Adverse Effects Of Salt Stress Research Articles

Physiological Parameters of Silicon-Treated Maize Under Salt Stress Conditions

The effects of silicon (Si) on Zea mays under salt stress conditions were investigated and the data was analyzed by cluster heat maps. The results indicated that the application of Si in salt-stressed plants significantly increased fresh and dry weight, chlorophyll b, carotenoids and reduced sugar, and decreased proline contents. In addition, Si decreased the APX (ascorbate peroxidase) and SOD (superoxide dismutase) activities under salt stress conditions but significantly increased CAT (catalase) activity. The application of Si under salt stress conditions decreased the Na, Ca, Fe, and K contents of plants and increased Mg translocation from the root to shoots. Therefore, alleviation effects of Si under salt stress conditions, at least in parts, may be related to increases of reduced sugar and pigment content, increase of CAT activity as an antioxidant enzyme, and decrease of Na content in maize. Decreases of the SOD and APX activities and the proline content of plants, when Si was added to NaCl-treated plants, showed the favorable role of Si in mitigating the adverse effects of salt stress.

Salicylic Acid Attenuates the Adverse Effects of Salinity on Growth and Yield and Enhances Peroxidase Isozymes Expression more Competently than Proline and Glycine Betaine in Cucumber Plants

Foliar applications of osmoprotectants could be a valuable tool to counteract the deleterious effects of salinity and protect plant cells from oxidative damage. Some of the known osmoprotectants used in this field are salicylic acid, proline, and/or glycine betaine but there is no available empirical research exists to figure out which of these chemicals is the most effective in reducing the adverse effects of salt stress. To compare the ameliorating effects of foliar application of these osmoprotectants on growth, some physiological and biochemical parameters, and productivity of cucumber plants under NaCl stress (0, 50, or 100 mM), a factorial experiment was carried out during 2015 and 2016 seasons at the Experimental Farm of Horticulture Department, Faculty of Agriculture, Ain Shams University, Qalubia Governorate, Egypt. Increasing NaCl levels reduced plant growth parameters, leaf relative water content, leaf membrane stability, chlorophyll contents, some macro-nutrients content and yield and the lowest values were recorded with the use of 100 mM of sodium chloride treatment. Foliar application of salicylic acid at 1 mM, proline at 10 mM, or glycine betaine at 10 mM to cucumber plants ameliorated the harmful effects of NaCl stress on the vegetative growth and yield through enhancing both leaf relative water content and leaf membrane stability. In addition, these treatments improved both chlorophyll contents, and nutrient content, altogether resulted in a significant reduction in sodium (Na+) and chloride (Cl−) accumulation toxicity. Moreover, the expression of cucumber peroxidase isozymes was analyzed in cucumber leaves 1, 3 and 7 days after the second application. Native polyacrylamide gel electrophoresis analysis indicated that exogenous applications led to the differential regulation of peroxidase enzyme. In conclusion, salicylic acid was the most effective in attenuating the negative effects of the salt stress and in up-regulating peroxidase enzyme expression followed by proline and by glycine betaine. Peroxidase enzyme appeared to function as one of the main molecular mechanisms underlying the resistance response of cucumber to salinity.

Increasing the okra salt threshold value with biochar amendments

ABSTRACTSoil salinity is a severe worldwide environmental problem that adversely affects soil properties and the crop growth such as okra. We hypothesized that biochar soil amendments could increase the okra salt threshold, alleviate salt stress and improve soil productivity. In this study, a pot experiment was conducted to investigate whether biochar could ameliorate the effects of salinity on okra plants. Three biochar amendment (BA) soil applications (0%, 5% and 10% by mass of soil) were considered for seven irrigation water salinity levels (0.75, 1.0, 2.0, 4.0, 5.0, 6.0 and 7.0 dS m−1) in a randomized block design with three replications. The Maas and Hoffman salt tolerance model was used to evaluate the effects of BA on okra plant growth parameters (e.g. yield, biomass) and water use efficiency for each salinity treatment. The results showed that increasing the soil salinity levels caused significant decreases in plant yields and yield components. However, biochar application rates of 5% and 10% increased the okra threshold by 19.7% and 81.2%, respectively, compared to the control (0%). The 10% biochar application rate also resulted in the greatest okra plant growth and increased yield, indicating that the effects of salt stress were ameliorated; moreover, the soil bulk density was decreased, and the water content was increased. Hence, biochar soil amendments could be considered as an important agronomic practice that could potentially overcome the adverse effects of salt stress.

