土壤-玉米系统中土壤呼吸强度及各组分贡献

用特殊设计的气体采集箱法对玉米生长期间潮土呼吸强度进行了测定。结果表明,施用150kgNhm^-2的裸地土壤CO2累积排放量是294g C m^-2,约为种植玉米土壤的一半。用根去除法测得的玉米对土壤呼吸的贡献率,苗期小于20％,拔节到收获期波动在30％-70％之间,全生长期平均为46％。玉米生长期间因土壤有机碳分解而释放出的CO2总量为2．94MgChm^-2,大约是0—40cm土层中土壤有机碳总储存量的8％,因此需要输入7．35Mghm^-2的碳含量40％的作物残留物才能平衡土壤中有机碳的损失,约为玉米收获时残留于土壤中根量的一倍,但与残留根量及玉米生长期间根系分泌到土壤的有机物量的总和相当,因此土壤中有机碳总体处于平衡状态。在玉米生长期间,施用氮肥可使土壤CO2排放量降低10％。土壤排放CO2主要受土壤温度的影响,温度效应Q10为1．90-2．88。     

氮添加对沙质草地微生物呼吸与根系呼吸的影响

土壤呼吸可以细化为根系呼吸和微生物呼吸,二者对氮添加的响应有所不同.本文以科尔沁沙质草地为研究对象,探讨氮添加对土壤CO₂排放的影响,并细化为微生物呼吸和根系呼吸的响应特征.结果表明: 在观测期(5—10月),土壤呼吸、微生物呼吸月动态均呈先升高后降低的趋势;微生物呼吸是土壤呼吸的主要贡献者,占82.6%;观测期内根系呼吸贡献率随月份而变化,根系呼吸贡献率两个峰值分别出现在5月(占49.4%)和8月(占41.9%),6个月的平均贡献率为17.4%;在10 ℃条件下,根系呼吸较微生物呼吸对氮添加的响应更为敏感,微生物呼吸速率在氮添加后降低了3.9%,而根系呼吸降低了17.7%;氮添加提高了土壤呼吸、微生物呼吸温度敏感性Q₁₀值,也提高了二者对土壤水分变化的敏感程度.     

Studies on enhanced post-illumination respiration in microalgae

The extent of enhanced post-illumination respiration (EPIR)has been investigated in a number of microalgae. Respirationrates, as determined by O₂ consumption, were enhanced (in allbut one case) by 50–140% following pre-exposure to highphoton flux compared to rates obtained for steady-state darkrespiration. The extent of EPIR was dependent more on photonflux than on duration of exposure, although the latter did havesome effect. In Isochrysis galbana and Chaetoceros calcitrens,EPIR effects were also demonstrated using [¹⁴C]CO₂ evolution.In I.galbana, release of CO₂ from cells pre-exposed to a periodof high photon flux was most rapid from carbohydrate and low-molecular-weightmetabolites. Data obtained from Thalassiosira weisflogii indicatethat cells grown at low photon flux are more susceptible toEPIR than those grown under high photon flux. These resultsare discussed in the context of various hypotheses that havebeen proposed regarding the mechanism of EPIR effects. ⁸Present address: RIVM-LWD, PO Box 1, 3720 BA Bilthoven, TheNetherlands     

CO2浓度升高和施氮条件下小麦根际呼吸对土壤呼吸的贡献

依托FACE技术平台,采用稳定13C同位素技术,通过将小麦(C3作物)种植于长期单作玉米(C4作物)的土壤上,研究了大气CO2浓度升高和不同氮肥水平对土壤排放CO2的δ13C值及根际呼吸的影响.结果表明:种植小麦后土壤排放CO2的δ13C值随作物生长逐渐降低,CO2浓度升高200 μmol·mol-1显著降低了孕穗、抽穗期(施氮量为250 kg·hm-2,HN)与拔节、孕穗期(施氮量为150 kg·hm-2,LN)土壤排放CO2的δ13C值,显著提高了孕穗、抽穗期的根际呼吸比例.拔节至成熟期,根际呼吸占土壤呼吸的比例在高CO2浓度下为24％～48％ (HN)和21％ ～48％ (LN),在正常CO2浓度下为20％ ～36％ (HN)和19％～32％(LN).不同CO2浓度下土壤排放CO2的δ13C值和根际呼吸对氮肥增加的响应不同,CO2浓度与氮肥用量在拔节期对根际呼吸的交互效应显著.     

