Salt-induced changes in photosynthetic activity and growth in a potential medicinal plant Bishop’s weed (Ammi majus L.)

Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50 % reduction in shoot dry mass occurred at 156 mM (ca.15.6 mS cm^–1), whereas that in seed yield was at 104 mM (ca.10.4 mS cm^–1). As in most glycophytes, Na⁺ and Cl^– in both shoots and roots increased, whereas K⁺ and Ca²⁺ decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majusmaintained markedly higher K⁺/Na⁺ ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (P_N) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majusis a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K⁺/Na⁺ ratio and accumulation of proline in shoots, but P_N had a negative association with the salt tolerance of this crop.This revised version was published online in March 2005 with corrections to the page numbers.     

Restoration of Growth of Durum Wheat (Triticum durum var. waha) Under Saline Conditions Due to Inoculation with the Rhizosphere Bacterium Azospirillum brasilense NH and Extracts of the Marine Alga Ulva lactuca

Inoculation with the rhizosphere bacterium Azospirillum brasilense NH, originally isolated from salt-affected soil in northern Algeria, greatly enhanced growth of durum wheat (Triticum durum var. waha) under saline soil conditions. Important plant parameters like the rate of germination, stem height, spike length, dry weight of roots and shoots, chlorophyll a and b content, proline and total sugar contents, 1000-seed weight, seed number per spike, and weight of seeds per spike were measured. At salt stress conditions (160 and 200 mM NaCl) A. brasilense NH restored almost completely vegetative growth and seed production. The combination with extracts of the marine alga Ulva lactuca resulted in even more improved salt tolerance of durum wheat. Proline and total sugar accumulation, a sign of physiological plant stress under inhibitory salt conditions, was reduced in plants inoculated with A. brasilense NH with and without addition of algal extracts. Inoculation with the salt-sensitive A. brasilense strain Sp7 could not restore salt-affected plant growth at 200 mM NaCl. Furthermore, it could be demonstrated by fluorescence in situ hybridization and confocal laser scanning microscopy that A. brasilense NH is able to colonize roots of durum wheat endophytically under salt-stressed conditions. Thus, the salt-tolerant rhizobacterium A. brasilense NH could effectively provide alone or in combination with extracts of U. lactuca a promising solution to overcome salt inhibition which is a major threat hindering productive wheat cultivation in arid saline soils.     

Potassium nitrate application alleviates sodium chloride stress in winter wheat cultivars differing in salt tolerance

A sand culture experiment was conducted to answer the question whether or not exogenous KNO(3) can alleviate adverse effects of salt stress in winter wheat by monitoring plant growth, K(+)/Na(+) accumulation and the activity of some antioxidant enzymes. Seeds of two wheat cultivars (CVs), DK961 (salt-tolerant) and JN17 (salt-sensitive), were planted in sandboxes and controls germinated and raised with Hoagland nutrient solution (6 mM KNO(3), no NaCl). Experimental seeds were exposed to seven modified Hoagland solutions containing increased levels of KNO(3) (11, 16, 21 mM) or 100 mM NaCl in combination with the four KNO(3) concentrations (6, 11, 16 and 21 mM). Plants were harvested 30 d after imbibition, with controls approximately 22 cm in height. Both CVs showed significant reduction in plant height, root length and dry weight of shoots and roots under KNO(3) or NaCl stress. However, the combination of increased KNO(3) and NaCl alleviated symptoms of the individual salt stresses by improving growth of shoots and roots, reducing electrolyte leakage, malondialdehyde and soluble sugar contents and enhancing the activities of antioxidant enzymes. The salt-tolerant cultivar accumulated more K(+) in both shoots and roots compared with the higher Na(+) accumulation typical for the salt-sensitive cultivar. Soluble sugar content and activities of antioxidant enzymes were found to be more stable in the salt-tolerant cultivar. Our findings suggest that the optimal K(+)/Na(+) ratio of the nutrient solution should be 16:100 for both the salt-tolerant and the salt-sensitive cultivar under the experimental conditions used, and that the alleviation of NaCl stress symptoms through simultaneously applied elevated KNO(3) was more effective in the salt-tolerant than in the salt-sensitive cultivar.     

