Potential Respiration Research Articles

Changes in potential denitrification and respiration during the cold storage of soils.

The denitrification potential in moderately fertilized soil sampled four times during 1995 decreased significantly after cold storage, at 4 +/- 2 degrees C for 1 week. Prolonged storage (up to 24 weeks) resulted in a further decrease of denitrification potential which dropped to 38-54% of the original values. Similarly, denitrification potential decreased substantially during the first week of storage in differently fertilized soils. After 24 weeks of storage, denitrification potential dropped to 29-55% of that in fresh soils. The effects of storage at 4 +/- 2 degrees C on denitrification potential and respiration (determined as carbon dioxide evolution) were in general the same in moderately fertilized soils from four different sites: in all soils, depression of both the denitrification potential and potential respiration was found after 8 weeks. However, the extent to which the parameters were decreased differed from case to case. Not only the duration and storage conditions but also unidentified soil parameters are important for the persistence of biological activity in stored soils.

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.

Mapping meristem respiration of Prunus persica (L.) Batsch seedlings: potential respiration of the meristems, O 2 diffusional constraints and combined effects on root growth

Mapping meristem respiration of Prunus persica (L.) Batsch seedlings: potential respiration of the meristems, O 2 diffusional constraints and combined effects on root growth

Cd2+ effects on transmembrane electrical potential difference, respiration and membrane permeability of rice (Oryza sativa L) roots.

Among other detrimental effects of the heavy metal Cd2+, a decrease in the plant content of essential mineral nutrients is known. In this study, the effect of Cd2+ on different physiological activities of rice roots involved in nutrient acquisition has been studied. Upon addition of 0.1 or 1 mM Cd2+ to the experimental solution, root cell membranes depolarized in few minutes, reaching very low Em values. This effect was transient and the initial membrane potential recovered totally within 6–8 h. Only the highest concentration used had an inhibitory effect on root respiration. Significant respiratory inhibition appeared after 2 h of exposure to Cd2+ and lasted for at least 4 h. In turn, membrane permeability increased in the presence of Cd2+ for at least 8 h, inducing K+ efflux from the roots. The relationship between these parameters and their possible involvement in lowered nutrient content in Cd2+-treated plants is discussed.

Effects of inorganic mercury on the respiration and the swimming activity of shrimp larvae, Pandalus borealis

In order to test the sensitivity of respiration (physiological and potential) to mercury (Hg) contamination, larval shrimp Pandalus borealis were exposed to inorganic Hg (0–160 ppb) for 27 h in the laboratory. Oxygen consumption rates (RO 2), potential respiration (determined by respiratory electron transfer system activity, ETSA), protein content, and swimming activity for zoeae III and zoeae V stages were measured. For both zoeae stages, ETSA and protein content remained constant after 27 h exposure to 160 ppb Hg whereas RO 2 and swimming activity decreased. This study revealed the impact of different Hg levels and different exposure times on RO 2 of shrimp larvae. After 10 h exposure to 160 ppb Hg, the RO 2 decreased by 43 and 49% in zoeae III and zoeae V stages, respectively. Exposure time of 27 h to 80 ppb Hg and higher, induced paralysis in nearly 100% larvae. Surprisingly, the paralysed larvae displayed almost 50% of the control's RO 2. The results showed that Hg disturbs a part of the respiration process without modifying the maximum activity of the enzymes involved in the ETSA assay. Therefore, the ETSA assay can not be used as a sublethal bioanalytic probe to detect Hg in short-term exposures. The decline of the RO 2/ETSA ratios reported here, indicates an inability of contaminated larvae to adapt their metabolism to physiological stress caused by Hg.

