Adverse Effects Of Salt Stress Research Articles

Role of Nitrogen and Gibberellin (GA3) in the Regulation of Enzyme Activities and in Osmoprotectant Accumulation in Brassica juncea L. under Salt Stress

AbstractSalt stress alters a wide array of plant metabolic mechanisms. Different strategies of the application of nutrients and phytohormones are required to overcome the adverse effects of salt stress. The main objective of the present study was to determine if added nitrogen (N) and gibberellin (GA3) in growth medium could alleviate the adverse effects of salt stress on plant metabolism. Two‐week‐old plants were fed with: (i) 0 mm NaCl + 0 mg N kg−1 sand + 0 m GA3 (control), (ii) 100 mm NaCl + 0 mg N kg−1 sand + 0 m GA3, (iii) 0 mm NaCl + 40 mg N kg−1 sand + 0 m GA3, (iv) 0 mm NaCl + 0 mg N kg−1 sand + 10−5 m GA3, (v) 100 mm NaCl + 40 mg N kg−1 sand + 0 m GA3, (vi) 100 mm NaCl + 0 mg N kg−1 sand + 10−5 m GA3, (vii) 100 mm NaCl + 40 mg N kg−1 sand + 10−5 m GA3. Growth and physio‐biochemical attributes i.e. shoot length, leaf area, fresh weight, dry weight, net photosynthetic rate, stomatal conductance, malondialdehyde concentration, electrolyte leakage, total chlorophyll concentration, nitrate reductase and carbonic anhydrase activities, proline and glycinebetaine concentration, leaf – N, potassium (K) and sodium (Na) concentration and K/Na ratio were affected by NaCl treatment. But application of N or GA3 alone as well as in combination proved beneficial in alleviating the adverse effects of salt stress on these growth and physio‐biochemical parameters. However, N applied with GA3 proved more effective than N and GA3 applied alone. The results revealed that combined application of N and GA3 may ameliorate most of the attributes and prove to be a physiological remedy to increase the tolerance against the ill effects of salt stress in Brassica.

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

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

Exogenously applied ascorbic acid alleviates salt-induced oxidative stress in wheat

Although ascorbic acid (AsA) is one of the most important and abundantly occurring water soluble antioxidants in plants, relatively little is known about its role in counteracting the adverse effects of salt stress on plant growth. To address this issue that whether exogenous application of ascorbic acid (AsA) through rooting medium could alleviate the adverse effects of salt stress on wheat plants, a hydroponic experiment was conducted under glasshouse conditions using two wheat cultivars, S-24 (salt tolerant) and MH-97 (moderately salt sensitive). Plants of both cultivars were subjected to 0 or 150 mM NaCl solution supplemented with 0, 50, or 150 mg L −1 AsA for 58 days. Imposition of salt stress reduced the growth of both wheat cultivars by causing reduction in photosynthesis, and endogenous AsA level, and enhancing accumulation of Na + and Cl − coupled with a decrease in K + and Ca 2+ in the leaves and roots of both cultivars thereby decreasing tissue K +/Na + ratio. However, root applied AsA counteracted the adverse effects of salt stress on the growth of cv. S-24 only, particularly at 100 mg L −1 AsA level. AsA-induced enhancement in growth of salt-stressed plants of S-24 was associated with enhanced endogenous AsA level and CAT activity, and higher photosynthetic capacity, and accumulation of K + and Ca 2+ in the leaves. Although root applied AsA did not improve the growth of salt-stressed plants of MH-97, it enhanced endogenous level of AsA, CAT activity, photosynthetic capacity, and leaf K + and Ca 2+. These findings led us to conclude that root applied AsA counteracts the adverse effects of salt stress on growth of wheat by improving photosynthetic capacity of wheat plants against salt-induced oxidative stress and maintaining ion homeostasis, however, these effects were cultivar specific.

