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1.
Objectives
In this study we investigated the dynamics of meiofaunal and macrofaunal communities in artificial water-filled tree holes. The abundances and, for the first time, biomasses and secondary production rates of these communities were examined. The experimental set-up consisted of 300 brown plastic cups placed in temperate mixed forests and sampled five times over a period of 16 months to determine the impact of (i) seasonal events, (ii) physicochemical parameters, and (iii) food resources on the tree hole metazoans.Outcomes
Metazoan organisms, especially the meiofauna (rotifers and nematodes) occupied nearly all of the cups (> 99%) throughout the year. Between 55% and 99% of the metazoan community was represented by rotifers (max. 557,000 individuals 100 cm-2) and nematodes (max. 58,000 individuals 100 cm-2). Diptera taxa, particularly Dasyhelea sp. (max. 256 individuals 100 cm-2) dominated the macrofaunal community. Macrofauna accounted for the majority of the metazoan biomass, with a mean dry weight of 5,800 μg 100 cm-2 and an annual production rate of 20,400 μg C 100 cm-2, whereas for meiofauna mean biomass and annual production were 100 μg 100 cm-2 and 5,300 μg C 100 cm-2, respectively. The macrofaunal taxa tended to show more fluctuating population dynamic while the meiofaunal dynamic was rather low with partly asynchronous development. Seasonality (average temperature and rain intervals) had a significant impact on both meiofauna and macrofauna. Furthermore, bottom-up control (chlorophyll-a and organic carbon), mainly attributable to algae, was a significant factor that shaped the metazoan communities. In contrast, physicochemical water parameters had no evident influence. 23.7% of organism density distribution was explained by redundancy analysis (RDA) indicating a high dynamic and asynchrony of the systems. 相似文献2.
P. S. Ramlal R. H. Hesslein R. E. Hecky E. J. Fee J. W. M. Rudd S. J. Guildford 《Biogeochemistry》1994,24(3):145-172
The organic carbon cycle of a shallow, tundra lake (mean depth 1.45 m) was followed for 5 weeks of the open water period by examining CO2 fluxes through benthic respiration and anaerobic decomposition, photosynthesis of benthic and phytoplankton communities and gas exchange at the air-water interface. Total photosynthesis (as consumption of carbon dioxide) was 37.5 mmole C m–2 d–1, 83% of which was benthic and macrophytic. By direct measurement benthic respiration exceeded benthic photosynthesis by 6.6 mmole C m–2 d–1. The lake lost 1.4 × 106 moles C in two weeks after ice melted by degassing C02, and 6.8 mmole C m–2 d–1 (1.5 × 106 moles) during the remainder of the open water period; 2.2 mmole C m2 d–1 of this was release Of CO2 stored in the sediments by cryoconcentration the previous winter. Anaerobic microbial decomposition was only 4% of the benthic aerobic respiration rate of 38 mmole C m–2 d–1. An annual budget estimate for the lake indicated that 50% of the carbon was produced by the benthic community, 20% by phytoplankton, and 30% was allochthonous material. The relative contribution of allochthonous input was in accordance with measurement of the 15N of sedimented organic matter. 相似文献
3.
Tatiana F. Maria Marleen De Troch André M. Esteves 《Journal of experimental marine biology and ecology》2011,407(2):309-314
Benthic diatoms are assumed to be of minor importance as food sources in sandy-beach food webs, since they are typically scarce in sandy-beach sediments; whereas organic matter derived from land and sea is known to be more important in sandy-beach food webs. In order to test if benthic and planktonic diatoms play a minor or major role, respectively, in sandy-beach food webs, a laboratory experiment was conducted. Labelled planktonic and benthic diatoms, enriched in the stable carbon 13C isotope, were offered as food sources to sandy-beach macrofauna and meiofauna communities. Uptake of both types of diatoms occurred with most of the species, but benthic diatoms were preferentially consumed by two macrofaunal species and all meiofaunal species. This result reveals the importance of benthic carbon sources in both macrofaunal and interstitial food webs, and suggests a link between both food webs through the common use of benthic diatoms. 相似文献
4.
