Changes in growth,photosynthetic capacity and ionic relations in spring wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) due to pre-sowing seed treatment with polyamines

The influence of pre-sowing seed treatment with polyamines (2.5 mM putrescine, 5.0 mM spermidine and 2.5 mM spermine) on growth, photosynthetic capacity, and ion accumulation in two spring wheat (Triticum aestivum L.) cultivars MH-97 (intolerant) and Inqlab-91 (tolerant) was examined. The primed seeds of each treatment and non-primed seeds were sown in a field containing 15 dS m⁻¹ NaCl. Although all three polyamines were effective in improving shoot growth and grain yield in both cultivars under saline conditions, the effect of spermine was very pronounced particularly in improving grain yield. Different priming agents did not affect the net CO₂ assimilation rate and transpiration rate of either cultivar. However, pre-treatment with spermidine increased stomatal conductance (g_s) in the tolerant cultivar, whereas with spermine stomatal conductance decreased in the intolerant cultivar under salt stress. Priming agents had different effects on the accumulation of different ions in wheat plant tissues. When spermidine and distilled water were used as priming agents, they were effective in reducing shoot [Na⁺] in the tolerant and intolerant cultivars, respectively under saline conditions. Although all priming agents caused an increase in shoot [K⁺], distilled water was more effective in improving shoot [K⁺] in both cultivars under salt stress. Pre-treatment with spermidine was very effective in reducing shoot [Cl⁻] under saline conditions particularly in the tolerant cultivar. However, the pattern of accumulation of different ions in roots due to different seed priming treatments was not consistent in either cultivar except that root Na⁺ decreased due to priming with spermine and spermidine in the intolerant and tolerant cultivars under saline conditions. In conclusion, although all three priming agents, spermine, spermidine and putrescine, were effective in alleviating the adverse effect of salt stress on wheat plants, their effects on altering the concentration of different ions and growth were different in the two cultivars differing in salt tolerance.     

Salicylic acid-mediated changes in photosynthesis,nutrients content and antioxidant metabolism in two mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> L.) cultivars differing in salt tolerance

Mustard (Brassica juncea L.) cultivars Alankar (salt-tolerant) and PBM16 (salt-sensitive) plants were grown with 50 mM NaCl and were sprayed with 0.1, 0.5, and 1.0 mM salicylic acid (SA) to study the physiological processes determining salt tolerance and to observe the influence of SA application on the alleviation of NaCl-induced adverse effects. The content of leaf Na⁺, Cl⁻, H₂O₂, TBARS, and electrolyte leakage and the activity of SOD were higher in PBM16 than Alankar. In contrast, nutrients content, activity of APX and GR, glutathione content, photosynthetic and growth characteristics were higher in Alankar. Treatment of 50 mM NaCl resulted in increase of Na⁺ and Cl⁻, oxidative stress, activity of antioxidant enzymes and glutathione content, while nutrients content, photosynthetic, and growth characteristics decreased in both the cultivars. Application of 0.5 mM SA alleviated the negative effects of 50 mM NaCl maximally, but 1.0 mM SA proved inhibitory. The effect of SA was more conspicuous in Alankar than PBM16. It is concluded that the higher tolerance of Alankar was due to its lower leaf Na⁺ and Cl⁻ content, higher nutrients content, and efficient antioxidant metabolism. The application of 0.5 mM SA substantially alleviated salt-induced adverse effects in Alankar.     

Response of Strawberry Plant cv. ‘Camarosa’ to Salicylic Acid and Methyl Jasmonate Application Under Salt Stress Condition

The possible role of salicylic acid (SA) and methyl jasmonate (MJ) treatments on the physiology responses and growth of strawberry (Fragaria?×?ananassa) cv. ‘Camarosa’ subjected to the different levels of salinity stress were investigated. Root and shoot growth as well as their Na⁺/K⁺ ratio, photosynthetic-related factors, and activity of some important antioxidant enzymes were determined in the salt-treated plants. Results indicated that salt stress reduced plant performance especially at higher concentrations. By increasing the levels of salinity stress, fresh and dry weight of shoot and roots, net photosynthetic rate (Pn), and stomatal conductance (Gs) significantly decreased, whereas intercellular CO₂ (Ci) increased. Application of exogenous SA and MJ significantly improved the plant physiological characters as well as fresh and dry weight of shoots and roots. Moreover, the ratio of Na⁺/K⁺ was elevated in the leaves and roots concomitantly with salinity levels, whereas SA and MJ treatments significantly reduced this ratio. Results of enzymatic assays showed that activity of ascorbate peroxidase, peroxidase, and superoxide dismutase enzymes increased in the salt-stressed plants. In addition, SA and MJ treatments reduced the destructive effects of salinity in strawberry plant. In general, among the tested concentrations, 0.5 mM SA and 0.25 mM MJ best increased the activity of antioxidant enzymes and hence alleviated the detrimental effects of salinity stress.     

