The activity of antioxidative enzymes in three strawberry cultivars ...

Acta Physiol Plant (2008) 30:201–208 DOI 10.1007/s11738-007-0108-4

ORIGINAL PAPER

The activity of antioxidative enzymes in three strawberry cultivars related to salt-stress tolerance Ece Turhan Æ Hatice Gulen Æ Atilla Eris

Received: 22 November 2006 / Revised: 9 August 2007 / Accepted: 12 September 2007 / Published online: 25 October 2007 Franciszek Go´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako´w 2007

Abstract Effects of salt stress on the time course of stomatal behaviors and the activity of antioxidative enzymes such as catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11), and glutathione reductase (GR) (EC. 1.6.4.2) were studied in three strawberry cultivars. The responses of the cultivars ‘Camarosa’, ‘Tioga,’ and ‘Chandler’ were compared when they were irrigated with nutrient solution containing 0, 8.5, 17.0, and 34.0 mM sodium chloride (NaCl) for 30 days. A significant reduction in stomatal conductance (gs) was seen particularly on the 30th day of the salt treatments only in Camarosa, which is parallel to transpiration rate (E). CAT activities decreased in all of the salt treatments only in Tioga, while it remained almost unchanged or slightly increased depending on the period in Camarosa and Chandler. APX activity sharply increased in 17.0 and 8.5-mM NaCl treatments for 30 days in Camarosa and Tioga, respectively, whereas it linearly increased based on the NaCl treatments in Chandler. On the other hand, only Camarosa demonstrated a sharp increase in GR activity induced by salinity applied for 30 days. All the data indicated that control of the stomatal behavior, the higher salt-stress tolerance (LT50) and higher constitutive activity of antioxidant enzymes made Camarosa and Tioga relatively salt-tolerant cultivars.

Keywords Antioxidative enzymes Salt stress tolerance (LT50) Stomatal conductance (gs) Strawberry Transpiration rate (E)

Abbreviations APX Ascorbate peroxidase CAT Catalase E Transpiration rate EDTA Ethylenediamine-tetraacetic acid GR Glutathione reductase gs Stomatal conductance H2O2 Hydrogen peroxide Kphosphate Potassium phosphate buffer LT50 Salt stress tolerance NaCl Sodium chloride NADPH bNicotinamide adenine dinucleotide phosphate PVP-40 Polyvinylpyrrolidone 40 ROS Reactive oxygen species

Introduction Communicated by W. Bielawski. E. Turhan (&) Canakkale Onsekiz Mart University, Bayramic Vocational School, 17700 Bayramic, Canakkale, Turkey e-mail: [email protected] H. Gulen A. Eris Faculty of Agriculture, Department of Horticulture, Uludag University, Gorukle, Bursa 16059, Turkey

Environmental stresses such as sodium chloride salt (NaCl) and drought are among the factors most limiting to plant productivity (Greenway and Munns 1980; Bohnert et al. 1995). Such stresses are becoming even more prevalent as the intensity of agriculture increases. Therefore, elucidation of the mechanisms by which plants perceive and transduce these stresses are critical if we are to understand the plant response and introduce genetic or environmental improvement to stress tolerance (Borsani et al. 2001).

