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131.
Leaves of Kalanchoë daigremontiana Hamet et Perr. at a photon flux density (PFD) above 220 mol·m–2s–1 (400–700 nm) or at leaf temperatures above 27.0 °C showed a rapid loss of rhythmicity, and a more or less pronounced damping-out of the endogenous circadian rhythm of CO2 exchange under continuous illumination. This rhythm was reinitiated after reduction of the PFD by 90–120 mol·m–2·s–1 or reduction of leaf temperature by 3.5–11.0 °C under otherwise unchanged external conditions. The reduction in the magnitude of the external control parameter of the Crassulacean acid metabolism (CAM) rhythm (i.e. PFD or leaf temperature) set the phase of the new rhythm. The maxima of CO2 uptake occurred about 5, 28, 51, 75 h after the reduction. Simulations with a CAM model under comparable conditions showed a similar behaviour. The influence of temperature on the endogenous CAM rhythm observed in K. daigremontiana in vivo could be simulated by incorporating into the model temperature-dependent switch modes for passive efflux of malate from the vacuole to the cytoplasm. Thus, the model indicates that tonoplast function plays an important role in regulation of the endogenous CAM rhythm in K. daigremontiana.Abbreviations CAM
Crassulacean acid metabolism
- PAR
photosynthetically active radiation
- PFD
photon flux density
This work was supported by a grant to F.B. and U.L. from Teilprojekt B5 in the Sonderforschungsbereich 199 of the Deutsche Forschungsgemeinschaft (Bonn, Germany) and by a grant to T. E. E. G. from the Sudienstiftung des deutschen Volkes (Bonn, Germany). Erika Ball is thanked for processing of time-course data for the analysis of Fourier spectra. 相似文献
132.
Atmospheric ammonia (NH3) from various anthropogenic sources has become a serious problem for natural vegetation. Ammonia not only causes changes in plant nitrogen metabolism, but also affects the acid-base balance of plants. Using the pH-sensitive fluorescent dyes pyranine and esculin, cytosolic and vacuolar pH changes were measured in leaves of C3 and C4 plants exposed for brief periods to concentrations of NH3 in air ranging from 1.33 to 8.29 mol NH3 · mol-1 gas (0.94–5.86 mg · m-3). After a lag phase, uptake of NH3 from air at a rate of 200 nmol NH3 · m - 2 leaf area · s- 1 into leaves of Zea mays L. increased pyranine fluorescence indicating cytosolic alkalinisation. The increase was much larger in the dark than in the light. In illuminated leaves of the C3 plant Pelargonium zonale L. and the C4 plants Z. mays and Amaranthus caudatus L., NH3-dependent cytosolic alkalinisation was particularly pronounced when CO2 was supplied at very low levels (16 or 20 mol CO2 · mol- 1 gas, containing 210 mmol O2 · mol- 1 gas). An increase in esculin fluorescence, which was smaller than that of pyranine, was indicative of trapping of some of the NH3 in the vacuoles of leaves of Spinacia oleracea L. and Z. mays. Photosynthesis and transpiration remained unchanged during exposure of illuminated leaves to NH3, yielding an influx of 200 nmol NH3 · m-2 leaf area · s-1 for up to 30 min, the longest exposure time used. Both CO2 and O2 influenced the extent of cytosolic alkalinisation. At 500 mol CO2 · mol-1 gas the cytosolic alkalinisation was suppressed more than at 16 or 20 mol CO2 · mol-1 gas. The suppressing effect of CO2 on the NH3induced alkalinisation was larger in illuminated leaves of the C4 plants Z. mays and A. caudatus than in leaves of the C3 plant P. zonale. A reduction of the O2 concentration from 210 to 10 mmol O2 · mol -1 gas, which inhibits photorespiration, increased the NH3induced cytosolic alkalinisation in C3 plants. Suppression by CO2 or O2 of the alkaline pH shift caused by the dissolution and protonation of NH3 in queous leaf compartments, and possibly by the production of organic compounds synthesised from atmospheric NH3, indicates that NH3 which enters leaves is rapidly assimilated if photosynthesis or photorespiration provide nitrogen acceptor molecules.This work was supported by the Biotechnology and Biological Sciences Research Council and the Deutsche Forschungsgemein-schaft within the framework of the research of Sonderforschun-gsbreich 251 of the University of Würzburg. We are grateful to Dr. B. Wollenweber (The Royal Veterinary and Agricultural University, Denmark) for discussions. 相似文献
133.
134.
Antonio Cupane Eugenio Vitrano Pal Ormos G.Ulrich Nienhaus 《Biophysical chemistry》1996,60(3):111-117
We have measured the Soret band of the photoproduct obtained by complete photolysis of sperm whale carbonmonoxymyoglobin at 10 K. The experimental spectrum has been modeled with an analytical expression that takes into account the homogeneous bandwidth, the coupling of the electronic transition with both high and low frequency vibrational modes, and the effects of static conformational heterogeneity. The comparison with deoxymyoglobin at low temperature reveals three main differences. In the photoproduct, the Soret band is shifted to red. The band is less asymmetric, and an enhanced coupling to the heme vibrational mode at 674 cm−1 is observed. These differences reflect incomplete relaxation of the active site after ligand dissociation. The smaller band asymmetry of the photoproduct can be explained by a smaller displacement of the iron atom from the mean porphyrin plane, in quantitative agreement with the X-ray structure analysis. The enhanced vibrational coupling is attributed to a subtle heme distortion from the planar geometry that is barely detectable in the X-ray structure. 相似文献
135.