Transformation of 2,4,6-trinitrotoluene during oxygen and nitrate respiration in Pseudomonas fluorescens

A study of the metabolic pathway and the rate of 2,4,6-trinitrotoluene (TNT) transformation depending on the nature of the electron acceptor in the electron transport chain of Pseudomonas fluorescens B-3468 revealed that the first reaction of nitroreduction of TNT resulting in formation of 2-amino-4,6-dinitrotoluene (2A) and 4-amino-2,6-dinitrotoluene (4A) became more active in case of nitrate respiration as compared to oxygen respiration; a TNT decrease was 100 and 66%, respectively. The same tendency but much more pronounced was observed at the next stage of nitroreduction that lead to 2,4-diamino-6-nitrotoluene (2,4DA). On the contrary, aerobic conditions are more preferable for the subsequent destruction of 2,4DA. Thus monoamino derivatives, 2A and 4A, predominated under anaerobic conditions, whereas 2,4DA under anaerobic ones (85 and 69% of the total nitrogen-containing metabolites), respectively. Phloroglucinol and pyrogallol accumulated in the culture liquid when the bacteria were grown on a medium containing 2,4DA as a sole source of nitrogen. Their role as intermediates was proved by the results obtained by studying oxidative activity of the cells grown in the presence of 2,4DA and phloroglucinol.     

Proton electrochemical gradient and rate of controlled respiration in mitochondria

The correlation between deltamuH, the proton electrochemical potential difference, and the rate of controlled respiration is analyzed. deltamuH (the proton concentration gradient) is measured on the distribution of [3H]acetate, and deltapsi (the membrane potential) on the distribution of 86Rb+, 45Ca2+ and [3H]triphenylmethylphosphonium used either alone or simultaneously. The effects of the addition of ADP + hexokinase (state-3 ADP) and of carbonylcyanide trifluoromethoxyphenylhydrazone (state-3 uncoupler) on respiration and deltamuH are not equivalent: the uncoupler depresses deltamuH more than ADP at equivalent respiratory rates. The effects of the additions of nigericin-valinomycin and of ionophore A23187 (state-3 cation transport) and of carbonylcyanide trifluoromethoxy-phenylhydrazone (state 3-uncoupler) on respiration and deltamuH are also not equivalent: the uncoupler depresses deltamuH more than A23187 and nigericin + valinomycin at equivalent respiratory rate. A23187 is very efficient in stimulating respiration with negligible deltamuH changes.     

Factors influencing respiration data in freshwater sediment

Sediment respiration (oxygen consumption and CO₂ evolution) was measured in freshwater sediment samples using both flask- and core-microcosms, and the estimates were compared. Oxygen consumption data were also compared in flask-microcosms constructed with sediment samples of different masses, sediment: water ratios, and storage times. Furthermore, sediment respiration was examined under different incubation conditions of temperature and agitation. O₂ consumption was markedly higher in flask-microcosms than in sediment core-microcosms, when compared on a per g dry weight basis. However, when the results were expressed as O₂ consumed per unit surface area, the values were more similar. CO₂ evolution was less dependent on surface area as evidenced by similar CO₂ values per g sediment in both microcosms. In addition, the effect of sediment mass on O₂ consumption and CO₂ evolution was examined. Both O₂ consumption and CO₂ evolution (expressed as µmole g^–1 dry weight sediment) decreased significantly with increasing sediment mass between 3 and 12 g dry weight. Maximum O₂ consumption per unit headspace was measured when a wet sediment mass between 10.0 and 20.0 g was used in the flask-microcosms. It was also shown that the sediment: water ratio, agitation, incubation temperature, and previous storage time of sediment all affected the respiration estimates. Initial O₂ consumption and CO₂ evolution in flasks were significantly higher in flasks with a decreased sediment: water ratio (1:1 versus 1:2), increased flask agitation, and increased incubation temperature (15 °C versus 5 °C). Also, respiration decreased significantly over the first 100 days of storage at 4 °C.     

