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151.
152.
James I. L. Morison 《The New phytologist》2001,149(2):154-156
153.
Interaction between CO2 enrichment and salinity stress in the C4 non-halophyte Andropogon glomeratus (Walter) BSP 总被引:2,自引:2,他引:0
Abstract Increasing atmospheric CO2 may result in alleviation of salinity stress in salt-sensitive plants. In order to assess the effect of enriched CO2 on salinity stress in Andropogon glomeratus, a C4 non-halophyte found in the higher regions of salt marshes, plants were grown at 350, 500, and 650 cm3 m?3 CO2 with 0 or 100 mol m?3 NaCl watering treatments. Increases in leaf area and biomass with increasing CO2 were measured in salt-stressed plants, while decreases in these same parameters were measured in non-salt-stressed plants. Tillering increased substantially with increasing CO2 in salt-stressed plants, resulting in the increased biomass. Six weeks following initiation of treatments, there was no difference in photosynthesis on a leaf area basis with increasing CO2 in salt-stressed plants, although short-term increases probably occurred. Stomatal conductance decreased with increasing CO2 in salt-stressed plants, resulting in higher water-use efficiency, and may have improved the diurnal water status of the plants. Concentrations of Na+ and Cl? were higher in salt stressed-plants while the converse was found for K +. There were no differences in leaf ion content between CO2 treatments in the salt-stressed plants. Decreases in photosynthesis in salt-stressed plants occurred primarily as a result of decreased internal (non-stomatal) conductance. 相似文献
154.
Abstract Crassulacean acid metabolism (CAM) was studied in mixotrophic callus tissue cultures of Kalanchoë blossfeldiana hybr. Montezuma and compared with plants propagated from the calli. The ultrastructural properties of the green callus cells are similar to mesophyll cells of CAM plants except that occasionally abnormal mitochondria were observed. There was permanent net CO2 output by the calli in light and darkness, which was lower in darkness than in light. The calli exhibited a diurnal rhythm of malic acid, with accumulation during the night and depletion during the day. 14C previously incorporated by dark CO2 fixation into malate was transferred upon subsequent illumination into end products of photosynthesis. All these data indicate that CAM operates in the calli tissue. The results revealed that the capacity for CAM is obviously lower in the calli compared with plantlets developing from the calli, or with ‘adult’ plants. The data suggest also that CAM in the calli was not limited by the activities of CAM enzymes. 相似文献
155.
Fioretta Rambelli Maurizio Brigotti Simonetta Sperti Lucio Montanaro 《Bioscience reports》1987,7(9):737-743
Diphtheria toxin fragment A interacts with Cibacron blue in solution, although it is not retained by blue Sepharose columns. Difference spectral titration of fragment A with the dye gives a dissociation constant of the order of 10–5 M and a 11 stoichiometry for the complex. In equilibrium dialysis experiments Cibacron blue behaves as a competitive inhibitor of the binding of NAD to diphtheria toxin fragment A. The dye inhibits in a non-competitive way the fragment A-catalysed transfer of ADP-ribose from NAD to elongation factor 2 (EF2). By affinity chromatography on blue Sepharose a binding of EF2 and of ADP-ribosyl-EF2 with the dye is also demonstrated. GDP, GTP and GDP(CH2)P are able to displace EF2 from blue Sepharose. 相似文献
156.
The rate constant of modification of a specific thiol group, SH2, with N-ethylmaleimide (NEM) has been used to estimate the conformational change in the local area containing SH2 (SH2 region) of skeletal myosin as a structural probe. The rate of Mg2+-ATP-induced SH2 modification of subfragment-1 (S-l) isozymes was regulated by Ca2+ in the pCa range below 6.4 and was not regulated in the pCa range above 6.4. No substantial difference between S-1 containing alkali light chain, A1, (S-1(A1)) and S-1 containing alkali light chain, A2, (S-1(A2)) was observed in the Ca2+-dependent rate of SH2 modification. Due to the presence of this Ca2+ regulation in myosin (absence in S-1 isozymes) in the pCa range above 6.4, absence of 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) light chain in S-1 isozymes, and high affinity of Ca2+ for DTNB light chain, this Ca2+ regulation in the pCa range above 6.4 is possibly related to the Ca2+ binding to DTNB light chain. F-Actin, which is entirely free from tropomyosin and troponin, enhanced the rate of Mg2+-ATP-induced SH2 modification of S-1 isozymes equally and of myosin, and reduced the Ca2+ sensitivity with an increase in F-actin concentration. 相似文献
157.
