Different Levels Of Salt Stress Research Articles

Amelioration of high salinity stress damage by plant growth-promoting bacterial endophytes that contain ACC deaminase

Plant growth and productivity is negatively affected by soil salinity. However, it is predicted that plant growth-promoting bacterial (PGPB) endophytes that contain 1-aminocyclopropane-1-carboxylate (ACC) deaminase (E.C. 4.1.99.4) can facilitate plant growth and development in the presence of a number of different stresses. In present study, the ability of ACC deaminase containing PGPB endophytes Pseudomonas fluorescens YsS6, Pseudomonas migulae 8R6, and their ACC deaminase deficient mutants to promote tomato plant growth in the absence of salt and under two different levels of salt stress (165 mM and 185 mM) was assessed. It was evidence that wild-type bacterial endophytes (P. fluorescens YsS6 and P. migulae 8R6) promoted tomato plant growth significantly even in the absence of stress (salinity). Plants pretreated with wild-type ACC deaminase containing endophytic strains were healthier and grew to a much larger size under high salinity stress compared to plants pretreated with the ACC deaminase deficient mutants or no bacterial treatment (control). The plants pretreated with ACC deaminase containing bacterial endophytes exhibit higher fresh and dry biomass, higher chlorophyll contents, and a greater number of flowers and buds than the other treatments. Since the only difference between wild-type and mutant bacterial endophytes was ACC deaminase activity, it is concluded that this enzyme is directly responsible for the different behavior of tomato plants in response to salt stress. The use of PGPB endophytes with ACC deaminase activity has the potential to facilitate plant growth on land that is not normally suitable for the majority of crops due to their high salt contents.

Effect of salt stress on tomato fruit antioxidant systems depends on fruit development stage

The effects of different levels of salt stress on the oxidative parameters (H2O2 and MDA), the total pool sizes of ascorbate, the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as the activities and relative transcript levels of the enzymes of ascorbate-glutathione cycle; ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were studied in fruits of tomato. Plants were treated by three concentrations of NaCl (50, 100 and 150mM) and fruits at different development stages were harvested after 3 and 6days of stress. The concentrations of ascorbate (AsA) and dehydroascorbate (DHA) generally changed with salt stress treatments. Moreover, changes in SOD and CAT activities and DHAR, MDHAR, APX and GR activities and relative transcript levels were dependent on the fruit development stage and the intensity and duration of salt stress. These results suggest that the response of antioxidant systems of tomato fruits to oxidative stress induced by salt stress treatments was different depending on the fruit development stage.

OP012 The role of H2S in pepper leaves under salt stress conditions

In plants high concentrations of hydrogen sulfide (H 2 S) can inhibit enzymes such as cytochrome oxidase. Based on this, and its similar inhibitory effects, H 2 S has commonly been thought of as a phytotoxin. However, at lower concentrations, it may act in a more positive manner. Many plant species have been found to generate H 2 S suggesting that it may be an endogenous chemical and suitable to be considered as signalling molecule. There is a growing body of evidence to suggest that the presence of this gasotransmitter may impact on oxidative stress metabolism in plants. The treatment of plant cells with H 2 S affects both cysteine and glutathione metabolism but are there other plant physiological pathways which can be affected by H 2 S? The activity of stress-related enzymes and also the content of some specific metabolites are often used as physiological stress response parameters. In greenhouse growing, plants are often exposed to unfavorable growth conditions due the salt stress, while at the same time numerous H 2 S-based preparations are often used as fungicides. Thus, our study aimed to further explore the potential role of H 2 S in plant physiological pathways, with a particular focus on the possible protective role of H 2 S in salt stress conditions. Pepper plants grown in substrate under fully controlled conditions were pre-treated with H 2 S donors (NaHS, GYY4137) and exposed to the three different levels of salt stress. Significant differences between individual treatments and pre-treatments were observed. Total activity of catalase, glutathione reductase and guaiacol peroxidase were significantly increased at 100 and 200 mM NaCl. The applied salt stress treatments increased lipid peroxidation rates as well as free proline and hydrogen peroxide content. In general, both H 2 S donors decreased lipid peroxidation levels in leaves, while NaHS reduced free proline and hydrogen peroxide content. Salt stressed plants pretreated with GYY4137 showed significantly higher free proline content. The results suggest that H 2 S may have a protective role in the case of salt stress, through increasing enzymatic activity and the accumulation of stress protective metabolites such as proline. Lowered lipid peroxidation in plants pre-treated with H 2 S donors implies that this gasotransmitter can protect cell membranes constituents from chain destruction, whether through direct involvement in ROS neutralization, or through the synthesis of important antioxidants such as glutathione.

