Is the salt tolerance of maize related to sodium exclusion? I. Preliminary screening of seven cultivars

Maize (Zea mays L.) plants in the early stage of development were treated with 80 mM sodium chloride (NaCl) with or without supplemental calcium (Ca²⁺) (8.75 mM) for a seven day period. The effects of salinity on dry matter production and shoot and root concentrations of sodium (Na⁺), Ca²⁺, and potassium (K⁺) were measured for seven Pioneer maize cultivars. Salinity significantly reduced total dry weight, leaf area, and shoot and root dry weight below control levels. For all seven cultivars, Na⁺concentrations were reduced and leaf area was significantly increased by supplementing salinized nutrient solutions with 8.75 mM calcium chloride (CaCl₂). The two cultivars with the lowest shoot and root Na⁺ concentrations under NaCl‐salinity showed the greatest increases in total, shoot and root dry weights with the addition of supplemental Ca. Shoot fresh weight/dry weight ratios for all cultivars were decreased significantly by both salinity treatments, but supplemental Ca²⁺ increased the ratio relative to salinity treatments without supplemental Ca. Root fresh weight/dry weight ratios were decreased only by salinity treatments with supplemental Ca. With NaCl‐salinity, cultivars which had lower shoot and root Na⁺ concentrations were found to be more salt sensitive and had significantly lower amounts of dry matter production than those cultivars which had higher shoot and root Na⁺ concentrations. It was concluded that Na⁺ exclusion from the shoot was not correlated with and was an unreliable indicator of salt tolerance for maize.     

Growth,Chlorophyll, and Cation Concentration of Tetraploid Wheat on a Solution High in Sodium Chloride Salt: Hulled Versus Free-Threshing Genotypes

Based on the literature, under-utilized hulled wheats could be tolerant to some harsh environmental conditions. The effect of salt stress on chlorophyll content, leaf area, dry weight, and ion concentrations in eight genotypes of tetraploid wheat (Triticum turgidum) using a three-replicate completely random design indoor experiment was studied. These genotypes included six hulled wheat (HW), T. turgidum subspp. Dicoccum, and two free-threshing wheat (FTW), T. turgidum subspp. durum. Salt stress was induced by adding sodium chloride (NaCl) to a hydroponic medium to 40, 80, and 120 mM, in addition to control. Salinity reduced leaf content of chlorophyll a (chl-a) at 120 mM but had not significant effect on chlorophyll b (chl-b) content. Salt stress decreased plant leaf area by nearly 63%. Plant top dry weight declined by 52% with increasing salinity to 120 mM level. Plant top calcium (Ca²⁺) content was not affected, whereas plant top sodium (Na⁺) concentration increased and potassium (K⁺) and magnesium (Mg⁺) concentration decreased with increasing salinity, averaged over genotypes. No significant interaction of genotype × salinity was detected for traits studied in this experiment. When contrasted as two groups of genotypes, i.e., HW vs. FTW, the former group suffered more severe decreases in terms of chl-a, chl-b, leaf area, dry weight, and Mg²⁺ concentration and a more pronounced increase in Na⁺ compared to the FTW. Overall, no evidence of salt tolerance was found for hulled tetraploid wheats of central Iran.     

Sodium‐calcium interactions with growth,water, and photosynthetic parameters in salt‐treated beans

