Negative Effects Of Salinity Stress Research Articles

Applications of polysaccharides (β-glucan) for physiological and biochemical parameters for evaluation rice tolerance under salinity stress at seedling stage

Salt stress is considered to be the most important abiotic stress and is the main problem in the interruption of the metabolic processes of plants, thereby limiting crop production. The present study was carried out to examine the effects of exogenously applied mushroom polysaccharides (β-glucan) on the growth of two rice varieties of Oryza sativa L. (MRQ74 and MR269) seedlings grown in vitro in 200 Mm sodium chloride (NaCl). Growth characteristics, including shoot and root height, and fresh and dry weight of salt-stressed rice seedlings were inhibited by sodium chloride treatment, the degree of which depends on the rice variety. The negative effects of salinity stress resulted in an imbalance of N, K+ Na+ and Na/K ratios and biochemical analysis activities a degradation of chlorophyll content in the plants. However, treatment with exogenously applied polysaccharides (β-glucan) ameliorated the stress generated by NaCl and improved the parameters mentioned above. The significance of the changes in growth and metabolism to salt stress tolerance in rice seedlings are discussed in the paper.

Attenuation of Negative Effects of Saline Stress in two Lettuce Cultivars by Salicylic Acid and Glycine Betaine

Reducing destructive effects of lettuce plants irrigated with saline water was investigated in two field experiments conducted at Ismailia Governorate in 2012–2013 and 2013–2014. Two lettuce (Lactuca sativa L.) cultivars, Great Lakes and Balady, irrigated with saline water (3.22 dS/m) were treated using two levels of salicylic acid (SA) and glycine betaine (GB) as a foliar application (200, 400 ppm and 15, 30 Mm, respectively). Generally, application of SA and GB enhanced growth parameters, i. e. plant height; root length; number of leaves per plant; plant fresh and dry weight; leaf relative water content (LRWC); membrane permeability (MP); lipid peroxidation (MDA); chlorophyll a, b and carotenoid content in leaf; proline; total soluble sugars (TSS); superoxide dismutase (SOD) and peroxidase (POD) activity; and Na, K, Ca content. GB treatments significantly increased most recorded growth parameters, especially at 30 mM, while this treatment decreased values of MP, (MDA) and Na content in two lettuce cultivars.

THE EFFECT OF SALINITY PRETREATMENT OF GLOMUS MOSSEAE ON INDUCTION OF SALINITY TOLERANCE IN LYCOPERSICUM ESCULENTUM L.

Tomato (Lycpoersicum esculemtum) belongs to the Solanaceae potato family and is an important crop plant. It is relatively resistant to salinity, but in the saline environment growth and production of the plant significantly reduces. On the other hand, the presence of mycorrhiza fungus can improve the adverse effects of salinity. A factorial experiment in a completely randomized design with three replications was conducted on tomato plants in the Islamic Azad University. The first factor was mycorrhiza treatment with NaCl at 0 (control), 50, and 100 mM, and the second factor included salinity stress at 0 (control), 50, 100, and 200 mM. Based on the obtained results from variance analysis, the effects of mycorrhiza pretreatment with NaCl were significant on the root length. Also, the level of salinity pretreatment of mycorrhiza had a significant effect on proline content (p≤0.05). Moreover, salinity treatment had a significant effect on stem length, leaf area, the inoculation percentage of mycorrhiza, and proline content (p≤0.01) and on stem length (p≤0.05). Moreover, salinity pretreatment of mycorrhiza and salinity treatment reduced root length, the inoculation percentage of mycorrhiza, and proline accumulation. Salinity treatment reduced root length, leaf area, stem length, and the inoculation percentage of mycorrhiza while it increased proline content. Finally, it was found that salinity stress reduced the root length, stem length, leaf area, leaf water content, the inoculation percentage of mycorrhiza, potassium, phosphorous, and nitrogen while it increased the proline content. Finally, mycorrhiza pretreatment with NaCl was found to reduce the negative effects of salinity stress.