Salicylic Acid Confers Salt Tolerance in Giant Juncao Through Modulation of Redox Homeostasis,Ionic Flux,and Bioactive Compounds: An Ionomics and Metabolomic Perspective of Induced Tolerance Responses

We investigated the stimulatory and/or inhibitory role of exogenous SA in alleviating the salt stress (250, 500 mM NaCl) in Pennisetum giganteum (Giant Juncao) through coordinated induction of redox homeostasis, ionic flux, and bioactive compounds. Salt stress radically impaired root and shoot (growth, fresh, and dry biomass as well as tolerance indices), leaf relative water content, and leaf chlorophyll a/b ratio of Juncao due to higher Na⁺ and Cl^? accumulation followed by H₂O₂ generation, lipid peroxidation (MDA contents), and electrolyte leakage. However, the innate defense response of Juncao counteracted salt-induced damages by osmolytes accumulation combined with orchestrating antioxidants and ionic homeostasis mechanisms. Furthermore, the application of SA had an incremental impact on the development and productivity of high-salinity-exposed Juncao plants by increasing root length, plant biomass, tolerance indices, chlorophyll a/b ratio, and protein contents. Furthermore, SA treatment considerably decreased Na⁺ and Cl^? toxicity by orchestrating antioxidant enzymes, ion transport, and secondary metabolism. Notably, the application of SA substantially mitigated the adverse effects of high salinity concentration (500 mM NaCl), owing to the simultaneous upregulation in enzymatic and non-enzymatic antioxidants, nutrient ion flux, alongside chlorogenic acid production. Thus, we concluded that SA enhanced the tolerance capability of Juncao plants in a NaCl concentration-dependent manner. The findings of this study will enable environmentalists and pharmacologists to gain dual farm-level benefits, including animal therapeutics and restoration of salinized soils for arable purposes.

     

Simultaneous Application of Rhizobium Strain and Melatonin Improves the Photosynthetic Capacity and Induces Antioxidant Defense System in Common Bean (Phaseolus vulgaris L.) Under Salinity Stress

Melatonin (N-acetyl-5-methoxytryptamine) as a natural biostimulating substance provides a number of benefits in stimulating plant growth in stress situations due to its natural antioxidant capacity. Rhizobia also play crucial roles in supporting plant growth under environmental stress conditions. The overall goal of this research is to study the possible positive effects of melatonin and rhizobacterium in enhancing the growth and salinity tolerance of common bean. To accomplish this objective, we conducted in vitro experiment to select the optimal melatonin concentration and treatment time of seed priming for the best germination. Also, a greenhouse experiment was performed to investigate the effect of melatonin pre-treatment applied before rhizobial inoculation to improve the fitness of common bean under salinity stress. The experiment was conducted using a completely randomized factorial design with six replications and three treatments: priming treatments (melatonin priming (PM100), hydro priming (PH) and dry (PD)), salinity (0, 4, 8, 10 and 16 dS m^?1) and Rhizobium strain (inoculated (RS?+) and uninoculated (RS?)). Our results showed that melatonin priming promoted bacterial colony size in Petri-dishes. The interactive effects of melatonin and RS?+?was found to alleviate reactive oxygen species (ROS) burst, and hence protect common bean chlorophylls a, b and carotenoid and photosynthetic activity and decrease malondialdehyde content through activation of antioxidant enzymes (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase), facilitation of soluble protein synthesis, maintenance of Na⁺ and K⁺ homeostasis, and finally increase shoot dry weight (33.2, 39.5 and 31.5%) and seed yield (78.6, 91 and 54.2%) compared to the combination of PD and RS- treatments under 0, 4 and 8 dS m^?1 salinity levels, respectively. Thus, our findings suggest that seed priming with melatonin, especially 100 µM melatonin is an effective strategy that can be used to enhance salt tolerance in common bean.

