共查询到20条相似文献,搜索用时 31 毫秒
1.
Cannabinoids were found to augment phospholipase activities and modify lipid levels of mouse brain synaptosomes, myelin and mitochondria. Delta-1-tetrahydrocannabinol (1-THC) and several of its metabolites induced a dose-dependent (0.32–16 M) stimulation of phospholipase A2 (PLA2) activity resulting in the increased release of free arachidonic acid from exogenous [1-14C]phosphatidylcholine (PC). The potencies of the cannabinoids in modulating PLA2 activity were approximately of the order: 7-OH-1-THC > 1-THC > 7-oxo-1-THC > 1-THC-7oic acid = 6 OH-1-THC 6-OH-1-THC. The hydrolysis of phosphatidylinositol (PI) by synaptosomal phospholipase C (PLC) was enhanced significantly by 1-THC and promoted diacylglyceride levels by greater than 100 percent compared to control values. In contrast, arachidonate was the major product resulting from phospholipase activities of a 20,000g pellet. Synaptosomal diacylglyceride lipase activity was inhibited by 1-THC. [1-14C]Arachidonic acid was readily incorporated into subcellular membrane phospholipids and after exposure to cannabinoids led to diminished phosphoglyceride levels and concomitant increases in released neutral lipid products. These data suggest that cannabinoids control phospholipid turnover and metabolism in mouse brain preparations by the activation of phospholipases and, through this mechanism, may exert some of their effects. 相似文献
2.
The transmembrane proton gradient of the sulfate-reducing bacterium Desulfovibrio desulfuricans strain CSN has been determined by in vivo31P nuclear magnetic resonance (NMR) spectroscopy in the absence of dioxygen. At pH 7.0 in the medium (pHex) the intracellular pH (pHin) was 7.5. By lowering pHex to 5.9 pHin decreased to 7.1. At pHex greater than 7.7 the transmembrane proton gradient (pH) was zero. The uncouplers 3,3,4,5-tetrachlorosalicylanilide (TCS) and carbonylcyanide-m-chlorophenylhydrazone (CCCP), or the permeant anion thiocyanate caused complete dissipation of pH.Abbreviations
CCCP
carbonylcyanide-m-chlorophenylhydrazone
-
TCS
3,3,4,5-tetrachlorosalicylanilide
-
MOPS
3-(N-morpholino)-propanesulfonic acid
-
P
i
inorganic phosphate
-
pH
in (pHex)
intracellular (extracellular) pH
- pH
transmembrane proton gradient (pHin-pHex)
-
electrochemical membrane potential
-
chemical shift in parts per million
-
NMR
nuclear magnetic resonance 相似文献
3.
G. Bertram A. Wessing 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(3):238-246
The functional significance of the apical vacuolar-type proton pump (V-ATPase) in Drosophila Malpighian tubules was studied by measuring the intracellular pH (pHi) and luminal pH (pHlu) with double-barrelled pH-microelectrodes in proximal segments of the larval anterior tubule immersed in nominally bicarbonate-free solutions (pHo 6.9). In proximal segments both pHi (7.43±0.20) and pHlu (7.10±0.24) were significantly lower than in distal segments (pHi 7.70±0.29, pHlu 8.09±0.15). Steady-state pHi of proximal segments was much less sensitive to changes in pHo than pH of the luminal fluid (pHlu/pHo was 0.49 while pHi/pHo was 0.18; pHo 6.50–7.20). Re-alkaliniziation from an NH4Cl-induced intracellular acid load (initial pHi recovery rate 0.55±0.34 pH·min-1) was nearly totally inhibited by 1 mmol·l-1 KCN (96% inhibition) and to a large degree (79%) by 1 mol·l-1 bafilomycin A1. In contrast, both vanadate (1 mmol·l-1) and amiloride (1 mmol·l-1) inhibited pHi recovery by 38% and 33%, respectively. Unlike amiloride, removal of Na+ from the bathing saline had no effect on pHi recovery, indicating that a Na+/H+ exchange is not significantly involved in pHi regulation. Instead pHi regulation apparently depended largely on the availability of ATP and on the activity of the bafilomycin-sensitive proton pump.Abbreviations DMSO
dimethylsulphoxide
- DNP
2,4-dinitrophenol
- NMDG
N-methyl-D-glucamine
- pHi
intracellular pH
- pHlu
pH of the luminal fluid
- pHo
pH of the superfusion medium
- I
intrinsic intracellular buffer capacity 相似文献
4.