Effect of respiratory apparatus on respiration

A mouthpiece plus noseclip (MP + NC) is frequently used in performing measurements of breathing patterns. Although the effects the apparatus exerts on breathing patterns have been studied, the mechanism of the changes it causes remains unclear. The current study examines the effects on respiratory patterns of a standard (17-mm-diam) MP + NC during room air (RA) breathing and the administration of 2 and 4% CO2 in normal volunteers and in patients 2-4 days after abdominal operation. When compared with values obtained with a noninvasive canopy system, the MP + NC induced increases in minute ventilation (VE), tidal volume (VT), and mean inspiratory flow (VT/TI), but not frequency (f) or inspiratory duty cycle, during both RA and CO2 administration. The percentage increase in VE, VT, and VT/TI caused by the MP + NC decreased as the concentration of CO2 increased. During RA breathing, the application of noseclip alone resulted in a decrease in f and an increase in VT, but VE and VT/TI were unchanged. The changes were attenuated during the administration of 2 and 4% CO2. Reducing the diameter of the mouthpiece to 9 mm abolished the alterations in breathing pattern observed with the larger (17-mm) diameter MP.     

Effect of a single breath of 100% oxygen on respiration in neonates during sleep

To determine the effect of a single breath of 100% O2 on ventilation, 10 full-term [body wt 3,360 +/- 110 (SE) g, gestational age 39 +/- 0.4 wk, postnatal age 3 +/- 0.6 days] and 10 preterm neonates (body wt 2,020 +/- 60 g, gestational age 34 +/- 2 wk, postnatal age 9 +/- 2 days) were studied during active and quiet sleep states. The single-breath method was used to measure peripheral chemoreceptor response. To enhance response and standardize the control period for all infants, fractional inspired O2 concentration was adjusted to 16 +/- 0.6% for a control O2 saturation of 83 +/- 1%. After 1 min of control in each sleep state, each infant was given a single breath of O2 followed by 21% O2. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), alveolar O2 and CO2 tension, O2 saturation (ear oximeter), and transcutaneous O2 tension were measured. VE always decreased with inhalation of O2 (P less than 0.01). In quiet sleep, the decrease in VE was less in full-term (14%) than in preterm (40%) infants (P less than 0.001). Decrease in VE was due primarily to a drop in VT in full-term infants as opposed to a fall in f and VT in preterm infants (P less than 0.05). Apnea, as part of the response, was more prevalent in preterm than in full-term infants. In active sleep the decrease in VE was similar both among full-term (19%) and preterm (21%) infants (P greater than 0.5). These results suggest greater peripheral chemoreceptor response in preterm than in full-term infants, reflected by a more pronounced decrease in VE with O2. The results are compatible with a more powerful peripheral chemoreceptor contribution to breathing in preterm than in full-term infants.     

Manganese depresses rat heart muscle respiration

It has previously been reported that moderately high dietary manganese (Mn) in combination with marginal magnesium (Mg) resulted in ultrastructural damage to heart mitochondria. Manganese may replace Mg in biological functions, including the role of enzyme cofactor. Manganese may accumulate and substitute for Mg during the condition of Mg-deficiency. The objective of the current study was to determine whether high Mn alters heart muscle respiration and Mg-enzyme activity as well as whole body Mn retention under marginal Mg. An additional objective was to determine whether high Mn results in increased oxidative stress. In experiment 1: forty-eight rats were fed a 2 x 3 factorial arrangement of Mn (10, 100, or 1000 mg/kg) and Mg (200 or 500 mg/kg). In experiment 2: thirty-two rats were fed one of four diets in a 2 x 2 factorial arrangement of Mn (10 or 250 mg/kg) and Mg (200 or 500 mg/kg). In experiment 3: thirty-two rats were fed one of four diets in a 2 x 2 factorial arrangement of Mn (10 or 650 mg/kg) and Mg (200 or 500 mg/kg). In experiment 2, high Mn and marginal Mg reduced (P<0.05) oxygen consumption of left ventricle muscle. Marginal Mg, but not Mn, reduced (P<0.05) activity of sarcoplasmic reticulum calcium-ATPase enzyme. Dietary Mg had no affect on (54)Mn kinetics, but high dietary Mn decreased (P<0.01) absorption, retention, and rate of excretion of (54)Mn. Neither cellular stress, measured by Comet assay, nor antioxidant activities were increased by high Mn. A strong interaction (P<0.001) between increasing Mn and adequate Mg on hematology was observed. These results confirm previous research in swine that high Mn alters myocardial integrity as well as function, but not as a result of altered calcium transport or oxidative stress.     