     

外源SA和NO对NaCl胁迫下番茄幼苗生长、光合及离子分布的影响

以番茄(Lycopersicon esculentum Mill.)品种‘秦丰保冠’为试材,采用营养液培养法,研究单独和复配施用外源水杨酸(SA)、一氧化氮(NO)供体硝普钠(SNP)对100mmol/L NaCl胁迫下番茄幼苗生长、光合及离子分布的影响。结果表明:(1)单独和复配外施SA、SNP均能有效抑制NaCl胁迫下番茄幼苗叶片光合色素(Chla、Chlb、Chla+b和Car)含量、Chla/b值、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、瞬时水分利用效率(WUEt)、表观光能利用效率(LUEapp)和表观CO2利用效率(CUEapp)的下降及Car/Chla+b值和胞间CO2浓度(Ci)的升高,并以SA和SNP复配处理效果最明显。(2)NaCl胁迫下,外源SA、SNP单独和复配处理的番茄幼苗各器官(叶、茎和根)中Cl-、Na+含量和Na+/K+、Na+/Ca2+、Na+/Mg2+值显著降低,而K+、Ca2+和Mg2+的含量却不同程度提高,其中以SA和SNP复配处理效果最好。(3)单独和复配外施SA、SNP均能有效减轻NaCl胁迫对番茄幼苗生长的抑制作用,并促进各器官生物量的积累和壮苗的形成,且以SA和SNP复配处理效果更佳。研究表明,复配外施SA和SNP在诱导番茄幼苗提高抗(耐)盐能力方面具有协同增效作用。     

Effects of buffer capacity on growth,photosynthesis, and solute accumulation of a glycophyte (wheat) and a halophyte (<Emphasis Type="Italic">Chloris virgata</Emphasis>)

Two species with different resistances to alkaline pH, the glycophylic Triticum aestivum (wheat) and the halophilic Chloris virgata, were chosen as test organisms. The salt-alkaline (SA) mixed stress conditions with different buffer capacities (BC) but with the same salt molarities and pH were established by mixing neutral (NaCl, Na₂SO₄), and alkaline salts (NaHCO₃ and Na₂CO₃) in various proportions. Growth, photosynthetic characteristics, and solute accumulation of the seedlings were monitored to test the validity of BC as a decisive index of alkali-stress (AS) intensity in SA mixed stress. At the same salinities and pHs, the relative growth rate, the content of photosynthetic pigments, and net photosynthetic rates of wheat and C. virgata decreased, while Na⁺ content and Na⁺/K⁺ ratios in shoots increased with increasing BC. Hence BC was a true measure of AS intensity at mixed SA stress and the alkali-resistance mechanism of plants was easy to interpret. BC of soil solution is an important parameter for estimating the alkalization degree of salt-alkalized soil.     

Arbuscular mycorrhizal fungi native from a Mediterranean saline area enhance maize tolerance to salinity through improved ion homeostasis

Soil salinity restricts plant growth and productivity. Na⁺ represents the major ion causing toxicity because it competes with K⁺ for binding sites at the plasma membrane. Inoculation with arbuscular mycorrhizal fungi (AMF) can alleviate salt stress in the host plant through several mechanisms. These may include ion selection during the fungal uptake of nutrients from the soil or during transfer to the host plant. AM benefits could be enhanced when native AMF isolates are used. Thus, we investigated whether native AMF isolated from an area with problems of salinity and desertification can help maize plants to overcome the negative effects of salinity stress better than non‐AM plants or plants inoculated with non‐native AMF. Results showed that plants inoculated with two out the three native AMF had the highest shoot dry biomass at all salinity levels. Plants inoculated with the three native AMF showed significant increase of K⁺ and reduced Na⁺ accumulation as compared to non‐mycorrhizal plants, concomitantly with higher K⁺/Na⁺ ratios in their tissues. For the first time, these effects have been correlated with regulation of ZmAKT2, ZmSOS1 and ZmSKOR genes expression in the roots of maize, contributing to K⁺ and Na⁺ homeostasis in plants colonized by native AMF.     