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Salinity stress can affect several physiological and metabolic processes such as photosynthesis (Borsani et al. 2001; Chattopadhayay et al. 2002), protein synthesis, respiration, nitrogen assimilation, and phytohormone turnover (Arshi et al. 2002). Plant responses to stress are complex (Chaves et al. 2003), which depends on a number of interrelated factors based on morphological, biochemical, and physiological processes (Greenway and Munns 1980; Arshi et al. 2002; Qasim et al. 2003). The organic solutes such as sugars, organic acids, polyols, and many nitrogen-containing compounds such as amino acids, amides, protein, and quaternary ammonium compounds have been found to be helpful in osmoregulation (Grumet et al. 1985) and in tolerance of toxicity of ions under salt stress (Greenway and Munns 1980). One of the biochemical changes occurring when plants are subjected to biotic or abiotic stresses is the production of reactive oxygen species (ROS), such as superoxide (O2–), hydrogen peroxide (H2O2), and hydroxyl radicals (OH) (Foyer et al. 1994; Mittler 2002; Neill et al. 2002; Foyer and Noctor 2005). These ROS are highly reactive and their reactivity dictates that they are highly energetic compounds, able to undertake catalytic functions in the absence of enzymes (e.g., in cell wall cleavage and resynthesis). This property means that they are very well suited to the activation of signaling cascades (Foyer and Noctor 2005). Salt-tolerant plants, besides being able to regulate the ion and water movements, should also have a better antioxidative system for effective removal of ROS (Borsani et al. 2001; Rout and Shaw 2001; Shalata et al. 2001; Sudhakar et al. 2001; Chaparzadeh et al. 2004). In plant cells, one such protective mechanism is an antioxidant system, composed of both non-enzymatic and enzymatic antioxidants (Foyer et al. 1994). Antioxidative enzymes like superoxyde dismutase (SOD), catalase (CAT), peroxidase (PRX), ascorbate peroxidase (APX), and glutathione reductase (GR) are the most important components in the scavenging system of ROS (Mc Kersie and Leshem 1994; Noctor and Foyer 1998). To mitigate and repair damage initiated by ROS, plants have developed a complex antioxidant system (del Rio et al. 2002). Salt stress can induce conditions of oxidative stress (Zhu 2000). Changes in the activity of antioxidant enzymes in response to salinity (Faltin et al. 1998; Shalata and Tal 1998) were reported as different in tolerant and sensitive cultivars in various plant species (Sairam et al. 2002; Meloni et al. 2003; Tsai et al. 2005). In strawberry, as well as in some other crops, response of the cultivars to salt stress has been well documented using agronomic and physiological characteristics (Barroso and Alvarez 1997; Turhan 2002; Turhan and Eris 2004, 2005). According to morphologic properties and ionic

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Acta Physiol Plant (2008) 30:201–208

composition of the cultivars, Camarosa and Tioga are reported to be relatively salt-tolerant (Turhan 2002). Turhan and Eris (2004) also indicated that 8.5, 17.0, and 34.0 mM NaCl applications caused osmotic effects in Camarosa strawberry cultivar and Camarosa has the ability to osmotic regulation. In addition, it was indicated in our previous study related to PRX activity that salt stress increased total and specific PRX activity as compared with the control in strawberry cultivars (Gulen et al. 2006). However, there have been no reports indicating the other antioxidative responses of strawberry cultivars to salinity, yet. Therefore, the aim of the present work was to investigate the effects of salt stress on the activity of three antioxidative enzymes (CAT, APX, and GR) in three strawberry cultivars in order to better understand the genotypic difference in salt-stress tolerance (LT50). In addition, the time course of the stomatal conductance (gs) and transpiration rate (E) were also evaluated to determine the stomatal response to salinity during the experiment. The data from this study can supply us information on the possible involvement of antioxidant enzymes in the mechanism of LT50 related to cellular damage by NaCl stress in strawberry plants, and also could allow improving our knowledge about the molecular mechanisms of saltinduced oxidative stress in strawberry plant.

Materials and methods Plant material and salt-stress conditions Cold-stored (frigo) seedlings of three strawberry cultivars, Camarosa, Chandler, and Tioga, which are widely grown and are important cultivars in Turkey, were planted in 14 · 12-cm2 pots using perlite in a greenhouse. Twenty days after planting (plants had 4–5 leaves), plants were watered with modified 1/3 Hoagland nutrient solution (Awang et al. 1993) containing 0 (control), 8.5, 17.0, and 34 mM NaCl (electrical conductivities of 2.0 ± 0.2, 3.0 ± 0.4, 3.8 ± 0.5, and 5.0 ± 0.6 dS m–1, respectively, in their root zones) for 15 or 30 days. It was attempted to keep the quantity of drainage water at 30% of the amount of nutrient solution applied. Plants were grown in a greenhouse with day/night mean temperature of 32/14C, average relative humidity of 70%, average photoperiod of 16 h.

Stomatal conductance (gs) and transpiration rate (E) Stomatal conductance and E of leaves were determined using a portable steady-state porometer (LI-1600 M, LI-


COR, Lincoln, NE, USA). Measurements were made on the 10th, 20th, and 30th days of the experiment in the same leaves (fully expanded mature leaves of each sampled plant), in the middle of the day (between 12:00 and 14:00).

