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1.
Solute dynamics in soil water and groundwater in a central Amazon catchment undergoing deforestation 总被引:1,自引:3,他引:1
Hydrochemical changes caused by slash-and-burnagricultural practices in a small upland catchment inthe central Amazon were measured. Soluteconcentrations were analyzed in wet deposition,overland flow, shallow throughflow, groundwater andbank seepage in a forested plot (about 5 ha) and anadjacent plot (about 2 ha) which had been deforestedin July 1989 and planted to manioc, and in streamwater in partially deforested and forested catchments. Measurements were made from November 1988 to June1990. The effects of slash-and-burn agriculturalpractices observed in the experimental plot includedincreased overland flow, erosion, and large losses ofsolutes from the rooted zone. Concentrations ofNO3
-, Na+, K+, SO4
2-,Cl- and Mn in throughflow of the experimentalplot were higher than those of the control plot bymore than a factor of 10. Extensive leaching occurredafter cutting and burning, but solute transfers werediminished along pathway stages of throughflow togroundwater, and particularly within the riparian zoneof the catchment. High concentrations of N and P inoverland flow indicate the importance of usingforested riparian buffers to mitigate solute inputs toreceiving waters in tropical catchments. 相似文献
2.
Ross D. Fitzhugh Tanya Furman ast; J. Rick Webb B. Jack Cosby Charles T. Driscoll 《Biogeochemistry》1999,47(1):39-62
The chemical composition during baseflow was used to elucidate the fundamental processes controlling longitudinal and seasonal patterns of stream acidity in Yellow Creek, a chronically acidic headwater (pH range 3.7--4.2) on the Appalachian Plateau in northeastern West Virginia. Sulfate concentrations controlled the variability of stream acidity within the Yellow Creek catchment. Decreases in stream free H+ acidity with decreasing elevation likely resulted from SO
4
2–
retention in riparian wetland areas as well as spatial variation in dominant tree species. Seasonal variations in free H+ and inorganic monomeric aluminum (Aln+) concentrations appeared related to seasonal fluctuations in baseflow discharge which was controlled by vegetative activity. Baseflow stream discharge, as well as H+ and Aln+ acidity, gradually declined during the growing season (June through October), likely reflecting microbial SO
4
2–
> reduction in saturated anaerobic environments within riparian wetlands. A marked pulse of stream H+, Aln+, and SO
4
2–
coincided with an abrupt increase in baseflow discharge resulting from the cessation of transpiration after leaf-fall in November. This seasonal pattern suggests that autumn may be a critical period for eastern brook trout in streams draining wetlands on the Appalachian Plateau. 相似文献
3.
Summary The loop diuretic bumetanide binds specifically to the Na/K/2Cl cotransporter of many cell types including duck erythrocytes. Membranes isolated from these erythrocytes retain the ability to bind bumetanide when cells are exposed to cotransport activity stimuli prior to membrane isolation. An extensive study of the effects of ions on specific [3H]bumetanide binding to such membranes is presented here and compared to the activity of these ions in supporting transport function in intact cells. Both Na+ and K+ enhanced bumetanide binding in a saturable manner consistent with a single-site interaction. The K
m
for each ion was dependent on the concentration of the other cation suggesting heterotropic cooperative interactions between the Na+ and K+ binding sites. Na+ and K+ were partially replaceable, with the selectivity of the Na+ site being Na+ > Li+ > NH
4
+
; N-methyl-d-glucamine+, choline+ and tetramethylammonium+ also supported a small amount of specific binding when substituted for Na+. The selectivity of the K+ site was K+ Rb+ > NH
4
+
> Cs+; N-methyl-d-glucamine+, choline+ and tetramethylammonium+ were inactive at this site. The results of transport experiments revealed a slightly different pattern. Li+ could partially substitute for Na+ in supporting coteansport, but other monovalent cations were completely inactive. The order of potency at the K+ site was NH
4
+
> K+ Rb+ > Cs+ other monovalent cations. The effect of Cl- on bumetanide binding was biphasic, being stimulatory at low [Cl-] but inhibitory at high [Cl-]. As this implies the existence of two Cl- binding sites (termed Cl
H
and Cl
L
for the high- and low- affinity sites, respectively) each phase was examined individually. Cl- binding to Cl
H
could be described by a rectangular hyperbola with a K
m
of 2.5 mm, while kinetic analysis of the inhibition of bumetanide binding at high [Cl-] revealed that it was of a noncompetitive type (K
i
= 112.9 mm). The selectivity of anion binding to the two sites was distinct. Cl
H
was highly selective with Cl- > SCN- > Br-; F-, NO
3
-
, ClO
4
-
, MeSO
4
-
, gluconate- and SO
4
2-
were inactive. The efficacy of anion inhibition of binding to Cl