Effects of foliar applications of nitric oxide and salicylic acid on salt-induced changes in photosynthesis and antioxidative metabolism of cotton seedlings

Nitric oxide (NO) is a plant signaling compound known to mitigate key physiological processes and salicylic acid (SA) is considered to be a signaling molecule that plays a key role in growth, development, and defense responses in plants under stress conditions. This work investigated the effects of sodium nitroprusside (SNP, a donor of NO) and SA on salt-tolerance of cotton (Gossypium hirsutum L.) seedlings by examining growth, photosynthetic performance, total osmoregulation substance content, antioxidative enzymes and H⁺-ATPase enzyme subjected to 100 mM NaCl. Addition of 100 mM NaCl inhibited the growth and photosynthetic parameters of cotton seedlings, and dramatically increased the electrolyte leakage, the plant contents of proline, lipid peroxidation (malondialdehyde), hydrogen peroxide (H₂O₂) and Na. Furthermore, antioxidant enzyme activities were restrained. Foliar applications of 0.1 mM SNP or/and 0.1 mM SA led to increase in the growth rate and photosynthesis, including photosystem II, net photosynthetic rate and transpiration rate, improvement of reactive oxygen species-scavenging enzymes activities and reduction of H₂O₂ accumulation in cotton seedlings induced by NaCl. In addition, membrane transport and function were facilitated by decreasing leaf electrolyte leakage, improving ion absorption and activating the osmotic-regulated substances metabolic. Further investigation also showed that SNP and SA alleviated the inhibition of H⁺-ATPase in plasma membrane induced by NaCl. The present study showed that foliar application of SNP and SA alone mitigated the adverse effect of salinity, while the combined application proved to be even more effective in alleviating the adverse effects of NaCl stress.     

Physiological and Metabolic Effects of 5-Aminolevulinic Acid for Mitigating Salinity Stress in Creeping Bentgrass

The objectives of this study were to determine whether foliar application of a chlorophyll precursor, 5-aminolevulinic acid (ALA), could mitigate salinity stress damages in perennial grass species by regulating photosynthetic activities, ion content, antioxidant metabolism, or metabolite accumulation. A salinity-sensitive perennial grass species, creeping bentgrass (Agrostis stolonifera), was irrigated daily with 200 mM NaCl for 28 d, which were foliar sprayed with water or ALA (0.5 mg L⁻¹) weekly during the experiment in growth chamber. Foliar application of ALA was effective in mitigating physiological damage resulting from salinity stress, as manifested by increased turf quality, shoot growth rate, leaf relative water content, chlorophyll content, net photosynthetic rate, stomatal conductance and transpiration rate. Foliar application of ALA also alleviated membrane damages, as shown by lower membrane electrolyte leakage and lipid peroxidation, which was associated with increases in the activities of antioxidant enzymes. Leaf content of Na⁺ was reduced and the ratio of K⁺/Na⁺ was increased with ALA application under salinity stress. The positive effects of ALA for salinity tolerance were also associated with the accumulation of organic acids (α-ketoglutaric acid, succinic acid, and malic acid), amino acids (alanine, 5-oxoproline, aspartic acid, and γ -aminobutyric acid), and sugars (glucose, fructose, galactose, lyxose, allose, xylose, sucrose, and maltose). ALA-mitigation of physiological damages by salinity could be due to suppression of Na⁺ accumulation and enhanced physiological and metabolic activities related to photosynthesis, respiration, osmotic regulation, and antioxidant defense.     

Extracts from Yeast and Carrot Roots Enhance Maize Performance under Seawater-Induced Salt Stress by Altering Physio-Biochemical Characteristics of Stressed Plants

Damage to plant productivity due to soil salinity is a major agricultural problem, necessitating the development of effective salinity management measures. Here, we sought the potential effects of yeast and carrot extracts, and their associated mechanisms in the alleviation of seawater-induced salt stress in maize. Pretreatment of maize seeds with yeast or carrot extract provided maize plants with enormous abilities in reducing growth inhibition and biomass loss when exposed to seawater. The better growth performance of yeast extract- and carrot extract-primed plants under saline conditions coincided with improved protection of the photosynthetic pigments, chlorophylls and carotenoids. The primed plants also restricted Na⁺ accumulation in both roots and shoots while maintaining a higher K⁺ content and lower Na⁺/K⁺ ratio when compared with that of non-primed plants. Yeast extract and carrot extract also potentiated salt tolerance mechanisms by accelerating the production of osmolytes, as evidenced by accumulating levels of total free amino acids and soluble sugars, especially in the roots of primed plants during salinity. The enhanced levels of ascorbic acid and phenolic compounds, and the heightened activities of reactive oxygen species-detoxifying enzymes superoxide dismutase, catalase, and ascorbate peroxidase with concurrent reduction of lipid peroxidation in the leaves of primed plants clearly indicated a positive impact of yeast extract- and carrot extract-priming on the antioxidant system of maize under salt stress. Our results together suggest decisive roles of yeast extract and carrot extract in the management of salt-induced adverse effects in economically important maize, and perhaps other crops.

