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1.
Koop JH Grieshaber MK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):75-83
Fluctuating salinities at different sites on the German salt-polluted rivers Werra and Weser were compared with extracellular
ion levels of specimens of Gammarus tigrinus (Sexton; Amphipoda, Crustacea), collected at the same sites. G. tigrinus regulated haemolymph concentrations of inorganic anions (Cl−, SO2−
4, PO3−
4) and cations (Na+, K+, Mg2+, Ca2+) during fluctuations of salt pollution in the upper Weser. This capacity to regulate varying levels of salt pollution in
the upper Weser, correlated well with the distribution of the brackish amphipods in this river ecosystem. G. tigrinus tolerated periods of Na+ and Cl− stress (>380 mmol l−1) without compensating these maxima by regulating extracellular Na+ and Cl−. However, during such bursts of Na+ and Cl− stress in Werra and Weser, the ability to regulate extracellular [K+] at river water K+ stress of ≥6.0 mmol l−1 may explain why this brackish species has been more successful in these rivers than its competitors like Gammarus pulex. The present investigation demonstrates that the water salinity affects the [NO−
3] in the haemolymph of G. tigrinus. With increasing hypo-osmotic stress the animals accumulate increasing amounts of NO−
3. A simultaneous increase in stream water [NO−
3] causes an additional accumulation of NO−
3 in the haemolymph. The high extent of accumulation indicates that active ion transport systems may be involved. The accumulation
of NO−
3 in the haemolymph has low physiological consequences to G. tigrinus, but when hypo-osmotically stressed under anoxic conditions, nitrite formed by the reduction of nitrate may have an adverse
affect on the metabolism of G. tigrinus.
Accepted: 4 October 1999 相似文献
2.
The accumulation of inorganic and organic osmolytes and their role in osmotic adjustment were investigated in roots and leaves
of vetiver grass (Vetiveria zizanioides) seedlings stressed with 100, 200, and 300 mM NaCl for 9 days. The results showed that, although the contents of inorganic
(K+, Na+, Ca2+, Mg2+, Cl−, NO3−, SO42− and H2PO3−)) and organic (soluble sugar, organic acids, and free amino acids) osmolytes all increased with NaCl concentration, the contribution
of inorganic ions (mainly Na+, K+, and Cl−) to osmotic adjustment was higher (71.50–80.56% of total) than that of organic solutes (19.43–28.50%). The contribution of
inorganic ions increased and that of organic solutes decreased in roots with the enhanced NaCl concentration, whereas the
case in leaves was opposite. On the other hand, the osmotic adjustment was only effective for vetiver grass seedlings under
moderate saline stress (less than 200 mM NaCl). 相似文献
3.
The paper presents the results of an examination of the phycical-chemical parameters of water together with an analysis of
the chlorophyll a concentration of 12 small water bodies situated within urban and suburban areas of the city of Poznań (mid-west Poland)—typical
mid-forest, strongly anthropogenically modified in the urban landscape, strongly antropogenically modified in an agricultural
area and clay-pits. There were zones of open water (Unvegetated Zone) as well as zones of rush and aquatic vegetation (Vegetated
Zone) distinguished in the examined ponds. The influence of the rush vegetation, nymphaeids and elodeids on the abiotic parameters
of an aquatic environment was examined. Water samples were taken during the summer of 2004 from 12 stations within the open
water and 24 within macrophytes. The plant matter was randomly collected in triplicate from the central part of the vegetated
stand. The influence of macrophytes on the abiotic features of water was estimated using the parameter of the plant length
(cm l−1) and the plant biomass (g l−1). In the studied ponds 12 aquatic macrophyte communities were distinguished. A salient feature of submerged macrophytes was
a great density of plant stems along with considerebly low biomass, however, the rush vegetation (Phragmitetum communis, Typhetum latifoliae) when compared to nymphaeids (Polygonetum natantis, Potametum natantis) and elodeids (Potametum lucentis) was characterised by lower stem densities and higher biomass. The water bodies were alkaline and of pronounced hardness.
In most of them high trophy conditions were found with especially high concentrations of phosphorus (96 μg l−1 on average). There was significant differentiation in the water chemistry (mainly in respect to mineral compounds) between
the Vegetated and Unvegetated Zones as well as between particular aquatic macrophyte communities. 相似文献
4.
