Human respiratory sensory system, its physiological role

Modern data on genesis and functional role of sensations associated with respiration, were analysed. Regularities of human perception of the respiratory cycle's parameters have been cited. Respiratory discomfort occurring in an increased loading of the respiratory system, as well as an imperative respiration stimulus developing in a prolonged apnoe or obvious hypoventilation, are regarded as defensive responses to a threat to normal ventilation of the lungs. The central link in mechanisms of the respiratory sensory system seems to involve pulses from receptors of the respiratory muscles.     

Effect of Osmotic Stress in Early Stages of Ontogenesis on Root Respiration, Growth, Sugar Content, and Cell Injury in Maize Seedlings Differing in Drought Sensitivity

Cultivars of maize （Zea mays L.） with different sensitivity to drought were exposed to 0.3 mol/L sorbitol （-1.4 MPa water potential） for 24 h. Exposure to water deficiency significantly reduced the growth of both shoots （coleoptile and hypocotyl） and roots. Shoot growth was inhibited more than the growth of roots. Osmotic stress enhanced accumulation of soluble sugars. Electrolyte leakage, a cell injury index, was slightly increased after 0.3 mol/L sorbitoh Respiration was measured in the presence and absence of 2,6-dlchloro-phenol indophenoh 2,6-Dichloro-phenol indophenol did not influence respiration rates, because statistically equal results were observed under both conditions. Total respiration （VT） decreased after osmoticum treatment. There were no significant differences in the VT among the cultlvars analysed. The decrease In VT was caused by a decline In the activities and capacities of both cytochrome （Vcyt, Vcyt） and alternative pathway （Valt, Valt） of respiration. A high residual respiration （Vres） was observed, up to 27% of total uninhibited respiration. The result of uncoupler use clearly indicated that coupling was maintained after 24 h of osmotic stress. The recovery of the respiration rate was comparable with that of non-stressed control rates. According to these observations, no possible mltochondrial damage is expected. Water deficiency did not induce a stimulation of the alternative oxidase, so we assume that the stimulation of the alternative pathway is not related to drought stress resistance; rather, the function of the alternative pathway is to balance carbon metabolism and electron transport in a response to a changing environment.     

Soil plus root respiration and microbial biomass following water, nitrogen, and phosphorus application at a high arctic semi desert

In order to investigate the effects of anticipated increased precipitation and changing soil nutrient levels on soil CO₂ efflux from high arctic semi desert, a field experiment was carried out in Northeast Greenland. Water, phosphorus, and nitrogen were added to plots in a fully factorial design. Soil microbial biomass carbon was analysed after one year, and respiration from soil plus roots was measured in situ throughout the third growing season after initiation of the experiment. Soil plus root respiration was enhanced by up to 47%, and the microbial biomass by 24%, by the weekly water additions, but not by nutrient additions. The direct effect of increased soil moisture on CO₂ efflux suggests that future changes of precipitation levels and patterns may strongly affect below-ground respiration in arctic semi deserts, with direction of responses depending upon amounts and frequencies of precipitation events. Morover, low CO₂ emission at low light intensities regardless of treatment suggests that the major part of the below-ground respiration originated from turnover of recently fixed C. Hence, the more recalcitrant soil organic matter C pool may not change in proportion to changes in below-ground respiration rate.     

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.     

Utilization of Photosynthates for Growth, Respiration, and Storage in Tops and Roots of Lolium multiflorum

Lolium multiflorum L. was grown in pots in controlled environments. CO₂-exchange rates were continuously measured on two pots during 46 and 52 days, respectively, separating between tops and roots. After 20 days, the plants were entirely defoliated and the plants were then followed during the regrowth period. During the experiment, alternating 2–3 day periods of high and low irradiance were applied. Analogously treated plants were frequently harvested to obtain the distribution of assimilates between tops and roots. From integration of CO₂-exchange rates, diurnal photosynthesis and respiration were obtained, and utilization of assimilates was analysed. The respiration associated with the synthesis of new structural material (growth respiration) was dependent on assimilates originating from both the current and the preceding 24 h diurnal cycles. The amount of new structural material synthesized during the current 24 h diurnal cycle was estimated from the relative contribution of assimilates accumulated from the preceding and the current 24 h and diurnal cycles to growth respiration of the current 24 h. From this approximation, the respiratory components connected to synthesis of new structural material and to maintenance of already established material were found. Growth and maintenance respirations of the tops were alike during the predefoliation and the regrowth periods. For the roots, however, growth respiration was higher and maintenance respiration lower in the regrowth period. The difference between daily integrated CO₂-exchange and the amount converted into new structural material was assumed to be the daily change in assimilates stored. On the first day of a period of high irradiance, the assimilation per unit leaf weight was higher than on the following day of high irradiance, and an accumulation of storage material took place. On the first day of a period of low irradiance, the assimilation per unit leaf weight was lower than on the following day of low irradiance, and there was a depletion of assimilates stored. These effects were most pronounced during the regrowth period, indicating a change in the metabolic sink demand. This indicates a strong feedback mechanism between sources and sinks, in the sense that accumulation of products will inhibit assimilation.     

