Numbers of iron‐oxidizing bacteria and oxidation potential of sulfur and iron components in coal refuse amended with limestone and sewage sludge

Counts of acidophilic iron‐oxidizing bacteria, ratios of S₂O₃=—S/SO₄=—S and Fe⁺³/Fe⁺², and S₂O₃=—S oxidation potentials were examined over a two‐year period in coal refuse (acid gob) treated with limestone and/or sewage sludge. A non‐amended treatment was used as a control.

No significant difference in population counts of acidophilic iron‐oxidizing bacteria were observed between treatments in either year of the study. S₂O₃=—S/SO₄=—S and Fe⁺³/Fe⁺² ratios indicated active sulfur and iron oxidation suggesting that limestone and/or sewage sludge may be ineffective in suppressing pyrite oxidation. Under optimal conditions, S₂O₃=—S oxidation potentials (in vitro) showed a logarithmic increase in SO₄=—S formation for all four treatments over time. The final pH of the treatments following twenty days of perfusion ranged from 3.06 to 3.59.     

Some morphogenic effects of sodium sulfate on tobacco callus

Callus cultures of Nicotiana tabacum L cv. Wisconsin 38 were initiated and grown on shoot-forming (SF) and callus proliferation (CP) medium with or without Na₂SO₄. Two cultures were maintained on SF medium with 0, 0.75, 1 or 1.5% Na₂SO₄ for 2.5 and 3.5 years. In the older culture only callus grown on salt formed shoots throughout the maintenance period, while in the younger culture the control responded best and Na₂SO₄ was inhibitory. Callus from the older culture which had been grown on salt continued to form shoots in the absence of salt. Na₂SO₄ caused adventitious shoot formation in three cultures on CP medium. These shoots were present for 7 subcultures after removal of Na₂SO₄; but established, control callus, did not form shoots when transferred to Na₂SO₄. Callus initiated and maintained on NaCl or mannitol showed a slight increase in shoot initiation. On NaCl, Na₂SO₄ or mannitol, the tissue osmotic potential became more negative and proline concentration increased.     

Formation and role of glycine betaine in the moderate halophile Vibrio costicola

The moderate halophile Vibrio costicola, growing on a chemically-defined medium, transformed choline into glycine betaine (betaine) by the membrane-bound enzyme choline dehydrogenase and the cytoplasmic enzyme betainal (betaine aldehyde) dehydrogenase. Choline dehydrogenase was strongly induced and betainal dehydrogenase less strongly induced by choline. The formation of these enzymes was also regulated by the NaCl concentration of the growth medium, increasing with increasing NaCl concentrations. Intracellular betaine concentrations also increased with increasing choline and NaCl concentrations in the medium. This increase was almost completely blocked by chloramphenicol, which does not block the increase in salt-tolerant active transport on transfer from a low to a high salt concentration.Choline dehydrogenase was inhibited by chloride salts of Na⁺, K⁺, and NH _inf4 ^su+ , the inhibition being due to the Cl^- ions. Betainal dehydrogenase was stimulated by 0.5 M salts and could function in up to 2.0 M salts.Cells grew as well in the presence as in the absence of choline in 0.5 M and 1.0 M NaCl, but formed no intracellular betaine. Choline stimulated growth in 2.0 M NaCl and was essential for growth in 3.0 M NaCl. Thus, while betaine is important for some of the adaptations to high salt concentration by V. costicola, it by no means accounts for all of them.Abbreviations CDMM chemically-defined minimal medium - PPT proteose-peptone tryptone medium - SDS sodium dodecyl sulfate Deceased, 1987     

Sulfur Transformation in Microbially Mediated Pyrite Oxidation by Acidithiobacillus ferrooxidans: Insights From X-ray Photoelectron Spectroscopy-Based Quantitative Depth Profiling