Calcium (Ca²⁺) amelioration of the plant's growth response to salinity depends on genetic factors. In this work, supplemental Ca²⁺ did not improve growth in Phaseolus vulgaris L. cv. Contender under high‐saline conditions and negatively affected several physiological parameters in nonsalinized plants. The response to supplemental Ca²⁺ was examined using plants grown in 25% modified Hoagland solution at different Na⁺ : Ca²⁺ ratios. In control plants (1 mM Ca²⁺; 1 mM Na⁺) surplus Ca²⁺ (4 or 10 mM) was associated with stomatal closure, decrease of hydraulic conductivity, sap flow, leaf specific dry weight, leaf K⁺ and leaf Mg²⁺ concentrations, and inhibition of CO₂ assimilation. Leaf water content was enhanced, while water‐use efficiency and dry matter were unaffected during the 15 d experimental period. The Ca²⁺ effect was not cation‐specific since similar results were found in plants supplied with high external Mg²⁺ or with a combination of Ca²⁺ and Mg²⁺. Relative to control plants, salinization (50 and 100 mM NaCl) caused a decrease in dry matter, hydraulic conductivity, sap flow, leaf Mg²⁺ activity, and inhibition of stomatal opening and CO₂ assimilation. However, NaCl (50 and 100 mM NaCl) enhanced leaf K⁺ concentration and water‐use efficiency. At 100 mM NaCl, leaf water content also significantly increased. Supplemental Ca²⁺ had no amelioration effect on the salt‐stress response of this bean cultivar. In contrast, the 50 mM–NaCl treatment improved stomatal conductance and CO₂‐assimilation rate in plants exposed to the highest Ca²⁺ concentration (10 mM). Phaseolus vulgaris is classified as a very NaCl‐sensitive species. The similarities in the effects caused by supplemental Ca²⁺, supplemental Mg²⁺, and NaCl salinity suggest that P. vulgaris cv. Contender has a high non‐ion‐specific salt sensitivity. On the other hand, the improvement in gas‐exchange parameters in Ca²⁺‐supplemented plants by high NaCl could be the result of specific Na⁺‐triggered responses, such as an increase in the concentration of K⁺ in the leaves.     

Soil salt and NaCl have different effects on seed germination of the halophyte Suaeda salsa

Seed germination is a key life‐history stage of halophytes. Most studies on seed germination of halophytes have focused on the effects of a single salt, while little information is available on the effects of mixed salt in the natural habitat. Due to the contribution of multiple ions in saline soil, we hypothesized that the effect of mixed salt on seed germination will differ from that of a single salt and the mechanism of how germination is affected will differ as well. The effects of mixed salt and NaCl on germination, water imbibition, and ionic concentrations of seeds of Suaeda salsa (L.) Pall. were compared at various salinity levels. Germination percentage (GP) and rate (GR) decreased with increasing salinity level, regardless of salt type. There was no difference in GP or GR between mixed salt and NaCl when the salinity level was below 20 dS m^?1. Above 20 dS m^?1, GP and GR in NaCl were lower than those in mixed salt. At the same salinity level, Na⁺ concentration in seeds was higher in NaCl than that in mixed salt, but the reverse was true for Ca²⁺ and Mg²⁺ concentrations. Imbibition rate for seeds in NaCl was lower than that in mixed salt at the same salinity level. Addition of Ca²⁺ and Mg²⁺ alleviated the inhibition of NaCl on seed germination. In conclusion, our results suggest that the effects of soil salts and NaCl on seed germination are different, and using NaCl instead of soil salt might not be realistic to show the effect of saline stress on seed germination of halophytes in the natural habitat.     

Edaphic characterization and soil ionic composition influencing plant zonation in a semiarid Mediterranean salt marsh

