Physiological responses and adaptive strategies of wheat seedlings to salt and alkali stresses

Abstract

Effects of salt (NaCl?:?Na₂SO₄) and alkali (NaHCO₃?:?Na₂CO₃) stresses on the contents of inorganic ions and organic solutes in wheat shoots were compared to explore the physiological responses and adaptive strategies of wheat to these stresses. Wheat significantly accumulated Na⁺ and simultaneously accumulated Cl^?, soluble sugars and proline to maintain osmotic and ionic balance under salt stress. Compared with salt stress, the high pH from alkali stress enhanced Na⁺ accumulation and affected the absorption of inorganic anions. To maintain ionic and osmotic balance, wheat accumulated organic acids, soluble sugars and proline. The accumulation of Cl^? and organic acids was the main difference in the physiological responses and adaptive mechanisms to salt and alkali stresses, respectively.     

COMPARISON OF OSMOTIC REGULATION IN DEHYDRATION- AND SALINITY-STRESSED SUNFLOWER SEEDLINGS

Plant dry matter accumulation rate (DMAR), relative water content (RWC), electrolyte leakage percentage (ELP), chlorophyll content, osmotic adjustment ability (OAA), and osmotica accumulation in leaves of sunflower (Helianthus annuus L.) seedlings under different levels of dehydration and salinity stress induced by iso-osmotic PEG (polyethylene glycol) or sodium chloride (NaCl) were evaluated. Plants were subjected to four stress treatments for 10 days: ?0.44 MPa PEG6000, ?0.44 MPa NaCl, ?0.88 MPa PEG6000, ?0.88 MPa NaCl. Results showed that PEG and NaCl treatments decreased the plant's DMAR and RWC, and NaCl treatments had more severe inhibitory effect on the plants than PEG treatments. Leaf ELP in sunflower seedlings increased after NaCl and PEG treatments. However, leaf ELP under salt stress was higher than that under dehydration stress (PEG treatment). All stress treatments increased OAA in plant leaves. Leaf OAA was enhanced significantly as PEG concentration increases, while leaf OAA was less enhanced at higher concentration of NaCl. OAA of sunflower leaves under dehydration stress was due to an increase in potassium (K⁺), calcium (Ca²⁺), amino acid, organic acid, magnesium (Mg²⁺), and proline content. OAA of sunflower leaves under moderate salt stress was owing to an increase in K⁺, chlorine (Cl^?), amino acid, organic acid, sodium (Na⁺), and proline content, and was mainly due to an accumulation of K⁺, Cl^?, Na⁺, and proline under severe salt stress.     

CONTRIBUTION OF PROLINE AND INORGANIC SOLUTES TO OSMOTIC ADJUSTMENT IN COTTON UNDER SALT STRESS

Physiological responses to salt stress were investigated in two cotton (Gossypium hirsutum L.) cultivars (Pora and Guazuncho) grown hydroponically under various concentrations of NaCl. Dry matter partitioning, plant water relations, mineral composition and proline content were studied. Proline and inorganic solutes were measured to determine their relative contribution to osmotic adjustment. Both leaf water potential (Ψ_w) and osmotic potential (Ψ_s)decreased in response to NaCl levels. Although Ψ_wand Ψ_s decreased during salt stress, pressure potential Ψ_p remained between 0.5 to 0.7 MPa in control and all NaCl treatments, even under 200 mol m^?3 NaCl. Increased NaCl levels resulted in a significant decrease in root, shoot and leaf growth biomass. Root / shoot ratio increased in response to salt stress. The responses of both cultivars to NaCl stress were similar. Increasing salinity levels increased plant Na⁺ and Cl^?. Potassium level remained stable in the leaves and decreased in the roots with increasing salinity. Salinity decreased Ca²⁺ and Mg²⁺ concentrations in leaves but did not affect the root levels of these nutrients. The K/Na selectivity ratio was much greater in the saline treated plants than in the control plants. Osmotic adjustment of roots and leaves was predominantly due to Na⁺ and Cl^? accumulation; the contribution of proline to the osmotic adjustment seemed to be less important in these cotton cultivars.     