UNGULATE VS. LANDSCAPE CONTROL OF SOIL C AND N PROCESSES IN GRASSLANDS OF YELLOWSTONE NATIONAL PARK

Within large grassland ecosystems, climatic and topographic gradients are considered the primary controls of soil processes. Ungulates also can influence soil dynamics; however the relative contribution of large herbivores to controlling grassland soil processes remains largely unknown. In this study, we compared the effects of native migratory ungulates and variable site (“landscape”) conditions, caused by combined climatic and topographic variability, on grassland of the northern winter range of Yellowstone National Park by determining soil C and N dynamics inside and outside 33–37 yr exclosures at seven diverse sites. Sites included hilltop, slope, and slope bottom positions across a climatic gradient and represented among the driest and wettest grasslands on the northern winter range. We performed two experiments: (1) a 12-mo in situ net N mineralization study and (2) a long-term (62-wk) laboratory incubation to measure potential N mineralization and microbial respiration. Results from the in situ experiment indicated that average net N mineralization among grazed plots (3.8 g N·m−2·yr−1) was double that of fenced, ungrazed plots (1.9 g N·m−2·yr−1). Mean grazer enhancement of net N mineralization across sites (1.9 g N·m−2·yr−1) approached the maximum difference in net N mineralization among fenced plots (2.2 g N·m−2·yr−1), i.e., the greatest landscape effect observed. Furthermore, ungulates substantially increased between-site variation in mineralization; grazed grassland, 1 sd = 2.2 g N·m−2·yr−1, fenced grassland, 1 sd = 0.85 g N·m−2·yr−1. In the long-term incubation, potential microbial respiration and net N mineralization were positively related to total soil C and N content, respectively. There was greater variation in potential respiration and net N mineralization early in the incubation, when labile material was processed, compared to late in the incubation, when more recalcitrant substrate was processed, suggesting that between-site variation in labile organic matter was greater than that of recalcitrant material. Herbivores improved the organic matter quality of soil, increasing the labile fractions and reducing the recalcitrant fractions. Grazers reduced C respired/N mineralized ratios, an index of microbial N immobilization, by an average of 21%. However, the largest landscape influence on the immobilization index was 13-fold greater than the grazer effect. Given that the greatest landscape influence on in situ net mineralization (2.2 g N·m−2·yr−1) was similar to the average grazer impact on that rate (1.9 g N·m−2·yr−1), we hypothesize that the landscape effect on field N availability was primarily caused by variation in microbial immobilization, while the grazing effect was primarily due to stimulation of gross mineralization. These results indicate that the relative importance of ungulates in controlling soil N cycling may be more important than previously suspected for grasslands supporting large herds of migratory ungulates, and that the dominant mechanisms underlying the landscape and ungulate influences on soil mineral fluxes may differ.

Decomposition dynamics of litters of various pine species in a Corsican pine forest

The decomposition dynamics of the litters of Corsican pine ( Pinus laricio Poiret), Stone pine ( P. pinea L.) and Scots pine ( P. sylvestris L.) exposed in a Corsican pine forest in the South Italy Apennines were followed for 2.5 y. Litter decomposition was very slow for all three species and appeared to be limited mainly by the low water availability throughout the study. The microbial activity, expressed as respiration, and the fungal biomass were also low due to the low moisture content of the litters, as suggested by the high increase of the potential respiration, after their hydration. A highly significant and positive relationship between potential CO 2 evolution rates and litter moisture content was found. The decomposition dynamics were also affected by the initial chemical composition of the three litter types. A delay in starting decomposition and the lowest initial rate were observed in Stone pine litter, that had the highest initial N, but also the highest lignin content and the lowest initial Mn content.

Soil attributes as predictors of crop production under standardized conditions

To assess soil fertility or quality three controlling components – its physical, chemical and biological nature – have to be considered. In this study a broad spectrum of agricultural soils from Sweden were cropped with ryegrass in pots under standardized conditions in climate chambers. Measurements of physical, chemical and biological attributes of soil were used to predict C and N yields by simple correlation and the multivariate calibration techniques, principal component analysis combined with multiple linear regression, and partial least squares (PLS) regression. The N yields were typically more accurately predicted than the corresponding C yields. The best single predictor of yields was always total soil N, but estimates produced by multivariate models including organic C, total N, C/N ratio, coarse silt, potential denitrification activity, N mineralization, substrate-induced respiration and sample site humidity were, in all cases, substantially more accurate. Coefficients of correlation between predicted and measured C or N yields ranged between 0.61 and 0.80 with total N as predictor, and between 0.69 and 0.97 with the multivariate models. Both quantitative and qualitative aspects of the organic matter were considered to be important with respect to the predictive ability. Both these aspects were accounted for by the multivariate models. The multivariate technique, PLS regression, facilitated the classification of soils into categories of good, normal or poor fertility in relation to their organic matter content.