Salt-induced changes in photosynthetic activity and growth in a potential medicinal plant Bishop’s weed (<Emphasis Type="Italic">Ammi majus</Emphasis> L.)

Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50 % reduction in shoot dry mass occurred at 156 mM (ca.15.6 mS cm^?1), whereas that in seed yield was at 104 mM (ca.10.4 mS cm^?1). As in most glycophytes, Na⁺ and Cl^? in both shoots and roots increased, whereas K⁺ and Ca²⁺ decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majusmaintained markedly higher K⁺/Na⁺ ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (P_N) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majusis a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K⁺/Na⁺ ratio and accumulation of proline in shoots, but P_N had a negative association with the salt tolerance of this crop.     

Salt sensitivity of the vegetative and reproductive stages in chickpea (Cicer arietinum L.): Podding is a particularly sensitive stage

Soil salinity is an increasing problem, including in regions of the world where chickpea is cultivated. Salt sensitivity of chickpea was evaluated at both the vegetative and reproductive phase. Root-zone salinity treatments of 0, 20, 40 and 60 mM NaCl in aerated nutrient solution were applied to seedlings or to older plants at the time of flower bud initiation. Even the reputedly tolerant cultivar JG11 was sensitive to salinity. Plants exposed to 60 mM NaCl since seedlings, died by 52 d without producing any pods; at 40 mM NaCl plants died by 75 d with few pods formed; and at 20 mM NaCl plants had 78-82% dry mass of controls, with slightly higher flower numbers but 33% less pods. Shoot Cl exceeded shoot Na by 2-5 times in both the vegetative and reproductive phase, and these ions also entered the flowers. Conversion of flowers into pods was sensitive to NaCl. Pollen from salinized plants was viable, but addition of 40 mM NaCl to an in vitro medium severely reduced pollen germination and tube growth. Plants recovered when NaCl was removed at flower bud initiation, adding new vegetative growth and forming flowers, pods and seeds. Our results demonstrate that chickpea is sensitive to salinity at both the vegetative and reproductive phase, with pod formation being particularly sensitive. Thus, future evaluations of salt tolerance in chickpea need to be conducted at both the vegetative and reproductive stages.     

Salinity stress response of non-transformed and AtCKX transgenic centaury (Centaurium erythraea Rafn.) shoots and roots grown in vitro

Common centaury (Centaurium erythraea Rafn.) is a plant species that can inhabit saline soils. It is known as a plant with high spontaneous regeneration potential in vitro. In the present work we evaluated shoots and roots salinity tolerance of non-transformed and three AtCKX transgenic centaury lines to graded NaCl concentrations (0, 50, 100, 150, 200 mM) in vitro. Overexpression of AtCKX genes in transgenic centaury plants resulted in an altered cytokinins (CKs) profile leading to a decline of bioactive CK levels and, at the same time, increased contents of storage CK forms, inactive CK forms and/or CK nucleotides. Significant increment of fresh shoot weight was obtained in shoots of non-transformed and AtCKX1 transgenic line only on medium supplemented with 50 mM NaCl. However two analysed AtCKX2 transgenic lines reduced shoot growth at all NaCl concentrations. In general, centaury roots showed higher tolerance to salinity than shoots. Non-transformed and AtCKX1 transgenic lines tolerated up to 100 mM NaCl without change in frequency of regeneration and number of regenerated plants. Roots of two analysed AtCKX2 transgenic lines showed different regeneration potential under salt stress. Regeneration of transgenic AtCKX2-26 shoots even at 200 mM NaCl was recorded. Salinity stress response of centaury shoots and roots was also evaluated at biochemical level. Free proline, malondialdehyde and hydrogen peroxide content as well as antioxidative enzymes activities were investigated in shoots and roots after 1, 2, 4 and 8 weeks. In general, adition of NaCl in culture medium elevated all biochemical parameters in centaury shoots and in roots. Considering that all analysed AtCKX transgenic centaury lines showed altered salt tolerance to graded NaCl concentrations in vitro it can be assumed that CKs might be involved in plant defence to salt stress conditions.     

