Sagebrush carbon allocation patterns and grasshopper nutrition: the influence of CO2 enrichment and soil mineral limitation

Summary Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650 l l^–1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO₂ led to a doubling of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO₂. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by changes in carbon allocation to shoot mass alone. Growth under CO₂ enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO₂ and low nutrient availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient limitation slightly reduced the C/N balance among the high-CO₂ plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO₂ enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO₂ treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content.     

Data consistency,yield, maintenance,and hysteresis in batch cultures of Candida lipolytica cultured on n-hexadecane

Candida lipolytica was cultured batchwise using n-hexadecane as the main carbon source. Biomass production, n-hexadecane consumption, oxygen consumption, and carbon dioxide evolution were measured to follow the fermentation. The consistency of the measured data was examined using integrated and instantaneous available electron and carbon balances. Values of the “true” growth yield, η_max, and maintenance coefficient, m_e were estimated using three different sets of data (biomass and n-hexadecane, oxygen and biomass, and CO₂ and biomass), and the results were compared with estimates obtained from literature data. Hysteresis patterns were observed in plots of specific rates of oxygen consumption and carbon dioxide evolution versus specific growth rate.     

Microbial gas balance measurements: Basic interrelations and error estimation

The given paper represents formulae for calculation of oxygen consumption and of carbon dioxide formation in a microbial culture obtained from corrected measuring data of gas balance measurements. Basic relations between these measuring data the respiration quotient RQ were derived. The influence of measuring error to the accuracy of determination of oxygen consumption and of carbon dioxide formation at the analysis of gas concentrations and of air flow is discussed. It is shown that the determination of carbon dioxide formation rate is possible in many cultivation regimes with better accuracy than the determination of oxygen uptake rate.     

Über den Einfluß niedriger und hoher O2-Partialdrucke auf den Sauerstoff- und Kohlendioxidumsatz von Amaranthus und Phaseolus während der Lichtphase

Summary Carbon dioxide and oxygen gas exchange of illuminated Amaranthus and Phaseolus leaves was measured from 0–600 ppm of CO₂ in an open system.At low oxygen concentration (2% O₂) the ratio of CO₂ uptake to O₂ evolution came close to 1.At high oxygen partial pressure (42% O₂) the O₂ compensation point of an Amaranthus leaf was increased and oxygen evolution was depressed. Accordingly the CO₂/O₂ quotients were variable; the lowest value of 1,9 differed significantly from 1,0.The oxygen and carbon dioxide compensation points of a Phaseolus leaf were increased at high oxygen concentration (42% O₂) and oxygen evolution as well as carbon dioxide uptake were reduced. Therefore the ratios CO₂ over O₂ varied and differed greatly from 1,0.It was concluded that the nature of photosynthates is regulated by the gas composition around the leaves.     

An increased carbon dioxide production in transient hypoxia in healthy subjects at rest

Indices of pulmonary gas exchange and heart rate (HR) have been measured in 24 healthy subjects not adapted to hypoxia after hypoxic aerial mixture (HAM) (17, 15, 13 vol % of oxygen) respiration for 15 min. Using group data analysis, it has been shown that hypoxia under the conditions of inhalation of 17 and 15 vol % of O₂ caused no significant changes. Hypoxia under the conditions of 13 vol % of O₂ inhalation is a threshold one, when ventilation (SpO₂) drops below 85%. A significant increase in the lung ventilation (Ve) (10–14%, p < 0.05) and HR (11–15%, p < 0.05) have been observed in this case. Hyperpnea was accompanied by an increase in the oxygen uptake rate by 10% and carbon dioxide release rate (10–18%, p < 0.05). On the contrary, individual data analysis showed changes in the pulmonary gas exchange indices in 90% of subjects in the case of inhalation of 17 vol % of O₂ HAM. Four response types have been found: ventilation (increase in lung ventilation), hypoxic hypometabolism (decrease in oxygen consumption rate), and mobilization response (increase in oxygen utilization in the lungs), and anaerobic response, which is expressed in an increase in the carbon dioxide release rate along with an increase in the respiratory quotient. All these responses are of an individual type, but the ventilation response is developed in response to hypoxia caused by inhalation of 13 vol % of O₂ HAM and a decrease in SpO₂ below 85% in more than 60% of cases.     