Mapping meristem respiration of Prunus persica (L.) Batsch seedlings: potential respiration of the meristems, O2 diffusional constraints and combined effects on root growth

Root system architecture partially results from meristem activities, which themselves depend on endogenous and environmental factors, such as O2 depletion. In this study, meristem respiration and growth was measured in the root systems of three Prunus persica (L.) Batsch seedlings. The spatial distribution of meristem respiration within the root system was described, and the relationship between the respiration rates and meristem radii was analysed, using a model of radial O2 diffusion and consumption within the root. Histological observations were also used to help interpret the results. Respiration rates were linearly correlated to the root growth rates (rho 2 = 0.9). Respiration reached values greater than 3.5 x 10(-13) mol O2 s-1 for active meristems. The taproot meristem consumed more O2 than the rest of the entire root system meristems. Similarly, the first order lateral meristems used more O2 than the second order ones. A near hyperbolic relationship between respiration rates and meristem radii was observed. This can be explained by a model of radial O2 diffusion and consumption within the root. Therefore, only one maximum potential respiration rate and one O2 diffusion coefficient was estimated for all the meristems.     

The physiological significance of cyanide-resistant respiration in higher plants

Abstract A brief survey of the biochemistry of the alternative oxidative pathway (‘cyanide-resistant respiration’) and its occurrence in vivo is given. Several hypotheses about the physiological significance of the alternative chain are discussed. These include a role in (1) heat production, (2) fruit ripening, (3) respiration of plants that contain high levels of cyanogenic glycosides, producing HCN upon wounding, (4) oxidation of NADH that is produced by various causes in excess of that required for ATP production, (5) ion uptake, and (6) osmoregulation. In intact roots of higher plants, the activity of the alternative pathway is more active when less carbohydrate is required for assimilation of N (NH+₄ NO-₃ or N₂) and is less active in those when carbohydrates are being stored in a storage organ or when the availability of photosynthate is reduced. An increase in carbohydrate requirement for osmoregulation is also correlated with decreased alternative chain activity. It is concluded that the alternative pathway in roots plays an important role in oxidation of sugars which are not required for carbon skeletons, energy production for growth and maintenance processes, osmoregulation or storage. However, the significance of this role may vary in different tissues and physiological states.     

Cyanide-resistant respiration in light- and dark-grown soybean cotyledons

Measurements of respiration were made on intact tissue and mitochondria isolated from soybean (Glycine max [L.] Merr. cv `Corsoy') cotyledons from seedlings of different ages grown in light and darkness. Effects of cyanide (KCN) and salicylhydroxamic acid (SHAM) on O₂ uptake rates were determined. O₂ uptake was faster in light-grown tissue and was inhibited by both KCN and SHAM in all except light-grown tissue older than 9 days. Both inhibitors stimulated O₂ uptake in tissues more than 9 days old. Mitochondria in which O₂ uptake was coupled to ATP synthesis were isolated from all tissues. O₂ uptake by mitochondrial preparations from light- and dark-grown cotyledons was equally sensitive to KCN. Similarly, age did not affect KCN sensitivity, but sensitivity to SHAM declined with age both in the presence and absence of KCN. Estimated capacities of the cytochrome and alternative pathways of the mitochondrial preparations indicated considerably larger cytochrome than alternative pathway capacities. The cytochrome pathway capacities paralleled the state 3 mitochondrial respiration rates, which increased from day 5 to day 7 then declined thereafter. The alternative pathway capacities were not affected by light. The uncoupler, p-trifluoromethoxycarbonylcyanide phenylhydrazone (FCCP), increased the flow of electrons through the cytochrome pathway at the expense of flow through the alternative pathway in isolated mitochondria. However, the combined capacities did not exceed the rate in the presence of FCCP. The results are interpreted to indicate that the stimulation of respiration by KCN and SHAM observed in the 12-day-old green cotyledons and previously observed in older soybean leaves is not explained by characteristics of the mitochondria.     