     

Influence of Salt Stress on Growth, Ion Accumulation and Seed Oil Content in Sweet Fennel

A greenhouse experiment was conducted to assess the effect of 25, 50, 75, and 100 mM NaCl on growth, ion accumulation, seed yield, and seed oil content in 67-d-old plants of Foeniculum vulgare Mill. Increasing NaCl concentration caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. Na⁺ and Cl^– in both shoots and roots increased, whereas K⁺ and Ca²⁺ decreased consistently with the increase in NaCl concentration. Plants maintained markedly higher Ca²⁺/Na⁺ ratios in the shoots than those in the roots, whereas that of K⁺ /Na⁺ ratios remained almost uniform in both shoots and roots. Proline content in the shoots increased markedly at the highest NaCl concentration. Oil content in the seed decreased progressively with increase in salinity.     

Effect of Salinity on Seed Germination,Growth, and Ion Accumulation of Atriplex patula (Chenopodiaceae)

Seeds and seedlings of the halophyte Atriplex patula were exposed to 0–2% NaCl to determine the effect of salt stress on germination and growth. Seeds germinated and plants survived and grew in solutions of up to 2.0% NaCl. Both seed germination and dry mass production were negatively affected by increased salinity. Dry mass production declined to 1% of controls and seed germination to 17% of controls in the 2% NaCl treatments, indicating that seeds were less inhibited than growing plants. Also, recovery treatments indicated that high salinity did not permanently injure seeds. Percent ash, and Na⁺ and Cl⁻ ions increased in shoots with each salt increment, while the K⁺ ion content decreased sharply. Atriplex patula is a facultative halophyte, and is limited to low and moderately saline sites because both seed germination and growth are severely reduced at salinities > 1% NaCl.     

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.     

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5 mg L^?1), SWE (5% v/v), BAP + SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10 dS m^?1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K⁺) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na⁺) contents were decreased. Seed priming with SWE + BAP was the most effective in this regard. Under salt stress, the tissue Na⁺ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE + BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE + BAP > BAP > SWE > Hydropriming. In conclusion, seed priming with SWE + BAP may be opted to improve the tolerance against salt stress in wheat.     

Salicylic Acid Induced Salinity Tolerance Through Manipulation of Ion Distribution Rather than Ion Accumulation

In this research, the effect of different SA concentrations (0, 0.5, 1.0, 1.5, and 2.0 mM) on biological and grain yield as well as Na⁺, K⁺, Cl^?, Ca²⁺, and Mg²⁺ distribution and accumulation in barley plants was examined under nonsaline (2 dS m^?1) and saline (12 dS m^?1) conditions in a three-year field study (2012–2015 growing seasons). Storage factor (SF) was defined as the concentration of an ion in the root, as a proportion of total uptake of that ion, to quantify ion partitioning between root and shoot. Salt stress decreased SF for K⁺, Ca²⁺, and Mg²⁺ and enhanced it for Na⁺ and Cl^?, which led to reduce grain and biological yield. Nonetheless, foliar-applied SA in varying concentrations could lower some of these adverse effects on ion transport and accumulation. At the 2nd and 3rd years, unfavorable climatic conditions such as less precipitation and higher temperature intensified salt stress and decreased the alleviating impact of SA. Foliar application of SA at higher levels increased SF for Na⁺ and Cl^? ions and decreased that for K⁺ indicating that SA helped barley plants keep more Na⁺ and Cl^? and less K⁺ ions in the root system, which suggested the probable role of SA in altering ion transport within the plant in favor of salt stress tolerance. SF was found to be more correlated with grain yield under both nonsaline and saline conditions. Overall, SF might be considered as a potential criterion for salt tolerance in barley plants.     

