Characterization of cell surface material removed by water and NaCl washing ofParacoccus denitrificans grown under conditions of divalent cation deficiency and sufficiency

Paracoccus denitrificans grown on complex medium deficient in Mg²⁺ and Ca²⁺ are rendered lysozyme susceptible by washing with NaCl, whereas cells grown in a succinate-salts medium (Mg²⁺ and Ca²⁺ sufficient) or complex medium supplemented with Mg²⁺+Ca²⁺ are not. The material released by water washing of cells grown on complex medium and complex medium supplemented with Mg²⁺ and Ca²⁺ was characterized by a high protein content. There was a high lipid: protein ratio and an appreciable amount of 3-deoxyoctulosonic acid in the material released by NaCl washing of cells grown under all conditions, indicating release of outer membrane material. The lipid ornithine: lipid phosphorous ratios of NaCl wash from cells grown on complex medium and complex medium supplemented with Mg²⁺ and Ca²⁺ were 0.54 and 0.34, respectively. Although NaCl washing removed outer membrane material from cells grown under all conditions, only divalent cation deficient cells were rendered lysozyme susceptible. This might be explained by the increased outer membrane ornithine-containing lipid to phospholipid ratio in these cells yielding a more permeable outer membrane.     

Tolerance ofHolcus lanatus andAgrostis stolonifera to sodium chloride in soil solution and saline spray

Summary Inland and sea cliff populations of bothAgrostis stolonifera L. andHolcus lanatus L. were subjected to soil NaCl treatments, of 100 and 200 mol m⁻³ NaCl, and tolerance examined using plant dry weight data. A parallel experiment subjected them to salt spray treatments of 2.5%, 5% and 10% NaCl in distilled water, and tolerance assessed from leaf damage. Both populations of each species were equally sensitive to soil NaCl. When subjected to salt spray the sea cliff populations however showed marked resistance to leaf damage. Soil salinity resistance and salt spray resistance thus appear to be independent characteristics in these two species.     

Effects of sodium chloride and polyethylene glycol on root-hair infection and nodulation of Vicia faba L. plants by Rhizobium leguminosarum

The effects of sodium chloride and polyethylene glycol (PEG) on the interaction between Rhizobium leguminosarum strain 29d and root hairs of field bean (Vicia faba L. cv. Maris Bead) plants were investigated. Two levels each of NaCl (50 and 100 mol·m^–3) and PEG (100 and 200 mol·m^–3) were given at the time of root-hair formation. Scanning electron microscopy showed rhizobial attachment and colonization on root-hair tips. Adhesion of rhizobia in both lateral and polar orientation, sometimes associated with microfibrils, occurred mainly in crooks at the root-hair tips; most of the infections also occurred here. Bacterial colonization and root-hair curling were both reduced by stress treatments. Polyethylene glycol but not NaCl significantly reduced root-hair diameter. The proportion of root hairs containing infection threads was reduced by 30% under NaCl and by 52% under PEG. The structure of some of the root hairs, epidermal and hypodermal cells, as seen by light microscopy in ultrasections, was distorted as a result of NaCl and PEG treatments; cells showed plasmolysis and folded membranes. After three weeks of treatment, both NaCl and PEG inhibited nodule number by about 50% and nodule weight by more than 60%. It is concluded that the root-hair infection process in Vicia faba is impaired by NaCl and PEG treatments and this in turn results in fewer nodules being produced.Abbreviation PEG polyethylene glycol     

Salinity and Temperature Effects on Germination for Three Salt-resistant Euhalophytes, Halostachys caspica, Kalidium foliatum and Halocnemum strobilaceum