GROWTH AND PHYSIOLOGICAL RESPONSE OF HYDROPONICALLY-GROWN SUNFLOWER AS AFFECTED BY SALINITY AND MAGNESIUM LEVELS

The effects of NaCl and magnesium levels (Mg²⁺) on the physiological response of sunflower were investigated. Plants were grown for 54 days in hydroponic culture with NaCl (100 mM) or without NaCl and four concentrations of Mg²⁺: 0, 0.4, 1.0 and 5.0 mM. At the end of the vegetative growing cycle of sunflower, salt stress reduced leaf area development by 51% and dry matter accumulation by 37% as compared to non saline-treated plants; at this stage, considering the percent reduction of partitioned plant dry matter, roots (42%) and leaves (35%) showed to be more salt-sensitive than stem. Growth reduction was related to the drop in net CO₂ assimilation rate and stomatal conductance, which started declining later during the vegetative growth period when leaf ion concentration started increasing. The investigated genotype was unable to exclude ions and significant amounts of Cl^? (about 1700 μmol g^?1 DW) and lesser Na⁺ (700 μmol g^?1 DW) accumulated in the leaves. The decline in net CO₂ assimilation was well correlated to the increase in leaf Cl^? concentration (r² = 0.71) and not to leaf Na⁺ concentration (r² = 0.33). The results suggest that, though sunflower develops an endogenous protection system by which it redistributes this ions in the whole plant, with more ions accumulating in roots and older leaves, growth reduction may be attributed to specific toxic effects of Cl^? on photosynthetic functionality. In both saline and non saline conditions, little or no significant differences in growth parameters of plants exposed to a range from 0.4 to 5 mM of Mg²⁺ were observed. Whereas, its deficiency caused a drastic reduction of dry matter accumulation up to 90%, due to progressive decline in CO₂ assimilation rate and chlorophyll content, with imbalances in Ca²⁺, Mg²⁺ and K⁺.     

Effect of grafting on the growth and ion concentrations of cucumber seedlings under NaCl stress

Abstract

To assess whether grafting raised the salt tolerance of cucumber seedlings by limiting transport of Na⁺ to the leaf and to test whether the salt tolerance of grafted plants was affected by the shoot genotype, two cucumber cultivars (“Jinchun No. 2”, a relatively salt-sensitive cultivar, and “Zaoduojia”, a relative salt-tolerant cultivar) were grafted onto rootstock pumpkin (Cucurbita moschata Duch. cv. “Chaojiquanwang”, a salt-tolerant cultivar). Ungrafted plants were used as controls. The effects of grafting on plant growth and ion concentrations were investigated under NaCl stress. Reductions in the shoot and root dry weights, leaf area and stem diameter of grafted plants were lower and concentrations of K⁺ and Cl^? in the leaves were higher than those of ungrafted plants under the same NaCl stress. The Na⁺ concentration and Na⁺/K⁺ ratio in scion leaves and in the stems of grafted plants were lower, whereas those in rootstock stems and roots were higher than in ungrafted plants under the same NaCl stress. Shoot and root dry weight, leaf area and stem diameter were negatively correlated with leaf Na⁺ concentrations and Na⁺/K⁺ ratio, but were positively correlated with leaf K⁺ concentrations. The Na⁺ concentrations and Na⁺/K⁺ ratio were lower, whereas the K⁺ concentrations in the leaves of grafted “Zaoduojia” plants were higher than those in grafted “Jinchun No. 2” plants under the same NaCl stress. The reductions in leaf area and stem diameter of grafted “Jinchun No. 2” plants were more severe than those of grafted “Zaoduojia” plants. These results indicate that: (1) the higher salt tolerance of grafted cucumber seedlings is associated with lower Na⁺ concentrations and Na⁺/K⁺ ratio and higher K⁺ concentrations in the leaves, (2) grafting improved the salt tolerance of cucumber seedlings by limiting the transport of Na⁺ to the leaves, (3) the salt tolerance of grafted cucumber seedlings is related to the shoot genotype.     