The oxidation of pyrite and other sulfides is responsible for the generation of acid mine drainage and acid rock drainage, which leads to further contamination of soil and water. In these processes, microbial oxidation usually prevails over chemical oxidation. To determine the mechanism of microbial oxidation of pyrite, the interaction of Acidithiobacillus ferrooxidans with pyrite was comprehensively studied, and the sulfur transformation in the interaction was disclosed using X-ray photoelectron spectroscopy (XPS) depth profiling. Abundant bacterial cells attach to pyrite surface and form biofilms, which greatly enhances surface corrosion and results in two types of etching pits: bacteria-driven rod-shaped and chemically driven hexagonal etching pits. The details of XPS depth profiles on a reacted pyrite surface reveal that the surface sulfur was first oxidized into elemental sulfur. Thereafter, elemental sulfur was further oxidized to intermediate species S₂O₃^2?, SO₃^2?, and ultimately to SO₄^2?. The oxidation sequence of sulfur is S₂^2?/S^2?→S_n^2?, S⁰→SO₃^2?, and S₂O₃^2?→SO₄^2?. Meanwhile, the remnant ferrous iron in the surface layer was released into solution and subsequently oxidized into Fe³⁺ by A. ferrooxidans and dissolved oxygen, which in turn enhanced the oxidation of sulfur. Fe³⁺, sulfate, and other ions (e.g., K⁺, Na⁺, NH₄⁺) in the solution precipitated as jarosite, hydroniumjarosite, and ammoniojarosite. On the basis of results, a three-staged model is proposed to interpret the kinetics of microbial oxidation of pyrite.     

Anaerobic degradation of betaine by marine Desulfobacterium strains

From enrichment cultures with betaine (20 mM) and sulfate (20 mM) as the substrates and intertidal mud as an inoculum, a betaine-oxidizing, sulfate-reducing bacterium (strain PM4) was isolated. Strain PM4 was an oval to rod-shaped, Gram-negative, motile bacterium, which was able to oxidize lactate completely to CO₂ and contained, during growth on betaine and sulfate, high activities of key enzymes of the acetyl CoA/CO dehydrogenase pathway (carbon monoxide dehydrogenase and formate dehydrogenase), but not of 2-oxo-glutarate dehydrogenase, a key enzyme of the citric acid cycle. On the basis of its morphological and physiological characteristics, strain PM4 was identified as a Desulfobacterium strain. Desulfobacterium PM4 grew on betaine with a doubling time of approximately 20 h at 30°C and produced N, N-dimethylglycine (in a 1:1 ratio) and sulfide as products. In this type of betaine metabolism one of the methyl groups of betaine is oxidized to CO₂ and the reducing equivalents generated are used for the reduction of sulfate. Desulfobacterium autotrophicum (DSM 3382) grew also on betaine and sulfate with the formation of N,N-dimethylglycine, sulfide and CO₂.     

Changes in the levels of jasmonates and free polyamines induced by Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> and NaCl in roots and leaves of the halophyte <Emphasis Type="Italic">Prosopis strombulifera</Emphasis>

Prosopis strombulifera, a common legume in high-salinity soils of Argentina, is a useful model for elucidation of salt tolerance mechanisms and specific biochemical pathways in halophytes, since its NaCl tolerance exceeds the limit described for most halophytic plants. We analyzed the effects of the increasing concentration of two main soil salts, Na₂SO₄ and NaCl, on growth parameters of P. strombulifera, chlorophyll levels, and content of jasmonates (JAs) and polyamines (PAs), which are key molecules involved in stress responses. P. strombulifera showed a halophytic response (growth promotion) to NaCl, but strong growth inhibition by iso-osmotic solutions of Na₂SO₄. Chlorophyll levels, number of leaves and leaf area were also differentially affected. An important finding was the partial alleviation of SO₄²⁻ toxicity by treatment with two-salt mixture. JAs are not directly involved in salt tolerance in this species since its levels decrease under all salt treatments. Beneficial effects of Putrescine (Put) accumulation in NaCl treated plants maybe inferred probably associated with the antioxidative defense system. Another novel finding is the accumulation of the uncommon PA cadaverine in roots under high Na₂SO₄, which may be related to SO₄²⁻ toxicity.     

