Na In Shoots Research Articles

One size does not fit all: Different strategies employed by triticale and barley plants to deal with soil salinity

Salinity stress tolerance is a polygenic trait conferred by multiple physiological mechanisms, operating at various levels of plant structural organization. In this work, we have compared adaptative strategies employed by barley and triticale, two most tolerant cereal species, to deal with saline conditions. While the photosynthetic attributes were considerably reduced by 200 mM NaCl treatment in both species, triticale plants maintained higher photosynthetic capacity per unit leaf area compared with barley. Triticale plants also showed higher stomatal conductance under both saline and non-saline conditions, explaining the above photosynthetic rate. However, this high photosynthetic capacity in triticale was not translated into higher biomass (as compared with barley) due to stronger salinity-induced inhibition of tillering in the former species. Leaf elemental analysis revealed that salinity tolerance in triticale was related to its ability to exclude Na+ from the shoot while tolerant barley plant tended to accumulate more Na in shoot upon exposure to salt stress, for osmotic adjustment purposes. Salinity tolerance in both species was also causally associated with higher Fe content that was essential for activation of superoxide dismutase (SOD) to reduce the extent of oxidative stress. Electrophysiological experiments also revealed several patterns associated with control of ion transport in root epidermis, of which desensitization of K+- and Ca2+- ROS-inducible cation channels were the main trait conferring salinity tolerance. Cytosolic K+ retention in the root elongation zone in response to salt stress was more efficient in both triticale genotypes compared to barley. Finally, barley and salt tolerant genotypes of triticale showed higher speed of stomata, thus possessing higher water use efficiency.

Sodium hyperaccumulators in the Caryophyllales are characterized by both abnormally large shoot sodium concentrations and [Na]shoot/[Na]root quotients greater than unity.

Some Caryophyllales species accumulate abnormally large shoot sodium (Na) concentrations in non-saline environments. It is not known whether this is a consequence of altered Na partitioning between roots and shoots. This paper tests the hypotheses (1) that Na concentrations in shoots ([Na]shoot) and in roots ([Na]root) are positively correlated among Caryophyllales, and (2) that shoot Na hyperaccumulation is correlated with [Na]shoot/[Na]root quotients. Fifty two genotypes, representing 45 Caryophyllales species and 4 species from other angiosperm orders, were grown hydroponically in a non-saline, complete nutrient solution. Concentrations of Na in shoots and in roots were determined using inductively coupled plasma mass spectrometry (ICP-MS). Sodium concentrations in shoots and roots were not correlated among Caryophyllales species with normal [Na]shoot, but were positively correlated among Caryophyllales species with abnormally large [Na]shoot. In addition, Caryophyllales species with abnormally large [Na]shoot had greater [Na]shoot/[Na]root than Caryophyllales species with normal [Na]shoot. Sodium hyperaccumulators in the Caryophyllales are characterized by abnormally large [Na]shoot, a positive correlation between [Na]shoot and [Na]root, and [Na]shoot/[Na]root quotients greater than unity.

Cotyledon loss of Astragalus membranaceus hindered seedling establishment through mineral element reallocation and carbohydrate depletion

Tissue loss of plants caused by herbivores is very common in nature. As the storage and first photosynthetic organ, the loss of cotyledon severely impacts dicot seedling establishment and the subsequent growth. However, it is still not clear how plants adjust their metabolic strategy in response to cotyledon loss. In this study, we employed ICP-OES, GC and LC-MS to examine the effects of cotyledon removal (RC1: remove one cotyledon, RC2: remove two cotyledon) on mineral element distribution and metabolite changes in a traditional Chinese herbal plant, Astragalus membranaceus. The results showed that cotyledon removal had a greater effect on shoot than root growth. Specifically, RC2 revealed a more serious impact on shoot growth than RC1. Microelement Mn and Na in shoot increased more in RC2 than RC1. Macroelement K and microelement B in root increased in RC2. The metabolite results in shoot showed that sugars related to galactose metabolism reduced while amino acids significantly increased in RC2. In root, sugars related to fructose and mannose metabolism decreased in both RC1 and RC2 while most flavonoids increased in RC2. It can be concluded that cotyledon removal triggered different metabolic strategies in both root and shoot. In shoot, more Mn was absorbed to improve the lowered photosynthetic efficiency. Meanwhile, increased Na may have promoted carbohydrate consumption and amino acid synthesis, thereby maintaining shoot growth. In root, K and B participation in cell division and expansion increased, as well as the delivery and metabolism of carbohydrates, to maintain root system growth.

