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1.
This is the first report on using green fluorescent protein (GFP) as a pH reporter in plants. Proton fluxes and pH regulation play important roles in plant cellular activity and therefore, it would be extremely helpful to have a plant gene reporter system for rapid, non‐invasive visualization of intracellular pH changes. In order to develop such a system, we constructed three vectors for transient and stable transformation of plant cells with a pH‐sensitive derivative of green fluorescent protein. Using these vectors, transgenic Arabidopsis thaliana and tobacco plants were produced. Here the application of pH‐sensitive GFP technology in plants is described and, for the first time, the visualization of pH gradients between different developmental compartments in intact whole‐root tissues of A. thaliana is reported. The utility of pH‐sensitive GFP in revealing rapid, environmentally induced changes in cytoplasmic pH in roots is also demonstrated. 相似文献
2.
Sedimentation in fluvial and lacustrine environments 总被引:1,自引:1,他引:0
Sedimentation in rivers is dominated by a complex set of physical processes, associated with the unidirectional flow of water.
Variations in these processes give rise to different fluvial channel types, whose character can commonly be recognised in
the ancient record. Chemical and biological processes are comparatively unimportant in fluvial sedimentation.
In contrast, physical, chemical or biological processes can each dominate sedimentation in lakes. Physical (clastic) deposition
dominates in high-latitude and mountain lakes (in which chemical and biological activity are low), and in lakes with high
relief of the drainage basin and lake floor. Its variety reflects a range of processes influenced by river inflow, wave and
current action, thermal and density effects.
Economic benefits from the study of lake and river sedimentation include both resource and environmental aspects. An example
is given of a mercury pollution study in a fluvial ecosystem. It shows that return to background levels can take place within
a relatively short interval after cessation of pollutant input. 相似文献
3.
Martin Wood 《Plant and Soil》1987,97(3):303-314
Summary Laboratory data for the loss of root material by barley and field data for the growth of barley plants in Syria and in England
have been combined to predict the amount of material lost by barley roots during a season, and to predict the resulting microbial
biomass in the rhizosphere. The predicted microbial biomass C in the rhizosphere ranged from 10–34% of the total plant biomass
C depending mainly upon the value used for rate of loss of root material. Total loss of root material predicted during a season
in England constituted 7.7–25.4 percent of C fixed by photosynthesis. The major assumptions made in these calculations are
considered, and the predicted values discussed in relation to reported values for soil microbial biomass, CO2 fluxes from soil and associative nitrogen fixation. 相似文献
4.
Vertical nutrient transport and its effects on epilimnetic phosphorus in four calcareous lakes 总被引:2,自引:1,他引:1
Robert E. Stauffer 《Hydrobiologia》1987,154(1):87-102
The influence of vertical nutrient transport on epilimnetic phosphorus was studied comparatively in four calcareous Wisconsin lakes during 1972. In the two lakes with steep metalimnetic nutrient gradients (Mendota, Delavan), upward fluxes by entrainment and eddy diffusion exceeded all other influxes combined; here epilimnetic total-P concentrations increased during period of high windpower and thermocline migration, and decreased during comparatively stagnant intervals. In the two lakes lacking upper metalimnetic P gradients (Green, Fish), higher windpower had little or no effect on epilimnetic phosphorus.In each of the four lakes epilimnetic P declined in early summer until a quasi steady-state was achieved between P influxes and P sedimentation. In Mendota and Delavan steady-state featured higher concentrations of total-P, and much higher epilimnetic concentrations of particulate-P and chlorophyll, than in Green and Fish Lakes — mainly on account of the high fluxes of molybdate-reactive, biologically-available P through the seasonal thermocline. The flux analysis illustrates why mean lake TP concentration after ice-out is an inconsistent measure (not sufficient statistic) for estimating nutrient potential and chlorophyll standing crops during the following summer in stratified lakes. 相似文献
5.
Effects of recent acidification on Cladocera in small clear-water lakes studied by means of sedimentary remains 总被引:1,自引:1,他引:0
Cladoceran populations, as revealed by sedimentary remains, were studied in six lakes which by diatom evidence have become
strongly acidified during the past 30 years. The accumulation rates of cladoceran remains and in two of the most strongly
acidified lakes both relative and absolute numbers ofBosmina greatly increased during this period. Species numbers were not reduced, but there were shifts in relative abundances of cladoceran
species.Bosmina longispina dominated all the lakes. Low pH (4.7) seemed not to be straight-forwardly harmful toDaphnia longispina, but the relative abundances of this taxon were reduced because ofBosmina. 相似文献
6.
Direct measurements of net production rates and pore water profiles of solutes in the fine-grained sediments of Saginaw Bay, imply corresponding steady-state fluxes to the overlying water of 1.1–1.3 (I), 450–1010 (NH4
+), 1250–2650 (Si(OH)4), 3000–3400 (Ca2+), 440–1330 (Mg2+), 1.5–728 (Fe2+), and 179–281 (Mn2+) moles/m2/day and 11.0–11.8 (alkalinity) meq/m2/day at 17.5 °C. Silica production rates in sediments apparently follow first order kinetics with a rate coefficient of 0.09/day and a steady-state silica concentration of 1.2 mM at 23.5°C. The remaining solutes follow kinetics approximately independent of solute concentration over the range of concentrations observed. Measured solute production rates are consistent with observed solute profiles only if lateral diffusion gradients are maintained in the sediments by the burrowing and irrigation activity of benthic organisms such asChironomous, the dominant burrower in Saginaw Bay. Assuming that solute fluxes from Saginaw Bay are representative of all of the post-glacial sediments of Lake Huron, the iodine flux from sediments is comparable to the total fluvial input of iodine. The extrapolated silica fluxes from Lake Huron sediments balance the estimated biogenic silica flux to the sediments. 相似文献
7.