Zn2+ inhibits alpha-ketoglutarate-stimulated mitochondrial respiration and the isolated alpha-ketoglutarate dehydrogenase complex

Intracellular free Zn(2+) is elevated in a variety of pathological conditions, including ischemia-reperfusion injury and Alzheimer's disease. Impairment of mitochondrial respiration is also associated with these pathological conditions. To test whether elevated Zn(2+) and impaired respiration might be linked, respiration of isolated rat liver mitochondria was measured after addition of Zn(2+). Zn(2+) inhibition (K(i)(app) = approximately 1 micrometer) was observed for respiration stimulated by alpha-ketoglutarate at concentrations well within the range of intracellular Zn(2+) reported for cultured hepatocytes. The bc(1) complex is inhibited by Zn(2+) (Link, T. A., and von Jagow, G. (1995) J. Biol. Chem. 270, 25001-25006). However, respiration stimulated by succinate (K(i)(app) = approximately 6 micrometer) was less sensitive to Zn(2+), indicating the existence of a mitochondrial target for Zn(2+) upstream from bc(1) complex. Purified pig heart alpha-ketoglutarate dehydrogenase complex was strongly inhibited by Zn(2+) (K(i)(app) = 0.37 +/- 0.05 micrometer). Glutamate dehydrogenase was more resistant (K(i)(app) = 6 micrometer), malate dehydrogenase was unaffected, and succinate dehydrogenase was stimulated by Zn(2+). Zn(2+) inhibition of alpha-ketoglutarate dehydrogenase complex required enzyme cycling and was reversed by EDTA. Reversibility was inversely related to the duration of exposure and the concentration of Zn(2+). Physiological free Zn(2+) may modulate hepatic mitochondrial respiration by reversible inhibition of the alpha-ketoglutarate dehydrogenase complex. In contrast, extreme or chronic elevation of intracellular Zn(2+) could contribute to persistent reductions in mitochondrial respiration that have been observed in Zn(2+)-rich diseased tissues.     

Slowed respiration training

A method of slowed respiration rate (RR) training is described that uses visual feedback of the respiratory cycle. Subjects assigned to the slowed RR training procedure were compared with subjects assigned to either a traditional frontal electromyographic (EMG) biofeedback condition or a control condition where no feedback was presented. RR, frontal EMG, heart rate, digital temperature, and skin conductance level were monitored simultaneously. The results indicated that RR training was effective in reducing RR, that RR training had little systematic effect on the other physiological variables, and the frontal EMG procedure did not in itself reduce RR. The advantages of the current methodological approach and the importance of respiration training were discussed along with a literature review. The relationship between RR training and the complexities of respiratory phenomena was discussed, as well as ways that future research using this method may help clarify current issues within respiration training.This research was supported by grant No. 2-S06RR08038-19 from the National Institutes of Health. The able work of Nora Barker and Robert Longoria is acknowledged, who served as biofeedback technicians.     