Growth,ion accumulation,and lipid composition of two olive genotypes under salinity 1

Olive (Olea europaea L cv. Leccino and cv. Frantoio) plants grown in aeroponic cultivation system were supplied with Hoagland solutions containing 0 and 150 mM NaCl for 4 weeks. Sodium (Na⁺), chloride (Cl^‐), and potassium (K⁺) concentration was measued on 15‐day‐old leaves and K⁺/Na⁺ selectivity ratio was calculated. Plant water relations were estimated on the same leaves by measuring leaf bulk water and osmotic potentials, and by calculating leaf turgor pressure. Root and leaf tissues were also analysed for lipid composition, estimating free sterol (FS), glycolipid (GL) and phospholipd (PL) content. The salt‐sensitive Leccino accumulated more Na⁺ and Cl^‐ in the leaves and showed a lower K⁺/Na⁺ selectivity ratio than the salt‐tolerant Frantoio. The FS/PL ratio and the content of GL (namely mono‐galactosyldiglyceride, MGDG) in the roots were related to the salt accumulation in the shoot. Salinity‐induced changes on root lipids were more important in Frantoio than in Leccino, indicating the specific role of the roots in salt exclusion mechanisms. Conversely the effect of salinity on leaf lipid composition was more important in the leaves of the salt‐sensitive Leccino.     

Lavandula multifida response to salinity: Growth,nutrient uptake,and physiological changes

Fern leaf lavender (Lavandula multifida L.) is a perennial shrub native to Almería with known medicinal properties, which grows in saline soils that are increasingly present in the Mediterranean region. However, the effects of salinity on the mineral nutrition and physiology of L. multifida are unknown. In the present study, we evaluated the salt resistance of this species and compared it with other members of the Lamiaceae . Plants of L. multifida were grown in pots in a mixture of sphagnum peat‐moss and Perlite, and treated with five different NaCl concentrations [10 (control), 30, 60, 100, and 200 mM NaCl] over a period of 60 d. The effects of different levels of salinity on mineral nutrient and osmolyte concentrations and on biomass were evaluated. Our results show that L. multifida plants were able to grow with 60 mM NaCl without significant biomass reduction. Na⁺ and Cl⁻ were the main contributors to the osmotic potential in both roots and leaves, whereas total soluble sugars (TSS) and proline made only a small contribution. The concentrations of TSS and proline showed different trends in the different organs: in roots, both showed the highest concentrations at 60 mM NaCl, whereas in leaves TSS increased and proline decreased with increasing salt stress. To survive salinity, L. multifida plants increased salt excretion (Na⁺ and Cl⁻) by leaves at 100 and 200 mM NaCl and leaf succulence at 60, 100, and 200 mM NaCl. Excessive accumulation of Na⁺ and Cl⁻ was avoided by shedding leaves. Our results indicate that L. multifida is better adapted to salinity compared to other members of the Lamiaceae ¸ a consideration that is particularly relevant for their growth in arid saline areas.     

Na+ and Cl−: Leaf extrusion,retranslocation and root efflux in diplachne fusca (kallar grass) grown in NaCl

Abstract

Groups of “Kallar”; grass plants were subjected to various treatments of 100 mM NaCl simultaneously labelled with ²²Na⁺ and ³⁶Cl^?. On the basis of the specific activity, the distribution of Na and Cl^? in the tissue was followed during and after treatment, i.e. after transfer of some groups to an identical but inactive solution. Sequential collections of leaf washes showed that both Na and Cl^? were extruded at a somewhat constant rate. Leaf sheaths accumulated more Na⁺ and Cl^? than the leaf blades and the amounts of Na⁺ and Cl^? in the leaf sheaths as a percentage of their total plant content (i.e. 28% and 31%) approximated the amounts of Na and Cl^? extruded by the leaves (i.e. 23%). Moreover, almost equivalent amounts of Na⁺ (21%) and Cl^? (29%) were removed by root efflux which continued even several days after transfer of the plants to the inactive, saline solution. Part of the Na⁺ and Cl^? was retranslocated from the tops to the roots and was attributed to phloem export.

Tolerance of Kallar grass to NaCl was thus related to preventing the tissue from accumulating high concentration by extrusion of both Na⁺ and Cl^? by the leaves and their efflux by the roots in addition to an equivalent retention in the leaf sheaths.     

