield and quality characters as compared with untreated plants under such drought level (Table, 6)

In general, drought depressed the maize yield by 10-76%, betting on the severity and stage of occurrence (Bolaòos et al., 1993). Similar results were obtained by Farouk and Abdul Qados 2010; Sharafizad et al., 2013). The deleterious effect of drought on yield and its components may be due to: 1- Drought declined water potential of leaves, resulting in stomata closure, reduction in

photosynthetic rate, and reduced radiation interception that ultimately decreased plant biomass and photoassimilates translocation towards the developing grain, and finally yield reduction (Ghassemi-Golezani et al., 2016)

2- Accerelated flower and fruit abortion (Liu et al., 2003). Recent studies support this hypothesis, that low water potential disrupted carbohydrate metabolism in ovaries by reducing the activity of invertase (Anderson et al., 2002). Also, drought-induced swollen pollen and filament development, resulted in reductions in grain yield (Song et al., 1998).

3- Recently, the OA has received increasing interest throughout later years (Moustafa et al., 1996). That is, genotypes that adjusted osmotically, may sustain high photosynthetic rate because of a lot of favorable leaf water status that may, in turn, cause higher crop growth rate and dry matter production, finally, a higher productivity. Thus, it might be inferred that maintenance of higher RWC at a high drought level during this study (Table 2) may sustain growth and metabolic activities in plants (Subbarao et al., 2000). Additionally, SA treated plants may, presumably, translocate the pre-anthesis carbohydrate reserves to developing pods more effectively than


117

Table 6: Yield and its quality of maize plants as affected by drought with or without salicylic acid in the two seasons

