Effects of salt stress on growth and nutrients concentration in cx hickpea (Cicer arietinum L.).Introduction
Cicer arietinum is one of the most important grain legumes grow in semi-arid regions, offering high-quality protein concentration and increasing the imput of combined [N.sub.2] into the soil. The chickpea has been traditionally used in rotation with cereal crops, and the benefits of these practies are well known.
Salinity has long been known to influence the distribution of plant nutrients in legumes. NaCl toxicity, the predominant form of salt in most saline soils, enhances the sodium content and consequently affects the absorption of other mineral elements . Indeed, high levels of Na inhibit Ca and K absorption, which results in a Na/K antagonism . In brassicas, Ashraf and Mcneilly , suggested the maintenance of high tissue K/Na ratio as criteria for salt-tolerance.
Plant species adapt to high salt concentrations in soils by lowering tissue osmotic potential with the accumulation of inorganic as well as organic solutes . Cations [Na.sup.+] and [K.sup.+] are known to be the major inorganic components of the osmotic potential . Cation [Na.sup.+] may cause metabolic disturbances in processes where low [Na.sup.+] and high [K.sup.+] or [Ca.sup.2+] are required for optimum function .
Cell membrance function may be compromised as a result of [Na.sup.+] replacing [Ca.sup.2+], resulting increased cell leakiness . The objective of the present work is to study chickpea salt tolerance mainly as the ability to maintain plan growth and effects the absorption of mineral elements under salt-affected conditions.
Meterials And Methods
2.1. Biological and materials and growth condition:
Chickpea (Cicer arietinum L.) cultivars Flip93, Arman, ILC482, Hashem were obtained from the Center dry farming Research Institute KermanshahIran, and local chickpea from region Urmia-Iran. The set up consisted of 80 made of clay pots (5 genotypes x 4 treatment x 4 replications) with a top diameter of 35 cm and depth of 25 cm, filled with 6 kg farm soil (EC = 1.7 [ds.m.sup.-1], PH = 7.8, %SP = 38 and loam texture). Before sowing, seed were surface sterilized in 30% mercuric choloride for 2 min, rinsed with sterile water. Plants were cultivated in greenhouse with 16-h light and 8-h dark cycle, 25 and 20 day and night temperature and 55-70% relative humidity.
2.2. Experimental treatments and harvest:
Plants were harvested at 75 days of culture. The plants were subjected to salt stress by adding NaCl to the growth medium (0.0, 2.5, 0.5 and 7.5 [ds.m.sup.-1]) control plants were maintained in a NaCl-free solution. The salt solution on 3 consecutive days before sowing in order to obtain the required salinity level. Chickpea seeds were sown in each pot to depth of 4 cm and thinned to three plants of uniform size were maintained in each pot after 2 week. A sample of root, stem and leaves of each plant were detached, weighed, and dried at 70[degrees]C for 48 h to calculate dry weight.
2.3. Nutrient determinations:
For the determination of sodium and potassium concentrations dried samples of root, stem and leaves dried at 105[degrees]C for 48 h, afterwards were ground to pass a sieve and ashes by electrical oven at 580[degrees]C for 2 h, and digested with chloridric acids. Ions content was analysed using the Flamphotometer model JENWAY PEP 7 according to method .
2.4. Statistical design and analysis:
The data were subjected to analysis of variance (ANOVA) using the MSTAT-C statistical package, Means were separated using least significant difference (L.S.D) test, the confidence level was set at (p < 0.05).
3.1. Growth parameters:
From table 1 it can be seen that cultivars respondence differently to saline conditions shoot dry weight (SDW), root dry weight (RDW) and plant dry weight (PDW) decrease with increasing salinity levels. At an EC of 7.5 [ds.m.sup.-1], the reduction percentage in (SDW) of plants as compared to the respective controls were 46, 16, 44, 36 and 22% for Flip93, Arman, ILC482, Hashem and local chickpea cultivars, respectively.
At the highest level of salinity (7.5 [ds.m.sup.-1]), the reduction percentage in (RDW) relative to the control value were 42, 33, 40, 62 and 62% for Flip93, Arman, ILC482, Hashem and local chickpea cultivars, respectively. Plant dry weight (PDW) was affected by salinity especially for Flip93 and ILC482 cultivars.
