Buoyancy effect on forced convection in the leaf boundary layer

Abstract. Mixed convection (forced convection plus free convection) in the leaf boundary layer was examined by air flow visualization and by evaluation of the boundary layer conductance at different leaf-air temperature differences ( T _L- T _A) under low wind velocities. The visualized air flow was found to become more unstable and buoyant at higher T _L- T _A. An ascending longitudinal plume was induced along the upper surface, and the air flow along the lower surface ascended after passing the trailing leaf edge. The air flow modified by buoyancy was considered to result in an increase in boundary layer conductance ( G _A) for mixed convection, which became higher with higher T _L- T _A as compared with the conductance for pure forced convection without buoyancy. This increase in G _A appeared larger at larger Grashof number (Gr) and at smaller Reynolds number (Re). The dependences of buoyancy effect on Gr and Re were related to 'edge-effects'.     

Mineral sulphide oxidation by enrichment cultures of novel thermoacidophilic bacteria

Abstract: Enrichment culture of hot spring water samples with pyrite as substrate has provided acidophiles with novel growth characteristics: with these bacteria, the range of conditions under which rapid microbial oxidation of mineral sulphides has been demonstrated has been extended. The upper temperature limit for bacterial mineral oxidation in reactors has been raised. The dissolution of pyrite occurred during growth of Sulfolobus -like thermophiles up to almost 90C. The most efficient extraction of copper from chalcopyrite occurred at 80–85C. With moderate thermophiles, rapid oxidation of minerals was obtained during autotrophic growth in the absence of supplemental CO₂: a mixed enrichment culture was active in pyrite dissolution at 45–50C in reactors gassed only with air which contrasted with poor growth by well-studied moderate thermophiles in the absence of enhanced CO₂ concentrations.     

Age, growth and reproduction of the barrelfish Hyperoglyphe perciformis (Mitchill) in the western North Atlantic

Otoliths ( n = 847) and gonads ( n = 817) were collected from barrelfish Hyperoglyphe perciformis that were captured by commercial fishermen in the waters off South Carolina and Georgia in 1995, 1997 and 2001–2006. Of the otoliths collected, 97% were aged successfully, and specimens sampled ranged from 5 to 85 years, with a median age of 12 years. The von Bertalanffy growth parameters yielded the equation: L_t = 857·8{1 − e^{−0·0985[ t −(−8·95)]}}, where L_t is fork length ( L _F) at time t . Through histological examination, 94% of the gonads assessed were assigned to a sex and reproductive class. Females spawned from September to May with a peak from November to January. Males spawned year round, but had a peak from September to April. The sex ratio (M:F) for this population was 1:1·34. The smallest mature female was 605 mm L _F and the youngest immature female was 697 mm L _F. Estimates of L _F and age at 50% maturity ( L ₅₀ and A ₅₀) for females were 660 mm L _F (95% CI = 633–667 mm L _F) and 6·08 years (95% CI = 3·50–7·27 years), respectively. The youngest mature male was 575 mm L _F and the oldest immature male was 762 mm L _F, and no estimates of L ₅₀ or A ₅₀ were made for males. It was determined that barrelfish exhibit the typical characteristics of long life span, slow growth and high age at maturity seen in other deepwater fishes, and that care should be taken to manage this species accordingly.     

Matrix composition and community structure analysis of a novel bacterial pyrite leaching community

Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS₂) oxidation. This community grows in stalactite-like structures – snottites – on the ceiling of an abandoned pyrite mine at pH values of 2.2–2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro-X-ray diffraction analysis showed that jarosite [(K,Na,H₃O)Fe₃(SO₄)₂(OH)₆] is the major mineral embedded in the snottites. X-ray absorption near-edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self-contained consortium of bacterial species fuelled by the decomposition of pyrite.     