Soil respiration fluxes measured along a hydrological gradient in a Norway spruce stand in south Sweden (Skogaby)

Soil respiration fluxes were measured continuously in order to assess the degree to which they were influenced by spatial and temporal variation in soil moisture. The synergistic effects of the variation in soil moisture with the one in soil temperature, soil organic matter and global radiation on respiration fluxes were also analysed. The measurements were performed using an open chamber system along a hydrological gradient in a Norway spruce forest in south Sweden (Skogaby) for 3 weeks in June 1995. The measured soil respiration fluxes were quite stable and somewhat larger compared with those reported in literature. The experiment took place during the shoot elongation period with intensive nutrient uptake, and it might be that soil respiration was dominated by mycorrhizal activity. Variation in the moisture content of the litter layer accounted for most of the spatial variation in respiration fluxes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of the cytoskeleton,energy supply,and protein synthesis on the structure of the endoplasmic reticulum

Summary FITC-Con A fluorescence was used to visualize rER arrangement of endothelial cells derived fromXenopus laevis tadpole hearts. In particular determinants of rER organization, intracellular localization and the interrelationships with other organelles were analysed. rER occurs in association with nucleus, mitochondria and microtubules.The structure of rER is strongly affected by energy metabolism and by microtubules. In order to elucidate the interdependence of structure and function we examined the influence of cellular respiration, net lactate production and protein synthesis on rER morphology, as well as the relationship between energy metabolism and protein synthesis. ER morphology is determined primarily by energy consuming intracellular transport mechanisms. Energy needed for protein synthesis is supplied by the respiratory chain while ATP from aerobic glycolysis only compensates when respiration is disturbed.Abbreviations ACM amphibian culture medium - ATP adenosine triphosphate - FITC-Con A fluoresceine-isothiocyanate-coupled con-canavalin A - MT microtubule - rER rough endoplasmic reticulum - sER smooth endoplasmic reticulum - TRITC-phalloidin tetramethyl-rhodaminyl-isothiocyanate-coupled phalloidin - pXTH primary cells fromXenopus laevis tadpole hearts - XTH-2 endothelial cell line derived fromXenopus laevis tadpole hearts     

Russian Article pp. 51–58

This paper considers techniques of measurement of the curves of oxygen consumption by microorganisms. The widely applied method of obtaining the value of the critical oxygen concentration (COC) using these curves has been analysed. The experimental conditions necessary for the adequate measurement of the culture respiration rate in a fermenter have been found. It has been shown that in the case when the respiration rate within the considered range of pO₂ is determined by one and the same enzyme, the COC value is not an apropriate characteristic of the mode of the respiration rate dependence on oxygen concentration.     

Dark Respiration of Winter Wheat Crops in Relation to Temperature and Simulated Photosynthesis