Soil characteristics and plant zonation were studied in a semiarid Mediterranean salt marsh in SE Spain. According to topographic sequences and plants distribution, two transects were established from the border of La Mata lagoon to the upland vegetation limit and soils were described and analysed. Regularly spaced plots were established in these transects in accordance with the stands of vegetation and surface soil samples were taken every 2 months for 2 years. The following edaphic factors were determined: soil moisture content, pH and concentration of Cl⁻, SO₄²⁻, Ca²⁺, Mg²⁺, Na⁺ and K⁺ in the saturation extract. In addition, the groundwater level was measured and the duration of the flooding periods established in each plot. Soil–plant relationships were studied by means of canonical correspondence analysis. Based on rainfall data for the study period, dry and wet seasons were separated and the habitats of the plant communities were compared for salt quantity and quality independently for each season. Soils were classified, according to FAO (1998), as Hypercalcic, Sodic and Mollic Solonchaks and Hypercalcic Sodic Calcisols. The most important variables which explained plant zonation were: the flooding period, total salinity, minimum Ca²⁺/Na⁺ ratio and the mean sodium adsorption ratio. When the habitats of the main plant communities were compared, differences in salt quantity, quality and seasonal variations were found. Two chenopod shrubs, Arthrocnemum macrostachyum and Sarcocornia fruticosa, predominated in the most saline areas. More pronounced seasonal variations in soil salinity were found in the A. macrostachyum zone than in the Sarcocornia fruticosa zone. The highest value for K⁺/Na⁺ and Ca²⁺/Na⁺ ratios were measured in the Suaeda vera stand. The Lygeum spartum zone was distinguished by the high Ca²⁺/Na⁺ and Ca²⁺/Mg²⁺ ratios in the wet period. Among the rushes, Schoenus nigricans predominated in the less saline areas, where the K⁺/Na⁺ ratio was higher and the Ca²⁺/Na⁺ ratio lower than where Juncus maritimus predominated. Limonium cossonianum communities occupied an intermediate position with respect to soil salinity, between the chenopod shrubs and the other communities.Our results suggest that salt marsh plant zonation is influenced by temporal and spatial edaphic gradients which must be jointly considered if soil–plant relationships in saline soils are to be fully understood.     

运东近滨海地区燕麦秸秆盐分积累与改良盐碱地潜力分析

为探明燕麦在运东滨海盐碱地区秸秆盐分积累特点以及改良盐碱地的潜力,选用"坝莜1号"、"白燕2号"和"花早2号"燕麦,采用单因素随机区组试验,以品种和土壤含盐量作为因素,进行了2组田间试验,测得燕麦的生物量、秸秆离子浓度和积累量及秸秆与土壤离子浓度比值。研究结果显示,"坝莜1号"燕麦开花-灌浆至成熟期整株生物量从2.9 t·hm-2增加至3.8 t·hm-2,延迟20 d收获则减少至2.5 t·hm-2。"白燕2号"在低土壤盐分浓度(1.0 g·kg-1左右)下的生物量(3.1 t·hm-2)显著大于中浓度(2.0 g·kg-1左右,1.7 t·hm-2)和高浓度(3.0 g·kg-1左右,0.4 t·hm-2)下的生物量。中等土壤盐分浓度下"坝莜1号"的生物量(3.8 t·hm-2)显著高于"白燕2号"(3.1t·hm-2)和"花早2号"(2.2 t·hm-2)。"坝莜1号"秸秆中Na+、K+浓度从开花到成熟均显著增加,而Mg2+、Ca2+和Cl-则显著降低。延迟20 d收获,除Ca2+外,其他离子浓度均显著降低。随着土壤盐分的升高,"白燕2号"秸秆Na+、Mg2+、Ca2+和Cl-浓度显著升高,而K+显著下降。3个品种的Na+、K+和Mg2+之间存在显著差异,而Cl-和Ca2+浓度无显著差异。燕麦秸秆中Cl-浓度最高,K+和Na+基本相当,均高于Mg2+和Ca2+。"坝莜1号"秸秆中Na+、K+、Mg2+、Cl-积累量成熟期最高,延迟收获20 d后积累量均显著降低。"白燕2号"秸秆Na+、K+、Mg2+、Ca2+、Cl-积累量随土壤盐分升高显著下降。除Ca2+外,Na+、K+、Mg2+、Cl-积累量品种之间差异显著。"坝莜1号"秸秆与土壤离子浓度比值中,Na++K+最大(46~63),其次是Cl-(30~46)、Mg2+(24~30)和Ca2+(3~15);延迟收获后Na++K+和Cl-秸秆与土壤浓度比值显著下降,Mg2+比值无显著变化,Ca2+比值显著升高。随着土壤盐分升高"白燕2号"秸秆与土壤Na++K+和Cl-浓度比值显著下降,Ca2+无显著变化。秸秆与土壤离子浓度比值在品种之间存在显著差异。燕麦理论上具有改良盐碱地的潜力,但收获时间和土壤盐分均会显著地影响燕麦生物量、离子浓度和积累量,从而影响燕麦改良盐碱地的效果。     

