Inter-population Variations of Kochia indica During Germination Under Different Stresses

Germination of three populations of Kochia indica Wight fromcontrasting soil types were studied under various levels ofsalinity, alkalinity and osmotic stress with a view to evaluatetheir potential to establish through seeds in saline and alkalineenvironments of various magnitudes. The seeds were germinatedunder controlled conditions in Petri dishes using salinizedsolutions of NaCl, Na₂SO₄, MgCl₂ and CaSO₄ (electrical conductivity,EC, 4–16 dsm¹), sodium carbonate solutions (pH 8.5ndash;10.0), mannitol solutions ( —2.5 to —10.0 bar) andde-ionised distilled water (control). Inter-population differenceswere very marked, showing selective adaptation of the populationsto a particular stress type. In general, all populations exhibitedsalt tolerance but were rather sensitive to high osmotic stress. Kochia indicaWight (bui), germination, populatio, salinity, alkalinity, osmotic stress     

Inter-population Variations of Kochia indica During Germination Under Different Stresses

Germination of three populations of Kochia indica Wight fromcontrasting soil types were studied under various levels ofsalinity, alkalinity and osmotic stress with a view to evaluatetheir potential to establish through seeds in saline and alkalineenvironments of various magnitudes. The seeds were germinatedunder controlled conditions in Petri dishes using salinizedsolutions of NaCl, Na₂SO₄, MgCI₂ and CaSO₄ (electrical conductivity,EC, 4–16 ds m^–), sodium carbonate solutions (pH8.5–100), mannitol solutions ( – 2.5 to –100 bar) and de-ionised distilled water (control). Inter-populationdifferences were very marked, showing selective adaptation ofthe populations to a particular stress type. In general, allpopulations exhibited salt tolerance but were rather sensitiveto high osmotic stress. Kochia indica Wight (bui), germination, population, salinity, alkalinity, osmotic stress     

Canola seed germination and seedling emergence from pre-hydrated and re-dried seeds subjected to salt and water stresses at low temperatures

Low soil temperatures and low water potentials reduce and delay the seed germination of canola (Brassica rapa L., B. napus L.) in western Canada. Germination is also very sensitive to the salinity effects of nitrogen fertiliser placed with the seed, especially when the seed bed is relatively dry. The effects of pre-hydration and re-drying treatment on canola (Brassica rapa L. cv. Tobin) seed germination and seedling emergence at 10°C subjected to either a water or salt stress were determined. Low water potentials, induced by polyethylene glycol (PEG 8000), low soil moisture, or high concentrations of salts, reduced both germination and seedling emergence, and increased the time to 50% germination and emergence of seeds at 10°C. At equal osmotic potentials, Na₂SO₄ was less inhibitory on low temperature germination than either NaCl or PEG, suggesting that the sulphate ion partially alleviated the inhibitory effects of low water potential. Solutions of NaCI produced more abnormal seedlings compared to Na₂SO₄, suggesting that NaCl was more toxic than Na₂SO₄ during seedling development. Pre-hydration and re-drying partially overcame the inhibitory effects of both low water potential and salts on seed germination and seedling emergence at 10°C. The seed treatment increased the germination rate in Petri dishes and seedling emergence from a sandy loam soil. Water potentials or soil water contents required to inhibit 50% germination or emergence at 10°C were lower for treated seeds compared to control seeds. Salt concentrations inhibiting 50% emergence were higher for treated seeds than control seeds. Neither treated nor control seeds produced seedlings which emerged if the soil water content was lower than 9% or when the soil was continuously irrigated with salt solutions of 100 mmol kg^-1 of NaCl or 50 mmol kg^-1 of Na₂SO₄. These results suggest that the pre-hydration and re-drying treatment did not lower the base water potentials at which seedling emergence could occur. Abnormal seedlings were observed in both treated and control seeds, particularly if the soil was watered with NaCl solutions; however, the seed treatment reduced the number of abnormal seedlings.     