Development changes in calla lily plants due to salt stress

Soil salinity is mainly caused by excessive use of fertilizers and the use of poor quality water, and adversely affected crop growth especially when grown in protected environments. Soil salinity causes salt stress in plants, which inhibits plant growth, leading to morphological, metabolic and physiological changes. Though it is a major problem occurs more frequently, there is less information on the behavior of calla lily (Zantedeschia aethiopica) under these conditions, and most studies are conducted with other species of the genus Zantesdeschia. Therefore, this study aimed to evaluate ecophysiological, biochemical and anatomical growth responses of calla lily plants to salt stress. Rhizomes were grown in trays containing coconut fiber as a substrate and treated with 0, 25, 50, 75 and 100 mM NaCl to induce stress. A decrease in plant height was observed, as well as in the number of tillers and leaves, main root length, fresh and dry matter of the shoot and root system. A reduction in photosynthetic rate, stomatal conductance and transpiration rate was observed at 60 days. However, after 90 days, the photosynthetic rate was unchanged, with increased stomatal conductance and transpiration rate for plants exposed to 75 mM NaCl. Salt stress caused a higher accumulation of carbohydrates in shoots and roots. Thus, high concentrations of NaCl affect the development of calla lily, indicating that this species is susceptible to salt stress.     

Accumulation and distribution of Zn in the shoots and reproductive structures of the halophyte plant species Kosteletzkya virginica as a function of salinity

Kosteletzkya virginica is a wetland halophyte that is a good candidate for rehabilitation of degraded salt marshes and production of oil as biodiesel. Salt marshes are frequently contaminated by heavy metals. The distribution of Zn in vegetative and reproductive organs of adult plants, and the NaCl influence on this distribution remain unknown and were thus explored in the present study. Plants were cultivated in a nutrient film technique system, from seedling stage until seed maturation in a control, Zn (100 μM), NaCl (50 mM) or Zn + NaCl medium. Photosynthesis, ion nutrition, malondialdehyde and non-protein thiol concentrations were quantified. Zinc distribution in reproductive organs was estimated by a laser ablation-inductively coupled plasma-mass spectrometry procedure (LA-ICP-MS). Adult plants accumulated up to 2 mg g^?1 DW Zn in the shoots. Zinc reduced plant growth, inhibited photosynthesis and reduced seed yield. Zinc accumulation in the seeds was only two times higher in Zn-treated plants than in controls. Exogenous NaCl neutralized the damaging action of Zn and modified the Zn distribution through a preferential accumulation of toxic ions in older leaves. Zinc was present in seed testa, endosperm and, to a lower extent, in embryo. Additional NaCl induced a chalazal retention of Zn during seed maturation and reduced final Zn seed content. It is concluded that NaCl 50 mM had a positive impact on the response of K. virginica to Zn toxicity and acts through a modification in Zn distribution rather than a decrease in Zn absorption.     

5-Aminolevulinic acid improves photosynthetic gas exchange capacity and ion uptake under salinity stress in oilseed rape (Brassica napus L.)