Effects of rapid changes in oxygen concentration on the respiration of carrot roots

Rates of CO₂ production and O₂ consumption from aged disks of carrot ( Daucus carota L.) root tissues were measured for 4 h after they were transferred from 21% to 0, 1, 2, 4 or 8% O₂ in gas mixtures. A transient peak in the rate of CO₂ production started 5 to 7 min after transfer to 2% or lower O₂ mixtures and peaked at 50 min. After the peaks in CO₂ production from the 0, 1 and 2% O₂ treatments and after the stable production from the 4 and 8% O₂ treatments, the rate of CO₂ production from all low O₂ treatments started to decline at 50 min, reaching stable rates by 160 to 240 min. Concentrations of lactate and ethanol that were significantly higher than the 21% O₂ controls had started to accumulate in disks between 10 and 50 min after exposure to atmospheres containing 2% or less O₂. Production of CO₂ started to increase 5 to 7 min after transfer to 0, 1 and 2% O₂, while the initial decline and then rise in pH and the accumulation of ethanol did not occur until 30 min after the change in atmosphere. Ethanol accumulation paralleled the increase in pH; first at 0.4 μmol g⁻¹ h⁻¹ from 30 to 60 min as the pH shifted from 5.97 to 6.11, and then at 0.08 μmol g⁻¹ h⁻¹ from 60 to 100 min as the pH stablized around 6.12. The peak at 50 min in CO₂ production roughly coincided with the shift from the rapid to the slow change in pH and ethanol accumulation.     

A desk study of the relationship between temperature and hatching time for the eggs of five species of salmonid fishes

SUMMARY. Information on temperature (T°C) and time from fertilization to 50% hatch ( D days) for five species of salmonid fishes has been used to assess several mathematical models relating D and T . No single equation gave the best fit to all five data sets. The power law with temperature correction (α), log₁₀₁ D = log₁₀ a + b log₁₀ ( T - α) and the quadratic, log₁₀ D = log₁₀ a + bT + b ₁ T ² (where a, b, b ₁, and α are constants), each accounted for over 97 % of the variance of D and were good fits to the observed data points for all five species. There was little difference between the predictions obtained from these two equations within the range of observed temperatures. Therefore, the simpler power-law model is preferred. However, there were substantial within-species differences between values of D predicted from extrapolations of the two models from 2 or 3°C down to 0°C. When more data for low temperatures become available it will be possible to make a more objective choice of model.     

Relative toxicity of nC24 agricultural mineral oil to Tetranychus urticae Koch (Acari: Tetranychidae) and Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) and its possible relationship to egg ultrastructure

The relative toxicity (LC₅₀ values based on µg oil/cm²) is evaluated of aqueous n C24 agricultural mineral oil (AMO) emulsions to the egg, six-legged nymph (larva), eight-legged protonymph and adult stages of two-spotted mite ( Tetranychus urticae ) and its predator, Phytoseiulus persimilis , on French bean leaf discs, using a Potter spray tower to apply of the oil. The egg of P. persimilis was the least susceptible stage (LC₅₀ 444.84) and its LC₅₀ was significantly higher than all other stages tested of either P. persimilis or T. urticae . The LC₅₀ for adult female T. urticae (LC₅₀ 63.89) was significantly lower than the larva (LC₅₀ 93.86); however, there was no significant difference in response between the protonymph (LC₅₀ 70.44) and the larva, which were both higher than T. urticae eggs (LC₅₀ 17.55). LC₅₀s for P. persimilis larva (LC₅₀ 43.87), protonymph (LC₅₀ 41.55) and adult female (LC₅₀ 53.34) were similar. Scanning electron microscopy showed that the egg surface of T. urticae is usually well covered with fine silk that may trap more oil and increase AMO efficacy. Other possible differences in AMO efficacy between T. urticae and P. persimilis may be due to differences in egg size, egg incubation period, egg surface structure and the presence of vulnerable respiratory cones in T. urticae eggs. Dose of 0.2–0.3% (w/w) is considered to be the most appropriate for n C24 AMOs use against T. urticae in combination with P. persimilis in integrated pest management programs.     