Poonam Kakkar Sudhir Mehrotra P. N. Viswanathan 《Molecular and cellular biochemistry》1992,111(1-2):11-15
Incubation of freshly isolated rat liver mitochondria in the presence of oxygen free radical generating hypoxanthine —xanthine oxidase system led to swelling of mitochondria as measured by the change in optical density, which was reversed by the addition of superoxide dismutase. O2
– in the presence of CaCl2 enhanced the peroxidative decomposition of mitochondrial membrane lipids along with swelling of the organelle. Free radical generation led to enhancement of monoamine oxidase activity while glutathione peroxidase and cytochrome c oxidase were inhibited. Tertbutyl hydroperoxide (t-BHP) caused mitochondrial swelling through oxidative stress. Incorporation of ruthenium red, which is a Ca2+ transport blocker, during assay abolished peroxidative membrane damage and swelling. Dithiothreitol (DTT) accorded protection against t-BHP induced mitochondrial swelling. The above in vitro data suggest a possible interrelationship of active oxygen species, membrane damage and calcium dynamics. 相似文献
8.
An experimental test of the eddy correlation technique over a Mediterranean macchia canopy 总被引:4,自引:1,他引:3
R. VALENTINI G. E. SCARASCIA MUGNOZZA P. DE ANGELLS R. BIMBI 《Plant, cell & environment》1991,14(9):987-994
Abstract. Flux densities of water vapour and carbon dioxide were measured for a Mediterranean macchia canopy. Results show good agreement between the measured available energy and the sum of latent sensible and heat flux densities determined with the eddy correlation technique. Joint evaluation of the Bowen ratio, aerodynamic resistance, canopy resistance and the 'omega factor' suggests that the macchia canopy is intermediate in aerodynamic roughness between coniferous and deciduous canopies. Maximum daytime carbon flux densities ranged from -14 to -22(μnol m−2 s−1 on a ground area basis. The ratio of transpiration to assimilation (E/A) was a function of incident photo-synthetic photon flux density below about 400 μmol m−2 s−1 and above it was fairly constant at 272 mol mol−1 (H2 O/CO2 ). The relationship between carbon influx and canopy conductance was linear. Results show promising applications of the eddy correlation technique for evaluating physiological features of canopies, treated as unitary functional systems. 相似文献
9.
Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River 总被引:2,自引:0,他引:2
Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside. 相似文献
10.
Else K. Hoffmann Ian H. Lambert Lars Ole Simonsen 《The Journal of membrane biology》1986,91(3):227-244
Summary The net loss of KCl observed in Ehrlich ascites cells during regulatory volume decrease (RVD) following hypotonic exposure involves activation of separate conductive K+ and Cl– transport pathways. RVD is accelerated when a parallel K+ transport pathway is provided by addition of gramicidin, indicating that the K+ conductance is rate limiting. Addition of ionophore A23187 plus Ca2+ also activates separate K+ and Cl– transport pathways, resulting in a hyperpolarization of the cell membrane. A calculation shows that the K+ and Cl– conductance is increased 14-and 10-fold, respectively. Gramicidin fails to accelerate the A23187-induced cell shrinkage, indicating that the Cl– conductance is rate limiting. An A23187-induced activation of42K and36Cl tracer fluxes is directly demonstrated. RVD and the A23187-induced cell shrinkage both are: (i) inhibited by quinine which blocks the Ca2+-activated K+ channel. (ii) unaffected by substitution of NO
3
–
or SCN– for Cl–, and (iii) inhibited by the anti-calmodulin drug pimozide. When the K+ channel is blocked by quinine but bypassed by addition of gramicidin, the rate of cell shrinkage can be used to monitor the Cl– conductance. The Cl– conductance is increased about 60-fold during RVD. The volume-induced activation of the Cl– transport pathway is transient, with inactivation within about 10 min. The activation induced by ionophore A23187 in Ca2+-free media (probably by release of Ca2+ from internal stores) is also transient, whereas the activation is persistent in Ca2+-containing media. In the latter case, addition of excess EGTA is followed by inactivation of the Cl– transport pathway. These findings suggest that a transient increase in free cytosolic Ca2+ may account for the transient activation of the Cl– transport pathway. The activated anion transport pathway is unselective, carrying both Cl–, Br–, NO
3
–
, and SCN–. The anti-calmodulin drug pimozide blocks the volume- or A23187-induced Cl– transport pathway and also blocks the activation of the K+ transport pathway. This is demonstrated directly by42K flux experiments and indirectly in media where the dominating anion (SCN–) has a high ground permeability. A comparison of the A23187-induced K+ conductance estimated from42K flux measurements at high external K+, and from net K– flux measurements suggests single-file behavior of the Ca2+-activated K+ channel. The number of Ca2+-activated K+ channels is estimated at about 100 per cell. 相似文献