Maize germination parameters and early seedlings growth under different levels of salt stress

Increased salt concentration has a negative effect on germination parameters and early seedling growth. The objective of this study was to evaluate germination parameters and early seedlings growth of maize under different salinity conditions (0, -0.3, -0.6, -0.9 and -1.2 MPa). Germination was tested in double rolled filter paper, moistened with different NaCl solution, in the dark at 25°C. Osmotic stress had significant effects on all examined characteristics, except on final germination. Under the highest osmotic stress, mean germination time and time to 50% germination were 14 h and 30 h longer than at control. Root and shoot length under those conditions (-1.2 MPa) were 76% and 87% shorter compared to control, while root and shoot weight were reduced (81% and 87%). Minor reduction in germination energy was recorded under stress. These results showed different responses of germination parameters and early seedling growth in the observed genotype under different salinity conditions.

Salinity Impact on Growth, Essential Oil Content and Composition of Coriander (Coriandrum sativum L.) Stems and Leaves

The influence of salt stress on vegetative growth, essential oil content, and composition of Tunisian coriander (Coriandrum sativum L.) grown in hydroponic culture was investigated. The volatile constituents of stems and leaves were isolated by hydrodistillation and analyzed by GC and GC/MS. Seedlings were treated with different levels of salt stress (25 mM, 50 mM and 75 mM NaCl). Results showed that the stem and leaf biomasses were not affected under 25 mM NaCl, compared to the control, although it decreased significantly at 50 mM and 75 mM. Essential oil content was 1762.64 μ/g DW (0.18%) and 1255.77 μ/g DW (0.12%) in stems and leaves, respectively. At low and moderate stress, a significant difference in the essential oil content was developed between stems, with a significant decrease, and leaves, with an increase up to 43%. Under high salinity, the oil content of both organs decreased significantly. The major volatile compound of stems and leaves was (E)-2-decenal with 24% and 52%, respectively. Other important components were decanal, (E)-2-dodecenal, dodecanal, (E)-2-undecenal, (E)-2-tridecenal and (E)-2-undecanal. Further, the content of these compounds were affected differently by the treatment level and by the organ type.

Reproductive Compensation of Cotton after Salt Stress Relief at Different Growth Stages

AbstractDifferential salt sensitivity during growth stages and reproductive compensation of plants after salt stress relief are important factors for adopting appropriate irrigation strategies with saline waters. Consequently, recovery of cotton after exposure to different levels of salt stress was evaluated. An outdoor, sand culture experiment was conducted with cotton. Water salinities were 2, 10 and 20 dS m−1, and the growth phases were vegetative (G1), reproductive (G2) and boll development (G3). G1 and G3 were the least and the most salt tolerant phases, respectively. The significant yield reduction in all of the saline water treatments as compared to control was mainly due to the reduction in number of bolls per plants. In general, cotton plants were capable of producing seed cotton under salt stress, as well as, after salt stress relief. However, as the salt stress severity increased the ability of cotton to compensate yield loss decreased. Irrigation of cotton at G1 stage with either moderate (10 dS m−1) or high (20 dS m−1) salinity waters should be avoided. Moderate saline water could be applied either at G2 or G3 stage. High salinity water can be used for irrigation only at G3 stage to produce acceptable cotton seed yield.