Salt stress tolerance (LT50) Salt-stress tolerance of leaf tissues was evaluated by the method of Arora et al. (1992), with some modifications. Leaf discs 2 cm in diameter were cut from fully expanded uniform leaves from each of the three plants (replicates) per treatment (unstressed-control, 8.5, 17.0, and 34.0 mM NaCl). Discs were lightly rinsed in distilled water, gently blotted with paper, and placed in test tubes (one disc per tube). Then, 20 ml of distilled water was added to each test tube. Samples were then vacuum infiltrated to allow uniform diffusion of electrolytes and shaken on a gyratory shaker at 250 rpm for 4 h at room temperature. After incubation, electrical conductivity of each solution was measured using a conductivity meter (WTW TetraCon 325 model, InoLab Cond Level 1, Weilheim, Germany). After measuring initial electrolyte leakage (C1), samples were heat-killed (autoclaved at 121C, 124 kPa for 15 min) and final electrolyte leakage (C2) was measured at room temperature. Ion leakage was calculated using the following equation: % electrolyte leakage = C1/C2 · 100. Percentage injury at each salt treatment was calculated from ion leakage data using the equation (Arora et al. 1992): % injury = [(%L(t)–%L(c))/(100–%L(c))] · 100, where % L(t) and % L(c) are percentage ion leakage data for the treatments and control samples, respectively. LT50 was defined as the salt concentration at which 50% injury occurred (Arora et al. 1992). All measurements were replicated three times.

Enzymatic activity Fully expanded leaf material was collected at the end of each NaCl treatment periods (15 and 30 days after NaCl applications). Triplicate samples of leaf tissues were frozen immediately and ground in liquid N2 and stored at –80C until used. Enzymes were extracted at 0–4C from 0.5 g of leaves, by grinding them with mortar and pestle in 1.0% polyvinylpyrrolidone 40 (PVP-40) and 2 ml of the following extraction solution (Moran et al. 1994): for CAT, 100 mM potassium phosphate buffer (K-phosphate), pH 7.0, 0.1 mM ethylenediamine-tetraacetic acid (EDTA), 0.1% Triton; for APX, 50 mM K-phosphate buffer, pH 7.8, 50 mM ascorbate; for GR, 50 mM K-phosphate, pH 7.6, 0.1 mM EDTA.

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The homogenate was centrifuged at 15,000g for 20 min at 4C. The supernatants were used for the enzymatic assays. CAT was assayed by monitoring the consumption of H2O2 at 240 nm (Rao et al. 1996). The activity was calculated using the extinction coefficient of 39.4 mM– 1 cm–1 for H2O2. APX activity was determined by measuring decrease in absorbance of the oxidized ascorbate at 290 nm, according to Nakano and Asada (1980). The concentration of oxidized ascorbate was calculated using extinction coefficient (£ = 2.8 mM–1 cm–1), 1 U of APX was defined as 1 lmol ml–1 ascorbate oxidized per minute. GR activity was determined by following the oxidation of b-Nicotinamide adenine dinucleotide phosphate (NADPH) at 340 nm (extinction coefficient 6.2 mM–1 cm–1) (Cakmak and Marschner 1992).

Statistics The experiment was arranged in a randomized block design with three replications. Data were tested by SPSS 13.0 for Windows program and mean separation was accomplished by least significant difference (LSD) test at P \ 0.05.

Results Stomatal conductance and transpiration rate The time courses of gs and E in the leaf of the three strawberry cultivars are given in Fig. 1. gs was almost the same level in all the NaCl treatments and control plants of all the cultivars at the 10th day of the salt treatments (Fig. 1-I). Considering the measurement of 20th day of salt treatments, gs was significantly increased by the NaCl treatments only in Tioga. On the other hand, gs was sharply decreased by the NaCl treatments only in Camarosa while it was slightly increased in Tioga and Chandler at the 30th day of the salt treatments. Similar to gs, E was almost unchanged by the NaCl treatments on the 10th day of the treatments (Fig. 1-II). NaCl treatments caused a decrease in E measured on the 20th day of the salt treatments in Camarosa and Chandler while it caused an opposite effect in Tioga. However, on the 30th day of the salt treatments, E decreased in NaCltreated Camarosa plants, especially in the highest NaCl concentration (34.0 mM) while it increased in Tioga and remained almost unchanged in Chandler comparing with control plants. All the results showed that the effects of period, cultivars, NaCl, and their interactions on gs were significant except the interaction between the period and the NaCl (Table 1). Regarding the E, except NaCl and its interaction