Increase in cytoplasmic calcium content in internodal cells of Lamprothamnium upon hypotonic treatment 总被引:2,自引:1,他引:1
Abstract Internodal cells of Lamprothamnium succinctum, a brackish water Characeae, regulate turgor pressure in response to changes in external osmotic pressure (turgor regulation). When internodal cells were transferred to a hypotonic medium containing 3.9 mol m?3 Ca2+, the cell osmotic pressure decreased and the original turgor pressure was recovered. During turgor regulation Ca content of the cytoplasm increased significantly. Lowering the external Ca2+ concentration from 3.9 to 0.01 mol m?3 inhibited this increase in cytoplasmic calcium content. In a hypotonic medium containing 0.01 mol m?3 Ca2+, turgor regulation was inhibited as previously reported (Okazaki & Tazawa, 1986a). Thus transient increase in cytoplasmic Ca, probably in the ionized form, induced by hypotonic treatment may play an important role in turgor regulation. 相似文献
158.
The protolytic reactions of PSII membrane fragments were analyzed by measurements of absorption changes of the water soluble indicator dye bromocresol purple induced by a train of 10 s flashes in dark-adapted samples. It was found that: a) in the first flash a rapid H+-release takes place followed by a slower H+-uptake. The deprotonation is insensitive to DCMU but is completely eliminated by linolenic acid treatment of the samples; b) the extent of the H+-uptake in the first flash depends on the redox potential of the suspension. In this time domain no H+-uptake is observed in the subsequent flashes; c) the extent of the H+-release as a function of the flash number in the sequence exhibits a characteristic oscillation pattern. Multiphasic release kinetics are observed. The oscillation pattern can be satisfactorily described by a 1, 0, 1, 2 stoichiometry for the redox transitions Si Si+1 (i=0, 1, 2, 3) in the water oxidizing enzyme system Y. The H+-uptake after the first flash is assumed to be a consequence of the very fast reduction of oxidized Q400(Fe3+) formed due to dark incubation with K3[Fe(CN)6]. The possible participation of component Z in the deprotonation reactions at the PSII donor side is discussed.Abbreviations A
protonizable group at the PSII acceptor side
- BCP
Bromocresol Purple
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- FWHM
Full Width at Half Maximum
- QA, QB
primary and secondary plastoquinone at PSII acceptor side
- Q400
redox group at PSII-acceptor side (high spin Fe2+)
- P680
Photoactive chlorophyll of PSII reaction center
- Si
redox states of the catalytic site of water oxidation
- Z
redox component connecting the catalytic site of water oxidation with the reaction center 相似文献
159.
CO2 fixation was studied in a lichen, Xanthoria parietina, kept in continuous light, and with cyclic changes in light intensity, dark period or temperature. The diurnal and seasonal courses of CO2 exchange were followed. The rate of net photosynthesis was observed to fall from morning to evening, and this decline was more pronounced in winter than in summer. The maximal net photosynthetic rate, 223 ng CO2g-1dws-1, occured in winter and the minimum, 94 ng CO2g-1dws-1, late in spring. The light compensation point in summer was four times as high as in winter. In continuous light (180 or 90 mol photons m-2s-1, 15°C) net photosynthesis decreased noticeably during one week, falling below the level maintained in a 12 h light: 12 h dark cycle. Photosynthetic activity did not decrease, however, in lichens held in continuous light (90 mol photons m-2s-1) with cyclic changes of temperature (12 h 20 °C: 12 h 5 °C). Active photosynthesis was also maintained in light of cyclically changing intensity (12 h: 12 h, 15 °C) when night-time light was at least 75% lower than illumination by day. A dark period of 4 hours in a 24-h light:dark cycle was sufficient to keep CO2 fixation at the control level. It seems that plants need an unproductive period during the day to survive and this can be induced by fluctuations in light and/or temperature. 相似文献
160.
Abstract: Prostaglandin H-E isomerase (EC 5.3.99.3) was purified from human brain cytosol. Purification was by ammonium sulfate fractionation, diethylaminoethyl-Sephar-ose chromatography, gel filtration on a BioGel P-100 column, GSH-agarose chromatography, and MonoQ chromatography. The activity was eluted in two peaks from the MonoQ column, which were designated peaks 1 and 2. The molecular weights of peaks 1 and 2, determined by gel filtration, were 42,000 and 44,000, respectively. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, peak 1 showed two bands at the molecular weights of 24,500 and 25,000, and peak 2 showed a single band at the molecular weight of 25,000, results suggesting that both were dimeric proteins. The pI values of both enzymes were ∼5.4. The enzymes catalyzed selective conversion of prostaglandin H2 to prostaglandin E2 . The K m values for prostaglandin H2 of peaks 1 and 2 were 147 and 308 μ M , respectively, and the V max values were 380 and 720 nmol/min/mg of protein, respectively. GSH was required for the catalysis of both enzymes, and no other sulfhydryl compounds could support the reaction. A part of glutathione S -transferase (EC 2.5.1.18) was copurified with peaks 1 and 2 of prostaglandin H-E isomerase. Prostaglandin H-E isomerase activity of peak 2 enzyme was competitively inhibited by 1-chloro-2,4-dinitrobenzene, a substrate of glutathione S -transferase. These results suggested that prostaglandin H-E isomerases in human brain cytosol were identical with anionic forms of glutathione S -transferase. 相似文献