Effect Of Nacl On Physiological Parameters Of Rice Biology Essay

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Rice plants were exposed to increasing concentrations (0, 25, 50, 100 and 200 mM) of NaCl. Fresh weight, dry weight of the treated seedlings decreased. Decreasing of plant growth depended on lowering of available CO2 which was caused by stomatal closure and also on the additive effects of leaf water and osmotic potential, relative leaf water content, and biochemical constituents such as photosynthetic pigments, soluble carbohydrates, and proteins. increasing concentrations of NaCl resulted in increase and decrease of Na+ and K+ ions respectively. NaCl salinity caused for increasing both peroxide content and lipid peroxidation. Seedlings which recovered for 24 h showed lower peroxide and MDA content.

Keywords: Rice, NaCl, Salinity


Salinity is becoming a serious problem in several parts of the world. The saline area is three times larger than land used for agriculture [1]. Salinity is one of the key environmental factors that limit crop growth and agricultural productivity. Total area under salinity is about 953 million ha covering about 8 per cent of the land surface [2-3]. Several physiological pathways, i.e., photosynthesis, respiration, nitrogen fixation and carbohydrate metabolism have been observed to be affected by high salinity [4].

Rice (Oryza sativa L.) is one of the most important crops in the world and is the primary stable food for over two billion people. With the rapid growth in population consuming rice and the deteriorating soil and water quality around the globe, there is an urgent need to understand the response of this important crop towards these environmental abuses. With the ultimate goal to raise rice plant with better suitability towards changing environmental inputs, intensive efforts are on worldwide employing physiological, biochemical and molecular tools to perform this task. Abiotic stress is the main factor negatively affecting crop growth and productivity worldwide. Rice plants are relatively susceptible to soil salinity as an abiotic stress [5-6].

Salinity alters a wide array of metabolic processes in growing plants and induces changes in contents and activities of many enzymes [7-10]. As a consequence of ion imbalance and hyperosmotic stresses, which are primary effects of salt stress, secondary stresses such as oxidative damage may occur. Limited CO2 fixation due to stress conditions leads to a decrease in carbon reduction by the Calvin cycle and decrease in oxidized NADP+ to serve as an electron acceptor in photosynthesis. When ferrodoxin is over reduced during photosynthetic electron transfer, electrons may be transferred from PSI to oxygen to form superoxide radicals (O2˙) by the process called Mehler reaction, which triggers chain reactions that generate more aggressive reactive oxygen species (ROS). Any imbalance in the cellular redox homeostasis can be called as an oxidative stress and results in the production of ROS because of the univalent reduction of oxygen. Salt stress increases the rate of production of ROS such as superoxide radical (O2¯), hydrogen peroxide (H2O2), hydroxyl radical (˙OH), alkoxyl radical (RO˙) and singlet oxygen (1O2) formation via enhanced leakage of electron to oxygen. It is already known that these cytotoxic ROS, which are also generated during metabolic processes in the mitochondria and peroxisomes, can destroy normal metabolism through oxidative damage of lipids, proteins, and nucleic acids [11-12]. Lipid peroxidation, induced by free radicals, is also important in membrane deterioration [13-14].

Salinity appears to affect two plant processes: water relations and ionic relations. During initial exposure to salinity, plants experience water stress, which in turn reduces leaf expansion. During long-term exposure to salinity, plants experience ionic stress, which can lead to premature senescence of adult leaves. The problem is compounded by mineral deficiencies (Zn, P) and toxicities (Fe, Al, organic acids), submergence, deep water and drought [15]. Thus the photosynthetic area available to support continued growth is reduced [16]. Reduced photosynthesis with increasing salinity is attributed to either stomatal closure, leading to a reduction in intracellular CO2 partial pressure, or non-stomatal factors [17]. There are evidences showing that salinity changes photosynthetic parameters, including osmotic and leaf water potential, transpiration rate, leaf temperature, and relative leaf water content (RWC). Salt also affects photosynthetic components such as enzymes, chlorophylls, and carotenoids. Changes in these parameters depend on the severity and duration of stress [18] and on plant species [9].