Studies on animal material have revealed that changes in the mitochondrial permeability transition pore (PTP), which cause a reduction in the mitochondrial transmembrane potential (m) followed by release of cytochrome c, belong to the earliest manifestations of some types of apoptosis. We have attempted to monitor the m of mitochondria during programmed cell death (PCD) of the secretory tapetum using JC-1, a fluorochrome dye that detects mitochondrial membrane potential and to relate changes in this potential to mitochondrial ultrastructure. Analysis of tapetal cells isolated from Ornithogalum virens anthers revealed that the m of mitochondria in the tapetal cells alters during development; the change, however, is not uniform in the mitochondrial population within a single tapetal cell. In young tapetal cells, at the tetrad stage, we detected only the red fluorescence of JC-1 aggregates in all tapetal mitochondria, which indicates highly negative m. In an advanced stage of PCD at the late microspore stage, in each tapetal cell we detected both mitochondria with red (as formerly) and mitochondria with green fluorescence. The green fluorescence of JC-1 monomers indicates mitochondria with depolarised membranes. These changes in m are related to observed changes in mitochondria ultrastructure. This is the first documentation of intracellular heterogeneity of m during anther tapetum development. Alteration in m suggests a relationship between mitochondrial function and PCD processes in tapetal cells. 相似文献
5.
Ishverlal P. Pankhania Alfred M. Spormann W. Allan Hamilton Rudolf K. Thauer 《Archives of microbiology》1988,150(1):26-31
Cell suspensions of Desulfovibrio vulgaris were found to catalyze, in the absence of sulfate, the complete conversion of 1 lactate to 1 acetate, 1 CO2, and 2 H2 (G0=-8.8 kJ/mol) and of 1 pyruvate to 1 acetate, 1 CO2, and 1 H2 (G0=-52 kJ/mol). Protonophores, the proton translocating ATPase inhibitor N,N-dicyclohexylcarbodiimide, and arsenate specifically inhibited H2 formation from lactate but not from pyruvate. The results suggest that lactate oxidation to pyruvate and H2 (G
0=+43.2 kJ/mol) is energy driven. 相似文献
6.
Kevin Oxborough Ladislav Nedbal Roger A. Chylla John Whitmarsh 《Photosynthesis research》1996,48(1-2):247-254
In dark-adapted spinach leaves approximately one third of the Photosystem II (PS II) reaction centers are impaired in their ability to transfer electrons to Photosystem I. Although these inactive PS II centers are capable of reducing the primary quinone acceptor, QA, oxidation of QA
– occurs approximately 1000 times more slowly than at active centers. Previous studies based on dark-adapted leaves show that minimal energy transfer occurs from inactive centers to active centers, indicating that the quantum yield of photosynthesis could be significantly impaired by the presence of inactive centers. The objective of the work described here was to determine the performance of inactive PS II centers in light-adapted leaves. Measurements of PS II activity within leaves did not indicate any increase in the concentration of active PS II centers during light treatments between 10 s and 5 min, showing that inactive centers are not converted to active centers during light treatment. Light-induced modification of inactive PS II centers did occur, however, such that 75% of these centers were unable to sustain stable charge separation. In addition, the maximum yield of chlorophyll fluorescence associated with inactive PS II centers decreased substantially, despite the lack of any overall quenching of the maximum fluorescence yield. The effect of light treatment on inactive centers was reversed in the dark within 10–20 mins. These results indicate that illumination changes inactive PS II centers into a form that quenches fluorescence, but does not allow stable charge separation across the photosynthetic membrane. One possibility is that inactive centers are converted into centers that quench fluorescence by formation of a radical, such as reduced pheophytin or oxidized P680. Alternatively, it is possible that inactive PS II centers are modified such that absorbed excitation energy is dissipated thermally, through electron cycling at the reaction center.Abbreviations A518