Changes in germination and glyoxylate and respiratory enzymes of Pinus pinea seeds under various abiotic stresses

Abstract

This study examined Pinus pinea seeds for their tolerance to osmotic potentials of ?0.30MPa (10% polyethylene glycol [PEG]), ?0.58MPa (18% PEG), ?0.80MPa (21% PEG), ?1.05MPa (24% PEG), pH values of 4, 5, 6, 7, 8, 9, 10, and different calcareous solutions (5, 10, 20 and 40% CaCO₃). The main enzymes of glyoxylate cycle and respiratory pathway were tested. Pinus pinea seeds under no stressful condition (Control) and 5% CaCO₃ reached 100% of germination. Higher concentrations of CaCO₃ (20, 40%) and lower pH (4–5) adversely affected seed germination percentage, glyoxylic and respiratory enzyme activities. PEG caused the most detrimental effects on Pinus seeds; increasing the osmotic potential the germination was completely inhibited. These results suggest that Pinus pinea is able to germinate in calcareous and alkaline soils rather than in soils with lower water availability and acidic conditions.     

Effect of salt and osmotic stresses on germination in durum wheat (Triticum durum Desf.)

In order to determine the relative importance of ionic toxicity versus the osmotic component of salt stress on germination in durum wheat (Triticum durum Desf.), seeds of three cultivars differing in their salt and drought resistance (Omrabi-5, drought-resistant; Belikh, salt-resistant and Cando, salt-sensitive) were incubated in various iso-osmotic solutions of NaCl, mannitol and polyethylene-glycol (PEG) (osmotic potential of –0.15 (control solution) –0.58, –1.05 or –1.57 MPa). Moderate stress intensities only delayed germination, whereas the highest concentration of NaCl and PEG reduced final germination percentages. PEG was the most detrimental solute, while mannitol had no effect on final germination percentages. All osmotica reduced endosperm starch and soluble sugars content as well as -amylase activities recorded after 48 h of treatment while -amylase activities were, in contrast, slightly stimulated in all cultivars. Deleterious effects of NaCl and PEG were higher on isolated embryos germinated onto an in vitro Linsmaier and Skoog (LS) medium comparatively to whole seeds. All PEG-treated embryos, however, recovered after the stress relief while NaCl-treated embryos exhibited a lower rate of recovery and some extent of abnormal germination after rinsing. It was concluded that stress inhibition of germination could not be attributed to an inhibition of mobilisation of reserves and that the main effect of PEG occurred via an inhibition of water uptake while detrimental effects of NaCl may be linked to long-term effects of accumulated toxic ions. The behaviour of the three cultivars during germination did not fully reflect their mean level of putative stress resistance in field conditions and germination is, therefore, not recommended as a reliable selection criterion for breeding purposes.     

Hydrogen sulfide promotes wheat seed germination under osmotic stress

Effects of NaHS, H₂S donor, on germination and antioxidant metabolism in wheat (Triticum aestivum L.) seeds under osmotic stress were investigated. With the enhancement of osmotic stress, which was mimicked by PEG-6000, the seed germination dropped gradually. NaHS treatment could promote wheat seed germination against osmotic stress in a dose-dependent manner; while Na⁺ and other sulfur-containing components, such as S²⁻, SO₄²⁻, SO₃²⁻, HSO₄⁻ and HSO₃⁻, were not able to improve seed germination as NaHS did, confirming H₂S or HS⁻ derived from NaHS contribute to the protective roles. Further experiments showed that NaHS treatment combined with PEG enhanced the activities of amylase and esterase in comparison to PEG treatment alone. Alternatively, NaHS treatment significantly reduced malondialdehyde and hydrogen peroxide accumulation in seeds. Significant enhancement of catalase and ascorbate peroxidase activities and decrease in lipoxygenase activity were observed in NaHS treated seeds, while peroxidase and superoxide dismutase activities were not affected as compared with the control. Furthermore, the H₂S donor treatment could retain higher levels of endogenous H₂S in wheat seeds under osmotic stress. These data indicated that H₂S played a protective role in wheat seed against osmotic stress.     