Effect of Calcium and Potassium Nutrition on Yield,Ion Content,and Salt Tolerance of Brassica campestris (rapa)

When plants encounter salinity, growth is reduced initially by water stress and subsequently by toxic levels of ions and by interference with nutrient acquisition and translocation. Calcium (Ca^{2 +}) in particular seems to have an important role in salt tolerance and there are reports of a beneficial effect of increasing Ca^{2 +} availability. Higher potassium (K⁺) concentrations in plants may also improve salinity tolerance as sodium (Na)⁺/K⁺ ratios have been shown to be important. Previous work with a range of Acacia species has suggested that endogenous seed Ca^{2 +} and K⁺ concentrations might influence salinity tolerance at germination, but this has not previously been tested with a single species. The objectives of this investigation were thus to determine whether (1) altered Ca^{2 +} and K⁺ nutrition of Brassica campestris (rapa) L. plants affects the yield and ion content of their seeds, and (2) seeds with different Ca^{2 +} and K⁺ contents differ in their salinity tolerance. Plants were grown in a growth room or greenhouse in (1) Gem® horticultural sand (2) Silvaperl® perlite and sand (2:1), or (3) Shamrock® Medium General Purpose Irish Sphagnum Peat and Vermiperl® vermiculite (1:1). Plants in each growth substrate were supplied with nutrient solutions based on a modified Hoagland's solution as a control, low Ca^{2 +} and low K⁺ solutions containing those elements at half the control strength, but all other mineral elements as far as possible at control strength, and high Ca^{2 +} and high K⁺ solutions containing those elements at double control strength but all other mineral elements, as far as possible, at control strength. An increase in substrate available Ca^{2 +} and K⁺ resulted in increased Ca^{2 +} and K⁺ concentration in seeds, respectively, and was accompanied by a reduction in seed K⁺ and Ca^{2 +}, respectively. The Ca^{2 +} and K⁺ concentrations of seeds affected their salinity tolerance. Increases in seed Ca^{2 +}, K⁺ or Ca^{2 +}+ K⁺ concentrations decreased salinity tolerance at germination. The results, especially in terms of Ca^{2 +} nutrition, contradict previous results of an increased salinity tolerance with increased Ca^{2 +} and/or K⁺ concentrations.     

Fractionation and Speciation of Manganese in Rhizosphere Soils of Pseudomonas sp. Rhizobacteria Inoculated Pistachio (Pistacia vera L.) Seedlings Under Salinity Stress

Enhancement of manganese (Mn) availability in saline and Mn-deficient soils is very important for plant growth. An experiment was carried out to evaluate the effect of Pseudomonas sp. rhizobacteria (P₀ (control), P₁, P₂ and P₃) and Mn (0 and 10 mg Mn kg^?1 soil) on the distribution of Mn in the rhizosphere of pistachio seedlings under salinity stress (0, 1000 and 2000 mg NaCl kg^?1 soil). The results showed that salinity decreased the dry weight, Mn uptake and chlorophyll content of the pistachio seedlings. However, inoculation with rhizobacteria increased these parameters in saline conditions. Application of rhizobacteria increased the availability of Mn in the rhizosphere soil. The use of rhizobacteria decreased the residual-Mn form in the rhizosphere. Inoculation with rhizobacteria increased the percent of Mn²⁺ and MnCl⁺ species in the soil solution. However, pistachio seedlings inoculation with rhizobacteria increased the contents of Mn available forms in the rhizosphere soil.     