Rapid and transient excitation of respiration mediated by central chemoreceptor

We evaluated rapid and transient changes in phrenic nerve (PN) and internal intercostal (IIC) activities when 0.2-0.5 ml of saline saturated with 100% CO2 was injected into the vertebral artery during various respiratory phases in decerebrated spontaneously breathing cats. The injections evoked an initial transient inhibition of ongoing PN or IIC activity with a mean onset latency of 0.17 s, followed by excitation of subsequent respiratory activities with an onset latency ranging from 0.4 to 2.7 s; the average onset latency of expiratory excitation (1.49 s) was significantly longer than that of inspiratory facilitation (0.89 s). The initial inhibitory responses were analogous to reflex effects of injections of phenyl biguanide, indicating that the initial inhibition was due to activation of vascular nociceptors and the subsequent excitation was due to stimulation of the central chemoreceptors. In addition, CO2-saline injections during hypocapnic apnea developed a quick reappearance of respiratory rhythm, and the first facilitatory effect appeared in tonic IIC activity, which became more active before rhythm started. In summary, the present study, by use of a technique of vertebral arterial injections of 100% CO2-saline, revealed dynamic properties of respiratory control system mediated by central chemoreceptors and vascular nociceptors.     

The effect of aluminium on respiration of wheat roots

The effects of aluminium ions on respiration of excised root apices from wheat (Triticum aestivum L. cv. Vulcan) and on isolated mitochondria have been investigated. Addition of 75μ M aluminium to the growth medium of 4-day-old seedlings inhibited O₂ uptake by excised root apices by 23 and 35% after 12 and 24 h, respectively. This decreased rate of respiration was initially caused by inhibition of the cytochrome pathway of mitochondrial electron transport. The cyanide-insensitive, alternative pathway was inhibited only after more prolonged exposure to aluminium. Mitochondria isolated from roots of aluminium-treated seedlings had reduced oxidative capacity with substrates that supply electrons to Complexes I and II, compared with mitochondria from roots of untreated control seedlings. The state 3 and state 4 rates of O₂ uptake and the uncoupled rates with these substrates were also inhibited when aluminium was added directly to reaction mixtures containing mitochondria isolated from untreated plants. In contrast, when aluminium was added to reaction mixtures oxidizing exogenous NADH, state 4 O₂ uptake was stimulated, whereas no effect was observed on the state 3 rate or the rate in the presence of uncoupler. The results suggest that aluminium initially affects electron flow through Complexes I and II, and that after more prolonged exposure, aluminium may also interact with other sites in mitochondria.     

Angiotensin stimulates respiration in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) have an activated brain angiotensin system. We hypothesized 1) that ventilation (V) would be greater in conscious SHR than in control Wistar-Kyoto (WKY) rats and 2) that intravenous infusion of the ANG II-receptor blocker saralasin would depress respiration in SHR, but not in WKY. Respiration and oxygen consumption (VO(2)) were measured in conscious aged-matched groups (n = 16) of adult female SHR and WKY. For protocol 1, rats were habituated to a plethysmograph and measurements obtained over 60-75 min. After installation of chronic intravenous catheters, protocol 2 consisted of 30 min of saline infusion ( approximately 14 microliter. kg(-1). min(-1)) followed by 40 min of saralasin (1.3 microgram. kg(-1). min(-1)). V, tidal volume (VT), inspiratory flow [VT/inspiratory time (TI)], breath expiratory time, and VO(2) were higher, and breath TI was lower in "continuously quiet" SHR. In SHR, but not in WKY rats, ANG II-receptor block decreased V, VT, and VT/TI and increased breath TI. During ANG II-receptor block, an average decrease in VO(2) in SHR was not significant. About one-half of the higher V in SHR appears to be accounted for by an ANG II mechanism acting either via peripheral arterial receptors or circumventricular organs.     

Light respiration by subtropical seaweeds

Here, we report the first‐ever measurements of light CO₂ respiration rate (CRR) by seaweeds. We measured the influence of temperature (15–25°C) and light (irradiance from 60 to 670 μmol · m^?2 · s^?1) on the light CCR of two subtropical seaweed species, and measured the CRR of seven different seaweed species under the same light (150 μmol · m^?2 · s^?1) and temperature (25°C). There was little effect of irradiance on light CRR, but there was an effect of temperature. Across the seven species light CRR was similar to OCR (oxygen consumption rate in the dark), with the exception of a single species. The outlier species was a coralline alga, and the higher light CRR was probably driven by calcification. CRR could be estimated from OCR, as well as carbon photosynthetic rates from oxygen photosynthetic rates, which suggests that previous studies have probably provided good estimations of gross photosynthesis for seaweeds.