Increasing NaCl and CaCl2 concentrations in the growth medium of quince leaves: II. Effects on shoot regeneration

Summary The effects of NaCl and CaCl₂ on shoot regeneration from quince (Cydonia oblonga BA L29 clone) leaves were investigated. Caulogenesis was induced on in vitro-grown leaves treated for 2d in liquid Murashige and Skoog (MS) medium with 11.3 μM 2,4-dichlorophenoxyacetic acid and cultured on MS gelled medium supplemented with 4.5 μM thidiazuron and 0.5 μM naphthaleneacetic acid. Three experiments were performed: in the first, we compared the effects of NaCl at 0, 25, 50, 100, and 200 mM in factorial combination with 3, 9, and 27 mM CaCl₂. In the second, NaCl was tested at 0, 5, 10, 20, 40, and 80 mM with CaCl₂ at 0.3, 1.0, and 3.0 mM. The third experiment was carried out with the same experimental design as the second one but replacing NaCl with Na₂SO₄. Shoot regeneration was evaluated after 50 d of culturing: 25 in darkness and 25 in white light. In the first experiment, shoot regeneration was very poor and was observed only at the lower salt concentrations. In the second experiment, the percentages of caulogenic leaves were much higher, but decreased with increasing NaCl concentration. The more pronounced negative effect of the highest NaCl concentrations appeared to be partly mitigated by CaCl₂ at 1 and 3 mM. The presence of 3 mM CaCl₂, in the experiment with Na₂SO₄, appeared to be even more effective in reducing the adverse effect of sodium stress on caulogenesis. This result was attributed to the lower Cl⁻ concentration in the growth medium, which resulted from replacing NaCl with Na₂SO₄. NaCl applied at low concentrations (5 and 10 mM) in combination with 3 mM CaCl₂ exerted a favorable effect on adventitious shoot regeneration. As regards the Na⁺ and Ca²⁺ interaction, when the Na⁺/Ca²⁺ ratio was below roughly 35 and 20, with NaCl and Na₂SO₄, respectively, at least 60% of leaves showed regenerating capacity, but optimal values of this ratio were not derived.     

Gluconic Acid Fermentation by Pullularia pullulans

During the study on the sugar metabolism of molds, several strains of Pullularia pullulans were found to produce large amounts of gluconic acid from glucose. Thirty seven strains of P. pullulans were then tested for their acid-producing abilities. Seven strains did not produce any amount of gluconic acid. However, all of the other strains were shown to be capable of producing this acid. The superior strains produced yiclds of gluconic acid as high as about 90%, based on glucose available, in shaking cultures at 30°C after 2 days. The yields were increased up to approximately 100% during later stages. In addition to high yields, gluconic acid was produced exclusively by these strains. Glutamic acid and inorganic ammonium salts, such as (NH₄)₂SO₄, NH₄Cl and (NH₄)₂HPO₄, were favorable nitrogen sources for acid production. In the case of (NH₄)₂SO₄, the optimum concentration was 0.05%. The addition of CaCO₃ was essential for gluconic acid production by P. pullulans and a 3% concentration of CaC0₃ appeared to be desirable for the maximum conversion to gluconic acid in a medium containing 10% glucose.     

Betaine aldehyde oxidation by spinach chloroplasts

Chenopods synthesize betaine by a two-step oxidation of choline: choline → betaine aldehyde → betaine. Both oxidation reactions are carried out by isolated spinach (Spinacia oleracea L.) chloroplasts in darkness and are promoted by light. The mechanism of betaine aldehyde oxidation was investigated with subcellular fractions from spinach leaf protoplasts. The chloroplast stromal fraction contained a specific pyridine nucleotide-dependent betaine aldehyde dehydrogenase (about 150 to 250 nanomoles per milligram chlorophyll per hour) which migrated as one isozyme on native polyacrylamide gels stained for enzyme activity. The cytosol fraction contained a minor isozyme of betaine aldehyde dehydrogenase. Leaves of pea (Pisum sativum L.), a species that lacks betaine, had no betaine aldehyde dehydrogenase isozymes. The specific activity of betaine aldehyde dehydrogenase rose three-fold in spinach plants grown at 300 millimolar NaCl; both isozymes contributed to the increase. Stimulation of betaine aldehyde oxidation in illuminated spinach chloroplasts was due to a thylakoid activity which was sensitive to catalase; this activity occurred in pea as well as spinach, and so appears to be artifactual. We conclude that in vivo, betaine aldehyde is oxidized in both darkness and light by the dehydrogenase isozymes, although some flux via a light-dependent, H₂O₂-mediated reaction cannot be ruled out.     