According to Yeo and Flowers chlorophyll content of salt stressed rice can be described as a function of the leafs sodium content [19]. Sodium chloride accumulation in the leaf laminae reduces net photosynthesis and growth [20]. Sodium uptake to the rice plant is greater under low than under high air humidity [21], The response of transpiration to salt stress under different air humidity levels differs among rice cultivars according to their overall resistance to salinity and their resistance strategy [22], and also depends on the external salt concentration. The relative leaf chlorophyll content of non stressed field grown rice is lower than moderate salt stressed plants. [23]. This effect could be due to a reduction in leaf area, which has been discussed as an adaptive strategy of salt-stressed plants to reduce transpiration and thus the uptake of sodium into leaves [5]. The nitrogen concentration per unit leaf area in salt-stressed plants, however, will be higher than in non-stressed plants and thus the net-photosynthesis can also be expected to be higher, at least as long as the sodium accumulation in the leaf blades stays within the limits of the plants tissue tolerance to sodium

Starch accumulates in leaves as a temporary reserve form of carbon and is the principal component of dry mass accumulated in mature leaves, whereas sucrose is transported to different organs where it is used by plants. The last step in the photosynthetic production of sucrose is catalysed by the sucrose phosphate synthase (SPS) [24-25] which converts hexose phosphates to sucrose. Prolonged water stress which limited photosynthesis led also to loss of SPS activity, e.g., in leaves of Phaseolus vulgaris [26], whereas in rapidly stressed spinach leaves a stimulation in SPS activity was observed [27]. A change in kinetic properties and the appearance of a new form of SPS has been noticed in potato tubers after low temperature treatment [25]. Sucrose breakdown inside the tissues is accomplished by acid invertase or sucrose synthase [28]. Metabolism of sugars is adversely affected in plants growing under saline conditions [10].

The present investigation was undertaken to examine the changes in the content of starch and sugars, Na+ and K+ concentrations, relative water content (RWC) photochemical efficiency and electron transfer rate and the amount of photosynthetic pigment and protein, as well as growth parameters under various concentration of NaCl.



Rice seeds (Oryza sativa cv. Tarom Azmoon.) were surface sterilized with 1% sodium hypochlorite and washed thrice thoroughly in distilled water and then imbibed in water for 48 h at room temperature. The soaked seeds were then put in plastic pots filled with vermiculite saturated with Hoagland nutrient solution [29]. After germination seedlings were grown in the pots filled with vermiculite saturated either with Hoagland nutrient solution (control) or nutrient solution supplemented with 0, 25, 50, 100 and 200 mM NaCl for 8 days. The solutions renewed after every 2 days. Seedlings were grown in a growth chamber under controlled environmental conditions with relative humidity of 70-85%, temperature 24 ± 2˚C and a photoperiod of 16 h in a photosynthetic photon flux density of 250-350 µmol m-2 s-1.


The length of each seedling was measured after 13 days (the seeds had been soaked in water for 5 days prior to the sowing). The fresh weight of each culm with its leaves was taken, and then the samples were oven-dried at 80°C and the dry weight was taken.

To determine relative water content (RWC), four plants from each treatment were randomly selected and the method described by Whetherley and Turner was fallowed [30-31]. About 0.1 g leaf sample was cut into smaller pieces and weighed to determine initial weight (Wi). The leaf samples were then floated in freshly de-ionized water for 12 h and weighed thereafter to determine fully turgid weight (Wf). The sample was oven-dried at 80ËšC for 3 days and the dry weight was obtained (Wd). The relative water content (RWC) was determined using the following formula: RWC = (Wi - Wd) (Wf - Wd)-1 ï‚´ 100.


For sugar extraction samples (1 g) were ground with liquid nitrogen, and the sample powder was extracted twice with 5 ml of 80% (v/v) ethanol at 80˚C for 5 min. After centrifugation at 3000·g for 5 min, samples were washed twice with H2O at room temperature. Each sample was resuspended with 3 ml H2O and boiled for 2 h. Total sugars were estimated calorimetrically using phenol sulphuric acid method described by Dubois [32] and reducing sugars by Nelson-Somogyi method as described by Oser [33].


Fresh samples of leaves were analyzed for pigment contents. Photosynthetic pigments were extracted with 80% acetone as described by Brouers et al. [34]. The salt treated and untreated leaves (1.0-1.5 g) were ground to a fine powder in liquid nitrogen using a mortar and pestle. The pigments were extracted with 3 cm3 of cold 80 % acetone. The acetone extracts were centrifuged at 30 000Ã-g for 10 min and the resulting pellet was extracted with cold 80 % acetone. This operation was repeated 3 times. The successive supernatants were pooled and clarified by centrifugation at 40 000g for 5 min. The absorbance spectra of the extracts were measured and the total amount of pigments was determined with equations recommended by Brouers et al. [34].