Seed Preconditioning Modulates Growth, Ionic Relations, and Photosynthetic Capacity in Adult Plants of Hexaploid Wheat under Salt Stress

ABSTRACT In order to assess whether seed priming could improve salt tolerance in spring wheat (Triticum aestivum L.) a study was carried out by soaking the seeds of two cultivars, MH-97 (salt sensitive) and Inqlab-91 (salt tolerant), for 12 h in distilled water or 100 mol m–3 of calcium chloride (CaCl2), potassium chloride (KCl), or sodium chloride (NaCl). The primed seeds (P-seeds) of each treatment and non-primed seeds (NP-seeds) were sown in a field in which NaCl salinity of 15 dS m− 1 was developed. Calcium chloride followed by KCl and NaCl was found to be effective in alleviating the adverse effect of salt stress on both cultivars of wheat in terms of biomass production, grain yield, and net CO2 assimilation rate. Although all priming agents were found to be effective in reducing the shoot Na+ levels in both cultivars, the effect of KCl was very pronounced, because it significantly reduced shoot Na+ in both cultivars under saline conditions. In conclusion, although all three priming agents CaCl2, KCl, and NaCl, were effective in alleviating the adverse effect of salt stress on wheat plants, their effects on altering the levels of different ions and photosynthetic rate were different in the two cultivars.

Gibberellic Acid (GA3) Enhance Seed Water Uptake, Germination and Early Seedling Growth in Sugar Beet under Salt Stress

The study was carried out to assess whether water uptake could be improved in sugar beet seeds and salt tolerance at the germination and early seedling stage by soaking the seeds for 10 h in distilled water (control), 100, 150 and 200 mg L(-1) GA3. Electrical Conductivity (EC) values of the NaCl solution were 0.0 (control), 4.7, 9.4 and 14.1 dS n(-1) NaCl. Priming increased the final germination percentage and the germination rate (1/t 50, where t 50 is the time to 50% of germination) under saline condition. Water uptake of primed seeds also increased significantly with increasing concentration of GA3 as compared to control. Priming also alleviated the adverse effect of salt stress on sugar beet in terms of roots and shoots lengths and fresh weights of plants, roots and shoots.

Glycinebetaine-induced modulation of antioxidant enzymes activities and ion accumulation in two wheat cultivars differing in salt tolerance

Modulation of water relations, activities of antioxidant enzymes and ion accumulation was assessed in the plants of two wheat cultivars S-24 (salt tolerant) and MH-97 (moderately salt sensitive) subjected to saline conditions and glycinebetaine (GB) applied foliarly. Different levels of GB, i.e., 0 (unsprayed), 50 and 100 mM (in 0.10% Tween-20 solution) were applied to the wheat plants at the vegetative growth stage. Leaf water potential, leaf osmotic potential and turgor potential were decreased due to salt stress. Salt stress increased the Na + and Cl − accumulation coupled with a decrease in K + and Ca 2+ in the leaves and roots of both cultivars thereby decreasing tissue K +/Na + and Ca 2+/Na + ratios. Furthermore, salt stress decreased the activities of superoxide dismutase (SOD), whereas it increased the activities of catalase (CAT) and peroxidase (POD) in both wheat cultivars. However, accumulation of GB in the leaves of both wheat cultivars was consistently increased with an increase in concentration of exogenous GB application under both non-saline and saline conditions. Accumulation of Na + was decreased with an increase in K + accumulation upon a consistent increase in GB accumulation under salt stress conditions thereby resulting in better K +/Na + and Ca 2+/Na + ratios in the leaves and roots. High accumulation of GB and K + mainly contributed to osmotic adjustment, which is one of the factors known to be responsible for improving growth and yield under salt stress. The activities of all antioxidant enzymes, SOD, CAT and POD were enhanced by GB application in cv. MH-97 under saline conditions, whereas all these except SOD were reduced in cv. S-24. It is likely that both applied GB and intrinsic SOD scavenged ROS in the tolerant cultivar thereby resulting into low activities of CAT and POD enzymes under salt stress. In conclusion, the adverse effects of salt stress on wheat can be alleviated by the exogenous application of 100 mM GB by modulating activities of antioxidant enzymes and changes in water relations and ion homeostasis. Furthermore, effectiveness of GB application on regulation of activities of antioxidant enzymes was found to be cultivar-specific.

Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress?