The Effect of Different Salts of Sodium and Potassium on the Accumulation of Glycinebetaine in Atriplex Prostrata

Atriplex prostrata was grown for one month in nutrient solutions with NaCl, KCl, Na₂SO₄, and K₂SO₄ (at osmotic potentials of 0, –0.75, –1.00, and –1.50 MPa). Plants treated with K₂SO₄ had less glycinebetaine at –1.0 and –1.50 MPa than those treated with Na⁺ salts, probably due to the inhibitory effects of K⁺ on glycinebetaine accumulation.     

NaCl和Na2CO3胁迫对栓皮栎种子萌发及幼苗生长的影响

为了阐明栓皮栎种子萌发期对盐碱胁迫的耐受性,研究了不同浓度(0、50、100、200和400 mmol/L)NaCl和Na2CO3胁迫对其种子萌发、生长、保护酶活性和有机渗透调节物质等的影响,结果表明:(1)盐碱胁迫对栓皮栎种子的萌发率和发芽指数均没有显著影响;随着Na+浓度的升高,NaCl和Na2CO3处理下的胚根长度、胚根生长速率、胚根鲜重均受到抑制,呈现下降趋势;活力指数和耐盐指数在NaCl胁迫下表现为较低浓度(50 mmol/L)促进,较高浓度(100,200,400 mmol/L)抑制,而在Na2CO3处理下则不断下降;相对盐害率在两种处理下均表现波动趋势。(2)通过建立活力指数、胚根长度等与Na+浓度的回归方程,发现在NaCl胁迫下栓皮栎种子活力指数、胚根鲜重、胚根长度和胚根生长速率的临界值分别为300.0、300.0、333.6、369.6 mmol/L。(3)在NaCl和Na2CO3胁迫下,随Na+浓度的增加,丙二醛含量增幅显著;NaCl处理下的SOD(superoxide dismutase)活性呈现先升高后降低的趋势,而Na2CO3处理下则均低于对照;POD(peroxidase)活性变化不显著;CAT(catalase)活性均表现为先降低后升高;脯氨酸、可溶性蛋白和可溶性糖含量均随着Na+浓度的升高而呈现不同程度上升趋势。(4)等Na+浓度时,NaCl处理下的各项生长指标均高于Na2CO3处理,丙二醛、保护酶活性及渗透调节物质含量均低于Na2CO3处理,说明Na2CO3对栓皮栎种子的影响比NaCl更为显著。     

Effects of various salt-alkaline mixed stresses on Aneurolepidium chinense (Trin.) Kitag.

The stress conditions of salt-alkalinized soil were simulated to investigate the features and acting factors of salt-alkaline mixed stress, using a natural salt-alkaline tolerant grass Aneurolepidium chinense (Trin.) Kitag. According to the features of salt-alkalinized soil in the northeast of China, various salt-alkali conditions with different salinities and pHs were established by mixing NaCl, NaHCO₃, Na₂SO₄, and Na₂CO₃, in various proportions. The treatments included a salt concentration range of 50 to 350 mM and pH values from 7.14 to 10.81. Seedlings of A. chinense were stressed under these salt-alkali conditions. Several physiological indices of seedling stress were determined, including survival rate, tillering rate, number of rhizomes, relative growth rate (RGR), proline content, electrolyte leakage rate, and Na⁺ and K⁺ content, in order to analyze the characteristics of the stresses due to the salt-alkali mixes and their main stress factors.The results showed that the survival rate, tillering rate, number of rhizomes, RGR, and K⁺ content of A. chinense decreased with increasing salinity and pH (or alkalinity). Proline and Na⁺ content and electrolyte leakage rate increased with increasing salinity and pH (or alkalinity). The deleterious effects of a high pH value or salinity alone were significantly less than those of high pH in combination with salinity. This result suggested that for a salt-alkaline mixed stress, a reciprocal enhancement between salt stress and alkali stress was a characteristic feature, and it was most evidently reflected in the survival rate. When salinity was below 125 mM or pH was below 8.8, survival rates were all 100%. However, when salinity was above 125 mM and pH was above 8.8, survival rates sharply declined with the increasing of either salinity or pH.The buffer capacity of the treatment solution was taken as a stress factor in order to simplify the stress factor analysis. The results of the statistical analysis showed that for the stress factors of the salt-alkaline mixed stress, [CO₃^2–] and [HCO₃^–] could be fully represented by the buffer capacity, and [Na⁺] could be fully represented by salinity, whereas [SO₄^2–] was negligible. Therefore, four factors, salinity, buffer capacity, pH and [Cl^–], could reflect all of the stress factors. Perfect linear correlations were observed between all physiological indices and four or three stress factors by a stepwise regression analysis. However, the effects of the four stress factors on the physiological indices were significantly different in magnitude. Buffer capacity and salinity were dominant factors for all physiological indices. Thus, it is reasonable to consider the sum of salinity plus buffer capacity as the strength value of salt-alkaline mixed stress. Furthermore, the relationships between different physiological indices and various stress factors were shown to be different.     

