جستجوی مقالات مرتبط با کلیدواژه « Na+ » در نشریات گروه « زراعت »

Increasing water and soil salinity and the damage caused by it on plant products make it necessary to investigate the effects of salinity on crop plants. Studying the physiological traits changes under stress conditions is a suitable method for identifying the factors that affect crop tolerance to salinity stress and selecting tolerant cultivars.

A factorial experiment was conducted based on a randomized complete block design with three replications in the research greenhouse of the faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural. Experiment factors included the applying four salinity levels with Hoagland solution (no application of salinity as control, application of 30, 60, and 80 mM NaCl) and different soybean cultivars (Hill, LBK, BP, Hog, Deer, Gorgan 3, Sahr, Hobbit, Williams, JK, and LWK). In this experiment, soybean seeds were inoculated with Rhizobium japonicum bacteria and planted in pots containing sand. The irrigation was done by distilled water from the planting until the appearance of the main leaf, and after that, Hoagland's solution (without nitrogen) continued. Seedlings were harvested after 60 days and Na+ and K+ percentage, Na+/K+ ratio, proline, nitrogen percentage, nitrogen yield, and total dry weight were measured. Analysis of variance and comparison of the means (LSD test) was done by the SAS software (version 9).

The results show that with increasing the salinity, sodium percentage, Na+/K+ ratio, and proline amount increased and total dry weight, potassium percentage, and nitrogen yield decreased. Deer cultivar with the highest percentage of nitrogen at the levels of 0, 30, 60, and mM NaCl and the lowest percentage of nitrogen reduction (28%) have the lowest total dry weight reduction (54%) from the control treatment to the 80 mM treatment. Hag cultivar have the lowest increase in sodium percentage and the lowest percentage decrease in potassium absorption and the lowest Na+/K+ ratio compared to other varieties. LWK, LBK, and Sahar cultivars had the lowest tolerance to salinity with the highest amount of sodium accumulation, the highest Na+/K+ ratio, and low production of proline, and dry matter. The results of correlation coefficients showed that there was the most positive and significant correlation between total dry weight and potassium percentage (0.904**) and nitrogen percentage (0.902**).

According to the obtained results, it seems that the tolerant cultivars deal with salinity stress with mechanisms such as more potassium absorption and osmotic potential regulation. Among the investigated cultivars and according to the measured indicators, the Deer cultivar was recognized as a tolerant cultivar and can be used for cultivation in saline lands and the Hag cultivar can be used in breeding programs.

Salinity stress is one of the most vital abiotic stresses which limits the production of crops. In recent decades, the area under chickpea cultivation in Iran has tripled, but unfortunately, its yield has decreased from 610 to 500 Kg per hectare. The main reason for this reduction is the allocation of marginal lands under rain-fed conditions to chickpea cultivation. However, environmental stresses are the most critical factors of yield loss that can decrease chickpeas production significantly. The growth of chickpea is susceptible to salinity, and salinity stress affects their yield by affecting plant growth and symbiotic bacteria. Considering the current extent of salt-affected lands in Iran and in order to maintain and increase the area under chickpea cultivation, it is necessary to select the salt-tolerant genotypes. Therefore, this study was carried out to determining the salinity tolerance threshold of Kabuli -type chickpea genotypes.