披针叶黄华试管苗适应盐胁迫的渗透调节机制

以披针叶黄华(Thermopsis lanceolata)试管苗为材料,通过组培方法研究其在0、0.2%、0.4%、0.6%、0.8%和1.0%NaCl和Na2SO4胁迫30d后的生长、有机渗透调节物质和无机渗透调节物质(Na+、K+和Ca2+)含量的变化,以探讨其耐盐性机制。结果显示:(1)随NaCl和Na2SO4胁迫浓度的增加,披针叶黄华试管苗叶片脯氨酸和可溶性糖含量均显著持续增加,且NaCl胁迫下脯氨酸上升的幅度均大于相同浓度Na2SO4胁迫下的增幅,而可溶性糖上升的幅度却小于相同浓度Na2SO4胁迫下的幅度;可溶性蛋白含量随NaCl浓度的增大呈先升高后降低的趋势,但随Na2SO4浓度的增加呈持续上升的趋势。(2)随NaCl和Na2SO4浓度的增加,披针叶黄华试管苗Na+含量呈增加趋势且各处理均显著高于对照,Ca2+含量和叶片K+含量却呈逐渐减少趋势且各处理均显著低于对照,而根系K+含量呈先降后升的趋势;Na2SO4胁迫下披针叶黄华试管苗叶片Na+含量上升幅度以及K+和Ca2+含量下降幅度均明显低于相同浓度NaCl胁迫组;而Na+/K+和Na+/Ca2+比值随NaCl和Na2SO4浓度增加而升高;NaCl胁迫下,叶片Na+/K+和Na+/Ca2+高于相同浓度Na2SO4胁迫下的比值,而根系Na+/K+和Na+/Ca2+却低于相同浓度Na2SO4胁迫下的比值。研究表明,盐胁迫下,披针叶黄华试管苗通过抑制叶片中Na+积累并增加可溶性糖和可溶性蛋白含量,在根系中维持较高K+和Ca2+含量以及较低水平Na+/K+和Na+/Ca2+比,以降低披针叶黄华细胞渗透势来适应盐渍环境;披针叶黄华对NaCl胁迫的调节能力弱于Na2SO4。     

四翅滨藜生理生化特征对盐胁迫的响应

采用温室盆栽试验研究四翅滨藜(Atriplex canescens)幼苗株高、地径、生物量、净光合速率、蒸腾速率、气孔导度、叶绿素含量、抗氧化酶活性及丙二醛含量对不同浓度NaCl和Na_2SO_4(0、100、200、300和400mmol·L~(-1))胁迫的响应,以探讨四翅滨藜对不同种类及不同浓度盐渍环境的适应机制及其耐盐机理。结果显示:(1)随着盐分浓度的升高,四翅滨藜幼苗的株高、地径及生物量增量呈现出先升高后降低的趋势,低盐浓度下2种盐均促进幼苗生长,盐浓度超过400mmol·L~(-1)时,NaCl对幼苗生长具有明显抑制作用。(2)2种盐处理下,四翅滨藜幼苗净光合速率(Pn)和叶绿素含量(Chl)随盐浓度增大而升高,即2种盐均对幼苗Pn和Chl含量具有促进作用,且Na_2SO_4的促进效果大于NaCl;而幼苗蒸腾速率(Tr)和气孔导度(Gs)随盐浓度升高呈先增大后减小的趋势,且Na_2SO_4的促进作用强于NaCl。(3)与对照相比,四翅滨藜幼苗的丙二醛、SOD、POD酶活性在NaCl和Na_2SO_42种盐处理下,随着盐浓度的升高均呈现出不同程度的增大,且增大幅度总体表现为NaClNa_2SO_4。研究表明,四翅滨藜在NaCl和Na_2SO_4胁迫下,叶绿素的分解速率以及发挥作用的渗透调节物质均有差异,使得幼苗叶片健康程度不同,导致叶片光合能力大小的差异,最终表现为植株的生长差异;四翅滨藜具有较强的耐盐能力,而且对Na_2SO_4的适应能力强于NaCl。     

Effects of NaCl or Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> salinity on plant growth,ion content and photosynthetic activity in <Emphasis Type="Italic">Ocimum basilicum</Emphasis> L.