为探究黄河三角洲湿地柽柳灌丛下土壤的盐渍化特征,在黄河三角洲国家级自然保护区(37°35''-12''N,118°33''-119°20''E)黄河入海口附近,根据长势基本一致的原则分别在碱蓬群落、柽柳群落和芦苇群落各选3株柽柳,采集柽柳灌丛下土壤样品,分析土壤盐分和盐碱化参数的空间分布以及距基茎不同距离处研究对象(土壤总盐(TS)、电导率(EC)、pH、交换性钠百分率(ESP))和环境因子(Na+、K+、Ca2+、Mg2+、Cl-、HCO3-、SO2-4)之间的关系。结果表明:(1)研究区土壤为弱碱化盐土,离子含量由高到低依次为Cl->Na+>SO2-4 >Ca2+>Mg2+>HCO-3>K+。除pH在土壤表层数值最低外,表层土壤TS、EC、ESP和盐分离子大于深层土壤,显示表聚性。(2)土壤盐分和盐碱化参数空间分布总体为:在柽柳基茎周围形成"盐谷"、"碱谷"效应, Na+、Mg2+、Cl-表现为"盐谷",K+ 、SO2-4 、Ca2+ 表现为"盐岛"。(3)在整个土壤剖面中,与TS、EC相关性最强的阴阳离子为Mg2+、Cl-,从灌丛中心到灌丛间裸地Ca2+、SO2-4与TS、EC的相关性逐渐减弱,Mg2+、Cl-与TS、EC的相关性逐渐增强。Ca2+和SO2-4与pH表现为较强的负相关性;与ESP相关性最强的阴离子为HCO-3,与之相关性最强的阳离子为Na+和K+,并且Na+和K+与ESP的相关性表现出从灌丛中心向外逐渐增强。(4)土壤盐渍化主要受控于Na+,从灌丛下到灌丛间裸地Cl-对盐渍化程度的影响逐渐增加,SO2-4的影响逐渐降低。 相似文献
5.
The chemical composition of rainwater is altered upon its passage through tree canopies. In order to investigate how rainwater
chemistry is affected by canopy-dependent processes in characteristic forest types of Northwest German sandy lowland regions
– oak–birch-forests, Betula pubescens Ehrh. swamp forests, and stands of Pinus sylvestris L. – comparative studies on the chemical composition of throughfall were carried out at seven forest sites, situated in close
proximity within a nature reserve. Additionally, rainwater was sampled at three heathland sites for analysis of open-field
precipitation and at three sites along an oak–birch-forest edge. Throughfall concentrations of most of the parameters analysed
were significantly higher than open-field concentrations, especially with regard to electric conductivity, NH4-N, K+, and KMnO4-index. Ion concentrations in throughfall were the lowest in a 10-year-old stand of Betula pendula Roth. and Pinus sylvestris and in a Betula pubescens swamp forest and were highest beneath a stand of Pinus sylvestris. Except for Na+, Cl−, and NO3−, ion concentrations in both throughfall and open-field precipitation increased during the growing season (May–October). In
throughfall, Ca2+, Mg2+, K+, and Mn2+ were strongly correlated. Enrichment ratios between throughfall and open-field deposition varied among sites and elements
and were the highest for K‰+, Mg2‰+, and Mn2‰+. Estimates of canopy leaching indicated high leaching rates of K‰+ and Mn2‰+ and moderate leaching of Mg2‰+. The contribution of foliar leaching to throughfall deposition was higher at the deciduous than at the coniferous stands. 相似文献
6.