Accumulation,distribution, and physiological contribution of oxalic acid and other solutes in an alkali‐resistant forage plant,Kochia sieversiana,during adaptation to saline and alkaline conditions

Kochia sieversiana (Pall.) C. A. Mey is a forage plant in the family Chenopodiaceae, which can grow in extremely alkalinized grasslands at pH levels of 10 or higher. Kochia sieversiana often contains a large amount of oxalic acid. In the present study, seedlings of K. sieversiana were exposed to the following conditions: nonstress, salt stress (molar ratio of NaCl : Na₂SO₄ = 1:1, salinity: 200 mM), and alkali stress (molar ratio of NaHCO₃ : Na₂CO₃ = 1:1, salinity: 200 mM). By determining and analyzing various physiological factors such as the concentrations and distribution of different organic acids (including oxalic acid) in various parts of K. sieversiana, the concentrations of inorganic ions (K⁺, Na⁺, Cl^–, SO$ _4^{2-} $ , etc.), the organic solutes (proline, betaine, and soluble sugar) in shoots, and the accumulation and distribution of oxalic acid in K. sieversiana, the physiological contribution of oxalic acid to K. sieversiana adaptability to saline and alkaline conditions was investigated. Results show that oxalic acid mainly accumulated in shoots, and that its concentration was highest in mature functional leaves where photosynthesis productivity was based and lowest in old stems and roots, regardless of plant treatment (nonstress, salt, or alkali conditions). Under nonstress, salt, and alkali conditions, the concentrations of oxalic acid in mature leaves were 8%, 10%, and 12% of their dry weights, respectively, and were 1%, 0.7%, and 0.6% of dry weights, respectively, in roots. There were varying effects of salt and alkali conditions on oxalic acid concentrations in different parts of K. sieversiana. Oxalic acid concentration increased in leaves, did not change significantly in young stems, and decreased in old stems and roots. The present analysis shows that oxalic acid exists as an organic anion in K. sieversiana. Consequently, oxalic acid not only plays a crucial role in osmoregulation and pH adjustment, but it also is the dominant contributor of negative charge, playing a key role in maintaining ionic balance in vivo. Oxalic acid in K. sieversiana shoots is a key substance on which the adaptation to saline and alkaline conditions is based.     

Physiological Response to Sodium Chloride of Wild Swiss Chard

ABSTRACT

The present work was aimed at determining the limits of tolerance to sodium chloride (NaCl) of a halophyte, Beta macrocarpa Guss (wild Swiss chard). Five week-old plants were cultivated with a nutritive solution to which was added 0, 100, 200, and 300 mM NaCl. Plants were harvested after four weeks of treatment. The growth (fresh and dry weight, leaf surface area, and leaf number), water contents, and the mineral composition (meq · g^?1 DW) of roots and leaves (reduced nitrogen (N), K⁺, Ca^{2 +}, Na⁺, Cl^?) were determined on individual plants. Results show that Beta macrocarpa can tolerate up to 200 mM NaCl. A significant decrease in biomass production (to 50% of control) was observed only for 300 mM NaCl. In the latter treatment, leaf mean surface area was 25% of control. The shoot-to-root ratio was not changed. Leaf hydration was not modified by salt treatment. This ability of the plant to maintain the hydric equilibrium of its leaves seemed associated with an efficient intracellular compartmentalization of Na⁺ and Cl^? ions. Salt treatment had little effect on N content (80% of control), but decreased significantly K⁺ and Ca^{2 +} contents. These three essential elements could be limiting for growth of leaves and roots of plants challenged by NaCl.     

Salinity Stress Promote Drought Tolerance of Chenopodium Quinoa Willd

A greenhouse experiment was conducted to investigate the impact of water and salt stress in Quinoa plants (Chenopodium quinoa Willd.). Irrigation treatments using saline solutions of 0 (control), 50(T₁), 200(T₂), 400(T₃), 600(T₄), and 800(T₅) mM sodium chloride (NaCl) were adopted. The results indicated that quinoa plants can tolerate water stress (50%FC) when irrigated with moderately saline water (T₁ and T₂, respectively). Salinity stress increases quinoa drought tolerance in terms of biomass production. Neither osmotic stress nor ions deficiency/toxicity seems to be determinant under T₁ and 100%FC. Salinity induced a significant increase of sodium (Na⁺) and chloride (Cl^?), while reduced magnesium (Mg²⁺) and calcium (Ca²⁺) in stems, leaves, seed’s coating, and seeds. The potassium (K⁺)/Na⁺ ratio never fell below 1 with T₁; yet, fell to 0.78 and 0.89 with T₂ for 100% and 50%FC, respectively. The seed coat limited the passage of possibly toxic concentrations of Na⁺ and Cl^? to seed interior, as high Na⁺ and Cl^? was found in the seed coat.     

