Evaluation barley germination in NaCl + Ca[Cl.sub.2] solution, natural saline water and saline soil.
In semi arid and arid region, irrigation has a main role to gain economic production. The main factor in irrigation assessment is recognition of plant interaction to water. Irrigation water has dissolved salt, thus salinity must be investigated. In long term without amendatory operation dissolved salt accumulate in soil and lead to reduction in yield and finally soil damaging. Thus recognizing plant reaction to salinity is one of main factor in assessing irrigation management [17,18,19,20,21]. Salinity can be disastrous because it causes many direct and indirect harmful effects, inhibits seed germination, induces physiological dysfunction and often kills nonhalophytes even at low concentrations and limits agricultural development . In principle, much of the soil salinity could be reduced by installing drainage systems and leaching the soil profile with adequate quality water. In practice, however, these amelioration methods may be too expensive or not possible, and there are many cases where it always will be necessary to grow crops that have some salt tolerance. When evaluating the salt tolerance of plants, it is important to recognize that the results can be affected by the composition of the salts used in salinizing the plant growth medium. Many agronomic experiments with plants growing in soils have been salinized by adding NaCl and Ca[Cl.sub.2] at a 2:1 molar ratio.
Germination is complicate phenomenon comprising physiological and biochemical variation due to embryo activation. Salinity as a non live stress makes many hardships for seed in germination period. Salinity decrease water availability for the seed by taking down osmotic potential and in second stage cause to toxicity and change in enzyme activity . Saline soils have many dissolved salts including cation and anion. The most prevailing cation and anion are [Na.sup.+], [Ca.sup.2+], [Mg.sup.2+], [K.sup.+], [Cl.sup.-] and [So.sub.4.sup.2-]. Plant growth and development in saline soil is scanty due to high osmotic pressure that finally cause to reduction in water availability . Also direct toxicity resulted from abundant presence of this ions have a preventive effect on plant and at last this interaction put some limitation for plant growth . The main growth stages in plant are germination, vegetative and reproductive. Plant sensitivity to salinity during different growing stage is varying. Mast plants are resistant to salinity during germination but in plantlet outburst stage is sensitive and salinity damages those . Primary signs of salinity are delaying in germination, plantlet appearance and bud enfeeblement. Damaging in this sensitive stage may decrease plant congestion and lead to reduction in yield significantly. Usually with increasing plant age, their resistance to salinity increase .
One of the most effective ways to facing with salinity is identifying enduring plant to salinity. Resistance to salinity is varying among different species of plant, also among different variety of one species [2,5,16]. Furthermore plant endurance to salinity may be differing upon the culture medium, type of salinity and plant growth stage. When plant is exposure to salinity by NaCl, water and ion transport processes may be affected and disturb plant nutrient situation and ionic balance  or disordered physiological process [12,14]. The salt tolerance of two greenhouse bell-pepper hybrids was studied during germination, seedling growth and vegetative growth in hydroponics culture . Salinities up to 50mM delayed germination but did not reduce the final germination percentage. Seedling growth was reduced significantly with salinities higher than 10 mM NaCl. Plants growth parameter such as plant height, total leaf area and dry weight were significantly reduced at salinities higher than 25 mM NaCl in both hybrids.
The effect of increasing concentration of different salts in solution and soil extract solution of comparable osmotic potentials on germination of suaeda salsa seeds was studied . Seed germination decreased significantly with increased salinity. Germination inhibition was in following order: Mg[Cl.sub.2] > [Na.sub.2][So.sub.4] > [Na.sub.2][Co.sub.3] > NaCl > soil extract solution > Mg[So.sub.4]. Non-germinated seeds under all salt treatment s recovered completely when transferred to distilled water, indicating that there was little specific ion effect on seed viability. Low levels of salinity (0.05- 0.1 mol increased seedling growth, while high levels (>0.2 mol l-1 NaCl) inhibited the growth significantly. Shamsaddin saied et al  studied the effects of salinity on germination, vegetative growth and some physiological characteristics of canola cultivar. Results showed that salinity has very significant effect on germination percentage, germination homogeneity, germination rate, and rootlet and polomul length at the end of germination stage. Shoot length, dry weight, diameter and number of nodes per shoot were significantly affected also by salinity at vegetative growth. The effect of cultivar on this trait was also significant. In both growth stages, cultivars response to salinity was different. Barley (Hordeum Vulgar) is one of the most tolerant plants to salinity stress that is widely grown in semiarid and arid regions. Barley resistance to salinity, drought and heat stress is more than wheat and endures in unfavorable environmental condition better than wheat. Barley strength and rate of germination is more than wheat but in seedling stage wheat is more resistance than barley . The objective of this study was to investigate the effect of soil salinity on germination of barley seeds and comparison with germination in without soil (in vitro) medium.