Studies on the effect of mercury and organomercurial on the growth and nitrogen fixation by mercury-resistant Azotobacter strains

Five nitrogen-fixing Azotobacter strains isolated from agricultural farms in West Bengal, India, were resistant to mercuric ion and organomercurials. Resistance of Hg-resistant bacteria to mercury compounds is mediated by the activities of mercuric reductase and organomercurial lyase in the presence of NADPH and GSH as cofactors. These bacteria showed an extended lag phase in the presence of 10–50 μmol 1^-1 HgCl₂. Nitrogen-fixing ability of these isolates was slightly inhibited when the mercuryresistant bacterial cells were preincubated with 10 μmol 1^-1 HgCl₂. Acetylene reduction by these bacteria was significantly inhibited (91-97%) by 50 μmol 1^-1 HgCl₂. However, when GSH and NADPH were added to the acetylene reduction assay mixture containing 50 μmol 1^-1 HgCl₂, only 42–50% inhibition of nitrogenase activity was observed. NADPH and GSH might have a role in suppressing the inhibition of N₂-fixation in the presence of Hg compounds either by assisting Hg-detoxifying enzymes to lower Hg concentration in the assay mixture or by formation of adduct comprising Hg and GSH which is unable to inhibit nitrogen fixation.     

Indole-3-methanol as an intermediate in the oxidation of indole-3-acetic acid by peroxidase

During oxidation of indole-3-acetic acid catalyzed by horseradish peroxidase, indole-3-aldehyde and 3-hydroxymethayloxindole cease to be produced a few minutes after initiation of the reaction even though IAA is still being consumed. At the same time an increased accumulation of indole-3-methanol is observed and the ratio of oxygen to indole-3-acetic acid consumed becomes less than unity. Indole-3-niethanol can be a substrate for horseradish peroxidase provided that H₂O₂ is present. In this reaction, indole-3-aldehyde but not 3-hydroxymethyloxindole is formed. H₂O₂ is not merely an activating agent for the enzyme but also a true oxidant because it is consumed stoichiometrically (1 mol of H₂O₂ per mol of indole-3-methanol) and the reaction is independent of the presence of oxygen. Indole-3-methanol is proposed as an intermediate in the process of oxidation of indole-3-acetic acid into indole-3-al-denyde, the second step of which requires peroxide as an oxidant.     

Involvement of matrix NADP turnover in the oxidation of NAD-linked substrates by pea leaf mitochondria

The involvement of the internal rotenone-insensitive NADPH dehydrogenase on the inner surface of the inner mitochondrial membrane [ND_in(NADPH)] in the oxidation of strictly NAD⁺-linked substrates by pea ( Pisum sativum L.) leaf mitochondria was measured. As estimated by the inhibition caused by 5 μ M diphenyleneiodonium (DPI) in the presence of rotenone to inhibit complex I, the activity of ND_in(NADPH) during glycine oxidation (measured both as O₂ uptake and as CO₂ release) was 40–50 nmol mg⁻¹ protein min⁻¹. No significant activity of ND_in(NADPH) could be detected during the oxidation of 2-oxoglutarate, another strictly NAD⁺-linked substrate; this was possibly due to its relatively low oxidation rate. Control experiments showed that, even at 125 μ M , DPI had no effect on the activity of glycine decarboxylase complex (GDC) and lipoamide dehydrogenase. The relative activity of complex I, ND_in(NADPH), and ND_in(NADH) during glycine oxidation, estimated using rotenone and DPI, differed depending on the pyridine nucleotide supply in the mitochondrial matrix. This was shown by loading the mitochondria with NAD⁺ and NADP⁺, both of which were taken up by the organelle. We conclude that the involvement of NADP turnover during glycine oxidation is not due to the direct production of NADPH by GDC but is an indirect result of this process. It probably occurs via the interconversion of NADH to NADPH by the two non-energy-linked transhydrogenase activities recently identified in plant mitochondria.     