L
was ClO
4
-
> I- > SCN- > NO3 > Cl-; F-, MeSO
4
-
, gluconate-, and SO
4
2-
were inactive. Thus, Cl
H
is much more selective than Cl
L
and largely accounts for the specificity of the system with respect to anion transport. SO
4
-
, NO
3
-
, I-, SCN- and ClO
4
-
did not support cotransport when bound to Cl
L
and the latter three anions were inhibitory. Mg2+ was found to stimulate binding at a narrowly defined peak around 1.5 mm, but was inhibitory at higher concentrations. Other divalent cations caused a similar inhibition of bumetanide binding but did not exert a stimulatory effect at 1.5 mm. Divalent cations have little effect on cotransport in intact cells at concentrations up to 20 mm, suggesting that their effects on diuretic binding reflect interactions at internally disposed sites. Bumetanide binding was optimal at a pH of 7.8–8.1 and declined sharply as the pH was lowered towards 6. The titration curve correlated well with the effect of pH on cotransport in intact cells; the inhibitory effect of low pH suggests that protonation of the cotransporter may inhibit its function.We thank Drs. Brad Pewitt, John Westley and Mrinalini Rao for discussion, Sara Leung and Artelia Watson for their excellent technical assistance, and Dr. R.J. Turner for his gift of [3H] bumetanide. This work was supported in part by Cystic Fibrosis Center grant #CF RO11 7-04. 相似文献
4.
Jon Chorover Peter M. Vitousek Daniel A. Everson Anne M. Esperanza Douglas Turner 《Biogeochemistry》1994,26(2):115-144
Solution chemistry profiles of mixed-conifer forests in granitic catchments of the Sierra Nevada were measured for three years before (1987–1990) and three years after (1990–1993) prescribed fire. Wet deposition, throughfall and soil solution samplers were installed in both white-fir and giant-sequoia dominated forest stands underlain by poorly developed inceptisols. Stream water chemistry was monitored as part of an ongoing study of catchment outputs. Calcium, NO
3
–
and Cl– were the major ions in precipitation. Canopy leaching increased mean concentrations of all major ions, especially K+ and Ca2+. Water flux through the soil occurred largely during spring snowmelt. Forest floor leachate represented the most concentrated solutions of major ions. Interaction with the mineral soil decreased mean concentrations of most species and the average composition of soil solutions closely resembled stream water at baseflow. Bicarbonate alkalinity, Ca2+, Mg2+, and Na+ were enriched in stream water relative to precipitation whereas inputs of H+, NH
4
+
, NO
3
–
and SO
4
2–
were retained within the catchments.Burning of the forest understory and litter layer increased solute concentrations in soil solution and stream water. Mean soil solution Ca2+, Mg2+ and K+ concentrations increased more than 10 fold, but the relative predominance of these cations was not affected by burning. Sulfate concentration, which was very low in soil solutions of undisturbed stands (<25 mmolc m–3), increased more than 100 times following fire. Ammonium concentration exhibited a rapid, short-term increase and then a decrease below pre-burn levels. Changes in soil solution chemistry were reflected in catchment outputs.Corresponding author. 相似文献
5.
Dissolved nutrient inputs in bulk precipitation and outputs in streamwater were measured during 3 years of contrasting hydrological conditions in a 6.3-ha, grazed heathland watershed on schists in the Montseny mountains (NE Spain), drained by an intermittent stream. On average, 39% of the precipitation became streamflow. Bulk precipitation delivered positive net alkalinity (mean 0.22 keq/ha/yr), sulphate input was moderate (9.0 kg SO4-S/ha/yr), and the mean input of inorganic N was not exceptionally high (6.6 kg/ha/yr). Ion concentrations were relatively low in streamwater; SO4
2- was the dominant anion. Most concentrations in streamwater varied seasonally, with maxima in late summer or early autumn and minima in spring. This pattern probably resulted from increased availability of ions for leaching due to decomposition of organic matter and chemical weathering during the warm period. Nitrate concentrations were relatively high in winter and dropped sharply in early spring, probably because of biological uptake. Annual element outputs in streamwater varied between years and seemed to be controlled by both the amount of annual streamflow and its seasonal distribution. Annual inputs exceeded outputs for dissolved inorganic N. The watershed accumulated H+ and Ca2+, had net losses of Na+ and Mg2+, and was close to steady state for K+, SO4
2-, Cl- and alkalinity. The chloride budgets gave no evidence of substantial dry deposition in this system. The cationic denudation rate was negative (-0.14 keq/ha/yr) because Ca2+ retention was higher than net exports of Na+ and Mg2+ from silicate weathering. Low nutrient export and little production of alkalinity suggest that this watershed has a low buffering capacity. 相似文献
6.