The experiment was a split-plot randomized complete block design (RCBD) with three replicates at the research greenhouse of the faculty of agriculture of Ferdowsi University of Mashhad, Iran, in 2020. Chickpea germplasm, including 70 Kabuli type chickpea genotypes, were provided from the Mashhad chickpea collection at the Research Center for Plant Science, Ferdowsi University of Mashhad. Two weeks after seed planting, the salinity treatments included 12 and 16 dS.m-1 sodium chloride and 0.5 dS.m-1 (tap water) as control was applied. The recirculating nutrient system was applied, the nutrient solution was replaced weekly, and the salinity of nutrient solution was adjusted daily, but no acidity adjustments were made in the Hoagland solution. The plant height was measured before and after four weeks of applying salinity stress, and then the difference in plant height was calculated. Four weeks after salinity application, survival percentage, leaves survival, plant height, leaf electrolyte leakage, osmotic potential, shoot dry weight, and Na to K ratio were measured. Salinity tolerance indexes, including stress tolerance (TOL), mean productivity (MP), stress susceptibility index (SSI), geometric mean productivity (GMP), and stress tolerance index (STI), were calculated based on the shoot dry weight and separately for 12 and 16 dS.m-1 compared to the control treatment. Data were analyzed using Minitab 16 software, and the mean comparison was performed by Duncan Multiple Range Test (DMRT) at a 5% probability level. Interrelationship among different traits was calculated using Pearson's correlation analysis. STATISTICA 8.0 and SPSS 27 soft wares also performed a cluster analysis (based on Euclidean distance) and principal component analysis (PCA).

The results showed that for the salinity levels of 12 and 16 dS.m-1, 65 and 28 genotypes had a survival between 76 -100%, respectively. With the decrease in the survival percentage in 16 dS.m-1, the average percentage of leaf survival also decreased. With increased salinity levels from 12 to 16 dS.m-1, electrolyte leakage in the survival range of 76 -100, 51 -75, and 26 -50% increased by 8, 25, and 12%, respectively. With increased salinity levels from 12 to 16 dS.m-1, in survival ranges of 0 -25, 26 -50, 51 -75, and 76 -100%, shoot dry weight decreased by 15, 11, 36, and 14%. With increased salinity levels from 12 to 16 dS.m-1, the shoot Na to K ratio in the survival range of 26-50% did not change, and in the survival range of 0 -25, 51 -75 and 76 -100%, it increased two and nine times and 22% respectively. The highest average shoot Na to K ratio was also observed within the survival range of 0 -25%. In 12 and 16 dS.m-1, two genotypes, MCC1467 and MCC1394, were superior to other genotypes in most studied traits. The genotypes of the third cluster had a higher relative advantage for salinity tolerance.

In general, the results showed the diversity between chickpea genotypes under salinity stress. In 12 and 16 dS.m-1 salinity, MCC1467 and MCC1394 were superior to other genotypes in most studied traits. In saline conditions plant survival had a positive and strong correlation with leaf survival. In the saline condition, genotypes that can maintain their normal physiological function can maintain and expand more leaf area, which ultimately leads to more biomass production. The genotypes of the third cluster had a more advantage for salinity tolerance. Due to this study being conducted in greenhouse conditions, it is recommended to check the salinity tolerance of superior genotypes in field conditions.

Regulation of ionic homeostasis in plant cells is one of the important aspects in salt tolerance. In this study, the effect of 200 mM salinity stress after 1, 10 and 20 days of stress on some morphological characteristics, elements concentration and expression of some genes involved in salt tolerance of bread wheat genotypes, including lines 7 and 8 (salt-tolerant), line 16 (salt-sensitive) and Sistan cultivar (native tolerant cultivar) were studied factorially in a Completely Randomized Design (CRD) with three replications. The results showed that salinity stress reduced shoot biomass in all tolerant and sensitive lines with the lowest reduction in line 7. Under salt stress conditions, Na+ content had an increasing trend in all lines and K+ content had a decreasing trend. The lowest increase of Na+, and the lowest decrease of K+ and K+/Na+ ratio was observed in line 7. Under salt stress conditions, the highest expression of SOS1, SOS2 and SOS3 genes was observed in line 7 and the lowest expression was observed in lines 16 and 8. The results of this study suggest that line 7 had a higher degree of tolerance and can be considered in breeding programs as well as for additional studies in saline areas.

One of the biggest challenges of agriculture in the present era is environmental stresses, especially drought and salinity stress and its destructive effect on food security. In this regard, this experiment was conducted with the aim of selecting of tolerant cultivar of barley to salinity stress and identifying tolerance mechanisms in new and old barley cultivars.

