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1.
The Permeability of the Guard Cell Plasma Membrane and Tonoplast 总被引:4,自引:0,他引:4
Uptake experiments and efflux compartmental analysis of planthormones, osmotica and toxins using isolated guardcells of Valerianella locusta and guard cell protoplasts (GCP)of Vicia faba were performed in order to study the permeabilityproperties of guard cell plasma membrane and tonoplast. Theplasma membrane of guard cells exhibits a higher permeabilitythan plasma membranes of mesophyll cells for most solutes investigated.The permeability coefficients (Ps calculated for the guard cellplasma membranes are also significantly higher than the Ps valuesfor the guard cell tonoplast. This applies also for protonatedABA. We suppose that the high permeability for ABAH could bepart of the target cell properties. A Collander analysis demonstratesa linear correlation between Ps, values and the ratio Kr/Mr1,5for both plasma membrane (r = 0.87) and for the tonoplast (r=0.93). Because of deviations from the observed correlations,the permeation of some solutes (ABA, GA, IAA through the tonoplast;methylamine through the plasma membrane) seems to be facilitatedby an additional transport mechanism. The Collander analysisof the plasma membrane of GCP shows very similar results tothe analysis of the plasma membrane of isolatedguard cells, indicating that isolation of protoplasts does notalter the permeability of the guard cell plasma membrane. Key words: Permeability coefficient, guard cells, plasma membrane, tonoplast 相似文献
2.
The Cl fluxes across the plasma membrane and the Clcontent of the acidresistant alga Dunaliella acidophila(optimal growthat pH 1.0, positive membrane potential) werestudied in the presence of 0.01300 mM Cl. Up to40 mM Cl in the medium, theinternal Cl concentrationis higher than that predicted by the electrochemical equilibrium,whereas at higher external Cl concentrations internalCl levels are lower than expected for the electrochemicalequilibrium. Growth in the absence of Cl is significantlylower than in the standard growth medium (2.2 mM Cl)and this reduction cannot be overcome by the addition ofothermonovalent anions such as Br or NO3 The latterimplies a specific Cl requirement in addition to therole of Cl as apermeant anion during ion translocations.Growth and photosynthesis tolerate an excess of Cl upto 300 mM (without stepwiseadaptation to increasing salinity).The uptake of Cl (measured by tracer techniques) exhibitsMichaelisMenten kinetics (KM = 0.75 mM Cl) andis stimulated by light and high H+ concentrations. Internalacidification by acetic acid causes an inhibition of Cluptake. The uptake of Cl is inhibited by the monovalentanions Br, I, and NO3 with K1, values notvery much different from the KM. value for Cl. The aniontransport inhibitors SITS and DIDS do not affect photosynthesis,but strongly suppressthe uptake of Cl. The Clchannel blockers A9C and NPPB cause inhibitionsof Cl uptake as well as of photosynthesis andthe ATPpool. FCCP strongly depresses the internal ATPpool withouta marked effect on Cl uptake. Cl efflux was inhibitedbyDIDS and SITS, but stimulated or inhibited by FCCP, dependingon the external Cl concentration. Results are in agreementwiththe hypothesis that Cl uptake into D. acidophila is dueto catalysed diffusion and is primarily independent of the hydrolysisofATP. Cl efflux is assumed to be coupled to an activepump. Data suggest tight cooperativity between the systemsresponsiblefor Cl uptake and Cl efflux, with thecytoplasmic pH and the membrane potential being important mediators. Key words: Acid resistance, chloride carrier, chloride channels, Dunaliella acidophila, membrane potential, plasma membrane 相似文献
3.
HARTMUT K. LICHTENTHALER 《Physiologia plantarum》1975,33(4):241-244
The kinetics of prenyl chain formation (C20 phytyl in chlorophylls, vitamin KI and α-tocopherol; C40 carotenoids and C45 in plastoquinone-9) in plastids of etiolated Hordeum seedlings was compared in continuous darkness and after far-red and white light treatments:
- 1 Continuous far-red (via phytochrome Pfr) enhances the synthesis rate of all prenyl chains, but does practically not change the dark pattern of prenyl chain accumulation. Free C20 phytyl chains could not be detected by means of thin layer chromatography.
- 2 White light induces a much stronger enhancement of prenyl chain formation than does far-red. It also changes the pattern of prenyl chain synthesis by a particularly strong promotion of the synthesis of phytyl chains, which get bound to chlorophyll a. The rate of chlorophyllide formation seems to determine the rate of enhanced phytyl formation.