In this study we investigated the spatial and temporal variation in soil solution chemistry and of water and ion fluxes through the soil in a forest ecosystem. Our aim was to evaluate the relevance of these variations for the accuracy of average areal soil solution concentrations and ion fluxes with seepage at 90 cm depth.Twenty spatially distinct subcompartments of approximately 1 m2 were established within a mature stand of Norway spruce and ceramic suction lysimeters were installed at depths of 20, 35 and 90 cm. A tensiometer was placed close to each suction lysimeter, and one throughfall sampler was established for each subcompartment.Soil solution samples were analysed for major ions (H+, Na+, K+, Ca2+, Mg2+, Mn2+, Fe3+, Al3+, Cl-, NO
3
-
, SO
4
2-
. We calculated water fluxes for each subcompartment separately by a numeric simulation of the soil water flux close to the lysimeters. The ion fluxes at each lysimeter were calculated by multiplying the simulated water fluxes with the ion concentrations on a fortnightly base. Averaging these 20 independent ion fluxes gave the areal average flux and an estimate of its statistical accuracy. The spatial variation of ion concentrations in the soil solution was high with coefficients of variance ranging from 5% to 128%. Part of the spatial variation was related to stem distance. Temporal variation of the concentrations was less than spatial for most ions. The spatial variation of water and ion fluxes with seepage was also substantial; for example the fluxes of SO
4
2-
-S calculated for each subcompartment ranged from 21 to 119 kg ha-1 yr-1, with an arithmetic average of 47 kg ha-1 yr-1. For H2O, Mg2+, Cl-, and SO
4
2-
, the spatial heterogeneity of seepage fluxes was largely explained by the heterogeneity of throughfall fluxes. No such relationship was found for nitrogen.Despite using 20 replicates, the 95% confidence intervals of the average annual areal fluxes with seepage were found to be 20–30% for most ions. 相似文献
7.
Junichi Mano Kunio Kawamoto G. Charles Dismukes Kozi Asada 《Photosynthesis research》1993,38(3):433-440
A new binding site for anions which inhibit the water oxidizing complex (WOC) of Photosystem II in spinach has been identified. Anions which bind to this site inhibit the flash-induced S2/S0 catalase reaction (2H2O22H2O+O2) of the WOC by displacing hydrogen peroxide. Using a mass spectrometer and gas permeable membrane to detect the 32O2 product, the yield and lifetime of the active state of the flash-induced catalase (to be referred to simply as flash-catalase) reaction were measured after forming the S2 or S0-states by a short flash. The increase in flash-catalase activity with H2O2 concentration exhibits a Km=10–20 mM, and originates from an increase in the lifetime by 20-fold of the active state. The increased lifetime in the presence of peroxide is ascribed to formation of the long-lived S0-state at the expense of the unstable S2-state. The anion inhibition site differs from the chloride site involved in stimulating the photolytic water oxidation reaction (2H2OO2+4e-+4H+). Whereas water oxidation requires Cl- and is inhibited with increasing effectiveness by F-CN-N3
-, the flash-catalase reaction is weakly inhibited by Cl-, and with increasing effectiveness by F-CN-, N3
-. Unlike water oxidation, chloride is unable to suppress or reverse inhibition of the flash-catalase reaction caused by these anions. The inhibitor effectiveness correlates with the pKa of the conjugate acid, suggesting that the protonated species may be the active inhibitor. The reduced activity arises from a shortening of the lifetime of the flash-induced catalase active state by 3–10 fold owing to stronger anion binding in the flash-induced states, S2 and S0, than in the dark S-states, S1 and S-1. To account for the paradoxical result that higher anion concentrations are required to inhibit at lower H2O2 concentrations, where S2 forms initially after the flash, than at higher H2O2 concentrations, where S0 forms initially after the flash, stronger anion binding to the S0-state than to the S2-state is proposed. A kinetic model is given which accounts for these equilibria with anions and H2O2. The rate constant for the formation/release of O2 by reduction of S2 in the WOC is <0.4 s-1.Abbreviations ADRY
acceleration of the deactivation reactions of the water splitting enzyme system Y
- BTP
bis [tris(hydroxymethyl)methylamino]-propane
- CCCP
carbonylcyanide m-chlorophenylhyrazone
- DCBQ
2,5-dichlorobenzoquinone
- DMBQ
2,3-dimethylbenzoquinone
- WOC
water oxidizing complex 相似文献
8.