Basil (Ocimum basilicum L., cultivar Genovese) plants were grown in Hoagland solution with or without 50 mM NaCl or 25 mM Na₂SO₄. After 15 days of treatment, Na₂SO₄ slowed growth of plants as indicated by root, stem and leaf dry weight, root length, shoot height and leaf area, and the effects were major of those induced by NaCl. Photosynthetic response was decreased more by chloride salinity than by sulphate. No effects in both treatments on leaf chlorophyll content, maximal efficiency of PSII photochemistry (F _v/F _m) and electron transport rate (ETR) were recorded. Therefore, an excess of energy following the limitation to CO₂ photoassimilation and a down regulation of PSII photochemistry was monitored under NaCl, which displays mechanisms that play a role in avoiding PSII photodamage able to dissipate this excess energy. Ionic composition (Na⁺, K⁺, Ca²⁺, and Mg²⁺) was affected to the same extent under both types of salinity, thus together with an increase in leaves Cl⁻, and roots SO₄ ²⁻ in NaCl and Na₂SO₄-treated plants, respectively, may have resulted in the observed growth retardation (for Na₂SO₄ treatment) and photosynthesis activity inhibition (for NaCl treatment), suggesting that those effects seem to have been due to the anionic component of the salts.     

Effects of NaCl and Na2SO4 on Water Relations ofPlantago maritima (L.) andPlantago lanceolata (L.)

Transpiration and water absorption rates, stomatal and cuticular resistances to water vapour diffusion, were measured onPlantago maritima (halophyte) andPlantago lanceolata (glycophyte) grown in the presence of NaCl or Na₂SO₄. Water absorption was reduced in the presence of Na₂SO₄ and transpiration rate was increased when NaCl was added to the nutrient solution. The glycophyte daily water balance was more disturbed than that of the halophyte in the presence of Na₂SO₄.     

Characterization of Growth, Water Relations, and Proline Accumulation in Sodium Sulfate Tolerant Callus of Brassica napus L. cv Westar (Canola)

Unselected and sodium sulfate tolerant callus cultures of Brassica napus L. cv Westar were grown on media supplemented with mannitol, NaCl, or Na₂SO₄. In all cases, growth of tolerant callus, measured on a fresh weight or dry weight basis, was greater than that of unselected callus, which was also subject to necrosis on high levels of salt. Tissue water potential became more negative in both unselected and tolerant callus grown in the presence of mannitol or Na₂SO₄. Water potentials in unselected callus were more negative than those of the tolerant tissues; but over a range of Na₂SO₄ concentrations both cultures displayed osmotic adjustment, maintaining relatively constant turgor. Proline accumulation in both unselected and tolerant callus was low (15 to 20 micromoles per gram dry weight) in the absence of stress, but increased on media supplemented with mannitol, NaCl, or Na₂SO₄. Increases in proline concentration were approximately linear in tolerant callus, reaching a maximum of 130 to 175 micromoles per gram dry weight. In unselected callus, concentrations were higher, reaching 390 to 520 micromoles per gram dry weight. Proline accumulation was correlated with inhibition of growth, and there was a negative correlation between proline concentration and culture age for tolerant callus.     

