_____________________________________________________________________________________________________
*Corresponding author: E-mail: [email protected];
Effect of Thiourea on Physiological Performance of Two Salt Affected Rice (Oryza sativa L.) Cultivars
Syeda Maasooma Zahra1,2, Abdul Wahid1, Nazimah Maqbool3 and Mohd Hafiz Ibrahim2*
1Department of Botany, University of Agriculture, Faisalabad, Pakistan.
2Department of Biology, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia.
3Department of Botany, University of Sargodha, Lyallpur Campus, Faisalabad, Pakistan.
Authors’ contributions
This work was carried out in collaboration between all authors. Author SMZ designed the study, performed the statistical analysis, wrote the protocol and wrote the first draft of the manuscript.
Authors AW and NM managed the analyses of the study. Author MHI managed the literature searches. All authors read and approved the final manuscript.
Article Information
DOI: 10.9734/ARRB/2018/41352 Editor(s):
(1)Dr. George Perry, Dean and Professor of Biology, University of Texas at San Antonio, USA.
Reviewers:
(1)Ilker Nizam, Namik Kemal University, Turkey.
(2)Mervat Sh. Sadak, Egypt.
(3)Miguel Aguilar Cortes, Universidad Autónoma del Estado de Morelos, Mexico.
(4)Lina Wang, Shandong Agricultural University, China.
Complete Peer review History:http://www.sciencedomain.org/review-history/25464
Received 15th March 2018 Accepted 24th May 2018 Published 9th July 2018
ABSTRACT
Aims: The aim of the experiment was to investigate the effect of thiourea on physiological characteristics of two rice (Oryza sativa L.) varieties under impact of salinity.
Study Design: Experiment includes two rice varieties named as B-515 and KS-282, salinity level of 150 mM, thiourea of 0.25 mM alone and in combination were arranged in a completely randomized design (CRD).
Place and Duration of Study: Old Botanical Garden, University of Agriculture Faisalabad, Pakistan, between 4th July and 21st August 2015.
Methodology: Transplants of two rice varieties, Basmati-515 and KS-282 were exposed to salinity (150 mM) and thiourea (0.25 mM) after one month of transplanting in a Completely Randomized
Original Research Article
Design with three replications. Harvesting data was taken that include fresh and dry weights, leaf area, number of tillers, photosynthetic pigments, photosynthetic rate, transpiration rate, stomatal and substomatal conductance, water use efficiency and intrinsic CO2 concentration as well as chlorophyll contents in two rice varieties.
Results: Thiourea treatment enhanced photosynthetic efficiency of Basmati-515 more than KS-282 by improving the chlorophyll and carotenoid contents and gas exchange attributes more than control.
Conclusion: Salinity profoundly affect the physiological performance of two rice varieties especially that of KS-282, while 0.25 mM thiourea application unable to mitigate the effect of salinity but thiourea alone proved to be beneficial for both the rice varieties.
Keywords: Thiourea; salinity; photosynthetic pigments; rice; leaf area.
1. INTRODUCTION
Rice (Oryza sativa L.) the main food of closely
one-half of the world's population, subsides over 20% of the total calorie intake of
human population. But in Asia, somewhere 95%
of the world's rice is produced and spent, it pays 40-80% of the calories of the Asian food.
Most of the plants are very sensitive to salinity
and also approve low salt or unlikely reserved the growth on low salinity so they show
different responses to different salinity levels [1]. The two main abiotic stresses that
harm all crops included low water level and saline soil, mainly affects the rice production 50%
world-wide [2].
Salt stress affected the large area all over the world [3]. Like other abiotic stresses
salinity also causes reduction in biochemical as well as physiological processes [4]. Impact of salinity lowered the chlorophyll contents that somehow cause reduction in net CO2
assimilation rate [5]. Salinity also disturbs ion balancing in cell by virtue cell
experiences ion toxicity as well as osmotic stress [6]. Now a day’s increase level of salinity in soil causes reduction in growth of many important crops. Salt stress has so many adversaries on plant like it alters the morphological development as well as lowered the gas exchange attributes [7].