- 3 It is assumed that the enzyme, which esterifies chlorophyllide a with the phytyl chain, is formed or activated by far-red treatment, but only starts working in white light, when the protochlorophyllide holochrome is re-arranged to the chlorophyllide holochrome.
4.
HARTMUT K. LICHTENTHALER 《Physiologia plantarum》1975,34(4):357-358
The effect of short pulses of red and or far-red light on the formation of individual carotenoids was tested in etiolated radish seedlings (Raphanus sativus L.). Red light induces an enhanced synthesis of β-carotene, lutein. violaxanthin and neoxanthin, while the level of antheraxanthin is decreased. Far-red light reverses the red light effects to the level of the far-red light control. The data indicate that in radish seedlings active phytochrome Pfr initiates the light-induced carotenoid synthesis, which is bound to thylakoid formation. 相似文献
5.
ANDREAS BAUMANN WERNER FESER PETER CRAMER RASOUL S. KERDAR HARTMUT BLODE JURGEN KORBER 《Biomarkers》2013,18(3):188-202
In the present study, a new in vitro model combining the short-term incubation of precision-cut human liver slices with DNA-adduct analysis by the 32P-postlabelling technique is proposed for investigation of the genotoxic potential of xenobiotics. For method validation, the metabolic turnover of testosterone (TES) and the DNA-adduct inducing potential of 2-aminofluorene (2-AF) were used. Precision-cut human liver slices were prepared from a total of 12 human liver samples which were freshly obtained as parts of resectates from liver surgery. The slices were incubated as submersion cultures with TES and 2-AF for up to 6 h in 12-well tissue culture plates at concentrations of 10-50 and 0.06-28 μM, respectively. Slices recovered from the slicing procedure in the 4 °C cold Krebs-Henseleit buffer as indicated by intracellular potassium concentrations which increased for 2 h and then remained stable until the end of the incubation. TES was extensively metabolized by human liver slices with a similar metabolite pattern as observed in vivo. Almost 90% of the metabolites were conjugates. Major phase-I metabolites were androstendione, 6β-OH-androstendione, 6β-OH-TES, and 15β-OHTES. After incubation with 2-AF, substance related DNA-adducts were detected which increased dose-dependently from 12 to 1146 adducts per 109 nucleotides. The adduct pattern consisted of one major adduct spot, A, representing 80-90% of the total adduct level and up to four minor adduct spots, B-E. In summary, the present data demonstrate that precision-cut liver slices are a valuable alternative in vitro system for DNA-adduct determination to screen chemicals for potential genotoxicity in humans. 相似文献
6.
MARKUS WEITERE REAS VOHMANN NADINE SCHULZ CATHERINE LINN DÉSIRÉE DIETRICH HARTMUT ARNDT 《Global Change Biology》2009,15(12):2838-2851
Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains. 相似文献
7.
CHRISTA FREUDENSTEIN HARTMUT BEUG STEVEN PALMIERI THOMAS GRAF 《Differentiation; research in biological diversity》1982,22(1-3):231-234
Cells prepared from 1-day-old chick blastoderms were infected with a temperature-sensitive mutant of avian erythroblastosis virus ( ts AEV). Clonal strains of transformed erythroblasts were isolated from the infected blastoderm cells. By shift to the nonpermissive temperature, these cells could be induced to differentiate into erythrocyte-like cells which expressed embryonic haemoglobins. Embryonic haemoglobins could not be detected in ts AEV-transformed erythroblasts from adult bone marrow when induced to differentiate under the same conditions. In contrast to normal primitive erythrocytes, ts AEV-infected embryonic erythroblasts differentiated in vitro expressed also adult haemoglobin. These results suggest an influence of the haematopoietic environment on the switch from embryonic to adult erythrocytes. 相似文献
8.