Sodium‐specific foraging by leafcutter ant workers (Atta cephalotes,Hymenoptera: Formicidae)

1. Sodium is often a limiting nutrient for terrestrial animals, and may be especially sought by herbivores. Leafcutter ants are dominant herbivores in the Neotropics, and leafcutter foraging may be affected by nutritional demands of the colony and/or the demands of their symbiotic fungal mutualists. We hypothesized that leafcutter colonies are sodium limited, and that leafcutter ants will therefore forage specifically for sodium. 2. Previous studies demonstrated that leafcutter Atta cephalotes Linnaeus workers preferentially cut and remove paper baits treated with NaCl relative to water control baits. Atta cephalotes colonies in this study were presented with baits offering NaCl, Na₂SO₄, and KCl to test whether leafcutters forage specifically for sodium. Sucrose and water were used as positive and negative controls, respectively. 3. Atta foragers removed significantly more of the baits treated with NaCl and Na₂SO₄ than the KCl treatment, which did not differ from water. The NaCl and Na₂SO₄ treatments were collected at similar rates. We conclude A. cephalotes forage specifically for sodium rather than for anions (chloride) or solutes in general. This study supports the hypothesis that leafcutter ants are limited by, and preferentially forage for, sodium.     

Activity,stability and enantioselectivity of lipase-coated microcrystals of inorganic salts in organic solvents

Lipase-coated microcrystals of inorganic salts were prepared by dissolving enzymes in buffers and then mixing with 3 volumes of saturated salt solutions followed by drop-wise addition into polar precipitating organic solvents. The Mucor javanicus lipase-coated microcrystals did not show any activity for esterification of lauric acid with 1-propanol in isooctane when NaCl and Na₂SO₄ were used as the salts but showed much higher activity than the enzyme powder when KCl (10.0 times) and K₂SO₄ (5.8 times) were used as the salts and precipitated in 1-propanol. Acetonitrile was found to be the best precipitating solvent for preparing M. javanicus lipase-coated microcrystals, with enzyme activities 26.2 and 22.4 times higher than that of the enzyme powder when KCl and K₂SO₄ were used as precipitating salts, respectively. The presence of water in the precipitating solvents markedly decreased the enzyme activity. The M. javanicus lipase-coated microcrystals prepared using K₂SO₄ as the salt and acetonitrile as the precipitating solvent was as active at 80°C as at 40°C. No significant improvement in enantioselectivity of Candida rugosa lipase-coated microcrystals was observed for transesterification of 1-phenylethanol with vinyl acetate in hexane when the microcrystals were prepared by dissolving the enzymes in salt solutions containing 25% (v/v) of acetone or 2-propanol before precipitating in polar solvents.     

Redox Cycling of Iron Supports Growth and Magnetite Synthesis by Aquaspirillum magnetotacticum

Under anaerobic conditions and in the absence of alternative electron acceptors, growth of the magnetic bacterium Aquaspirillum magnetotacticum MSI was iron concentration dependent. Weak chelation of the iron (with quinate, oxalate, or 2,3-dihydroxybenzoate) enhanced growth, whereas strong chelation (with EDTA, citrate, or nitrilotriacetic acid) retarded the growth of strain MSI relative to that of controls lacking chelators. Growth was proportional to the percentage of unchelated iron in medium containing EDTA in various molar ratios to iron. Addition of the respiratory inhibitors antimycin A (5 μM), NaCN (10 mM), and NaN₃ (10 mM) inhibited growth with Fe(III) or NO₃^- as the terminal electron acceptor. Growth with O₂ and NO₃^- was inhibited by 2-heptyl-4-hydroxyquinolone-N-oxide (HOQNO) but not with 2 mM Fe(III). Under strongly reducing conditions, strain MS1 survived but grew poorly and became irreversibly nonmagnetic. Growth and iron reduction in anaerobic cultures were stimulated by the provision of small amounts of O₂ or H₂O₂. Slow infusion of air to cultures which had reduced virtually all of the Fe(III) in the medium (2 mM) supported a high rate of iron reoxidation (relative to killed controls) and growth in proportion to the amount of iron reoxidized. Oxygen consumption by iron-reducing cultures was predominantly biological, since NaCN and HOQNO both inhibited consumption. Inhibition of oxygen consumption (and iron reoxidation) by the addition of ferrozine and the inhibition of iron oxidation (and oxygen consumption) by the addition of HOQNO suggest that iron oxidation by strain MS1 is an aerobic respiratory process, perhaps tied to energy conservation. Iron oxidation was also necessary for magnetite synthesis, since in microaerobic denitrifying cultures, sequestration of reduced iron by ferrozine present in 10-fold molar excess to the available iron resulted in loss of magnetism and a severe drop in the average magnetosome number of the cells.     