Salinity stress can be regulated by the
application of exogenously stress alleviating chemical [8,9]. There are many plant
growth regulators which show their working even
in salinity in most plants. In addition to naturally occurring plant growth regulators, an
array of synthetic compounds has been tested
for their growth-regulatory properties with great success. For instance, synthetic
auxins (e.g., 2, 4-dichlorophenoxyactic
acid, nephthalene acetic acid etc.), cytokinins (e.g., indole butyric acid), thiourea, hydrogen peroxide etc., have been successfully used to improve plant growth under normal or subversive conditions [10]. There are quite a few nitrogen containing growth regulating substances, such as thiourea, that have specifically proven worthwhile in improving crop growth and productivity [8].
This is attributed to the fact that, in addition to growth regulatory roles, these compounds are
metabolized and provide as a source of nitrogen nutrition [11]. Thiourea is an important
molecule with two functional groups; ‘thiol’ is important to oxidative stress response and
‘imino’ partly fulfils the N requirement. It is highly water soluble and easily absorbed in the living tissues.
Exogenous application of thiourea (TU) is thought to have a significant role in minimizing oxidative damage and processes involved therein. For example, externally applied TU alleviated the injurious effects of salinity in Brassica juncea seeds by altering a number of effector and signaling processes [12]. Thiourea has also been reported to significantly improve growth, yield and water use efficiency of mung bean (Phaseolus vulgaris) seedlings, pearl millet [13] and cluster bean plants [14] under arid and semi-arid conditions. Salt stress is among of the biggest problem that is specially affecting the production of rice. The ability to stand against salinity is main factor that enhances the productivity of plant [15]. Survey done that 800 million ha of whole world area isaffected by salinity [16]. Therefore, in the present study our main objective was to assess the effect of exogenous application thiourea onvarious morphological as well as gas exchange parameters of rice plants under salt stress in two Pakistan rice varieties namely Basmati-515 and KS-282.
2. MATERIALS AND METHODS
2.1 Experimental Location and Treatments
A pot experiment was carried out in net-house of Old Botanical Garden, University of Agriculture, Faisalabad- Pakistan. Thirty days old seedlings of two rice (Oryza sativa L.) varieties; Basmati- 515 and KS-282 were obtained from fields of Department of Agronomy, University of Agriculture, Faisalabad. Seedlings of both the varieties were transplanted in soil filled pots arranged in completely randomized design with three replicates. Almost after one week when transplants were established treatments were applied. Treatments include control (only water), NaCl (150 mM), Thiourea (0.25 mM) and their interactive effect. Data for morphological attributes and gas exchange were recorded right after 15 days when treatments were applied.
2.2 Morphlogical Parameters 2.2.1 Shoot and root fresh weights (g)
Fresh weights of shoots and roots of three plants per replicates, per treatment were determined immediately after uprooting the plants with the help of top loading balance and mean values were calculated.
2.2.2 Number of tillers
Number of tillers of all the application treated plants replicates was counted manually.
2.2.3 Leaf area (cm2) per plant
Leaf area as calculated by measuring the maximum width and length and then leaf area of each plant of each treatment is calculated according to following formula.
Total leaf area= maximum leaf length × maximum leaf width × correction factor
Where, correction factor (C.F) = 0.68 2.3 Gas Exchange Parameters
Net photosynthetic rate (A), transpiration rate (E), sub-stomatal CO2 concentration (Ci), stomatal conductance (gs) and water use efficiency (A/E) were measured from a fully expanded youngest leaf by using an open system LCA-4 ADC portable infrared gas analyzer (Analytical Development Company, Hoddeson, England).