Microbial biomass and its mineralization activity in a comparative study of five anthropogenic grassland soils contaminated by persistent organic pollutants

This study surveyed microbial biomass and its mineralization activity in five anthropogenic grasslands typically contaminated by persistent organic pollutants (polychlorinated biphenyls — PCBs, polycyclic aromatic hydrocarbons — PAHs, DDT). Toxic equivalent (I‐TEQ 2378‐TCDD; pg•g‐1) of PCBs congeners decreased in the following order: site T (8.40) > site P (3.10) > site M (1.1) > site PZ (0.92) > site K (0.05). Site M was the only one with increased level of polychlorinated phenols (23.80 μg•g‐1). Following parameters of stressed microbial communities were evaluated: microbial biomass carbon (MB‐C), respiration rate (RR), potential (glucose‐stimulated) respiration rate (PR), biomass specific respiration activity (qCO2) and long‐term glucose uptake incubation experiments where mineralization kinetics is studied simultaneously with the evaluation of MB‐C. Estimates of MB‐C provided very suitable basis for the evaluation of mineralization capacity. Although the soils were not fully distinguished only on the basis of short‐term estimations of RR and PR values, the ratio RR/PR appeared to reflect relatively low capacity of microflora in heavily polluted soils to utilize sufficient amount of available organic matter naturally present in the sites. Significant decline of MB‐C content during laboratory incubations without substrate addition also proved low mineralization capacity of soils PZ, P, and particularly of soil T, while soil K was able to maintain present microbial biomass and relatively high mineralization activity. In all the soils, the addition of glucose significantly increased MB‐C content and newly synthesized biomass at the end of incubation could be arranged in the following order: K > M > P > PZ > T. Sufficient mineralization capacity and sustainability of microbial biomass was therefore observed in the site K that was not highly polluted by PCBs and DDT. Microflora in the other soils appeared to be limited in mineralization capacity and in conversion efficiency of substrate C to biomass C which appeared to be caused mainly by bacteriostatic effect of PCBs.

Organic halogen, heavy metals and biological activities in pristine and pulp mill recipient lake sediments

In order to create a basis for prognosing future intrinsic remediation potential of past pollution by pulping industry, we analyzed biochemical activities and levels of pollution in sediments dated with 210Pb and 137Cs. A small pristine forest lake and a pulp mill recipient area of a large oligotrophic Lake Saimaa were test sites. Sediment concentration of EOX ranged from 40 to 130 μg Cl (g d.w.)−1 in the pristine lake and from 770 to 4700 μg Cl (g d.w.)−1 in the pulp mill recipient area and the C:Cl (w/w) ratio of sediment organic matter ranged from 2000 to 5100 and 42 to 230, respectively. The organic matter in 10 to 20 years old pulp mill recipient sediment was mainly of waste water origin. The activity gradients of β-glucosidase, butyrate-esterase, methane oxidation potential and endogenous respiration from surface to deeper layers were less steep in polluted than in pristine sediment. Methane oxidation potential was 120 μmol CH4d−1 (g C)−1 at the sediment surface of pristine lake sediment and 26 μmol CH4d−1 (g C)−1 at the polluted site, endogenous respiration rates of the surface sediment were 670 and 310 μmol CO2 d−1 (g C)−1, respectively. In the most polluted layer we found a depressed potential for methane oxidation, inhibition of phosphatase and butyrate-lipase activities and moderately increased induction ratio of β-galactosidase to phosphatase in the SOS-Chromotest strain E. coli PQ 37. The results suggest that at the concentrations observed these effects in the sediment were not due to heavy metals.

Plant-microbe competition for soil amino acids in the alpine tundra: effects of freeze-thaw and dry-rewet events.

Amino acids have been shown to be a potentially significant N source for the alpine sedge, Kobresia myosuroides. We hypothesised that freeze-thaw and dry-rewet events allow this plant species increased access to amino acids by disrupting microbial cells, which decreases the size of competing microbial populations, but increases soil amino acid concentrations. To test this hypothesis, we characterized freeze-thaw and dry-rewet events in the field and simulated them in laboratory experiments on plant-soil microcosms. In one experiment, 15N,13C-[2]-glycine was added to microcosms that had previously been subjected to a freeze-thaw or dry-rewet event, and isotopic concentrations in the plant and microbial fractions were compared to non-stressed controls. Microbial biomass and uptake of the labeled glycine were unaffected by the freezing and drying treatments, but microbial uptake of 15N was lower in the two warmer treatments (dry-rewet and summer control) then in the two colder treatments (freeze-thaw and fall control). Plant uptake of glycine-15N was decreased by climatic disturbance, and uptake in plants that had been frozen appeared to be dependent on the severity of the freeze. The fact that intact glycine was absorbed by the plants was confirmed by near equal enrichment of plant tissues in 13C and 15N. Plants under optimal conditions recovered 3.5% of the added 15N and microbes recovered 5.0%. The majority of the 13C and 15N label remained in a non-extractable fraction in the bulk soil. To better understand the isolated influences of environmental perturbations on soil amino acid pools and population sizes of amino-acid utilizing microbes, separate experiments were performed in which soils, alone, were subjected to drying and rewetting or freezing and thawing. Potential respiration of glycine and glutamate (substrate-induced respiration; SIR) by the soil microbial communities was unaffected by a single freeze-thaw event. Glycine SIR was decreased slightly (∼10%) by the most extreme drying treatment, but glutamate SIR was not significantly affected. Freezing lowered the concentration of water-extractable amino acids while drying increased their concentration. We interpret the surprising former result as either a decrease in proteolytic activity in frozen soils relative to amino acid uptake, or a stimulation in microbial uptake by physical nutrient release from the soil. We conclude that climatic disturbance does not provide opportunities for increased amino acid uptake by K. myosuroides, but that this plant competes well for amino acid N under non-stressed conditions, especially when soils are warm. We also note that this alpine tundra microbial community's high resistance to freeze-thaw and dry-rewet events is novel and contrasts with studies in other ecosystems.