Salt tolerance in Argentine wheatgrass is related to shoot sodium exclusion

AbstractThis is the first report about Na and K fluxes and heritability of Na exclusion in the Elymus genus. Argentine wheatgrass [Elymus scabrifolius (Döll) J.H. Hunz.] is an important forage genetic resource for saline environments. A previous study showed that salt‐sensitive lines accumulated toxic levels of Na in shoots. The aim of this study was to increase the understanding of Na exclusion in Argentine wheatgrass. Growth and Na and K accumulation rates were analyzed in two homozygous salt‐tolerant genotypes (T1 and T2) and a salt‐sensitive genotype (S1), under different salt stress levels. The Na accumulation rate in shoots was 1.5 times higher in the sensitive line than in the tolerant ones at 100 mM NaCl, and five times higher at 200 mM NaCl. A negative association was found between Na concentration and leaf weight in parent genotypes, F1, and segregating F2 populations generated by crossing homozygous S1 and T2, suggesting that growth in the third leaf was more affected in Na‐including genotypes. The inheritance of Na exclusion was estimated under salt stress conditions in a segregating F2 population and in F2:3 families obtained by crossing two homozygous genotypes with contrasting values of shoot Na exclusion. In the F2 population and F2:3 families, Na concentration segregation was compatible with intermediate inheritance (with very low partial dominance). High heritability values estimated for Na exclusion suggest that this trait might be used as a priority selection criterion for salt tolerance. Results will be useful to design breeding strategies for salt tolerance in this and related species of the Elymus genus.

Factors of Soil Properties and Elements in Tissues Influencing on Extent of Arsenic Accumulation in Brown Rice

Recently, As-contaminated soil management has started dealing with phytoavailable As content instead of total As content in soils. Phytoavailable As content is known to consider food safety more than the management of the environment. This study aims to predict As content in brown rice using phytoavailable As concentration in soil and soil properties and to see the relationship between element contents in tissues and As in brown rice. As-contaminated soils were collected, and their total and phytoavailable As content and soil properties were analyzed. Mehlich3 extraction method was used for phytoavailable As analysis. After the analysis, correlations among total and phytoavailable As concentrations in soils, As content in rice and soil properties were analyzed. Then, a prediction model of As content in brown rice was developed through multiple stepwise regression. Also, correlation analysis between nutrients and As contents in rice was conducted to identify the factors affecting As accumulation in brown rice. The modelling equation for estimating As concentration in brown rice was [Log (As in brown rice) = 2.45 + 0.13 × Log (As_Mehlich3) – 0.99 × Log (CEC) + 0.50 × Log (avail.-P)] (r = 0.49, p < 0.001). Soil avail.P concentration and CEC were valid variables for As accumulation in brown rice. In addition, Cu, Zn, Mo and Na in shoot were revealed to influence governing translocation of As from shoot to grain. Regression models for estimating As concentration in brown rice using total and phytoavailable As content in paddy soils, combined with soil avail.-P and CEC values. Parameter r p value Log (As_R†) = 2.98 ‒ 0.08×Log (Total As_S†) 0.13 0.318 Log (As_R) = 2.15 ‒ 0.06×Log (Total As_S) + 0.42×Log (avail.-P) 0.31 0.041 Log (As_R) = 2.63 + 0.01×Log (Total As_S) + 0.59×Log (avail.-P) ‒ 1.00×Log (CEC) 0.44 0.004 Log (As_R) = 2.15 + 0.17×Log (As_M3§) 0.28 0.022 Log (As_R) = 2.89 + 0.18×Log (As_M3) ‒ 0.72×Log (CEC) 0.38 0.008 Log (As_R) = 2.45+ 0.13×Log (As_M3) ‒ 0.99×Log (CEC) + 0.50×Log (avail.-P) 0.49 0.001 †As concentration in brown rice†Total As concentration in soil§Mehlich3-extractable As concentration in soil