2.4 Irga
The specifications /adjustments of IRGA were as follows: leaf surface area 11.35 cm3, ambient CO2 concentration (Cref) 342.12 µmol/mol, temperature of leaf chamber (Tch) varied from 39.2 to 43.9ºC, leaf chamber volume gas flow rate (v) 396 ml/min, leaf chamber molar gas flow rate (U) 251 µmol/sec, ambient pressure (P) 99.95 kPa, molar flow of air per unit leaf area (Us) 221.06 mol/m2/sec, PAR (Qleaf) at leaf surface was maximum up to 918 µmol/m2. 2.5 Chlorophyll Content
The concentration of chlorophyll contents was determined by using the method of Arnon [17].
For this purpose 0.1 g fresh leaves were chopped and extracted in 10mL of 80% acetone for one day in a refrigerator then absorbance was recorded at 663, 645 and 480 nm using a spectrophotometer (Hitachi-220, Japan).
2.6 Observations
After 15 days of applying all treatments harvesting of experiment was made shoot fresh as well as dry weight of randomly selected 3 rice plants of each variety from each pot of a single replicate was taken and averaged. After that these samples were put in an oven at 65°C for 72 h to record shoot dry weight. Leaf area of rice plant was measured at harvesting by a leaf area meter.
2.7 Data Analyses
The experiment was arranged in a completely randomized design (CRD) with three replicates and the data were analyzed using a software named CoSTAT V 6.3 (developed by, Cohort software, Berkeley, California).
3. RESULTS AND DISCUSSION 3.1 Results
Salt stress significantly reduced shoot fresh weight of both rice cultivars. A considerable variation was found in this parameter. Cultivar KS-282 had higher value of shoot fresh weight under thiourea application as well as in salinity while root fresh weight of Basmati-515 reduced due to imposition of salt stress in rooting medium. Same case was observed in shoot dry weight on the other hand, number of tillers for
both varieties increased when the cultivars subjected to salinity and there seems to be reduction when they impose to thiourea. Leaf area reduced in salinity and enhanced when thiourea was applied (Table 1).
3.1.1 Net photosynthetic rate (A)
Net photosynthetic rate showed substantial reduction in both cultivars as compared to control in saline conditions. Variable results were noted for rice varieties, Basmati-515 showed
positive response under thiourea application (Fig.1).
3.1.2 Transpiration rate (E)
Results for transpiration rate (E) showed variation under salinity. Basmati-515 showed positive response as compared to control while in KS-282 rate of transpiration badly decreased because of salinity, however application of thiourea impart significant results in KS-282 because application of thiourea compensate effect of salinity (Fig. 2).
Fig. 1. Measurements of net photosynthetic rate in two rice cultivars under salinity treated with thiourea
Fig. 2. Measurements of transpiration rate in two rice cultivars under salinity treated with thiourea
a
c
ab
d a
c bc
e
0 4 8 12 16 20
Control 150mM NaCl 0.25mM TU NaCl+TU A(µmol CO2m-1s-1)
Basmati-515 KS-282
bc
cde
a
cde bcd
e
ab
de
0 2 4 6 8 10 12 14
Control 150mM NaCl 0.25mM TU NaCl+TU E(mmol H2O m-2s-1)
Basmati-515 KS-282
5
Table 1. Morphological changes induced by NaCl and thiourea in two selected rice cultivars
SFW SDW RFW RDW No. Tillers LA
Basmati-515
Control 31.2 ± 0.5 a 8.2 ± 0.7 a 20.8 ± 1.0 a 7.0 ± 0.1 a 4 ± 0.6 cd 75.6 ± 2.8 ab
150mM NaCl 17.4 ± 0.5 c 4.2 ± 0.5 bc 10.4 ± 0.9 c 2.5 ± 0.3 cd 4.7 ± 0.3 cd 49.3 ± 3.2 cd