The effects of three salinities (0, 100 and 500 mM NaCl) and four constant temperatures (10, 20, 30 and 35 °C) on seed germination of Halostachys caspica (M. B.) C. A. Mey., Kalidium foliatum (Pall.) Mop. and Halocnemum strobilaceum (Pall.) Bieb. were investigated. After seeds were treated with different concentrations of NaCl at constant temperatures of 10–35 °C for 16 days, ungerminated seeds were transferred to distilled water for 10 days to investigate the total germination; after this time, the ungerminated seeds from the 10 and 20 °C treatments were then moved to 35 °C for another 5 days to determine the final germination. The three plant species in the present experiment are salt-resistant euhalophytes growing in high saline soils in the Zhungur Basin in Xinjiang, a northwest province of China.Compared with germination under control conditions, germination percentages of all three species were not affected by 100 mM NaCl at 10–35 °C, while severely inhibited by 500 mM NaCl; germination percentages were very low at 10 °C up to 100 mM NaCl for all species; the optimum temperature for germination of H. caspica and K. foliatum was 20–30 °C, while 35 °C for H. strobilaceum, up to 100 mM NaCl; seeds did not suffer ion toxicity for all species, as evidenced by the high total germination after ungerminated seeds pretreated with 500 mM NaCl were transferred to distilled water at constant temperatures of 10–35 °C for 10 days, and the high final germination after the ungerminated seeds from the 10 and 20 °C treatments were subsequently moved to 35 °C for another 5 days; Halostachys caspica had greater sensitivity to increasing temperatures from 10 and 20 °C to 35 °C compared with the other two species.     

Salt impact on photosynthesis and leaf ultrastructure of <Emphasis Type="Italic">Aeluropus littoralis</Emphasis>

The effects of salinity (400 mM NaCl) on growth, biomass partitioning, photosynthesis, and leaf ultrastructure were studied in hydroponically grown plants of Aeluropus littoralis (Willd) Parl. NaCl produced a significant inhibition of the main growth parameters and a reduction in leaf gas exchange (e.g. decreased rates of photosynthesis and stomatal conductance). However, NaCl salinity affected neither the composition of photosynthesis pigments nor leaf water content. The reduction in leaf gas exchange seemed to correlate with a decrease in mesophyll thickness as well as a severe disorganisation of chloroplast structure, with misshapen chloroplasts and dilated thylakoid membranes. Conspicuously, mesophyll chloroplasts were more sensitive to salt treatment than those of bundle sheath cells. The effects of NaCl toxicity on leaf structure and ultrastructure and the associated physiological implications are discussed in relation to the degree of salt resistance of A. littoralis.     

蒭雷草对盐胁迫的生理响应

该文选择从西沙东岛采集蒭雷草,通过分株繁殖挑选健壮植株作为材料,模拟热带珊瑚岛生境设置不同浓度NaCl处理,研究不同程度的盐胁迫对其植株叶片丙二醛(MDA)、抗氧化酶以及渗透调节物质的影响.结果表明:(1)短期(28 d)盐胁迫下,NaCl浓度的增加并未加速蒭雷草叶片细胞发生膜脂过氧化作用,MDA含量增加幅度较小;随着...     

The wall associated lipoteichoic acid ofStreptococcus sanguis

A competitive ELISA is described for the measurement of lipoteichoic acid. The assay was used to determine the wall associated lipoteichoic acid ofStreptococcus sanguis which was found to represent only 2–4% of the phenol extractable content. Extracellular lipoteichoic acid was detected even after exhaustive cell washing. This material was not the result ofde novo synthesis because membrane de-polarization had no effect on the amount detected. Since extracellular lipoteichoic acid interfered with the measurement of cell surface antigen, cells were fixed with glutaraldehyde prior to assay. Lipoteichoic acid was demonstrated on the surface of fixed cells which did not leak antigen. The relevance of fixation used in antigen location studies by electron microscopy of immune-labelled cells is discussed.     