Timothy R. Traynor Scott M. O'Grady 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):47-53
Summary Porcine distal colon epithelium was mounted in Ussing chambers and bathed in plasma-like Ringer solution. Tissue conductances ranged from 10 to 15 mS and the short-circuit current (Isc) ranged from-15 to 220 A·cm-2. Variations in basal Isc resulted from differences in the amount of amiloride (10M mucosal addition)-sensitive Na+ absorption. Ion substitution and transepithelial flux experiments showed that 10 M amiloride produced a decrease in the mucosal-to-serosal (M-S) and net Na flux, and that this effect on Isc was independent of Cl- and HCO
3
-
replacement. When the concentration of mucosal amiloride was increased from 10 to 100 M, little change in Isc was observed. However, increasing the concentration to 1 mM produced a further inhibition, which often reversed the polarity of the Isc. The decrease in Isc due to 1 mM amiloride was dependent on both Cl- and HCO
3
-
, and was attributed to reductions in the M-S and net Na+ fluxes as well as the M-S unidirectional Cl- flux. Ion replacement experiments demonstrated that Cl- substitution reduced the M-S and net Na fluxes, while replacement of HCO
3
-
with HEPES abolished net Cl- absorption by reducing the M-S unidirectional Cl- flux. From these data it can be concluded that: (1) Na+ absorption is mediated by two distinct amiloride-sensitive transport pathways, and (2) Cl- absorption is completely HCO
3
-
-dependent (presumably mediated by Cl-/HCO
3
-
exchange) and occurs independently of Na+ absorption.Abbreviations Gt
tissue conductance
- HEPES
tris (hydroxymethyl) aminomethane
- (tris)
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- Isc
short-circuit current
- Jr
residual flux
- M-S
mucosal-to-scrosal
- S-M
serosal-to-mucosal
- TTX
tetrodotoxin 相似文献
9.
K. Nagashima M. Ando 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(1):47-54
To characterize mechanisms of esophageal desalination, osmotic water permeability and ion fluxes were measured in the isolated esophagus of the seawater eel. The osmotic permeability coefficient in the seawater eel esophagus was 2·10-4 cm·s-1. This value was much lower than those in tight epithelial, although the eel esophagus is a leaky epithelium with a tissue resistance of 77 ohm·cm-2. When the esophagus was bathed in normal Ringer solutions on both sides no net ion and water fluxes were observed. However, when mucosal NaCl concentration was increased by a factor of 3, Na+ und Cl- ions were transferred from mucosa to serosa (desalination). If only Na+ or Cl- concentration in the mucosal fluid was increased by a factor of 3, net Na+ and Cl- fluxes were reduced to 30–40%, indicating that 60–70% of the net Na+ and Cl- fluxes are coupled mutually. The coupled NaCl transport seems to be effective in desalting the luminal high NaCl. The remaining 30–40% of the total Na+ and Cl- fluxes seems to be due to a simple diffusion, because these components are independent of each other and follow their electrochemical gradients, and also because these fluxes remain even after treatment with NaCN or ouabain. A half of the coupled NaCl transport could be explained by a Na+/H+–Cl-/HCO
3
-
double exchanger on the apical membrane of the esophageal epithelium, because mucosal amiloride and 4.4-diisothiocyanatostilbene-2,2-disulphonic acid inhibited the net Na+ and Cl- fluxes by approximately 30%. The other half of the coupled NaCl transport, which follows their electrochemical gradients, still remains to be explained.Abbreviations DIDS
4,4-diisothiocyanatostilbene-2,2-disulphonic acid
- NMDG
N-methyl-d-glucosamine
-
P
Cl
Cl- permeability coefficient
- PD
transepithelial potential difference
-
P
Na
Na+ permeability coefficient
-
P
osm
osinotic permeability coefficient
- TALH
thick ascending limb of Henle's loop 相似文献
10.