AbstractIn order to assess whether salt tolerance could be improved in spring wheat (Triticum aestivum L.), the present study was performed by soaking the seeds of two cultivars, namely MH‐97 (salt sensitive) and Inqlab‐91 (salt tolerant), for 12 h in distilled water or 100 mol/m3 CaCl2, KCl, or NaCl. Primed seeds from each treatment group and non‐primed seeds were sown in a field in which NaCl salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCl and NaCl, was found to be effective in alleviating the adverse effects of salt stress on both wheat cultivars in terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance in plants of both cultivars. In MH‐97 plants, CaCl2 pretreatment considerably reduced leaf abscisic acid (ABA) concentrations and increased leaf free salicylic acid (SA) concentrations under both saline and non‐saline conditions. In contrast, in the Inqlab‐91 plant, CaCl2 increased free indoleacetic acid (IAA) and indolebutyric acid (IBA) content. However, priming of seeds with CaCl2 did not alter free polyamine levels in either cultivar, although spermidine levels were considerably lower in plants raised from seeds treated with CaCl2 for both cultivars under saline conditions. Priming with KCl increased growth in Inqlab‐91 plants, but not in MH‐97 plants, under saline conditions. The salinity induced reduction in auxins (IAA and IBA) was alleviated by NaCl priming in both cultivars under saline conditions. However, NaCl increased leaf free ABA content and lowered leaf SA and putrescine levels in Inqlab‐91 plants under saline conditions. In conclusion, although all three priming agents (i.e. CaCl2, KCl, and NaCl) were effective in alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different in the two cultivars.(Managing editor: Ping He)

Presowing Seed Treatment with Cytokinins and Its Effect on Growth, Photosynthetic Rate, Ionic Levels and Yield of Two Wheat Cultivars Differing in Salt Tolerance

Abstract: The effects of presowing seed treatment with different concentrations of cytokinins (kinetin and benzylaminopurine; 100, 150, and 200 mg/L) on growth, photosynthetic capacity, and ion homeostasis were investigated in two spring wheat (Triticum aestivum L.) cultivars, namely MH-97 (salt sensitive) and Inqlab-91 (salt tolerant). Primed and non-primed seeds were sown in a field in which NaCl salinity of 15 dS/m was developed. Of the different concentrations of priming agents tested, the effect of a moderate concentration of kinetin (150 mg/L) was very pronounced, particularly in improving growth and grain yield, in both cultivars. In addition, priming with kinetin alleviated the adverse effect of salt stress on gaseous exchange characteristics (net CO2 assimilation rate and water use efficiency) in both cultivars. Seed priming with a moderate concentration of kinetin also altered the pattern of accumulation of Na+ and Cl− in the shoots, irrespective of the wheat cultivar, under conditions of salt stress. However, all other priming agents at the different concentrations tested did not show any consistent effect on ion levels, except hydropriming, which increased K+ levels in the shoots of both cultivars under salt stress. In conclusion, a moderate concentration of kinetin showed a consistent effect in altering the growth and grain yield of both wheat cultivars, which was related to the beneficial effects of kinetin priming on water use efficiency and photosynthetic rate under conditions of salt stress. (Managing editor: Ping HE)

Changes in growth, photosynthetic capacity and ionic relations in spring wheat (Triticum aestivum 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 (gs) 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.

Response of salt stressed barley seedlings to phenylurea

The effect of phenylurea with reported cytokinin-like activities on seed germination, seedling growth, activities of antioxidant enzymes, polyphenol, peroxidase, indoleacetic acid oxidase, and total phenolic compounds, flavonoids was investigated in stressed barley seedlings. The application of phenylurea decreases the activity of peroxidase, indoleacetic acid oxidase and increases the activity of polyphenol oxidase with decrease in total phenolic compounds and flavonoids and consequent increase in growth rate. Saline (NaCl) stress in barley seedlings causes an increase in total phenolic compounds, flavonoids and enhancement of peroxidase and indoleacetic acid oxidase activities and consequent decrease in growth rate. The adverse effect of salt stress on germination, antioxidant enzymes, phenolic compounds, flavonoids can partially be rectified by phenylurea.