External potassium (K+) application improves salinity tolerance by promoting Na+-exclusion, K+-accumulation and osmotic adjustment in contrasting peanut cultivars

Achieving salt-tolerance is highly desirable in today's agricultural context. Apart from developing salt-tolerant cultivars, possibility lies with management options, which can improve crop yield and have significant impact on crop physiology as well. Thus present study was aimed to evaluate the ameliorative role of potassium (K+) in salinity tolerance of peanut. A field experiment was conducted using two differentially salt-responsive cultivars and three levels of salinity treatment (control, 2.0 dS m−1, 4.0 dS m−1) along with two levels (with and without) of potassium fertilizer (0 and 30 kg K2O ha−1). Salinity treatment incurred significant changes in overall physiology in two peanut cultivars, though the responses varied between the tolerant and the susceptible one. External K+ application resulted in improved salinity tolerance in terms of plant water status, biomass produced under stress, osmotic adjustment and better ionic balance. Tolerant cv. GG 2 showed better salt tolerance by excluding Na+ from uptake and lesser accumulation in leaf tissue and relied more on organic osmolyte for osmotic adjustment. On the contrary, susceptible cv. TG 37A allowed more Na+ to accumulate in the leaf tissue and relied more on inorganic solute for osmotic adjustment under saline condition, hence showed more susceptibility to salinity stress. Application of K+ resulted in nullifying the negative effect of salinity stress with slightly better response in the susceptible cultivar (TG 37A). The present study identified Na+-exclusion as a key strategy for salt-tolerance in tolerant cv. GG 2 and also showed the ameliorating role of K+ in salt-tolerance with varying degree of response amongst tolerant and susceptible cultivars.

Physiological factors involved in positive effects of elevated carbon dioxide concentration on Bermudagrass tolerance to salinity stress

Salinity stress due to increased use of non-potable water sources for irrigation imposes major limitations on plant growth in salt-affected soils. However, rising atmospheric CO2 concentration may counteract the negative effects of salinity stress. The objective of this study was to determine whether elevated CO2 mitigates salinity stress by influencing physiological activities and/or ion (Na+ and K+) balance in Bermudagrass (Cynodon dactylon cv. ‘Tifway’). Plants were exposed to either ambient CO2 concentration (400μmolmol−1) or elevated CO2 concentration (800μmolmol−1) and maintained well-watered (control) with fresh water or subjected to salinity stress by irrigating plants with NaCl solution (200mM). Salinity stress caused reduction in turf quality (TQ), leaf relative water content (RWC), leaf net photosynthetic rate (Pn), transpiration rate, stomatal conductance, and cellular membrane stability. Elevated CO2 concentration alleviated the depression of those physiological parameters and promoted osmotic adjustment through accumulation of soluble sugars, proline, and glycine betaine (GB) under salinity stress, but had no significant effects on the ratio of Na+ to K+. Our results demonstrated that elevated CO2 concentration was effective in alleviating physiological damages of salinity stress in Bermudagrass, suggesting that C4 grasses may benefit from the rising atmospheric CO2 concentration associated with global climate changes. The positive physiological effects of elevated CO2, as manifested by improved TQ, RWC, Pn and cell membrane stability could be related to the maintenance of cellular hydration associated with osmotic adjustment due to the accumulation of soluble sugars, proline and GB, and the suppression of Na+ accumulation independent of changes in K+ accumulation.

Role of Foliar Application of Nicotinic Acid and Tryptophan on Onion Plants Response to Salinity Stress

This experiment was conducted at the National Research Centre, Dokki, Cairo, Egypt during 2006 and 2007 winter season to evaluate the effects of spraying with tryptophan (TP) and nicotinic acids (NA) on onion plants grown under varying degree of salinity stress (irrigation water with 3000 and 6000 ppm salinity) as compared to tap water (300 ppm) irrigation. Irrigation by high salinity water decreased the number of leaves, mean bulb diameter, fresh and dry weight of bulb and whole plant. Foliar application of TP and NA significantly increased the top height and fresh weight, and bulb dry weight. The above beneficial effects were greater in the plants sprayed with NA as compared to those of the plants received TP spray. At the lower salinity level (3000 ppm), TP was more effective than NA in mitigating the negative effects of salinity stress. At the high salinity stress (6000 ppm), however, the converse was evident. The electrolyte leakage (EL) was not influenced by 3000 ppm salinity irrigation water as compared to that of the plants which received tap water (300 ppm) irrigations. However, it increased significantly in the plants irrigated by 6000 ppm salinity water. Lipid peroxidation (LP) and EL were significantly lower in the plants sprayed with TP or tapwater. In addition, spraying of NA or TP increased the plant growth and biomass weight. Therefore, the above foliar sprays appear to mitigate the negative effects of increased salinity.