Effects of various mixed salt-alkaline stresses on growth,photosynthesis, and photosynthetic pigment concentrations of <Emphasis Type="Italic">Medicago ruthenica</Emphasis> seedlings

Soil salinization and alkalinization frequently co-occur in naturally saline and alkaline soils. To understand the characteristics of mixed salt-alkali stress and adaptive response of Medicago ruthenica seedlings to salt-alkali stress, water content of shoots, growth and photosynthetic characteristics of seedlings under 30 salt-alkaline combinations (salinity 24–120 mM and pH 7.03–10.32) with mixed salts (NaCl, Na₂SO₄, NaHCO₃, and Na₂CO₃) were examined. The indices were significantly affected by both salinity and pH. The interactive effects between salt and alkali stresses were significant, except for photosynthetic pigments. Water content of shoots, relative growth rates of shoots and roots and pigment concentrations showed decreasing trends with increasing salinity and alkalinity. The root activity under high alkalinity and salinity treatments gradually decreased, but was stimulated by the combined effects of low alkalinity and salinity. The survival rate decreased with increased salinity, except at pH 7.03–7.26 when all plants survived. Net photosynthetic rate, stomatal conductance and intercellular CO₂ concentration decreased with increased salinity and pH. M. ruthenica tolerated the stress of high salt concentration when alkali concentration was low, and the synergistic effects of high alkali and high salt concentrations lead to the death of some or all seedlings. M. ruthenica appeared to be saltalkali tolerant. Reducing the salt concentration or pH based on the salt components in the soil may be helpful to abate damage from mixed salt-alkaline stress.     

High Salt and High pH Tolerance of New Isolated Rhizobium etli Strains from Egyptian Soils

Saline and alkaline soils are major problems contributing to the low productivity of common bean (Phaseolus vulgaris) in arid and semi-arid regions such as Egypt. Therefore our study was directed toward selecting strains more tolerant to these environmental stresses. Among seven Rhizobium etli strains isolated from Egyptian soils, we found a high degree of diversity. Strains EBRI 21 and EBRI 26 are highly tolerant to a salt concentration up to 4% NaCl. A positive correlation was found between the salt tolerance and the adaptation to alkaline pH (9). Strains EBRI 2 and EBRI 26 were adapted to elevated temperatures (42°C). The minimum level of low pH for the majority of Rhizobium etli strains from Egypt was pH 4.7 while the Colombian strain Rhizobium tropici CIAT 899 survived well at pH 4. At 0.4% NaCl, the symbiotic efficiency of the salt-tolerant strain EBRI 26 was superior in cultivar Giza 6 compared with the salt-sensitive strain EBRI 2 (18.2 compared with 13.9 nM C₂H₄ h^–1 mg^–1 nodule fresh weight). In the bean cultivar Saxa, nitrogen fixation was much more affected by high salt concentration (0.4% NaCl) than in the cultivar Giza 6 with both strains (3.9 and 3.8 nM C₂H₄ h^–1 mg^–1 nodule fresh weight, respectively). In general, stress of alkalinity had a less detrimental effect on nodulation and N₂ fixation than stress of salinity.     