Ribulose bisphosphate carboxylase (EC 4.1.1.39) from Thiobacillus A2 has been purified to homogeneity on the basis of polyacrylamide gel electrophoresis and U.V. analysis during sedimentation velocity studies. The enzyme had an optimum pH of about 8.2 with Tris-HCl buffers. The molecular weight was about 521000 with an S
rel. of 16.9. K
m for RuBP was 122 M, for total CO2 it was 4.17 mM, and for Mg2+ 20.0 M. The absolute requirement for a divalent cation was satisfied by Mg2+ which was replaceable to a certain extent by Mn2+. Activity was not significantly affected by SO
4
2-
, SO
3
2-
, or S2O
3
2-
at 1.0 mM. At this concentration S2- caused a 27% stimulation. All mercurials tested were inhibitory. pHMB was the most potent causing about 60% inhibition at 0.01 mM. This inhibition was reversible by low concentrations of cysteine. Cyanide was also inhibitory. Its mode of inhibition with respect to RuBP was un-competitive and with a K
i of 20 M. Lost activity could be restored partially by GSH or Cu2+. Although azide at the concentration tested had no significant effect on enzyme activity, 2,4-dinitrophenol at 1.0 mM caused 91% inhibition. Finally, activity was also affected by energy charge.Abbreviations ATP
adenosine-5-triphosphate
- GAPDH
glyceraldehyde phosphate dehydrogenase
- GSH
(reduced) glutathione
- G6P
glucose-6-phosphate
- NAD+
nicotinamide adenine dinucleotide
- NADP+
nicotinamide adenine dinucleotide phosphate
- pHMB
parahydroxymercuribenzoate
- 6PG
6-phosphogluconate
- 3-PGA
3-phosphoglycerate
- PGK
phosphoglyceratekinase
- RuBP
ribulose-1,5-bisphosphate 相似文献
11.
With 3-O-methylfluorescein phosphate (3-OMFP) as substrate for the phosphatase reaction catalyzed by the (Na+ + K+)-ATPase, a number of properties of that reaction differ from those with the common substratep-nitrophenyl phosphate (NPP): theK
m is 2 orders of magnitude less and the Vmax is two times greater, and dimethyl sulfoxide (Me2SO) inhibits rather than stimulates. In addition, reducing the incubation pH decreases both theK
m and Vmax for K+-activated 3-OMFP hydrolysis as well as theK
0.5 for K+ activation. However, reducing the incubation pH increases inhibition by Pi and the Vmax for 3-OMFP hydrolysis in the absence of K+. When choline chloride is varied reciprocally with NaCl to maintain the ionic strength constant, NaCl inhibits K+-activated 3-OMFP hydrolysis modestly with 10 mM KCl, but stimulates (in the range 5–30 mM NaCl) with suboptimal (0.35 mM) KCl. In the absence of K+, however, NaCl stimulates increasingly over the range 5–100 mM when the ionic strength is held constant. These observations are interpreted in terms of (a) differential effects of the ligands on enzyme conformations; (b) alternative reaction pathways in the absence of Na+, with a faster, phosphorylating pathway more readily available to 3-OMFP than to NPP; and (c) a (Na+ + K+)-phosphatase pathway, most apparent at suboptimal K+ concentrations, that is also more readily available to 3-OMFP.Abbreviations Et3N
triethyl amine
- FITC
fluorescein isothiocyanate
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonate
- MES
2-(N-morpholino)ethanesulfonate
- Me2SO
dimethyl sulfoxide
- NPP
p-nitrophenyl phosphate
- 3-OMFP
3-O-methylfluorescein phosphate
- TNP-ATP
2, (or 3)-O-(2,4,6-trinitrophenyl)-ATP 相似文献
12.
Horst Onken Kai Graszynski Wolfgang Zeiske 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(3):293-301
Summary Single gill lamellae from posterior gills of Chinese crabs (Eriocheir sinensis) were isolated, separated into halves and mounted in a modified Ussing chamber. Area-related short-circuit current (Isc) and conductance (Gtot) of this preparation were measured. Epithelial cells were impaled with microelectrodes through the basolateral membrane and cellular potentials (Vi under open- and Vsc under short-circuit conditions) as well as the voltage divider ratios (Fi, Fo) were determined.With NaCl salines on both sides an outside positive PDte (22±2 mV) and an Isc (-64±13 A·cm-2) with a polarity corresponding to an uptake of negative charges (inward negative) were obtained. Trough-like potential profiles were recorded across the preparation under open- as well as short-circuit conditions (Vo=-101±5 mV, external bath as reference; Vi=-78±2 