Salinity is one of the major constraints in oilseed rape (Brassica napus L.) production. One of the means to overcome this constraint is the use of plant growth regulators to induce plant tolerance. To study the plant response to salinity in combination with a growth regulator, 5-aminolevulinic acid (ALA), oilseed rape plants were grown hydroponically in greenhouse conditions under three levels of salinity (0, 100, and 200 mM NaCl) and foliar application of ALA (30 mg/l). Salinity depressed the growth of shoots and roots, and decreased leaf water potential and chlorophyll concentration. Addition of ALA partially improved the growth of shoots and roots, and increased the leaf chlorophyll concentrations of stressed plants. Foliar application of ALA also maintained leaf water potential of plants growing in 100 mM salinity at the same level as that of the control plants, and there was also an improvement in the water relations of ALA-treated plants growing in 200 mM. Net photosynthetic rate and gas exchange parameters were also reduced significantly with increasing salinity; these effects were partially reversed upon foliar application with ALA. Sodium accumulation increased with increasing NaCl concentration which induced a complex response in the macro-and micronutrients uptake and accumulation in both roots and leaves. Generally, analyses of macro- (N, P, K, S, Ca, and Mg) and micronutrients (Mn, Zn, Fe, and Cu) showed no increased accumulation of these ions in the leaves and roots (on dry weight basis) under increasing salinity except for zinc (Zn). Foliar application of ALA enhanced the concentrations of all nutrients other than Mn and Cu. These results suggest that under short-term salinity-induced stress (10 days), exogenous application of ALA helped the plants improve growth, photosynthetic gas exchange capacity, water potential, chlorophyll content, and mineral nutrition by manipulating the uptake of Na⁺.     

Selection of a NaCl-tolerant Citrus plant

Summary The objective of the work was to select Citrus plants more tolerant to elevated NaCl concentrations in the irrigation water. For this purpose, unfertilized Troyer citrange ovules treated with a chemical mutagenic agent (ethyl methane sulphonate) were cultured in vitro. Whole plants were regenerated from embryos developed in the nucellar tissue of the ovule. The screening for salt tolerance was achieved by irrigating these plants with a nutrient solution containing 45 mM NaCl.Plants obtained from vegetative propagation of the selected plant show faster growth, less leaf damage and lower concentrations of Cl^– and Na⁺ in leaves than the original clone with increasing NaCl levels in the nutrient solution. In addition, the selected plant accumulated more Na⁺ in shoots and roots and this was accompanied by a significant reduction in K⁺concentration. It can be concluded that the selected plant restricts the accumulation of Na⁺ in leaves by concentrating Na⁺ in shoots and roots.Abbreviations EMS ethyl-methane-sulphonate - IBA indole 3-butyric acid     

Nutrient uptake and management under saline conditions in the xerohalophyte: Tecticornia indica (Willd.) subsp. indica

In the present investigation, we studied uptake and management of the major cations in the xerohalophyte, Tecticornia indica (Willd.) subsp. indica as subjected to salinity. Plants were grown under greenhouse conditions at various salinity levels (0, 100, 200 and 400 mM NaCl) over 110 days. At harvest, they were separated into shoots and roots then analyzed for water contents, dry weights (DW), and Na+, K+, Ca2+, and Mg2+ contents. Plants showed a growth optimum at 200 mM NaCl and much better tissue hydration under saline than non-saline conditions. At this salt concentration (200 mM NaCl), shoot Na+ content reached its highest value (7.9 mmol · g-?1 DW). In spite of such stressful conditions, salt-treated plants maintained adequate K+, Ca2+, and Mg2+ status even under severe saline conditions. This was mainly due to their aptitude to selectively acquire these essential cations and efficiently use them for biomass production.     

