Μg CO2 Research Articles

The utilisation of a piezoelectric quartz crystal for measuring carbon dioxide in wine

A piezoelectric quartz crystal (PQC) is used for the quantification of carbon dioxide in still white wine. The methodology is discussed in terms of calibration stability and accuracy as a direct consequence of coating amount and absolute quantity of carbon dioxide in the samples. The method is compared, in terms of precision, with the titrimetric method. Standard deviations for several wine samples are, in the titrimetric method, between 4% and 12%, while using the PQC from 1% to 4%, for wines containing 300–1000 μg CO 2cm −3.

Preparation of57Co standard solution and its activity measurement

57Co was produced with high pure nature iron irradiated by 8.5MeV deuterons. TBP-benzene extraction method and anion-exchange method were used to separate and purify it. The purified57Co was prepared into standard solution of about 30 to 50 μg Co2+/ml carrier concentration and about 0.1 mol/l HCl. The specific activity of the standard solution was measured with 4 π β (ppc)-γ coincidence counting method. The final result was 476.82(1±0.42%)Bq/mg.

Mechanisms for carbon and nutrient release and retention in beech forest gaps

Field levels of soil microbial biomass C and N, determined by the chloroform fumigation-extraction method, showed no marked seasonal pattern in limed and unlimed gaps and the surrounding beech stand; average contents were 530, 532 and 674 kg microbial C ha −1 ; and 65, 68 and 87 kg microbial N ha −1 respectively. Liming increased microbial biomass in the stand but had no influence on the size of the microbial pool in the gap. The decrease in microbial biomass in gaps was attributed to a decline of ectomycorrhizal hyphae. Due to the absence of available carbon soil microbial biomass was not a significant nutrient sink following forest disturbance. In situ N mineralization at these sites could not be explained by fluctuations in microbial N. Laboratory measurements of CO 2 evolution from soil samples, which were in good agreement with field CO 2 measurements, indicated a decline in easily decomposable soil organic matter during the growing season. High metabolic quotients (μg CO 2 -C mg C mic −1 d −1 ) of the microflora in gaps indicated inefficient energy use

Canopy photosynthesis of CO2‐enriched lettuce (Lactuca sativa L.). Response to short‐term changes in CO2, temperature and oxides of nitrogen

SUMMARYThe canopy net photosynthesis (Pn) of lettuce (Lactuca sativa L. ev.‘Ambassador’) was analyzed under controlled conditions simulating the winter glasshouse atmosphere. Prior to measurements the plants were grown in CO2‐enriched air of 1000 μmol mol−1, at a photosynthetic photon flux density (PPFD) of 280 μmol m2 s−1 (400–700 nm) and a day/night air temperature of 16/13 °C.Short‐term changes in CO2 concentration significantly changed the initial gradient of the photosynthetic response to incident PPFD. Maximum photosynthetic efficiency of the crop increased from 0·041 mol CO2 mol photons−1 (equivalent to 8·2 μg CO2 J−1 and 9·4% on an energy basis) at 350 μmol mol−1 to 0·055 mol CO2 photons−1 (10·9 μg CO2 J−1 and 12·7% on an energy basis) at 1000 μmol mol−1. Transfer from low to high CO2 also lowered the light compensation point, but did not affect dark respiration. The large response of Pn to transient changes in CO2 indicated that the lettuce canopy did not acclimate to growth in 1000 μmol CO2 mol−1, in contrast with the effect of growth in high CO2on Pn in single mature leaves reported earlier.A reduction in air temperature from 16 to 6 °C at a concentration of 1000 μmol CO2 mol−1 halved the rate of dark respiration and reduced the light compensation point, but had no direct effect on the maximum efficiency with which the crop utilized light. Subsequently at low light (below 200 μmol m−1 s−1) Pn was greater at 6 than 16 °C. Between a PPFD of 250 and 300 μmol m−2 s−1 canopy Pn was similar at all temperatures.Addition of 2·0 μmol mol−1 nitric oxide to an atmosphere of 1000 μmol CO2 mol−1 caused a rapid and reversible reduction of canopy Pn, which was greater at the lowest temperatures. The average inhibition was 6·6 at 16 °C and 28·8% at 6 °C; this was not explained by differences in the rate of pollutant uptake, which was less in the cooler conditions.The results are discussed in relation to development of optimal growing conditions for production of glasshouse lettuce at low light and low temperature during winter in the UK.