absorbance change at 518 nm, reflecting the formation of an electric field across the thylakoid membrane
- AFL1
amplitude of the fast (<100 ms) phase of A518 induced by the first of two saturating, single-turnover flashes spaced 30 ms apart
- AFL2
amplitude of the fast (<100 ms) phase of A518 induced by the second of two saturating, single-turnover flashes spaced 50 ms apart
- DCBQ
2,6-dichloro-p-benzoquinone
- Fo
yield of chlorophyll fluorescence when QA is fully oxidized
- Fm
yield of chlorophyll fluorescence when QA is fully reduced
- Fx
yield of chlorophyll fluorescence when QA is fully reduced at inactive PS II centers, but fully oxidized at active PS II centers
- Pheo
pheophytin
- P680
the primary donor of Photosystem II
- PPFD
photosynthetic photon flux density
- QA
Primary quinone acceptor of PS II
- QB
secondary quinone acceptor of PS II 相似文献
7.
Plant growth substances (PGSs) were analysed in liquid endosperm of black walnut using HPLC and an ELISA procedure. Of all the PGSs studied, we show no GA3, low levels of cytokinins (io6A, i6Ade, i6Ado) and ABA, and very high level of IAAAbbreviations ABA
Abscisic acid:
- Ade
Adenine:
- GA3
Gibberellic acid:
- IAA
Indole-3-acetic acid:
- i6Ade
N6(2-1) adenine:
- i6Ado
N6(2-isopentenyl adenosine:
- io6A
Zeatin riboside: 相似文献
8.
Adam M. Gilmore Theodore L. Hazlett Peter G. Debrunner Govindjee 《Photosynthesis research》1996,48(1-2):171-187
Photosystem II (PS II) chlorophyll (Chl) a fluorescence lifetimes were measured in thylakoids and leaves of barley wild-type and chlorina f104 and f2 mutants to determine the effects of the PS II Chl a+b antenna size on the deexcitation of absorbed light energy. These barley chlorina mutants have drastically reduced levels of PS II light-harvesting Chls and pigment-proteins when compared to wild-type plants. However, the mutant and wild-type PS II Chl a fluorescence lifetimes and intensity parameters were remarkably similar and thus independent of the PS II light-harvesting antenna size for both maximal (at minimum Chl fluorescence level, Fo) and minimal rates of PS II photochemistry (at maximum Chl fluorescence level, Fm). Further, the fluorescence lifetimes and intensity parameters, as affected by the trans-thylakoid membrane pH gradient (pH) and the carotenoid pigments of the xanthophyll cycle, were also similar and independent of the antenna size differences. In the presence of a pH, the xanthophyll cycle-dependent processes increased the fractional intensity of a Chl a fluorescence lifetime distribution centered around 0.4–0.5 ns, at the expense of a 1.6 ns lifetime distribution (see Gilmore et al. (1995) Proc Natl Acad Sci USA 92: 2273–2277). When the zeaxanthin and antheraxanthin concentrations were measured relative to the number of PS II reaction center units, the ratios of fluorescence quenching to [xanthophyll] were similar between the wild-type and chlorina f104. However, the chlorina f104, compared to the wild-type, required around 2.5 times higher concentrations of these xanthophylls relative to Chl a+b to obtain the same levels of xanthophyll cycle-dependent fluorescence quenching. We thus suggest that, at a constant pH, the fraction of the short lifetime distribution is determined by the concentration and thus binding frequency of the xanthophylls in the PS II inner antenna. The pH also affected both the widths and centers of the lifetime distributions independent of the xanthophyll cycle. We suggest that the combined effects of the xanthophyll cycle and pH cause major conformational changes in the pigment-protein complexes of the PS II inner or core antennae that switch a normal PS II unit to an increased rate constant of heat dissipation. We discuss a model of the PS II photochemical apparatus where PS II photochemistry and xanthophyll cycle-dependent energy dissipation are independent of the Peripheral antenna size.Abbreviations Ax