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Fig. 1 Time course of stomatal conductance-gs (I) and transpiration rate-E (II) of three strawberry cultivars, Camarosa (a), Tioga (b), and Chandler (c) under 0, 8.5, 17.0, and 34.0 mM NaCl treatments of 10, 20, and 30 days. Values indicate average ± SD of three replications

Table 1 Results of variance analysis (ANOVA) of sampling period (P), cultivar (Cv.), NaCl concentrations (NaCl), and their interactions for stomatal conductance (gs), transpiration rate (E), salt stress tolerance (LT50), CAT, APX, and GR activities Dependent variable

Independent variable P

Cv.

NaCl

P · Cv.

P · NaCl

Cv. · NaCl

P · Cv. · NaCl

Stomatal conductance (gs)

13.32*

6.32*

0.89*

5.47*

0.52 ns

6.13*

4.65*

Transpiration rate (E)

175.43*

32.35*

1.96 ns

14.06*

1.95 ns

5.49*

3.78*

Salt stress tolerance (LT50) CAT activity

27.81* 3.56 ns

40.03* 47.51*

–nd 14.63*

1.97* 0.98 ns

–nd 1.48 ns

–nd 26.59*

–nd 4.62*

APX activity

231.52*

0.30 ns

53.39*

7.29*

63.55*

47.20*

55.61*

GR activity

33.77*

64.82*

17.15*

45.61*

29.51*

27.49*

17.05*

Number represent F-values at 5% level nd None detected *,

ns

Significant and non-significant at P \ 0.05

with period, all the variables and their interactions were found statistically significant.

Salt-stress tolerance Salt-stress tolerance expressed by LT50 of leaf tissues from three strawberry cultivars is presented in Fig. 2. Regarding the effect of period, long period of NaCl treatments (30 days) caused less LT50 than short period of NaCl treatments (15 days) in the three cultivars. Comparison of the LT50 of the three cultivars, Camarosa and Tioga exhibited greater LT50 than Chandler in both periods of salt treatments. The data indicated that the effects of period, cultivar and their interactions on the LT50 were statistically significant (Table 1).

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Enzyme activities The activities of CAT remained almost unchanged and slightly increased in 15 and 30 days of salt treatments, respectively, in Camarosa, while it decreased in both 15 and 30 days of salt treatments in Tioga (Fig. 3-I). However, in Chandler, CAT activity remained almost unchanged in both 15 and 30 days of salt treatments even though it slightly decreased in the highest NaCl treatment (34.0 mM) for 30 days. According to the variance analysis of CAT activity data in Table 1, the effects of periods and its interactions with cultivars and NaCl were not significant while the effects of other variables and their interactions were significant. Sodium chloride treatments for 15 days did not change the activity of APX in Camarosa and Tioga, while it


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maximum level in 34.0 mM NaCl treatment. The data indicated that the effects of period, cultivar, NaCl, and their all interactions on the activity of APX were statistically significant except the effects of cultivar (Table 1). In three of the cultivars, the activity of GR remained almost unchanged in both 15 and 30 days of NaCl treatments while only that of GR sharply increased in 17 mM NaCl treatment and remained almost the same level in 34.0 mM NaCl treatment for 30 days in Camarosa (Fig. 4). Results of variance analysis (Table 1) indicated that the effects of all the independent variables and their interactions on the GR activity were significant.