mV, internal bath as reference; Vsc=-80±2 mV, extracellular space as reference). The voltage divider ratios of the external (apical membrane plus cuticle) and internal (basolateral membrane) barrier were Fo=0.92±0.01 and Fi=0.08±0.01, respectively. To investigate a Cl--related contribution to the above parameters, Na+-free solutions in the external bath (basolateral NaCl-saline) were used. Inward negative Isc under these conditions almost completely depended on external Cl-. Elimination of Cl- in the external bath reversed Isc, and Gtot decreased substantially. Concomitantly, Vsc depolarised and Fo increased. Cl--dependent current and conductance showed saturation kinetics with increasing external [Cl-]. Addition of 20 mmol·1-1 thiocyanate to the external bath had similar, although less pronounced, effects as Cl- substitution. Equally, external SITS (1 mmol·1-1) inhibited the current and, concomitantly, Gtot decreased substantially. Addition of 1 mmol·1-1 acetazolamide to, and omission of NaHCO3 from, the basolateral bath resulted in a decrease of Isc while Gtot remained unchanged. The Cl--channel blocker DPC inhibited Isc almost completely when added to the basolateral saline, whereas Gtot decreased moderately; however, Vsc depolarised without significant change of Fi. Ouabain had no influence on Isc and Gtot. Increasing the basolateral [K+] resulted in a decrease in Isc, while Gtot was not affected. At the same time Vsc largely depolarised and Fi decreased. Addition of the K+-channel blocker Ba++ (5 mmol·1-1) to the basolateral solution resulted in a two-step alteration of the transepithelial (Isc, Gtot) and cellular (Vsc, Fi) parameters. The results are discussed with regard to (i) the mechanisms responsible for active transbranchial Cl- uptake, and (ii) the technical improvement of being able to perform transport studies with crab gill preparations in an Ussing chamber.Abbreviations
DMSO
dimethylsulfoxide
-
DPC
diphenylamine-2-carboxylate
-
F
o, i
voltage divider ratio for external (o) and internal (i) barrier, respectively
-
G
Cl
conductance related to the external [Cl-]
-
G
tot
total tissue conductance
-
I
Cl
short-circuit current related to the external [Cl-]
-
I
sc
short-circuit current
-
PD
te
transepithelial potential difference
-
R
ME
resistance of the microelectrode
-
SITS
4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid
-
V
o, i
open-circuit voltage across the external (o) and internal (i) barrier, respectively
-
V
sc
intracellular potential under short-circuit conditions 相似文献
13.
Active Cl- uptake by Chlorella fusca was examined by using 36Cl as a label. Under light/air conditions chloride influx from a 2.4·10-5 M solution was 4.0±0.04 nmol m-2s-1. After 70±10 min a stationary 380±40 fold accumulation was reached. In dark/air and dark/argon influx and accumulation were reduced to 25±6%, respectively, 5±1.5% of the light/air control. Cl- uptake had a broad optimum around pH 7 and showed saturation kinetics with a K
M of 1.25·10-5 M and a v
max of 7.0 nmol m-2s-1 in light/air. Br- inhibited Cl- uptake strongly, J-, ClO
4
-
, SO
4
2-
, and NO
3
-
had no inhibitory effect. Inhibitor studies with carbonyl cyanide m-chlorophenylhydrazone and N,N-dicyclohexylcarbodiimide resulted in a good correlation between Cl- uptake and ATP level. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea and darkness reduced transport activity without affecting the ATP level.The magnitudes of the pH gradient and the membrane potential across the cell membrane were determined and/or estimated under different conditions. It could be shown that in Chlorella Cl- transport cannot proceed via secondary active H+/Cl- cotransport. In addition, 2H+/Cl- cotransport seems unlikely for energetic reasons. On the basis of the results of this and the following study, a primary active ATP-driven Cl-/OH- exchange pump is proposed.Abbreviations CCCP
carbonyl cyanide m-chlorophenylhyd razone
- DCCD
N,N-dicyclohexylcarbodiimide
- DCMU
3-(3.4-dichlorophenyl)-1.1-dimethylurea
- DMO
5,5-dimethyloxazolidine-2,4-dione
- Hepes
N-2-hydroxyethylpiperazine-N ethane-sulfonic acid
- POPOP
1.4-bis-2-(4-methyl-5-phenyloxazolyl)-benzene
- PPO
2.5-diphenyloxazole
To whom correspondence should be addressed 相似文献
14.