Ionic interactions and salinity affect monoterpene and phenolic diterpene composition in rosemary (Rosmarinus officinalis)

In this study, we evaluated how increased cation supply can alleviate the toxic effects of NaCl on plants and how it affects essential oils (EOs) and phenolic diterpene composition in leaves of rosemary (Rosmarinus officinalis L.) plants grown in pots. Two concentrations of the chloride salts KCl, CaCl₂, MgCl₂, and FeCl₃ were used together with 100 mM NaCl to study the effects of these nutrients on plant mineral nutrition and leaf monoterpene, phenolic diterpene, and EO composition. The addition of 100 mM NaCl, which decreased K⁺, Ca²⁺, and Mg²⁺ concentrations with increasing Na⁺ in leaves, significantly altered secondary metabolite accumulation. Addition of MgCl₂ and FeCl₃ altered leaf EO composition in 100 mM NaCl–treated rosemary plants while KCl and CaCl₂ did not. Furthermore, addition of CaCl₂ promoted the accumulation of the major phenolic diterpene, carnosic acid, in the leaves. The carnosol concentration was reduced by the addition of KCl to salt‐stressed plants. It is concluded that different salt applications in combination with NaCl treatment may have a pronounced effect on phenolic diterpene and EO composition in rosemary leaves thus indicating that ionic interactions may be carefully considered in the cultivation of these species to achieve the desired concentrations of these secondary metabolites.     

Studies on growth and distribution of Na+, K+ and Cl− in soybean varieties differing in salt tolerance

Soybean plants, varieties “Lee”, “Jackson” and “Bragg” were grown in solution culture at various salinity levels. A NaCl concentration of 10 mM was already inhibitory to growth of “Jackson”; growth of “Lee”, however, was only reduced at a salt concentration of 50 mM or higher. The moderately salt tolerant variety “Lee” efficiently excluded Cl^? from the leaves up to about 50 mM NaCl in the medium, but showed high Cl^? contents in the root; exclusion of Na⁺ from the leaves was also apparent in this variety. On the other hand, the salt sensitive variety “Jackson” did not have the capacity for exclusion of Cl^? and Na⁺. The physiological behaviour of the variety “Bragg” resembled that of “Jackson”. It is suggested that the exclusion of Cl^? and Na⁺ from the leaves in the soybean variety “Lee” is regulated by the root.     

Protective role of proline against salt stress is partially related to the improvement of water status and peroxidase enzyme activity in cucumber

Abstract

A salt-sensitive cucumber cultivar “Jinchun No. 2” (Cucumis sativus L.) was used to investigate the role of proline in alleviating salt stress in cucumber. Proline was applied twice (day 0 and day 4 after salt treatment) as a foliar spray, with a volume of 25?mL per plant at each time. Plant dry weight, leaf relative water content, proline, malondialdehyde (MDA), Na⁺, K⁺ and Cl^? contents, as well as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities in the plants were determined at day 8 after salt treatment. The results showed that 100?mmol?L^–1 NaCl stress significantly decreased plant dry weight, leaf relative water and K⁺ contents, and increased leaf MDA, Na⁺ and Cl^? contents and SOD, POD, CAT and APX activities. However, leaf proline accumulation was not affected by salinity. The exogenous application of proline significantly alleviated the growth inhibition of plants induced by NaCl, and was accompanied by higher leaf relative water content and POD activity, higher proline and Cl^? contents, and lower MDA content and SOD activity. However, there was no significant difference in Na⁺ and K⁺ contents or in CAT and APX activities between proline-treated and untreated plants under salt stress. Taken together, these results suggested that the foliar application of proline was an effective way to improve the salt tolerance of cucumber. The enhanced salt tolerance could be partially attributed to the improved water status and peroxidase enzyme activity in the leaf.     