The dark respiration of shoots (measured between March and anthesisin mid-June) and of ears (measured between anthesis and maturityat end of July) of winter wheat crops, grown in 1982 and 1985under different nitrogen application and irrigation conditions,was determined in the field. The respiration rate of 126 averagesof four samples was measured hourly for a 12–14-h darkperiod including the night. Respiration (expressed per unitdry mass) generally declined through the season for both shootsand ears. The average rate of respiration obtained on the samenight was greater for fertilized and irrigated crops, comparedwith unfertilized and droughted crops. The relationship betweenthe measured respiration and photosynthesis, simulated usinga modified version of the model developed by Spitters (1986),was analysed. This revealed that: (a) Shoot respiration was less well correlated with photosynthesisfrom the day preceding measurement than with the average ofthe photosynthesis from the two days preceding measurement. (b) The constants relating shoot respiration to total crop photosynthesisper unit crop mass and ear respiration to total crop photosynthesisper unit ear mass had similar values. This suggests that allgrowth respiration takes place in the ears at the end of theseason. (c) Crop growth respiration consumes about 35% of assimilatebefore anthesis, and that growth respiration of the ear consumesabout 40% of assimilate at the end of the season. (d) No significant effect of treatment on the relationship betweenrespiration and photosynthesis was detected, suggesting thatthe observed effect of treatment on respiration is due entirelyto differences in photosynthesis. Triticwn aestivum var. Avalon, winter wheat, dark respiration, growth coefficient, photosynthesis model, nitrogen nutrition, irrigation     

Interpreting,measuring, and modeling soil respiration

This paper reviews the role of soil respiration in determining ecosystem carbon balance, and the conceptual basis for measuring and modeling soil respiration. We developed it to provide background and context for this special issue on soil respiration and to synthesize the presentations and discussions at the workshop. Soil respiration is the largest component of ecosystem respiration. Because autotrophic and heterotrophic activity belowground is controlled by substrate availability, soil respiration is strongly linked to plant metabolism, photosynthesis and litterfall. This link dominates both base rates and short-term fluctuations in soil respiration and suggests many roles for soil respiration as an indicator of ecosystem metabolism. However, the strong links between above and belowground processes complicate using soil respiration to understand changes in ecosystem carbon storage. Root and associated mycorrhizal respiration produce roughly half of soil respiration, with much of the remainder derived from decomposition of recently produced root and leaf litter. Changes in the carbon stored in the soil generally contribute little to soil respiration, but these changes, together with shifts in plant carbon allocation, determine ecosystem carbon storage belowground and its exchange with the atmosphere. Identifying the small signal from changes in large, slow carbon pools in flux dominated by decomposition of recent material and autotrophic and mycorrhizal respiration is a significant challenge. A mechanistic understanding of the belowground carbon cycle and of the response of different components to the environment will aid in identifying this signal. Our workshop identified information needs to help build that understanding: (1) the mechanisms that control the coupling of canopy and belowground processes; (2) the responses of root and heterotrophic respiration to environment; (3) plant carbon allocation patterns, particularly in different forest developmental stages, and in response to treatments (warming, CO₂, nitrogen additions); and (4) coupling measurements of soil respiration with aboveground processes and changes in soil carbon. Multi-factor experiments need to be sufficiently long to allow the systems to adjust to the treatments. New technologies will be necessary to reduce uncertainty in estimates of carbon allocation, soil carbon pool sizes, and different responses of roots and microbes to environmental conditions.     

羊草呼吸作用与温度、光照和土壤水分的关系

本文报道了两种土壤水分条件下羊草明呼吸速率与光照和温度的关系,以及暗呼吸速率与温度的关系。结果表明,羊草的明呼吸速率与光强呈非线性函数关系。在低光强下,明呼吸速率随光强升高而有较快的增加;随着光强的增高,其增加速度减慢。在温度低于羊草光合的高温补偿点的条件下,明呼吸速率在一定温度范围内随温度升高而增大;当温度达到一定限度时,有一个下降阶段,而后又回升。羊草的暗呼吸速率随温度增加而升高,且在一定限度内,其升高速度随温度增高而加快。当土壤干旱时,明呼吸速率显著降低,而暗呼吸速率仅略有减小。     

长白山阔叶红松林生态系统土壤呼吸作用研究

用密闭静态箱式法观测了长白山阔叶红松林生态系统生长季中的土壤呼吸作用。结果表明, 长白山阔叶红松林生态系统土壤呼吸作用日动态呈单峰曲线, 在 18∶0 0左右达到最大值。土壤呼吸作用在生长季中的动态呈单峰曲线, 7月最大。 6、7、8、9各月平均土壤呼吸作用分别为 0.2 2、0.32、0.2 3和 0.13gC·m-2 ·h-1。温度升高可以提高土壤呼吸作用强度, 地下 5cm的土壤温度比气温更能准确地反映土壤呼吸作用的动态变化 ;土壤水分含量在一定范围内增加可使土壤呼吸作用强度增加, 但水分过多也会对土壤呼吸产生抑制作用而导致土壤碳排放减少。     