Influence of anions on the potassium status and productivity of kiwifruit (Actinidia deliciosa) vines 总被引:1,自引:0,他引:1
The effects of K fertiliser (160 kg ha-1) applied with Cl- or SO4
2- as the accompanying anion on the K nutrition of kiwifruit (Actinidia deliciosa var. deliciosa) were assessed in a field experiment, using vines with varying degrees of K deficiency. Leaf K concentrations in spring were significantly higher for vines receiving KCl, compared to those receiving K2SO4. This effect did not interact significantly with the degree of K deficiency, and persisted for about 6 weeks. Subsequently there was no significant difference between the leaf K concentrations for the vines receiving KCl or K2SO4. Applying K as KCl increased the leaf Cl concentration, especially in spring, while applying K as K2SO4 had no significant effect on the leaf S concentration at that time. These results implied a greater requirement for organic acid anions for K+ uptake from K2SO4 than from KCl, and the importance of organic acid anions for K+ uptake from different sources of K fertiliser is discussed. This transient effect of the accompanying anion on leaf K status was associated with large effects on flowering, and fruit yields were about 28% higher for plants receiving KCl rather than K2SO4.The effects on growth and tissue nutrient composition of varying the concentrations of Cl-, NO3
-, SO4
2- and H2PO4
- around the roots of kiwifruit vines were examined in a solution culture experiment. For H2PO4
-, plant growth was very similar over a wide range of rates of addition. For the other anions, the range between deficiency and toxicity was clearly delineated. For Cl- and NO3
-, toxicity was associated with high tissue concentrations of Cl and N, respectively, and was consistent with competition for uptake between Cl- and NO3
-. However, for SO4
2-, toxicity was associated with only a small increase in the tissue S concentration relative to that associated with maximum growth, and appeared to result more from effects on uptake of other anions and cations rather than from direct effects of high tissue S concentrations.It is concluded that the sensitivity of kiwifruit to the anion accompanying K+ in fertiliser may be related to the unusually high requirement for Cl previously reported for this species. 相似文献
15.
Solute concentrations in atmospheric deposition and stream water were measuredfrom 1984 through 1993 to determine the fate and mobility of solutes in twogauged mixed-conifer catchments (Tharp's and Log creeks) located in theSierra Nevada, California. The two catchments contain mature forest standsdominated by Abies concolor (white fir), Sequoiadendron giganteum (giantsequoia), Abies magnifica (red fir) and Pinus lambertiana (sugar pine).Ammonium, Cl-, Ca2+ and NO-
3were highest in concentration of the solutes measured in wet deposition;bulk deposition was highest in SO2-
4, NH+
4,Cl- and H+. Net retention ofH+, NO3
-, NH4
+,SO4
2- and Cl- occurred in both catchments.Discharge was dominated by spring snowmelt with the largest export yieldsfor acid neutralizing capacity (ANC), SiO2, andCa2+. Export yields of H+,NO3
-, NH4
+ and PO4
3-were relatively small (0.5 kg ha-1 y-1).Discharge-concentration relationships for ANC, SiO2,Na+, K+, Ca2+ andMg2+ were inverse and their concentrations in stream waterwere primarily influenced by discharge and annual differences in the relativecontributions of snowmelt and groundwater. The mobility of these solutes iscontrolled by the rates of mineral weathering and ion exchange. The positiverelationship of SO4
2- concentration with increasingdischarge suggests that atmospherically deposited SO4
2-is temporarily stored and that its release is controlled by the extent of soilwater flushing. 相似文献
16.
The effects of D-glucose, D-glyceraldehyde, glibenclamide, D-600, NH
4
+
and high concentrations of K+ on cytoplasmic pH (pH
i
) were investigated in dispersed and cultured pancreatic -cells fromob/ob mice. The cytoplasmic pH was measured with the fluorescent H+-indicator quene 1. The average pH
i
value in resting -cells was 6.71. Addition of 20 mM of the physiological stimulus D-glucose increased pH
i
with 0.05 units. Both glibenclamide and high concentrations of K+ decreased pH
i
. The latter effects were completely reversed by D-600, supporting the notion that free cytoplasmic Ca2+ can be involved in the regulation of pH
i
. In contrast to D-glucose, 10mM of D-glyceraldehyde decreased pH
i
by 0.09 units, an effect persisting even in the presence of D-600. From the present study it is evident that D-glyceraldehyde and D-glucose have opposite effects on pH
i
in pancreatic -cells. 相似文献
17.