Evaluation of Salinity Effects on Ionic Balance and Compatible Solute Contents in Nine Grape (Vitis L.) Genotypes

The salinity tolerance of nine grape genotypes was studied. Salinity was applied as nutrient solutions containing 0, 25, 50, and 100 mM sodium chloride (NaCl) for two weeks. Growth was significantly reduced by salinity, whereas chloride (Cl^?) and sodium (Na⁺) contents increased. Sodium ion accumulation exceeded that of Cl^? in all treatments. Shirazi and H₆ had higher and lower Cl^? concentrations in their lamina than others. There were significant positive correlations (P < 0.01) between Cl^? and Na⁺ and negative correlation between Na⁺ and potassium (K⁺) in roots and laminas of all genotypes. Soluble sugars, proline, and glycine betaine contents increased in laminas of all of the genotypes with moderate salinity. There were positive correlations (P < 0.01) between lamina and root Na⁺ and Cl^? contents and compatible solutes in all genotypes. Overall results revealed that unlike Shirazi with higher Na⁺ and Cl^? accumulation in shoot, H₆ showed a higher capacity to restrict Na⁺ and Cl^? transport to shoot.     

Effects of salt stress on distribution of Na+ and some other cations in two soybean varieties differing in salt tolerance

In the course of investigations on the impact of salinity on mineral ion transport in differentially salt susceptible soybeans (“Lee” and “Jackson”) short-term experiments were conducted to elucidate the distribution pattern of Na⁺ and some other cations. The results showed that low salinity (7.5 mM NaCl) did not induce varietal differences in Na⁺ content during a 30 hrs uptake period. At 66.5 mM NaCl, however, the Na⁺ contents increased more in the leaves of the salt sensitive variety “Jackson” than in “Lee”. Both soybean varieties retained Na⁺ in the proximal root and stem. Furthermore, they extruded considerable amounts of Na⁺ from the roots to the medium. Increasing the level of salinity in the solution substantially reduced the Ca²⁺ uptake of both soybean varieties. In an experiment with the salt sensitive variety under constant salinity but increasing Ca²⁺ concentration in the medium, the plants showed a reduction in Na⁺ uptake and translocation to stem and leaves and an enhanced Ca²⁺ uptake and translocation to the shoots. It is suggested that the injury observed in “Jackson” after salt treatment is not only related to the insufficient control of Cl^? transport. At higher salinity levels the increasing accumulation of Na⁺ in the leaves and the varietally independant depression of Ca²⁺ uptake and translocation may enhance the development of leaf necrosis.     

Effect of salinity on metalloenzymes of oxygen metabolism in two leguminous plants

Abstract

Superoxide dismutase (SOD) pattern, catalase, Cyt c oxidase and fumarase activity were studied in leaves of Phaseolus vulgaris and Vigna unguiculata plants growth in two sodium chloride (NaCl) concentrations (35 mM and 100 mM). In bean plants growth with NaCl, leaf chloride (Cl^?) contents were higher than in control plants, and the same was found for sodium (Na⁺) and potassium (K⁺) contents, although to a lesser degree. In cowpea leaves, Na⁺ and Cl^? had a similar increase due to salt‐growth conditions. Under salinity, all changes in the antioxidant (SOD and catalase) enzymes levels were smaller in bean than in cowpea plants. In Phaseolus at 15 days growth, Cu, Zn‐SOD I showed an increase by the effect of salt treatment, but this induction did not occur at 30 days growth, and both Mn‐SOD and Cu, Zn‐SOD II did not show variations due to salt‐stress. In Vigna, Mn‐SOD was decreased by salinity but this was compensated by an increase in Cu, Zn‐SOD I activity in plants at 30 days growth, whereas in young leaves under saline conditions, both isozymes were also decreased. Likewise, there was a rise in cytochrome c oxidase and fumarase activity in leaves of NaCl‐treated plants compared to the control. The activity changes observed are discused in term of their possible relevance to plant sensitivity to saline conditions.     

Individual and additive effects of Na+ and Cl− ions on rice under salinity stress

This study was attempted to assess the extent of toxicity contributed by Na⁺ and/or Cl^? ions individually, besides their possible additive effects under NaCl using physiological and biochemical parameters. Despite the fact that most annual plants accumulate both Na⁺ and Cl^? under saline conditions and each ion deserves equal considerations, most research has been focused on Na⁺ toxicity. Consequently, Cl^? toxicity mechanisms including its accumulation/exclusion in plants are poorly understood. To address these issues, effects of equimolar (100 mM) concentrations of Na⁺, Cl^? and NaCl (EC ≈ 10 dS m^?1) were studied on 15-day-old seedlings of two rice cultivars, Panvel-3 (tolerant) and Sahyadri-3 (sensitive), using in vitro cultures. All three treatments induced substantial reductions in germination rate and plant growth with greater impacts under NaCl than Na⁺ and Cl^? separately. Apparently, salt tolerance of Panvel-3 was due to its ability to exclude Na⁺ and Cl^? from its shoots and maintaining low (<1.0) Na⁺/K⁺ ratios. Panvel-3 exhibited better vigour and membrane stability indices coupled with lower reactive oxygen species and lipid peroxidation levels, besides stimulated synthesis of proline, glycine betaine and ascorbic acid. Overall, the magnitude of toxicity was observed in NaCl > Na⁺ > Cl^? manner. Though Cl^? was relatively less toxic than its countercation, its effect cannot be totally diminished.     