Discussion

Fig. 2 The salt-stress tolerance of leaf tissues of three strawberry cultivars under 8.5, 17.0, and 34.0 mM NaCl treatments during 15 and 30 days. LT50 was assessed by electrolyte leakage. Values indicate average ± SD of three replications

affected the APX activity negatively in Chandler (Fig. 3II). Regarding the NaCl treatments for 30 days, the activity of APX was sharply increased by 17.0 mM NaCl treatment and then decreased to the same level with control by 34 mM NaCl treatment in Camarosa. Similar APX activity was observed in Tioga, while only that of APX activity was sharply increased by 8.5 mM NaCl treatment. However, APX activity of Chandler increased linearly reaching a

A decrease in gs under saline condition was reported in some plants such as muskmelon (Carvajal et al. 1998), pepper (Martinez-Ballesta et al. 2004), and cowpea (Wilson et al. 2006), E generally tend to decline with increasing salinity in almost all plants (Robinson et al. 1997). In contrast to these evidences, addition of NaCl to the growth medium caused a reduction only in gs of Camarosa. Salinity up to 34.0 mM NaCl did not have any influence on gs of Tioga and Chandler. The time course of gs of strawberry plants in recent work either remained almost unchanged or slightly increased in all the NaCl treatments in Tioga and Chandler, which is similar to Es (Fig. 1). However in Camarosa, a significant reduction in gs was seen particularly on the 30th day of the salt treatments,

Fig. 3 The activity of Catalase-CAT (I) and Ascorbate peroxidase-APX (II) of three strawberry cultivars, Camarosa (a), Tioga (b), and Chandler (c) under 0, 8.5, 17.0, and 34.0 mM NaCl treatments during 15 and 30 days. Values indicate average ± SD of three replications

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Fig. 4 The activity of Glutathion reductase-GR of three strawberry cultivars, Camarosa (a), Tioga (b), and Chandler (c) under 0, 8.5, 17.0, and 34.0 mM NaCl treatments during 15 and 30 days. Values indicate average ± SD of three replications

which is parallel to E. This may be correlated with the ability of osmotic regulation of Camarosa. That NaCl treatments caused osmotic effects in Camarosa and possess the ability to bring about osmotic regulation to tolerate the salinity (Turhan and Eris 2004) is well documented in the previous study. Reactive oxygen species generation during salt stress can result from electron leakage toward oxygen, caused by defected electron flow due to altered membrane ionic interactions (Borsani et al. 2001). LT50 based on the electrolyte leakage directly correlated with the cell membrane stability. Thus, higher membrane stability could be correlated with abiotic stress tolerance (Premachandra et al. 1992). In the present study, short period of NaCl applications (15 days) in all the cultivars showed higher LT50 than longer period (30 days) (Fig. 2). In other words, longer period of salt treatment had more deleterious effect on the cell membrane than short period of salt treatment related to tolerance. Recent data also indicated that Camarosa and Tioga cultivars had almost the same LT50 values (*32 and *29 mM NaCl in the 15 and 30-day periods, respectively) while Chandler had significantly lower LT50 in both 15 and 30-day periods of NaCl treatments (*27 and *21 mM NaCl, respectively) (Fig. 2). According to the results of our previous work (Gulen et al. 2006), Camarosa and Tioga leaf tissues had less electrolyte leakage than Chandler, which is symptomatic of cellular damage. In addition, according to morphologic properties

