Effects of combined NaCl and CaCl2 salinity on photosynthetic parameters of barley grown in nutrient solution

The changes caused by NaCl− and CaCl₂-induced salinity on several leaf parameters have been measured in two cultivars of barley ( Hordeum vulgare L.) growing in a growth chamber in nutrient solution. Salinity was induced by adding to the nutrient solution equal weights of NaCl and CaCl₂, to obtain conductivities of 2, 6, 12, 19 and 26 dS m⁻¹. Salinity induced decreases in the leaf water potential and in the osmotic potential. Salinity did not induce significant changes in the relative photosynthetic pigment composition of barley leaves, the photosynthetic pigment stoichiometry for neoxanthin:violaxanthin cycle pigments:lutein:β-carotene:Chl b :Chl a being close to 3:6:14:12:25:100 (mol:mol). Salinity per se did not induce interconversions in the carotenoids within the violaxanthin cycle in most barley leaves. The PSII photochemistry of most barley leaves was unchanged by salinity. However, some apparently healthy leaves growing in high salinity exhibited sudden decreases in PSII photochemistry and increases in zeaxanthin (at the expense of violaxanthin), that preceded rapid leaf drying. Salinity induced significant changes in the slow part of the chlorophyll fluorescence induction curve from barley leaves.     

Expression Analysis of Genes Encoding NHX2 Antiporter and Subunit A of Vacuolar H+-ATPase Pump in Salt-Resistant and Salt-Sensitive Barley (Hordeum vulgare L.) Cultivars under Salt Stress

Russian Journal of Plant Physiology - Salinity is one of the most important factors causing limiting growth aspects. Salinity tolerance is a multigenic trait activating mechanisms such as high H+...     

Factors influencing species diversity in saline waters of Death Valley,USA

Salinity is a major factor influencing the distributions and abundances of aquatic macroinvertebrates of saline waters in Death Valley, California, USA. A general pattern of declining numbers of species with increasing salinity is seen in Death Valley waters. Some species are restricted to low salinities, others are found only in highly saline pools, and still others are widely distributed over a broad range of salinities.Salinity alone cannot explain distributions seen in the field. Distributions and abundances of species such as the caddisfly Limnephilus assimilis Banks are broader than would be predicted on the basis of laboratory studies of salinity and temperature. I present evidence that for such species, biotic factors such as reduced predation at high salinities may compensate for increased physiological stress.     

Biochemical and molecular changes induced by salinity stress in <Emphasis Type="Italic">Oryza sativa</Emphasis> L.

Salinity stress constrains the growth, development, and yield in crops. Rice is an important cereal crop highly affected by salinity. To ensure the agriculture production in salt-affected soils, it is enormously entail to understand the salt adaptation strategies of plants. Salinity directly affects the morphology, physiology, and metabolism of the plants. The current study was carried out to check the influence of different concentrations of sodium chloride on rice cultivar. Higher concentration of the NaCl showed significant reduction in the growth, pigment system, and metabolites in rice cultivars. Salinity also elicited the antioxidant enzymes (CAT, SOD, and POX) response and gene expression. Cell biological studies showed the H₂O₂ production and nuclear fragmentation due to alleviated salinity stress. To delineate the portrayal of antioxidant proteins and autophagy mechanism in salinity stress, the homologs of rice CAT1, Mn-SOD, GPX, ATG1, and ATG6 genes were retrieved from blast search. The real-time PCR analysis showed differential expression of genes and depicts new molecular insight of target genes to understand the salinity stress and autophagy-mediated stress signaling pathways.     

Differential Responses of Nitrogen-Fixing Cyanobacteria to Salinity and Osmotic Stresses

Two nitrogen-fixing Anabaena strains were found to be differentially tolerant to salinity and osmotic stresses. Anabaena torulosa, a brackish-water, salt-tolerant strain, was relatively osmosensitive. Anabaena sp. strain L-31, a freshwater, salt-sensitive strain, on the other hand, displayed significant osmotolerance. Salinity and osmotic stresses affected nitrogenase activity differently. Nitrogen fixation in both of the strains was severely inhibited by the ionic, but not by the osmotic, component of salinity stress. Such differential sensitivity of diazotrophy to salinity-osmotic stresses was observed irrespective of the inherent tolerance of the two strains to salt-osmotic stress. Exogenously added ammonium conferred significant protection against salinity stress but was ineffective against osmotic stress. Salinity and osmotic stresses also affected stress-induced gene expression differently. Synthesis of several proteins was repressed by salinity stress but not by equivalent or higher osmotic stress. Salinity and osmotic stresses induced many common proteins. In addition, unique salt stress- or osmotic stress-specific proteins were also induced in both strains, indicating differential regulation of protein synthesis by the two stresses. These data show that cyanobacterial sensitivity and responses to salinity and osmotic stresses are distinct, independent phenomena.     