Methyl sulfides as intermediates in the anaerobic oxidation of methane

While it is clear that microbial consortia containing Archaea and sulfate-reducing bacteria (SRB) can mediate the anaerobic oxidation of methane (AOM), the interplay between these microorganisms remains unknown. The leading explanation of the AOM metabolism is 'reverse methanogenesis' by which a methanogenesis substrate is produced and transferred between species. Conceptually, the reversal of methanogenesis requires low H₂ concentrations for energetic favourability. We used ¹³C-labelled CH₄ as a tracer to test the effects of elevated H₂ pressures on incubations of active AOM sediments from both the Eel River basin and Hydrate Ridge. In the presence of H₂, we observed a minimal reduction in the rate of CH₄ oxidation, and conclude H₂ does not play an interspecies role in AOM. Based on these results, as well as previous work, we propose a new model for substrate transfer in AOM. In this model, methyl sulfides produced by the Archaea from both CH₄ oxidation and CO₂ reduction are transferred to the SRB. Metabolically, CH₄ oxidation provides electrons for the energy-yielding reduction of CO₂ to a methyl group ('methylogenesis'). Methylogenesis is a dominantly reductive pathway utilizing most methanogenesis enzymes in their forward direction. Incubations of seep sediments demonstrate, as would be expected from this model, that methanethiol inhibits AOM and that CO can be substituted for CH₄ as the electron donor for methylogenesis.     

Stable isotope ecology of fossil hippopotamids from the Lake Turkana Basin of East Africa

The diet of African hippopotamids can be documented through δ ¹³C analyses of enamel and other tissues. Analysis of a 10-million-year sequence of hippopotamids in and near the Lake Turkana Basin of northern Kenya shows that hippos have included a substantial fraction of C₃ vegetation in their diets since the late Miocene when C₄ vegetation first appears in hippo diet as a measurable fraction. The C₄ component of vegetation becomes dominant (>50%) by Upper Burgi time ( c . 2 million years ago) but does not reach 100% for all individuals. It is therefore not unexpected that the δ ¹³C values of modern hippopotamids show a higher fraction of dietary C₃ biomass than has been estimated from traditional observations. Analysis of δ ¹⁸O of hippos from different stratigraphic levels shows no systematic trend over time; the average value for fossil hippos over the last 10 million years is similar to that of modern hippos from the Omo River system.     

Cell Surface Sialoglycoproteins of Cultured Rat Cerebellar Interneurons

Abstract: The sialoglycoproteins of cultures of relatively pure rat cerebellar interneurons were labelled by NaIO₄ oxidation/NaB ³H₄ reduction. The labelled molecules were analysed by polyacrylamide gel electrophoresis in sodium dodecyl sulphate followed by fluorography. Faint labelling could be detected in three components if cells were labelled without any oxidation. In young cultures, oxidation by galactose oxidase alone failed to reveal any additional bands. After oxidation by NaIO₄ or galactose oxidase in the presence of neuraminidase, many more components were labelled. After NaIO₄ oxidation, about 80% of the cell-associated radioactivity could be removed by treating the cells with neuraminidase, which left the cells more than 95% viable. The majority of the bands seen after neuraminidase treatment were substantially reduced when compared with untreated controls, supporting a surface localisation of these molecules. Reproducible developmental changes were seen in the profiles of bands labelled by NaIO₄/NaB ³H₄ in time course studies of cultures up to 8 days in vitro . Some bands became more prominent, and others disappeared. The gel profiles of the neuron cultures were quite distinct from those of cerebellar astrocyte cultures, which contain all the cell types likely to be contaminants of the neuron cultures.     

Studies on a Capillary-Rich Fraction Isolated from Brain: Histaminic Components and Characterization of the Histamine Receptors Linked to Adenylate Cyclase

Abstract: A fraction enriched in capillaries has been prepared from the guinea pig cerebral cortex. The purity of this fraction was checked by light- and electron-microscopic examination and by its high enrichment in alkaline phosphatase and γ-glutamyl transpeptidase. In the capillary-rich fraction, the endogenous level of histamine was 1.9%'of that measured in the initial hornogenate. The histamine-synthesizing enzyme, I-histidine decarboxylase, and the metabolizing enzyme, histamine-N-methyltransferase, were barely detectable. In addition, histamine elicits a twofold stimulation in the accumulation of cyclic AMP in this capillary fraction with an EC₅₀ of 5 γM. Agonists and antagonists of the two types of histamine receptors (H₁ and H₂) were used for the characterization of the receptors mediating this action: H₂-receptor agonists were able to activate the adenylate cyclase with "relative potencies" similar to that found on typical H₂-receptors, and cimetidine, a specific H₂-receptor antagonist, competitively inhibited the response to histamine with a K₁ value reflecting its interaction with a single population of H₂-receptors. On the contrary, data obtained with H₁-receptor agonists and antagonists reflect their interaction with H₂-receptors rather than H₁-receptors. Thus H₂-receptors are involved in the activation of adenylate cyclase of the capillary fraction.     