Enhanced Tonoplast H+-ATPase Activity and Superoxide Dismutase Activity in the Halophyte Suaeda salsa Containing High Level of Betacyanin

In this study, high-betacyanin Suaeda salsa seedlings were developed and used to explore whether the betacyanin accumulation is related to salinity tolerance in S. salsa. After 8 days of culture, betacyanin content decreased markedly in both high-betacyanin S. salsa seedlings and the control under nonsalt stress, but the decreases were suppressed by NaCl treatments. Betacyanin content in high-betacyanin seedlings was much higher than that in the control throughout the salt treatments. Growth of S. salsa plants was significantly promoted by NaCl treatments, and the fresh weight of high-betacyanin seedlings was much higher than that of the control when grown in 400 mmol L⁻¹ NaCl. Similar cell sap osmolarity and K⁺/Na⁺ ratios were observed in high-betacyanin seedlings and the control. No obvious differences in V-ATPase (tonoplast H⁺-ATPase) activity, leaf SOD (superoxide dismutase) activity, and total chloroplast SOD (including thylakoid-bound SOD and stroma SOD) activity were detected between high-betacyanin seedlings and the control under nonsalt stress conditions. However, V-ATPase hydrolytic activity increased dramatically in S. salsa seedlings when subjected to different levels of NaCl, and the increases in V-ATPase activity in high-betacyanin seedlings were much higher than that in the control. No clear pattern was observed for NaCl-dependent activity changes of P-ATPase (plasma membrane H⁺-ATPase) and V-PPase (tonoplast H⁺-pyrophosphatase). Similar changes were demonstrated in leaf SOD activity and chloroplast SOD activity under salt stress. Both leaf SOD activity and chloroplast SOD activity were markedly enhanced with the increase of NaCl or with time, especially thylakoid-bound SOD activity. Furthermore, the increases in chloroplast SOD activity and thylakoid-bound SOD activity were much higher in high-betacyanin seedlings than that in the control at different levels of NaCl treatment. The higher V-ATPase activity, chloroplastic SOD activity, and thylakoid-bound SOD activity demonstrated in high-betacyanin seedlings, but lower in the control, suggest that high-betacyanin S. salsa seedlings may have higher potential to be energized by the electrochemical gradient for ion uptake into the vacuole and to scavenge O₂^−• in situ produced in the chloroplasts, which may lead to higher salt tolerance than the control under salt stress. Thus, betacyanin may be involved in salt tolerance of S. salsa.     

Effect of NaCl and Polyamines on Plasma Membrane Lipids of Wheat Roots

Caryopses of a salt sensitive wheat cultivar (Triticum aestivum L. cv. Giza 163) were presoaked in 2.5 mM putrescine (Put), 5 mM spermidine (Spd) or 2.5 mM spermine (Spm) for 24 h and then subjected to 150 mM NaCl added to the growth medium for 15 d. Effects of NaCl and polyamines (PAs) on plasma membrane (PM) lipids, phospholipids, fatty acids, and free sterols were determined. NaCl treatment caused a decrease in total phospholipids, increase in saturated fatty acids and altered distribution of sterols and phospholipids. NaCl also induced increase in sterol/phospholipid ratio. PAs treatments (particularly Put and Spd) counterbalanced the NaCl deleterious effects on PM lipids.     

Establishment of Salt Stress Tolerant Rice Plants Through Step Up NaCl Treatment In Vitro

Establishment of salt tolerant rice plants was examined by single step or step up NaCl treatments of shoot bud clumps in vitro, and variation among in vitro salt tolerant plants were examined by rapid amplified polymorphic DNA (RAPD). Shoot bud clumps were necrotic, stubbed or dead when subjected to single step treatment with 1.5 or 2.0 % NaCl. Conversely all the clumps could grow vigorously when subjected to step up salt treatment with 0.5, 1.0, 1.5 and 2.0 % NaCl at 3 week intervals and 2 % NaCl tolerant plants were established. RAPD revealed shoot bud clumps with and without different NaCl treatments, seedlings from field and grown in vitro, and regenerants from callus were genetically close to one another. Conversely, callus cultures were genetically isolated. Growth under different salt stress conditions was not correlated with the genetic variation, suggesting that 2.0 % NaCl tolerant plants might not result from genetic mutation but were due to adaptation of plants by step up NaCl treatment in vitro.     