Central Venous-To-Arterial CO2-Gap May Increase in Severe Isovolemic Anemia

Despite blood transfusions are administered to restore adequate tissue oxygenation, transfusion guidelines consider only hemoglobin as trigger value, which gives little information about the balance between oxygen delivery and consumption. Central venous oxygen saturation is an alternative, however its changes reflect systemic metabolism and fail to detect regional hypoxia. A complementary parameter to ScvO₂ may be central venous-to-arterial carbon dioxide difference (CO₂-gap). Our aim was to investigate the change of alternative transfusion trigger values in experimental isovolemic anemia. After splenectomy, anesthetized Vietnamese mini pigs (n = 13, weight range: 18–30 kg) underwent controlled bleeding in five stages (T₁–T₅). During each stage approximately 10% of the estimated starting total blood volume was removed and immediately replaced with an equal volume of colloid. Hemodynamic measurements and blood gas analysis were then performed. Each stage of bleeding resulted in a significant fall in hemoglobin, the O₂-extraction increased significantly from T₃ and ScvO₂ showed a similar pattern and dropped below the physiological threshold of 70% at T₄. By T₄ CO₂-gap increased significantly and well correlated with VO₂/DO₂ and ScvO₂. To our knowledge, this is the first study to show that anemia caused altered oxygen extraction may have an effect on CO₂-gap.     

Genotypic variation for condensed tannin production in trembling aspen (POPULUS TREMULOIDES,salicaceae) under elevated CO2 and in high- and low-fertility soil

The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO₂ partial pressure and high- and low-fertility soil in field open-top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO₂ and low soil fertility compared to ambient CO₂ and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO₂, while others showed no CO₂ response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO₂, and fertility treatments. These results suggest that with rising atmospheric CO₂, plant secondary compound production may vary within species. This could have consequences for plant–herbivore and plant–microbe interactions and for the evolutionary response of this species to global climate change.     

Spatial variation of dissolved gas concentrations in a willow vegetation filter treating landfill leachate

Membrane inlet mass spectrometry (MIMS) was used to monitor continuously and simultaneously the concentrations of dissolved gases (O₂, CO₂, CH₄) within the treatment bed of a willow vegetation filter treating leachate at a landfill site in mid Wales. The distribution of dissolved gasses within the bed was shown to be highly heterogeneous at the small spatial scale with considerable variation between vertical profiles measured simultaneously at different locations. In general, aerobic conditions were observed above the water table with reduced levels of oxygen and increasing levels of carbon dioxide and methane below it. Distinct pockets of oxygen (up to 200 μM) were observed in anaerobic zones and pockets of reduced oxygen and elevated carbon dioxide were observed in the aerobic zone. Pockets of methane were observed in some profiles coexisting with up to 200 μM oxygen at 5 cm depth. These observations confirm the hypothesis that micro-sites exists within the soil/root matrix where aerobic organic matter decomposition and anaerobic processes such as methanogenesis can occur in relatively close proximity to each other. We hypothesise that the distribution of dissolved gases is determined by rapid diffusion of air maintaining aerobic conditions above the water table, removal of oxygen by microbial processes creating anaerobic conditions below the water table and the distribution of willow roots in the soil which create local aerobic zones by oxygen release.     

REDUCTION OF CARBON DIOXIDE COUPLED WITH THE OXYHYDROGEN REACTION IN ALGAE

1. Unicellular algae possessing a hydrogenase system (Scenedesmus and other species), and having been adapted by anaerobic incubation to the hydrogen metabolism, reduce oxygen to water according to the equation O₂ + 2H₂ → 2H₂O. 2. The oxyhydrogen reaction proceeds undisturbed only in the presence of carbon dioxide, which simultaneously is reduced according to the equation CO₂ + 2H₂ → H₂O + (CH₂O) = (carbohydrate). 3. The maximum yield of the induced reduction is one-half molecule of carbon dioxide reduced for each molecule of oxygen absorbed. 4. Partial reactions are recognizable in the course of the formation of water and it is with the absorption of the second equivalent of hydrogen that the carbon dioxide reduction appears to be coupled. 5. The velocity of the reaction increases in proportion to the partial pressure of oxygen, but only up to a certain point where any excess of oxygen causes the inactivation of the hydrogenase system. The reaction then ends prematurely. 6. During the oxyhydrogen reaction little or no oxygen is consumed for normal respiratory processes. 7. Small concentrations of cyanide, affecting neither photosynthesis nor photoreduction in the same cells, first inhibit the induced reduction of carbon dioxide and then lead to a complete inactivation of the hydrogenase system. 8. Hydroxylamine, added after adaptation, has either no inhibitory effect at all, or prevents solely the induced reduction of carbon dioxide without inactivating the hydrogenase system. 9. Dinitrophenol prevents the dark reduction of carbon dioxide while the reduction of oxygen continues to the formation of water. 10. Glucose diminishes the absorption of hydrogen, probably in its capacity as a competing hydrogen donor. 11. The induced reduction of carbon dioxide can be described as an oxido-reduction similar to that produced photochemically in the same cells.     