Effects of sodium, potassium and calcium on salt-stressed barley

We grew barley ( Hordeum vulgare L. CM 72) for a 28-day period and sequentially harvested plants every 3 or 4 days. Plants were salt-stressed with either NaCl or KCl (125 m M ) with or without supplemental Ca (10 or 0.4 m M final concentration, respectively). We determined tissue concentrations of Na, Ca, Mg, K. S, P, Fe, Mn, Cu and Zn for each harvest date by inductively coupled plasma spectrometry. Uptake (specific absorption rate) was calculated from the element content and growth rates. Salinity had significant effects on the uptake and concentrations of most elements. Mg and Mn concentrations declined with time. The concentrations of all other elements determined increased over time. Element uptake on a root dry weight basis declined with time. Three variables were significantly affected by salinity and correlated with growth; 1) the Ca concentration, 2) the total sum of the cation concentration (TC), and 3) the Mn concentration of the shoot. Salinity reduced Ca uptake and concentrations. Supplemental Ca increased Ca concentrations and was positively correlated with growth during salt stress. Salinity doubled TC, which was negatively correlated with relative growth rate (RGR). Relative growth rate declined at TC values above 150 m M . Salinity reduced the uptake and concentration of Mn. Manganese concentrations in the shoot were highly correlated with RGR. Relative growth rate declined at Mn concentrations below 50 nmol (g fresh weight)⁻¹.     

Effect of Salinity on the Activities of RNase, DNase and Protease during Germination and Early Seedling Growth of Mung Bean

Seeds and seedlings of mung bean (Phaseolus aureus Roxb.) were treated separately with NaCl, KCl, Na₂SO₄ and K₂SO₄ solutions of 5 and 10 S/cm conducitivity. The activity of RNase, DNase and protease were estimated in cotyledons, embryo axis, leaves, and roots. Salinity caused inhibition of RNase activity in the cotyledons and roots, but increase in embryo axis and leaves. Activity of DNase was also increased; sodium salt was more effective than potassium irrespective of associated anion. Salinity in general either reduced or had no effect on protease activity in all organs, with the exception of NaCl which doubled it in leaves.     

Long-term variability of winter nitrate concentrations in the Northern Wadden Sea driven by freshwater discharge,decreasing riverine loads and denitrification

The hypothesis of a recent reversal in the eutrophication of the Wadden Sea and the potential of inshore waters in denitrification is explored. Salinity, temperature and nitrate concentrations in the List Tidal Basin (Northern Wadden Sea) have been measured about twice weekly since 1984. Salinity has a clear seasonal cycle with lowest salinities of about 27 in late winter and highest salinities of about 31 in summer. Mean annual deviations from the long-term mean salinity correlate significantly with riverine freshwater discharge. Winter nitrate concentrations are generally high (about 50 μM on average). The major part of the variability is related to salinity (∼35%). Temperature had a minor impact (∼1%). Superimposed on this, a long-term decrease of about 1 μM per year was found. Together, these processes account for about 45% of the nitrate variability. The long-term decrease of about 2% per year is similar to continental riverine trend in total nitrogen loads. In contrast to the List Tidal Basin, salinity explained more than 90% of nitrate variability in the off-shore German Bight. Salinity (30) normalised winter nitrate data of the German Bight also show a long-term decreasing trend. Most of the List Tidal Basin data are either on or below the nitrate–salinity relation found in the German Bight. This observation suggests that denitrification has a major impact on the winter nitrate concentrations in the Northern Wadden Sea compared to the German Bight. It is hypothesised that a large part of the unexplained variability is related to weather-dependent changes in residence time of tidal water masses in the Wadden Sea and circulation patterns within the German Bight.     

Resistance patterns to salinity and temperature in an estuarine mysid (Mysidopsis bahia) in relation to its life cycle

Survival of the estuarine mysid Mysidopsis bahia was monitored in the laboratory from juvenile through maturation to an adult under various combinations of salinity (3–31 %₀ S) and temperature (19–31°C). Salinity had a greater influence on mysid survival than did temperature. Salinity tolerance was strongly modified by temperature with maximum tolerance at intermediate temperatures. Salinity-temperature interactions on mysid survival varied with age of the mysid. Canonical analysis of weekly resistance patterns produced absolute maximum survival combinations for salinity and temperature which changed over time. The salinity-temperature tolerance ranges described for this estuarine mysid correspond with previously described physiological capabilities and distribution patterns.     

Proteome analysis of soybean leaves,hypocotyls and roots under salt stress

Background  

Salinity is one of the most widespread agricultural problems in arid and semi-arid regions that makes fields unproductive, and soil salinization is a serious problem in the entire world. To determine the effects of salt stress on soybean seedlings, a proteomic technique was used.     