Osmotic adjustment and ion balance traits of an alkali resistant halophyte Kochia sieversiana during adaptation to salt and alkali conditions 总被引:1,自引:0,他引:1
Chunwu Yang Jianna Chong Changyou Li Changmin Kim Decheng Shi Deli Wang 《Plant and Soil》2007,294(1-2):263-276
Kochia sieversiana (Pall.) C. A. M., a naturally alkali-resistant halophyte, was chosen as the test organism for our research. The seedlings
of K. sieversiana were treated with varying (0–400 mM) salt stress (1:1 molar ratio of NaCl to Na2SO4) and alkali stress (1:1 molar ratio of NaHCO3 to Na2CO3). The concentrations of various solutes in fresh shoots, including Na+, K+, Ca2+, Mg2+, Cl−, SO42−, NO3−, H2PO3−, betaine, proline, soluble sugar (SS), and organic acid (OA), were determined. The water content (WC) of the shoots was calculated
and the OA components were analyzed. Finally, the osmotic adjustment and ion balance traits in the shoots of K. sieversiana were explored. The results showed that the WC of K. sieversiana remained higher than 6 [g g−1 Dry weight (DW)] even under the highest salt or alkali stress. At salinity levels >240 mM, proline concentrations increased
dramatically, with rising salinity. We proposed that this was not a simple response to osmotic stress. The concentrations
of Na+ and K+ all increased with increasing salinity, which implies that there was no competitive inhibition for absorption of either in
K. sieversiana. Based on our results, the osmotic adjustment feature of salt stress was similar to that of alkali stress in the shoots of
K. sieversiana. The shared essential features were that the shoots maintained a state of high WC, OA, Na+, K+ and other inorganic ions, accumulated largely in the vacuoles, and betaine, accumulated in cytoplasm. On the other hand,
the ionic balance mechanisms under both stresses were different. Under salt stress, K. sieversiana accumulated OA and inorganic ions to maintain the intracellular ionic equilibrium, with close to equal contributions of OA
and inorganic ions to anion. However, under alkali stress, OA was the dominant factor in maintaining ionic equilibrium. The
contribution of OA to anion was as high as 84.2%, and the contribution of inorganic anions to anion was only 15.8%. We found
that the physiological responses of K. sieversiana to salt and alkali stresses were unique, and that mechanisms existed in it that were different from other naturally alkali-resistant
gramineous plants, such as Aneurolepidium chinense, Puccinellia tenuiflora.
Responsible Editor: John McPherson Cheeseman. 相似文献
7.
Sulian Lv Lingling Nie Pengxiang Fan Xuchu Wang Dan Jiang Xianyang Chen Yinxin Li 《Acta Physiologiae Plantarum》2012,34(2):503-513
Salicornia europaea is a succulent euhalophyte that belongs to the Chenopodiaceae family. It is found that moderate concentration of NaCl can
dramatically stimulate the growth of S. europaea plants. To elucidate the mechanism underlying the phenomenon, morphological and physiological changes of S. europaea in response to different ions, including cations (Na+, K+, Li+, Cs+) and anions (Cl−, NO3
−, CH3COO−) were investigated, and the effects of Na+, Cl− and K+ on the growth of S. europaea were also studied. Na+ was more effective than K+ and Cl− in stimulating shoot succulence, cell expansion, and stomatal opening. Plants treated with Na+ (including NaCl, Na+, NaNO3) showed better plant growth, increased photosynthesis and less cell membrane damage than those untreated and treated with
200 mM of Cl− and K+ (including KCl and KNO3). Both SEM-X-Ray microanalysis and flame emission results revealed that well developed S. europaea plants had a higher content of sodium but lower potassium and chlorine. It is concluded that sodium plays a more important
role in the growth and development of S. europaea than potassium and chloride. 相似文献
8.
Cl− currents (I
Cl) were measured in short fibers (1–2 mm) from the lumbricalis muscle of toads (Bufo arenarum) with two microelectrodes (15°C). Initially the fibers were equilibrated in a high K+-containing solution: (mm) K2SO4 68; Na2SO4 20; KCl 60; CaSO4 8; MgSO4 1; HEPES 2.5. Constant pulses were applied when all the external K+ was replaced by Cs+: Cs2SO4 68; Na2SO4 20; CsCl 60; CaSO4 8; HEPES 2.5 (pH 7.5). Under these conditions about 80–90% of the current is carried by Cl−. The current-voltage relation is almost linear implying constant conductance and hence voltage-independent permeability.
The voltage dependence of the net Cl− current could be fitted by constant field equation with a P
Cl of 3.3 × 10−6 cm/sec. In a separate group of experiments a two-pulse technique was used to estimate the availability and the inactivation
of the initial I
Cl during a test pulse. After returning the potential to the holding potential for various times, test pulses of the same amplitude
and duration of the prepulses were applied. The initial current during the test pulse was 70% of the initial current during
the prepulse and the recovery was complete in less than 300 msec with a linear relationship between the current during the
test pulse and the amplitude of the preceding prepulse. When the test pulses were preceded by a positive prepulse, the initial
current for any given test pulse was larger than with a negative prepulse. If we assumed that the initial current during the
test pulse is a measure of the number of channels open at the end of the prepulse, these results suggest that hyperpolarizing
pulses inactivate and depolarizing prepulses activate the I
Cl.
Received: 31 March 1995/Revised: 27 October 1995 相似文献
9.