Materials and Methods
Most previous experiments to study effect of salinity stress on germination of different plant use artificial saline water with NaCl and Ca[Cl.sub.2] combination. Ionic compound of artificial and natural saline water are different hence we expect dissimilar response of plant to this solutions. Thus in vitro experiments conducted in two different parts with artificial and natural saline water. Germination in Petri dish can not show real condition of field because plant seeds in soil must encounter both osmotic potential of saline water and matrix potential of soil particle, therefore third experiment was conducted in shallow pots with 15cm diameter and 10cm deep contain soil. Artificial saline water with same equivalent combination from NaCl and Ca[Cl.sub.2] was used. Natural saline water prepared from Haoz Soltan Lake in Ghom province, Iran. Electrical conductivity (EC) of this water was 300dS [m.sup.-1]. Table 1 shows chemical analysis of natural saline water. Saline soil prepared from Ghomrood County in Ghom province, Iran. Soil texture was loamy sand and electrical conductivity (EC) of saturated extract was 3.85dS [m.sup.-1]. Table 2 shows the results of physical and chemical analysis of the soil.
A completely randomized experiment with 13 treatment and 3 replication was conducted with saline water contain equivalent ratio of NaCl and Ca[Cl.sub.2]. Experiment treatments was 0.0055(control), 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25 and 27dS [m.sup.-1]. Seeds were germinated on 3 sheets of 9cm filter paper in 10 diameter Petri dishes with 10ml solutions. The Petri dishes were sealed to prevent water loss. Twenty seeds were used for each treatment. The experiment was carried out in 24[degrees]C temperature auto-controlled growth chamber. Germination was recorded daily and at 24 hours intervals until all the seeds were completely germinated or the number of germinated seeds in the two continuous counting became alike.
Experiment designing and treatments was like first stage but in this part natural saline water with 300dS [m.sup.-1] EC was used. This saline water mixed with drink water at distinct proportion and EC was adjusted with a portable EC-meter. As shown in table 1, composition of this natural saline water was different from NaCl + Ca[Cl.sub.2] solution. After preparing Petri dishes and placing seeds, treatments transfer to growth chamber and temperature adjusted at 24[degrees]C.
In order to investigate other component of water potential that affect water availability for seeds and roots, the last experiment was conducted in soil medium. A loamy sand soil was used in flowerpots with 15cm diameter and 10cm depth. Natural saline water was used in this experiment. Each flowerpot leached 3 fold with related saline water treatment and then 20 seeds cultured in each of them. Dry weight mass wetness of soil measured by gravimetric method and irrigation program based on 70% F.C water content of soil, thus each flowerpot must be weigh every day. Germination was recorded daily and at 24 hours intervals until all the seeds were completely germinated or the number of germinated seeds in the two continuous counting became alike. Statistical analysis was carried out using SPSS 11.0 to determinate differences among treatment groups for germination percentage and germination rate.
Result and Discussion
Variance analysis results on effect of salinity on Barely seed germination shows that treatments have a significant effect on seed germination. Fig 1 shows the final germination percentage of barely after 12 days. In NaCl + Ca[Cl.sub.2] solution germination percentage differences between salinity treatments are not significant until 25dS [m.sup.-1] but as the salinity increase, difference became significant in 27dS [m.sup.-1]. The seeds germinated best in the treatment 9dS [m.sup.-1]. The germination percentage decreased as the level of salinity increased in all the salt solution. Maximum reduction in NaCl + Ca[Cl.sub.2] solution and natural saline water was 38 and 38.5 percent in treatment 27dS [m.sup.-1] respectively. In soil medium although there is no significant difference among lower treatments (0-15 dS [m.sup.-1]) but higher salinity treatments have a significant difference with each other. Important notice in this investigation is that germination in soil medium compare to solutions (artificial and natural saline water) with increasing salinity, decrease until in high treatments (23, 25 and 27dS [m.sup.-1]) there is no germinated seed. This phenomenon indicating soil matrix potential that aggravate water deficit when seeds put in medium that have soil particle rather than a solution by itself.