Effects of Light and CO2 on Net Photosynthesis Rates of Stands of Aubergine and Amaranthus

Net photosynthetic rates per unit ground area for plant stands of Solanum melongena L. var. esculentum (aubergine) and Amaranthus caudatus L. var. edulis (grain amaranth) were measured over 10 min intervals in an airtight, glass, controlled-environment cabinet for a range of light flux densities provided by the diurnal variation in daylight. Light response curves for photosynthesis of stands, grown at ambient CO2 concentration, were defined at 400, 800 and 1200 vpm CO2.Light compensation points for these stands were around 20-30 J m-2 s-1 and decreased slightly at higher CO2 concentrations. For aubergine, a C3 species, the short-term effects of CO2 enrichment were to increase the initial slope as well as the asymptote of the light response curve, reducing light saturation at moderate to high light flux densities; but for amaranthus, a C4 species, saturation was less apparent and CO2 enrichment scarcely increased photosynthesis except at light flux densities above 150 J m-2 s-1.The canopies intercepted 93-98% of incident light. The efficiency of utilization of intercepted light in photosynthesis (μg CO2 J-1) increased from zero at the light compensation point to a maximum at an optimum light flux density of about 100 J m-2 s-1 (the optimum rose a little with CO2 enrichment) and decreased slightly with further increase in light. Maximum utilization efficiencies at 400 vpm CO2 were 8-9 μg CO2 J-1. Enrichment to 1200 vpm did not affect the peak utilization efficiency of the C4 amaranthus, but increased that aubergine to 12·2 μg CO2 J-1 (equivalent to some 14% when using the heat of combustion of plant dry matter to convert to the dimensionless form). This is among the highest recorded efficiencies of light utilization for stands, and relates to the exceptionally favourable environment, with optimal control of CO2 concentration, humidity, temperature, water supply and mineral nutrition.

Effects of temperature and ageing on CO 2 exchange of pods of oilseed rape ( Brassica napus)

Net CO 2 exchange of the upper pods of Brassica napus L., cv. Marnoo,was measured in the light ( P n) and in the dark ( R d) using a portable photosynthesis system. Dark respiration was measured in a blacked-out chamber during the day. Measurements spanned the period from 23 days after full flower ( daff 23), when pods were fully grown and seeds were immature and green, to daff 50 when pods were yellow-brown and seeds were ripe. Daylight photosynthesis decreased linearly from ca. 400 μg CO 2 pod −1 h −1 at daff 25 to 0 at ca. daff 46, but marked deviations from trend were negatively associated with temperature in the range 20°C to 40°C, at the time of measurement. Dark respiration increased with temperature from ca. 80 μg CO 2 pod −1 h −1 at 20°C to 400 μg CO 2 pod −1 h −1 at 40°C. The relationship of R d with temperature was adequately described by a Q 10 of 2.3. Regression analyses suggested that changes in P n during pod-filling were partly attributable to effects of temperature on the respiratory component of P n, and partly to ageing. The importance of temperature in the carbon balance of the pods decreased with age. It is hypothesized, on the basis of these and other data, that high temperature has a negative effect on pod and seed growth, and also duration of pod-filling, through direct effects on the carbon balance of pods.