F. Gagnon N.O. Dulin J. Tremblay P. Hamet S.N. Orlov 《The Journal of membrane biology》1999,167(2):193-204
P2U/2Y-receptors elicit multiple signaling in Madin-Darby canine kidney (MDCK) cells, including a transient increase of [Ca2+]
i
, activation of phospholipases C (PLC) and A2 (PLA2), protein kinase C (PKC) and mitogen-activated protein kinase (MAPK). This study examines the involvement of these signaling
pathways in the inhibition of Na+,K+,Cl− cotransport in MDCK cells by ATP. The level of ATP-induced inhibition of this carrier (∼50% of control values) was insensitive
to cholera and pertussis toxins, to the PKC inhibitor calphostin C, to the cyclic nucleotide-dependent protein kinase inhibitors,
H-89 and H-8 as well as to the inhibitor of serine-threonine type 1 and 2A phosphoprotein phosphatases okadaic acid. ATP led
to a transient increase of [Ca2+]i that was abolished by a chelator of Ca2+
i
, BAPTA. However, neither BAPTA nor the Ca2+ ionophore A231287, or an inhibitor of endoplasmic reticulum Ca2+-pump, thapsigargin, modified ATP-induced inhibition of Na+,K+,Cl− cotransport. An inhibitor of PLC, U73122, and an inhibitor of MAPK kinase (MEK), PD98059, blocked ATP-induced inositol-1,4,5-triphosphate
production and MAPK phosphorylation, respectively. However, these compounds did not modify the effect of ATP on Na+,K+,Cl− cotransport activity. Inhibitors of PLA2 (AACOCF3), cycloxygenase (indomethacin) and lypoxygenase (NDGA) as well as exogenous arachidonic acid also did not affect ATP-induced
inhibition of Na+,K+,Cl− cotransport. Inhibition of the carrier by ATP persisted in the presence of inhibitors of epithelial Na+ channels (amiloride), Cl− channels (NPPB) and Na+/H+ exchanger (EIPA) and was insensitive to cell volume modulation in anisosmotic media and to depletion of cells with monovalent
ions, thus ruling out the role of other ion transporters in purinoceptor-induced inhibition of Na+,K+,Cl− cotransport. Our data demonstrate that none of the known purinoceptor-stimulated signaling pathways mediate ATP-induced inhibition
of Na+,K+,Cl− cotransport and suggest the presence of a novel P2-receptor-coupled signaling mechanism.
Received: 29 July 1998/Revised: 19 October 相似文献
10.
Orlov SN Dulin NO Gagnon F Gekle M Douglas JG Schwartz JH Hamet P 《The Journal of membrane biology》1999,172(3):225-234
We demonstrated recently that in renal epithelial cells from collecting ducts of Madin-Darby canine kidneys (MDCK), Na+,K+,Cl− cotransport is inhibited up to 50% by ATP via its interaction with P2Y purinoceptors (Biochim. Biophys. Acta 1998. 1369:233–239). In the present study we examined which type of renal epithelial cells possesses the highest sensitivity of Na+,K+,Cl− cotransport to purinergic regulation. We did not observe any effect of ATP on Na+,K+,Cl− cotransport in renal epithelial cells from proximal and distal tubules, whereas in renal epithelial cells from rabbit and
rat collecting ducts ATP decreased the carrier's activity by ∼30%. ATP did not affect Na+,K+,Cl− cotransport in C7 subtype MDCK cells possessing the properties of principal cells but led to ∼85% inhibition of this carrier
in C11-MDCK cells in which intercalated cells are highly abundant. Both C7- and C11-MDCK exhibited ATP-induced IP3 and cAMP production and transient elevation of [Ca2+]
i
. In contrast to the above-listed signaling systems, ATP-induced phosphorylation of ERK and JNK MAP kinases was observed in
C11-MDCK only. Thus, our results reveal that regulation of renal Na+,K+,Cl− cotransport by P2Y receptors is limited to intercalated cells from collecting ducts and indicate the involvement of the MAP kinase cascade in
purinergic control of this ion carrier's activity.
Received: 10 June 1999/Revised: 23 August 1999 相似文献
11.