Arbuscular Mycorrhizal Symbiosis with Arundo donax Decreases Root Respiration and Increases Both Photosynthesis and Plant Biomass Accumulation

The effect of arbuscular mycorrhiza (AM) symbiosis on plant growth is associated with the balance between costs and benefits. A feedback regulation loop has been described in which the higher carbohydrate cost to plants for AM symbiosis is compensated by increases in their photosynthetic rates. Nevertheless, plant carbon balance depends both on photosynthetic carbon uptake and respiratory carbon consumption. The hypothesis behind this research was that the role of respiration in plant growth under AM symbiosis may be as important as that of photosynthesis. This hypothesis was tested in Arundo donax L. plantlets inoculated with Rhizophagus irregularis and Funneliformis mosseae. We tested the effects of AM inoculation on both photosynthetic capacity and in vivo leaf and root respiration. Additionally, analyses of the primary metabolism and ion content were performed in both leaves and roots. AM inoculation increased photosynthesis through increased CO₂ diffusion and electron transport in the chloroplast. Moreover, respiration decreased only in AM roots via the cytochrome oxidase pathway (COP) as measured by the oxygen isotope technique. This decline in the COP can be related to the reduced respiratory metabolism and substrates (sugars and tricarboxylic acid cycle intermediates) observed in roots.     

Oxygen and carbon dioxide fluxes from barley shoots depend on nitrate assimilation

A custom oxygen analyzer in conjunction with an infrared carbon dioxide analyzer and humidity sensors permitted simultaneous measurements of oxygen, carbon dioxide, and water vapor fluxes from the shoots of intact barley plants (Hordeum vulgare L. cv Steptoe). The oxygen analyzer is based on a calciazirconium sensor and can resolve concentration differences to within 2 microliters per liter against the normal background of 210,000 microliters per liter. In wild-type plants receiving ammonium as their sole nitrogen source or in nitrate reductase-deficient mutants, photosynthetic and respiratory fluxes of oxygen equaled those of carbon dioxide. By contrast, wild-type plants exposed to nitrate had unequal oxygen and carbon dioxide fluxes: oxygen evolution at high light exceeded carbon dioxide consumption by 26% and carbon dioxide evolution in the dark exceeded oxygen consumption by 25%. These results indicate that a substantial portion of photosynthetic electron transport or respiration generates reductant for nitrate assimilation rather than for carbon fixation or mitochondrial electron transport.     

Indirect estimation of cell mass and substrate concentration using a computer-coupled mass spectrometer

On-line estimation of cell mass and substrate concentration based on exhaust gas analysis was developed. The O₂, CO₂, H₂O, and N₂ contents at the inlet and outlet of fermentor, analyzed by a computer-coupled quadrupole mass spectrometer, were used to calculate the oxygen uptake rate and carbon dioxide evolution rate, and these rates were further used to evaluate cell mass and substrate concentration in a recombinant Escherichia coli fermentation. Cell mass, glucose concentration, specific growth rate, and specific consumption rate of glucose were well estimated by this method; the oxygen uptake rate gave more accurate estimates for these state variables than did the carbon dioxide evolution rate.     

Carbon dioxide inhibition of yeast growth in biomass production

Saccharomyces cerevisiae was grown under aerobic and substrate-limiting conditions for efficient biomass production. Under these conditions, where the sugar substrate was fed incrementally, the growth pattern of the yeast cells was found to be uniform, as indicated by a constant respiratory quotient during the entire growing period. The effect of carbon dioxide was investigated by replacing portions of the nitrogen in the air stream with carbon dioxide, while maintaining the oxygen content at the normal 20% level, so that identical oxygen transfer rate and atmospheric pressure were maintained for all experiments with different partial pressures of carbon dioxide. Inhibition of yeast growth was negligible below 20% CO₂ in the aeration mixture. Slight inhibition was noted at the 40% CO₂ level and significant inhibition was noted above the 50% CO₂, level, corresponding to 1.6 × 10^?2M of dissolved CO₂ in the fermentor broth. High carbon dioxide content in the gas phase also inhibited the fermentation activity of baker's yeast.     