Influence of foliar-applied triacontanol on growth, gas exchange characteristics, and chlorophyll fluorescence at different growth stages in wheat under saline conditions

A greenhouse experiment was conducted to examine the effect of foliar application of triacontanol (TRIA) on two cultivars (cv. S-24 and MH-97) of wheat (Triticum aestivum L.) at different growth stages. Plants were grown in full strength Hoagland’s nutrient solution under salt stress (150 mM NaCl) or control (0 mM NaCl) conditions. Three TRIA concentrations (0, 10, and 20 μM) were sprayed over leaves at three different growth stages, i.e. vegetative (V), boot (B), and vegetative + boot (VB) stages (two sprays on same plants, i.e., the first at 30-d-old plants and the second 78-d-old plants). Salt stress decreased significantly growth, net photosynthetic rate (P N), transpiration rate (E), chlorophyll contents (Chl a and b), and electron transport rate (ETR), while membrane permeability increased in both wheat cultivars. Stomatal conductance (g s) decreased only in salt-sensitive cv. MH-97 under saline conditions. Foliar application of TRIA at different growth stages enhanced significantly the growth, P N, g s, Chl a and b contents, and ETR, while membrane permeability was reduced in both cultivars under salt stress. Of various growth stages, foliar-applied TRIA was comparatively more effective when it was applied at V and VB stages. Overall, 10 μM TRIA concentration was the most efficient in reducing negative effects of salinity stress in both wheat cultivars. The cv. S-24 showed the better growth and ETR, while cv. MH-97 exhibited higher nonphotochemical quenching.

Exogenous application of free polyamines enhance salt tolerance of pistachio (Pistacia vera L.) seedlings

The protective effects of free polyamines (PAs) against salinity stress were investigated for pistachio seedlings (Pistacia vera cv. Badami-Zarand) in a controlled greenhouse. Seedlings were treated with 25, 50, 100 and 150 mM of salts including NaCl, CaCl2 and MgCl2. Foliar treatments of putrescine, spermidine (Spd) and spermine (Spm) (0.1 and 1 mM) were applied during the salinity period. Results showed that growth characteristics of pistachio seedlings decreased under salinity stress and the application of PAs efficiently reduced the adverse effects of salt stress. PAs reduced the severe effects of salt stress in pistachio seedlings neither by increasing the activities of peroxidase and ascorbate peroxidase nor by increasing the proline content but by increasing the activities of superoxide dismutase and catalase and decreasing the hydrogen peroxide (H2O2) activity. PAs treated seedlings showed a lower Na+:K+ ratio and Cl− in leaves suggesting the role of PAs in balancing the ion exchange and better Na+:K+ discrimination under salt stress condition. These results showed the promising potential use of PAs especially Spm and Spd for reducing the negative effects of salinity stress and improving the growth of pistachio seedlings.

Proteomic analysis of the enhancement of seed vigour in osmoprimed alfalfa seeds germinated under salinity stress

AbstractAlfalfa (Medicago sativaL.) yield is severely compromised by soil salinity, especially at the level of seedling establishment. This question was addressed by proteomics to decipher whether specific changes in protein accumulation correlate with germination performance of alfalfa seeds submitted to a salinity stress as obtained by imbibing seeds in the presence of NaCl. This study used alfalfa seeds submitted to an osmopriming invigoration treatment that proved very efficient in counteracting the negative effect of salinity stress on germination performance. Comparative proteomic analyses disclosed 94 proteins commonly characterizing the response of both the untreated control and osmoprimed seeds to the experimental salinity stress. Remarkably, many of them, representing 84 proteins, showed contrasting accumulation patterns when comparing the untreated control and osmoprimed seeds submitted to the same salt stress. Thus numerous changes observed in the proteome of the untreated control seeds imbibed in the presence of salt, and presumably accounting for the loss in seed vigour associated with salinity stress, can be substantially reversed in osmoprimed seeds undergoing this stress. These data therefore provide a biochemical understanding of the increase in seed vigour generally observed with primed seeds.