Overexpression of <Emphasis Type="Italic">TaNHX2</Emphasis> enhances salt tolerance of ‘composite’ and whole transgenic soybean plants

Salinity is a major factor resulting in extensive loss of agricultural production. Genetic transformation has become a powerful tool for studying gene function and for improving crop salt tolerance. In this study, a TaNHX2 gene was transformed into a plant cloning vector under the control of cauliflower mosaic virus 35S promoter, and then introduced into Agrobacterium rhizogenes strain K599. Explants of soybean were transformed with A. rhizogenes and ‘composite’ plants consisting of wild-type shoots and transgenic hairy roots overexpressing TaNHX2 were produced. When exposed to salt stress, ‘composite’ plants displayed high salinity tolerance at 171 mM NaCl in vermiculite and in solid medium supplemented with up to 200 mM NaCl, whereas control plants displayed chlorosis and died within 15 days under above treatment conditions. We subsequently obtained soybean plants overexpressing TaNHX2 through A. tumefaciens-mediated transformation and studied four homozygous lines of TaNHX2. Transgenic lines displayed an enhanced salt tolerance in plant biomass and flower number per plant, compared with wild type plants grown on sand culture containing 150 mM NaCl. Furthermore, transgenic plants of line C12-11 showed longer survival, less growth inhibition and greater number of flowers than wild type plants. Taken together, these results indicated that TaNHX2 gene could enhance salt tolerance of soybean, and A. rhizogenes-mediated transformation system could be used as a complementary tool of A. tumerfaciens-mediated transformation to rapidly investigate candidate gene function in soybean.     

Boron and calcium increasePisum sativum seed germination and seedling development under salt stress

A beneficial effect of B and Ca application on symbiotic interaction between legume and rhizobia under saline conditions has recently been shown, suggesting conventional agricultural practices to increase crop salt tolerance. However, nothing is known about application of both nutrients on early events of legume development under salt stress, prior to the establishment of a symbiotic interaction. Therefore, the effects of different levels of B (from 9.3 to 93μM B) and Ca (from 0.68 to 5.44 mM Ca) on seed germination, root elongation, plant development, and mineral composition of pea (Pisum sativum L. cv. Argona) grown under 0 to 150 mM NaCl, were analysed. Development of plants previously germinated in the presence of salt was more impaired than that of plants put under salt stress once seeds were germinated. A NaCl concentration of 75 mM and 150 mM inhibited pea seed germination and seedling growth. The addition of either extra B or extra Ca to the germination solution prevented the reduction caused by 75 mM NaCl but not that of 150 mM NaCl. However, root elongation and plant development under salt stress (75 mM NaCl) was enhanced only by addition of both B and Ca. When plants were cultivated in the absence of external N, N content in roots and shoots originating from seeds was diminished by salt and enhanced by B and Ca, suggesting a role of these nutrients in remobilisation of seed nutrient stores. Salinity also led to an extremely high concentration of Na⁺ ions, and to a decrease of B and Ca concentrations. This can be overcome by addition of both nutrients, increasing salt tolerance of developing pea plants. The necessity of nutritional studies to increase crop production in saline soils is discussed and proposed.     

Responses of grass pea seedlings to salinity stress in in vitro culture conditions

Physiological and molecular mechanisms of adaptation to abiotic stresses of grass pea (Lathyrus sativus L.) are still poorly understood. Responses of four genotypes of grass pea to salinity stress in tissue culture conditions were investigated at early seedling growth stages. Salinity stress was induced in the agar media by adding 0, 50, 100 and 200 mM of NaCl. Germination and seedling emergence percentage was not significantly affected by 50 and 100 mM of NaCl. However, NaCl in 200 mM concentration lowered level of these parameters. Generally, exposure to NaCl stress significantly reduced length of grass pea seedling organs (root and shoot) but did not influence the content of dry weight in shoots and increased it in the roots in two cases. Increasing salt concentration decreased integrity of cellular membranes both in root and shoot tissues. Higher accumulation of phenolic compounds and significant changes in activity of antioxidant enzymes (peroxidase and catalase) were observed in the roots but not in the shoots. Similarly, the content of proline increased mostly in the roots from moderate (100 mM) salinity conditions. Adverse conditions did not resulted in alterations in photosynthetic pigments content of any tested genotypes. The better performance of shoots than roots may result from in vitro conditions in which experiments were conducted.