Experimentelle Untersuchungen zur Salzadaptation verschiedener Rassen des Dreistachligen Stichlings (Gasterosteus aculeatus L.)

Experimental Studies on Adaptation to Salinity Shown by the Different Races of the Three-Spined Stickleback (Gasterosteus aculeatus L.)     

Changes in plasma membrane lipids, aquaporins and proton pump of broccoli roots, as an adaptation mechanism to salinity

Salinity stress is known to modify the plasma membrane lipid and protein composition of plant cells. In this work, we determined the effects of salt stress on the lipid composition of broccoli root plasma membrane vesicles and investigated how these changes could affect water transport via aquaporins. Brassica oleracea L. var. Italica plants treated with different levels of NaCl (0, 40 or 80 mM) showed significant differences in sterol and fatty acid levels. Salinity increased linoleic (18:2) and linolenic (18:3) acids and stigmasterol, but decreased palmitoleic (16:1) and oleic (18:1) acids and sitosterol. Also, the unsaturation index increased with salinity. Salinity increased the expression of aquaporins of the PIP1 and PIP2 subfamilies and the activity of the plasma membrane H⁺-ATPase. However, there was no effect of NaCl on water permeability (P_f) values of root plasma membrane vesicles, as determined by stopped-flow light scattering. The counteracting changes in lipid composition and aquaporin expression observed in NaCl-treated plants could allow to maintain the membrane permeability to water and a higher H⁺-ATPase activity, thereby helping to reduce partially the Na⁺ concentration in the cytoplasm of the cell while maintaining water uptake via cell-to-cell pathways. We propose that the modification of lipid composition could affect membrane stability and the abundance or activity of plasma membrane proteins such as aquaporins or H⁺-ATPase. This would provide a mechanism for controlling water permeability and for acclimation to salinity stress.     

Response of Bur and Red oak seedlings to NaCl-induced salinity

Growth performance of Bur oak (Q. macrocarpa Michx.) and Red oak (Q. rubra L.) under salinity conditions was assessed by growing seedlings in the presence of increasing levels of NaCl. Salinity reduced root growth in both species, although its repressive effect was more pronounced in Red oak. Exposure to 75 mM NaCl for 3 weeks almost arrested root growth in Red oak, while it reduced it only by 40 % in Bur oak. Red oak roots showed extensive necrosis and limited branching. Salinity also induced leaf injury, which at a NaCl level of 25 mM was less severe in Bur oak possibly due the higher activity of catalase, superoxide dismutase, and dehydroascorbate reductase enzymes participating in the detoxification of reactive oxygen species. Relative to Red oak, a higher retention of photosynthetic rate was observed in Bur oak grown under saline conditions. Salinity also altered nutrient uptake and accumulation in root and leaf tissue. Compared to Red oak, the content of magnesium and calcium in Bur oak leaves exposed to NaCl remained elevated, while an opposite trend was observed in root tissue. This was in contrast to nitrogen which was not altered by salinity in Bur oak, while it increased in roots of Red oak. The better performance of Bur oak root tissue under salinity conditions was ascribed to structural modifications of the root system with maturation of casparian bands and suberinization occurring closer to the root tip. These structures are known to act as barriers enhancing ion selectivity. Collectively this study demonstrates that relative to Red oak, Bur oak is more tolerant to NaCl-induced salinity conditions.     

Hardening of root cell walls: a growth inhibitory response to salinity stress

Primary roots of intact maize plants (Zea mays L.) grown for several days in nutrient solutions containing 100 mol m⁻³ NaCl and additional calcium, had relatively inhibited rates of elongation. Possible physical restraints underlying this salt induced inhibition were investigated. The inhibition did not involve reductions in osmotic potential gradients and turgor in the tip tissues responsible for root elongation growth. The apparent yield threshold pressure, which is related to capacity of cell walls to undergo loosening by stress relaxation, was estimated psychrometrically in excised root tips. Salinity increased yield threshold values. Comparative root extensibility values were obtained for intact plants by determining the initial (1 min) increase in root elongation rate induced by an 0.1 MPa osmotic jump. Comparative extensibility was significantly reduced in the salinized root tips. Salinity did not reduce capacities for water efflux and associated elastic contraction in root tip tissues of intact plants exposed to hypertonic mannitol. We conclude that cell wall hardening in the elongating root tips is an important component of root growth inhibition induced by long-term salinization.     