The dynamics of benthic microbial communities at Davies Reef,central Great Barrier Reef 总被引:2,自引:0,他引:2
The dynamics of benthic microbial communities were examined within different functional zones (reef crest, reef flat, lagoon) of Davies Reef, central Great Barrier Reef, in winter. Bacterial numbers did not change significantly across the reef with a mean abundance
of 1.3 (±0.6) x 109 cells g-1 DW of sediment. Bacterial production, measured as thymidine incorporation into DNA, ranged from 1.2 (±0.2) to 11.6 (±1.5) mg C m-2h-1 across the reef and was significantly lower in a reef crest basin than in the other zones. Bacterial growth rates () across the reef (0.05 to 0.33 g-1) correlated only with sediment organic carbon and nitrogen. Protozoan and meiofaunal densities varied by an order of magnitude across the reef and correlated with one or more sediment variables but not with bacterial numbers or growth rates. Nutrient flux rates were similar to those found at other reefs in the central and southern Great Barrier Reef and are significantly lower than rates measured in temperate sand communities. In the front lagoon, bioturbation and feeding acitivity by thalassinid shrimps (Callianassa spp.) negatively influenced microbial and meiofaunal communities with a net import of organic matter necessary to support the estimated rates of bacterial productivity. In lagoonal areas not colonized by shrimps, primary productivity (400–1100 mg C m-2d-1) from algal mats was sufficient to support bacterial growth. It is suggested that deposit-feeding macrobenthos such as thalassinid crustaceans play a major role in the tructuring and functioning of lower trophic groups (bacteria, microalgae, protozoa, meiofauna) in coral reef sedments, particularly in laggons. 相似文献
5.
Bert G. Drake 《Oecologia》1984,63(2):263-270
Summary Photosynthetic responses to incident photon flux density (400–700 nm; PPFD) was studied in a grass community consisting of Spartina patens and Distichlis spicata and a mixed community having the two grasses and a sedge, Scirpus Olneyi. Net community CO2 exchange and incident PPFD were monitored from dawn to dusk in a large open gas exchange system, and a hyperbolic light response model was fit to the data for each day. Light response curves from five growing seasons were evaluated for seasonal trends in the compensation value, initial slope, and maximum net CO2 exchange rate calculated from the model at PPFD=1670 mol m-2s-1.All response curves were curvilinear. Data from approximately 30% of the 113 days studied fit saturation curves which occurred primarily in spring and fall. Approximately 5% of all curves constructed required a different response curve for the morning and afternoon. These occurred during mid-summer and were interpreted to be evidence of water stress.The compensation flux density was very high early in the growing season, but rapidly decreased and during the months June, July and August, it averaged near 100 and 120 mol m-2s-1 in the mixed and grass communities. The initial slope and maximum net CO2 exchange rate increased from early May to maxima in July and declined thereafter. Mid-summer mean values for the mixed and grass communities respectively were 34.3±10.3 mmol mol-1 and 39.1±9.1 mmol mol-1 for the initial slope and 20.3±4.2 mol m-2s-1 and 23.0±3.8 mol m-2s-1 for maximum net CO2 exchange. Daytime respiration accounted for approximately 20% of maximum gross photosynthesis in both communities.Photosynthetic efficiency, CO2 assimilated per unit total incident solar radiation, was approximately 4.1% and 4.7% at dawn or dusk and 2.3% and 2.6% at midday for the mixed and grass community. Gross photosynthesis, maximum photosynthesis plus midday respiration, accounted for 2.7% and 3.0% of total incident solar radiation in the mixed and grass communities. 相似文献
6.
7.
Species size distributions in marine benthic communities 总被引:12,自引:0,他引:12
Summary Species body size distributions from eight temperate benthic communities show a highly conservative pattern with two separate lognormal distributions, corresponding to the traditional categories of meiofauna and macrofauna. The meiofaunal mode occurs at a dry body weight of 0.64 g and the macrofaunal mode at 3.2 mg, with a trough between them at 45 g. It is suggested that there is a particular body size at which meiofaunal life-history and feeding traits can be optimised, and another for macrofaunal traits. As size departs in either direction (larger or smaller) from these optima, fewer species of the same size are able to co-exist. The split occurs at 45 g because many life history and feeding characteristics switch more or less abruptly at about this body size, compromise traits being either non-viable or disadvantageous. Meiofauna and macrofauna therefore comprise two separate evolutionary units each with an internally coherent set of biological characteristics.The expression of this conservative pattern is modified by water depth: the proportion of macrofauna species increases from intertidal situations to deeper water, and it is suggested that mechanisms of resource partitioning and diversity maintainence in the meiofauna and macrofauna are affected differentially by sediment disturbance. Salinity does not affect this proportionality, and so does not differentially affect mechanisms for maintaining species diversity in any particular size category of animals. Meiofauna species size distributions may be modified in sandy sediments because of physical impositions on interstitial or burrowing lifestyles.Brief discussion of some implications of these observations includes speculations on the larval ecology of macrofauna, on gigantism in Antarctic invertebrates, and on the benthic Sheldon spectrum. 相似文献
8.