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and ionic composition besides peroxidase enzyme activity and profiles of the cultivars, Camarosa and Tioga are reported more salt-tolerant than Chandler (Turhan 2002; Gulen et al. 2006). This hypothesis of the previous work was confirmed by the recent results showing the LT50 values of the cultivars. It is known that biochemical mechanism underlying salt tolerance such as antioxidative enzyme activity is more a relevant criterion for improving salt tolerance in crops even in cultivars (Dionisio-Sese and Tobita 1998; Morant-Avice et al. 1998; Ashraf and O’Leary 1999; Arshi et al. 2002). In strawberry, as well as in some other crops, response of the cultivars to salt stress was well-documented using agronomic and physiological characteristics, content of leaf total protein and PRX activity (Barroso and Alvarez 1997; Turhan 2002; Turhan and Eris 2004; 2005; Gulen et al. 2006). Camarosa, Tioga, and Chandler cultivars showed a different trend of CAT activity from each other. The activities of CAT remained almost unchanged and slightly increased in 15 and 30 days of salt treatments, respectively, in Camarosa, while it decreased in both 15 and 30 days of salt treatments in Tioga (Fig. 3-I). Similarly Cavalcanti et al. (2004) reported that CAT activity decreased significantly in leaves of cowpea under salinity stress. However, in Chandler, CAT activity remained almost unchanged in both 15 and 30 days of salt treatments. On the other hand, it was reported that salt stress had no significant effect on CAT activity in the salt-tolerant maize leaves, but it was reduced significantly in the salt-sensitive genotype (Neto et al. 2006). Gueta-Dahan et al. (1997) indicated that acquisition of salt tolerance might also be a consequence of improving resistance to salt stress, via increased APX activity. APX activity had a key role in the citrus response to salt stress in the comparison of the activities of antioxidant enzymes in salt-sensitive and salt-tolerant citrus cells (Gueta-Dahan et al.1997). Increased activity of APX in salt-adapted cells seems to be more important for their acquiring of salt tolerance, while GR activity decreases during salt adaptation. In strawberry, NaCl treatments for15 days almost did not change the APX activity (Fig. 3-II). However in salt treatments for 30 days, APX activity sharply increased up to *9 lmol in 17 and 8.5-mM NaCl treatments in Camarosa and Tioga, respectively. Moreover, the activity of APX linearly increased up to 6 lmol based on the NaCl treatments in Chandler. On the other hand, GR activity (Fig. 4) remained almost unchanged in all the treatments of all the cultivars except Camarosa in contrast to citrus plant (Gueta-Dahan et al.1997). Moreover, Camarosa demonstrated a sharp increase in GR activity induced by highNaCl concentrations (17 and 34 mM) applied during 30 days to reduce to NaCl induced damages.


In conclusion, the LT50s (Fig. 2) of the cultivars were lower in 30-day period treatments than in 15-day period treatments; in other words, since the cellular damages induced by NaCl were higher in salt treatments for 30 days, the activity of antioxidative enzymes was not effective to reduce the cellular damage in spite of having higher activity. Therefore, NaCl treatments for 30 days might not cause salt adaptation in strawberry leaves. Similar to our findings, Elkahoui et al. (2005) reported a correlation between antioxidant activities and cellular damage provoked by NaCl. They reported that increase of antioxidant activities could not stop the deleterious effects of salt, but reduced stress severity thus allowing cell growth to occur. On the other hand, Cavalcanti et al. (2004) indicated that PRX, SOD, and CAT activities of cowpea leaves were not effective in protecting the leaf tissues from salt-induced damage. The data presented here suggested that although APX and GR could be used in the classification of the strawberry cultivars according to their salt tolerance, CAT activity could not be used as an indicator. To summarize, long period of salt treatments (30 days) reduced the LT50 of the cultivars particularly in the treatments of higher NaCl concentration, which means none of the cultivars showed a salt adaptation during the experiment. The data of the present study confirmed and approved our previous reports (Turhan 2002; Turhan and Eris 2004, 2005; Gulen et al. 2006), which was concluded a significant cultivar dependent response to salt stress in strawberry. Consequently, control of the stomatal behavior as an indication of osmotic adjustment, the higher LT50 as an indication of lesser degree of membrane damage and higher constitutive activity of antioxidant enzymes made Camarosa and Tioga relatively high salt-tolerant cultivars.

References Arora R, Wisniewski ME, Scorza R (1992) Cold acclimation in genetically related (sibling) deciduous and evergreen peach (Prunus persica L. Batsch). I Seasonal changes in cold hardiness and polypeptides of bark and xylem tissues. Plant Physiol 99:1562–1568 Arshi A, Abdin MZ, Iqbal M (2002) Growth and metabolism of senna as affected by salt stress. Biol Plant 45:295–298 Ashraf M, O’Leary WJ (1999) Changes in soluble proteins in spring wheat stressed with sodium chloride. Biol Plant 42:113–117 Awang YB, Atherton JG, Taylor AJ (1993) Salinity effects on strawberry plants grown in rockwool. I. Growth and leaf water relations. J Hortic Sci 68:783–790 Barroso MCM, Alvarez CE (1997) Toxicity symptoms and tolerance of strawberry to salinity in the irrigation water. Sci Hortic 71:177–188 Bohnert HJ, Nelson DE, Jensen RG (1995) Adaptations to environmental stresses. Plant Cell 7:1099–1111 Borsani O, Valpuesta V, Botella MA (2001) Evidence for a role of salicyclic acid in the oxidative damage generated by NaCl and