This experiment was carried out during the two years of 2016-17 in the Milshbar Ardakan region located in Yazd province-Iran. Experimental treatments included 9 six-rowed barley cultivars including Nik, Mehr, Khatam, Reyhan, Goharan, Nosrat, Morocco, Afzal and Fajr 30 cultivars in three levels of irrigation water salinity including 4, 10 and 14 dS.m-1 were evaluated as a split plot experimental design so that water salinity as the main plots and cultivars as a sub-plots were randomly placed. The studied traits included yield and yield components as well as sodium and potassium levels, oxidizing enzymes and photosynthetic pigments.

The results showed that salinity treatment had a significant effect on day to emergence, day to tillering and grain yield. Salinity stress reduced grain yield components but this reduction was not significant. The effect of cultivar on plant phenology and day to emergence, tillering and ripening was significant, but on yield and yield components became insignificant. However, among the studied cultivars, Nik, Mehr, Khatam and Reyhan cultivars had higher yields and yield components. Among the salinity treatments, the highest grain yield was obtained at salinity of 4 dS m-1 with 5770.64 kg ha-1. With increasing salinity of irrigation water to 10 and 14 dS m-1, grain yield decreased by 18.04 and 27.55%, respectively, and reached 4729.29 and 4180.87 kg ha-1. The results of interaction showed that the interaction effect of year × salinity on grain yield components was significant and also the interaction of year × cultivar on 1000-Kernel weight and grain yield and year × salinity × cultivar on grain yield was significant. With increasing salinity stress, the amount of sodium ions in the shoots increased and potassium decreased, so the ratio of K/Na decreased. This mechanism was more effective in tolerant cultivars and in salinities of 4 and 10 dS m-1. With increasing salinity stress, the amount of oxidizing enzymes increased, so that with increasing salinity from 4 to 10 and 14 dS m-1, the amount of peroxidase enzyme was increased 1.59 and 2.23 times, catalase 1.52 and 1.95 times, and guaiacol peroxidase 1.47 and 2.89 times, respectively. With increasing salinity stress, all photosynthetic pigments increased. Among the cultivars, the amount of chlorophyll a and b in Morocco, Nik and Mehr was higher than other cultivars.

Based on the results of this experiment, it seems that tolerant cultivars, in addition to having high production potential, should have high potassium uptake mechanisms and high gene expression to produce enzymes that protect against oxidative stress in order to tolerate low to medium salinity stress.

Due to the possibility of environmental factors controll, studying the physiological effects of salinity under in vitro conditions can be a good solution for salinity tolerant cultivars selection. This experiment was conducted as factorial based on complete randomized design with four replications. Factors included sodium chloride concentrations (0, 2, 4, 6, 8 and 10 g.l-1) and three potato cultivars (Agria, Fontane and Sante). Results showed that the response of the studied cultivars to different salinity levels was different. In general, salinity stress reduced seedling, stem and root dry weights, stem length, number of nodes and photosynthetic pigments. Leaf area and stem diameter showed different responses to different levels of stress. In response to the salt concentration increase, Sodium and potassium concentrations increased in the stem  but the same was not happened in leaves. Among the studied cultivars and despite having the highest level of sodium in stems and leaves under stress conditions, Sante and Agria, tolerated higher salinity than Fontane. It seems that the ability to absorb salt and transfer it to the plant can play an important role in salinity tolerance under in vitro conditions.