0.25mM TU 23.1 ± 0.5 b 5.0 ± 0.7 b 16.4 ± 1.3 b 5.3 ± 0.2 b 3.3 ± 0.3 d 88.1 ± 5.6 a
NaCl+TU 9.6 ± 1.3 d 3.4 ± 0.4 cd 4.8 ± 0.5 d 1.0 ± 0.3 d 5 ± 0.6 bc 62.1 ± 3.0 bc
KS-282
Control 25.7 ± 1.4 b 4.8 ± 0.6 bc 9.7 ± 1.3 c 3.0 ± 0.3 c 7 ± 0.6 a 66.8 ± 3.4 a
150mM NaCl 16.4 ± 1.3 c 3.4 ± 0.1 cd 9.3 ± 0.4 c 2.0 ± 0.1 c 6.3 ± 0.6 ab 41.7 ± 5.1 d
0.25mM TU 18.1 ± 0.7 c 3.1 ± 0.4 de 8.3 ± 0.4 c 1.9 ± 0.2 cd 6.3 ± 0.3 ab 70.7 ± 5.0 ab
NaCl+TU 8.9 ± 1.3 d 2.2 ± 0.5 e 3.9 ± 0.5 d 1.1 ± 0.2 d 4.7 ± 0.3 cd 55.8 ± 1.4 cd
SFW = Shoot fresh weight; SDW = Shoot dry weight; RFW = Root fresh weight; RDW = Root dry weight; LA = Leaf area; Mean ± Standard Error Alphabets represents multiple comparison among treatments for each parameter
3.1.3 Stomatal conductance (gs)
Stomatal conductance (gs) of both rice cultivars showed variable results in salinity stress as well as in thiourea medium. In both KS-282 and Basmati-515 stomatal conductance significantly reduced. Exogenous application of thiourea enhanced stomatal conductance in both cultivars (Fig. 3).
3.1.4 Sub-stomatal conductance CO2 (Ci)
Salinity also significantly reduced sub-stomatal CO2 (Ci) concentrations in rice cultivars. A considerable variation was recorded in this parameter. Salinity somehow reduces Ci value in both varieties while application of thiourea enhanced sub stomatal conductance in Basmati- 515 as well as KS-282 (Fig. 4).
Fig. 3. Measurements of stomatal conductance in two rice cultivars under salinity treated with thiourea
Fig. 4. Measurements of sub-stomatal conductance in two rice cultivars under salinity treated with thiourea
b
c
a
e bc
d
a
f
0 100 200 300 400 500 600
Control 150mM NaCl 0.25mM TU NaCl+TU gs (mmol m-2s-1)
Basmati-515 KS-282
b
a a a
a a a a
0 50 100 150 200 250 300 350 400
Control 150mM NaCl 0.25mM TU NaCl+TU Ci(µmol mol-1)
Basmati-515 KS-282
3.1.5 Water use efficiency (WUE)
Salinity enhanced the water use efficiency in both B-515 as well as KS-282 rice cultivars as compared to control, however application of exogenous TU marked reduction in WUE in both varieties as in contrast to control and salinity stress (Fig. 5).
3.1.6 Chlorophyll contents
Salt stress showed reduction in chl a as well as chl b in both varieties and exogenous
application of thiourea increased chl a, b attribute. On the other hand, salt stress also reduced the total chlorophyll (Chl a+b) contents in rice cultivars, and thiourea application compensate it production in a positive way (Fig.
6).
3.1.7 Carotenoids
Salinity cause reduction for both Basmati-515 as well as KS-282 in carotenoids while applied thiourea increased its value in both rice cultivars (Fig. 6).
3.2 Discussion
Rice considered among is salt sensitive crop.
Deprived growth and production of rice crop under salt stress could be due to salt induced osmotic stress and specific ion toxicity [18]. In the present study, a significant decrease in
chlorophyll content was observed in both varieties under salinity as compared to control.
Salt- induced decrease in chlorophyll contents has already been reported in many crops such as in sunflower [19], wheat [20,21]. On the other hand, chlorophyll biosynthesis has been reported to be exaggerated more critically on contrast to chlorophyll degradation [22]. One of the main restrictive factor and abiotic stress is salt stress for plant productivity globally [23]. In salt stress, plants have to oppose reduction in external water potential as well as ion toxicity [24].