Growth and acquisition of Na,K and Ca in some elite sweetpotato [Ipomoea batatas (Lam.) L.] genotypes under salinity stress

Soil salinity is a concern in the wake of climate change challenges due to rising sea levels and coastal salinity in Papua New Guinea. A greenhouse experiment was conducted in Split Plot design, with five elite sweet potato genotypes (main-plot factors) and three levels of sodium chlroide (NaCl) concentrations (sub-plot factors) replicated six times. The vine cuttings of genotype RAB 45 showed very low mortality percentage (33%) at 600 mM NaCl concentration. At salinity level of 200 mM NaCl, aerial dry biomass of the genotypes was inversely but significantly (r = –0.40; p < 0.05) related to the accumulation of sodium (Na⁺) in the tissues. The Na⁺ accumulation in the tissues was antagonistic to the potassium (K⁺) and calcium (Ca²⁺) ions. Among the sweetpotato genotypes, Na⁺/K⁺ ratio decreased in the following order: RAB 45> KAV 11 > Northern Star > DOY 2 > L 46, which was more or less corroborated with the trend in the aerial dry matter.     

Physiological Response to Sodium Chloride of Wild Swiss Chard

ABSTRACT

The present work was aimed at determining the limits of tolerance to sodium chloride (NaCl) of a halophyte, Beta macrocarpa Guss (wild Swiss chard). Five week-old plants were cultivated with a nutritive solution to which was added 0, 100, 200, and 300 mM NaCl. Plants were harvested after four weeks of treatment. The growth (fresh and dry weight, leaf surface area, and leaf number), water contents, and the mineral composition (meq · g^?1 DW) of roots and leaves (reduced nitrogen (N), K⁺, Ca^{2 +}, Na⁺, Cl^?) were determined on individual plants. Results show that Beta macrocarpa can tolerate up to 200 mM NaCl. A significant decrease in biomass production (to 50% of control) was observed only for 300 mM NaCl. In the latter treatment, leaf mean surface area was 25% of control. The shoot-to-root ratio was not changed. Leaf hydration was not modified by salt treatment. This ability of the plant to maintain the hydric equilibrium of its leaves seemed associated with an efficient intracellular compartmentalization of Na⁺ and Cl^? ions. Salt treatment had little effect on N content (80% of control), but decreased significantly K⁺ and Ca^{2 +} contents. These three essential elements could be limiting for growth of leaves and roots of plants challenged by NaCl.     

Growth,Root Characteristics,and Leaf Nutrients Accumulation of Four Faba Bean (Vicia faba L.) Cultivars Differing in Their Broomrape Tolerance and the Soil Properties in Relation to Salinity

The effects of salinity on four faba bean (Vicia faba L) cultivars [Giza 429, Giza 843, Misr 1 (Orobanche-tolerant), and Giza 3 (Orobanche-susceptible)] and soil properties were investigated in a pot experiment with addition of 0, 50, and 100 mM sodium chloride (NaCl) for 9 weeks. Salinity significantly decreased calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), bicarbonate (HCO₃ ^?), and sulfate (SO₄ ^2?) while significantly increasing sodium (Na⁺), chloride (Cl^?), pH, and electrical conductivity (EC; dS m^?1). Root length density (cm cm^?3), root mass density (mg cm^?3), total dry weight, and salt-tolerance indexes were significantly reduced as a result of application of salinity. The results presented support evidence on the positive relationship between Orobance tolerance and salt tolerance in the three cultivars (Giza 429, Giza 843, and Misr 1). This adaptation was mainly due to a high degree of accumulation of inorganic nitrogen (N), phosphorus (P), K⁺, Ca²⁺, and Mg²⁺ and lesser quantities of Na⁺ and Cl^?, as well as greater K⁺/Na⁺ and Ca²⁺/Na⁺ ratios.     

盐胁迫下柚实生苗生长、矿质营养及离子吸收特性研究

以坪山柚为材料,对盐胁迫下实生苗生长、矿质营养及离子吸收特性进行了研究。结果表明,沙培30d,80～200mmol/L盐胁迫,随盐浓度提高,坪山柚实生苗株高、叶面积、地上部干重和根部干重明显降低。溶液培养8d,坪山柚实生苗地上部及根Na+、Cl-含量随盐浓度的增加而增加,根及地上部K+、Ca2+、Mg2+以及P和Mn含量下降,Fe、Zn、Cu含量的变化因器官而异。其中,地上部Fe含量对盐胁迫敏感,可作为柚耐盐性鉴定指标。40mmol/L盐胁迫,坪山柚地上部K+/Na+、Ca2+/Na+、Mg2+/Na+值均显著下降,且Mg2+/Na+值+/Na+值>1;浓度≥160mmol/L盐胁迫,K+/Na+值+吸收、运转效率比Cl-高。     