In order to investigate the effect of irrigation water salinity on some characteristics of Ajowan (Carum copticum L. C.B. Clarke), a field experiment has been conducted in a completely randomized design with 3 replications in Isfahan, Iran during 2013. The treatments involve different levels of saline water, namely 2.5 (control), 6, 9, and 18 dS.m-1. The determined traits include the yield, biochemical parameters, mineral contents, and seed essential oil content and quality. Results show that increasing salinity decreases biological yield and seed yield. Changes in essential oil components, caused by salinity, have been low, showing no specific trend. The major compound in the seed essential oil of C. capticum is thymol (56.1% to 61.2% of the essential oil). The highest concentration of total protein (root: 3.6 and shoot: 8.2 mg g-1 DW) is assigned to the control treatment, dropping significantly as salinity levels rise. Increasing salinity enhances the amount of proline and reducing sugars so that the highest amount of root proline, equal to 12 mg g-1 FW, and reducing sugars (root: 30.5 and shoot: 62 mg g-1 DW) comes from salinity of 18 dS.m-1. Increasing salinity levels raises the amount of phenolic compounds in the shoot, though this increase has not been considerable. The treatment of 18 dS.m-1 has had the lowest concentration of K+ (root: 5 and shoot: 22 mg g-1 DW) and the highest concentration of Na+ (root: 54 and shoot: 64 mg g-1 DW).It can be concluded that by increasing salinity levels, the amount of resistant osmolytes rises.

The effect of drought and salinity stress in view of water deficiency are similar to each other, but under long term-salinity stress, in addition to drought stress the plant experiences increased osmotic and high ion stress. There are different levels of salinity (more than 38% of Golestan’s total land area is salt-affected) and various farming conditions (rain-fed and irrigation) in Golestan Province, Iran. The purpose of this study was to evaluate the growth, water use efficiency and sodium and potassium concentrations of plant in irrigated and rain-fed wheat genotypes (selected from the first year of the experiment). The experiment was under greenhouse conditions and was conducted to physiologically compare genotypes selected in the first year in a factorial arrangement with two irrigation regimes (5 and 75 % water lost from soil available water), four levels of soil salinity (0, 4.5, 6.5, and 8 ds/m) and two tolerant genotypes (selected from the first year) in a completely randomized design with three replications. The greenhouse is located in Gorgan city of Iran. Two genotypes selected from the first year of the experiment at moderate salinity (9 ds/m) and under rain-fed condition i.e. N- 87- 20 and Karim were the experimental material, respectively. In this experiment leaf area, number of stomata, sodium and potassium concentrations for leaf and stem, total water use from sowing to maturity, water use efficiency (WUE) for grain and biomass and yield were measured. The results showed that genotype n- 87- 20 had higher leaf area but lower stomata density than those of Karim. Genotype n- 87- 20 in 25% soil available water, i.e. drier condition had similar yield (1.20 vs. 1.16 gr/plant) to Karim. In the wetter condition the yield of N- 87- 20 was higher than Karim (2.00 vs. 1.64 gr/plant). In drier condition, Karim had higher WUE than in wet condition but for N- 87- 20 genotype, it was reverse and it had higher WUE in dry than in wet condition. The sodium concentration in stem was twice as bigger than that of leaf (0.58 and 0.32%, respectively) and with increase in unit salinity of soil to 8 ds/m sodium concentration in leaf and stem increased 0.068 and 0.025 %, respectively. There was not any difference between two genotypes for Na+/ k+ in leaf and stem but with an increase in soil salinity the Na+/ k+ for leaf and stem decreased. N- 87- 20 was better genotype in irrigated conditions with no or moderate salinity stress and Karim was better genotype under rain-fed condition. Up to 8 ds/m of soil salinity Na+/k+ ratio could indicate the difference between genotypes.