Stream chemistry and hydrologic pathways during snowmelt in a small watershed adjacent Lake Superior 总被引:4,自引:2,他引:2
In regions with airborne contaminants and large snowpacks, there is concern over the impact that snowmelt chemical pulses — periods of sharp increase in meltwater solute concentration — could have on aquatic resources during spring runoff. A major variable in determining such an effect is the flow path of snowmelt solutes to the stream or lake. From December 1988, to late April 1989, the quality and quantity of precipitation, snowmelt, soil solution and streamwater were measured in a 176-ha gauged watershed on the south shore of Lake Superior. The main objectives were to (1) examine the change in flow path meltwaters take to the stream during distinct winter and spring hydrologic periods, (2) quantify ecosystem-level ion budgets prior to, during, and following snowmelt, and (3) examine if streamwater chemistry might be a sensitive indicator of change in ecosystem flow paths. Prior to peak snowmelt, groundwater made up 80% of stream discharge. During peak snowmelt, the groundwater level rose to the soil surface resulting in lateral water movement through near-surface macropores and as overland flow. Near the end of snowmelt, melt-waters exerted a piston action on deeper soil solution again increasing its relative contribution to streamwater discharge. Net groundwater drawdown during the study resulted in streamwater discharge about equal to precipitation inputs. Unfrozen soils and brief mid-winter thaws resulted in steady snowmelt throughout early and mid-winter. The snowpack lost > 50% of most ions prior to the period of major snowmelt and high stream discharge in late March and early April. Snowmelt and streamwater NO3
– and NH4 pulses occurred before the period of overland flow and peak streamwater discharge (April 4–24). During overland flow, stream discharge of total N, P, DOC, and AI peaked. Nutrient budgets computed for distinct hydrologic periods were much more helpful in explaining ecosystem pathways and processes than were changes in solute concentration. For the study period, watershed base cation (CB) discharge was 23 times input and SO4
2– discharge exceeded input by 42%. H+ was the most strongly conserved ion with output < 0.2% of input. Also conserved were NH4
+ with only 1.4% of input leaving the ecosystem and NO3
– with output equal to 9.4% of input. 相似文献
18.
Greg G. Goss Chris M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):635-646
Summary The novel application of a two-substrate model (Florini and Vestling 1957) from enzymology to transport kinetics at the gills of freshwater trout indicated that Na+/acidic equivalent and Cl-/basic equivalent flux rates are normally limited by the availability of the internal acidic and basic counterions, as well as by external Na+ and Cl- levels. Adult rainbow trout fitted with dorsal aortic and bladder catheters were chronically infused (10–16 h) with isosmotic HCl to induce a persistent metabolic acidosis. Acid-base neutral infusions of isosmotic NaCl and non-infused controls were also performed. Results were compared to previous data on metabolic alkalosis in trout induced by either isosmotic NaHCO3 infusion or recovery from environmental hyperoxia (Goss and Wood 1990a, b). Metabolic acidosis resulted in a marked stimulation of Na+ influx, no change in Cl- influx, positive Na+ balance, negative Cl- balance, and net H+ excretion at the gills. Metabolic alkalosis caused a marked inhibition of Na+ influx and stimulation of Cl- influx, negative Na+ balance, positive Cl- balance, and net H+ uptake (=base excretion). Mean gill intracellular pH qualitatively followed extracellular pH. Classical one-substrate Michaelis-Menten analysis of kinetic data indicated that changes in Na+ and Cl- transport during acid-base disturbance are achieved by large increases and decreases in Jmax, and by increases in Km. However, one-substrate analysis considers only external substrate concentration and cannot account for transport limitations by the internal substrate. The kinetic data were fitted successfully to a two-substrate model, using extracellular acid-base data as a measure of internal HCO
3
-
and H+ availability. This analysis indicated that true Jmax values for Na+/acidic equivalent and Cl-/basic equivalent transport are 4–5 times higher than apparent Jmax values by one-substrate analysis. Flux rates are limited by the availability of the internal counterions; transport Km values for HCO
3
-
and H+ are far above their normal internal concentrations. Therefore, small changes in acid-base status will have large effects on transport rates, and on apparent Jmax values, without alterations in the number of transport sites. This system provides an automatic, negative feedback control for clearance or retention of acidic/basic equivalents when acid-base status is changing.Abbreviations Amm
total ammonia in water
- DMO
55-dimethyl-24-oxyzolidine-dione
- Jin
unidirectional inward ion movement across the gill
- Jout
unidirectional outward ion movement across the gill
- Jnet
net transfer of ions (sum of Jin and Jout) across the gill
- Jmax
maximal transport rate for ion
- Km
inverse of affinity of transporter for ion
-
PIO2
partial pressure of oxygen in inspired water
- PaCO2
partial pressure of carbon dixide in arterial blood
- TAlk
titratable alkalinity of the water
- PEG
polyethylene glycol
- NEN
New England Nuclear 相似文献
19.
Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (C
i) was reduced by up to 30%. Salinization of plants was found to alter the 13C value of leaves of Phaseolus by up to 5 and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus C
i response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.Abbreviations and symbols A
net CO2 assimilation rate
- C
a
ambient CO2 concentration
-
C
i
intercellular CO2 concentration
- RuBP
ribulose-1,5-bisphosphate
- 13C
ratio of 13C to 12C relative to standard limestone 相似文献