Effects of sodium chloride treatments on growth and ion accumulation of the halophyte Haloxylon recurvum

Abstract

Effects of increasing salt concentrations 0, 180, 360 mol im³ sodium chloride (NaCl), on growth, succulence, mineral composition, and glycinebetaine content in Haloxylon recurvum was investigated. Fresh and dry weight of plants increased with an increase in salinity. Succulence of shoots increased at low salinity and decreased at high salinity. Root and shoot Ca⁺, Mg⁺, and K⁺content decreased with increasing salinity while both Na⁺ and Cl^‐ content increased, reaching 4,900 and 5,300 mmol kg^‐1 dry weight, respectively. Glycinebetaine (mol m^‐3 tissue water) significantly increased in shoots at 360 mol m^‐3 NaCl, but did not differ significantly in roots treated with from 0 to 360 mol m^‐3 NaCl. Haloxylon recurvum is a highly salt tolerant stem succulent plant which accumulate a high quantity of salt, which makes it a good candidate to use for phytoremediation in highly saline areas of the sub‐tropics.     

Nitrate Reduction and Nutrient Accumulation in Wheat Grown in Soil Salinized with Four Different Salts

ABSTRACT

The effect of salinization of soil with Na₂SO₄, CaCl₂, MgCl₂, and NaCl (70:35:10:23) on the biochemical characteristics of three wheat (Triticum aestivum L.) cultivars (‘LU-26S,’ ‘Sarsabaz’ and ‘Pasban-90’) was investigated under natural environmental conditions. Twenty-day-old seedlings of all three cultivars were subjected to three salinity treatments: 1.3 (control), 5.0, and 10 dSm^?1 for the entire life period of plants. After 120 d of seed sowing, plant biomass production decreased by 49% and 65%, respectively, in response to 5 and 10 dSm^?1 salinity levels. Addition of salts to growth medium also had a significant adverse effect on plant height. Increasing salinity treatments caused a great reduction in nitrate reductase activity (NRA) of the leaf. The inhibitory effect of salinity on nitrate reduction rate was more pronounced at the reproductive stage than at the vegetative stage of plant growth. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ showed less reduction in NRA due to salinity compared with ‘Pasban-90.’ Ascending salinity levels significantly reduced potassium (K⁺) and calcium (Ca²⁺) accumulation in shoots, while the concentration of sodium (Na⁺) was increased. Salts of growth medium increased the shoot nitrogen (N) concentration, whereas phosphorous (P) concentration of shoots was significantly reduced due to salinity. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ proved to be the salt-tolerant ones, producing greater biomass, showing less reduction in NRA, maintaining low sodium (Na⁺), and accumulating more K⁺ and Ca²⁺ in response to salinity. These two cultivars also showed less reduction in shoot K⁺/Na⁺ and Ca⁺/Na⁺ ratios than in ‘Pasban-90,’ particularly at the 10 dSm^?1 salinity level.     

Responses of barley to hypoxia and salinity during seed germination,nutrient uptake,and early plant growth in solution culture

The resistance of most plants to salt can be impaired by concurrent waterlogging. However, few studies have examined this interaction during germination and early seedling growth and its implications for nutrient uptake. The aim of the study was to examine the response of germination, early growth, and nutrient uptake to salt (NaCl) and hypoxia applied to barley (Hordeum vulgare L. cv. Stirling), in solution culture. Hypoxia, induced by covering seeds with water, lowered the germination from 94% to 28% but salinity and hypoxia together lowered it further to 13% at 120 mM NaCl. While the germination was 75% at 250 mM NaCl in aerated solution, it was completely inhibited at this NaCl concentration under hypoxia. Sodium ion (Na⁺) concentrations in germinated seedlings increased with increasing salinity under both aerated and hypoxic conditions during germination, while K⁺ and Mg⁺ concentrations were decreased with increasing salinity in 6 d old seedlings. After 20 d, control seedlings had the same dry weights of the roots and shoots with and without hypoxia but at 10 mM NaCl and higher, shoot and root dry weight was depressed with hypoxia. Sodium ion increased in roots and shoots with increased NaCl under both aerated and hypoxic conditions while K⁺ was depressed when salinity and hypoxia were applied together and Ca²⁺ was mostly decreased by NaCl. In general, hypoxia had greater effects on nutrient concentrations than NaCl by decreasing N, P, S, Mg, Mn, Zn, and Fe in shoots and by increasing B concentrations. The threshold salinity levels decreased markedly for germination, uptake of a range of nutrients, and for seedling growth of barley under hypoxic compared to well‐aerated conditions.     