Effects of salinity stress on some growth,physiological, biochemical parameters and nutrients in two pistachio (Pistacia vera L.) rootstocks

In the present study, effects of salinity stress were evaluated in the leaves and roots of two pistachio cultivars (Badami-Rize-Zarand (BZ) and Badami-e-Sefid (BS)). In overall, salinity negatively affects growth of both cultivars with more pronounced effects on BS. The physiological reason of the reduction could be attributed to some extent to more depletion of photosynthetic pigment in BS. In both cultivars, salinity increased proline content. Moderate and high salinities increased the soluble sugar contents in BZ. In both cultivars, Na⁺ content increased in plant organs with increasing Na⁺ in the media. Salinity treatment decreased the Fe and Pi contents in BS cultivar, while they remained unchanged in BZ. These results show that BZ cultivar exhibits more tolerance to salinity stress than BS cultivar possibly by better growth performance, accumulating more osmolytes, lesser accumulation of toxic sodium ion and lower Na⁺/K⁺ in the shoots as well as maintaining nutrient contents.     

Exogenously applied paclobutrazol modulates growth in salt-stressed wheat plants

Effect of paclobutrazol (PBZ) treatment on salinity tolerance of wheat (Triticum aestivum) was investigated on a salt-tolerant (Karchia-65) and salt-sensitive (Ghods) cultivars. Salinity significantly reduced the investigated growth parameters such as plant height, length and area of sixth leaf, root length, fresh and dry weight of shoot, roots and sixth leaf, water content (WC) of plant and seeds weight in the both cultivars. The negative effect of salinity in Ghods cultivar was more than Karchia cultivar. However, PBZ treatment reduced the growth in both cultivars, the differences in plant growth among various levels of NaCl decreased in PBZ-treated plants. Salt stress resulted in high accumulation of Na⁺ in the sixth leaf and roots in both cultivars, particularly in Ghods cultivar. Against Karchia cultivar, salt stress decreased the storage of K⁺, P and N in sixth leaf and roots in Ghods cultivar. In the both cultivars, PBZ treatment enhanced the K⁺, P and N contents in sixth leaf and roots by increasing salinity. Although PBZ treatment decreased the growth of plants, it improved the weight of seeds against stress damage. PBZ treatment reduced the accumulation of harmful Na⁺ ion in plant tissues while increased the K⁺, P and N contents. These observations suggest that PBZ treatment may increase tolerance by diminishing ionic imbalance caused by salt stress.     

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.     

Salicylic acid mitigates salinity stress by improving antioxidant defence system and enhances vincristine and vinblastine alkaloids production in periwinkle [<Emphasis Type="Italic">Catharanthus roseus</Emphasis> (L.) G. Don]

A pot experiment was conducted to find out whether the foliar spray of salicylic acid (SA) could successfully ameliorate the adverse effects of salinity stress on periwinkle. Thirty-day-old plants were supplied with Control; 0 mM NaCl + 10⁻⁵ M SA (T₁); 50 mM NaCl + 0 SA (T₂); 100 mM NaCl + 0 SA (T₃); 150 mM NaCl + 0 SA (T₄); 50 mM NaCl + 10⁻⁵ M SA (T₅); 100 mM NaCl + 10⁻⁵ M SA (T₆); 150 mM NaCl + 10⁻⁵ M SA (T₇). The plants were sampled 90 days after sowing to assess the effect of SA on stressed and unstressed plants. Salt stress significantly reduced the growth attributes including plant height, leaf-area index, shoot and root fresh weights, shoot and root dry weights. Increasing NaCl concentrations led to a gradual decrease in photosynthetic parameters and activities of nitrate reductase and carbonic anhydrase. Ascorbic acid, total alkaloids and antioxidants enzymes superoxide dismutase, catalase and peroxidase also declined in NaCl-treated plants. The plants, undergoing NaCl stress, exhibited a significant increase in electrolyte leakage and proline content. Foliar application of SA (10⁻⁵ M) reduced the damaging effect of salinity on plant growth and accelerated the restoration of growth processes. It not only improved the growth parameters but also reversed the effects of salinity. Total alkaloid content was improved by SA application both in unstressed and stressed plants. The highest level of total alkaloid content recorded in leaves of SA-treated stressed plants was 11.1%. Foliar spray of SA overcame the adverse effect of salinity by improving the content of vincristine (14.0%) and vinblastine (14.6%) in plants treated with 100 M NaCl.