Reed stands in constructed wetlands: “edge effect” and photochemical efficiency of PS II in common reed

In this study an attempt has been made to estimate the vitality of the common reed (Phragmites australis) grown in the constructed wetland. The efficiency of solar radiation uptake of leaves was measured and terminal electron transport system (ETS) activity of roots was determined in specimens from different locations on the reed bed. The results showed that photochemical efficiency of PS II, expressed as FvFm ratio, was higher in plants growing in the middle of the well established stand, but it was lower in plants growing in the area permanently flooded with leachate, where plants were significantly lower. Potential respiration of roots on the vertical rhizome decreases with depth, while it showed slight variations when determined at the same depth, but in plants from different locations within three beds of RBTS.

Succession of cellular states in a Salmonella typhimurium population during starvation in artificial seawater microcosms

The succession of the physiological states of Salmonella typhimurium cells under starvation-survival conditions in artificial seawater was investigated by flow cytometry and epifluorescence microscopy using direct examination of different cell functions. Measurements of substrate responsiveness (DVC method), real and potential respiration (redox dye 5-cyano-2,3-ditolyl tetrazolium chloride, CTC), membrane permeability ( BacLight™ kit), as well as DNA content (Hoechst 33342 staining) reveal an important heterogeneity within the population, and suggest a progressive physiological cell alteration throughout the starvation process. The transition steps between culturable and prelytic cells are described.

Reed stands in constructed wetlands: “edge effect” and photochemical efficiency of PS II in common reed

In this study an attempt has been made to estimate the vitality of the common reed (Phragmites australis) grown in the constructed wetland. The efficiency of solar radiation uptake of leaves was measured and terminal electron transport system (ETS) activity of roots was determined in specimens from different locations on the reed bed. The results showed that photochemical efficiency of PS II, expressed as F✓Fm ratio, was higher in plants growing in the middle of the well established stand, but it was lower in plants growing in the area permanently flooded with leachate, where plants were significantly lower. Potential respiration of roots on the vertical rhizome decreases with depth, while it showed slight variations when determined at the same depth, but in plants from different locations within three beds of RBTS.

Photosynthetic performance and photoinhibition in two species ofPotamogetonfrom lake Bohinj (Slovenia)

Summary Apparent photosynthesis, dark respiration, photochemical efficiency of photosystem II and potential respiration, estimated as terminal electron transport system (ETS) activity, were determined under experimental conditions to evaluate physiological differences in two competing species Potamogeton lucens L. and Potamogeton alpinus Balbis. The investigations showed that there are no significant differences in photosynthetic response and ETS activity. In P. lucens ETS capacity highly exceeds dark respiration measured as O2 consumption. Photochemical efficiency of PS II in P. lucens was higher and the recovery after photoinhibition was more effective.

Respiratory electron transport system (ETS) activity in Spanish reservoirs: relationships with nutrients and seston

We examined the relationship between potential respiration rates, as measured by electron transport system (ETS) activity, standardized at a defined temperature (ETS2O). and nutrients and sestonic particles in a set of 101 Spanish reservoirs spannin a wide range of limnological characteristics. ETS activity ranged from 0.009 to 31 31 μmol e- 1−1 h−1 Among the nutrients, it was significantly correlated only with phosphorus, and only during the stratification period. During this period, the best regressor of ETS2O was the concentration of chlorophyll a (Chla), whereas during the mixing period the best regressor was particulate organic nitrogen (PON), suggesting a greater contribution of non-algal sestonic particles to total metabolism. Both the mean ETS20:PON ratio and the mean Chla:PON ratio increased systematically with increasing PON, indicating a lower relative contnbution of detrital particles to total seston as trophic state increased. In contrast, the mean ETS20:Chla ratio was constant across the range of Chla. Vertical profiles of ETS2O. Chla and PON were more coherent during the stratification period. when subsurface and metalimnetic peaks were frequent, than during the mixing period.