Differential expression of LEA proteins in two genotypes of mulberry under salinity

The relative water content (RWC), cell membrane integrity, protein pattern and the expression of late embryogenesis abundant proteins (LEA; group 1, 2, 3 and 4) under different levels of salt stress (0, 1.0, 1.5 and 2.0 % NaCl) were investigated in mulberry (Morus alba L.) cultivars (S1 and ATP) with contrasting salt tolerance. RWC and membrane integrity decreased with increase in NaCl concentration more in cv. ATP than in cv. S1. SDS-PAGE protein profile of mulberry leaves after the NaCl treatments showed a significant increase in 35, 41, 45 and 70 kDa proteins and significant decrease in 14.3, 18, 23, 28, 30, 42, 47 and 65 kDa proteins. Exposure of plants to NaCl resulted in higher accumulation of LEA proteins in S1 than ATP. The maximum content of LEA (group 3 and 4) was detected in S1 at 2.0 % NaCl, which correlates with its salt tolerance.

Induction of antioxidant enzymes is involved in the greater effectiveness of a PGPR versus AM fungi with respect to increasing the tolerance of lettuce to severe salt stress

This study investigated the influence of inoculation with a plant growth-promoting rhizobacterium, Pseudomonas mendocina Palleroni, alone or in combination with an arbuscular mycorrhizal (AM) fungus, Glomus intraradices (Schenk & Smith) or Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, on antioxidant enzyme activities (catalase and total peroxidase), phosphatase activity, solute accumulation, growth and mineral nutrient uptake in leaves of Lactuca sativa L. cv. Tafalla affected by three different levels of salt stress. Salinity decreased lettuce growth, regardless of the biological treatment and of the salt stress level. The plants inoculated with P. mendocina had significantly greater shoot biomass than the control plants at both salinity levels, whereas the mycorrhizal inoculation treatments only were effective in increasing shoot biomass at the medium salinity level. At the highest salinity level, the water content was greater in leaves of plants treated with P. mendocina or G. mosseae. At the medium salinity level, G. intraradices- or G. mosseae-colonised plants showed the highest concentrations of foliar P. The P. mendocina- and G. mosseae-colonised plants presented higher concentrations of foliar K and lower concentrations of foliar Na under high salt conditions. Salt stress decreased sugar accumulation and increased foliar proline concentration, particularly in plants inoculated with the PGPR. Increasing salinity stress raised significantly the antioxidant enzyme activities, including those of total peroxidase and catalase, of lettuce leaves compared to their respective non-stressed controls. The PGPR strain induced a higher increase in these antioxidant enzymes in response to severe salinity. Inoculation with selected PGPR could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

NaCl effects on proline metabolism in two high yielding genotypes of mulberry ( Morus alba L.) with contrasting salt tolerance

The effect of salt stress was studied on free proline accumulation, activities of pyrroline-5-carboxylate reductase (P-5-CR), proline oxidase and proline dehydrogenase (PDH), glycinebetaine levels and chlorophyll stability in two cultivars of mulberry (S1 and ATP, salt tolerant and salt sensitive, respectively), at different levels of salt stress (0.0 (control), 0.5, 1.0 and 1.5% NaCl). Salt stress resulted in a significant accumulation of free proline in leaves of both the cultivars under salt stress. The magnitude of increase in free proline accumulation was higher in the tolerant cultivar than in the sensitive cultivar. Salt stress resulted in an accumulation of proline by six-fold in S1 and four-fold in ATP on day 12 at 1.5% NaCl stress. Pyrroline-5-carboxylate reductase activity increased in both cultivars and the magnitude of increase was more in S1 than in ATP. In addition, the activities of proline oxidase and proline dehydrogenase were inhibited under salt stress in both cultivars. Nevertheless, the reduction in the activity was more in S1 than in ATP. The greater proline levels were due to both the higher rates of proline synthesis and lower magnitude of proline oxidation in S1 compared to ATP. The results indicated that during salt stress, proline metabolism was significantly altered and the extent of alteration varied between the cultivars S1 and ATP, leading to the maintenance of the turgor by accumulating higher levels of free proline in S1, supporting its salt tolerance. Further, salt tolerance of S1 was evident from the higher level accumulation of glycine betaine (GB) compared with ATP during salt stress. Furthermore, the salt tolerance of S1 was indicated by lower amounts of chlorophyll degradation. The physiological significance of recorded changes are analyzed in relation to the functions of these enzymes in plant metabolism under salt stress.