Microbial carbon turnover in beech forest soils worked by Aporrectodea caliginosa (Savigny) (Oligochaeta:Lumbricidae)

Effects of the endogeic earthworm species Aporrectodea caliginosa (Savigny) on the edaphic microflora were studied in six German beech forest soils using the fumigation-extraction method. The following response variables were measured: biomass (C mic), C incorporation from 14C-labelled beech leaf litter ( 14C mic) and two metabolic quotients (qCO 2: μg CO 2-C μg −1 C mic h −1; q 14CO 2: μ 14CO 2-C μg −1 14C mic h −1). After removing the earthworms from the experimental containers at day 21, the experiment ran for a further 21 days to study the long-term alteration ofmicrobial performance in earthworm worked soils. At day 21, C mic and 14C mic were reduced in the earthworm treatments of five soils and qCO 2 and q 14CO 2 were increased in all soils. Effects on C mic and 14C mic were not correlated to each other. The day 21 effects of A. caliginosa on C mic and qCO 2 declined, while the stimulation of q 14CO 2 increased with increasing soil acidity. Day 42 measurements showed that the long-term effects of A. caliginosa on microbial C use were highly soil specific and were opposite to the effects measured at day 21 in most of the soils. It is concluded from these results that A. caliginosa alters the biomass and the metabolic activity of the edaphic microflora over a wide range of soils, that these alterations are highly soil and resource specific and that the microbial C turnover in soils freshly worked by A. caliginosa is significantly different from the microbial C turnover in aged casts and burrows.

Characterization of a substrate-induced respiration method for measuring fungal, bacterial and total microbial biomass on plant residues

A substrate-induced respiration (SIR) method is described to measure the contributions of fungi and bacteria to total glucose-induced microbial respiration on plant residues of differing composition. Relationships between fungal, bacterial and total SIR and biomass were used to develop regression equations for predicting microbial biomass C from measures of SIR. Total SIR rates (100–2000 μg CO 2-C g −1 h −1) and biomass-specific SIR rates (64–72 ng CO 2-C h −1 μg −1 biomass C) from plant residues were considerably greater than those calculated from the literature for soils. Results of longer term decomposition studies indicate that the C:N ratios of plant residues through time account for the greatest amount of the variation in total SIR. Annual decomposition rate constants ( k) for plant residues were positively correlated ( r 2=0.99) to overall mean estimates of total SIR. The plant residue SIR method has advantages over conventional direct count methods because it distinguishes a physiologically active component of the microbial biomass. Furthermore, it allows separation of fungal and bacterial components that may aid in understanding microbial controls on plant residue decomposition.

Application of respiration- and adenylate-based soil microbiological assays to deep subsurface terrestrial sediments

Nine samples were aseptically collected from subsurface sediments at depths of 10–436 m at a site in South Carolina near the U.S. Department of Energy's Savannah River Plant. The sediment samples were characterized physically, chemically and microbiologically. Subsurface microbial communities were characterized in various ways. Standard plate counts of the sediment samples resulted in variable densities of culturable bacteria (<10 2 to 4.0 × 10 4 colony-forming units g −1 dry wt). Basal respiration values ranged from 0 to 1.08 μg CO 2 g −1 dry wt h −1; substrate-induced respiration (SIR) biomass C values ranged from 0 to 40.5 μg biomass C g −1 dry wt; the ATP values ranged from < 1 to 127pmol g −1 dry wt; and adenylate energy charge (AEC) values ranged from 0.23 to 0.76. Metabolic quotients (respiration rate: biomass C) ranged from 0.000516 to 0.0239 μg CO 2-Ch −1: μg biomass C. Respiration rates were correlated with both AEC ( r = 0.860) and ATP ( r = 0.768). Ratios of biomass C to total organic carbon (TOC) for four samples for which TOC data were available averaged 4.96 mg biomass C g −1 organic C.

Application of eco-physiological quotients ( qCO 2 and qD) on microbial biomasses from soils of different cropping histories

Metabolic quotients for CO 2C ( qCO 2C) and microbial-C-loss ( qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO 2C (unit CO 2C unit −1 C mic h −1) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO 2 qCO 2CC as compared to 0.645 μg CO 2C of microbial biomasses from 19 CR systems. The 1.7 times higher CO 2C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level. In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher ( P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils). These differences were not related to soil texture, C org or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed.