Microencapsulation: Toward the Reduction of the Salinity Stress Effect on Wheat Plants Using NPK Rhizobacteria

Salinity is one of the most vicious environmental factors controlling the productivity of crop plants as most of the crop plants are sensitive to salinity affected by high concentrations of salts in the soil. The objective of this study was to evaluate the influence of the inoculation with the encapsulated and liquid culture of three halo-tolerant plants growth-promoting rhizobacteria (PGPR) strains of Paenibacillus polymyxa MSRH5, Bacillus nakamurai MSRH1 and Bacillus pacificus MSR H3 on the growth and yield of wheat (Triticum aestivum L.). The three strains MSRH1, MSRH3 and MSR H5 were characterized as salt-tolerant bacteria. P. polymyxa MSRH5 had nitrogen fixation ability while B. nakamurai MSRH1 and B. pacificus MSRH3 were able to solubilize phosphate and K respectively. All strains can produce indole acidic acid (IAA) and exopolysaccharides (EPS) under saline conditions. Encapsulated beads were observed under Scanning Electron Microscope (SEM). Colonization of encapsulated bacteria on the root of the wheat plant was studied by Transmission Electron Microscopy (TEM). Under soil salinity conditions in two consecutive field tries, results cleared that strains in two forms succeed to colonize the plant root, the reduction in shoot proline was 35.8% with capsules inoculation as well as improved relative water content (%) to 60.57% and improved the electrolyte leakage recorded 18.1% respectively compared to control. Generally, halo-tolerant PGPR inoculation increased DHA (?), acidic and alkaline phosphatase activities compared to control, inoculation with capsules exhibited a reduction in catalase enzymes 46.00%, 37.5% in ascorbate peroxidase and 40% in superoxide dismutase respectively in shoots of the wheat plant. There is a significant increase in all yield parameters, the highest plant height 115.8 cm, spike length 21 cm and 1000 grains 71.3 g respectively recorded with capsules inoculation, it had considerable effects on the content of N, P, K and Na in shoots of wheat plants and reduced the value of Na/K ratio in all treatments inoculated compared to un-inoculated wheat plant.

BIOCHEMICAL STUDIES ON THE EFFECT OF SOME BIOFERTELIZERS ON SOYBEAN SHOOTS

The field excrement was conducted in the agronomy farm of Gazala, Sharkia, Egypt to study the effect of power mix, citrine and super blue green biofertilizers on some biochemical contents of soybean shoots of (Giza111 and Crawford) varieties. The following results were recorded: - 1- All doses of biofertilizers increased dry weight content of shoots to both varieties of soybean. Giza111 variety recorded relatively greater values than those of Crawford variety. 2- The concentration of chl. a, chl. b and total chl. Of shoots soybean were increased by all treatments while decreased the concentration of carotenoids in shoots only at early stages of Giza111 variety, but increased of crawford variety at all stages of growth. 3- The percentage of total soluble sugars (reducing and non-reducing) in shoots of crawford variety were greater than those of giza111 variety and the highest increase of total soluble sugars was obtained by the foliar application of 0.25% and 0.5% super blue green biofertilizers. 4- All treatments were increased the concentration of soluble, insoluble and total nitrogen fractions in both varieties of soybean shoots at all stages of growth. 5- All doses of biofertilizers decreased the concentration of Na in shoots of both varieties of soybean, while they were increased the concentration of P and K at all stages of growth. 6- Fe, Zn and Mn contents were slightly increased by the application of biofertilizers at the early and second stage of growth, while they decreased values at the late stage of shoots growth. Conclusively, from the current results, it can be noticed that the application of all biofertilizers increased dry weight, photosynthetic pigments (chl. a, chl. b and carotenoids), the percentage of total nitrogen were increased either with all doses of biofertilizers in both varieties of soybean (Giza111 and Crawford). the highest increase of total soluble sugars was obtained by the foliar application of 0.25% and 0.5% super blue green biofertilizers especially in Giza111 variety. All micro and macro elements were increased (Na, K, P, Fe, Zn, Mn) except Na on all soybean vaterites.