Silicon ameliorates the adverse effects of salt stress on sainfoin (Onobrychis viciaefolia) seedlings

The objective of this study was to investigate whether the application of silicon (Si) ameliorates the detrimental effects of salinity stress on sainfoin (Onobrychis viciaefolia). Three-week-old seedlings were exposed to 0 and 100 mmol/L NaCl with or without 1 mmol/L Si for 7 days. The results showed that salinity stress significantly reduced plant growth, shoot chlorophyll content and root K<sup>+</sup> concentration, but increased shoot malondialdehyde (MDA) concentration, relative membrane permeability (RMP) and Na<sup>+</sup> concentrations of shoot and root in sainfoin compared to the control (no added Si and NaCl). However, the addition of Si significantly enhanced growth, chlorophyll content of shoot, K<sup>+</sup> and soluble sugars accumulation in root, while it reduced shoot MDA concentration, RMP and Na<sup>+</sup> accumulation of shoot and root in plants under salt stress. It is clear that silicon ameliorates the adverse effects of salt stress on sainfoin by limiting Na<sup>+</sup> uptake and enhancing selectivity for K<sup>+</sup>, and by adjusting the levels of organic solutes. The present study provides physiological insights into understanding the roles of silicon in salt tolerance in sainfoin.

Endophytic Bacteria Improve Plant Growth, Symbiotic Performance of Chickpea (Cicer arietinum L.) and Induce Suppression of Root Rot Caused by Fusarium solani under Salt Stress.

Salinity causes disturbance in symbiotic performance of plants, and increases susceptibility of plants to soil-borne pathogens. Endophytic bacteria are an essential determinant of cross-tolerance to biotic and abiotic stresses in plants. The aim of this study was to isolate non–rhizobial endophytic bacteria from the root nodules of chickpea (Cicer arietinum L.), and to assess their ability to improve plant growth and symbiotic performance, and to control root rot in chickpea under saline soil conditions. A total of 40 bacterial isolates from internal root tissues of chickpea grown in salinated soil were isolated. Four bacterial isolates, namely Bacillus cereus NUU1, Achromobacter xylosoxidans NUU2, Bacillus thuringiensis NUU3, and Bacillus subtilis NUU4 colonizing root tissue demonstrated plant beneficial traits and/or antagonistic activity against F. solani and thus were characterized in more detail. The strain B. subtilis NUU4 proved significant plant growth promotion capabilities, improved symbiotic performance of host plant with rhizobia, and promoted yield under saline soil as compared to untreated control plants under field conditions. A combined inoculation of chickpea with M. ciceri IC53 and B. subtilis NUU4 decreased H2O2 concentrations and increased proline contents compared to the un-inoculated plants indicating an alleviation of adverse effects of salt stress. Furthermore, the bacterial isolate was capable to reduce the infection rate of root rot in chickpea caused by F. solani. This is the first report of F. solani causing root rot of chickpea in a salinated soil of Uzbekistan. Our findings demonstrated that the endophytic B. subtilis strain NUU4 provides high potentials as a stimulator for plant growth and as biological control agent of chickpea root rot under saline soil conditions. These multiple relationships could provide promising practical approaches to increase the productivity of legumes under salt stress.

Seed priming by sodium nitroprusside improves salt tolerance in wheat (Triticum aestivum L.) by enhancing physiological and biochemical parameters