Continuous cultures of tomato and citron roots in vitro

Summary Initial trials with tomato-root cultures disclosed the desirability of employing a gently agitated liquid medium containing iron in the chelated form. For the normal cultivars “Ace” and “Tropic”, subcultures were best achieved by utilizing sectors that possessed one or more newly emerged laterals. Continuous cultures of a nonlateral-forming tomato mutant, “Diageotropica”, and of citron were accomplished by subculturing tips of the elongating primary roots. The tomato roots were cultured in White's medium with the Fe₂(SO₄)₃ replaced by 0.03 mM NaFeEDTA. Sustained growth of citron-root tips necessitated the use of a medium containing Murashige and Skoog salts, 7.5% sucrose, 100 mg per I each of citric acid and thiamine HCl, and 5000 mg per li-inositol. The success with citron-root cultures was extendable to all cultivars ofC. medica L., but not to otherCitrus species relatives. Both citron and “Diageotropica” root cultures manifested undiminished elongation through repeated subcultures; but neither produced laterals in response to any cultural treatments. Research was supported in part by National Science Foundation Grant OIP75-10390 and Elvenia J. Slosson Fellowship in Ornamental Horticulture.     

Sodium is the critical factor leading to the positive halotropism of the halophyte Limonium bicolor

Previous studies indicate that the roots of nonhalophytes showed negative halotropism to salt stress to avoid salt damage. However, halotropism of euhalophytes and their possible reasons are little known. Limonium bicolor, a typical recretohalophyte with multicellular salt glands, was used to study halotropism compared with Arabidopsis thaliana under NaCl, KCl and Na₂SO₄ stress. The elongation of the roots in L. bicolor was significantly promoted by the appropriate concentrations of NaCl, KCl and Na₂SO₄, but those of A. thaliana was markedly inhibited. However, isosmotic mannitol with 200?mM NaCl did not affect the root growth of both L. bicolor and A. thaliana. The root activity of both L. bicolor and A. thaliana was enhanced by salts. Compared with K⁺, Cl^–, and SO₄^2?, Na⁺ played a critical role in halotropism of L. bicolor. Furthermore, the gravitropic setpoint angle of L. bicolor increased under NaCl, KCl and Na₂SO₄ treatments compared with controls, and the phenomenon was most apparent under NaCl treatments. The endogenous IAA content of the NaCl-treated L. bicolor seedlings was significantly higher than that of the controls. These results suggest that the recretohalophyte L. bicolor has positive halotropism and Na⁺ plays a pivotal role in L. bicolor’s positive root halotropism by regulating IAA.     

Influence of NaCl and Na2SO4 on the kinetics and dye decolorization ability of crude laccase from Ganoderma lucidum

In a solid state medium using yellow passion fruit waste as substrate, the basidiomycete Ganoderma lucidum produced a laccase as the main ligninolytic enzyme. This crude enzyme presented Michaelian behavior with both substrates tested, namely 3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and the anthraquinone dye remazol brilliant blue R (RBBR). The K_M’s for these substrates were, respectively, 0.232 × 10⁻³ and 0.602 × 10⁻³ M. The actions of NaCl and Na₂SO₄, two important salts usually found in textile wastewaters, were investigated. The enzyme was inhibited by NaCl, but not by Na₂SO₄. Inhibition by NaCl was of the mixed type with two different inhibition constants. The enzyme was able to completely decolorize RBBR in the presence of 1.0 M Na₂SO₄ and 50% decolorization was found in the presence of 0.1 M NaCl. Such properties certainly make the enzyme a good agent for textile dye effluent treatment considering the fact that wastewaters of this industry usually contain high concentrations of NaCl and Na₂SO₄.