The basis of breeding programs is the presence of genetic diversity. The role of nuclear radiation to create genetic diversity has been well documented. Mutations induced by irradiation with gamma rays has had a significant role in improving the lot of important agronomic traits in plants. Salinity stress every year affects crops in large areas of the country. Since crops' yield is reduced due to the salt toxicity, hence the production and introduction of high yielding salinity tolerant varieties can minimize the phenomenon effect. In order to determine some stability indices related to wheat grain yield the fifth generation (M5) under salinity conditions, 15 selected lines from the fourth generation (M4) with two parents' genotypes (‘Arg’ and ‘Bam’) and two genotypes produced in Yazd region (‘Sivand’ and ‘Narin’) were planted under both conditions of non-stress )2 dsm-1) and salinity stress )10 dsm-1) in research field of the National Salinity Research Center (NSRC) in Yazd province. Each plot included two rows in 1 m long with a row spacing of 20 cm. During the growing season, to determine the soil salinity in the root growth zone the soil sampling was carried out to a depth of 0-90 cm. The average salinity under conditions of non-stress and stress was obtained 2.3 and 9.7 dsm-1, respectively. Analysis of variance for a complete random block design was performed on grain yield, yield components and sodium and potassium ions traits and the Comparison of means was conducted by least significant difference (LSD) test. Tolerant indices of mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), Stress stability index (SSI), Tolerance index (TOL) were calculated to investigation salinity. Also, Pearson correlation, stability analysis and cluster analysis was performed The results of analysis of variance for grain yield and yield components showed the genetic diversity among lines. Line two (Arg-200 gray, 246.67 g m-1) and one (Bam-150 gray, 165.55g m-1) had the highest grain yield, K+ and K+/NA+ ratio and the lowest and NA+ ions under both conditions. Also, lines tolerant to salinity had a lower level of NA+, high level of K+ and a higher K+/NA+ ratio under salinity stress conditions to sensitive lines. Regarding the positive and significant correlation between grain yield in both conditions and indices of MP, GMP and STI, the indices were selected as the most desirable tolerance indices. According to three-dimensional graph Fernandez were introduced that lines one, two and eight as the most tolerant lines to salinity stress. The experiment results showed, indices of MP, GMP and STI are the most suitable indices for selection of lines tolerant to salinity. Lines one, two and eight had high grain yield under both conditions. So, according to the results lines one, two and eight can be introduced as stable lines and with high yield under salinity stress conditions and the fifth generation and it is recommended to introduce these three lines for cultivation in the sixth generation.

In order to study the physiological aspects of water deficit stress on important quantitative traits of 14 sugar beet genotypes, a two-year experiment was conducted as split plot based on randomized complete block design with four replicates at Sugar Beet Seed Institute, Karaj, Iran in 2009-10. Two irrigation levels including S1 (normal irrigation after 80 mm evaporation from the class A pan) and S2 (irrigation after 180 mm evaporation) were applied by changing the irrigation round. Irrigation was performed similarly for both treatments from planting to the establishment (6-8 leaf) stage and thereupon applied based on evaporation from the class A pan. The highest root yield belonged to the genotypes SBSIDR-5, SBSIDR-8 and SBSIDR-14 and the lowest ones to SBSIDR-2, although all genotypes were placed in one group. Furthermore, the effect of year on potassium and sodium was significant. In SBSIDR-5, SBSIDR-1, and SBSIDR-7 genotypes, the Na level was the least while in SBSIDR-4 it was high. Compared with SBSIDR-1, SBSIDR-5, SBSIDR-6, SBSIDR-7, SBSIDR-9 and SBSIDR-10, SBSIDR-4 was placed in different group. In conclusion, genotype SBSIDR-5 was selected as the best pollinator.

In order to investigate effective morpho-physiological traits related to salinity resistance، and their relationship with grain yield as well as study of salinity tolerance and susceptibility indices in 169 barley recombinant inbred lines، a population of barley derived from a cross between Arigashar and Igri، this experiments were carried out using alpha lattice design with two replications during years 2011 to 2013 in Birjand station under non-stress and salinity stress conditions (ECwater=10ds/m and ECsoil=12ds/m). During cropping seasons، lines were evaluated for morpho-physiological traits، day to heading، day to maturity، spike length، peduncle length، plant height، leaf chlorophyll content (SPAD)، flag leaf Na+ and K+ content and K+/Na+، flag leaf length، width and area، grains in spike، thousand kernel weight (TKW)، biological yield (BY)، grain yield (YLD)، harvest index (HI) and salinity tolerance and susceptibility indices. Combined analysis of variance of studied traits in two conditions revealed significant difference among years، genotype and genotype×years interaction. Under salinity stress conditions، biological yield، grains in spike، harvest index، flag leaf Na+ content and K+/Na+ and thousand kernel weight (TKW) and under non-stress conditions، biological yield، harvest index and flag leaf area have high association with grain yield. With regard to grain yield under salinity and non-stress conditions (Ys and Yp) and tolerance and susceptibility indices (SSI، TOL، MP، GMP، STI and Harm)، liens were grouped in four classes، including: a) semi-high-yielding and salinity tolerance، b) low-yielding and salinity susceptibility c) high-yielding and salinity susceptibility، and d) high-yielding and salinity tolerance. GMP and STI indices had the highest correlation with grain yield under stress and non-stress conditions، and selected as the best salinity tolerance indices.