The germination, seedling vigor, crop establishment and yield of agronomically important crops is negatively affected by soil salinity. The current study aimed to investigate the ability of exogenous fertigation by sodium nitroprusside (SNP) to induce salt tolerance in four high yielding wheat cultivars (Sahar-06, Punjab-11, Millat-11 and Galaxy-13) that differ in their response to salt stress in terms of biomass production, oxidative defense mechanisms and grain yield. Three levels of SNP (0, 0.1 and 0.2 mM) were used for seed soaking. During soaking the seeds were kept in the dark. After soaking for 12 h the seeds were air-dried for 5 h before sowing. Salinity caused a significant reduction in biomass and grain yield, while it increased proline (Pro), ascorbic acid (AsA), hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. Cultivar Sahar-06 and Galaxy-13 were found more tolerant to salinity based on shoot length root fresh and dry wights, 100 grain weight, decreased MDA and H2O2 accumulation, phenolic and ascorbic acid (AsA) contents, accumulation of proline, activities of SOD, POD and CAT as compared to the other cultivars. Seed priming with SNP was effective in reducing the adverse effects of salt stress induced oxidative stress on plant biomass and grain yield in all the studied wheat cultivars, but maximum amelioration of salt stress tolerance by SNP treatment was found in cv. Sahar-06. The increased salt tolerance in wheat plants by SNP seed priming might be due to the role of NO in improving seed vigor and germination and early establishment of seedlings with better growth. 0.1 mM SNP was found the most effective in improving salt tolerance, as compared to other SNP concentations. Exogenous SNP fertigation increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and the contents of AsA, Pro and total phenolics content (TPC) in the salt stressed wheat plants. Our data indicate that SNP-priming induced salt tolerance by up-regulating the antioxidative defense mechanisms resulting in better biomass production and grain yield.

Saponin seed priming improves salt tolerance in quinoa

AbstractQuinoa (Chenopodium quinoa Willd.) is a facultative halophyte of great value, and World Health Organization has selected this crop, which may assure future food and nutritional security under changing climate scenarios. However, germination is the main critical stage of quinoa plant phenology affected by salinity. Therefore, two experiments were conducted to improve its performance under salinity by use of saponin seed priming. Seeds of cv. Titicaca were primed in seven different solutions with varying saponin concentrations (i.e. 0%, 0.5%, 2%, 5%, 10%, 15%, 25% and 35%), and then, performances of primed seeds were evaluated based on mean germination time and final germination percentage in germination assays (0 and 400 mM NaCl stress). Saponin solutions of 10%, 15% and 25% concentration were found most effective priming tools for alleviating adverse effects of salt stress during seed germination. Performances of these primed seeds were further evaluated in pot study. At six‐leaf stage, plants were irrigated with saline water having either 0 or 400 mM NaCl. The results indicated that saline irrigation significantly decreased the growth, physiology and yield of quinoa, whereas saponin priming found operative in mitigating the negative effects of salt stress. Improved growth, physiology and yield performance were linked with low ABA concentration, better plant water (osmotic and water potential) and gas relations (leaf photosynthetic rate, stomatal conductance), low Na+ and high K+ contents in leaves. Our results suggest that saponin priming could be used as an easy‐operated and cost‐effective technology for sustaining quinoa crop growth on salt‐affected soils.

Salicylic Acid Alleviates the Adverse Effects of Salt Stress on Dianthus superbus (Caryophyllaceae) by Activating Photosynthesis, Protecting Morphological Structure, and Enhancing the Antioxidant System.

Salt stress critically affects the physiological processes and morphological structure of plants, resulting in reduced plant growth. Salicylic acid (SA) is an important signal molecule that mitigates the adverse effects of salt stress on plants. Large pink Dianthus superbus L. (Caryophyllaceae) usually exhibit salt-tolerant traits under natural conditions. To further clarify the salt-tolerance level of D. superbus and the regulating mechanism of exogenous SA on the growth of D. superbus under different salt stresses, we conducted a pot experiment to examine the biomass, photosynthetic parameters, stomatal structure, chloroplast ultrastructure, reactive oxygen species (ROS) concentrations, and antioxidant activities of D. superbus young shoots under 0.3, 0.6, and 0.9% NaCl conditions, with and without 0.5 mM SA. D. superbus exhibited reduced growth rate, decreased net photosynthetic rate (Pn), increased relative electric conductivity (REC) and malondialdehyde (MDA) contents, and poorly developed stomata and chloroplasts under 0.6 and 0.9% salt stress. However, exogenously SA effectively improved the growth, photosynthesis, antioxidant enzyme activity, and stoma and chloroplast development of D. superbus. However, when the plants were grown under severe salt stress (0.9% NaCl condition), there was no significant difference in the plant growth and physiological responses between SA-treated and non-SA-treated plants. Therefore, our research suggests that exogenous SA can effectively counteract the adverse effect of moderate salt stress on D. superbus growth and development.