Forest ecosystems are self-fertilizing systems, and development of forest stands depends on nutrient supply via biogeochemical
cycling within the ecosystem. Therefore, it is important to clarify the nutrient cycle mediating growth and development. In
addition, long-term hydrochemical monitoring is needed to understand the influence of environmental changes on biogeochemical
cycling in forest ecosystems. The Oyasan Experimental Forest Watershed (OEFW) is located in the Field Museum Oyasan, the university
forest of Tokyo University of Agriculture and Technology, in Gunma prefecture, Japan. OEFW comprises two small adjacent forested
watersheds—A-watershed and B-watershed—with respective areas of 1.3 and 1.8 ha. A-watershed is a reestablished forest planted
with sugi (Japanese cedar; Cryptomeria japonica) and hinoki (Japanese cypress; Chamaecyparis obtusa) in 1976, and has been managed intensively with fertilizer application. By contrast, B-watershed is an established forest
planted with sugi and hinoki in 1907. No forest practices have been carried out except for thinning of suppressed trees in
1983. However, the sugi plantation on the lowest slope (18% of the watershed area) was cut in 2000, and sugi was replanted
the following year. In this data paper, we present data on the daily precipitation, discharge, pH, and concentrations of major
nutrients (Ca2+, Mg2+, K+, Na+, NH4
+, Cl−, NO3
−, and SO4
2−) in rainwater and stream water since November 1978. The arithmetical mean pH of precipitation, stream water in A- and B-watershed
from the beginning of the monitoring to the present were 4.77 ± 0.67, 6.85 ± 0.41 and 6.88 ± 0.36 (average ± SD), respectively.
The arithmetical mean concentrations in precipitation in mmolc L−1 were 0.030 ± 0.030 for Ca2+, 0.010 ± 0.011 for Mg2+, 0.009 ± 0.013 for K+, 0.020 ± 0.024 for Na+, 0.035 ± 0.041 for NH4
+, 0.026 ± 0.029 for Cl−, 0.033 ± 0.038 for NO3
−, and 0.046 ± 0.043 for SO4
2−. The mean concentrations in stream water in A-watershed were 0.180 ± 0.032 for Ca2+, 0.073 ± 0.013 for Mg2+, 0.018 ± 0.009 for K+, 0.182 ± 0.024 for Na+, 0.010 ± 0.010 for NH4
+, 0.060 ± 0.008 for Cl−, 0.111 ± 0.038 for NO3
−, and 0.074 ± 0.012 for SO4
2−; whereas for B-watershed the mean concentrations were 0.169 ± 0.025 for Ca2+, 0.079 ± 0.016 for Mg2+, 0.018 ± 0.005 for K+, 0.192 ± 0.026 for Na+, 0.010 ± 0.010 for NH4
+, 0.065 ± 0.010 for Cl−, 0.093 ± 0.025 for NO3
−, and 0.087 ± 0.011 for SO4
2−. 相似文献
12.
Potassium (K+) and chloride (Cl−) are two essential elements for plant growth and development. While it is known that plants possess specific membrane transporters
for transporting K+ and Cl−, it remains unclear if they actively use K+-coupled Cl− cotransporters (KCC), as used in animals, to transport K+ and Cl−. We have cloned an Oryza sativa cDNA encoding for a member of the cation–Cl− cotransporter (CCC) family. Phylogenetic analysis revealed that plant CCC proteins are highly conserved and that they have
greater sequence similarity to the sub-family of animal K+–Cl− cotransporters than to other cation–Cl− cotransporters. Real-time PCR revealed that the O. sativa cDNA, which was named OsCCC1, can be induced by KCl in the shoot and root and that the expression level was higher in the leaf and root tips than in any
other part of the rice plant. The OsCCC1 protein was located not only in onion plasma membrane but also in O. sativa plasma membrane. The OsCCC1 gene-silenced plants grow more slowly than wild-type (WT) plants, especially under the KCl treatment regime. After 1 month
of KCl treatment, the leaf tips of the gene-silenced lines were necrosed. In addition, seed germination, root length, and
fresh and dry weight were distinctly lower in the gene-silenced lines than in WT plants, especially after KCl treatment. Analysis
of Na+, K+, and Cl− contents of the gene-silenced lines and WT plants grown under the NaCl and KCl treatment regimes revealed that the former
accumulated relatively less K+ and Cl− than the latter but that they did not differ in terms of Na+ contents, suggesting OsCCC1 may be involved in K+ and Cl− transport. Results from different tests indicated that the OsCCC1 plays a significant role in K+ and Cl− homeostasis and rice plant development. 相似文献
13.
Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline
conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate
the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4
of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty
loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period.
Spatial distributions of fresh weight (FW), dry weight (DW), and Na+, K+, Cl−, NO−
3, Ca2+, Mg2+, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial
distribution of Na+, Cl−, K+, NO3
−, and Ca2+ in the growing leaves were affected by salinity, while those of Mg2+, total P, and total N were not. Sodium, K+, Cl−, Ca2+, Mg2+, and total N concentrations (mmol · kg−1 FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO3
− concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation
zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na+, Cl−, Ca2+, and Mg2+ (mmol · kg−1 FW · h−1) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO3
− this was depressed. The lower supply of NO−
3 to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of
Na+ and Cl− may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca2+, Mg2+, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K+ and Ca2+ concentrations at 120 mM NaCl are probably due to the presence of high Ca2+ in the soil of this study.