Interactive effects of gibberellic acid (GA3) and salt stress on growth, ion accumulation and photosynthetic capacity of two spring wheat (Triticum aestivum L.) cultivars differing in salt tolerance

A sand culture experiment assessed whether gibberellic acid(GA3) could alleviate the adverse effects of salt stress on thegrowth, ion accumulation and photosynthetic capacity of two spring wheatcultivars, Barani-83 (salt sensitive) and SARC-I (salt tolerant).Three-week-oldplants of both cultivars were exposed to 0, 100 and 200 molm−3 NaCl in Hoagland's nutrient solution. Threeweeks after the initiation of salt treatments, half of the plants of eachcultivar were sprayed overall with 100 mg L−1GA3 solution. Plants were harvested 3 weeks after theapplication of GA3. Fresh and dry weights of shoots and roots, plantheight and leaf area were decreased with increasing supply of salt, butgibberellic acid treatment caused a significant ameliorative effect on both thecultivars with respect to these growth attributes. However, GA3caused no significant change in grain yields but increased grain size in boththe cultivars. Saline growth medium caused a marked increase in theconcentrations of Na+ and Cl− in shoots androots of both the lines. However, with the application of GA3accumulation of Na+ and Cl− was enhanced inboth shoots and roots of both wheat lines, but more ions accumulated in saltsensitive Barani-83 than in salt tolerant SARC-1. Net CO2assimilation rate (A) of both wheat lines decreased consistently withincreasingsupply of NaCl, but application of GA3 alleviated the effect of saltstress on this variable in both the cultivars. However, the ameliorative effectof the hormone was more pronounced in Barani-83 than in SARC-1. Althoughwater-use efficiency (A/E = CO2assimilation/transpiration) and intrinsic water use efficiency(A/gs = CO2 assimilation/stomatalconductance) decreased significantly with increasing salt concentration of thegrowth medium in both the cultivars, GA3 was more effective inenhancing both the water-use attributes in Barani-83 than in SARC-1. Overall,GA3 treatment stimulated the vegetative growth of both cultivars ofwheat under salt stress, but it caused a slight reduction in grain yield.GA3 treatment enhanced the accumulation of Na+ andCl− in both shoots and roots of wheat plants under saltstress.It also caused a significant increase in photosynthetic capacity in both linesat the vegetative stage under both saline and non-saline media.

Inducing salt tolerance in maize (Zea mays L.) through seed priming with chloride salts: Growth and ion transport at early growth stages

The study was conducted to determine whether salt tolerance could be induced in maize at germination stage by soaking of seeds for 8 h in distilled water or in 200 meq·L−1 of NaCl, KCl, CaCl2·2H2O. Both primed and un-primed seeds were subjected for 14 days to 0, 100 or 200 mol·m−3 NaCl under controlled conditions. Although all priming agents were effective in alleviating adverse effects of salt stress on maize at germination stage, CaCl2·2H2O proved to be more effective since the seeds primed with this salt had significantly higher final germination, rate of germination and fresh and dry weights of plumules and radicles than those treated with other salts or distilled water. Concentration of Na+, K+ and Ca2+ increased significantly in all parts of germinating seeds of maize seeds primed with NaCl, KCl, or CaCl2·2H2O, respectively. In addition, seeds primed with CaCl2·2H2O were the highest in Cl− accumulation in all parts of the germinating seeds, followed by seeds treated with NaCl and KCl. Most of the Ca2+ was retained in seeds and mesocotyl, because of which, transport of this ion to plumules and radicles was low.