There are so many manmade organic compounds that can enhance plant growth as well as production because of their biological properties [25]. Thiourea has a role in intermittent plant growth under both saline and non-saline conditions [26]. According to recent study [27]
thiourea can recommended for both saline and non-saline because of its dissolving property that can be easily absorbed by living tissues.
In E. amoenume, increased salinity causes reduction in vegetative growth which changes in morphological attributes that caused lower turgor pressure inside the cells and in result cell growth experiences enlargement while leaf area decreased [28]. Same results were observed
when there was reduction in shoot as well as root length experienced in wheat because of
nutrient uptake imbalance that leads to inhibition of water for osmotic adjustment under salt stress.
Fig. 5. Measurements of water use efficiency in two rice cultivars under salinity treated with thiourea
Fig. 6. Measurements of photosynthetic pigments in two rice cultivars under salinity treated with thiourea
In rice cultivars root and shoot fresh as well as dry weight greatly affected when plant subjected to salinity. Same results were observed when seedling biomass i.e. fresh and dry weights were also decreased with enhanced amount of NaCl in comparison with control [29]. Almost similar results were also reported in different plants under salinity [30]. Application of thiourea nullifies the negative effects of salt stress on root, shoot and leaf area in wheat [31] and cotton [32].
It was noted that in rice cultivars salinity causes reduction in chlorophyll contents (a, b and carotenoids). Essential pigments of photosynthesis are chlorophyll a, b and carotenoids. It is being observed that decline in photosynthetic pigments is due to high salt stress that causes damage to thylakoid membrane, where all different types of photosynthetic pigments (Chlorophyll a, b and carotenoids) are accumulated [33]. Such drop-in chlorophyll a and b were also reported in sunflower [34], turnip [35]
and safflower [36,37] radish. Chlorophyll contents in maize leaves were enhanced when thiourea was applied. Thiourea enhanced metabolic rate of cell and impediment senescence by protecting and inhibiting chloroplast from senescing that increased the biosynthesis of chlorophyll in wheat [38].
Salt stress to growing medium lowers the gas exchange activity. It has also been studied by researcher that when plant subjected to high
salinity level they showed decline in transpiration rate (E) as well as photosynthetic activity and stomatal conductance (gs) and water use efficiency (WUE) [39]. Under salt stress reduction in stomatal conductance (gs) caused decline in net photosynthetic rate (A), internal CO2 concentration (Ci) and transpiration rate (E) [40], [41]. Exogenously applied thiourea increase the activity of gas exchange attributes. These results were related to study that was done on cluster bean [42] where application of thiourea proved to be helpful in improving gas exchange activity.
4. CONCLUSION
The application of thiourea improved the physiological activities of rice cultivar, among two rice cultivars KS-282 proved to be sensitive to salinity while with exogenous application of 0.25 mM thiourea KS-282 found to be non-beneficial regarding to almost all attributes. On the other hand, Basmati-515 showed less positive response when it was subjected to exogenous thiourea but somehow compensation response was also observed as compared to salinity.
Further research is recommended to find out the low concentrations of thiourea for rice which can mitigate the effect of salinity.
COMPETING INTERESTS
Authors have declared that no competing interests exist.
REFERENCES
1. Sheekh MM, Omar HH. Effect of high salt stress on growth and fatty Acids content of the unicellular green algae Chlorella vulgaris. Amer J Microbiol. 2002;55:181- 191.
2. Mahajan S, Tuteja N. Cold, salinity and drought stresses: An overview. Arch Biochem Biophys. 2005;444:139-158.
3. Ashraf M. Biotechnological approach of improving plant salt tolerance using antioxidants as markers. Biotechnol Adv.
2009;27:84-93.
4. Habib N, Ashraf M, Ali Q, Perveen R.
Response of salt stressed okra (Abelmoschus esculentus Moench) plants to foliar-applied glycine betaine and glycine betaine containing sugar beet extract.
South Afr J Bot. 2012;83:151-158.