NUTRIENT CONTENT IN SUNFLOWERS IRRIGATED WITH OIL EXPLORATION WATER

ABSTRACT: Irrigation using produced water, which is generated during crude oil and gas recovery and treated by the exploration industry, could be an option for irrigated agriculture in semiarid regions. To determine the viability of this option, the effects of this treated water on the nutritional status of plants should be assessed. For this purpose, we examined the nutritional changes in sunflowers after they were irrigated with oil-produced water and the effects of this water on plant biomass and seed production. The sunflower cultivar BRS 321 was grown for three crop cycles in areas irrigated with filtered produced water (FPW), reverse osmosis-treated produced water (OPW), or ground water (GW). At the end of each cycle, roots, shoots, and seeds were collected to examine their nutrient concentrations. Produced water irrigation affected nutrient accumulation in the sunflower plants. OPW irrigation promoted the accumulation of Ca, Na, N, P, and Mg. FPW irrigation favored the accumulation of Na in both roots and shoots, and biomass and seed production were negatively affected. The Na in the shoots of plants irrigated with FPW increased throughout the three crop cycles. Under controlled conditions, it is possible to reuse reverse osmosis-treated produced water in agriculture. However, more long-term research is needed to understand its cumulative effects on the chemical and biological properties of the soil and crop production.

Potássio, sódio e crescimento inicial de espécies florestais sob substituição de potássio por sódio

A substituição de potássio (K) por sódio (Na) é reconhecida na literatura por aumentar a produtividade de algumas plantas, porém se conhece pouco sobre o comportamento em espécies florestais. Por isso, o objetivo deste estudo foi avaliar o crescimento inicial de Enterolobium contortisiliquum e Sesbania virgata na substituição de K por Na em solução nutritiva de Hoagland e Arnon. O esquema fatorial foi 2 x 5, sendo duas espécies florestais e cinco níveis de substituição (0; 33,3; 50; 66,6; e 100%), com quatro repetições. O experimento foi instalado em vasos Leonard com capacidade para 1 L, com a troca periódica da solução nutritiva. A colheita foi realizada aos 50 dias após o início do estudo, quando se avaliaram as características morfométricas das mudas. O material foi lavado e seco, e determinou-se a matéria seca das raízes, das folhas e do caule. O material radicular e o da parte aérea foram triturados e submetidos às análises de K e Na. Por cálculo, obtiveram-se a matéria seca da parte aérea (caule + folhas), a razão de raízes/parte aérea e o acúmulo de K e Na nas raízes e na parte aérea. A substituição de K por Na promoveu diferenças significativas no desenvolvimento das mudas, nos teores e acúmulos de K e Na. A espécie Sesbania virgata apresentou o melhor desenvolvimento inicial e acumulou maior quantidade de K e Na na parte aérea.

Characterization of physiological responses of two alfalfa half-sib families with improved salt tolerance

Alfalfa (Medicago sativa L.) is a major forage crop worldwide that is relatively sensitive to soil salinity. Improved cultivars with high production on saline soil will benefit many producers and land managers. This study reports the characterization of physiological responses of two unrelated experimental alfalfa half-sib families, HS-A and HS-B, selected for their improved survival under saline conditions (up to EC 18). Six-week-old plants were subjected to NaCl-nutrient solution treatment for three weeks starting at an electrical conductivity (EC) of 3 dS m(-1) with incremental increases of 3 dS m(-1) every week, reaching 9 dS m(-1) in the third week. HS-B showed greater leaf number (72%) and stem length (44%) while HS-A showed better leaf production (84%) under salt treatment compared to the initial genetic backgrounds from which they were developed. This improved growth is associated with 208% and 78% greater accumulation of chlorophyll content in HS-B and HS-A, respectively. Both HS-A and HS-B also showed improved capability to maintain water content (RWC) under salt stress compared to the initial populations. Differing from its initial populations (P-B), HS-B did not accumulate Na in shoots after salt treatment. HS-B also maintained K(+)/Na(+) and Ca(2+)/Na(+) ratios, while P-B showed 59% and 69% decrease in these ion ratios, respectively. Na(+) content in HS-A was not different from its initial populations (P-A) after salt treatment. However, HS-A showed an enhanced accumulation of Ca(2+) and maintained the levels of Mg(2+) and K(+) in shoots compared to the P-A populations. This study provides physiological support of improved salt tolerance in HS-A and HS-B and suggests that these plants maintain ion homeostasis but have different mechanisms of coping with high salinity.