Seed germination of Pilosocereus arrabidae (Cactaceae) from a semiarid region of south‐east Brazil

We evaluated the effect of temperature regimes (six constant and four alternating temperatures), light qualities (five red : far red ratios) and water potentials (ΨW; seven NaCl and polyethylene glycol 6000 [PEG] solutions) on the percentage and germination rate, as well as the post‐seminal development morphology, that allow Pilosocereus arrabidae seeds to germinate in a hot semiarid climate on the south‐eastern Brazilian coast. The results showed that seeds germinated similarly between constant and alternating temperatures, with an optimal germination at 25/20°C and 20°C. Pilosocereus arrabidae seeds were photoblastic positive and the final germination percentage was inhibited at low red : far red ratios. Maximum germination was obtained in distilled water (0 MPa) and decreases of Ψ_W in the solutions reduced the germination, which was lower in NaCl than in iso‐osmotic PEG solutions. Germination inhibition appears to be osmotic because the recovery response was high when non‐germinated seeds from both iso‐osmotic solutions were transferred to water. Seeds of P. arrabidae are small and germination is phaneroepigeal. Despite the slow growth typically seen in seedlings and adults of Cactaceae, germination in this species depends on the ability of the seeds to appropriately sense and react to environmental cues that correlate with times and places under low‐risk growth conditions.     

Effects of mucilage on seed germination of the desert ephemeral plant Plantago minuta Pall. under osmotic stress and cycles of wet and dry conditions

To test the role of the seed mucilage of Plantago minuta Pall. in regulating germination under osmotic stress and cycles of hydration and dehydration, two experiments were carried out using seeds with intact mucilage and mucilage‐free seeds. In Experiment 1 seeds were immersed in a range of iso‐osmotic polyethylene glycol solutions (?1.15 to 0 MPa) for 14 days; any ungerminated seeds were transferred to deionized water to investigate the recovery germination. In Experiment 2 seeds were immersed in deionized water for 24 h, and were then incubated on filter paper for an additional 13 days to ensure complete desiccation before reimbibition to test the germination recovery percentage. Under mild osmotic stress (?0.73 to 0 MPa), the intact seeds with mucilage were shown to have higher germination rates than the mucilage‐free seeds, indicating that the mucilage led to a “fast sprouting” germination strategy under mild osmotic stress. However, when seeds were exposed to high osmotic stress (?1.15 MPa), the mucilage apparently slowed the germination rate, resulting in a “risk‐balancing” germination strategy. Extreme drought induced by polyethylene glycol solution and the desiccation pretreatment accelerated germination rates compared to non‐pretreated seeds; both germination potential and recovery percentage of the mucilage seeds were significantly higher than that of the mucilage‐free seeds. Our results revealed that the seed mucilage of P. minuta plays a crucial role in regulating seed germination rates and the germination strategies adopted by controlling seed water absorption when the seeds experience different osmotic stresses or alternating wet and dry conditions.     

沙地云杉和青海云杉种子萌发和幼苗生长对干旱盐碱胁迫的响应

利用控制实验研究了水分、盐分生态因子对沙地云杉和青海云杉种子萌发和幼苗生长的影响,以探索沙地云杉和青海云杉种子对水分、盐分生态因子的适应性。结果表明:(1)水分胁迫和盐分胁迫对沙地云杉和青海云杉种子萌发具有明显的抑制作用,可显著的降低种子的发芽率,两种云杉种子对水分胁迫的临界值和极限值分别是-0.03、-0.15 MPa和-0.5、-0.58 MPa;对盐分胁迫的临界值和极限值分别是78、148 mmol/L和284、345mmol/L;其幼苗长度随着渗透势和NaCl浓度的增加而显著减小。(2)沙地云杉和青海云杉种子恢复发芽率及恢复后的幼苗长度随着渗透势和NaCl浓度的增加先增加后减少。(3)在相同的水势条件下,PEG溶液比等渗的NaCl溶液对沙地云杉和青海云杉种子萌发具有更大的抑制作用,种子萌发过程中渗透胁迫比离子毒害的抑制作用更大。研究发现,沙地云杉和青海云杉种子对水分和盐分胁迫表现出不同程度的耐受性,两者对盐分胁迫的忍耐能力超过对水分胁迫;而且青海云杉种子比沙地云杉更耐旱、耐盐;早期的低盐和充分的水分条件是沙地云杉和青海云杉存活的关键。     

