Peroxidase activities of two rice cultivars differing in salinity tolerance as affected by proline and NaCl

Proline content, ion accumulation, cell wall and soluble peroxidase activities were determined in control and salt-treated calli (150 nM NaCl) and whole plants (30 mM NaCl) of two rice cultivars (salt sensitive cv. IKP and salt tolerant cv. Aiwu). Under salinity, the highest accumulation of Na⁺, Cl^? and proline occurred in calli, roots and younger leaves of cv. IKP, coupled with the highest decrease in K⁺ content; accumulations of Na⁺ and Cl^? were restricted to older leaves in cv. Aiwu. Relative growth rates of calli and roots or shoots from both cultivars were not linked to peroxidase activities. High concentrations (1 M) of exogenously applied glycerol did not inhibitin vitro activities of soluble peroxidase extracted from control and salt-treated calli or plants. Conversely, 35–55% (in cv. IKP) or 60–80% (in cv. Aiwu) of soluble peroxidase activities were found in presence of isosmotic proline concentration. There were no differences between proline and glycerol effects onin vitro cell wall peroxidase activities.     

Growth, proline accumulation and ion content in sodium chloride-stressed callus of date palm

Summary Growth and physiological responses of date palm. Phoenix dactylifera L. cv. Barhee, callus to salinity stress were examined. Callus induced from shoot tips of offshoots was cultured on Murashige and Skoog medium supplemented with NaCl at concentrations ranging from 0 to 225 mM, in consective increments of 25 mM. Data obtained after 6 wk of exposure to salt have shown a significant increase in callus proliferation in response to 25 mM NaCl the lowest level tested, beyond which callus weight decreased. At 125 mM NaCl and higher, callus growth was nearly completely inhibited. Physiological studies on callus exposed to salt stress have shown an increase in proline accumulation in response to increased salinity. Proline accumulation was correlated to callus growth inhibition. Furthermore, increasing the concentration of NaCl in the culture medium generally resulted in a steady increase in Na⁺ and reduction in K⁺ concentrations. However, at 25 mM NaCl, the only level at which callus growth was significantly enhanced, an increase in K⁺ content was noted, in comparison to the NaCl free control. In response to increasing external NaCl level, the Na⁺/K⁺ ratio increased The Na⁺/K⁺ ratio was positively correlated to proline accumulation and hence callus growth inhibition. This study provides, an understanding of the response of date palm callus to salinity, which is important for future studies aimed at developing strategies for selecting and characterizing somaclonal variants tolerant to salt stress.     

Physiological Characteristics and Alternative Respiratory Pathway under Salt Stress in Two Wheat Cultivars Differing in Salt Tolerance

Changes in respiratory pathway, dry weight, contents of proline, ATP, Na⁺and K⁺were investigated under five salinity treatments in the leaves of plants of spring wheat (Triticum aestivumL.). Two cultivars differing in salt resistance, namely, 89122 (salt-tolerant) and Longchun13 (salt-sensitive), were used. The decrease in dry weight and K⁺content was observed with the increasing NaCl concentrations, but more in cv. 89122 plants than in Longchun13 plants. Contents of proline and Na⁺in both cvs increased greatly, but the former increased more in 89122 while the latter more in Longchun13 plants. In all salinity treatments tested, a salt-induced increase in the activity of the alternative pathway was found, although cytochrome pathway (CP) still remained the main electron transport pathway. ATP production changed in parallel with CP operation. Cv. 89122 plants could produce more ATP than cv. Longchun13 plants exposed to each salinity treatment and their ATP generation could even be stimulated in contrast to its rapidly decline in Longchun13 plants with increased salinity stress. The possible relationship between respiration metabolism and above mentioned physiological changes is discussed.     

Agronomical and physiological characterization of salinity tolerance in a commercial tomato hybrid