Received: 13 March 1997 / Accepted: 9 June 1997 相似文献
14.
C. E. Crocker G. R. Ultsch D. C. Jackson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):249-255
We examined changes in blood gases, plasma ions, and acid-base status during prolonged submergence (6 h) of four aquatic
turtle species in aerated water at 20 °C. Our objective was to determine whether the temperate species, Chrysemys picta bellii, exhibits greater tolerance to submergence apnea than the tropical species, Pelomedusa subrufa, Elseya novaeguineae, and Emydura subglobosa. Blood was sampled from indwelling arterial catheters for measurements of blood PO2, PCO2, pH, and hematocrit and for plasma concentrations of lactate, glucose, Na+, K+, Cl−, total Ca, and total Mg. The pattern of change was similar in all species: a combined respiratory and metabolic acidosis
associated with a marked decrease of blood PO2. The severity of the acidosis developed in the temperate species, however, was significantly less than that of the tropical
turtles. Lactate rose significantly and HCO3
− fell proportionately in all turtles; changes in other plasma ion concentrations were small but were generally in the directions
consistent with compensatory exchanges with other body compartments; i.e., cations (K+, Ca, and Mg increased) and anions (Cl− decreased). The results indicate that hypoxia tolerance is a conserved trait in turtles, even in those that do not experience
enforced winter submergence, and that the temperate species may be superior in this capacity because of reduced metabolic
rate.
Accepted: 3 March 1999 相似文献
15.
In frog red blood cells, K-Cl cotransport (i.e., the difference between ouabain-resistant K fluxes in Cl and NO3) has been shown to mediate a large fraction of the total K+ transport. In the present study, Cl−-dependent and Cl−-independent K+ fluxes via frog erythrocyte membranes were investigated as a function of external and internal K+ ([K+]
e
and [K+]
i
) concentration. The dependence of ouabain-resistant Cl−-dependent K+ (86Rb) influx on [K+]
e
over the range 0–20 mm fitted the Michaelis-Menten equation, with an apparent affinity (K
m
) of 8.2 ± 1.3 mm and maximal velocity (V
max
) of 10.4 ± 1.6 mmol/l cells/hr under isotonic conditions. Hypotonic stimulation of the Cl−-dependent K+ influx increased both K
m
(12.8 ± 1.7 mm, P < 0.05) and V
max
(20.2 ± 2.9 mmol/l/hr, P < 0.001). Raising [K+]
e
above 20 mm in isotonic media significantly reduced the Cl−-dependent K+ influx due to a reciprocal decrease of the external Na+ ([Na+]
e
) concentration below 50 mm. Replacing [Na+]
e
by NMDG+ markedly decreased V
max
(3.2 ± 0.7 mmol/l/hr, P < 0.001) and increased K
m
(15.7 ± 2.1 mm, P < 0.03) of Cl−-dependent K+ influx. Moreover, NMDG+ Cl substitution for NaCl in isotonic and hypotonic media containing 10 mm RbCl significantly reduced both Rb+ uptake and K+ loss from red cells. Cell swelling did not affect the Na+-dependent changes in Rb+ uptake and K+ loss. In a nominally K+(Rb+)-free medium, net K+ loss was reduced after lowering [Na+]
e
below 50 mm. These results indicate that over 50 mm [Na+]
e
is required for complete activation of the K-Cl cotransporter. In nystatin-pretreated cells with various intracellular K+, Cl−-dependent K+ loss in K+-free media was a linear function of [K+]
i
, with a rate constant of 0.11 ± 0.01 and 0.18 ± 0.008 hr−1 (P < 0.001) in isotonic and hypotonic media, respectively. Thus K-Cl cotransport in frog erythrocytes exhibits a strong asymmetry
with respect to transported K+ ions. The residual, ouabain-resistant K+ fluxes in NO3 were only 5–10% of the total and were well fitted to linear regressions. The rate constants for the residual influxes were
not different from those for K+ effluxes in isotonic (∼0.014 hr−1) and hypotonic (∼0.022 hr−1) media, but cell swelling resulted in a significant increase in the rate constants.
Received: 19 November 1998/Revised: 23 August 1999 相似文献
16.