Physiological Mechanism of Salicylic Acid for Alleviation of Salt Stress in Rice

Soil salinity is one of the most important problems of crop production in estuarine and coastal zones. Improvement in salt tolerance of major food crops is an important way for the economic utilization of coastal zones. This study proved that the application of salicylic acid (SA) improved the growth and yield under salt stress conditions and investigated its physiological mechanisms for salt tolerance. The investigation on the effect of SA for salt tolerance during germination showed that the decreased rates of germination and growth (in terms of shoot and root lengths) by the salt stress were significantly increased by the SA application (SA + NaCl). The treatment of SA to the high and low saline soils enhanced the growth, yield and nutrient values of rice. The effects of SA on Na+, K+ and Cl– ionic accumulation were traced under salt stress condition by inductively coupled plasma optical emission spectrometry and ion chromatography. It was revealed that the increased accumulation of Na+ and Clˉ ions by the salt stress were reduced by SA application. An increased concentration of endogenous SA level was detected from the SA-treated rice varieties (ASD16 and BR26) by liquid chromatography electrospray Ionization-tandem mass spectrometry. The activities of antioxidant enzymes such as superoxide dismutase, catalase and peroxidase were increased by salt stress whereas decreased by the SA application. The study proved that the application of SA could alleviate the adverse effects of salt stress by the regulation of physiological mechanism in rice plants. In spite of salt stress, it can be applied to the coastal and estuarine regions to increase the rice production.

Foliar spray of triacontanol improves growth by alleviating oxidative damage in coriander under salinity

Effect of exogenous foliar spray of triacontanol (TRIA) on coriander (Coriamdrum sativum L.) under salt stress revealed that salinity stress caused a few morphological and physiological changes including decrease in root and shoot dry weight. Hydrogen peroxide content and levels of lipid peroxidation in terms of malondialdehyde content increased in leaves under salt stress. Salt stress also induced antioxidant enzymes activities such as superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase. Foliar spray of 10 µM TRIA was more effective in reducing the adverse effects of salt stress on coriander through modulating activities of antioxidant enzymes.

Smoke Priming Regulates Growth and the Expression of Myeloblastosis and Zinc-Finger Genes in Rice under Salt Stress

Salinity negatively affects the rice growth and productivity around the globe including Pakistan. The current study describes about the application of new approach of smoke solution priming, which was used to overcome the deteriorating effect of salinity by investigating its affects on biochemical and molecular attributes of rice crop. Seeds of two rice varieties (Basmati-385 and Shaheen Basmati) were soaked in smoke solution for 24 h. Smoke-soaked seeds were used to evaluate its effect on plant fresh and dry biomass, elemental uptake and expression of myeloblastosis (MYB) and zinc-finger (ZAT12) genes against different levels of NaCl (0, 50, 100 and 150 mM). Fresh and dry biomass of plant was decreased with increasing level of salt stress, while plant raised from smoke-primed seeds had lowers the adverse effect of salt stress. Concentration of sodium ion and \(\hbox {Na}^{+}/\hbox {K}^{+ }\)ratio was increased, while potassium ion concentration was decreased with increasing salt concentration in the medium. The amount of sodium ion was noted higher in roots than shoots, while potassium was in low amount in roots than shoot. Smoke solution reduced the harmful effect of salt stress by reducing the uptake of sodium ion and increasing potassium ions both in roots and in shoots. The expression of MYB and ZAT12 genes was checked by using RT-PCR approach. Result shows that MYB and ZAT12 protein genes were expressed differently under various levels of salt stress, while priming with the smoke solution changed the expression profile of MYB and ZAT12 protein genes by alleviating the drastic effect. It was concluded that priming with smoke solution protects the plants from ionic toxicity, shows promising effect on rice growth and can be used for enhancing crop productivity under saline condition.