The salt tolerance of the commercial F1 tomato hybrid (Lycopersicon esculentum Mill) Radja (GC-793) has been agronomically and physiologically evaluated under greenhouse conditions, using a control (nutrient solution), a moderate (70 mM NaCl added to the nutrient solution) and a high salt level (140 mM NaCl), applied for 130 days. The results show that Radja is a Na⁺-excluder genotype, tolerant to moderate salinity. Fruit yield was reduced by 16% and 60% and the shoot biomass by 30% and more than 75% under moderate and high salinities, respectively. At 90 days of salt treatment (DST), the mature leaves feeding the 4th truss at fruiting accumulated little Na⁺ (178 mmol kg^-1 DW). At this time, the sucrose concentration in these leaves even increased with moderate salinity and the amino acid proline was not accumulated under salt conditions as compared to control. At 130 DST, Na⁺ was accumulated mainly by the roots in proportion to the salt level applied, while in leaves appreciable amounts were found only at high salinity (452 mmol kg^-1 DW). In the leaves, Cl^- was always accumulated in proportion to the salt level and in a very much greater amounts than Na⁺ (until 1640 mmol kg^-1 DW). The sucrose content was reduced in all plants by salinity, and was distributed preferentially toward the distal stem and peduncle of a truss at fruiting under moderate salinity, and toward the basal stem and root at high salinity. Moreover, proline was accumulated in different organs of the plant only at high salinity, coinciding with Na⁺ accumulation in leaves. Attempts are made to find a clear relationship between physiological behaviour triggered by stress and the agronomical behaviour, in order to assess the validity of physiological traits used for salt-tolerance selection and breeding in tomato.     

Exogenous proline effects on water relations and ions contents in leaves and roots of young olive

The ability of exogenous compatible solutes, such as proline, to counteract salt inhibitory effects was investigated in 2-year-old olive trees (Olea europaea L. cv. Chemlali) subjected to different saline water irrigation levels supplied or not with exogenous proline. Leaf water relations [relative water content (RWC), water potential], photosynthetic activity, leaf chlorophyll content, and starch contents were measured in young and old leaves. Salt ions (Na⁺, K⁺, and Ca²⁺), proline and soluble sugars contents were determined in leaf and root tissues. Supplementary proline significantly mitigated the adverse effects of salinity via the improvement of photosynthetic activity (Pn), RWC, chlorophyll and carotenoid, and starch contents. Pn of young leaves in the presence of 25 mM proline was at 1.18 and 1.38 times higher than the values recorded under moderate (SS1) and high salinity (SS2) treatments, respectively. Further, the proline supply seems to have a more important relaxing effect on the photosynthetic chain in young than in old leaves of salt-stressed olive plants. The differential pattern of proline content between young and old leaves suggests that there would be a difference between these tissues in distinguishing between the proline taken from the growing media and that produced as a result of salinity stress. Besides, the large reduction in Na⁺ accumulation in leaves and roots in the presence of proline could be due to its interference in osmotic adjustment process and/or its dilution by proline supply. Moreover, the lower accumulation of Na⁺ in proline-treated plants, compared to their corresponding salinity treatment, displayed the improved effect of proline on the ability of roots to exclude the salt ions from the xylem sap flowing to the shoot, and thus better growth rates.     

Effects of salinity on the contents of polyamines and some other compounds in sunflower plants differing in salt tolerance

The effects of salt stress (50, 100, and 150 mM NaCl) on the levels of free, bound, and total polyamines were studied in the leaf tissues of salt-tolerant (Coban) and salt-sensitive (Sanbro) cultivars of sunflower (Helianthus annuus L.) plants grown for 15 or 25 days under salinity. The amounts of free, acid-soluble bound, and total spermine increased in leaf tissues of sunflower plants subjected to salt stress while the levels of other polyamines decreased or no significant changes occurred. The increase in some PA titers suggests their potential role in overcoming the adverse effect of salinity stress. The salt sensitivity of the sunflower plants was associated with the excessive accumulation of total polyamines in the leaf tissues of salt-sensitive cultivar (Sanbro) under saline condition. The content of other compounds such as proline, protein, and ions (Na⁺, K⁺, Cl^-, K⁺/Na⁺) in leaf tissue changed depending on salt concentration and the cultivars used.From Fiziologiya Rastenii, Vol. 52, No. 1, 2005, pp. 36–42.Original English Text Copyright © 2005 by Mutlu, Bozcuk.This article was presented by the authors in English.     