Summary The N-metabolism ofArthrocnemum fruticosum (L.) Moq., growing in a saline area north-east of the Dead Sea in Jordan, was studied over its vegetative growth period from
March to September 1981. Plant and soil samples were taken at monthly intervals. Water content, Na+, K+, Cl−, NH
4
+
, NO
2
−
and NO
3
−
concentrations were determined in the soil extracts, and the same determinations plus ash weight, soluble carbohydrates,
proline, proteins andin vivo nitrate reductase in the plant roots and shoots.
Soil humidity decreased and salinity increased from March to August, with re-wetting occurring in late July. K+ and Cl− were much lower in the soils than Na+. Plant relative dry weight increased during summer due to the absorption of Na+ in addition to increased organic dry weight. The uptake of Na+ was not balanced by a similar uptake of Cl−.
Ammonium and nitrate decreased in soil and plants in parallel with increasing salinity. Nitrite was only found in the roots
and always in very low quantities. Proline was found only in March. The total soluble carbohydrates in the roots showed a
short increase in June when the sodium in the plants also increased. It was concluded that carbohydrates may be used to balance
osmotic shocks, but that another compatible compounds is necessary to maintatin long-term osmotic equilibrium.
The nitrate reductase activity, measuredin vivo, and the soluble protein changed roughly in parallel with the internal nitrate from May to August, suggesting that nitrogen
uptake and reduction in the plant is inhibited during summer when the soil is dry and very saline. This could be a direct
effect of drought and/or salinity on the plants, or an indirect onevia an inhibition of nitrifying bacteria. 相似文献
17.
Analysis of salts transport affected by root absorption capacity in surface — irrigated fields in the upper Yellow River basin 总被引:1,自引:0,他引:1
Daisuke Yasutake Takuya Araki Weizhen Wang Tetsuo Kobayashi Hiroyuki Cho Makito Mori Masaharu Kitano 《Biologia》2009,64(3):570-574
In order to analyze the salt transport affected by roots and its effects on soil salinity in an experimental irrigated field
newly established in an alluvial valley of the Yellow River in China, spatial distribution of ions contained in waters, soils
and crops relevant to these phenomena were evaluated there. During the intensive surveys conducted in year 2007–2008, the
Yellow River water, irrigation canal water, groundwater, field soils and crops, etc. were sampled and their chemical characteristics
such as electrical conductivity, concentrations of ions Na+, Ca2+, Mg2+, K+, Cl−, SO42−and NO3− were measured. Irrigation seemed to cause increases in the concentrations of ions Na+, Cl− and SO42− in the groundwater. Although those were also major ions contained in the field soil, the soil was classed as saline but not
sodic according to the standard classification. On the other hand, K+, which is one of the major essential nutrients for plant growth, was highly concentrated in the crops, while Na+ was not concentrated because of crop’s poor ability to absorb it. The ion concentration within the plant body seemed to be
reflected by the active and selective ion uptake by roots and the transpiration stream. Furthermore, salt accumulation in
the surface-irrigated field largely depended on the upward transport of water and ions in the soil profile affected by root
absorption capacity. The information obtained in this study will contribute to the development of scientific methods for sustainable
and effective plant production in irrigated fields. 相似文献
18.
To examine the involvement of Na+,K+,2Cl− cotransport in monovalent ion fluxes in vascular smooth muscle cells (VSMC), we compared the effect of bumetanide on 86Rb, 36Cl and 22Na uptake by quiescent cultures of VSMC from rat aorta. Under basal conditions, the values of bumetanide-sensitive (BS) inward
and outward 86Rb fluxes were not different. Bumetanide decreased basal 86Rb uptake by 70–75% with a K
i
of ∼0.2–0.3 μm. At concentrations ranging up to 1 μm, bumetanide did not affect 36Cl influx and reduced it by 20–30% in the range from 3 to 100 μm. In contrast to 86Rb and 36Cl influx, bumetanide did not inhibit 22Na uptake by VSMC. BS 86Rb uptake was completely abolished in Na+- or Cl−-free media. In contrast to 86Rb, basal BS 36Cl influx was not affected by Na+
o
and K+
o
. Hyperosmotic and isosmotic shrinkage of VSMC increased 86Rb and 36Cl influx to the same extent. Shrinkage-induced increments of 86Rb and 36Cl uptake were completely abolished by bumetanide with a K
i
or ∼0.3 μm. Shrinkage did not induce BS 86Rb and 36Cl influx in (Na+ or Cl−)- and (Na+ or K+)-depleted media, respectively. In the presence of an inhibitor of Na+/H+ exchange (EIPA), neither hyperosmotic nor isosmotic shrinkage activated 22Na influx. Bumetanide (1 μm) did not modify basal VSMC volume and intracellular content of sodium, potassium and chloride but abolished the regulatory
volume increase in isosmotically-shrunken VSMC. These data demonstrate the absence of the functional Na+,K+,2Cl− cotransporter in VSMC and suggest that in these cells basal and shrinkage-induced BS K+ influx is mediated by (Na+
o
+ Cl−
o
)-dependent K+/K+ exchange and Na+
o
-dependent K+,Cl− cotransport, respectively.