A substrate-induced respiration (SIR) method for measurement of fungal and bacterial biomass on plant residues

The substrate-induced respiration (SIR) method was modified and adapted to measure fungal, bacterial and total microbial contributions to glucose-induced respiration and the potentially active microbial biomass on decaying plant residues of differing composition. Decomposing residues from natural and agricultural ecosystems were chopped and sieved to include the > 1 mm fraction for routine SIR analyses on a continuous flow-through respiration system. SIR procedures were optimized for sample size (0.5–1.0g dry wt), glucose concentration (80mg g −1), antibiotic concentrations (16mg streptomycin g −1; 80 mg cycloheximide g −1), total solution volume (5 ml), antibiotic preincubation conditions (12 h at 4 C), and total assay time following glucose addition (2–3 h). Analyses of antibiotic selectivities for target populations were made from agar plate culture experiments with mixed residue-microbial populations under in vitro and in situ exposure to antibiotics. The results support those concentrations optimized by SIR and emphasize the importance of independent analysis of antibiotic selectivity. Measures of fungal, bacterial and total SIR (μg CO 2-C g −1 dry residue h −1) were linearly correlated ( P<0.001) with biovolume-derived estimates of total ( r 2 = 0.91) and FDA-active ( r 2 = 0.93) fungal biomass, bacterial biomass ( r 2 = 0.87) and total microbial biomass ( r 2 = 0.91), respectively. Fungal to bacterial SIR ratios (1.6:1 to 2.5:1) emphasize the dominance of fungi in the early stages of plant residue decay (⩽ 3 weeks). Plant residue SIR rates were 38–600 times greater than those of soils. Biomass specific SIR rates from plant residues (72 ng CO 2 -Ch −1 μg −1 biomass-C) were 5– 6 times higher than those reported from soil SIR. These findings suggest both a larger microbial biomass as well as a much higher proportion of physiologically active microorganisms on plant residues as compared to soils.

The influence of micropropagation on yield components, dry matter partitioning and gas exchange characteristics of strawberry

Asexual progeny of micropropagated (MP) plants of the cultivars ‘Earliglow’ and ‘Redchief’ had higher plant densities and yields than conventionally propagated (CP) plants in matted rows. MP plants partitioned 9–10% less of their total dry matter to leaf tissue. Micropropagated ‘Redchief’ increased its allocation to crowns and flower trusses; ‘Earliglow’ to fruit. Leaf area crown −1 was reduced in MP ‘Earliglow’ (49%) and ‘Redchief’ (55%), and yield crown −1 was lower (32%) in MP ‘Redchief’, but not ‘Earliglow’. Net photosynthetic rate (mg CO 2 dm −2 h −1 or μg CO 2g −1 dry wt. h −1 was greater in MP ‘Earliglow’ but not in ‘Redchief’. Stomatal conductance was higher in MP ‘Earliglow’, while mesophyll conductance was unchanged in both cultivars. MP plants of both cultivars had more stable PN rates across leaf densities than CP ones.

Seasonal changes in the photosynthetic response ofMercurialis perennis plants from different light regime conditions