Effects of Si<sup>+</sup>, K<sup>+</sup> and Ca<sup>2+</sup> on Antioxidant Enzyme Activities and Osmolytes in <i>Halocnemum strobilaceum</i> under Salt Stress

We evaluated the effects of silicon , potassium, and calcium on the salt-tolerant plant Halocnemum strobilaceum (Pal.l) Bie under salt stress. The experimental treatments consisted of a NaCl-only treatment (150, 450, or 900 mmol/l NaCl), a complex salts treatment (NaCl with K+, Ca2+ ,andSi+at total concentrations of 150, 450, or 900 mmol/l;(Na+:K+:Ca2+ :Si+ =1:0.03:0.14:0.004), and a control with no complex ions or NaCl. After 20 and 60 days of treatments, we investigated activities of the major antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as succulence and the contents of malondialdehyde (MDA), proline(Pro) and glycine betain (GB). We found that additions of K+ , Ca2+ , and Si+ partially alleviated the negative effects of salinity stress by increasing the salt tolerance of the plant. The improved salt tolerance was associated with increased Pro, GB,and increased activities of SOD, CAT, and POD,and decrease MDA. In contrast, the NaCl-only treatments caused marked decreases in succulence and soluble protein contents. The results of these experiments suggest that K+, Ca2+ , and Si+ can alleviate the damaging effects of salt on H. strobilaceum by preventing oxidative membrane and oxidant enzyme activities damage, and that they may be associated with osmotic adjustment.

Salinity tolerance of 'Valencia' orange trees on rootstocks with contrasting salt tolerance is not improved by moderate shade

The effects of shading in combination with salinity treatments were studied in citrus trees on two rootstocks with contrasting salt tolerance to determine if shading could reduce the negative effects of salinity stress. Well-nourished 2-year-old 'Valencia' orange trees grafted on Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive), were grown either under a 50% shade cloth or left unshaded in full sunlight. Half the trees received no salinity treatment and half were salinized with 50 mM Cl- during two 9 week salinity periods in the spring and autumn interrupted by an 11 week rainy period. The shade treatment reduced midday leaf temperature and leaf-to-air vapour pressure deficit regardless of salinity treatments. In non-salinized trees, shade increased midday CO2 assimilation rate (A(CO2)) and stomatal conductance, but had no effect on leaf transpiration (E(lf)). Shade also increased leaf chlorophyll and photosynthetic water use efficiency (A(CO2)/E(lf)) in leaves on both rootstocks and increased total plant dry weight in Cleo. The salinity treatment reduced leaf growth and leaf gas exchange parameters. Shade decreased Cl- concentrations in leaves of salinized Carr trees, but had no effect on leaf or root Cl- of trees on Cleo. There were no significant differences in leaf gas exchange parameters of shaded and unshaded salinized plants but the growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na+ than unshaded trees after the first salinity period, and this shade-induced elevated leaf Na+ persisted after the second salinity period in trees on Carr. Thus, shading did not alleviate the negative effects of salinity on growth and Na+ accumulation.

Growth, photosynthesis, nodule nitrogen and carbon fixation in the chickpea cultivars under salt stress

Four cultivars of chickpea, two of them of Mediterranean origin (kabuli), CSG 9651, BG 267 and two Indian (desi) types, CSG 8962, DCP 92-3, differing in their salt sensitivities were identified after screening ten genotypes in saline soils. The cultivars CSG 9651 and CSG 8962 were salt tolerant while BG 267 and DCP 92-3 were salt sensitive, respectively. The seeds of different cultivars were inoculated with Mesorhizobium ciceri, strain F: 75 and the plants were grown in the greenhouse. After the establishment of symbiosis, 15-day-old seedlings were administered doses of saline at varying concentrations (0, 4, 6, 8 dSm-1 NaCl, Na2SO4, CaCl2). Plants were harvested at 40, 70 and 100 days after sowing, for analyses. The main aim was to compare the relative salt tolerance of both desi and kabuli cultivars in terms of nitrogen fixation and carbon metabolism, as well as to ascertain whether the negative effects of saline stress on nitrogen fixation were due to a limitation of photosynthate supply to the nodule or to a limitation on the nodular metabolism that sustains nitrogenase activity. Plant growth, nodulation and nitrogenase activity was more severely affected in BG 267 and DCP 92-3 under salinity treatments (6 and 8 dSm-1) compared with CSG 9651 and CSG 8962. Nodule number as well as nodule mass increased under salt stress in CSG 9651 and CSG 8962 which might be responsible for their higher nitrogen fixation. Salinity reduced leaf chlorophyll and Rubisco activities in all cultivars. However, tolerant cultivars CSG 9651 and CSG 8962 showed smaller declines than the sensitive ones. Phosphoenolpyruvate carboxylase (PEPCase) activity increased significantly in the nodules of tolerant cultivars under salt stress at all harvests, and this was clearly related to salt concentrations. Our results suggest that in salt-affected soils tolerant cultivars have more efficient nodulation and support higher rates of symbiotic nitrogen fixation than the sensitive cultivars.