COMPARISON OF OSMOTIC REGULATION IN DEHYDRATION- AND SALINITY-STRESSED SUNFLOWER SEEDLINGS

Plant dry matter accumulation rate (DMAR), relative water content (RWC), electrolyte leakage percentage (ELP), chlorophyll content, osmotic adjustment ability (OAA), and osmotica accumulation in leaves of sunflower (Helianthus annuus L.) seedlings under different levels of dehydration and salinity stress induced by iso-osmotic PEG (polyethylene glycol) or sodium chloride (NaCl) were evaluated. Plants were subjected to four stress treatments for 10 days: ?0.44 MPa PEG6000, ?0.44 MPa NaCl, ?0.88 MPa PEG6000, ?0.88 MPa NaCl. Results showed that PEG and NaCl treatments decreased the plant's DMAR and RWC, and NaCl treatments had more severe inhibitory effect on the plants than PEG treatments. Leaf ELP in sunflower seedlings increased after NaCl and PEG treatments. However, leaf ELP under salt stress was higher than that under dehydration stress (PEG treatment). All stress treatments increased OAA in plant leaves. Leaf OAA was enhanced significantly as PEG concentration increases, while leaf OAA was less enhanced at higher concentration of NaCl. OAA of sunflower leaves under dehydration stress was due to an increase in potassium (K⁺), calcium (Ca²⁺), amino acid, organic acid, magnesium (Mg²⁺), and proline content. OAA of sunflower leaves under moderate salt stress was owing to an increase in K⁺, chlorine (Cl^?), amino acid, organic acid, sodium (Na⁺), and proline content, and was mainly due to an accumulation of K⁺, Cl^?, Na⁺, and proline under severe salt stress.     

CONTRIBUTION OF PROLINE AND INORGANIC SOLUTES TO OSMOTIC ADJUSTMENT IN COTTON UNDER SALT STRESS

Physiological responses to salt stress were investigated in two cotton (Gossypium hirsutum L.) cultivars (Pora and Guazuncho) grown hydroponically under various concentrations of NaCl. Dry matter partitioning, plant water relations, mineral composition and proline content were studied. Proline and inorganic solutes were measured to determine their relative contribution to osmotic adjustment. Both leaf water potential (Ψ_w) and osmotic potential (Ψ_s)decreased in response to NaCl levels. Although Ψ_wand Ψ_s decreased during salt stress, pressure potential Ψ_p remained between 0.5 to 0.7 MPa in control and all NaCl treatments, even under 200 mol m^?3 NaCl. Increased NaCl levels resulted in a significant decrease in root, shoot and leaf growth biomass. Root / shoot ratio increased in response to salt stress. The responses of both cultivars to NaCl stress were similar. Increasing salinity levels increased plant Na⁺ and Cl^?. Potassium level remained stable in the leaves and decreased in the roots with increasing salinity. Salinity decreased Ca²⁺ and Mg²⁺ concentrations in leaves but did not affect the root levels of these nutrients. The K/Na selectivity ratio was much greater in the saline treated plants than in the control plants. Osmotic adjustment of roots and leaves was predominantly due to Na⁺ and Cl^? accumulation; the contribution of proline to the osmotic adjustment seemed to be less important in these cotton cultivars.     