A Salt-Tolerant Cultivar of Wheat Maintains Photosynthetic Activity by Suppressing Sodium Uptake

The effects of NaCl treatment on the photosynthetic machinery in wheat (Triticum aestivum L.) cultivars differing in salt tolerance were investigated by comparison with iso-osmotic PEG treatment. Both cultivars similarly reduced the photosystem 2 (PS2) energy conversion efficiency (_PS2) rapidly when plants were exposed to a 100 mM NaCl solution, though no decline was detected under the iso-osmotic PEG treatment. There was no correlation between the reduction of the leaf relative water content (RWC) and the _PS2 in the two iso-osmotic stress treatments. In contrast, a decline of _PS2 along with the increase of the leaf sodium content above 4 % dry matter was detected under the NaCl treatment, while no such correlation was detected with other cations. The recovery of _PS2 after photoinhibitory irradiation was repressed by the NaCl treatment as the increase of the duration of the treatment. Norin 61 subjected to the 100 mM NaCl treatment for 10 d showed a decline of the _PS2 after 1 h moderate irradiation of 400 mol m^–2 s^–1 PPFD. Thus the concentrated Na⁺ within a leaf under salinity treatments may decrease the stability of PS2 functions and lead to photochemical inactivation.     

Role of the Polysaccharide Components of Azospirillum brasilense Capsules in Bacterial Adsorption on Wheat Seedling Roots

Azospirillum brasilense cells deprived of capsular exopolysaccharides completely lost their ability to bind wheat germ agglutinin (WGA) and much of their ability to attach to wheat seedling roots. The decapsulation of bacterial cells by washing them with a NaCl solution led to an increase in the relative hydrophobicity of the cell surface. The pretreatment of wheat seedling roots with N-acetyl-D-glucosamine (GlcNAc) or the GlcNAc-containing polysaccharide complexes stripped from Azospirillum cells reduced their attachment to the roots. Under the experimental conditions used (3-h incubation of wheat seedling roots with exponential-phase azospirilla), bacterial adsorption is mainly driven by the specific mechanisms attachment of the cells to the roots, whose operation is due to the capsular polysaccharide components and the WGA present on the wheat seedling roots.     

The cost of stress: Dry matter partitioning changes with seasonal supply of water and nitrogen to dryland wheat

Spring wheat cv. ‘Gutha’ was grown in continuous wheat (W/W) and narrow-leafed lupin (L. angustifolius L. cv. Yandee)-wheat (L/W) rotation on a yellow earth over mottled clay (Arenic Fragiudult) in a mediterranean climate for two years. The first year had a higher than average rainfall with adequate soil water until anthesis. The second year was very dry (only 232 mm total rainfall) and soil water contents were low throughout the growing season. Nitrogen fertilizer (+N) treatments were included in both years. In the first year an adjacent experiment compared the effects of loosening a pronounced traffic pan which existed on the site (LS)versus unloosened (US). In the first year roots contained more dry matter than tops in the early vegetative stage in all crops and then declined exponentially to a ratio of 0.1 in the US and LS treatments. In the second year however, the decline was both linear and much less, so that root:shoot ratios at harvest were still between 0.4 and 0.8. There was a consistent trend in root:shoot ratios from the most favourable (LS) to least favourable (W/W-N) treatments over the combined two years’ data, and this was also found in grain yield, with a higher yield in year one from the LS than US, and the lowest yield in year two from the W/W-N treatment. The proportion of total biomass recovered from below ground was substantially higher than is commonly reported from studies carried out in temperate, high fertility soils, but probably still under-estimates of the true amount of dry matter in roots because of inadequacies of sampling, washing and storage techniques. Root length densities were much greater in the drier year, especially in the surface 0.1-m, and based on theoretical considerations, much greater than required for extraction of available water. The effect of environmental conditions on the relative size of cereal crop carbon sinks are discussed in relation to these results.     