5. Ashraf M. Some important physiological selection criteria for salt tolerance in plants. Flora. 2004;199:361-376.
6. Ashraf M, Harris PJC. Potential biochemical indicators of salinity tolerance in plants. Plant Sci. 2004;166:3-16.
7. Sairam RK, Tyagi A. Physiology and molecular biology of salinity stress tolerance in plants. Curr Sci. 2004;86:407- 421.
8. Farooq M, Wahid A, Kobayashi N, Fujita D.
Basra SMA. Plant drought stress: effects, mechanisms and management. Agron Sustain Dev. 2009b; 28:185-212.
9. Farooq M, Kobayashi N, Wahid A, Ito O, Basra SMA. Strategies for producing more rice with less water. Adv Agron. 2009a;
101:351-387
10. Wahid A, Gelani S, Ashraf M, Foolad MR.
heat tolerance in plants. An overview.
Environ Exp Bot. 2007;61:199-233.
11. Perveen A, Wahid A, Mahmood S, Hussain I, Rasheed R. Possible mechanism of root-applied thiourea in improving growth, gas exchange and photosynthetic pigments in cadmium stressed maize (Zea mays). Braz J Bot.
2015;38:71‒79.
12. Srivastava AK, Ramaswamy NK, Mukopadhyaya R, Chiramal JMG, D’Souza SF. Thiourea modulates the expression and activity profile of mtATPase under salinity stress in seeds of Brassica juncea.
Ann Bot. 2009;103:403–410.
13. Misra AN. Water use efficiently of pearl millet (Pennisetum americanum l. Leeke) genotypes under mid-season moisture
stress. Acta Agron Hungarica. 1991;40:
417–22.
14. Garg BK, Burman U, Kathju S. Influence of thiourea on photosynthesis, nitrogen metabolism and yield of clusterbean (Cyamopsis tetragonoloba (l.) Taub.) under rainfed conditions of Indian arid zone.
Plant Growth Regul. 2006;48:237–4.
15. Momayezi MR, Zaharah AR, Hanafi MM, MohdRazi I. Agronomic characteristics and proline accumulation of Iranian rice genotypes at early seedling stage under sodium salts stress. Malays J Soil Sci.
2009;13:59-75.
16. FAO. Land and Plant Nutrition Manangement Service. 2008.
Available:http://www.fao.org/agb/agl /agll/spush/
17. Arnon DT. Copper enzyme in isolated chloroplasts polyphenoloxidase in Beta vulgaris. Plant Physiol. 1949;24:1-15.
18. Duan D, Liu X, Khan MA, Gul B. Effects of salt and water stress on the germination of Chenopodium glaucum L., seed. Pak J Bot. 2004;36:793-800.
19. Akram MS, Ashraf M, Shahbaz M, Akram NA. Role of foliar applied potassium from different sources on physio-biochemical attributes of sunflower (Helianthus annuus L.) under salt stress. J Plant Nutr Soil Sci.
2009;172:88493.
20. Arfan M, Athar HR, Ashraf M. Does exogenous application of salicylic acid through the rooting medium modulate growth and photosynthetic capacity in two differently adapted spring wheat cultivars under salt stress. J Plant Physiol. 2007;6:
685-694.
21. Ashraf MA, Ashraf M. Salt-induced variation in some potential physiological
attribute of two genetically diverse spring wheat (Triticum astivum L.)
cultivars: Photosynthesis and photosystem II efficiency. Pak J Bot. 2012;
44:53-64.
22. Santos CLV, Campos A, Azevedo H, Caldeira G. In situ and in vitro senescence induced by KCl stress: Nutritional imbalance, lipid peroxidation and antioxidant metabolism. J Exp Bot. 2001;
52:351-360.
23. Debez A, Saadaoui D, Ramani B, Ouerghi Z, Koyro HW, Huchzermeyer B, Abdelly C.
Leaf H+ ATPase activity and photosynthetic capacity of Cakile maritima under increasing salinity. Environ Exp Bot.
2006;57:285-29.
24. Romero MR, Jurado O, Cuartero J. Silicon alleviates the deleterious salt effect on tomato plant growth by improving plant water status. J Plant Physiol. 2006;163:
847-855.