Curves relating net photosynthetic rate to irradiance [P(I) curve relation] were estimated and analysed inMercurialis perennis L. plants stemming from three forest (spruce, beech and ash) stands with different tree leaf canopy development and different light regime. The saturating irradiance (Is) reached the highest values in plants of all three stands in spring (spruce forest: 438 W m−2, beech forest: 440 W m−2 and ash forest: 367 W m−2), it declined sharply in the middle of the growing season (283, 285 and 297 W m-2, respectively) and this Is level persisted until autumn. A pronounced dynamics in plants from spruce and beech forests made itself manifest also in the adaptation (Ia) and compensating (Ic) irradiances, respectively. After a sudden decline in summer, values in autumn were close to those of the vernal season. The most pronounced parameter, which optimally expressed the adaptation ofMercurialis perennis to various light conditions, was the photosynthetic efficiency (α) calculated as the slope of the linear part of the curve relating net photosynthetic rate to irradiance. At the time of the highest PN sat. value in course of the growing season (August) (spruce forest: 100, beech forest: 98.7 and ash forest: 85.8 μg CO2 m−2 s−1), RD was in its minimum; in autumn PN sat. reached the lowest values which corresponded to the most intensive RD. It was found thatMercurialis perennis plants stemming from forest stands with different light conditions did not make use equally of the altering light conditions in the course of the growing season. By the underlying analysis of P(I) curves this rhizomatous perennial herb (geophyte) may be characterized as a shade tolerant species.

CO2 Fixation in Alfalfa and Birdsfoot Trefoil Root Nodules and Partitioning of 14C to the Plant1

Nonphotosynthetic CO2 fixation by root nodules of legumes may provide carbon skeletons for assimilation of symbiotically fixed N2. However, the products formed by this process and their physiological significance in perennial legumes is poorly understood. Therefore, the objectives of this study were to determine if nonphotosynthetic CO2 fixation by root nodules contributes carbon for the assimilation of fixed N2 in alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) and if assimilation products are partitioned to different plant organs. Effective alfalfa nodules excised from or attached to roots had apparent 14CO2 fixation rates of 50 to 80 μg CO2 kg‐1 s‐1 (dry weight) at 0.0012 to 0.0038 mole fraction CO2. Nodule CO2 fixation rates increased six‐ to seven‐fold as ambient CO2 was raised from 0.0038 to 0.0663 mole fraction. These rates were double to triple those of comparably treated nodules of ineffective alfalfa and those of birdsfoot trefoil. Respiration rates of nodules (3 to 4 mg CO2 kg‐1 s‐1) were 10 to 100‐fold higher than 14CO2 fixation rates of nodules. This finding suggests that attached nodules normally function at saturating CO2 levels and may fix up to 1600 μg CO2 kg‐1 s‐1 when concurrent 14C export to roots and shoots is accounted for. Pulse chase experiments with 14CO2 combined with nodule and xylem sap analysis demonstrated the initial products of root and nodule CO2 fixation were organic acids. However, the export of fixed 14C from effective nodules was primarily in the form of amino acids. In contrast, nodule and/or root fixed 14C in ineffectively nodulated alfalfa and denodulated effective alfalfa and birdsfoot trefoil was transported primarily as organic acids. Aspartate, asparagine, alanine, glutamate, and glutamine were the most heavily labeled compounds in the amino acid fraction of both effective alfalfa and birdsfoot trefoil nodules exposed to 14CO2. By contrast, asparate, asparagine, and glutamine were the predominantly labeled amino acids in xylem sap collected from nodulated effective roots exposed to 14CO2. The occurrence of nodule CO2 fixation in alfalfa and birdsfoot trefoil and the export of fixed carbon as asparagine and aspartate to roots and shoots is consistent with a role for CO2 fixation by nodules in providing carbon skeletons for assimilation and transport of symbiotically fixed N2.

The influence of irradiance and external CO 2-concentration on photosynthesis of different tomato genotypes

With 4 genotypes of tomato, irradiance and CO 2-response curves of net photosynthesis were analysed by means of curve fitting. Estimated values of the light compensation point I c showed small but significant differences between the genotypes, the overall value being in the order of 8 W m −2. The photochemical efficiency (α n) and the maximum net photosynthesis per unit leaf area basis ( P nm) reached the highest values for ‘F6 IVT’ (13.3 μg CO 2 J −1 resp. 0.549 mg CO 2 m −2 s −1), the lowest value of α n with ‘Bonabel’ (9.9 μg CO 2 J −1), and the lowest value of P nm with ‘PI 114969’ (0.424 mg CO 2 m −2 s −1). The CO 2-compensation point ( C c) was relatively high (177–245 mg m −3). ‘F6 IVT’ demonstrated the highest value of C c, the lowest carboxylation efficiency and the highest maximum rate of net photosynthesis. The results clearly demonstrate that the latter genotype requires a much higher external CO 2-concentration than the other genotypes in order to exhibit the highest rate of net photosynthesis.