207 osmotic stress in Arabidopsis seedlings. Plant Physiol 126:1024– 1030 Cakmak I, Marschner H (1992) Magnesium deficiency and high-light intensity enhance activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase in bean leaves. Plant Physiol 98:1222–1227 Carvajal MF, del Amor M, Fernandez-Ballester G, Martinez V, Cerda A (1998) Time course of solute accumulation and water relations in muskmelon plants exposed to salt during different growth stages. Plant Sci 138:103–112 Cavalcanti FR, Oliveira JTA, Martins-Miranda AS, Viegas RA, Silveira JAG (2004) Superoxide dismutase, catalase and peroxidase activities do not confer protection against oxidative damage in salt-stressed cowpea leaves. New Phytol 163:563– 571 Chaparzadeh N, D’Amico ML, Nejad RAK, Izoo R, Navari Izzo F (2004) Antioxidative responses of Calendula officinalis under salinity conditions. Plant Physiol Biochem 42:695–701 Chattopadhayay MK, Tiwari BS, Chattopadhayay G, Bose A, Sengupta DN, Bharati G (2002) Protective role of exogenous polyamines on salinity stressed rice (Oryza sativa) plants. Physiol Plant 116:192–199 Chaves MM, Maroco JP, Pereira JS (2003) Understanding plant responses to drought: from genes to the whole plant. Funct Plant Biol 30:239–264 del Rio LA, Corpas FJ, Sandalio LM, Palme JM, Gomez M, Barroso JB (2002) Reactive oxygen species, antioxidant systems and nitric oxide in peroxisomes. J Exp Bot 53:1255–1272 Dionisio-Sese ML, Tobita S (1998) Antioxidant responses of rice seedlings to salinity stress. Plant Sci 135:1–9 Elkahoui S, Hernandez JA, Abdelly G, Ghrir R, Limam F (2005) Effects of salt on lipid peroxidation and antioxidant enzyme activities of Catharanthus roseus suspension cells. Plant Sci 168:607–613 Faltin Z, Camoin L, Ben-Hayyim G, Perl A, Beeor-Tzahar T, Strosberg AD, Holland D, Eshdat Y (1998) Cystein is the presumed catalytic residue of Citrus sinensis phospholipids hydroxyperoxide glutathione peroxidase over-expressed under salt stress. Physiol Plant 104:741–746 Foyer CH, Noctor G (2005) Oxidant and antioxidant signaling in plants: a re-evaluation of the concept of oxidative stress in a physiological context. Plant Cell Environ 28:1056–1071 Foyer CH, Lelandais M, Kunert KJ (1994) Photooxidative stress in plants. Physiol Plant 92:696–717 Greenway H, Munns R (1980) Mechanisms of salt tolerance in nonhalophytes. Annu Rev Plant Physiol 31:149–190 Grumet R, Isleib TG, Hanson AD (1985) Genetic control of glycinebetaine level in barley. Crop Sci 25:618–622 Gueta-Dahan Y, Yaniv Y, Zilinskas BA, Ben-Hayyim G (1997) Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in citrus. Planta 203:460–469 Gulen H, Turhan E, Eris A (2006) Changes in peroxidase activities and soluble proteins in strawberry cultivars under salt-stress. Acta Physiol Plant 28:109–116 Martinez-Ballesta MC, Martinez V, Carvajal M (2004) Osmotic adjustment, water relations and gas exchange in pepper plants grown under NaCl or KCl. Environ Exp Bot 52:161–174 Mc Kersie BD, Leshem YY (1994) Stress and stress coping in cultivated plants. Kluwer, Dordrecht, The Netherlands, 256 pp Meloni DA, Oliva MA, Martinez CA, Cambraia J (2003) Phytosynthesis and activity of superoxide dismutase, peroxidase and glutathione reductase in cotton under salt stress. Environ Exp Bot 49:69–76 Mittler R (2002) Oxidative stress, antioxidants and stress tolerance. Trends Plant Sci 7:405–410