Contribution of the polychaete,Neanthes japonica (Izuka), to the oxygen uptake and carbon dioxide production of an intertidal mud-flat of the Nanakita River estuary,Japan

The benthic oxygen consumption and carbon dioxide production of undisturbed and sieved sediment cores with various values for the biomass of polychaetes collected from the intertidal mud-flat of Nanakita River estuary of Japan were measured simultaneously. The benthic oxygen consumption and carbon dioxide production increased in proportion to the biomass of a dominant polychaete species Neanthes japonica (Izuka). This increase was not explained by the respiration of the animals alone. The residual increase in benthic O₂ and CO₂ fluxes may be due to mineralization processes in the burrow wall and enhanced diffusion caused by the pumping activity of the worms. From the average biomass of polychaetes at the study site, total benthic O₂ and CO₂ fluxes were estimated to be 5.2 mmol·m⁻²·h⁻¹ and 7.3 mmol·m⁻²·h⁻¹, respectively, at 20 ° C. The worms were responsible for 79% of the total O₂ flux and 73% of the total CO₂ flux but the respiration of the worms accounted for only 53% of the total O₂ flux and 36% of the total CO₂ flux. The residual enhanced fluxes were 26% and 37% for the total O₂ and CO₂ fluxes, respectively.     

THE RESPIRATORY QUOTIENT OF FROG NERVE DURING STIMULATION

1. By means of a differential volumeter the increased oxygen consumption and the increased carbon dioxide output of frog nerve during and after stimulation have been observed. 2. Measurements of the R.Q. of nerve by this method are complicated by the retention of carbon dioxide. Attempts were made to avoid this (a) by studying the nerves at high CO₂ tensions to make the retention small and (b) by calculating the amount of CO₂ retained from the carbon dioxide dissociation curve of nerve and applying this value as a correction. 3. The results of both those methods when averaged together give an R.Q. of the excess metabolism of 1.19 and an R.Q. of the resting nerve of 0.97. 4. Observations on the time course of the gas exchange during stimulation indicate a delay in the appearance of the extra carbon dioxide output relative to the oxygen intake. 5. Very similar time curves can be calculated from the diffusion coefficients and the solubilities of the oxygen and the carbon dioxide.     

Anaerobic mineralization of cholesterol by a novel type of denitrifying bacterium

A novel denitrifying bacterium, strain 72Chol, was enriched and isolated under strictly anoxic conditions on cholesterol as sole electron donor and carbon source. Strain 72Chol grew on cholesterol with oxygen or nitrate as electron acceptor. Strictly anaerobic growth in the absence of oxygen was demonstrated using chemically reduced culture media. During anaerobic growth, nitrate was initially reduced to nitrite. At low nitrate concentrations, nitrite was further reduced to nitrogen gas. Ammonia was assimilated. The degradation balance measured in cholesterol-limited cultures and the amounts of carbon dioxide, nitrite, and nitrogen gas formed during the microbial process indicated a complete oxidation of cholesterol to carbon dioxide. A phylogenetic comparison based on total 16S rDNA sequence analysis indicated that the isolated micro-organism, strain 72Chol, belongs to the β2-subgroup in the Proteobacteria and is related to Rhodocyclus, Thauera, and Azoarcus species. Received: 16 July 1996 / Accepted: 5 December 1996     

High productivity and photosynthetic flexibility in a CAM plant

Summary In the annual succulent Mesembryanthemum crystallinum growing in situ, the balance between C₃ and CAM carbon fixation shifted rapidly in response to changes in water availability. When water was plentiful, M. crystallinum fixed carbon dioxide by the C₃ pathway and grew at rates comparable to other C₃ species. Under drought conditions, M. crystallinum fixed carbon by the CAM pathway at an average rate which exceeded 1 nanomole of carbon dioxide per square centimeter of leaf surface per second, a very high rate for a CAM plant.     