Zea mays L. amylacea from the Lluta Valley (Arica-Chile) tolerates salinity stress when high levels of boron are available

Elevated levels of boron occurring naturally in soil or irrigation waters are detrimental to many crops grown in agricultural regions of the world. If such levels of boron are accompanied by conditions of excessive salinity, as occurs in the Lluta valley in Northern Chile, the consequences can be drastic for crops. A variety of sweet corn from this valley (Zea mays L. amylacea) has arisen as a consequence of practiced seed selection, suggesting that it is extremely tolerant to high salt and boron levels. In the present study, seeds ofZea mays L. amylacea were collected in order to study their physiological mechanisms of tolerance to high levels of NaCl and boron. Concentrations of 100 and 430 mM NaCl and 20 and 40 mg kg⁻¹ boron were imposed as treatments. The plants did not exhibit symptoms of toxicity to either NaCl and boron during the 20 days of treatment. Na+ accumulation was substantial in roots, while boron was translocated to leaves. Boron alleviated the negative effect of salinity on tissue K+ and maintained membrane integrity. The higher values of water potential seem to be related to the capacity of this ecotype to maintain a better relative water content in leaves. Despite the fact that boron enhanced slightly the effect of salinity on CO₂ assimilation, no effect on photochemical parameters was observed in this ecotype. Osmotic adjustment allows this ecotype to survive in high saline soils; however the presence of boron makes this strategy unnecessary since boron contributed to the maintenance of cell wall elasticity.     

Effects of saline and osmotic stress on proline and sugar accumulation in Populus euphratica in vitro

The use of in vitro shoot cultures to evaluate osmotic and salt tolerance and the effects of salt and mannitol in the medium on proline and sugar accumulation were investigated in two poplar species, P. euphratica and P. alba cv. Pyramidalis × P. tomentosa. Shoot length, leaf number, whole plant dry weight, and the accumulation of proline and total soluble sugars in leaves were quantified after 2 weeks. All P. euphratica plantlets survived at all levels of mannitol and NaCl, while the mortality of P. alba cv. Pyramidalis × P. tomentosa increased both at the mannitol and the NaCl treatments. A significant increase in proline accumulation was observed in both young and mature P. euphratica leaves at 200 mM mannitol and above, and at 150 mM NaCl and above. The total soluble sugar content increased in young P. euphratica leaves at 250 mM NaCl; however, it decreased in the mature leaves. Similar increases of the total soluble sugar content were not seen in P. alba cv. Pyramidalis × P. tomentosa plants in response to either mannitol or NaCl treatment. Our results suggest that accumulated proline and sugars promote osmotic and salt tolerance. The effects of accumulated proline and total soluble sugars on leaves are discussed in relation to growth and osmotic adjustment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors influencing seed germination of Salsola affinis (Chenopodiaceae), a dominant annual halophyte inhabiting the deserts of Xinjiang, China

Salsola affinis is a dominant annual inhabiting saline deserts of Xinjiang, China. Experiments were conducted to determine the effects of temperature, winged perianths and NaCl on seed germination and on germination recovery from the effects of saline conditions after transfer to distilled water. Freshly harvested seeds could germinate equally well in light and darkness at 5–30 °C. Attached winged perianths significantly inhibited germination, removal enhanced germination. However, germination was not inhibited in the presence of detached winged perianths in any of the temperature treatments. We suggest that the winged perianth is a mechanical barrier for radicle emergence, not a barrier for water uptake; hence, it inhibited germination. Germination of seeds from which the perianth had been removed was not affected by NaCl at concentrations below 0.4 mol/l, but it was significantly decreased by NaCl at concentrations of 0.6–2.0 mol/l. No seeds germinated at 4.0 mol/l NaCl. Seeds incubated in NaCl at concentrations of 0.05–4.0 mol/l for 14 days recovered after being transferred to distilled water. However, germination was lower than that in the non-saline control, indicating that a portion of the NaCl-treated seeds may lose their ability to germinate.     