GROWTH INHIBITION AND CHANGES IN NUTRIENT ACCUMULATION IN CUCUMBER PLANTS UNDER SALINITY CONDITIONS

Soil salinity affects plant growth, including germination, reproductive development and yield. The most common soil salt, sodium chloride (NaCl) produces ionic toxicity, osmotic stress and nutrient deficiencies in plants, mainly of N, Ca, K, P, Fe and Zn. In this research we evaluated the response of two cultivars of cucumber (AF-1661 and Slice Max) to five NaCl concentrations (0, 50, 100, 150 and 200 mM) in the nutrient solution. Plants were grown under greenhouse using red tezontle (inert red volcanic gravel) as substrate and the nutrient solution of Steiner at 100%. The different levels of NaCl were applied during 60 days after transplanting. Height of plant, weight of fresh and dry matter of shoot and roots as well as concentration and accumulation of Ca, K, Mg, P, Na and N in shoot and roots were determined. The nutrient accumulation was estimated using the nutrient concentration and the weight of dry matter of shoot and roots. The cultivar 'AF-1661' had significant reductions in plant height with the addition of 150 mM NaCl. Salinity reduced the accumulation (mg/organ) of P, K, Ca, Mg and N, as well as the K/Na ratio both in shoot and in roots in both cultivars, because of antagonism between these macronutrients with the Na. At 200 mM NaCl, the cultivar 'Slice Max' showed higher sensibility to salinity than 'AF-1661', as this cultivar was unable of blocking the Na transport to shoots and therefore a higher accumulation of Na in shoots that caused leaf necrosis was observed.

Leaf number indicates salt tolerance of young seedling families of European aspen (Populus tremula L.) growing in different soils

Soil salinity limits plant productivity and quality. We evaluated the response of 12 aspen (Populus tremula) families to salt stress in two different soils irrigated for 4-weeks with 0, 80 or 160 mM saline solution. Easily measurable characteristics such as shoot height, leaf number, dry mass as well as the distribution of sodium (Na) ions were measured in 5-month-old aspen seedlings raised in controlled greenhouse conditions on two different soils. Growth among families varied significantly, and the interaction between family and soil type was significant. From 2–5 months, leaf number correlated with that of the first month and salinity tolerance. Sodium ions varied significantly within plants and among families; seedlings that accumulated higher Na concentrations in root had more leaves and lower Na in shoot. These results suggest that leaf number indicates salt tolerance in young seedlings. Seedling performance was also affected by soil type, especially the root/shoot ratio, suggesting an interaction between salt tolerance and growth medium. This study has identified significant intra-specific variation in salt tolerance of aspen in 160 mM saline and highlighted the potential to select and develop a method for efficient pre-screening of trees to be used in the reclamation of salt-affected land.+++

Zinc influence and salt stress on photosynthesis, water relations, and carbonic anhydrase activity in pistachio

