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81.
Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of CO2, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those based on CO2 pore-water gradients using Fick's First law indicates that apparent diffusion coefficients are 2 to 28 times higher than bulk sediment diffusion coefficients based on molecular diffusion. Seasonal changes in gaseous carbon fluxes or CO2 pore water concentrations cannot be used directly, or in a simple way, to determine seasonal rates of mineralization, because of marked seasonal changes in pore-water storage and exchange parameters.The annual amount of carbon delivered to the sediment is 42 mol m–2, of which about 42% becomes buried, the remaining being emitted as methane (7%) or carbon dioxide (50%). Each year about 2.6 mol N m–2 of particulate nitrogen reaches the sediment; 1.1 mol m–2 is buried and 1.6 mol m–2 is mineralized to ammonium. Only 0.42 mol m–2 yr–1 of the ammonium produced escapes from the sediments, the remaining being first nitrified (1.2 mol m–2 yr–1) and then denitrified (1.7 mol m–2 yr–1). Simple calculations indicate that intertidal sediments may account for about 14% and 30% of the total estuarine retention of nitrogen and carbon, respectively. 相似文献
82.
The ammonia oxidizing bacterium Nitrosomonas europaea was grown either (a) with added bicarbonate in the absence of added CO2 (bubbled through the culture), (b) with added bicarbonate plus low added CO2 (0.03% v/v), or (c) without added bicarbonate with high added CO2 (1% v/v). Cell doubling times of 12 h were observed in 1% cultures; doubling times of 2 to 3-fold longer wre found with 0.03% CO2 and/or bicarbonate grown cultures. The specific activity of carbonic anhydrase was 40–80% lower in cultures grown on 1% CO2. These results are compared with those in heterotrophic and photosynthetic microorganisms.Scientific Contribution Number 1241 from the New Hampshire Agricultural Experiment Station 相似文献
83.
Richters Valda Elliott Gary Sherwin Russell P. 《In vitro cellular & developmental biology. Plant》1978,14(5):458-464
Summary The lungs of 12 mice, half of which were exposed to continuous 0.5 ppm nitrogen dioxide for 3 weeks, were explanted in culture,
and the instances of macrophage congregation were quantitated according to numbers of target cells involved, categories of
congregation from three to 11 or more, numbers of macrophages participating in each category for the total cultures, and the
influence of delaying explantation for 24 and 96 hr. A total of 9042 macrophages and 2140 epithelial and spindle target cells
were counted in the outgrowths from 306 explants. The incidence of macrophage congregation (or numbers of target cells) was
greater for the cultures from the NO2-exposed animals, both with respect to total incidences between groups (p→0), and the 0-hr (p<0.001) and 24-hr (p<0.01) culture
subgroups. In addition, the values for T3 to T6 macrophage congregation were individually and consistently greater for the exposed animal group. Postmortem interval stress
at 96 hr appeared to result in large colonies, but they were reduced greatly in number. Also the incidence of macrophage congregation
fell by 28% as compared to 0-hr and 24-hr subgroups.
Supported by Grants NHLI No. HL 17412 and EPA No. R. 800881. 相似文献
84.
Photorespiration by Chlamydomonas reinhardtii and Anacystis nidulans was measured as the oxygen inhibition of CO2 uptake and the CO2 compensation points. Net photosynthesis was oxygen dependent in Chlamydomonas grown in 5% CO2, but CO2 insensitive in cultures bubbled with air. Anacystis, even when cultured in 5% CO2, exhibited an CO2 insensitive net photosynthesis. The CO2 compensation point of Chlamydomonas grown in cultures bubbled with air and Anacystis grown in 5% CO2 enriched air, were reached shortly after the measurement was begun and the values were very low, less than 10 μl CO2 1?1; while Chlamydomonas grown in 5% CO2 enriched air for 4 days showed a high, but temporary CO2 compensation point (60 μl CO2 1?1). After a two hour adaptation in low CO2, a stable, low CO2 compensation point was reached. It seems that photorespiration can only be detected by the methods used in this study when the algae are cultured in high CO2, but a mechanism exists which blocks photorespiration when the green algae are adapted to low CO2 concentrations. When Chlamydomonas was treated with Diamox, an inhibitor of carbonic anhydrase, after cultivation in low CO2 (air), the cells behaved as if they had been grown in high CO2. They showed an oxygen sensitive net photosynthesis and a high CO2 compensation point. This indicates that carbonic anhydrase plays an important role in the regulation of a measurable photorespiration in Chlamydomonas. The results are discussed in relation to previous observations of photorespiration measured by enzyme assay, metabolic products and gas exchange properties. 相似文献
85.