Endocrine, osmoregulatory, respiratory and haematological parameters in flounder exposed to the water soluble fraction of crude oil

Flounders Pleuronectes flesus with an implanted vascular catheter were exposed to a 50% dilution of the water soluble fraction (WSF) of Omani crude oil (c. 6ppm total aromatic hydrocarbons) and serial blood samples taken to determine their endocrine status (cortisol, catecholamines and thyroid hormones) and the resultant and/or causal physiological (haematological, ionoregulatory and respiratory) disturbances. This resulted in a progressive increase in plasma cortisol concentrations from 3 h onwards (rising from 18 to 51 ng ml⁻¹ after 48-h exposure), and increased plasma glucose concentrations indicating a generalized stress response. Plasma T3 and T4 concentrations of both control and WSF-exposed groups declined progressively over the experimental period; exposure to the WSF of crude oil further depressed plasma T4 concentrations but not plasma T₃ concentrations relative to those of control fish. Plasma osmolality and sodium and chloride concentrations were stable in WSF-exposed fish, however, plasma potassium concentrations were increased significantly at the 24-and 48-h sampling points. The most profound physiological disturbance in WSF-exposed fish was a dramatic decline in blood oxygen content (CvO₂) (from 2–8 to 0–8 ml 100 ml⁻¹ after 48-h exposure), which is likely to be the cause of the increased plasma noradrenaline concentrations from 3 h onwards. Increased noradrenaline is likely in turn to have been responsible for the significant increase in blood haematocrit and blood haemoglobin at the 3-h sampling point, although the dominant effect in the longer-term was a significant decline in both of these haematological parameters.     

Sequential phospholipase activation in the stimulation of the neutrophil NADPH oxidase

Abstract Stimulation of human neutrophils with the chemotactic peptide fMet-Leu-Phe results in activation of a rapid, transient burst of oxidant secretion, which reaches a maximal rate by about 1 min after stimulation. This phase of oxidant secretion is then followed by intracellular oxidant production, which is detected by luminol chemiluminescence but not by assays such as cytochrome c reduction or scopoletin oxidation. The rapid phase of oxidant secretion requires increases in intracellular free Ca²⁺ and phospholipase A₂ activity, but not the activities of phospholipase D or D or protein kinase C. In contrast, intracellular oxidant production requires the activities of phospholipase D and protein kinase C. A model is thus proposed suggesting the sequential activation of different phospholipases which activate oxidase molecules on the plasma membrane or else from the membranes of specific granules.     

Anaerobic sulfur oxidation in the absence of nitrate dominates microbial chemoautotrophy beneath the pelagic chemocline of the eastern Gotland Basin, Baltic Sea

Oxic–anoxic interfaces harbor significant numbers and activity of chemolithoautotrophic microorganisms, known to oxidize reduced sulfur or nitrogen species. However, measurements of in situ distribution of bulk carbon dioxide (CO₂) assimilation rates and active autotrophic microorganisms have challenged the common concept that aerobic and denitrifying sulfur oxidizers are the predominant autotrophs in pelagic oxic–anoxic interfaces. Here, we provide a comparative investigation of nutrient, sulfur, and manganese chemistry, microbial biomass distribution, as well as CO₂ fixation at the pelagic redoxcline of the eastern Gotland Basin, Baltic Sea. Opposing gradients of oxygen, nitrate, and sulfide approached the detection limits at the chemocline at 204 m water depth. No overlap of oxygen or nitrate with sulfide was observed, whereas particulate manganese was detected down to 220 m. More than 70% of the bulk dark CO₂ assimilation, totaling 9.3 mmol C m⁻² day⁻¹, was found in the absence of oxygen, nitrite, and nitrate and could not be stimulated by their addition. Maximum fixation rates of up to 1.1 μmol C L⁻¹ day⁻¹ were surprisingly susceptible to altered redox potential or sulfide concentration. These results suggest that novel redox-sensitive pathways of microbial sulfide oxidation could account for a significant fraction of chemolithoautotrophic growth beneath pelagic chemoclines. A mechanism of coupled activity of sulfur-oxidizing and sulfur-reducing microorganisms is proposed.     