Root respiration associated with ammonium and nitrate absorption and assimilation by barley

We examined nitrate assimilation and root gas fluxes in a wild-type barley (Hordeum vulgare L. cv Steptoe), a mutant (nar1a) deficient in NADH nitrate reductase, and a mutant (nar1a;nar7w) deficient in both NADH and NAD(P)H nitrate reductases. Estimates of in vivo nitrate assimilation from excised roots and whole plants indicated that the nar1a mutation influences assimilation only in the shoot and that exposure to NO₃⁻ induced shoot nitrate reduction more slowly than root nitrate reduction in all three genotypes. When plants that had been deprived of nitrogen for several days were exposed to ammonium, root carbon dioxide evolution and oxygen consumption increased markedly, but respiratory quotient—the ratio of carbon dioxide evolved to oxygen consumed—did not change. A shift from ammonium to nitrate nutrition stimulated root carbon dioxide evolution slightly and inhibited oxygen consumption in the wild type and nar1a mutant, but had negligible effects on root gas fluxes in the nar1a;nar7w mutant. These results indicate that, under NH₄⁺ nutrition, 14% of root carbon catabolism is coupled to NH₄⁺ absorption and assimilation and that, under NO₃⁻ nutrition, 5% of root carbon catabolism is coupled to NO₃⁻ absorption, 15% to NO₃⁻ assimilation, and 3% to NH₄⁺ assimilation. The additional energy requirements of NO₃⁻ assimilation appear to diminish root mitochondrial electron transport. Thus, the energy requirements of NH₄⁺ and NO₃⁻ absorption and assimilation constitute a significant portion of root respiration.     

Effect of AMPA on Cerebral Cortical Oxygen Balance of Ischemic Rat Brain

We tested the hypothesis that the excitatory neurotransmitter receptor agonist, alpha amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), would worsen cerebral cortical oxygen supply/consumption balance during focal ischemia. In this study, we compared regional cerebral blood flow, arterial and venous O₂ saturation, O₂ extraction and oxygen consumption of ischemic and AMPA treated ischemic and control regions of rat brain. Ischemia was induced by middle cerebral artery (MCA) occlusion in isoflurane (1.4%) anesthetized Wistar rats. Twenty minutes after MCA occlusion, 10^–5 M AMPA was applied to the ischemic cortex (IC) for a period of 40 min; the fluid was changed every 10 min. After 1 hr of ischemia, animals were sacrificed and regional cerebral blood flow (rCBF) was determined using the C¹⁴-iodoantipyrine autoradiographic technique. Regional arterial and venous oxygen saturation were determined microspectrophotometrically. In control, the cerebral blood flow and oxygen consumption of the IC were significantly lower than the contralateral cortex (rCBF: 46 ± 20 vs. 81 ± 39 ml/min/100g, O₂ consumption: 2.8 ± 1.4 vs. 3.6 ± 1.4 ml O₂/min/100g). 10^–5 M AMPA did not significantly alter regional cerebral blood flow and oxygen consumption of the IC, but did decrease the average venous O₂ saturation of the IC from 50.2 ± 3.9% to 46.7 ± 1.6%. AMPA also significantly increased the frequency of small veins with less than 45% O₂ saturation in the IC (8 out of 56 veins in IC vs. 18 out of 56 veins in AMPA treated IC). Thus, topical application of 10^–5 M AMPA to the ischemic area worsens cerebral O₂ balance and suggests that excitatory amino acids contribute to the degree of cerebral ischemia.     

Effect of Modified Atmosphere Composition on the Metabolism of Glucose by Brochothrix thermosphacta

The influence of atmosphere composition on the metabolism of Brochothrix thermosphacta was studied by analyzing the consumption of glucose and the production of ethanol, acetic and lactic acids, acetaldehyde, and diacetyl-acetoin under atmospheres containing different combinations of carbon dioxide and oxygen. When glucose was metabolized under oxygen-free atmospheres, lactic acid was one of the main end products, while under atmospheres rich in oxygen mainly acetoin-diacetyl was produced. The proportions of the total consumed glucose used for the production of acetoin (aerobic metabolism) and lactic acid (anaerobic metabolism) were used to decide whether aerobic or anaerobic metabolism predominated at a given atmosphere composition. The boundary conditions between dominantly anaerobic and aerobic metabolisms were determined by logistic regression. The metabolism of glucose by B. thermosphacta was influenced not only by the oxygen content of the atmosphere but also by the carbon dioxide content. At high CO₂ percentages, glucose metabolism remained anaerobic under greater oxygen contents.