Metabolism of a subtropical Brazilian lagoon 总被引:1,自引:1,他引:0
Total community, planktonic and benthic metabolisms were measured by using the carbon dioxide production and consumption, the diurnal curve' method and the in situ bottle incubation technique over an annual cycle in two sublagoons of the Saquarema Lagoon, Brazil. Metabolic rates of the phytoplankton-based lagoon were characterized by considerable daytime and daily variability in production and respiration, by a seasonal shift between net autotrophy and heterotrophy and by an annual balance of production (P = 105 ± 65 mmoles/m2/dayn = 25) and respiration (R = 102 ± 50 mmoles/m2/dayn = 25). Total community metabolism was similar throughout the lagoon, but phytoplankton assimilation rates and benthic respiration showed spatial differences. Bottle incubations compared to total community free water respiration suggested that the pelagic community was 2–5 times more active than the benthos 相似文献
9.
The benthic infauna and benthic respiration off the Banc d'Arguin (Mauritania,Northwest Africa) 总被引:3,自引:3,他引:0
In May 1988, a study was made of the benthic community structure and benthic respiratory activity along two transects across the Mauritanian shelf off Banc d'Arguin. The main emphasis of the present paper is put on the macrobenthos, but results of a gross analysis of the meibenthos are discussed as well. Macrofaunal and meiofaunal density showed no consistent decrease with distance from the shore. The composition of the macrofauna taxa appeared to be closely correlated with sediment parameters and less so with depth. The highest macrofaunal biomass was found at the northern edge of the Banc d'Arguin, and the lowest biomass along the outer shelf. The biomass levels on the shelf match the ones reported for the northern Cap Blanc area where, in contrast to the seasonal upwelling in the investigated area, upwelling takes place all year round.Benthic respiration rates on the offshore shelf were relatively high at the nearshore stations and low near the shelf break. Experimental evidence suggests that the low O2 levels in the upwelling water covering part of shelf, inhibited benthic respiration. The high respiratory activity at some northern inshore stations coincided with the presence of oxygen-rich coastal water. In this area benthic respiration surpassed the level previously reported for the enriched Cap Blanc area. On the basis of our respiration data, an estimate is made of the total carbon demand of the benthic community on the shelf in May and this quantity is compared with the measurements of daily primary production. 相似文献
10.
Size structure of the metazoan community in a Piedmont stream 总被引:1,自引:0,他引:1
N. LeRoy Poff Margaret A. Palmer Paul L. Angermeier Robert L. Vadas Jr. Christine C. Hakenkamp Alexa Bely Peter Arensburger Andrew P. Martin 《Oecologia》1993,95(2):202-209
We characterized the size structure of virtually the entire metazoan community in a fourth order, sandybottomed Piedmont stream during late summer. Our study, the first to sample across all habitat types and sizes of metazoans in an aquatic ecosystem, indicates that at the community level, stream size spectra may be bimodal for the benthos or trimodal when fish are included. Animals spanning 10 orders of magnitude in dry mass (from gastrotrichs to fish) were quantitatively collected from nine habitat types. The bimodal benthic size spectrum was characterized by a meiofaunal component (mostly oligochaetes and micro-crustacea) and a macrobenthic component (mostly the introduced asiatic clam, Corbicula fluminea). Insects contributed little to overall standing crop. Size-specific contribution to whole-community metabolism was assessed using allometric equations for respiration, and we found a distinctly bimodal distribution across the entire metazoan size range, with peaks in the meiofaunal and benthic macrofaunal size ranges. Our bimodal benthic size spectrum is similar to that observed for marine benthos but not to other freshwater benthic systems, possibly because the entire range of habitat types and/or animal sizes were not sampled in the latter. Numerous factors may influence size spectra in stream ecosystems, including local geomorphic (habitat) conditions, water level fluctuations, species introductions, and predation processes. 相似文献
11.