A greenhouse study was conducted to evaluate the ameliorative effects of zinc (0, 5, 10 and 20 mg Zn kg −1 soil) under saline (800, 1600, 2400 and 3200 mg NaCl kg −1 soil) conditions on pistachio ( Pistacia vera L. cv. Badami) seedlings’ photosynthetic parameters, carbonic anhydrase activity, protein and chlorophyll contents, and water relations. Zn deficiency resulted in a reduction of net photosynthetic rate and stomatal conductance. The quantum yield of photosystem II was reduced at zinc deficiency and salt stress. Zinc improved plant growth under salt-affected soil conditions. Increasing salinity in soil under Zn-deficient conditions, generally decreased carbonic anhydrase activity, protein, chlorophyll a and b contents. However, these adverse effects of salinity alleviated by increasing Zn levels up to 10 mg kg −1 soil. Under increasing salinity, chlorophyll a/b ratio significantly increased. Zinc treatment influenced the relationship between relative water content and stomatal conductance, and between leaf water potential and stomatal conductance. It concluded that Zn may act as a scavenger of ROS for mitigating the injury on biomembranes under salt stress. Adequate Zn also prevents uptake and accumulation of Na in shoot, by increasing membrane integrity of root cells.

III.Heat stress in Triticum: kinetics of Na, K and P accumulation

Genotypes of bread and durum wheat were submitted to heat stress after anthesis and the accumulation of Na, K and P, at booting, grain filling and maturity, were investigated. It was found that, after anthesis, the levels of Na in shoots were considerably higher in durum relatively to bread wheat, being this trend also observed in the total plant accumulation. In these genotypes, heat stress affected significantly Na concentration in shoots. In general, heat stressed plants had significant higher levels of K in the shoots and the proportion of this nutrient translocation from the roots also increased with heat stress. In general, the levels of P didn't show significant differences with heat stress. The effects of heat stress among the wheat genotypes life cycle are characterized and discussed.

Comparative Effect of Nitrogen Sources on Maize under Saline and Non‐saline Conditions

AbstractThe main objective of this study was to compare the relationship between biomass yield and nutrient uptake in salt‐stressed maize (Zea mays L.) following nitrogen (N) nutrition in a greenhouse. Three forms of N were applied, each at the rate of 100 kg ha−1: urea‐N, nitrate‐N, 1/2 urea‐N + 1/2 nitrate‐N (mixed‐N) and no N application (control). Maize was grown as a test crop for 6 weeks. All N sources greatly stimulated crop growth and nutrient uptake compared with the control. The biomass (shoot and root) of maize was significantly greater in mixed‐N treatment than in single sources in saline soil whereas it varied in the order of urea‐N &gt; mixed‐N &gt; nitrate‐N &gt; control in non‐saline soil. Under both soil conditions, the concentration of Ca, Mg and Na in shoot was highest in nitrate‐N treatments while that of K was highest in the control. Shoot nitrogen concentration was not significantly different among N sources under non‐saline treatment, whereas under saline conditions, the concentration varied markedly in the order of nitrate‐N &gt; urea‐N &gt; mixed‐N &gt; control. The mineral concentrations in the shoot increased under salt treated soil when compared with non‐saline soil. The ratios of Na/K, Na/Ca and Na/Mg were also higher under salt stress due to higher accumulation of Na ion in the shoot. Among N‐fertilizer sources, Na/Ca and Na/Mg ratios were highest in control whereas Na/K ratio was the highest in nitrate‐N treatment. The lowest cation ratios were noted in mixed‐N‐treated plants under both soils. Regression analysis showed that maize biomass was related to N concentration by the following equations: Y = −4.54 + 0.97N for the non‐saline soil and Y = 0.89 + 0.25N for the saline soil. Nitrogen use efficiency for non‐saline soil exceeded that of saline soil by 15 %.

An agronomic and physiological re-evaluation of the potassium and sodium requirements and fertilizer recommendations for sugar beet