Spatial root distribution of apricot trees in different soil tillage practices

Root and soil water distribution was studied in a mature drip-irrigated apricot (Prunus armeniaca L. cv. Búlida) orchard with different soil tillage practices, in a loamy textured soil with a 7% slope, located in Murcia (SE Spain). Three treatments were applied between tree rows:control (no-tillage), whereby, following the common practice in the area, weeds were cut back to ground level by a blade attached to a tractor; perforated treatment, where the soil surface was mechanically perforated with an adapted-plough; and mini-catchment treatment, consisting of mini-catchments with low banks manually raised perpendicular to the line of emitters. Almost all of the apricot root system was located in the first 0.75 m of soil depth, with 91% in the first 0.50 m. More than 75% of the roots corresponded to thin roots, with a diameter less than 0.2 mm. Both tillage treatments decreased runoff compared with the control treatment, while the mini-catchment treatment showed the highest change in soil water content after rainfall events. The mini-catchment treatment was performed in an attempt to reduce the rainwater running down the slope, leaving the accumulated water near plant roots, an effect which was responsible for the higher root length density (RLD) values found in this treatment. In addition, roots were distributed over a wider area, providing higher RLD values up to 1 m from the emitter, meaning that a higher soil volume was explored. For these reasons, the mini-catchment treatment was seen to be the most beneficial soil tillage treatment for optimising water use in semiarid conditions.     

Comparison of selected washing treatments onAgrostis gigantea samples from mine tailings near Copper Cliff,Ontario, before analysis for Cu,Ni, Fe and K content

Summary Plants ofAgrostis gigantea Roth collected from Cu/Ni tailings near Copper Cliff, Ontario, were contaminated by substrate particles, and also on roots by an iron hydroxide plaque. Three washing treatments were compared on shoots and six on roots, prior to analysis for Cu, Ni and Fe. K content was compared to detect leaching. For both shoots and roots, rinsing with de-ionized water was as effective as Extran-300 or ultrasound. These three treatments caused no measured leaching from shoots. DCB removed iron plaque from roots; hot or cold EDTA removed some plaque. All treatments caused leaching of K from roots.     

盐胁迫对中国柽柳幼苗生理特性的影响

以中国柽柳(Tamarix chinensis Lour.)插穗为研究材料,在装有不同土壤盐分梯度(0.4%、0.8%、1.2%、1.6%、2.0%、2.4%)的盆钵中进行扦插试验,测定柽柳扦插成活率、叶绿素含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性及丙二醛(MDA)含量等指标,研究分析柽柳扦插成活率及幼苗生理特性对盐分胁迫的响应特征。结果表明:(1)柽柳扦插成活率随盐胁迫增强逐渐降低,适合扦插繁殖的土壤含盐量低于0.8%;土壤含盐量超过0.8%后,扦插成活率太低,不适合柽柳进行扦插繁殖。(2)柽柳可通过提高叶绿素含量来适应盐胁迫,随着盐胁迫增强,柽柳扦插幼苗叶片中叶绿素含量先升高后降低,但过高的盐胁迫会破坏叶绿素的合成。(3)柽柳扦插幼苗叶片SOD和POD活性随盐胁迫增强先升高后降低,通过提高SOD和POD活性来清除细胞内多余的活性氧自由基,但活性氧自由基积累过多时,膜脂过氧化作用会破坏细胞膜的稳定性,导致抗氧化酶活性降低。(4)柽柳扦插幼苗叶片MDA含量随盐胁迫的增强先升高后降低。在土壤含盐量0.4%—1.2%范围内,MDA含量虽高于CK,但各盐分处理之间差异不显著。在含盐量为1.6%时,叶片细胞受到膜脂过氧化作用加强,MDA含量显著升高,但含盐量为2.0%时,MDA含量降低。     

Effect of NaCl,water stress or both on gas exchange and growth of wheat

Responses of wheat (Triticum aestivum L.) to various concentrations of NaCl and levels of drought were followed. With the rise of NaCl or drought, or NaCl and drought together, growth was retarded. The water content of shoots and roots was mostly unchanged. The chlorophyll and carotenoid contents were increased in plants subjected to salinity or drought or both. Only high salinity level induced a considerable decrease in net photosynthetic rate (P_N) and dark respiration rate (R_D). P_N and R_D were decreased with the decrease of soil moisture content. The content of Na⁺ in the shoots and roots of wheat plants increased with increasing salinity or decreasing soil moisture content or both treatments. Considerable variations in the content of K⁺, Ca²⁺ or Mg²⁺ were induced by the NaCl, drought or both treatments.