The microbial respiration quotient as indicator for bioremediation processes

The respiration quotient (Q R) calculated from the actual (R A) and potential respiration rate (R P) after addition of glucose ( Q R = R A R P ) was compared with the PAH concentration of a contaminated site during bioremediation. A correlation coefficient of 0.997 was obtained. Comparison with respiration quotients of several contaminated and uncontaminated sites gives evidence that the quotient is a suitable indicator for easily biodegradable carbon sources in the soil and presents an adequate quick and easily determinable indicator for the efficiency of bioremediation processes.

Vernal abundance, structure and development of epipelagic copepod populations of the eastern Weddell Sea (Antarctica)

Pelagic copepod populations under the pack ice of the Antarctic Weddell Sea were sampled with a 50 μm net between October 2 and December 7, 1986, to study their abundance and developmental stage composition before and at the onset of the vernal phytoplankton bloom. Subadult stages and adult females were incubated to estimate rates of development and egg production. Copepod densities in the upper 200 m were highest for the small-sized species Oithona similis, Oncaea curvata and Ctenocalanus citer. About 95% of the copedite stages belonged to these species, dominated by Oithona. The copepodids were outnumbered by the nauplii in all species, except in Oncaea. The stage distribution in the small-sized species was bimodal with peaks in N3 and C4. The larger species Calanus propinquus and Metridia gerlachei showed peaks in nauplii only. Eggs were relatively abundant in all small and large species. Animals smaller than 1 mm not only were more abundant than the larger ones, but also had a higher total potential respiration. Eggs were produced by incubated females in sea water virtually without food at 0°C. Eggs hatched, and Oithona nauplii developed at a rate of about 7 days per stage. Copepodite stages did not develop significantly. Reproduction in the most abundant species commonly occurred before the algal spring increase when food levels were very low. Maintenance of a stable stage distribution at the expense of a high juvenile mortality seemed to be characteristic for the overwintering strategy of Antarctic copepods.

Biomass and activity of benthic fauna on the fladen ground (northern North Sea)

During May 1983 the abundance and biomass of macrobenthos and meiobenthos populations, as well as the metabolic activity (shipboard incubated and in situ measured respiration, and potential respiration activity by ETS) were studied in the Fladen Ground area. Macrofauna showed an abundance of 4500 specimens per m 2; the corresponding biomass was 10.7 g ash-free dry weight per m 2. The bivalve Arctica islandica, with 12 specimens per m 2 contributed 7.2 g to this biomass. Average meiofauna numbers, 0.9·10 6 per m 2 were low; a meiofaunal biomass of only 0.3 g was estimated. Depending on the method applied, large variations in metabolic activity were found. Results from shipboard incubation experiments probably present a large underestimate. The in situ bell-jar experiments showed an average oxygen uptake of 1010 μmol O 2·m −2·h −1, equalling a carbon demand of 7.3 gC·m −2·month −1 in May. ETS measurements gave a 3 times higher estimate. Taking into account that macrofaunal and meiofaunal abundance and biomass, as well as bottom temperatures, show minimum values in spring, an annual carbon mineralization by the benthic system of 50 to 70 gC·m −2 is suggested. This would mean that about one third of the total primary produced organic matter is channelled into the benthic system.

Generation of the electrochemical potential of Na + by the Na +-motive NADH oxidase in inverted membrane vesicles of Vibrio alginolyticus

Inverted membrane vesicles prepared from Vibrio alginolyticus generated a membrane potential (positive inside) and accumulated Na + by the oxidation of NADH. Generation of the membrane potential required Na + and was inhibited by 2-heptyl-4-hydroxyquinoline N-oxide, a specific inhibitor of the Na +-dependent NADH oxidase. Collapse of the membrane potential by valinomycin stimulated the uptake of Na +. In contrast, accumulation of H + was not detected under all the conditions tested. These results suggest that only Na + is translocated by the Na +-dependent NADH oxidase of V. alginolyticus. Inverted vesicle Na + pump NADH oxidase Marine bacterium Na + electrochemical potential Respiration