Fig 2 shows the effect of salinity treatments on germination 6 and 8 days after starting experiment. Delaying in germination with increasing salinity levels occur. Difference between number of germinated seeds after 6 and 8 days increase as the salinity increases. As the salinity levels increase, time require to seed germination increases this result is corresponded with the finding of other researchers [3, 7, 8]. In fig 3 manners of germination in four treatments control (0.005 dS [m.sup.-1]), 7, 15 and 21dS [m.sup.-1] is compared with each other. From this figure we can understand that time require reaching to maximum germination is fewer as the salinity decreases, also final number of germinated seeds at lower salinity treatments is further.
[FIGURE 1 OMITTED]
Fig 4 shows the calculated germination rate for NaCl + Ca[Cl.sub.2] solution, natural saline water and saline soil. As salinity increase, germination rate in all three environment decrease but reduction of germination rate for NaCl + Ca[Cl.sub.2] Solution is less than natural saline water and Saline Soil. Totally germination rate in solutions (NaCl + Ca[Cl.sub.2] and natural saline water) is greater than soil medium. Data shows better condition for germination in NaCl + Ca[Cl.sub.2] solution rather than natural saline water. One reason for this problem is that the ratio of Na/Ca in NaCl + Ca[Cl.sub.2] solution is lower than natural saline water. Another is due to the effect of other element presence in natural saline water and can prevent seeds from water sorption and germination, for example presence of [So.sub.4.sup.2-], B, C[O.sub.3.sup.2-] and HC[O.sub.3.sup.-] compounds that have toxicity effect. Comparison germination in artificial and natural saline solution with soil medium we can understand that although increasing salinity in solutions reduces germination, seeds in all treatments can germinated. But in soil medium seeds could germinate until treatment 23 dS [m.sup.-1] and afterward no seed germinated. This result indicates matrix potential of soil that reduces water sorption by seeds. Water adsorption in soil medium is affected by osmotic and matrix potential that any reduction in these potentials aggravates water deficiency for seeds. In solution medium the only factor that control water availability for seeds is osmotic potential, thus we can see a sharp reduction of germination rate in soil medium comparison to NaCl + Ca[Cl.sub.2] and Natural Saline Water solutions.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
Comparison seed germination in NaCl + Ca[Cl.sub.2] Solution, Natural Saline Water and Saline Soil shows that in all three medium germination decreases with increasing salinity but there is further reduction in soil medium than other two mediums. Reduction in percentage of germination in saline soil until treatment 13dS [m.sup.-1] has no significant difference with control, but afterward with increasing salinity there is sharp reduction in germination so that no seed germinated in treatment 23dS [m.sup.-1]. Generalizing results of Petri dish and growth chamber experiment to field must be perform with prudence because effective factors in soil have complicated interaction that can not be explained simply. Salinity, whether natural or induced, is a widespread environmental stress that limits the growth and development of salt-sensitive plants. Plants vary greatly in their tolerance to salts. However, the performance of crops under saline conditions depends on seed germination and establishment and also tolerance at later stages of growth.
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(1) Khosro Mohammadi and (2) Mokhtar Eskandari
(1) Agronomy Department, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran.
(2) Former MSc. Student of Soil Science, Tarbiat Modares University, Tehran, Iran.
Khosro Mohammadi and Mokhtar Eskandari: Evaluation Barley Germination in NaCl + Ca[Cl.sub.2] Solution, Natural Saline Water and Saline Soil.
Mokhtar Exkandari, Former MSc. Student of Soil Science, Tarbiat Madares University, Tehran, Iran.
Tel: +98 918 8715336
Table 1: Chemical analysis of Haoz Soltan water. pH EC [Mg.sup.2+] [Ca.sup.2+] [Na.sup.+] dS [m. g [lit.sup.-1] sup.-1] 7.25 300 22.4 1.2 115 pH [Cl.sup.-] [HCO.sub.3. [CO.sub.3. [So.sub.4. B sup.-] sup.2-] sup.2-] mg [lit.sup.-1] 7.25 161 8.6 0.0 341.5 54.8 pH [NO.sub.3 .sup.-] 7.25 2.75 Table 2: Physical and chemical analysis of Ghoinrood soil. OC EC Ca Mg P K Fe Zn pH % dS [m.sup.-1] meq [lit.sup.-1] mg [kg.sup.-1] 7.25 0.39 300 34 9.25 1.02 0.9 0.1 Mn Cu pH mg [kg.sup.-1] 7.25 1.42 0.26
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|Title Annotation:||Original Article|
|Author:||Mohammadi, Khosro; Eskandari, Mokhtar|
|Publication:||Advances in Environmental Biology|
|Date:||Sep 1, 2011|
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