Received: 30 January 1996/Revised: 20 May 1996 相似文献
19.
Saeed Hajirezaee Bagher Mojazi Amiri Ali Reza Mirvaghefi 《Journal of Ichthyology》2010,50(11):1070-1076
To assay the effects of stripping frequency on semen characteristics of Caspian brown trout, Salmo trutta caspius, the chemical composition of seminal fluid, sperm production (semen volume, sperm density, spermatocrit,) and sperm motility
characteristics (percentage and duration of motility) were investigated over four times stripping during the spawning season.
According to data, semen volume, sperm density, osmolality and the concentrations of Na+, Cl−, K+, Ca2+, Mg2+ and total protein gradually decreased by increasing of stripping frequency. The values of glucose and triglyceride had no
significant changes over four times stripping. Also, the values of semen pH, the percentage (5 s after activation) and duration
of motility were statistically stable until third stripping but a decrease was recorded for these parameters in the fourth
stripping. As well as, significant positive correlations were found for sperm density vs. K+, Cl−, Na+, Ca2+, Mg2+, total protein, spermatocrit; the percentage of motile spermatozoa vs. Ca2+, Mg2+, K+, Cl−, Na+, total protein, and also the duration of motility vs. K+, Cl−, total protein and pH. In text, specific objectives of this study have been expressed. 相似文献
20.
Effects of Anions on the Capacity and Affinity of Copper Adsorption in Two Variable Charge Soils 总被引:2,自引:0,他引:2
Effects of nitrate,(NO3−) chloride (Cl−), sulfate (SO42-, and acetate (Ac−) on Cu2+ adsorption and affinity of the adsorbed Cu2+ were evaluated in two Fe and Al enriched variable charge soils from Southern China. The maximum adsorption of Cu2+ (M, a parameter from the Langmuir isotherm model) in the presence of different anions decreased in the order
Cl− > Ac− > NO3− > SO42- for both soils. The clayey loamy soil (mixed siliceous thermic Typic Dystrochrept, TTD), developed on the Arenaceous rock,
adsorbed less Cu2+ than the clayey soil (kaolinitic thermic Plinthudults, KTP), derived from the Quaternary red earths, regardless of anion
type present in the medium. The affinity of adsorbed Cu2+ to both soils could be characterized by the Kd (distribution coefficient) values and successive extraction of the adsorbed Cu2+ with 1-mol NH4Ac L−1. The log10Kd value was smaller for the TTD soil than for the KTP soil and decreased in the order of Cl− > NO3− > SO42- > Ac−
at low initial Cu2+ concentrations (≤40 mg Cu2+L−1), whereas at 80 mg Cu2+L−1, the log10Kd value was similar for NO3−, SO42-, and Ac−, but was slightly higher for Cl−. Complete extraction of Cu2+ adsorbed in the presence of Ac− was achieved. Influence of NO3− and SO42- on the affinity of adsorbed Cu2+ was similar, but the effects of Cl− depended on the initial Cu2+ concentrations. The extracted percentage of the adsorbed Cu2+ in the presence of NO3− or SO42- increased with increasing Cu2+ adsorption saturation. The presence of Cl−, NO3−, or SO42- markedly decreased the equilibrium solution pH for both soils with increasing initial Cu2+ concentrations, and the delta pH values at the highest Cu2+ level were 0.5, 0.63, and 0.55 U for the TTD soil and 0.79, 0.84, and 0.93 U for the KTP soil, respectively for the three
anions. The presence of Ac− had a minimal influence on the equilibrium solution pH because of the buffering nature of the NaAc/HAc medium which buffered
the released protons. The effects of anions on Cu2+ adsorption and affinity of the adsorbed Cu2+ were dependent on anion types and were apparently related to the altered surface properties caused by anion adsorption and/or
the formation of anion– Cu2+ complexes. 相似文献