GERMINATION, SODIUM, AND POTASSIUM CONCENTRATIONS OF BARLEY SEEDS AS INFLUENCED BY SALINITY

Seed germination is a major factor limiting the establishment of plants under saline conditions. Six barley (Hordeum vulgare L.) cultivars were screened for salt tolerance (using NaCl) during seed germination. The uptake of water, and levels of Na+ and K+ of salt sensitive and salt tolerant cultivars, before and after imbibition, were measured to determine the contributions of ionic and osmotic factors to seed different response to salt stress. Imbibition of seeds incubated with NaCl solutions was reduced by approximately 5% for each 100mM increase in NaCl concentration once the level of 100mM NaCl was reached. The Na+ concentration of seeds after imbibition did not differ significantly among cultivars and selective uptake or exclusion of Na+ were not associated with the differences in salinity tolerance. No differences between the two tested cultivars were noted for initial K+ concentration, but the salt tolerant cultivar lost less K+ relative to Na+ uptake than did the salt sensitive cultivar. The adverse effects of salt stress on seed germination might result from internal osmotic or restricted imbibition rather than from ion toxicity effects.

585 Indole Acetic Acid Reduced Some Adverse Effects of Salt Stress on Date Palm Seedlings

An experiment was conducted at the United Arab Emirates Univ., in Al-Ain, to study the effect of saline water on the growth characteristics of date palm (Phoenix dactylifera L.) seedings cultivar Lulu-salt alone or a combination of NaCl and indole acetic acid (IAA) or IAA alone were tested with different levels. Then the plant growth characteristics were measured. Hormone did not antagonize the salt effect on shoot length of date palm seedlings. Application of 24 mg·L–1 salt alone or in combination with hormone and 12 mg·L–1 in combination with 0.2 mg·L–1 IAA significantly increased the root: shoot ratio over the control. Irrigation date palm seedlings with saline water alone or in combination with IAA for 80 days resulted in a significant increase in dry matter (percentage) of leaves with salt symptoms, whereas the number of leaves per seedling were reduced over the control. The results also showed that the irrigation of seedlings with 0.15 mg·L–1 IAA in combination with 24 or 12 mg·L–1 salt alleviated adverse effect of salt by increasing or reducing significantly root length or leaves with salt symptoms percentage over using 24 or 12 mg·L–1 salt alone.

Interactions between Ca, Na, and K inSalicornia virginicaand barley roots under saline conditions: multi- compartment transport box experiment

Abstract The interrelationships between Ca, Na, and K in excised Salicornia (Salicornia virginica L.) and barley (Hordeum vulgare L. cv. Akashinriki) roots under saline conditions were determined using multi-compartment transport boxes. The results showed that Ca considerably depressed Na absorption and translocation in both Salicornia and barley roots. This depressing effect of Ca on Na uptake was more pronounced in barley than in Salicornia roots. High concentrations of NaCl (50 and 150 mM) inhibited the absorption and translocation of K in the roots of both plants in the absence of Ca, especially in barley. Ca addition, however, greatly alleviated the adverse effect of NaCl on K uptake in both Salicornia and barley roots. In contrast to barley, high concentrations of NaCl appeared to stimulate K uptake in Salicornia roots in the presence of Ca. Salicornia seems to be more effective than barley in protecting the K nutrition in its roots from the adverse effect of salt stress. The findings show that Sali...

Seed Polymorphism and Germination Responses to Salinity Stress in Atriplex triangularis Willd.

Seeds of Atriplex triangularis exhibited a very pronounced morphological and physiological seed polymorphism. Seed size varied from 1.0 to 2.8 mm and predicted the likelihood of successful establishment through its effect on germination and seedling vigor. Large seeds had a mean dry weight of 2.44 ± 0.16 mg and a mean length of 2.45 ± 0.24 mm; medium seeds, mean dry weight of 1.21 ± 0.10 mg and mean length of 1.78 ± 0.19 mm; small seeds, mean dry weight of 0.64 ± 0.04 mg and mean length of 1.27 ± 0.10 mm. The degree of salt tolerance increased progressively with increasing seed size. Seeds from all size classes that were initially treated with 2%-5% NaCl had from 85% to 100% germination after being immersed in distilled water for 6 days, indicating a transitory adverse effect of salt stress on germination. The amount of water absorbed by all seeds is influenced by change in media salinity but not by hormonal treatments. Small seeds contain more Na+ and Cl- than medium and large seeds. Seedling dry weight was related to initial seed size. Salt stress inhibited seedling growth. Gibberellic acid alleviated some of the dormancy in seeds induced by high salt concentrations.