The antihypertensive drug carvedilol inhibits the activity of mitochondrial NADH-ubiquinone oxidoreductase

A study is presented on the interaction of carvedilol with mitochondria isolated from several rat organs. It is shown that carvedilol causes a moderate uncoupling effect under non phosphorylating succinate supported respiration of intact mitochondria, as well as a marked inhibition of coupled respiration with NAD-dependent substrates. The inhibitory effect was also found in the bovine heart purified Complex I as well as in experiments with mitochondrial particles, where the individual redox segments of the respiratory chain were analysed. It is also shown that carvedilol, though exhibiting an intrinsic scavenger activity, caused reactive oxygen species to be produced as a consequence of its inhibitory effect on the steady-state respiration. Under these conditions the pro-oxidant activity of carvedilol appears to prevail over its scavenging activity, and a net generation of ROS is promoted.     

Respiration in Eggs of the Echiuroid, Urechis unicinctus, Before and After Fertilization

In eggs of the echiuroid Urechis unicinctus the respiration rate, which is not altered by fertilization, is inhibited by rotenone, antimycin A and cyanide. The respiration in echiuroid eggs is probably mediated by the mitochondrial respiratory chain. In fertilized eggs, the respiration was inhibited by oligomycin and stimulated by the uncouplers of oxidative phosphorylation 2,4-dinitrophenol and carbonylcyanide p-trifluoromethoxyphenylhydrazone, whereas respiration in unfertilized eggs was insensitive to these compounds. Insemination increased the respiratory rate in eggs in the presence of uncouplers and reduced it in the presence of oligomycin. These findings suggest that the capacity of electron transport in mitochondira is elevated by fertilization but becomes latent on fertilization-induced coupling of respiration with oxidative phosphorylation. Strong stimulation of the respiration in unfertilized eggs was induced by dichlorophenol indophenol, phenazine methosulfate and tetramethyl p-phenylenediamine, suggesting possible sites at which electron transport is regulated in unfertilized eggs. The resulting stimulation of respiration in unfertilized eggs was insensitive to uncouplers and oligomycin, but became sensitive to them after fertilization simultaneously with considerable decrease in its rate. Fertilization-induced coupling of the respiration seemed to reduce the respiratory rate enhanced artificially by these redox compounds.     

Growth and Maintenance Respiration in Whole Plants, Tops, and Roots of Lolium multiflorum

Continuous measurements of CO₂-exchange were separately carried out on tops and roots of small swards of Lolium multiflorum grown in nutrient solution in growth chamber during 3–4 weeks. From these measurements, a daily carbon balance and accumulated dry matter could be established. The data were used to distinguish between two components of respiration, one proportional to growth or photosynthesis (growth respiration), the other proportional to plant dry weight (maintenance respiration). The separation of respiration in the two components was made by multiple regression analyses with daily photosynthesis or growth rate and accumulated dry matter as the independent variables. To ensure independency between the independent variables during the growth period, photosynthesis was varied by application of alternate three-day periods of high and low irradiance. From the two regression coefficients, the efficiency of converting assimilates into constructive growth (Y_G) and the maintenance coefficient (M) could be derived. Three experiments with varying length of photoperiod and dark period were carried out. The analyses were carried out for whole-plant respiration, respiration of tops and respiration of roots separately. Growth respiration for whole plants as well as for tops and for roots was lower — and hence the efficiencies higher — the longer the photoperiods were. Growth respiration and maintenance respiration were higher for roots than for tops. The high rate of root respiration may originate from release of HCO₃^? in exchange for NO₃^?. The parameters found can be utilized quantitatively in computer models of crop photosynthesis and respiration.     