Salt stress effects on enzymes activities involved in carbon metabolism and nitrogen availability of two Tunisian durum wheat varieties

Two varieties of durum wheat (Om Rabiaa and Karim), were analyzed and evaluated in the presence of increasing doses of NaCl (0, 100, 200 and 300?mM) in which we added different concentrations of nitrate (0.1, 3, 10?mM). The data obtained showed that presence of NaCl in the culture medium induces the increase of the salt accumulation levels (Na⁺, Cl^?) and reduces the levels of K⁺ and NO₃^? in the cultivar Om Rabiaa. In Karim variety, ions that have been heavily accumulated following exposure to NaCl are Na⁺ and K⁺ while low levels of NO₃^? and Cl^? have been detected. Those findings highlight the difference in the salinity tolerance of durum wheat cultivars also depending on nitrogen (N) availability, Karim cultivar being less sensitive to NaCl treatment than Om Rabiaa. These data also suggested a relationship between salt tolerance capacity and enhancement of nitrogen and carbon metabolisms enzyme activity.     

Growth,Mineral Composition,and Biochemical Changes of Broad Bean as Affected by Sodium Chloride and Zinc Levels and Sources

Plants grown in salt‐affected soils may suffer from limited available water, ion toxicity, and essential plant nutrient deficiency, leading to reduced growth. The present experiment was initiated to evaluate how salinity and soil zinc (Zn) fertilization would affects growth and chemical and biochemical composition of broad bean grown in a calcareous soil low in available Zn. The broad bean was subjected to five sodium chloride (NaCl) levels (0, 10, 20, 30, and 40 m mol kg^?1 soil) and three Zn rates [0, 5, and 10 mg kg^?1 as Zn sulfate (ZnSO₄) or Zn ethylenediaminetetraaceticacid (EDTA)] under greenhouse conditions. The experiment was arranged in a factorial manner in a completely randomized design with three replications. Sodium chloride significantly decreased shoot dry weight, leaf area, and chlorophyll concentration, whereas Zn treatment strongly increased these plant growth parameters. The suppressing effect of soil salinity on the shoot dry weight and leaf area were alleviated by soil Zn fertilization, but the stimulating effect became less pronounced at higher NaCl levels. Moreover, rice seedlings treated with ZnSO₄ produced more shoot dry weight and had greater leaf area and chlorophyll concentration than those treated with Zn EDTA. In the present study, plant chloride and sodium accumulations were significantly increased and those of potassium (K), calcium (Ca), and magnesium (Mg) strongly decreased as NaCl concentrations in the soil were increased. Moreover, changes in rice shoot Cl^?, Na⁺, and K⁺ concentrations were primarily affected by the changes in NaCl rate and to a lesser degree were related to Zn levels. The concentrations of Cl^? and Na⁺ associated with 50% shoot growth suppression were greater with Zn‐treated plants than untreated ones, suggesting that Zn fertilization might increase the plant tolerance to high Cl^? and Na⁺ accumulations in rice shoot. Zinc application markedly increased Zn concentration of broad bean shoots, whereas plants grown on NaCl‐treated soil contained significantly less Zn than those grown on NaCl‐untreated soil. Our study showed a consistent increase in praline content and a significant decrease in reducing sugar concentration with increasing salinity and Zn rates. However, Zn‐treated broad bean contained less proline and reducing sugars than Zn‐untreated plants, and the depressing impact of applied Zn as Zn EDTA on reducing sugar concentration was greater than that of ZnSO₄. In conclusion, it appears that when broad bean is to be grown in salt‐affected soils, it is highly advisable to supply plants with adequate available Zn.