Microbial communities in subsurface environments are poorly characterized and the impacts of anthropogenic contamination on their structure and function have not been adequately addressed. The release of contaminant(s) to a previously unexposed environment is often hypothesized to decrease the diversity of the affected community. We characterized the structure of microbial communities along a gradient of benzene, toluene, ethylbenzene, and xylene (BTEX) and methyl-tert-butyl-ether (MTBE) contamination, resulting from a petroleum spill, within a shallow sandy aquifer at Vandenberg Air Force Base (VAFB) in Lompoc, CA. Differences in microbial community composition along the contaminant plume were assessed via a combinatorial approach utilizing denaturing gradient gel electrophoresis (DGGE), cloning and sequencing, intergenic transcribed spacer analysis (ITS), and comparative phylogenetic analysis of partial 16S rDNA sequences. Substantial bacterial sequence diversity, similar levels of species richness, and similar phylo-groups (including the Cytophaga–Flavobacterium–Bacteroidetes group and numerous members of the -, -, -, -, and -groups of the proteobacteria) were observed in both uncontaminated and contaminated regions of the aquifer. High-resolution measures (ITS fingerprinting and phylogenetic inference) readily separated communities impacted by the original petroleum spill (in source zone) from those in other parts of the aquifer and indicated that communities exposed to MTBE only were similar to communities in uncontaminated regions. Collectively, these data suggest that petroleum contamination alters microbial community structure at the species and subspecies level. Further study is required to determine whether these changes have an impact on the functioning of this subsurface ecosystem. 相似文献
12.
Benthic samples were collected from 1982 to 1985 in two stations in La Coruña Bay in order to study the temporal changes of two subtidal benthic assemblages: (1) a Tellina fabula — Paradoneis armata community, and (2) a Thyasira fluxuosa facies of an Abra alba community. The Tellina station is located in an area with little human disturbance, whereas the Thyasira station is located inside the organically polluted harbour area, where dredging operations took place at the beginning of this study. Temporal changes in both communities follow quite different patterns. The sedimentary environment of the Tellina station remains fairly constant through time: sediment size ranges from 2.80 to 3.85 , and organic matter content (loss by ignition) varies between 3.15 and 4.53%. In the Thyasira station these sedimentary variables cover a much wider range: 3.10 to 5.75 mean diameter and 5.19 to 17.05% organic matter.Community structure is quite stable in the Tellina station. The mean similarity of every sample with the following ones is relatively high and stable, and diversity (H) and evenness (J) fluctuations are small. However, in the Thyasira station the community structure has changed drastically after dredging operations ended as a result of the recolonization and further stabilization of the community.At the Tellina station biomass varies between 10 and 32 g ashfree DW m–2, and it does not show a discernible temporal pattern. However, at the Thyasira station biomass increased from less than 1 g ash-free DW m–2 during the dredging period up to 16 g ash-free DW m–2 18 months after the end of dredging. In conclusion, the Tellina fabula community seems very stable through time, whereas the Thyasira flexuosa facies has wider fluctuations due to human disturbances. 相似文献
13.
C. M. Burke 《Microbial ecology》1995,29(2):163-171
Lake Hayward is a hypersaline lake that stratifies seasonally and maintains oxygen supersaturation in its bottom water for about 6 months each year. This phenomenon was found to be the result of photosynthesis by the benthic microbial communities, composed primarily of the cyanobacteria Cyanothece spp., Spirulina sp., and Oscillatoria sp. When these communities were present and the lake was stratified, the bottom water was supersaturated with oxygen (up to 370%). During illumination, the benthic microbial communities rapidly developed very high concentrations (e.g., >500 M) of oxygen, which then diffused into the overlying water. However, while the overlying water became supersaturated, the concentration in the water was lower than in the benthic microbial communities because (1) transport across the sediment-water interface was limited by diffusion, and (2) turbulence rapidly mixed the oxygen throughout the much larger volume of the bottom water (approximately 1.5 m deep). Thus, import of oxygen by the benthic microbial communities at night proceeded more slowly than daytime export, allowing supersaturation of the bottom water to develop. 相似文献
14.