Regarding root to shoot ratio (RSR), value significantly differed between cultivars in a rang 0.71 to 0.47 (Table 1). In plants with higher (RSR), Flip93 and ILC482 was observed a lower decrease of SDW with salt dosage. This parameter dimished in Arman, Hashem and local cultivars with increasing salinity levels, whereas RSR increasing for Flip93 and ILC482 cultivars with NaCl application.
3.2. Ion concentrations:
The concentrations of Na increased in the roots and shoots under saline condition, particularly in susceptible cultivars (Fig. 1). A significant interaction occurred between salinity on Na accumulation in chickpea plants with increasing salt stress. The tolerant cultivars Flip93 and ILC482 showed a lower level of Na accumulation of both roots and shoots with increasing salinity.
The potassium content decreased in the roots of chickpea cultivars tested with increasing salinity (Fig. 2). There were significant interactions in the contents of potassium in the roots of chickpea plant with increasing salt stress. Althoug potassium content decreased with increasing salinity, but there were no significant interaction between salinity on potassium content in the shoots of the various cultivars growing in any treatment. The tolerance cultivar ILC482 was an inherently superior potassium, under non-saline conditions. It showed a higher level of potassium accumulation in the shoots with increasing salinity (Fig. 3).
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
The concentration of Na and K ions are determind by the rates uptake, transport and compartmention recent evidence suggests that K uptake is more selective than Na uptake. Na ions compete with K ions during uptake and energy is expended in extruding excess Na under the high salinity, ILC482 and Flip93 retained the highest K concentration.
Salinity had a significant effect on K/Na ratio. The chickpea cultivars Flip93 and ILC482 had the highest K/Na ratio in the shoots and roots (Table 2).
This study indicated that salinity reduced plant growth irrespective of the cultivar that is evident from the decline in dry weights of both roots and shoots with increasing salt stress. As stated by Munns , Suppression of plant growth under saline conditions may either be due to the decreasing availability of water or to the increasing toxicity of sodium chloride associated with increasing salinity. Chickpea was initially able to maintain water uptake, but accumulated large amounts of [Na.sup.+] quicky. This early accumulation of salt may have also served to decrease the osmotic potential of the plant tissues and facilitate water uptake. The root and shoot dry weight decreased in all cultivars. Particulary, in susceptible cultivars. Root- to- shoot ratio decreased for all cultivars except, for Flip93 and ILC482 with the highest NaCl tolerance, in terms of growth also, showed higher RSR with increased salt stress, where as significant reduction was observed in susceptible cultivars. The root dry weight showed higher decline than did the shoot dry weight in all cultivars. The reduction in roots and shoots dry weight directly affected on the root- to- shoot ratio (RSR). In generall, Flip93 and ILC482 cultivars seemed to have a better potential for salt tolerance compared with the other cultivars. The reduction in dry weight under salt stress may be attributed to in hibition of hydrolysis of reserve synthesising food and its translocation to the growing shoots . According to Cheeseman , salinity stress imposes metabolic carbon to storage poor so that less carbon is available for growth. Reduction of plant growth and dry matter accumulation under saline conditions has been found in several important grain legumes . NaCl also altered the nutritional balance of chickpea plants.
There were significant differences in the ions accumulation in the roots and shoots of the various cultivars growing in any on treatment, so that the Na accumulation was increased with increasing salinity. Flip93 and ILC482 showed lower accumulation of Na in the shoots. On the other hand, the content of K was decreased with increasing salinity. Flip93 and ILC482 cultivars showed higher accumulation of K in the roots. The sensitivity to salt stress of chickpea plants assayed here, most of cultivares accumulated Na mainly in the roots ensuring a limited Na toxicity in the shoots as has been reported by Rogers et al., . This capacity to accumulation of Na in the roots might be related to a protection of the photosynthetic apparatus from Na damage . The K/Na ratio for non-halophytes should be higher than 1 for normal functioning of all metabolic processes of the plant. In the present study, this parameter was lower of 1 with salt treatment. In this regard, (Baalbaki et al., 2000), postulated the involvement of two physiological mechanisms to impact of salinity: sodium compartmentalization in roots and K/Na ratio selectivity in reducing damage associated with excessive sodium levels in soils. Mcneilly, suggested that maintenance of high tissue K/Na ratio as criterion for salt-tolerance in brassicas. The tolerance and sensitivity to salinity of different plant species has been established to be genetically controlled [16,11].