Salinity is one of the most important abiotic stresses that decreases agricultural production in arid and semi-arid soils. To study the effect of salinity on root characteristics, Sahara3771 (salt tolerant) and Clipper (salt-sensitive) cultivars were evaluated in a factorial experiment based on randomized complete block design with three replications under 100 mM NaCl and normal conditions in hydroponic culture. Salinity treatment was applied at three leaves stages and continued for five weeks. To establish salinity stress, 500 mL of NaCl along with the half concentration of Hoagland solution was added at first day of stress treatment and after second day and onwards, 1000 mL NaCl and complete concentration of Hoagland was used. Root length, volume, fresh and dry weight, chlorophyll fluorescence and K+/Na+ ratio were measured at 24 hours, three weeks and five weeks after stress application. Analysis of variance and mean comparisons revealed that 100 mM NaCl compared with normal condition caused a significant reduction in root fresh weight and the K+/Na+ ratio. Significant differences were observed among growth stages for root fresh and dry weight and K+/Na+ ratio and with advanced of growth stages, the mean of studied traits was increased. Significant differences were found between cultivars for root volume and fresh weight at 1% probability level. Maximum root length and volume was observed in Sahara 3771 at shooting stage. Salinity stress caused more reduction in root weight and K +/Na+ in the susceptible cultivar (Clipper) compared with tolerant one (Sahara 3771).

This research was carried out on two canola cultivars (Hayola401 and RGS) at Research Laboratory of Islamic Azad University¡ Borujerd Branch. In this research the effects of GA3 (0.05 Mm)¡ SA (5 M) and NaCl (75¡ 100 and 150 Mm) on Na and K changes in root¡ shoot¡ specific leaf area (SLA)¡ leaf weight ratio (LWR) and leaf area ratio (LAR) were evaluated. The results showed that increasing salinity decreased the SLA¡ LWR and LAR while it decreased the K ion and increase the Na ion content as compared with those of control treatment. Applying of gibberellic acid and salicylic acid increased SLA¡ LWR and K ion content in root and shoot of the two cultivars significantly¡ but the effect of GA3 on these traits in higher concentration of NaCl (150 Mm) was not significant. It is therefore concluded that Hayola401 was more tolerant to salinity stress as compared to RGS cultivar.

This research was carried on in order to investigate the response of wheat cultivars to salinity tension as factorial experiment and in complete randomized block design in four replications in Islamic Azad University Shoushtar Branch. In this experiment the response of nine wheat cultivars including Chamran, Karchia66, Mahoti, Roshan, Alvand, Kavir, Ghods, Atrak and Tjan at vegetative growth stage in three salinity levels of water irrigation zero (control), 6 and 12 ds m-1 was investigated. Results showed salinity tension decreased seedling dry weight, chlorophyll concentration, leaf K concentration and leaf Kﳖ ratio of wheat cultivars. While, malondealdehid concentration, leaf Na concentration and leaf solution carbohydrates concentration increased under effect of salinity tension. The highest salinity tension tolerance index was observed in Mahoti and Karchia 66 cultivars (0.0089 and 0.0087, respectively). While, Ghods cultivar allocated the minimum amount of this index (0.0028). Karchia 66 and Mahoti cultivars had the highest seedling dry weight at 12 ds m-1 salinity level in comparison with other cultivars.