The decomposition of organic compounds in soil

The course of the CO2 evolution rates of soil samples has been followed continuously in the absence and in the presence of various organic compounds. After an incubation period of 300 hours at 13 and 20°C the CO2 evolution from pasture soil (containing 1.76% soil organic carbon) amounted to 0.13 and 0.44μg CO2−C.g soil−1.h−1, respectively. For arable soil (containing 1.20% soil organic carbon) the rates amounted to 0.04 and 0.09 μg CO2−C.g soil−1.h−1, respectively.

Primary productivity of Zostera muelleri Irmisch ex Aschers. In Westernport Bay (Victoria, Australia)

From simultaneous measurements of photosynthetically active radiation (PAR) and gas exchange under both exposed and submerged conditions in situ in Westernport Bay it is shown that the response of photosynthesis by Zostera muelleri ex Aschers. to light can be approximated by a Blackman limiting response curve. The maximum rate of net photosynthesis under submerged conditions is ca. 230 μg CO 2 m −2 leaf area s −1, this rate being reduced by about one-third on exposure. Under submerged conditions the light compensation point corresponds to a photon flux density of 25 μmol m −2s −1, and photosynthesis becomes light-saturated at a photon flux density of about 120 μmol m −2s −1. Estimates of net primary production for each month of the year were calculated from the light response curve and solar radiation records. Photosynthesis is shown to be light saturated for the greater part of each day, and the seasonal variation in net primary production is therefore influenced strongly by day length. Annual net primary production by Z. muelleri amounts to 4.3 g dry matter g −1 dry wt. of plant (17.2 g dry matter g −1 dry wt. of leaf), indicating a turnover of about four times per year. For the whole of Westernport Bay, annual net primary production by Z. muelleri, which covers an area of 38 km 2, is estimated to be 16.3 × 10 9 g dry wt. Taking into account primary production by other species of seagrass and benthic algae, which together cover an area of 181 km 2, it is evident that Westernport Bay is indeed a highly productive ecosystem.

A comparison of four methods for measuring respiration in organic material

Four methods for measurement of respiration (CO 2 evolution) were compared on uniformly prepared, birch forest-floor organic matter; the methods included infrared gas analysis (i.r.g.a.), gas chromatography (g.c.), KOH absorption of CO 2 (b.a.) and the Gilson respirometer. Respiration estimates were made at a single temperature and also at variable temperatures at constant moisture contents. The i.r.g.a. and b.a. methods gave maximum estimates for respiration; the g.c. gave lowest, with the Gilson intermediate. Lower estimates for the g.c. are attributed to the closed system employed, which included no means of increasing gas diffusion (such as a KOH-CO 2 sink or continuous gas flow) out of the sample into the unoccupied space of the respiration chamber. At 25°C, the minimum sensitivity of the g.c. and Gilson were 3.8 and 3.6 μg CO 2, respectively. The minimum sensitivity of the b.a. method (44 μg CO 2) could have been improved with use of a micro-liter burette for titrations. The least minimum sensitivity, 0.31 μg CO 2, was attained with the i.r.g.a. Conditions under which any of the techniques may be used to estimate respiration should be carefully worked out. The relationship between sample size, gas flow rate (open system), chamber atmosphere composition (closed system), and chamber design should be established with sufficient confidence so that stimulation of respiration by excessive gas flow rate, or exhaustion of O 2 or CO 2 inhibition through extended chamber closure does not adversely affect respiration estimates.