Protein extracts of plant material prepared by a method slightly modified from the one described by Böddi et al. [35]. The leaves were ground at 95°C in an extraction buffer of 10% (v/v) glycerol, 4% (w/v) sodium dodecyl sulphate (SDS), 0.3 M dithiothreitol, 0.001% bromophenol blue and 250 mM Tris-HCl, pH 6.8. The proteins were quantified by a colorimetric assay for protein determination using the Bio-Rad DC Protein Assay kit based on the well-documented Lowry assay (Bio-Rad, Richmond, CA). The absorption values were read at 750 nm with a Perkin Elmer Lambda 900 UV/VIS spectrophotometer.


The Maximal photochemical efficiency of PS2 (Fv/Fm) was determined by chlorophyll fluorescence, measured with a Chlorophyll Fluorometer (PAM-2000; Heinz-Walz, Effeltrich, Germany) according to the manufacturer's instructions and the experimental protocol of Genty et al. [36], was basically used in this experiment. Chlorophyll fluorescence was measured in dark adapted leaves. The minimal fluorescence level (F0) in the dark adapted state was measured by the measuring modulated light, which was sufficiently low (<0.1 μmol m-2 s-1) not to induce any significant variable change in fluorescence. The maximal fluorescence level (Fm) was measured by a 0.8 s saturating pulse at 8000 μmol (photon) m-2 s-1. The measurements of F0 were recorded with the measuring beam set to a frequency of 0.6 kHz, whereas Fm measurements were performed with the measuring beam automatically switching to 20 kHz during the saturating flash. The maximal quantum yield of PSII photochemistry (Fv/Fm) and the electron transport rate (ETR) was calculated using fluorescence parameters determined in leaves.


Tissue was homogenized in 5% trichloroacetic acid (TCA) and the homogenate was used for the determination of hydrogen peroxide (H2O2) levels by method described by Sagisaka [37]. The reaction mixture contained TCA (50%), ferrous ammonium sulphate (10 mM), potassium thiocyanide (2.5 M) and plant extract and the absorbance was read at 480 nm. The level of lipid peroxidation in the tissues was determined as 2-thiobarbituric acid (TBA) reactive metabolites chiefly malondialdehyde (MDA) accumulation as described by Heath and Packer [38]. Tissue (0.2 g) was extracted in 5 ml TBA (0.25%) made in 10% trichloroacetic acid (TCA). Extract was heated at 95°C for 30 min and then quickly cooled in ice. After centrifugation at 10,000g for 10 min, the absorbance of the supernatant was measured at 532 nm. Correction of nonspecific turbidity was made by substracting the absorbance value taken at 600 nm. The level of lipid peroxidation is expressed as µmol of MDA formed


Elongation studies showed that salt stress had a significant effect on the lengths of seedlings (Fig. 1). Seedling grown in the nutrient solution supplied with 25 and 50 mM extra salt were shorter, 82.5% and 61.2% of the control respectively. They could, however, develop their secondary leaves. Seedling grown in the nutrient solution supplied with 100 and 200 mM extra salt were much shorter, 49.3% and 10% of the control respectively. They could not even develop their secondary leaves. Seedlings could hardly growth at salinity higher than 200 mM. (Fig. 1A).

Salt stress had reducing effect on leaf area of seedlings. The leaf areas of salt treated seedlings with 0, 25, 50, 100 and 200 mM salt decreased to 79%, 40.7%, 28.7% and 3% of untreated seedlings, respectively (Fig. 1B). In addition, increased salinity level caused reduction in leaf relative water contents (RWC) was reduced from 71% in the control plants to 67%, 64%, 60% and 58% in the plants treated with 25, 50, 100 and 200 mM salt, respectively (Table 1).

The weight of plants has been affected by salt stress. Both fresh and dry weights of culms with leaves were reduced with increasing salinity. Fresh weight of seedlings reduced to 89.7%, 84.6%, 69.6% and 42.2% of non treated ones when grown in Hoagland solution supplied with 25, 50, 100 and 200 mM salt, respectively. In addition dry weight of seedlings treated with 25, 50, 100 and 200 mM salt, decreased to 91.5%, 86.3%, 76.6% and 41.2%, respectively (Fig. 2).