The effect of different levels of salinity arising from sodium chloride on plant growth parameters, phosphorus, potassium and sodium uptake by saffron plant with and without mycorrhiza was studied in a pot experiment. A factorial experiment with a randomized complete block design was performed. The results showed that increasing salinity from 1.5 to 7.5 dS m-1 significantly decreased plant dry weight. The decreased plant dry weight was attributed to the toxicity resulting from high Na+ concentration and low K+ concentration in plant tissues. Mycorrhizal colonization led to a significant reduction in the concentration of Na+ and improved K+: Na+ ratio,and this in turn, resulted in a considerable increase in plant growth. Percentage of root colonization was not affected by salinity. Despite the reduction of mycorrhizal plant dry weight with increasing salinity, mycorrhizal growth response increased as salinity was increased. Shoot phosphorus concentration and shoot phosphorus content of mycorrhizal plant were significantly higher than those in the shoot of non-mycorrhizal plant. Although shoot phosphorus content decreased with increasing salinity, shoot phosphorus content per unit root length colonized increased as salinity was increased, and this may explain the increased mycorrhizal growth response with increasing salinity. In conclusion, the result of this study, for the first time, showed that saffron has high mycorrhizal dependency, and mycorrhizal colonization alleviated the detrimental effects of salinity on plant growth, uptake of phosphorous and potassium and K+:Na+ ratio.

To study the effect of salinity on germination and threshold of barley germplasms two experiments carried out as a factorial arrangement based on completely randomized designin greenhouse and laboratory condition. In the first experiment 23 barley germplasms (17 wild and 6 improved barely cultivars) were investigated for germination index with four treatments of salinity (0، 100، 200 and 300 Mm NaCl) in three replications and in the second experiment the threshold salinity of 7 germplasms that selected from the first experiment were analyzed in five treatments (1. 3، 5، 10، 15 and 20 ds. m-1) with four replications. At the end of the first experiment،following factors were measured: germination percent،root length،shoot length،root fresh weight،root dry weight،shoot fresh weight،shoot dry weight،Na+ root content،K+ root content،Na+ shoot content،K+shoot content also threshold salinity، shoot length، dry and fresh weight، Na+and K+content was measured in the second experiment. The result showed that increased salt concentrations caused decrease final germination percentage (P≤0. 05). Some of germplasms showed high tolerance to salinity. The relative yield of dry weight indicated that H. vulgare،var. Afzal with 25. 24 ds. m-1andH. murinum (Ilam) with 16. 65 ds. m-1 which had the maximum and minimum EC50 value respectively between these germplasms. In this experiment the native cultivar had a highest tolerance with compared to the other cultivars that is likely contain genes for resistance to salt stress.

To investigate the effect of K fertilizer on yield and yield components of three watermelon cultivars, a two-year study (2007-2008) was conducted in Ardestan Agricultural Research Center (Isfahan province) by using of split plot randomized based on complete block design in three replications. Three watermelon cultivars (‘Sugar baby’, ‘Charleston Grey’ and ‘Mahbubi’), were assigned as main plots and four K fertilizer levels (zero, 50, 100, and 150 kg K.ha-1) were assigned as subplots. Two and three times higher than consumption of K fertilizer (100 and 150 kg K.ha-1) in compared to normal conditions (without salinity), led to a 24.8 and 18.5 percent increase in yield of ‘Charlston Gray’ and ‘Sugar Baby’, respectively. The highest fruit yield (39112 kg.ha-1), was obtained using 150 kg K.ha-1 in ‘Charleston Gray’ cultivar. Potassium applications at all levels, increased fruit number in ‘Sugar Baby’ and fruit weight in ‘Charleston Gray’, were considered as the main reason for increasing yield. By increasing of K application, the ratio of Na/K in the leaves from 0.61 to 0.33 and in the stems from 0.81 to 0.4 was decreased. The results indicated that in saline conditions, higher levels of K fertilizers can reduce the deleterious effects of salinity and thus may improve watermelon yield.