Growth and solute accumulation in 3-week-old seedlings of Agropyron elongatiun stressed with sodium and potassium salts

Agropyron elongatum [Host. (Beauv.)] [^cv. Arizona Glendale, was grown in liquid medium salinized with either NaCl, KCI, or a 50:50 mixture of these two salts at osmotic potentials ranging from 0 to –1.6 MPa. The amount of growth in 21 days was measured, and extracts were made of the shoots at this time. The extracts were assayed for low-molecular-weight organic compounds (glucose, fructose, sucrose, be-taine, proline) and inorganic solutes (Na⁺, K⁺, Cl^?, P.). The purpose was to determine if there was any correlation between the harmful effect of salinity on growth and the concentrations of solutes in tissues. Growth inhibition of A. elongatum was roughly proportional to the osmotic potential of the growth medium and was independent of the ionic composition of the salinizing salts. Total monovalent cation (the sum of Na⁺ and K⁺) concentrations and the ratio of these two cations in leaves were mainly a function of the ionic compostion of the salt in growth media, and, to a lesser degree, of osmotic potentials. F At an osmotic potential of –0.2 MPa, total monovalent cation in leaves was the same as in non-stressed plants. However, if the salinizing salt contained NaCl, there was an increase in foliar Na⁺ with a balancing decrease in K⁺. At stress levels between –0.4 and –1,6 MPa, and, if the media were salinized with either 100% NaCl or a 50:50 mixture of NaCl and KCI, total monovalent cation concentrations remained constant at a value that was twice that in non-stressed plants. Although total monovalent cation concentrations were equal in plants grown under these two salinity conditions, the K⁺/Na⁺ ratios shifted from a value of 1:2 in plants grown in 100% NaCl to 3:1 in plants subjected to the 50:50 mixture. If 100% KCI was used to salinize media, total monovalent cation was 80% of its concentration in NaCl-treated plants in the range of –0.4 to -1.2 MPa. At –1.6 MPa due to 100% KCI, total monovalent cation was double that in plants subjected to -0.4 MPa. In the range of osmotic potentials from–0.2 to –1.2 MPa, the chloride:cation ratio was 1:2. At –1.6 MPa the ratio changed to 3:4. Proline started accumulating in leaves of A. elongatum when the tissue concentration of total monovalent cation exceeded 200 μ (g fresh weight)^?1. Above this threshold value of total monovalent cation, the proline concentration of leaves was 6% of the amount of total monovalent cation that exceeded 200 umol (g fresh weight)¹.     

Salinity thresholds for understory plants in coastal wetlands

The effects of sea level rise and coastal saltwater intrusion on wetland plants can extend well above the high-tide line due to drought, hurricanes, and groundwater intrusion. Research has examined how coastal salt marsh plant communities respond to increased flooding and salinity, but more inland coastal systems have received less attention. The aim of this study was to identify whether ground layer plants exhibit threshold responses to salinity exposure. We used two vegetation surveys throughout the Albemarle-Pamlico Peninsula (APP) of North Carolina, USA to assess vegetation in a low elevation landscape (≤?3.8 m) experiencing high rates of sea level rise (3–4 mm/year). We examined the primary drivers of community composition change using Non-metric Multidimensional Scaling (NMDS) and used Threshold Indicator Taxa Analysis (TITAN) to detect thresholds of compositional change based on indicator taxa, in response to potential indicators of exposure to saltwater (Na, and the Σ Ca?+?Mg) and elevation. Salinity and elevation explained 64% of the variation in community composition, and we found two salinity thresholds for both soil Na⁺ (265 and 3843 g Na⁺/g) and Ca⁺ +?Mg⁺ (42 and 126 µeq/g) where major changes in community composition occur on the APP. Similar sets of species showed sensitivity to these different metrics of salt exposure. Overall, our results showed that ground layer plants can be used as reliable indicators of salinity thresholds in coastal wetlands. These results can be used for monitoring salt exposure of ecosystems and for identifying areas at risk for undergoing future community shifts.

     

Different mechanisms of ion homeostasis are dominant in the recretohalophyte <Emphasis Type="Italic">Tamarix ramosissima</Emphasis> under different soil salinity