Carbohydrate composition of seedlings was altered by salinity stress. The amounts of sugars were affected by different concentration of NaCl. Decrease of total sugar content was remarkable at higher concentrations. Total sugar in the treated seedlings reduced to 45.4%. Reducing and non-reducing sugars both exhibited a significantly (P<0.001) decreasing trend with increasing salinity and decreased to 46.5% and 43.6% in treated seedlings with 200 mM salt (Table 1).

The effect of NaCl on the photosynthetic pigments, protein, and soluble carbohydrate contents in the leaves were examined. Chlorophyll and carotenoid contents decreased significantly in the salt treated seedlings (Fig. 3). As figure 3A shows chlorophyll b was more sensitive than chlorophyll a. in the treated seedlings with 200 mM salt. Chlorophyll a and b decreased to 44.1% and 27.3% of control, respectively. The ratio increased from 1.40 in the control to 2.35 at the highest salinity tested (Fig. 3A). Salinity had also a significant effect on carotenoid contents. Carotenoid contents in seedlings treated with 25, 50, 100 and 200 mM were 78.7%, 69.0%, 60.0% and 39.3% of control plants, respectively (Fig. 3B).

The changes in PSII photochemistry were studied in dark adapted leaves by using the Mini PAM fluorometer. As Figure. 4A shows no significant changes occurred in the maximal quantum yield of PSII (Fv/Fm) measured in the dark adapted leaves between control plants and salt-stressed plants in both species. The measurements of ETR also observed no significant changes in salt treated seedlings (Fig. 4B).

Total protein has also been examined. The soluble protein contents decreased with increasing salinity. Decreasing the total protein was not intensive (P>0.2 and P> 0.05, respectively) when seedlings treated with 25 and 50 mM salt. Addition of salt to 100 mM and specially 200 mM resulted in more intensive decrease (P<0.05) of total protein (Fig. 5).

Increase in NaCl concentrations showed a uniform increase in Na+ ion and decrease in K+ ion in stressed seedlings. Upon removing NaCl, there was a decrease in content of sodium ions and an increase in potassium ion content. The Na+/K+ ratio increased significantly with the increasing NaCl concentrations. Increasing the Na+/K+ ratio in the seedlings which recovered for 24 h, however, was more gradually (Fig. 6).

The damage by NaCl to cellular membranes due to lipid peroxidation as indicated by the accumulation of the malondialdehyde (MDA) levels and the results showed that MDA level was significantly increased with rising NaCl concentrations. Recovered samples showed lower content of MDA (Fig. 7). Treatment showed significant increase in H2O2 content, however, recovered roots showed lower content of H2O2 (Fig. 7).


One aim of this study was to examine whether salinity influences the seedlings morphological and biochemical properties. Rice was chosen for this investigation because it has not been explored as much as for example wheat and barley [39] . Rice is also one of the world's major crops, indeed a majority of the human population need rice for their daily food intake [40].

The results of present study demonstrate growth reduction of seedlings when expose to increased in salinity level. The height, leaf area and were decreased (Fig. 1). This might partially be attributed to the lower leaf water potential and a reduction in relative leaf water content (Table 1), which resulted in loss of turgor, which in turn causes stomatal closure and limits CO2 assimilation and reduced photosynthetic rate. This result agrees with the findings of Pérez-Alfonsa, Sibole, Sultana and Pattanagul and Thitisaksakul [41-44]. A marked growth reduction was also reported earlier to rice seedlings exposed to salt stress [45].The results showed a decrease in the RWC in salt treated seedlings (Table 1). It is known that salt stress affects both leaf growth and water status [7, 46]. The osmotic effect resulting from soil salinity may cause disturbances in the water balance of the plant and inhibiting growth as well as provoking stomatal closure and reducing photosynthesis [47]. Plants respond by means of osmotic adjustment, normally by increasing the concentrations of Na+ and Cl¯ in their tissues, although such accumulation of inorganic ions may produce important toxic effects and cell damage and inactivate both photosynthetic and respiratory electron transport. This limited osmotic adjustment was not sufficient to avoid water stress in the treated plants, and thus there was a decrease in the roots water content after salt stress. Wilson et al. (1989) indicated that osmotic adjustment accounted for decreases in the fresh weight/dry weight ratio, increases in apoplastic water content and direct solute accumulation [48].