     

Effects of NaCl and Na2SO4 on red-osier dogwood (Cornus stolonifera Michx) seedlings

Sodium chloride and sodium sulfate are commonly present in extraction tailings waters produced as a result of surface mining and affect plants on reclaimed areas. Red-osier dogwood (Cornus stolonifera Michx) seedlings were demonstrated to be relatively resistant to these high salinity oil sands tailings waters. The objectives of this study were to compare the effects of Na₂SO₄ and NaCl, on growth, tissue ion content, water relations and gas exchange in red-osier dogwood (Cornus stolonifera Michx) seedlings. In the present study, red-osier dogwood seedlings were grown in aerated half-strength modified Hoagland's mineral solution containing 0, 25, 50 or 100 mM of NaCl or Na₂SO₄. After four weeks of treatment, plant dry weights decreased and the amount of Na⁺ in plant tissues increased with increasing salt concentration. Na⁺ tissue content was higher in plants treated with NaCl than Na₂SO₄ and it was greater in roots than shoots. However, Cl^– concentration in the NaCl treated plants was higher in shoots than in roots. The decrease in stomatal conductance and photosynthetic rates observed in presence of salts is likely to contribute to the growth reduction. Our results suggest that red-osier dogwood is able to control the transport of Na⁺ from roots to shoots when external concentrations are 50 mM or less.     

Role of Salicylic Acid in Promoting Salt Stress Tolerance and Enhanced Artemisinin Production in Artemisia annua L.

In the present investigation, the role of salicylic acid (SA) in inducing salinity tolerance was studied in Artemisia annua L., which is a major source of the antimalarial drug artemisinin. SA, when applied at 1.00 mM, provided considerable protection against salt stress imposed by adding 50, 100, or 200 mM NaCl to soil. Salt stress negatively affected plant growth as assessed by length and dry weight of shoots and roots. Salinity also reduced the values of photosynthetic attributes and total chlorophyll content and inhibited the activities of nitrate reductase and carbonic anhydrase. Furthermore, salt stress significantly increased electrolyte leakage and proline content. Salt stress also induced oxidative stress as indicated by the elevated levels of lipid peroxidation compared to the control. A foliar spray of SA at 1.00 mM promoted the growth of plants, independent of salinity level. The activity of antioxidant enzymes, namely, catalase, peroxidase, and superoxide dismutase, was upregulated by salt stress and was further enhanced by SA treatment. Artemisinin content increased at 50 and 100 mM NaCl but decreased at 200 mM NaCl. The application of SA further enhanced artemisinin content when applied with 50 and 100 mM NaCl by 18.3 and 52.4%, respectively. These results indicate that moderate saline conditions can be exploited to obtain higher artemisinin content in A. annua plants, whereas the application of SA can be used to protect plant growth and induce its antioxidant defense system under salt stress.     

Effects of silicon on photosynthesis,water relations and nutrient uptake of <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> under NaCl stress

A greenhouse experiment was conducted to investigate the effects of silicon application on Phaseolus vulgaris L. under two levels of salt stress (30 and 60 mM NaCl in the irrigation water). Salinity significantly reduced growth, stomatal conductance and net photosynthetic rate, and increased Na⁺ and Cl⁻ content mainly in roots. Silicon application enhanced growth of salt stressed plants, significantly reduced Na⁺ content especially in leaves and counterbalanced the effects of NaCl on gas exchange; the effect was more evident at 30 mM NaCl. Cl⁻ content in shoots and roots was not significantly modified by silicon application; the drop in K⁺ content caused by salinity was partially counterbalanced by silicon, especially in roots.     