Responses of dormant heather (Calluna vulgaris) seeds to light, temperature, chemical and advancement treatments

Two seed lots of Calluna vulgaris were obtainedfrom English Nature (seed of Cornish provenance) (EN) and John ChambersWildflower Seeds (JCWS). In laboratory tests, under continuous light untreatedseeds of both seed lots were partially dormant at temperatures between14–35 °C, but JCWS seeds were more deeply dormant thanENseeds. The optimum temperature for germination for both lots was ca 18°C. Germination of EN seeds was much lower in the dark than inthe light at all temperatures; JCWS seeds did not germinate in the dark. In thelight at 22 °C, dormancy of both seed lots was broken whenseeds were incubated in GA_4/7 solution(2×10^–4 M). Dormancy ofJCWSseeds at 22 °C in the light was broken when seeds wereincubated in four different smoke solutions but more so when used incombinationwith GA_4/7. Soaking seeds for 4h insmoke/GA_4/7solutions before sowing improved both the speed andpercentage germination in pot experiments on a mist bench in the glasshouse byat least 10-fold. Soaking with GA_4/7 alone produced a 5-fold increasein germination but seedlings were more etiolated than with thesmoke/GA_4/7 mixtures. A seed advancement treatment modified from thatused commercially on sugar beet seeds also promoted germination in bothlaboratory and glasshouse tests. This entailed soaking seeds in 0.2% thiramsuspension for 4h followed by incubation in excess solution at 22°C for 4 days. This treatment was not as effective as thesmoke/GA_4/7 seed soaks.     

Abscisinsäure und Keimungshemmung in der Tomatenfrucht

Summary The germination inhibiting effect of the juice from ripe tomato fruit tissue surrounding the seeds was analysed. The most important factor seem to be osmotic substances contained in the sap. Isotonic solutions of sucrose, glucose and Na₂SO₄ inhibit germination of tomato seeds completely. The osmotic inhibition is increased by a ether soluble acid germination inhibitor (Blastokolin according to Köckemann, 1934), which was identified as abscisic acid (ABA). ABA alone cannot be responsible for the inhibition of germination, since concentrations of synthetic racemic ABA corresponding to the natural concentration of ABA in the fruit flesh have only a slight inhibitory effect in vitro. Moreover, volatile germination inhibitors are present, but their exact importance and chemical nature was not analysed. The results are discussed in the light of earlier papers concerning the problem of germination inhibition in fruits.     

Water relations and xylem transport of nutrients in pepper plants grown under two different salts stress regimes

Two iso-osmotic concentrations of NaCl and Na₂SO₄ were used for discriminating between the effects of specific ion toxicities of salt stress on pepper plants (Capsicum annuum L.) grown in hydroponic conditions, in a controlled-environment greenhouse. The two salts were applied to plants at different electrical conductivities, and leaf water relations, osmotic adjustment and root hydraulic conductance were measured. Leaf water potential (_w), leaf osmotic potential (_o) and leaf turgor potential (_p) decreased significantly when EC increased, but the decrease was less for NaCl- than for Na₂SO₄-treated plants. The reduction in stomatal conductance was higher for NaCl-treated plants. There were no differences in the effect of both treatments on the osmotic adjustment, and a reduction in root hydraulic conductance and the flux of solutes into the xylem was observed, except for the saline ions (Na⁺, Cl^– and SO₄ ^2–). Therefore, pepper growth decreased with increasing salinity because the plants were unable to adjust osmotically or because of the toxic effects of Cl^–, SO₄ ^2– and/or Na⁺. However, turgor of NaCl-treated plants was maintained at low EC (3 and 4 dS m^–1) probably due to the maintenance of water transport into the plant (decrease of stomatal conductance), which, together with the lower concentration of Na⁺ in the plant tissues compared with the Na₂SO₄ treatment, could be the cause of the smaller decrease in growth.     