This study shows that photosynthetic pigments, sugars and protein concentrations of leaves were reduced by salinity. A decrease in Chl and tetrapyrroles content with the increase of NaCl was also reported by Khan [49]. The results obtained in this study are in agreement with those of Azooz et al. [50], Dager et al. [51].and Jaleel et al.[52]. A decrease in chlorophyll concentration in salinized plants could be attributed to increased activity of the chlorophyll-degrading enzyme chlorophyllase [53]. Ion accumulation in leaves also adversely affected chlorophyll concentration [19]. The decrease in carotenoids under salt stress leads to degradation of β-carotene and formation of zeaxanthins, which are apparently involved in protection against photoinhibition [54]. As salinity adversely influenced the photosynthetic process, photosynthetic production (e.g. sugar) was inhibited. Kerepesi et al. and Sultana et al. also found that sugar contents of leaves decreased in seedlings under NaCl stress [41, 55].

The increase in Na+ ion content and decrease in K+ ion uptake disturbs ionic imbalance as observed in most species exposed to salt stress. Due to high uptake and accumulation of Na+ and antagonastically low uptake, translocation and accumulation of K+ and also enhanced K+ efflux under salt stress could suppress growth by decreasing the capacity of osmotic adjustment and turgor maintenance or by inhibiting metabolic activities. The diminution of K+ concentration in tissue may also be due to direct competition between K+ and Na+ at plasma membrane, inhibition of Na+ on K+ transport process in xylem tissues and/or Na+ induced K+ efflux from the roots. High Na+ accumulation in salt-sensitive foxtail millet cultivar, in tomato roots and rice roots have been reported to result in an enhanced membrane damage, electrolyte leakage and oxidative damage [13].

The maximum quantum yield of PSII; Fv/Fm is equivalent to the intrinsic photochemical efficiency of PSII. A decrease in this ratio is closely associated with exposure to high light intensity [56]. Fv/Fm measurement of the salt treated seedling with different salt concentrations showed no significant changes compare to control. They were all in the same range 0.81-0.83 (Fig. 4). Values between 0.8-0.85 are usually considered as non-stressed plants. That means Fv/Fm is not sensitive enough to salt stress.

These data are, however, opposite to another report where general decrease of Fv/Fm is detected with the increase of salt concentration exposed to plants [57]. The decrease in Fv/Fm was expected to be an indicator to evaluate the damage in chloroplasts, especially in thylakoid membranes, under salinity [58].

ETR can be an indicator to evaluate the photosynthetic activity of plant leaves [59]. ETR is the actual rate of electron flow, is derived from the quantum yield of PSII and considered as one of the photosynthetic parameters which show the efficiency of photosynthesis [60]. There is a relationships between the electron transport rate (ETR) measured by pulse amplitude modulated (PAM) fluorometer and the rate of O2 production and C fixation. A remarkable linear relationship was reported between the rate of O2 production and C fixation to ETR [61]. Thus changes in ETR shows that O2 production and C fixation has been affected by salinity. Measurements did not, however, show any significant ETR changes on used rice varieties affected by salinity.

Cellular membranes damaged by NaCl due to lipid peroxidation. The results showed that MDA level was significantly increased with rising NaCl concentrations. Salt treatment seedlings also showed significant increase in H2O2 content. There are reports that salinity disrupts membrane permeability is by peroxidation of the lipid membrane. Salinity also increases the content of H2O2 and induces oxidative stress in plant tissues [13]. Membrane injury under salt stress is related to increased production of highly toxic reactive oxygen species [46]. Lipid peroxidation measured as the amount of MDA is produced when polyunsaturated fatty acids in the membrane undergo oxidation by the accumulation of free oxygen radicals. Lipid peroxidation is ascribed to oxidative damage and is often used as an indicator of increased damage [46, 62-63]. The post stress recovered seedlings showed lesser accumulation of MDA compared to stressed seedlings showing the ability of the plants to recover to some extend the damage caused during the stressed conditions.