Response of barley grains to the interactive e.ect of salinity and salicylic acid

Effect of grain soaking presowing in 1 mM salicylic acid (SA) and NaCl (0, 50, 100, 150 and 200 mM) on barley (Hordeum vulgare cv Gerbel) was studied. Increasing of NaCl level reduced the germination percentage, the growth parameters (fresh and dry weight), potassium, calcium, phosphorus and insoluble sugars content in both shoots and roots of 15-day old seedlings. Leaf relative water content (RWC) and the photosynthetic pigments (Chl a, b and carotenoids) contents also decreased with increasing NaCl concentration. On the other hand, Na, soluble sugars, soluble proteins, free amino acids including proline content and lipid peroxidation level and peroxidase activity were increased in the two plant organs with increasing of NaCl level. Electrolyte leakage from plant leaves was found to increase with salinity level. SA-pretreatment increased the RWC, fresh and dry weights, water, photosynthetic pigments, insolube saccharides, phosphorus content and peroxidase activity in the stressed seedlings. On the contrary, Na⁺, soluble proteins content, lipid peroxidation level, electrolyte leakage were markedly reduced under salt stress with SA than without. Under stress conditions, SA-pretreated plants exhibited less Ca²⁺ and more accumulation of K⁺, and soluble sugars in roots at the expense of these contents in the plant shoots. Exogenous application (Grain soaking presowing) of SA appeared to induce preadaptive response to salt stress leading to promoting protective reactions to the photosynthetic pigments and maintain the membranes integrity in barley plants, which reflected in improving the plant growth.     

Salt effects on the growth, mineral nutrition, essential oil yield and composition of marjoram (Origanum majorana)

The aim of this work was to investigate the growth, mineral nutrition and essential oil composition of marjoram aerial part. Seedlings were cultivated for 20 days on nutrient solution, and then transferred to hydroponic solution with different NaCl concentrations (0, 50, 100, 150 mM). Plants were harvested after 17 days of treatment. Mineral nutrition and essential oil composition of shoots were determined. Results showed that growth, water content and development of the different organs of marjoram plant were affected just at the highest NaCl concentration (150 mM). Furthermore, salt did not seem to affect leaf area and root length but reduced the number of leaves. An increase in the total leaf surface and its thickness was observed at different NaCl concentrations. At 50 mM NaCl, sodium was primarily accumulated in roots but at 150 mM, it was strongly accumulated in leaves. However, Cl^? accumulation was lower at higher NaCl concentrations. Essential oil yield of marjoram shoots was 0.12% in the control and 0.10% at 50 mM but an important decrease was observed at 100 mM (0.05%). Thirty-three components were identified belonging to different chemical classes. In the control, the essential oil was found to be rich in trans-sabinene hydrate (47.67%), terpinen-4-ol (20.82%) and cis-sabinene hydrate (7.23%). The proportions of these main compounds were differently affected by salt.     

Isolated Thellungiella shoots do not require roots to survive NaCl and Na2SO4 salt stresses

Shoots of Thellungiella derived by micropropagation were used to estimate the plants'' salt tolerance and ability to regulate Na⁺ uptake. Two species with differing salt tolerances were studied: Thellungiella salsuginea (halophilla), which is less tolerant, and Thellungiella botschantzevii, which is more tolerant. Although the shoots of neither ecotype survived at 700 mM NaCl or 200 mM Na₂SO₄, micropropagated shoots of T. botschantzevii were more tolerant to Na₂SO₄ (10–100 mM) and NaCl (100–300 mM). In the absence of roots, Na₂SO₄ salinity reduced shoot growth more dramatically than NaCl salinity. Plantlets of both species were able to adapt to salt stress even when they did not form roots. First, there was no significant correlation between Na⁺ accumulation in shoots and Na⁺ concentration in the growth media. Second, K⁺ concentrations in the shoots exposed to different salt concentrations were maintained at equivalent levels to control plants grown in medium without NaCl or Na₂SO₄. These results suggest that isolated shoots of Thellungiella possess their own mechanisms for enabling salt tolerance, which contribute to salt tolerance in intact plants.Key words: Thellungiella salsuginea, Thellungiella botschantzevii, salt tolerance, isolated shoots, growth, rhizogenesis, ion accumulation