羊草呼吸作用与湿度、光照和土壤水分的关系

本文报道了两种土壤水分条件下羊草明呼吸速率与光照和温度的关系,以及暗呼吸速率与温度的关系。结果表明,羊草的明呼吸速率与光强呈非线性函数关系。在低光强下,明呼吸速率随光强升高而有较快的增加;随着光强的增高,其增加速度减慢。在温度低于羊草光合的高温补偿点的条件下,明呼吸速率在一定温度范围内随温度升高而增大;当温度达到一定限度时,有一个下降阶段,而后又回升,羊草的暗呼吸速率随温度增加而升高,且在一定限度内,其升高速度随温度增高而加快。当土壤干旱时,明呼吸速率显著降低,而暗呼吸速率仅略有减小。     

放牧对赖草草地土壤呼吸日、季动态的影响

土壤呼吸是土壤碳向大气排放的关键过程,受土地利用变化的强烈影响。利用LI-840a静态箱法,对放牧利用下赖草(Leymus secalinus)草地土壤呼吸速率日、季动态进行为期2年(2012–2013)的观测,并分析其与大气、土壤温度和土壤含水量的相关性,旨在为合理利用赖草草地提供依据。结果表明,赖草草地土壤呼吸日、季动态均呈单峰型变化,一天中的最高值出现在午间13点,凌晨4点最低,在生长季初的5–6月和生长季末的9月较低,在生长旺盛期7–8月较高。放牧降低了土壤呼吸速率,但并不改变土壤呼吸速率的变化趋势。土壤呼吸速率日变化与大气温度呈显著相关(P0.05),季节变化主要受0–10 cm土壤温度的调控。围封和放牧草地土壤呼吸速率可以分别用下列方程拟合:Rs=1.040 8e0.086Ts(R2=0.91,P0.01);Rs=1.016e0.075 2Ts(R2=0.95,P0.01)。经综合分析得出如下结论:温度是影响赖草草地土壤呼吸速率的主要因素,放牧通过改变土壤表层温度而降低土壤呼吸速率。     

Microbial biomass,respiration and diversity in ultramafic soils of West Dome,New Zealand

Ultramafic soils are colonised by plant communities adapted to naturally elevated heavy metal content but it is not known whether soil microbial communities are similarly adapted to heavy metals. We measured microbial properties of six ultramafic soils that ranged in heavy metal content to test whether microbial diversity would decrease and respiratory quotient (microbial respiration:biomass) increase due to the stress imposed by increasing metal content. Soil samples were collected from beneath Nothofagus solandri var. cliffortioides tall forest, tall Leptospermum scoparium shrubland, open Leptospermum scoparium shrubland, an open Leptospermum scoparium shrubland with the rare ultramafic endemic Celmisia spedenii, a mixed divaricate shrubland, and a red tussock (Chionochloa rubra) grassland on the Dun Mountain Ophiolite belt, New Zealand. Samples were analysed for catabolic evenness using the catabolic response profile technique, microbial biomass, microbial respiration, and soil properties (pH, total carbon, total nitrogen, magnesium and total or extractable chromium and nickel). The sites differed in base saturation, pH and concentrations of metals, particularly magnesium, chromium and nickel, properties that are a major determinant of the plant communities that develop. Microbial biomass and respiration, catabolic evenness (range of 19.1 to 22.7) and the respiratory quotient were not correlated to any of the measured soil chemical properties. Factor analysis of the respiratory responses showed that the microbial communities under each vegetation type were distinct. The second factor extracted was correlated to total carbon (r ²=0.62, P<0.01), basal respiration (r ²=0.55, P<0.01) and microbial biomass (r ²=0.65, P<0.01). Increasing metals concentrations had no direct impact on microbial diversity, biomass, respiration or community energetics. However, we suggest that metal concentrations may have exerted an indirect effect on the structure of the microbial communities through control of the vegetation community and litter inputs of carbon to the soil.     

Prospective elementary science teachers’ understanding of photosynthesis and cellular respiration in the context of multiple biological levels as nested systems

In this study, Turkish prospective elementary science teachers’ understanding of photosynthesis and cellular respiration has been analysed within the contexts of ecosystem knowledge, organism knowledge and interconnection knowledge (IK). In the analysis, concept maps developed by 74 prospective teachers were used. The study was carried out with prospective teachers in their final year who were enrolled in the special teaching methods course. The results show that prospective teachers’ understanding of photosynthesis, cellular respiration, energy flow and matter cycling is quite different from one another’s. In addition, the present study revealed that prospective elementary science teachers showed weak understanding of energy flow and matter, cycling and cellular respiration concepts and IK category but they had strong understanding of photosynthesis concept. Prospective teachers also experience difficulties in understanding connections between macro- and microbiological systems. The study concludes with suggestions for more meaningful biology education.