Physical and physiological dormancy in black henbane (<Emphasis Type="Italic">Hyoscyamus niger</Emphasis> L.) seeds

Aim of this study was to investigate the nature of dormancy in black henbane (Hyoscyamus niger) seeds which have low germination rate under normal laboratory conditions. To do this, before placing the seeds in Petri dishes, they were soaked in 5,10 and 15 mg/L GA; 1,2 and 3% H₂SO₄, 15 mg/L GA + 1% H₂SO₄, 0.01 M KNO₃ solutions, tap water, 40, 50 and 60°C hot water for 30 min. The study was performed under both continuous illumination and darkness in growth chambers to evaluate the effect of light on germination rate. The results showed that H₂SO₄ and GA treatments were the most important factors affecting seed germination and their germination enhancing effects were more evident in darkness. The results also suggested that black henbane seeds exhibit double dormancy involving a hard seed coat and a partially dormant embryo and have a partial dark requirement to germinate.     

<Emphasis Type="Italic">Thialkalivibrio halophilus</Emphasis> sp. nov., a novel obligately chemolithoautotrophic,facultatively alkaliphilic,and extremely salt-tolerant,sulfur-oxidizing bacterium from a hypersaline alkaline lake

A new chemolithoautotrophic, facultatively alkaliphilic, extremely salt-tolerant, sulfur-oxidizing bacterium was isolated from an alkaline hypersaline lake in the Altai Steppe (Siberia, Russia). According to 16S rDNA analysis and DNA–DNA hybridization, strain HL 17^T was identified as a new species of the genus Thialkalivibrio belonging to the subdivision of the Proteobacteria for which the name Thialkalivibrio halophilus is proposed. Strain HL 17^T is an extremely salt-tolerant bacterium growing at sodium concentrations between 0.2 and 5 M, with an optimum of 2 M Na⁺. It grew at high concentrations of NaCl and of Na₂CO₃/NaHCO₃ (soda). Strain HL 17^T is a facultative alkaliphile growing at pH range 7.5–9.8, with a broad optimum between pH 8.0 and 9.0. It used reduced inorganic sulfur compounds (thiosulfate, sulfide, polysulfide, elemental sulfur, and tetrathionate) as energy sources and electron donors. In continuous culture under energy limitation, thiosulfate was stoichiometrically oxidized to sulfate. In sodium carbonate medium under alkaline conditions, the maximum growth rate was similar, while the biomass yield was lower as compared with the NaCl-grown culture. The maximum sulfur-oxidizing capacity measured in washed cells was higher in the soda buffer independent of the growth conditions. The compatible solute content of the biomass was higher in the sodium chloride-grown culture than in the sodium carbonate/bicarbonate-grown culture. The data suggest that the osmotic pressure differences between soda and NaCl solutions might be responsible for the difference observed in compatible solutes production. This may have important implications in overall energetic metabolism of high salt adaptation.     

Influence of calcium pretreatment on wheat germination on saline media

Summary Wheat grains (Triticum vulgare L. var. Lemhi 53) were pretreated for about 6 hours with various solutions. They were then rinsed and planted on filter paper moistened with NaCl solution in petri dishes. Percent germination was measured after 3 days. Germination of water pretreated seeds on 1% NaCl was 8 per cent, while pretreatment with 1% CaCl₂. 2H₂O resulted in 90 per cent germination on 1% NaCl. Pretreatment with sodium and potassium chlorides enhanced germination only slightly. The beneficial effects of calcium pretreatment could be duplicated only partially by increments of CaCl₂ to the NaCl germination medium. Preatreatment concentrations ranging from 1 to 5% CaCl₂. 2H₂O, and times ranging from 3 to 24 hours were about equally effective. The beneficial effect of pretreatment persisted even though the seeds were subsequently dried and planted several months later. Pretreatment with calcium resulted in about a 25 per cent reduction in Na²² uptake from the germination medium.United Nations F.A.O. André Meyer Post Doctoral Research Fellow, on leave from Sind University, Hyderabad, West Pakistan.