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Table legend:

Table 1 Effect of different concentrations of NaCl on total sugar (TS) (mg g-1 FW), reducing sugar (RS) (mg g-1), non-reducing sugar (NRS) (mg g-1) and relative leaf water content (RWC) (%) in the leaves of rice.


Figure 1. Picture (A) and diagram (B) of changes in height and leaf area of rice seedlings subjected to NaCl salinity (0, 25, 50, 100 and 200 mM) stress. Data presented on panel B are mean ± SE (n = 3).

Figure 2. Fresh (FW) and dry weights (DW) of rice seedlings subjected to NaCl salinity (0, 25, 50, 100, 200 mM) stress. Data presented are mean ± SE (n = 3).

Figure 3. Effects of NaCl on chlorophyll (A) and carotenoid (B) contents of rice leaves subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM). Vertical bars indicate mean ± SE (n = 3).

Figure 4. Optimum quantum yield (Fv/Fm) (A) and ETR (B) of leaves of 12-day old rice. Plants were fed by solution containing different concentrations of NaCl (0, 25, 50, 100, 200 mM) Leaves were placed in the dark adapted state for 30 min allowing the reaction centers to be re-oxidized. Fv/Fm ratio is the average from five replicates. Vertical bars indicate mean ± SE (n = 3).

Figure 5. Effects of NaCl on total protein contents of rice leaves subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM). Vertical bars indicate mean ± SE (n = 3).

Figure 6. Changes in the concentrations of sodium (Na+), potassium (K+) and the Na+/K+ ratio in rice plants subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM) (A) and after 24 h recovery in nutrient solution. Data presented are mean ± SE (n = 3).

Figure 7. Changes in malondialdehyde (MDA) (A) and H2O2 (B) levels in rice seedlings subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM) (S) and after 24 h recovery in nutrient solution (R). Data presented are mean ± SE (n = 3).


Table 1 Effect of different concentrations of NaCl on total sugar (TS) (mg g-1 FW), reducing sugar (RS) (mg g-1), non-reducing sugar (NRS) (mg g-1) and relative leaf water content (RWC) (%) in the leaves of rice.


0 96.85 ± 2.26 58.24 ± 2.06 38.56 ± 2.19 71.05 ± 2.08

25 90.04 ± 2.31 55.22 ± 2.24 35.25 ± 1.90 67.10 ± 1.39

50 74.38 ± 1.70 47.20 ± 1.52 28.00 ± 2.31 64.22 ± 1.42

100 57.19 ± 3.09 36.62 ± 2.28 20.78 ± 3.10 60.39 ± 1.37

200 44.13 ± 2.13 26.98 ± 1.44 17.33 ± 1.96 58.08 ± 1.37


Figure 1. Picture (A) and diagram (B) of changes in height and leaf area of rice seedlings subjected to NaCl salinity (0, 25, 50, 100 and 200 mM) stress. Data presented on panel B are mean ± SE (n = 3).

Figure 2. Fresh (FW) and dry weights (DW) of rice seedlings subjected to NaCl salinity (0, 25, 50, 100, 200 mM) stress. Data presented are mean ± SE (n = 3).

Figure 3. Effects of NaCl on chlorophyll (A) and carotenoid (B) contents of rice leaves subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM). Vertical bars indicate mean ± SE (n = 3).

Figure 4. Optimum quantum yield (Fv/Fm) (A) and ETR (B) of leaves of 12-day old rice. Plants were fed by solution containing different concentrations of NaCl (0, 25, 50, 100, 200 mM) Leaves were placed in the dark adapted state for 30 min allowing the reaction centers to be re-oxidized. Fv/Fm ratio is the average from five replicates. Vertical bars indicate mean ± SE (n = 3).

Figure 5. Effects of NaCl on total protein contents of rice leaves subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM). Vertical bars indicate mean ± SE (n = 3).

Figure 6. Changes in the concentrations of sodium (Na+), potassium (K+) and the Na+/K+ ratio in rice plants subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM) (A) and after 24 h recovery in nutrient solution. Data presented are mean ± SE (n = 3).

Figure 7. Changes in malondialdehyde (MDA) (A) and H2O2 (B) levels in rice seedlings subjected to different concentrations of NaCl (0, 25, 50, 100, 200 mM) (S) and after 24 h recovery in nutrient solution (R). Data presented are mean ± SE (n = 3).