Total ion (Na⁺, K⁺, Ca²⁺, SO₄ ^2? and Cl^?) accumulation by plants, ion contents in plant tissues and ion secretion by salt glands on the surface of shoots of Tamarix ramosissima adapted to different soil salinity, namely low (0.06 mmol Na⁺/g soil), moderate (3.14–4.85 mmol Na⁺/g soil) and strong (7.56 mmol Na⁺/g soil) were analyzed. There are two stages of interrelated and complementary regulation of ion homeostasis in whole T. ramosissima plants: (1) regulation of ion influx into the plant from the soil and (2) changing the secretion efficiency of salt glands on shoots. The secretion efficiency of salt glands was appraised by the ratio of ion secretion to tissue ion content. Independent of soil salinity, the accumulation of K⁺ and Ca²⁺ was higher than the contents of these ions in the soil. Furthermore, the accumulation of K⁺, Ca²⁺ and SO₄ ^2? ions by plants was maintained within a narrow range of values. Under low soil salinity, Na⁺ was accumulated, whereas under moderate and strong salinity, the influxes of Na⁺ were limited. However, under strong salinity, the accumulation of Na⁺ was threefold higher than that under low soil salinity. This led to a change in the Na⁺/K⁺ ratio (tenfold), an increase in the activity of salt glands (tenfold) and a reduction in plant growth (fivefold). An apparently high Na⁺/K⁺ ratio was the main factor determining over-active functioning of salt glands under strong salinity. Principal component analysis showed that K⁺ ions played a key role in ion homeostasis at all levels of salinity. Ca²⁺ played a significant role at low salinity, whereas Cl^? and interrelated regulatory components (K⁺ and proline) played a role under strong salinity. Proline, despite its low concentration under strong salinity, was involved in the regulation of secretion by salt glands. Different stages and mechanisms of ion homeostasis were dominant in T. ramosissima plants adapted to different levels of salinity. These mechanisms facilitated the accumulation of Na⁺ in plants under low soil salinity, the limitation of Na⁺ under moderate salinity and the over-activation of Na⁺ secretion by salt glands under strong salinity, which are all necessary for maintaining ion homeostasis and water potential in the whole plant.     

Assessment of the preventive effect of vermicompost on salinity resistance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L^??1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na⁺ concentrations, and decreased K⁺ concentrations. Salt stress decreased stomatal conductance (g_s), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (F_v/F_m), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and g_s, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na⁺ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K⁺/Na⁺ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g^??1 FW) and the highest sugar content in roots (9.2 µmol g^??1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.     

Role of Ca2+ in Drought Stress Signaling in Wheat Seedlings

Plants use complex signal transduction pathways to perceive and react to various biotic and/or abiotic stresses. As a consequence of this signaling, plants can modify their metabolism to adapt themselves to new conditions. One such change is the accumulation of proline in response to drought and salinity stresses. We have studied drought and salinity induced proline accumulation and the roles of Ca²⁺ (10 mM) and indoleacetic acid (IAA, 0.3 mM) in this response. Subjecting seedlings to both drought (6% polyethylene glycol, PEG) and salinity (150 mM NaCl) stress resulted in a dramatic increase in proline accumulation (7-fold higher than control level). However, the application of Ca²⁺ along with these stress factors had different effects. Unlike the salinity stress, Ca²⁺ prevented the drought induced proline accumulation indicating that these stress factors use distinct signaling pathways to induce similar responses. Experiments with IAA and EGTA (10 mM) supported this interpretation and suggested that Ca²⁺ and auxin participate in signaling mechanisms of drought-induced proline accumulation. Drought and salt stress-induced proline accumulation was compared on salt resistant (cv. Gerek 79) and salt sensitive (cv. Bezostaya) wheat varieties. Although proline level of the first was twofold lower than that of the second in control, relative proline accumulation was dramatically higher in the case of the salt resistant wheat variety under stress conditions.     

Changes in water relations,photosynthetic activity and proline accumulation in one-year-old olive trees (<Emphasis Type="Italic">Olea europaea</Emphasis> L. cv. Chemlali) in response to NaCl salinity

The comparative responses of young olive trees (Olea europaea L. cv “Chemlali”) to different NaCl salinity levels were investigated over 11 months. One-year-old own rooted plants were grown in 10-L pots containing sand and perlite mixture (1:3 v/v). Trees were subjected to three irrigation treatments: CP (control plants that were irrigated with fresh water); SS1 (salt stressed plants irrigated with water containing 100 mM NaCl) and SS2 plants (salt stressed plants irrigated with water containing 200 mM NaCl). Shoot elongation rate, relative water content, leaf water potential and net carbon dioxide exchange rates decreased significantly with increased NaCl salinity level. Under stressed conditions, the increase of Na⁺ and Cl⁻ ions in both leaves and roots was accompanied with that of proline and soluble sugars. The above results show that the accumulation of proline and sugars under stressed conditions could play a role in salt tolerance. The absence of toxicity symptoms under both stress treatments and the superior photosynthetic activity recorded in SS1-treated plants suggest that cv Chemlali is better able to acclimatize to 100 mM NaCl than at 200 mM NaCl. Our findings indicate that saline water containing 100 mM NaCl, the most available water in arid region in Tunisia, can be recommended for the irrigation of cv Chemlali in the arid south of Tunisia.     