25. Tang Y, Posner MI. Attention training and attention state training. Trends Cogn Sci.
2009. 13; 222–227.
26. Anjum F, Wahid A, Farooq M, Javed F. Potential of foliar applied thiourea
in improving salt and high temperature tolerance of bread wheat (Triticum aestivum L.). Int J Agric Biol.
2011;13:251–256.
27. Mani F, Bettaieb T, Zheni K, Doudech N, Hannachi C. Effect of thiourea
on yield and quality of potato (Solanum tuberosum L.). J. Stress Physiol. Biochem.
2013;9:87-95.
28. Jampeetong A, Brix H. Effect of NaCl salinity on growth, morphology, Photosynthesis and proline accumulation of Salvia natans. Aquat. Bot. 2009;91:181- 186.
29. Hussainn S, Khaliq A, Matloob A, Wahid A, Afzal I. Germination and growth response of three wheat cultivars to NaCl salinity.
Soil Environ. 2013;32:36-43.
30. Basalah MO. Action of salinity on seed germination and seedling growth of Solanum melongeana L. J Agric Res Kafer El-Shaikh Univ. 2010;36:64-73.
31. Parveen S, Shahbaz M, Ashraf M.
Regulation in gas exchange and quantum yield of photosyatem II (PSII) in salt stressed and non-stressed wheat plant raised from seed treated with triacontanol.
Pak J Bot. 2010;42:3073-3081.
32. Shaheen HL, Shahbaz M, Ullah I. Iqbal MZ. Morpho-physiological responses of cotton (Gossypium hirsutum) to salt stress.
Int J Agric Biol. 2012;14:980-984.
33. Shaheen S, Naseer S, Ashraf M, Akram NA. Salt stress affects water relations, photosynthesis and oxidative defense mechanism in Solanum melongena. J Plant Interct. 2013;8:85-96.
34. Akram, NA, Ashraf M. Improvement in growth, chlorophyll pigments and
photosynthetic performance in salt-
stressed plants of sunflower (Helianthus annuus L.) by foliar application
of 5-aminolevulinic acid. Agrochemica 2011;55:94-104.
35. Noreen S, Ashraf M, Hussain M, Jamil A.
Exogenous application of salicylic acid enhances antioxidative capacity in salt stressed sunflower (Helianthus annuus L.) plants. Pak J Bot.
2009;41:473-479.
36. Siddiqi EH, Ashraf M, Hussain M, Jamil A. Assessment of
inter-cultivar variation for salt tolerance in safflower (Carthamus tinctorius L.) using gas exchange characteristics as selection criteria. Pak J Bot. 2009;41:2251-2259.
37. Noreen Z, Ashraf M. Changes in antioxidant enzymes and some key metabolites in some genetically diverse cultivars of radish (Raphanus sativus L.).
Environ Exp Bot. 2009;67:395-402.
38. Amin AA, Rashad El-ShM, Gharib FAE. Changes in morphological,
physiological and reproductive characters of wheat plants as affected by foliar application with salicylic acid and ascorbic acid, Australian J Basic Appl Sci. 2008;2:
252-261.
39. Ashraf M. Relationships between leaf gas
exchange characteristics and growth of differently adapted populations
of Blue panicgrass (Panicum antidotale
Retz.) under salinity or waterlogging.
Plant Sci. 2003;165: 69-75.
40. Zheng L, Shannon MC, Lesch SM. Timing of salinity stress affects rice growth and yield components. Agric Water Manag.
2001;48:191-206.
41. Parida AK, Das AB. Salt tolerance and salinity effects on plants A review.
Ecotoxicol Environ Safe. 2005;60:324-349.
42. Burman U, Garg BK, Kathju S.
Interactive effects of thiourea and phosphorus on cluster bean under water stress. Plant Biol. 2003;48:61-
65.
_________________________________________________________________________________
© 2018 Zahra et al.; This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Peer-review history:
The peer review history for this paper can be accessed here:
http://www.sciencedomain.org/review-history/25464