Zinc application mitigates the adverse effects of NaCl stress on mustard [Brassica juncea (L.) Czern & Coss] through modulating compatible organic solutes, antioxidant enzymes, and flavonoid content

ABSTRACTThis study examined the protective effect of Zn on salt-stressed Brassica juncea plants using some key morphological and biochemical attributes at different developmental stages (30, 60, and 90 days after treatment [DAT]). Salt stress (200 mM) caused suppression in plant height, root length, and dry weight by 58.35%, 41.15%, and 53.33%, respectively, at 90 DAT, but Zn application improved these variables by 15.52%, 16.59%, and 11.45%, respectively. Furthermore, 200 mM NaCl decreased total chlorophyll by 45.32% and relative water content by 27.62% at 90 DAT, whereas Zn application compensated the decrease in the levels of both variables. NaCl (200 mM) increased H2O2, malondialdehyde, and electrolyte leakage by 70.48%, 35.25%, and 68.39%, respectively, at 90 DAT, but Zn supplementation appreciably reduced these variables. Except for catalase, enzymatic antioxidant activity increased under NaCl stress. Zn application with salt further increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione-S-transferase by 33.51%, 9.21%, 10.98%, 17.46%, and 12.87%, respectively, at 90 DAT. At 90 DAT, salt stress increased flavonoids by 24.88%, and Zn supply by a further 7.68%. Overall, Zn mitigated the adverse effects of salt stress through osmotic adjustment, as well as by modulating the oxidative defense system and flavonoid contents.

Foliar-applied trehalose modulates growth, mineral nutrition, photosynthetic ability, and oxidative defense system of rice (Oryza sativa L.) under saline stress

ABSTRACTA tub experiment was conducted to assess the effect of exogenously applied trehalose (0, 10, and 20 mM) on various attributes of two rice cultivars (Bas-385 and Bas-2000) under salt stress (0, 50, 100, and 150 mM). Salinity decreased growth, gas exchange characteristics, shoot and root potassium (K+) ions, hydrogen peroxide (H2O2), total soluble proteins, activity of catalase (CAT), and yield attributes, while it increased chlorophyll contents, shoot and root sodium (Na+) and calcium (Ca2+), malondialdehyde (MDA), glycinebetain (GB), free proline, and peroxidase (POD) activity. Foliar-applied trehalose improved growth attributes, net photosynthetic rate, GB, total soluble proteins, superoxide dismutase (SOD) and yield. Yield was not obtained at 150 mM salt stress. The rice cultivar Bas-2000 showed better performance with respect to gas exchange attributes and activities of enzymatic antioxidants. Overall, varying levels of foliar-applied trehalose proved to be effective in ameliorating adverse effects of salt stress on rice.

Potassium silicate alleviates deleterious effects of salinity on two strawberry cultivars grown under soilless pot culture

We aimed to understand the impact of two potassium silicate (K2O3Si) levels (1000 and 1500ppm) on vegetative growth, physiological parameters and fruit yield of two strawberry cultivars under saline (50mM NaCl) and non-saline conditions during 2014 and 2015. Supplementary Si counteracted the negative effects of salinity on dry matter, leaf area, and root length and volume. Leaf relative water content and chlorophylls content were also improved by application of K2O3Si under salinity. NaCl imposed oxidative damages to cell manifested as decreased membrane stability index (MSI) as well as increased malondialdehyde (MDA) and H2O2 content. Higher MSI as well as lower MDA and H2O2 in Si-supplied plants representing a systemic palliative effect of Si to salinity induced cellular injuries. Salinity led to an increase of proline and soluble carbohydrates suggesting a physiological osmotic strategy to increase salt tolerance. Reduction of proline content further supports the beneficial roles of Si in alleviation of the adverse effects of salt stress. Significant increase in activity of peroxidase (POD) and superoxide dismutase (SOD) enzymes was only observed during 2015 under saline conditions. The induction of antioxidant enzymes coincided with a decrease in concentration of MDA and H2O2. Salinity decreased fruit yield in both cultivars with a drastic reduction in Paros. K2O3Si nutrition could recover yield loss with almost a 50% increase in fruit weight per plant. Overall, our results suggest that drenching potassium silicate in the nutrient solution of strawberry plants could be considered as a routine strategy to maintain strawberry growth and yield under salinity.