Effect of Salinity on Germination and Seedling Growth of twoAtriplexspecies (Chenopodiaceae)

Salinity is one of the environmental factors that has a criticalinfluence on the germination of halophyte seeds and plant establishment.Salinity affects imbibition, germination and root elongation.However, the way in which NaCl exerts its influence on thesevital processes, whether it is through an osmotic effect ora specific ion toxicity, is still not resolved. Dimorphic seedsof the halophytesAtriplex prostrataandA. patulawere treatedwith various iso-osmotic solutions of NaCl and polyethyleneglycol (PEG). For each treatment, imbibition, germination rate,percent germination, germination recovery and nuclear area ofroot tip cells were compared. Higher concentrations of NaCl(-1.0 MPa) were more inhibitory to imbibition, germination andseedling root elongation than iso-osmotic PEG solutions. Allseeds recovered from a pre-treatment with -2.0 MPa NaCl andPEG solutions, except large seeds ofA. prostratawhich failedto germinate following transfer from -2.0 MPa NaCl. NaCl causeda greater increase in nuclear volume than iso-osmotic PEG solutions.These data suggest that the influence of NaCl is a combinationof an osmotic effect and a specific ion effect.Copyright 1998Annals of Botany Company Atriplex patula,Atriplex prostrata,cytophotometry, osmotic potential, salinity, seed germination.     

Sorghum Seedling Growth as a Function of Sodium Chloride Salinity and Seed Size

Sodium chloride salinity in the range 0–90 mM inhibitedgrowth of sorghum seedlings. Seedlings derived from small seedswere most sensitive to salinity. Salinity, seed size, seedling growth, sorghum, Sorghum bicolor L. Moench     

Effect of soil salinity on the electro-chemical and chemical kinetics of some plant nutrients in submerged soils

Summary The electro-chemical and chemical kinetics of six California rice soils were significantly influenced by the presence of salts up to an EC of 9 mmhos/cm in saturation extract (EC_e). Subsamples of each soil salinity treatment were incubated for periods up to 10 weeks after flooding. Most of the changes in Eh and pH values took place in the first 3–4 weeks after submergence. Salinity decreased pH values, but slightly increased the redox-potential. Both ammonification and nitrate reduction were significantly decreased, by increasing soil salinity. Salinity up to 9 mmhos/cm did not affect levels of Bray and Kurtz extractable P, but increased the water extractable Ca, Mg, K and Mn. In DTPA extract, salinity in incubated soils had no effect on Zn in 4 soils, but it decreased Fe in acid and neutral soils. Possible explanations for the electro-chemical and chemical kinetic changes due to flooding and salinity are discussed.     

Proteomic identification of OsCYP2, a rice cyclophilin that confers salt tolerance in rice (Oryza sativa L.) seedlings when overexpressed

Background  

High Salinity is a major environmental stress influencing growth and development of rice. Comparative proteomic analysis of hybrid rice shoot proteins from Shanyou 10 seedlings, a salt-tolerant hybrid variety, and Liangyoupeijiu seedlings, a salt-sensitive hybrid variety, was performed to identify new components involved in salt-stress signaling.     

Effect of ellagic acid on growth and physiology of canola (Brassica napus L.) under saline conditions

Salinity stress is limiting growth and productivity of plants in many areas of the world. Plants adopted different strategies to minimize the effect of salt stress. A pot experiment was conducted to investigate the morphological and physiological changes produced in Canola (Brassica napus) by exogenous application of ellagic acid (EA) under saline conditions. EA is an antioxidant, expected to reduce the effect of salinity stress. The seeds of two canola cultivars, Rainbow and Oscar, were soaked for 6?h with different concentrations of EA (0, 55 and 110?µg/ml). The soaked seeds were sown in small pots. Salt stress was imposed on the plants by applying NaCl solutions of different concentrations (0, 60 and 120?mM) and the duration of stress was for four weeks. Salinity stress reduced seed germination and disturbed the morphological and physiological attributes of B. napus. Application of EA as seed soaking reduced the effect of salinity and enhanced the growth of plants. Overall, we could confirm a significant role of EA by inducing salinity tolerance in B. napus.     

The effects of humidity and cytokinin on growth and water relations of salt-stressed bean plants

Summary Salinity inhibited growth of plants in both low and high humidities when compared to control plants grown under the same conditions. However, salttreated plants grew better under high humidity when compared to saltstressed plants grown under low humidity. Benzyl adenine (B.A.) sprays did not have any effect on growth of salt-treated plants grown in low humidity. However, when plants were grown in high humidity, B.A. either had no effect or inhibited the growth of the plants. Salinity increased leaf resistance to water vapor loss (R _l ) in both low and high humidity, and B.A. decreased R _l of salt-treated plants in both humidities. The effects of salinity on decreasing root permeability were the same in both humidities studied, and they were not reversed by B.A. applications. The results do not support the idea that growth inhibition due to salinity is simply the result of impaired cytokinin metabolism and/or transport. Rather, the growth inhibition probably is due to the effect of salinity on the balance of hormones and could be acting at several different steps. re]19720725