Effects of salinity on uptake and distribution of Na+, Cl- and K+ in two wheat cultivars

Plants of two wheat (Triticum aestivum L.) cultivars differing in salt tolerance were grown in sand with nutrient solutions. 35-d-old plants were subjected to 5 levels of salinity created by adding NaCl, CaCl₂ and Na₂SO₄. Growth reduction caused by salinity was accompanied by increased Na⁺ and Cl^- concentrations, Na⁺/K⁺ ratio, and decreased concentration of K⁺. The salt tolerant cv. Kharchia 65 showed better ionic regulation. Salinity up to 15.7 dS m^-1 induced increased uptake of Na⁺ and Cl^- but higher levels of salinity were not accompanied by further increase in uptake of these ions. Observed increases in Na⁺ and Cl^- concentrations at higher salinities seemed to be the consequence of reduction in growth. Uptake of K⁺ was decreased; more in salt sensitive cultivar. This was also accompanied by differences in its distribution.     

Co-expression of the Arabidopsis SOS genes enhances salt tolerance in transgenic tall fescue (Festuca arundinacea Schreb.)

Crop productivity is greatly affected by soil salinity; therefore, improvement in salinity tolerance of crops is a major goal in salt-tolerant breeding. The Salt Overly Sensitive (SOS) signal-transduction pathway plays a key role in ion homeostasis and salt tolerance in plants. Here, we report that overexpression of Arabidopsis thaliana SOS1+SOS2+SOS3 genes enhanced salt tolerance in tall fescue. The transgenic plants displayed superior growth and accumulated less Na⁺ and more K⁺ in roots after 350 mM NaCl treatment. Moreover, Na⁺ enflux, K⁺ influx, and Ca²⁺ influx were higher in the transgenic plants than in the wild-type plants. The activities of the enzyme superoxide dismutase, peroxidase, catalase, and proline content in the transgenic plants were significantly increased; however, the malondialdehyde content decreased in transgenic plants compared to the controls. These results suggested that co-expression of A. thaliana SOS1+SOS2+SOS3 genes enhanced the salt tolerance in transgenic tall fescue.     

Control of xylem Na+ loading and transport to the shoot in rice and barley as a determinant of differential salinity stress tolerance

Control of xylem Na⁺ loading has often been named as the essential component of salinity tolerance mechanism. However, it is less clear to what extent the difference in this trait may determine differential salinity tolerance between species. In this study, barley (Hordeum vulgare L. cv. CM72) and rice (Oryza sativa L. cv. Dongjin) plants were grown under two levels of salinity. Na⁺ and K⁺ concentrations in the xylem sap, and shoot and root tissues were measured at different time points after stress onset. Salt‐exposed rice plants prevented xylem Na⁺ loading for several days, but failed to control this process in the longer term, ultimately resulting in a massive Na⁺ shoot loading. Barley plants quickly increased xylem Na⁺ concentration and its delivery to the shoot (most likely for the purpose of osmotic adjustment) but were able to reduce this process later on, keeping most of accumulated Na⁺ in the root, thus maintaining non‐toxic shoot Na⁺ level. Rice plants increased shoot K⁺ concentration, while barley plants maintained higher root K⁺ concentration. Control of xylem Na⁺ loading is remarkably different between rice and barley; this difference may differentiate the extent of the salinity tolerance between species. This trait should be investigated in more detail to be used in the breeding programs aimed to improve salinity tolerance in crops.     

Cation co-tolerance phenomenon in cell cultures of Oryza sativa adapted to LiCl and NaCl

Cell lines of Oryza sativa L. (cv. Taipei-309) were adapted to 30 mM LiCl and 150 mM NaCl. Both adapted lines were considerably more tolerant than non adapted line when grown on 200, 250 and 300 mM NaCl and 30 mM LiCl stresses. The tolerance of LiCl-adapted line to NaCl (150 to 300 mM) and the tolerance of NaCl-adapted cells line to LiCl (30 mM) indicated that there was a cross-adaptation towards alkali metals (Na⁺ and Li⁺) not the Cl^–. Na⁺ and K⁺ contents of all lines which increased with increasing medium salinity but to a different degree. The increase in Na⁺ and K⁺ content in NaCl-adapted and non-adapted lines were comparable, while LiCl-adapted line accumulated significantly lower Na⁺and higher K⁺ content. Proline content of all lines increased with the increase in NaCl-stress but the magnitude of increase was much higher in the LiCl-adapted than other lines. The differential response of adapted lines to NaCl stress in accumulating proline and maintaining the ionic contents reveals that adapted lines have evolved different features of adaptation to cope with NaCl stress.     