123

208 Moran JF, Becana M, Ittrbe-Ormaetxe I, Frechilla S, Klucas RV, Aparicio-Tejo P (1994) Drought induces oxidative stress in pea plants. Planta 194:346–352 Morant-Avice A, Pradier E, Houchi R (1998) Osmotic adjustment in triticales grown in presence of NaCl. Biol Plant 41:227–234 Nakano Y, Asada K (1980) Spinach chloroplasts scavenge hydrogen peroxide on illumination. Plant Cell Physiol 21:1295–1307 Neill S, Desikan R, Hancock J (2002) Hydrogen peroxide signalling. Curr Opin Plant Biol 5:388–395 Neto ADA, Prisco JT, Ene´as-Filho J, Abreu CEB, Gomes-Filho E (2006) Effect of salt stress on antioxidative enzymes and lipid peroxidation in leaves and roots of salt-tolerant and salt-sensitive maize genotypes. Environ Exp Bot 56:87–94 Noctor G, Foyer CH (1998) Ascorbate and glutathione: keeping active oxygen under control. Annu Rev Plant Physiol Plant Mol Biol 49:249–279 Premachandra GS, Saneoka H, Fujita K, Ogata S (1992) Leaf water relations, osmotic adjustment, cell membrane stability, epicuticular wax load and growth as affected by increasing water deficits in Sorghum. J Exp Bot 43:1569–1576 Qasim M, Ashraf M, Ashraf MY, Rehman SU, Rha ES (2003) Saltinduced changes in two canola cultivars differing in salt tolerance. Biol Plant 46:629–632 Rao MV, Paliyath G, Ormrod DP (1996) Ultraviolet-B- and ozoneinduced biochemical changes in antioxidant enzymes of Arabidopsis thaliana. Plant Physiol 110:125–136 Robinson MF, Very AA, Sanders D, Mansfield TA (1997) How can stomata contribute to salt tolerance? Ann Bot 80:387–393 Rout NP, Shaw BP (2001) Salt tolerance in aquatic macrophytes: possible involment of antioxidative enzymes. Plant Sci 160:415– 423 Sairam RK, Veerabhadra Rao K, Srivastava GC (2002) Differential response of wheat genotypes to long term salinity stress in

123

Acta Physiol Plant (2008) 30:201–208 relation to oxidative stress, antioxidant activity and osmolyte concentration. Plant Sci 163:1037–1046 Shalata A, Tal M (1998) The effects of salt stress on lipid peroxidation and antioxidants in the leaf of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii. Physiol Plant 104:169–174 Shalata A, Mittova V, Volokita M, Guy M, Tal M (2001) Response of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii to salt-dependent oxidative stress: the root antioxidative system. Physiol Plant 112:487–494 Sudhakar C, Lakshmi A, Giridarakumar S (2001) Changes in the antioxidant enzyme efficacy in two high yielding genotypes of mulberry (Morus alba L.) under NaCl salinity. Plant Sci 161: 613–619 Tsai YC, Chwan YH, Liu LF, Kao CH (2005) Expression of ascorbate peroxidase and glutathione reductase in roots of rice seedlings in response to NaCl and H2O2. J Plant Physiol 162:291–299 Turhan E (2002) Researches on salt resistance physiology of strawberries growth in different media. (In Turkish: Farklı ortamlarda yetis¸ tirilen c¸ileklerin tuza dayanıklılık fizyolojileri u¨zerine aras¸ tırmalar.) Ph.D. thesis, Uludag Univ Inst Natural Sci, Bursa, p 195 Turhan E, Eris A (2004) Effects of sodium chloride applications and different growth media on ionic composition in strawberry plant. J Plant Nutr 27:1653–1665 Turhan E, Eris A (2005) Changes of micronutrients, dry weight, and chlorophyll contents in strawberry plants under salt stress conditions. Commun Soil Sci Plant Anal 39:1021–1028 Wilson C, Liu X, Lesch SM, Suarez DL (2006) Growth response of major USA cowpea cultivars II. Effect of salinity on leaf gas exchange. Plant Sci 170:1095–1101 Zhu JK (2000) Genetic analysis of plant salt tolerance using Arabidopsis. Plant Physiol 124:941–948