Treatments Cob length Cob weight

Grain weight per cob

1000 grain weight Oil% Carb% Protein%

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season

1st Season

2nd Season


15 (N) 26.77± 0.27a

26.66± 0.55a

244± 7.75a

237± 7.08a

219± 4.97a

215± 6.48a

364± 5.44a

366± 5.78a

3.91± 0.05a

3.72± 0.02a

71.32± 0.73a

70.83± 0.38a

9.08± 0.13a

8.96± 0.10a

20(DI1) 20.33± 0.60b

20.22± 0.59b

200± 8.59b

199± 6.37b

163± 7.70b

162± 10.11b

324± 10.46b

317± 6.61b

3.62± 0.05b

3.64± 0.02b

67.04± 1.12b

66.44± 1.07b

8.63± 0.04b

8.62± 0.04b

25(DI2) 19.11± 1.11c

19.22± 0.92b

182± 8.85c

178± 9.90c

146± 10.24c

145± 8.75b

296± 7.97c

285± 10.95c

3.24± 0.06c

3.38± 0.04c

62.16± 0.12c

62.83± 0.10c

8.09± 0.08c

8.23± 0.05c

Salicylic acid

Water (W) 19.66± 1.64b

19.88± 1.57b

183± 11.83b

184± 12.33b

151± 14.96b

152± 15.04b

305± 13.55b

297± 15.68c

3.41± 0.10c

3.47± 0.06c

64.95± 1.22c

65.23± 1.09c

8.33± 0.13c

8.39± 0.0c

100 mg/l (SA1) 23.55± 1.09a

23.44± 1.15a

226± 10.87a

218± 7.51a

193± 9.51a

189± 10.51a

345± 9.28a

343± 10.36a

3.77± 0.10a

3.67± 0.05a

68.86± 1.68a

68.46± 1.35a

8.84± 0.16a

8.83± 0.14a

200 mg/l (SA2) 23.00± 0.64a

22.77± 0.93a

216± 9.12a

211± 11.31a

185± 10.57a

180± 10.92a

335± 10.81a

329± 10.48b

3.59± 0.09b

3.60± 0.04b

66.71± 1.32b

66.41± 1.27b

8.63± 0.16b

8.59± 0.09b

Interaction

N W 26.00± 0.00b

26.00± 0.00a

226± 10.37bc

229± 6.12abc

207± 6.30a

206± 17.92abc

354± 9.93ab

349± 10.00bc

3.72± 0.02c

3.62± 0.01d

69.52± 1.20b

69.57± 0.20c

8.69± 0.01bc

8.64± 0.02cd

N SA1 27.66± 0.33a

27.66± 1.45a

258± 13.25a

243± 1.14a

230± 4.15a

227± 7.06a

372± 4.33a

381± 3.46a

4.10± 0.05a

3.82± 0.01a

73.04± 1.35a

71.84± 0.38a

9.36± 0.27a

9.35± 0.10a

N SA2 26.66± 0.33ab

26.33± 0.88a

246± 12.90ab

239± 22.79ab

220± 10.78a

211± 3.78ab

366± 12.41a

368± 5.48ab

3.39± 0.03ab

3.72± 0.02bc

71.40± 0.20ab

71.08± 0.47ab

9.20± 0.17a

8.91± 0.04b

DI1 W 18.00± 0.00d

18.00± 0.57c

176± 1.13de

176± 5.61ef

138± 8.02c

135± 5.02ef

294± 6.38de

296± 4.17d

3.48± 0.04d

3.55± 0.03de

63.65± 0.32d

63.37± 0.09e

8.49± 0.04bc

8.48± 0.01de

DI1 SA1 21.66± 0.33c

21.33± 0.33b

217± 19.36bc

216± 3.66abcd

179± 3.79b

178± 4.47bcd

351± 6.80ab

338± 3.66c

3.83± 0.01bc

3.73± 0.01a

71.15± 0.25ab

70.37± 0.57bc

8.81± 0.01b

8.76± 0.04c

DI1 SA2 21.33± 0.33c

21.33± 0.33b

208± 6.68cd

206± 4.83bcde

173± 11.26b

171± 25.50cde

329± 20.50bc

318± 7.31d

3.55± 0.05d

3.63± 0.01cd

66.34± 0.82c

65.57± 0.88d

8.61± 0.03bc

8.62± 0.02cd

DI2 W 15.00± 0.57e

15.66± 0.33d

148± 5.46e

148± 7.06f

109± 2.82d

114± 7.45f

267± 8.50e

245± 12.14e

3.30± 0.12f

3.24± 0.06g

61.70± 0.11d

62.74± 0.02e

7.82± 0.11e

8.05± 0.04g

DI2 SA1 21.33± 1.20c

21.33± 0.66b

202± 3.49cd

195± 9.81cde

169± 3.31b

163± 11.42de

312± 6.64cd

310± 0.33d

3.38± 0.04de

3.47± 0.03ef

62.41± 0.06d

63.17± 0.07e

8.36± 0.04cd

8.39± 0.06ef

DI2 SA2 21.00± 0.57c

20.66± 0.33b

194± 7.53cd

189± 19.06de

162± 12.36b

159± 2.42de

309± 0.33cd

302± 6.50d

3.29± 0.05e

3.45± 0.02f

62.39± 0.09d

62.59± 0.19e

8.10± 0.07de

8.24± 0.02f


118

untreated plants Drought may decrease photosynthetic rate, so declining the number of photoassimilates,

leading to decreasing carbohydrates, protein in the grains (Neslihan-Ozturk et al., 2002; Liu et al., 2004) and oil percentage (Nasri et al., 2008). The significant increase in the total carbohydrate by SA application might due to that the nitrogen is crucial within the structure of porphyrins, that are found in cytochrome enzymes. This increase in the cytochrome enzymes leads to a rise in the rate of photosynthesis, and in a promotion of carbohydrate synthesis and accumulation, these results in agreement with those obtained by Attia and Saad (2001). These results were in agreement with that detected by Ibrahim and Kandil, (2007). SA influences a wide biochemical processes, including stomatal regulation, photosynthetic pigments, and photosynthesis (Yildirim et al., 2008). Ghassemi-Golezani and Lotfi (2015) proved that foliar application of SA application increased the maximum quantum efficiency of PSII (Fv/Fm). In another report, Ghassemi-Golezani and Hosseinzadeh-Mahootchi (2015) declared that the chlorophyll content index (CCI), photosystem II efficiency, relative water content, leaf area index and finally seed yield of safflower were increased by SA foliar treatment. Similar results Fardus et al. (2017) that indicate the application of SA increased yield. Also, Kareem et al. (2017) revealed that SA supplementation induced the activities of various phsio-biochemical changes and may also result in inducing yield and productivity of plants. Conclusion

It could be generally concluded that salicylic acid can be used as a foliar spray on growing corn plants in the arid and semi-arid lands, as well as the newly reclaimed areas where irrigation water is a limiting factor. In addition, spraying salicylic acid at 100 mg/l lead to reduce the irrigation water quantity used during the irrigation.

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improving drought tolerance in corn (zea mays l.) by ... · (chattha et al., 2015) as well as...

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