The results of this classified as having low tolerance to salinity, cv. ILC482 and Flip93 appeared to have a higher tolerance to salinity than for the other cultivars and the most significant impact of increased NaCl on growth of chickpea is most affected by accumulation of salt plan tissues.
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Simin Azimi, Reza Amirnia, Mehdi Tajbakhsh and Mahdi Ghiyasi
Department of Agricultur, Agricultural Faculty, Urmia University, Urmia, West Azarbaijan, Iran
Simin Azimi, Department of Agricultur, Agricultural Faculty, Urmia University, Urmia, West Azarbaijan, Iran
Table 1: The effect of NaCl treatments on shoot dry weight (SDW), root dry weight (RDW), plant dry weight (PDW) in g [plant.sup.-1] and root-to-shoot ratio (RSR) of five chickpea cultivars cultivar NaCl(EC) SDW RDW Flip93 0.0 2.615 (a) 1.850 (a) 2.5 2.547 (a) 1.668 (a)b 5.0 2.253 (bc) 1.645 (bc) 7.5 1.388 (ghi) 1.065 (efghi) Arman 0.0 1.650 (fg) 1.100 (cdef) 2.5 1.533 (fgh) 0.997 (defg) 5.0 1.500 (fghi) 0.875 (efghi) 7.5 1.375 (ghi) 0.732 (fghij) ILC482 0.0 2.392 (ab) 1.352 (bcd) 2.5 2.053 (cd) 1.220 (cd) 5.0 1.962 (de) 1.180 (efgh) 7.5 1.322 (hij) 0.810 (j) Hashem 0.0 1.710 (ef) 0.802 (efghi) 2.5 1.495 (fghi) 0.705 (ghij) 5.0 1.288 (hij) 0.500 (ij) 7.5 1.087 (j) 0.357 (j) Local 0.0 1.555 (fgh) 0.927 (efgh) cultivar 2.5 1.470 (fghi) 0.727 (fghij) 5.0 1.295 (hij) 0.647 (ghij) 7.5 1.212 (ij) 0.610 (hij) cultivar NaCl(EC) PDW RSR Flip93 0.0 4.465 (a) 0.71 (b) 2.5 4.215 (ab) 0.71 (b) 5.0 3.898 (bc) 0.73 (b) 7.5 2.453 (fgh) 0.76 (a) Arman 0.0 2.750 (def) 0.66 (c) 2.5 2.530 (efg) 0.65 (c) 5.0 2.375 (fgh) 0.58 (e) 7.5 2.108 (gh) 0.53 (fg) ILC482 0.0 3.745 (b) 0.56 (ef) 2.5 3.273 (cd) 0.59 (e) 5.0 3.142 (de) 0.60 (d) 7.5 2.132 (hi) 0.61 (d) Hashem 0.0 2.513 (efg) 0.47 (gh) 2.5 2.197 (fgh) 0.47 (gh) 5.0 1.788 (hi) 0.39 (i) 7.5 1.445 (i) 0.33 (ij) Local 0.0 2.480 (efg) 0.60 (d) cultivar 2.5 2.197 (fgh) 0.50 (g) 5.0 1.945 (ghi) 0.50 (g) 7.5 1.822 (hi) 0.50 (g) L.S.D. (P [less than or equal to] 0.05) Mean followed by the same superscript letter (a-j) within a column do not differ (p<0.05) using the L.S.D. test. Table 2: Effect of NaCl treatment on potassium/sodium ratio (K/Na) in root and shoot of five chickpea cultivars. Cultivar K/Na shoot 0 2.5 5.0 7.5 Flip93 1.5100 1.3200 0.9275 0.8475 Arman 1.0030 0.9775 0.8450 0.7975 ILC482 1.247 1.0150 0.9600 0.8250 Hashem 1.048 0.9225 0.8250 0.7500 Local cultivar 1.267 0.9425 0.8950 0.7700 Cultivar K/Na root 0 2.5 5.0 7.5 Flip93 1.440 1.2830 0.9000 0.8375 Arman 1.0150 0.9400 0.3850 0.7550 ILC482 1.3170 1.1120 0.9575 0.7875 Hashem 0.9700 0.8925 0.8075 0.7500 Local cultivar 1.168 1.0170 0.8325 0.8000