Mass spectrometric determinations of O2 affinities by the rumen fungus Neocallimastix patriciarum indicated a stable respiration under liquid phase O2 concentrations up to 10 M, the apparent K
m for O2 under these conditions was 4.0 M. Exposure to O2 concentrations in excess of 10 M resulted in rapid inactivation of the observed respiration. Calculated H2 evolution rates for the organism are 8.1 nmol min-1 per mg of protein. Exposure to liquid-phase O2 concentrations in excess of 1.4 M caused 50% inhibition of H2 production. That superoxide and peroxide are amongst the products of respiration was shown by the use of ESR spectroscopy with the spin trapping agent 5,5-dimethyl-l-pyrroline-N-oxide. An active superoxide dismutase was present, but catalase could not be detected.Abbreviations ESR
electron spin resonance
- DMPO
5,5-dimethyl-l-pyrroline-N-oxide
- DETAPAC
diethylene-triamine pentaacetic acid 相似文献
15.
Effects of coral reef benthic primary producers on dissolved organic carbon and microbial activity 总被引:1,自引:0,他引:1
Haas AF Nelson CE Wegley Kelly L Carlson CA Rohwer F Leichter JJ Wyatt A Smith JE 《PloS one》2011,6(11):e27973
Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata – Ochrophyta; Amansia rhodantha – Rhodophyta; Halimeda opuntia – Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h−1 dm−2), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h−1) and concomitant oxygen drawdown (0.16±0.05 µmol L−1 h−1 dm−2). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial dynamics and biogeochemical parameters (i.e., DOC and oxygen availability, bacterial abundance and metabolism) in coral reef communities. 相似文献
16.
John Davy-Bowker Wayne Sweeting Nicole Wright Ralph T. Clarke Sean Arnott 《Hydrobiologia》2006,563(1):109-123
The spatial distribution of benthic (up to 0.05 m depth) and hyporheic (0.25 and 0.5 m depth) macroinvertebrates from downwelling
zones at the heads of riffles and upwelling zones at the tails of riffles was examined in two studies on a 4th order chalk
stream in Dorset, England. In the first study, differences in benthic and hyporheic macroinvertebrate community composition
between the head and tail of a single riffle were investigated. In the second study, a replicated design involving eight riffles
was used to compare benthic and hyporheic macroinvertebrate community composition both between heads and tails of the same
riffles and between riffles. In the first (single riffle) study there were significantly higher mean numbers of benthic invertebrates
and families at the riffle head (715 individuals and 13.8 families per 0.0225 m2) compared to the tail (192 individuals and 8.7 families). ANOSIM analysis also showed that the community structure of head
and tail benthic samples was significantly different. In the second (replicated riffle) study, there were also significantly
more benthic invertebrates at riffle heads (
= 594 per 0.0225 m2) compared to tails (
= 417 per 0.0225 m2), although this was not the case for families, and community structure also differed significantly between riffle heads and
tails. In contrast, in the hyporheic zone, there were no significant differences between the total numbers of invertebrates
in the riffle heads and tails, or between riffles, although a significant difference in family richness between riffle head
and tail samples was identified in the first study. Community analysis revealed progressively poorer separation of riffle
head and tail samples at 0.25 m and 0.5 m hyporheic depths. Whilst being able to identify clear differences in benthic communities
from riffles heads and tails, the physically heterogeneous nature of the riffle habitats studied made it difficult to account
for the consistent differences in macroinvertebrate communities observed with the physical variables measured. 相似文献
17.
The growth inhibitory activities of 6 endogenous growth inhibitors isolated from light-grown dwarf peas (Pisum sativum cv. Progress No. 9) were examined in the epicotyl of dark-grown seedlings of the same cultivar in the dark in order to examine the possible contribution of these compounds to the growth inhibition brought about by red light. The activities of these natural inhibitors, including two A-2 and A-2 of as yet undetermined structure, were compared with those of synthetic growth retardants and benzyladenine. Samples were applied directly into the epicotyls via a glass capillary tube. In 24-h tests doses for a 25% inhibition (I25) were: A-2, 4.3 × 10-2: cis-xanthoxin, 1.2 × 10-1 ; A-2, 1.6 × 10-1; trans-xanthoxin, 1.2; R,S-dihydromaleimide, 3.5 × 102 and pisatin, 4.0 × 102 nmol plant-1 . In 72-h tests, I25's were: benzyladenine, 1.5; AMO-1618 (ammonium-(5-hydroxycarvacryl)-trimethylchloride piperidine carboxylate), 2.4; R,S-dihydromaleimide, 4.0 × 102 and CCC (chlorocholine chloride), 1.1 × 103 nmol plant-1. -D-Glucosyl-R-dihydromaleimide had no activity at all. Benzyladenine caused the thickening as well as elongation inhibition of the epicotyls of intact plants. The possible involvement of A-2 and in the red light growth inhibition of dwarf peas is discussed.Abbreviations AMO-1618
ammonium-(5-hydroxycarvacryl)-trimethylchloride piperidine carboxylate
- CCC
chlorocholine chloride
- G-DHMD
-D-glucosyl-R-dihydromaleimide
- I25
dose required for a 25% growth inhibition
- R
red light
author for correspondence 相似文献
18.