The effect of carbon dioxide on pigment and membrane content in Synechococcus lividus was studied by depriving cells of CO2 and examining cell populations biochemically and by electron microscopy. After 120 h of CO2 deprivation, S. lividus lost all detectable chlorophyll a and C-phycocyanin. Such bleached cultures were mustard yellow, the result of approximately 1.8 times more carotenoid per cell than green control cultures.Although cells from beached cultures appeared morphologically identical to control green cells when examined by light microscopy, electron microscopic examination revealed them to be devoid of detectable thylakoid membrane. Thylakoid membrane could not be recovered by physical isolation or revealed by freeze etching of bleached S. lividus. In addition, inclusion bodies characteristically found in S. lividus were also absent.Reintroduction of CO2 into bleached cultures resulted in a rapid resynthesis of both chlorophyll a and C-phycocyanin. Electron microscopic examination of these regreening cultures revealed that thylakoid membrane was also rapidly resynthesized. Growth of regreened cultures did not occur until there was the synthesis of a full complement of chlorophyll a, C-phycocyanin, and thylakoid membrane.A time course study of the cytological events occurring during bleaching and regreening is presented. 相似文献
86.
The mechanism of photosynthetic carbon dioxide fixation in the green flagellate Dunaliella tertiolecta Butcher varies during growth in batch culture. Evidence for this change comes from three sources: i) algae from the stationary phase incorporated a greater proportion of the fixed carbon into amino arids and protein than did cells from the mid-exponential phase; ii) the activity of phosphoenolpyruvate carboxylase relative to that of ribulose-1, 5-di-phosphate carboxylase increased with age in batch culture; and, iii) cells from the stationary phase appeared to utilize the bicarbonate ion as the substrate for photosynthesis, whereas those from mid-exponential phase appeared to utilize fire carbon dioxide. These data suggest that a change of photosynthetic mechanism can occur within a single species of alga, depending on its physiological state. 相似文献
87.
Two rice ( Oryza sativa L.) cultivars of contrasting morphologies, IR-36 and Fujiyama-5, were exposed to ambient (360 μl l−1 ) and ambient plus 300 μl l−1 CO2 from time of emergence until ca 50% grain fill at the Duke University Phytotron, Durham, North Carolina. Exposure to increased CO2 resulted in about a 50% increase in the photosynthetic rate for both cultivars and photosynthetic enhancement was still evident after 3 months of exposure to a high CO2 environment. The photosynthetic response at 5% CO2 and the response of CO2 assimilation (A) to internal CO2 (Ci ) suggest a reallocation of biochemical resources from RuBP carboxylation to RuBP regeneration. Increases in total plant biomass at elevated CO2 were approximately the same in both cultivars, although differences in allocation patterns were noted in root/shoot ratio. Differences in reproductive characteristics were also observed between cultivars at an elevated CO2 environment with a significant increase in harvest index for IR-36 but not for Fujiyama-5. Changes in carbon allocation in reproduction between these two cultivars suggest that lines of rice could be identified that would maximize reproductive output in a future high CO2 environment. 相似文献
88.
P. CACIAGLI 《The Annals of applied biology》1991,119(2):257-264
This paper describes the effects of carbon dioxide anaesthesia on the ability of the planthopper Laodelphax striatellus to subsequently acquire and transmit maize rough dwarf reovirus (MRDV) and barley yellow striate mosaic rhabdovirus (BYSMV), both propagative in the vector. Anaesthesia reduced the acquisition of MRDV by about 45%, but did not affect acquisition of BYSMV. In serial transfer transmission tests, anaesthesia caused interruption of transmission of both MRDV and BYSMV in about 11% of infectious insects; the effect may be due to impaired ability to find the phloem. The effect was stronger on third instar nymphs than on adults. Transmission of MRDV was resumed 3 days after anaesthesia, but none of the insects that stopped transmitting BYSMV resumed it. The survival of insects which ceased to transmit BYSMV was significantly lower than that of hoppers that continued to transmit. No other effects on survival were detected. A possible interaction of carbon dioxide with BYSMV in L. striatellus is discussed, in the light of effects of carbon dioxide on Drosophila melanogaster infected by some rhabdoviruses. 相似文献
89.
The stoichiometric oxidation of uranous-to uranyl-uranium byThiobacllus ferrooxidans is demonstrated. Fixation of14CO2 and the effect of inhibitors demonstrate that energy is conserved during the oxidation and used for energy-dependent reverse electron flow and carbon dioxide fixation.Abbreviations HOQNO
2-heptyl-4-hydroxyquinoline-N-oxide
- 8-HQ
8-hydroxyquinoline
- TTFA
thenoyltrifluoroacetone 相似文献
90.