SUMMARYThe potassium (K) and sodium (Na) requirements of sugar beet were re-examined in a 6-year series of experiments between 2000 and 2005 using reference plots with a wide range of long-established differences in exchangeable topsoil K (Kex). Two groups of plots with a topsoil concentration Kex range of 40–550 mg/kg were used, each situated within an individual field, one on a silty clay loam at Rothamsted and the other on a contrasting sandy loam at Woburn. The interactions between topsoil Kex and applied N, K and Na fertilizers were studied at Rothamsted. Under these well-defined conditions, maximum yields of 55–71 t/ha of adjusted clean beet were achieved with a topsoil Kex concentration of 120–150 mg/kg, i.e. at Soil K Index 2–, with a small difference between the two soils being accounted for by differences in exchangeable soil Na and subsoil Kex. There were no yield responses to freshly applied fertilizer K, even on low K plots where responses might be expected. It is concluded that the existing recommendations for K fertilizer use on UK sugar beet do not need to be adjusted to allow for the higher yields of modern crops.There were no yield responses to NaCl fertilizer at any level of topsoil Kex at Rothamsted (where the soil contained 15–20 mg Na/kg), but yields were increased on low Kex plots at Woburn whose sandy loam contained only 5–10 mg Na/kg. The uptake of Na from the applied NaCl fertilizer was strongly influenced by the exchangeable K and Na status of the soil. On the low Na soil at Woburn, almost all of the applied Na was taken up by sugar beet grown on plots with low concentrations of topsoil Kex and half of it on plots with adequate concentrations of topsoil Kex compared with two-thirds and one-fifth, respectively, on the higher Na-content soil at Rothamsted.Plants partitioned 0·75 of their K and 0·95 of their Na to the shoot and the balance to the storage root. This pattern of distribution was consistent across sites, seasons and soil K supply. The physiological interactions between K and Na were studied by examining their millimolar concentrations in the tissue-water (mmol/kg) of the shoots and storage roots. The tissue-water concentrations of K in the shoot increased asymptotically with the concentration of Kex in the topsoil, and the increase in K concentration was accompanied by a corresponding decrease in the tissue-water concentration of Na. Maximum concentrations of K in shoot tissue-water (and minimum concentrations of Na) were achieved when the topsoil contained a minimum of 200 mg Kex/kg. The optimal physiological tissue-water concentration of Na in shoots was estimated to be c. 90–100 mmol/kg; maintenance of this level required a minimum of 25 mg/kg of exchangeable Na in the topsoil. When not limited by soil Kex, plants maintained a total tissue-water concentration of c. 300–350 mmol/kg of K+Na within the shoot. This was achieved with 80 mmol of Na and 230 mmol of K/kg of tissue water on the high Na-content soil at Rothamsted, and with 40 mmol of Na and 275 mmol of K/kg tissue water on the low-Na soil at Woburn.Significant correlations were established between measurements of beet K made in the factory tarehouse and those made using standard laboratory chemical analyses and between factory estimates of the concentrations of K in the tissue-water of delivered beet and the topsoil Kex. The uses of these relationships to estimate the off-takes of K in the harvested beet and provide feedback to growers on the K status of their soils, and the implications of the study for the use of K and Na fertilizers on UK sugar beet are discussed.

Genotypic variation in the response of pepper to salinity

Using 102 pepper (Capsicum annuum) genotypes, a greenhouse experiment has been conducted to study genotypic variation in tolerance to 100 mM sodium chloride (NaCl) in nutrient solution. Based on the severity of leaf symptoms caused by the NaCl treatment there was a substantial genotypic variation in salt tolerance. From this screening experiment, six sensitive and six tolerant genotypes were chosen to study dry matter production and root and shoot concentrations of sodium (Na), potassium (K) and calcium (Ca) in a growth chamber experiment in a nutrient solution with and without 150 mM NaCl. The genotypes selected as sensitive were highly damaged and developed severe chlorosis and necrosis under NaCl treatment, while the genotypes selected as tolerant were slightly affected. On average, decreases in shoot dry matter production caused by NaCl were greater in the sensitive than the tolerant genotypes. Application of salt increased shoot Na concentration at greater amount in the sensitive than the tolerant genotypes. Of the tolerant genotypes, the genotype Cac (Capsicum annuum var. cerasiforme) and 1245 F1 had around 2.45% Na in shoot while the sensitive genotypes Kandil and Pazarcik contained, on average, 5.4% Na. All sensitive and tolerant genotypes exhibited more or less similar shoot concentrations of K and Ca. There was very significant and positive correlation between severity of leaf symptoms and shoot Na concentration, but no correlation could be found in the case of K or Ca concentrations with the severity of leaf symptoms. The results indicate existence of substantial genotypic variation in tolerance to NaCl stress in pepper. It seems very likely that exclusion of Na from roots into growth medium plays a critical role in expression of high Na tolerance in pepper. # 2006 Published by Elsevier B.V.