Phosphate dissolving fungi: Mechanism and application in alleviation of salt stress in wheat

The present investigation reveals the solubilization efficiency of tri-calcium phosphate (TCP), Udaipur rock phosphate (URP), aluminium phosphate (AP) and ferric phosphate (FP) by Aspergillus niger (ITCC 6719) and Trichoderma harzianum (ITCC 6721) as function of carbon concentrations. Increasing glucose concentration from 1 to 7% in the growth medium, though improved the phosphorus (P) solubilization significantly but each fungal strain preferred different optimum carbon concentrations for mediating solubilization of different P sources. The two fungi employed different mechanisms to reduce medium pH for release of P from TCP, AP and FP. However, URP was solubilized solely through fungal production of citric, succinic, propionic, malic and acetic acid. A linear increase in citric acid production with increasing carbon concentration was recorded during FP solubilization by T. harzianum. The cell free culture filtrate of A. niger detected high phytase and low acid phosphatase activity titre whereas results were vice versa for T. harzianum. Both the fungal strains possessed plant growth promoting attributes such as auxin and sidreophore production and could solubilize Zn. In hydroponic system (with 60mM of sodium chloride concentration), supplementation with culture filtrate from each fungal strain increased the shoot growth of wheat seedlings significantly compared to non culture filtrate control. Use of A.niger as bio-inoculant could be a sustainable approach to improve soil P availability, promote plant growth and alleviate adverse effect of salt stress.

Calcium application mitigates salt stress in Date Palm (Phoenix dactylifera L.( offshoots cultivars of Berhi and Sayer

The effectiveness of exogenous application of calcium in ameliorating the adverse effects of salt stress (15.9 dS m-1) on date palm offshoots (Phoenix dactylifera L. cultivars of Berhi and Sayer) was investigated. Ca-fertilisers Polixal and Rexene were applied either as soil amendments or foliar spray. The results showed that Polixal at 30 ml offshoot-1 significantly increased plant height, leaf area, total chlorophyll content, RWC, proline concentration, peroxidase activity, IAA content, K+ and K+/Na+ ratio in leaves of Berhi cultivar, whereas catalase activity, ABA and Cl- content were decreased. Also Berhi cultivar responded to soil amendments more than to foliar spray. However, Ca-fertilisers mitigated salt stress in the two cultivars and Berhi cultivar was more salt stress tolerant than Sayer cultivar by maintaining the high ratio of K+/Na+ and regulating levels of IAA to ABA, in silty clay loam soil. These results suggest that calcium application can improve the defense system under salt stress conditions.

Methyl jasmonate regulated diploid and tetraploid black locust (Robinia pseudoacacia L.) tolerance to salt stress

Methyl jasmonate (MeJA) is an essential and promising plant growth regulation factor that can improve plant development and growth. Here, we explored the mechanism by which MeJA regulates the tolerance of black locust (Robinia pseudoacacia L.) to salt stress. In this study, diploid and tetraploid R. pseudoacacia were subjected to three treatments: 500 mM NaCl; 100 μM MeJA; and 500 mM NaCl and 100 μM MeJA, and the changes in plant growth, endogenous MeJA levels and the anti-oxidative metabolism of leaves were investigated. The results showed that salt stress significantly inhibited plant growth and induced the accumulation of Na+ and Cl− ions, malondialdehyde (MDA) content and reactive oxygen species. However, these adverse effects could be alleviated by applying MeJA, which was followed by a marked increase in the activities of antioxidant enzymes. In addition, some genes encoding several antioxidant enzymes were also up-regulated. Simultaneously, the endogenous MeJA content in MeJA-treated plants was lower than in salt-treated plants. It is noteworthy that tetraploids always possessed higher salt tolerance and obtained greater positive effects from MeJA than diploids. These results suggested that MeJA might play a protective role in defense responses, enabling diploid and tetraploid black locust, especially tetraploid, to better tolerate the adverse effects of salt stress.