136.
Gerd Esser 《Plant Ecology》1995,121(1-2):175-188
The High Resolution Biosphere Model (HRBM), which has been developed by the group of the author, was used to investigate the carbon balance of the vegetation and the soil in the ecosystems of Monsoon Asia in comparison to the rest of the world. The HRBM is a global grid-based (0.5 degree resolution) model with a monthly time step. It includes modules for natural vegetation, land use, vegetation fires, vegetation composition. A historical carbon budget was calculated for the period 1860–1978 and, on a global scale, validated using atmospheric CO2 data. Based on the per-country development of the population and their requirements, different reasonable scenarios were used to investigate the potential impacts of land use and deforestation in the period 1990–2050. The HRBM calculates considerable contributions of Monsoon Asia to the global CO2 emissions due to land use changes in the past. Between 1860 and 1978, about 1/4 of the global releases from land use changes came from South Asian and Southeast Asian biota. The future contributions in the period 1990–2050 depend on the assumed development of the agricultural methods. If the intensity of agriculture and the agricultural productivity will stay the same as in the 1980s, there will be a strong need to increase agricultural areas, and thus deforestation will dominate. If there will be a change over to intensive methods of agricultural production, the presently used areas might be sufficient to provide resources to the growing population. 相似文献
137.
138.
In an extended screening using d,l-carnitine amide as carbon or nitrogen source about 1300 strains were obtained by enrichment culture. Of these, 65 strains possessed carnitine amidase activities. A single strain was identified as containing an enzyme able to hydrolyse only l-carnitine amide and yield carnitine of high enantiomeric purity (97) when incubated with the racemic substrate. During the initial optimisation of the culture conditions the volume activity could be improved 6.7-fold whereas the specific activity increased 3.6-fold. The enzyme is inducible by l-carnitine amide and carnitine and to a lesser degree also by -butyrobetaine and dehydrocarnitine. As judged by the fatty acids and quinone composition the strain belongs into the -subgroup of purple bacteria but has not yet been classified by the German Culture Collection into a known genus of bacteria.
Correspondence to: M.-R. Kula 相似文献
139.
Ulrich Hagen 《Radiation and environmental biophysics》1994,33(1):45-61
The various aspects of formation and repair of radiation-induced double-strand breaks (DSB) are summarized. Concerning the structure of DSB found in irradiated cells, enzymatic and microdosimetric analysis hints at complex damage of the DNA structure at the position of a DSB. With increasing LET, the DSB damage may be more complex than that induced by low-LET irradiation. Most of the DSB are repaired in the irradiated cell; apparently the kinetics of DSB repair and the fraction of unrejoined DSB determine cell survival or cell death. We do not know the details of the complex machinery of DSB repair; certaintly recombination processes are involved, but there are still contradictions between our current knowledge about the mechanisms of recombinational DSB repair and the observed kinetics.Dedicated to Prof. W. Jacobi on the occasion of his 65th birthday 相似文献
140.
Anders Sonesson Erik Jantzen Torill Tangen Ulrich Zähringer 《Archives of microbiology》1994,162(4):215-221
Lipopolysaccharides (LPS) from Legionella bozemanii serogroup 1 and Legionella longbeachae serogroup 1 were subjected to chemical analyses. The lipid A part of both LPSs contained 2,3-dideoxy-2,3-diamino-d-glucose as major constituents and d-glucosamine and glycerol as minor constituents of the sugar backbone structure. Both LPSs exhibited a very complex fatty acid composition. Twenty amide-linked 3-hydroxy fatty acids were detected in LPS of L. longbeachae, whereas seventeen were encountered in LPS of L. bozemanii. Both LPSs contained nine ester-linked nonhydroxy fatty acids and the unique long-chain fatty acids 27-oxo-octacosanoic acid, 29-oxotriacontanoic acid, heptacosane-1,27-dioic acid and nonacosane-1,29-dioic acid. SDS-PAGE showed that L. bozemanii produced smooth-form LPS, whereas L. longbeachae LPS was mainly of the R-type. Composition analyses were in accordance with these electrophoretic patterns. d-Quinovosamine and l-fucosamine constituted 80 mol% of the polysaccharide part of L. bozemanii LPS. Other sugars identified were d-glucosamine, d-mannose, d-glucose, l-rhamnose, d-glycero-d-manno-heptose, l-glycero-d-mannoheptose, 2-keto-3-deoxy-octonic acid and glycerol. The polysaccharide chain from LPS of L. longbeachae appeared to be shorter, but composed of the same sugars except l-fucosamine. Both LPSs contained glycerol phosphate and glucosamine phosphate and L. longbeachae LPS contained in addition glucose phosphate.Abbreviations
EI
Electron impact
-
GlcN3N
2,3-Diamino-2,3-dideoxy-d-glucose
-
HPAEC
High pH anion-exchange chromatography
-
Kdo
2-Keto-3-deoxy-octonic acid
-
LPS
Lipopolysaccharide
-
PCP
Phenol/chloroform/petroleum ether solvent
-
PED
Pulsed electrochemical detection
-
PS
Polysaccharide
-
TFA
Trifluoroacetyl
-
TMS
Trimethylsilyl 相似文献