Salt tolerance of grain crops in relation to ionic balance ability to absorb microelements

A greenhouse experiment was conducted to investigate the effect of exchangeable Na on the growth and absorption of metal elements in barley, rye, and maize. The plants were cultivated in soils whose exchangeable sodium percentages (ESP) were 6.6 (saline soil: Saline), 17.4 (saline-sodic soil: Sodic 1), and 39.6 (sodic soil: Sodic 2), which were prepared from Tottori sand dune soil (Control). The dry weight (DW) and concentrations of metal elements Ca, Mg, Mn, Zn, and Cu) in shoots were analyzed. The shoot DW was smaller with higher ESP, but in barley the difference between all the treatments was no longer observed with time. In Sodic soils, the growth of barley was vigorous, whereas rye growth was poor, and maize plants died by 5 weeks after planting. The Na concentration in shoots of all the species was higher with higher ESP. The K concentration in shoots was low at the early growth stage, but in barley it was higher in the Saline and both Sodic soils than in the Control at the subsequent stages. The concentrations of Ca and Mg in shoots of barley and maize in the Saline and both Sodic soils were higher than those in the Control, but in rye the concentrations were lowest in Sodic 2. The concentrations of Mn, Zn, and Cu in barley shoots in the Saline and bothSodic soils tended to be higher than those in the Control, whereas in rye they were lower than in the Control in both Sodic soils. Barley showed a higher ability to absorb low available microelements than rye and maize. These results indicate that barley is tolerant to sodicity as well as salinity, maize is tolerant to salinity, but is very sensitive to sodicity, and rye is moderately sensitive to both stresses. We suggest that the tolerance of grain crops to ESP involves a tolerance to a high Na concentration in shoots, the ability to keep suitable concentrations of essential cations in the presence of a high concentration of Na in shoots and the ability to absorb low available microelements.

Salt Response of Chickpea as Influenced by N Supply1

AbstractProduction of chickpea (Cicer arietinum L.) in semiarid and coastal areas may be limited by the salt sensitivity of the chickpea symbiosis. Accordingly, this study was done to analyze effects of salt on the symbiosis by comparing the NaCl tolerance of chickpea‐specific strains of Rhizobium with tolerance of the chickpea plant grown either with combined N or dependent on symbiotic N2‐fixation. Effects of supplemental N on the salt response of symbiotic chickpea were also tested.In greenhouse sand cultures, growth of chickpea was depressed by NaCl at only 20 mM concentration unless mineral N was provided. With no added NaCl 22 strains of rhizobia were all effective, producing plant yields comparable with NH4NO3 control treatments; but with NaCl added at 75 mM only 1 strain did significantly better than controls with no N or inoculum. Poor symbiotic performance was not due to salt limitation of growth of rhizobia. Rhizobial growth rates determined by viable counts in yeast mannitol medium were unaffected by NaCl at 120 mM and only moderately depressed by 250 mM.Effects of supplemental N were studied in a solution culture experiment with four levels of NaCl (0, 15, 23, and 31 mM) combined factorially with four different N treatments: NH4NO3 absent, present continuously, present only during the first 31 days, or present only after onset of vigorous fixation at 31 days. The growth of both N‐fertilized and symbiotic plants was inhibited by salt. Ammonium nitrate moderated salt stress most strongly during the later period of growth (after 31 days). Growth inhibition of N‐fertilized plants was associated with excess Cl accumulation in shoots, which occurred regardless of N treatment. Additional effects could account for the greater inhibition in symbiotic plants. Salt delayed nodulation, and N‐treated plants showed greater retention of Na in roots and lower concentrations of Na in shoots than completely symbiotic plantsThe data indicate a clear need for greater salt tolerance in chickpea. And since the nature of the salt response changed markedly with N‐source, selection of cultivars and testing of management procedures should be done with both N‐fertilized and symbiotic plants.