Silicon nutrition alleviates the lipid peroxidation and ion imbalance of Glycyrrhiza uralensis seedlings under salt stress

Soil salinity reduces growth of Glycyrrhiza uralensis in arid and semi-arid areas of north-west in China. Silicon (Si) nutrition may alleviate salt stress in many crops including grain crop, fruit crop, and vegetable crop. In this study, the alleviating effects of Si on growth characteristics, antioxidant enzyme activity (SOD and POD) and MDA concentration, and K+ and Na+ concentrations in G. uralensis seedlings subjected to 50 mM NaCl stress were investigated. The results showed that NaCl stress imposed significant reduction in root length, secondary root number, leaf number, and stem and total dry weight of G. uralensis. NaCl stress also significantly reduced the activities of SOD and POD, and ration of K+/Na+, but significantly increased MDA concentration in leaves of G. uralensis seedling. The addition of Si increased SOD and POD activities, and reduced MDA concentration, which resulting in greater reactive oxygen species detoxification and lower lipid peroxidation. Si also significantly increased the ratio of K+/Na+ in stem and leaves of G. uralensis. In conclusion, Si could alleviate adverse effects of salt stress probably by decreasing Na+ concentration and improving antioxidant enzyme activity of G. uralensis, and these alleviating effects were dependent on Si concentration and on Si processing time.

Responses of pelargonium (Pelargonium × hortorum L.H. Bailey) to long-term salinity stress induced by treatment with different NaCl doses

The aim of this research was to study the physiological and biochemical responses of pelargonium growing in saline substrate. Salt stress caused an increase of sodium and chlorine, and decrease potassium ions concentrations in pelargonium leaves depending on their level in peat substrate. About 4–16-fold increase of sodium, 4–6-fold increase of chlorine were found in leaves of plants growing in substrate treated with the lowest (452 mg dm−3) and highest (2992 mg dm−3) NaCl doses, respectively. The concentration of potassium ions decreased by 20 to 27 % in leaves of plants growing in substrate supplemented with NaCl doses from 1976 to 2992 mg dm−3, respectively. However, lower doses of sodium chloride did not affect the content of potassium ions in pelargonium leaves. The increasing salinity of substrate after the addition of 960–2992 mg NaCl dm−3 caused the reduction of plant fresh matter in the range of 25–65 %, plant height 10–37 %, and leaf area 15–55 %. There were no changes in relative water content (RWC) and no signs of damage in the form of necrotic spots for any of the used salt concentrations. The content of chlorophyll pigments decreased proportionally to salt concentration, but the content of carotenoids did not change. Maximum photochemical activity of PSII (F v/F m) was reduced only in plants growing at the highest dose of NaCl. Proline and anthocyanin levels increased in response to elevated NaCl concentration. At the highest dose of NaCl proline level increased by 30 % while the content of anthocyanins increased about 2.5-fold in relation to the control. It can be assumed that proline and anthocyanins accumulated in pelargonium leaves may be responsible for the amelioration of the adverse effects of salt stress. The results revealed that the investigated pelargonium ‘Survivor Dark Red’ is somewhat tolerant to salinity and it can be cultivated in substrate and soil polluted with NaCl at the level lower than 1976 mg dm−3.

Thiourea-induced metabolic changes in two mung bean [Vigna radiata (L.) Wilczek] (Fabaceae) varieties under salt stress

A pot experiment was conducted to assess the effect of foliar application of thiourea on two mung bean (Vigna radiata (L.) Wilczek) varieties (NM-2006 and NM-2011) under salt stress. Experiment was laid-out in a completely randomized design with four replicates. Two salt treatments [non-saline (control) and 75 mM NaCl] were applied to 28-day-old mung bean plants. Three levels of TU [0 (water spray), 10, and 20 mM] were foliarly sprayed after 1 week of salt treatment. Data for various growth and physio-chemical attributes were collected of 64-day-old mung bean plants, while two plants were left for obtaining yield. Salt stress significantly decreased all growth and yield attributes, while increased anthocyanin, relative membrane permeability (% RMP), malondialdehyde, total soluble sugars, total soluble proteins, activities of catalase and peroxidase enzymes, total phenolics, free proline, and glycinebetaine contents. Foliar application of varying TU levels significantly increased shoot and root fresh and dry weights, shoot and root lengths, seed yield per plant, pod fresh and dry weights, number of seeds per plant, 100-seed weight, chlorophyll b (in NM-2006), total soluble sugars, total soluble proteins, POD activity, and total phenolic contents, while decreased RMP (%), total free amino acids, and GB contents. Of the two mung bean varieties, NM-2006 was superior to NM-2011 in most of growth and physio-chemical attributes under both salt stress and non-stress conditions as well as foliarly applied varying levels of TU. Overall, 20 mM TU proved more effective in reducing adverse effects of salt stress in both mung bean varieties.