Nafsika Papageorgiou Mariapaola Moreno Valentina Marin Susanna Baiardo Christos Arvanitidis Mauro Fabiano Anastasios Eleftheriou 《Helgoland Marine Research》2007,61(1):31-42
Collelungo beach (Maremma Park, NW Italy), was sampled quantitatively for macrofauna, meiofauna and bacteria in May 2003;
several physicochemical variables and variables associated with food availability and sediment structure were also measured.
Replicated samples were collected from three sites representing natural conditions, an erosion regime, and the influence of
the Ombrone River, respectively, as well as from four stations each located in the surf and sublittoral zones. Both uni- and
multivariate techniques were used to assess the benthic community structure and the associated environmental variables. Different
diversity indices revealed no pattern; in contrast, multivariate techniques applied on the macrobenthic fauna and the polychaete
taxocommunity distinguished between the sites located in natural and eroding conditions from the one located nearby the discharges
of the Ombrone river. Τhe community patterns deriving from meio- and macrofauna are clearly divergent. The overall benthic
faunal community appears to be influenced by both groups of organisms. The patterns of the meio- and macrofaunal communities
seem to be affected synergistically by a number of environmental variables, in accordance with the multicausal environmental
severity hypothesis. Meiofaunal patterns are more often correlated with bacteria and the protein concentration than are macrofaunal
patterns, indicating a potential utilization of bacteria as a food source by the meiofaunal organisms. Total bacterial numbers
are associated with the macrofaunal pattern under the erosion regime, probably as a consequence of competition for food between
macrofauna and meiofauna. 相似文献
19.
The rate of CO2- and p-benzoquione-dependent photosynthetic O2 evolution by Anabaena variabilis cells remained unaltered and the rate of O2 uptake observed after switching off the light (endogenous respiration) was enhanced by a factor of 6–8 when the O2 concentration was increased from 200 to 400 M. Photosystem-I-linked O2 uptake and respiration of the cells incubated with ascorbate and N,N,NN-tetramethyl-p-phenylenediamine was not appreciable influenced by the O2 concentration. 2-Iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether, blocking electron transfer at the plastoquinone level, suppressed O2 evolution and had no influence on endogenous respiration. 2-n-Heptyl-4-hydroxyquinoline-N-oxide, an inhibitor of electron transfer between photosystems II and I, as well as the cytochrome-oxidase inhibitors N
3
-
, CN- and NH2OH, caused a 35–50% retardation of endogenous respiration and blocked photosynthetic O2 evolution. The molar ratio of cytochromes b6, f, c-553, aa3 and photosystem-I reaction centers in the isolated membranes equalled approx. 2:1:2:0.7:2. It is inferred that endogenous respiration of A. variabilis cells is inhibited by the light-induced electron flow through both photosystems at the level of the plastoquinone-plastocyanin-oxidoreductase complex.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DNP-INT
2-iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether
- Hepes
4-(2-hydroxyethyl)-1-piperazine ethansulfonic acid
- TMPD
N,N,NN-tetramethyl-p-phenylenediamine 相似文献
20.
Stable carbon and nitrogen isotope ratios were used to posit the relative importance of microbial processes on energy pathways in an ephemeral, humic boreal wetland compared to four clearwater lakes in northwestern Ontario, Canada. In addition to algae and dipteran larvae, odonate larvae were sampled as these latter organisms are known to predate indiscriminately on smaller invertebrates and are thus likely to have average isotope ratios reflective of their habitats. Similarities in 13C and 15N values between lake insect larvae and emerged adults suggested that littoral foodwebs in these oligotrophic lakes may rely to a considerable degree upon terrestrial carbon. Wetland insect larvae and algae were depleted in both 13C and 15N compared to biota in lakes. Carbon isotope analysis implied a substantial presence of microbial respiration from decomposition in the humic wetland, whereas nitrogen isotope analysis suggested the prevalence of microbially modified nitrogen dynamics, including the possibilty of N-fixation. 相似文献