Sensitivity of methanogenic bacteria from paddy soil to oxygen and desiccation

Abstract The effects of combinations of desiccation and exposure to O₂ were studied in pure cultures of Methanosarcina barkeri strain Fusaro and in a new Methanosarcina strain and a new Methanobacterium strain which were both isolated from dry oxic paddy soil. Incubation of bacterial suspensions under air for 200 min resulted in a decreased potential to produce CH₄, but not in a decreased viability. The inhibitory effect of O₂ slightly increased with increased salt concentration. Desiccation of bacterial suspensions under N₂ resulted in reduction of viability to 10% and of potential CH₄ production to 0.6%. Desiccation of bacterial suspensions under air resulted in a larger decrease of both viability (0.5%) and potential CH₄ production (0.03%). This decrease was smaller at rapid compared to slow desiccation. Survival and potential CH₄ production were further inhibited when the suspension was dried in the presence of sand grains or glass beads coated with FeS or FeNH₄PO₄. However, survival and potential CH₄ production increased dramatically in the presence of pyrite (FeS₂) grains. Then, as much as 10% of the initial methanogenic population survived oxic desiccation. This relatively good resistance is in agreement with observations that methanogens in rice fields survive the periods when the paddy soil is dry and oxic.     

Effects of the triazole plant growth retardant BAS 111¨W on gibberellin levels in oilseed rape, Brassica napus

Three-week-old shoots of the spring oilseed rape cv. Petranova ( Brassica napus L. ssp. napus ) were found by combined gas chromatography-mass spectrometry to contain GA₁, GA₈, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₄, GA₂₉, 3-epi-GA₁ and a previously uncharacterised C₁₉ dicarboxylic acid that is probably structurally related to GA₂₄. Shoots of the winter cultivar Belinda, harvested at the early flowering stage, contained the same GAs with the exception of the C₁₉ dicarboxylic acid and, in addition, GA₃₄ and GA₅₁ were identified. All material contained higher levels of GA₂₀ than of GA₁; the ratio of GA₁ to GA₂₀ was highest in shoots containing the largest proportion of young immature tissues. Soil treatment of cv. Petranova seedlings with the growth retardant BAS 111¨W [1-phenoxy-5,5-dimethyl-3-(1,2,4-triazol-1-yl)-hexan-4-ol] caused 80% reduction in height 18 days after treatment and the levels of all GAs were 20% or less that of control plants. Foliar treatment at the same dosage reduced height by 50% and caused an 85% or greater reduction in the concentrations of the GA₁ precursors GA₂₀, GA₁₉ and GA₄₄. However, the levels of GA₁, GA₈ and GA₂₉ were affected to a much smaller extent. Foliar application of BAS 111¨W to cv. Belinda 1 month after sowing resulted in only a 20% height reduction at flowering, but no uniform decrease in the concentrations of endogenous GAs at this stage.     

Life‐history variation among local populations of Atlantic cod from the Norwegian Skagerrak coast

Small‐scale spatial variation in life history was found among genetically distinct local populations of Atlantic cod Gadus morhua from the Norwegian Skagerrak coast. Among populations, age at 50% maturity varied from 2·6 to 3·8 years, total ( L _T) length at 50% maturity from 35 to 60 cm, annual survival from 33 to 64%, mean L _T at age 4 years from 43 to 63 cm, and mean backcalculated L _T at age 1 year from 8 to 12 cm.