1. The abundance, production and control of pelagic heterotrophic nanoflagellates (HNF) in the Lower River Rhine (Germany) were investigated. Field samples (live‐counting technique) were taken at least every 2 weeks at Cologne (km 685) over a period of 20 months. In addition, Lagrangian sampling was carried out 160 km downstream of Cologne (Kalkar–Grieth, km 845) over a period of 12 months. Potential HNF growth rates and loss rates caused by planktonic predators were estimated in the laboratory (size fractionation experiments) and compared with the changes in HNF‐density in a water parcel flowing downstream. 2. Mean abundance (±SD) ranged from 7 ± 6 to 4890 ± 560 individuals mL–1 and was positively correlated with discharge. Heterotrophic nanoflagellates abundance increased up to 30‐fold during flood events, whereas there were only minor changes in the taxonomic composition. 3. HNF growth rate ranged from 0.16 ± 0.12 to 1.98 ± 0.10 day–1. Between 0 and 95% (mean: 32%) of the gross production was lost to planktonic predators; a larger portion between 0 and 195% (mean: 64%) of the HNF gross production was lost by other means. 4. There may be an important role for benthic predators in the control of pelagic HNF. First, production of HNF was high and grazing losses to planktonic predators low at times when HNF abundance was low. Secondly, high in situ loss rates (not explicable by planktonic predators), which were positively related to temperature, indicate the importance of biotic interactions. Thirdly, the dependence of HNF abundance on discharge indicated a decrease grazing intensity with rising water levels (increase in water volume/colonised river bed ratio). 5. The impact of discharge on planktonic HNF mediated by the grazing impact of benthic predators was modelled, showing a good fit with the field data. 相似文献
9.
Differential interference contrast micrographs from stretched animals, serially sectioned semi-thin and ultrathin sections revealed that the cerebral ganglia (supraoesophageal mass) of the eulardigrade Milnesium tardigradum lie above the buccal tube and adjacent tissue like a saddle. It has an anterior indentation which is penetrated by two muscles that arise from the cuticle of the forehead. The cerebral ganglia consist of lateral outer lobes bearing an eye on each side, and two inner lobes which extend caudally. Between the inner lobes a cone-like projection tapers into a nerve bundle. Each outer lobe is joined with the first ventral ganglion. From the outer lobe near the eye the ganglion for a posterolateral sensory field extends to the epidermis. Anterior to the supraoesophageal mass are three dorsal ganglia for the upper three peribuccal papillae. Two additional ganglia attached to the cerebral mass supply the lateral cephalic papillae. The cerebral ganglia are covered by a thin neural lamella. The pericarya which surround the neuropil have large nuclei. Near the axons in the centre of the supraoesophageal mass the cytoplasm is crowded with vesicles of different size and appearance. Some of them resemble synaptic vesicles while others resemble dense core bodies. Structurally different types of synapses and axons can be distinguished within the neuropil. 相似文献
10.
H. GIMMLER M. SCHIEDER M. KOWALSKI U. ZIMMERMANN U. PICK 《Plant, cell & environment》1991,14(3):261-269
Abstract. The zeta potential (which approximates the surface potential) of the acid resistant green alga Dunaliella acidophila (optimal growth at pH 1.0) and the salt resistant D. parva (grown at pH 7.6) were calculated from the electrophoretic mobility of cells as determined by means of free-flow electrophoresis. Dunaliella acidophila cells exhibit a positive zeta potential (+5 to +20mV) at acidic external pH values, whereas negative zeta potentials (-30 mV) were measured at neutral pH values. Negative zeta potentials of the same order of magnitude were also measured for D. parva cells (pH 7.6). Low concentrations of La3+ and A13+ did not affect the positive zeta potential of D. acidophila at acidic pH values, whereas higher concentrations caused a shift to more positive potentials. However, at neutral pH these cations caused a significant decrease of the negative zeta potential. The impermeant polycation poly-L-lysine acted in a similar manner to A13+ or La3+. The effect of Impermeant cations and anions on various physiological reactions also supports the existence of a positive zeta potential for D. acidophila and of a negative zeta potential for D. parva: polycations such as DEAE-dextran and poly-L-lysine strongly inhibitied photosynthesis and mobility of D. parva, but did not affect these reactions in D. acidophila. Comparable differential inhibitions were also observed for A13+ and La3+. Impermeant anions such as Dextran-sulfate exhibited effects in the opposite direction: inhibition was stronger with D. acidophila and weaker with D. parva. However, the differential inhibition by impermeant anions was much less pronounced in comparison with impermeant cations due to the relatively high pKa values of anionic solutes and consequently relatively high protonation at pH 1.0. The physiological consequences of an asymmetrically charged plasma membrane (excess of positive charges outside, excess of negative charges on the cytoplasmic side) of D. acidophila are discussed in regard to the extreme acid resistance of this alga and its resistance to cationic toxic solutes in industrial wastes. 相似文献