Different responses of two ecotypes of C<Subscript>3</Subscript>–C<Subscript>4</Subscript> xero-halophyte <Emphasis Type="Italic">Bassia sedoides</Emphasis> to osmotic and ionic factors of salt stress

The effects of low and moderate salinity (100 and 200 mM NaCl, respectively) and iso-osmotic stress generated by polyethylene glycol PEG (1) (–0.3 MPa) and PEG (2) (–0.6 MPa) on maximum quantum yield of photosystem II (PSII), growth, photosynthesis, transpiration, dark respiration, water use efficiency (WUE), water content, chlorophyll, proline, Na⁺ and K⁺ concentrations were investigated in shoots of two ecotypes С₃–С₄ xero-halophyte Bassia sedoides (Pall.) Aschers. Plants were grown from seeds of two Southern Urals populations (Makan and Podolsk) differing in their bioproductivity. Aboveground biomass of the Makan plants was approximately 10-fold higher than that of the Podolsk ecotype. The plants of both ecotypes were sensitive to water deficit. They showed similar decrease in biomass, water content, net photosynthesis and transpiration intensity under both low and moderate osmotic stress (PEG). However, the content of сhlorophyll and free proline in shoots of the Podolsk plants increased under moderate osmotic stress (PEG(2)). Under salinity the differences between transpiration, F_v/F_m, WUE, water content, chlorophyll and proline concentrations in shoots of two ecotypes were no found. But, the Podolsk plants showed decrease in the growth parameters (1.5-fold), increase in the dark respiration intensity (2-fold) and the Na⁺/K⁺ ratio (1.2-fold) under moderate salinity (200 mM NaCl). Thus, the reduction of bioproductivity of the Podolsk ecotype under salinity was the result of ionic rather than osmotic factor of salinity. In the Podolsk plants the additional transpiration costs and consumption of assimilates (correspondingly) increased with the toxic sodium ion accumulation under salinity. This led to decrease in the growth parameters. Thus, two B. sedoides ecotypes have different adaptive strategies of tolerance to the ionic factor of salt stress at the level of the physiological processes associated with the dark CO₂ gas exchange. Moreover, in less tolerant and productive Podolsk ecotype the increase in proline content in shoots characterized comparatively low adaptation to osmotic factor, and the increase in dark respiration and the Na⁺/K⁺ ratio pointed to relatively low resistance to ion factor of salinity as compared with the Makan ecotype.     

<i>Azospirillum brasilense</i> and <i>Saccharomyces cerevisiae</i> as Alternative for Decrease the Effect of Salinity Stress in Tomato (<i>Lycopersicon esculentum</i>) Growth

The salinity stress is one of the most relevant abiotic stresses that affects the agricultural production. The present study was performed to study the improvement of the salt tolerance of tomato plants which is known for their susceptibility to salt stress. The present study aimed to assess to what extent strain Azospirillum brasilense (N040) and Saccharomyces cerevisiae improve the salt tolerance to tomato plants treated with different salt concentration. The inoculant strain A. brasilense (N040) was previously adapted to survive up to 7% NaCl in the basal media. A greenhouse experiment was conducted to evaluate the effect of this inoculation on growth parameter such as: plant height, root length, fresh and dry weight, fruits fresh weight, chlorophyll content, proline and total soluble sugar in tomato plants under salt stress condition. The results revealed that co-inoculation of Azospirillum brasilense (N040) and Saccharomyces cerevisiae significantly increased the level of proline (8.63 mg/g FW) and total soluble sugar (120 mg/g FW) of leaves under salinity condition comparing to non-inoculated plants (2.3 mg/g FW and 70 mg/g FW, respectively). Plants co-inoculated with adapted strain of A. brasilense and S. cerevisiae showed the highest significant (p < 0.01) increase in fruit yield (1166.6 g/plant), plant high (115 cm) and roots length (52.6) compared whit un-inoculated control plants (42 g/pant, 43.3 cm and 29.6 cm, respectively). In contrast, Na⁺ ion content was significantly decreased in the leaves of salt stressed plants treated with the A. brasilense (N040) and S. cerevisiae. Finally, the results showed that dual benefits provided by both A. brasilense (N040) and S. cerevisiae can provide a major way to improve tomato yields in saline soils.