Effects of Zeolite on Soil Nutrients and Growth of Barley Following Irrigation with Saline Water

ABSTRACT

Soil salinity is a major abiotic factor limiting crop production but an amendment with synthetic zeolite may mitigate effects of salinity stress on plants. The objective of the study was to determine the effects of zeolite on soil properties and growth of barley irrigated with diluted seawater. Barley was raised on a sand dune soil treated with calcium type zeolite at the rate of 1 and 5% and irrigated every alternate day with seawater diluted to electrical conductivity (EC) levels of 3 and 16 dS m^?1. Irrigation with 16 dS m^?1 saline water significantly suppressed plant height by 25%, leaf area by 44% and dry weight by 60%. However, a substantial increase in plant biomass of salt stressed barley was observed in zeolite-amended treatments. The application of zeolite also enhanced water and salt holding capacity of soil. Post-harvest soil analysis showed high concentrations of calcium (Ca^{2 +}), magnesium (Mg^{2 +}), sodium (Na⁺), and potassium (K⁺) due to saline water especially in the upper soil layer but concentrations were lower in soils treated with zeolite. Zeolite application at 5% increased Ca^{2 +} concentration in salt stressed plants; concentrations of trace elements were also increased by 19% for iron (Fe^{2 +}) and 10% for manganese (Mn^{2 +}). The overall results indicated that soil amendment with zeolite could effectively ameliorate salinity stress and improve nutrient balance in a sandy soil.     

新疆玛纳斯河流域土壤盐分特征研究

以新疆玛纳斯河流域为研究区,结合面域土壤性状调研,利用相关分析和主成分分析方法对区域土壤盐分特征进行研究.结果表明,研究区域土壤盐渍化类型以硫酸盐为主,剖面土壤盐分含量呈现底聚分布特征;土壤盐分含量与SO42-、Ca2+离子含量呈极显著正相关;各层土壤盐分阴离子以SO42-为主,阳离子以Ca2+为主;SO42-、Ca2+、Mg2+及土壤盐分含量(St)是表征玛纳斯河流域土壤盐渍化的主要特征因子.本研究将为新疆玛纳斯河流域土壤资源可持续利用提供重要的理论依据.     

Effects of Silicon Application on Wheat Growth and Some Physiological Characteristics under Different Levels and Sources of Salinity

We investigated the effects of silicon (Si) and the levels and sources of salinity on the growth and some physiological properties of wheat (Triticum aestivum cv. Chamran) in a sandy loam soil under greenhouse conditions. Treatments comprised four Si levels (8, 50, 100 and 150 mg kg^?1 soil), four salinity levels (0.46, 4, 8 and 12 dS m^?1) and two salinity sources (sodium chloride (NaCl) and four-salt combination). Salts combination included NaCl, sodium sulfate (Na₂SO₄), calcium chloride (CaCl₂) and magnesium sulfate (MgSO₄) at a molar ratio of 4:2:2:1. The experiment was arranged as a completely randomized design in a factorial manner, with three replications. Increasing salinity level resulted in a significant decrease in shoot dry weight, chlorophyll content and catalase (CAT) activity, and it caused a marked increase in proline and glycine betaine (GB) concentrations and superoxide dismutase (SOD) enzyme activity. The stimulating effect on GB accumulation and SOD activity was more intense in NaCl-treated plants. However, the source of salinity had no significant effect on shoot dry weight, chlorophyll and proline concentrations, and CAT activity. Si application enhanced all the above-mentioned parameters, except for proline. The suppressing effect of salinity on shoot dry weight, chlorophyll concentration and CAT activity was alleviated by Si supplementation. The stimulating effects of Si fertilization on shoot dry weight and chlorophyll concentration became more pronounced at higher salinity levels. It could be concluded that a decrease in soil osmotic potential, nutrient imbalance and increasing reactive oxygen species (ROS) in salt-treated plants caused growth suppression, while Si supply decreased the deleterious effects of excess salt on wheat growth. Consequently, it appears that when wheat plants are to be grown in salt-affected soils, it is highly recommended to supply them with adequate available silicon (Si).