antheraxanthin
- BSA
bovine serum albumin
- cx
lifetime center of fluorescence decay component x
- CP
chlorophyll binding protein of PS II inner antenna
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DTT
dithiothreitol
- fx
fractional intensity of fluorescence lifetime component x
- Fm, Fm
maximal PS II Chl a fluorescence intensity with all QA reduced in the absence, presence of thylakoid membrane energization
- Fo
minimal PS II Chl a fluorescence intensity with all QA oxidized
- Fv=Fm–Fo
variable level of PS II Chl a fluorescence
- HPLC
high performance liquid chromatography
- kA
rate constant of all combined energy dissipation pathways in PS II except photochemistry and fluorescence
- kF
rate constant of PS II Chl a fluorescence
- LHCIIb
main light harvesting pigment-protein complex (of PS II)
- Npig
mols Chl a+b per PS II
- NPQ=(Fm/Fm–1)
nonphotochemical quenching of PS II Chl a fluorescence
- PAM
pulse-amplitude modulation fluorometer
- PFD
photon-flux density, mols photons m–2 s–1
- PS II
Photosystem II
- P680
special-pair Chls of PS II reaction center
- QA
primary quinone electron acceptor of PS II
- Vx
violaxanthin
- wx
width at half maximum of Lorentzian fluorescence lifetime distribution x
- Zx
zeaxanthin
- pH
trans-thylakoid proton gradient
- % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% GabaqaaiGacaGaamqadaabaeaafiaakeaacqGH8aapcqaHepaDcqGH% +aGpdaWgaaWcbaGaamOraiaad2gaaeqaaaaa!4989!\[< \tau > _{Fm}\],% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% GabaqaaiGacaGaamqadaabaeaafiaakeaacqGH8aapcqaHepaDcqGH% +aGpdaWgaaWcbaGaamOraiaad+gaaeqaaOGaeyypa0Zaaabqaeaaca% WGMbWaaSbaaSqaaiaadIhaaeqaaOGaam4yamaaBaaaleaacaWG4baa% beaaaeqabeqdcqGHris5aaaa!50D3!\[< \tau > _{Fo} = \sum {f_x c_x }\]
average lifetime of Chl a fluorescence calculated from a multi-exponential model under Fm, Fo conditions 相似文献
9.
An NMR approach for determining the electron self-exchange (ESE) rate constants in blue copper proteins is presented. The approach uses the paramagnetic relaxation enhancement of resonances in 1D 1H super-WEFT spectra of partly oxidized (paramagnetic) proteins. These spectra allow a more precise determination of the relevant paramagnetic linebroadenings than conventional 1D 1H spectra and, thus, permit a more detailed investigation of the applicability of the linebroadenings for determining the electron exchange rates. The approach was used to estimate the ESE rate constant of plastocyanin from Anabaena variabilis. It was found that, although the rate constant can be determined accurately from a series of resonances, precise but erroneous constants are obtained from the resonances of the copper-bound residues, unless a narrow splitting of these resonances caused by the presence of two conformations is taken into account. As demonstrated here, this complication can be overcome by a correct analysis of the paramagnetic broadening of the combined double signals. Because of the high resolution and specific sensitivity of the approach it should be generally applicable to estimate electron transfer rates, k, if the paramagnetic relaxation enhancement R
2p of the resonances can be determined, and the conditions kR
2p or pkR
2p are fulfilled, p being the frequency separation between corresponding diamagnetic and paramagnetic sites. 相似文献
10.
Summary In-vivo phytochrome determinations in totally etiolated rice seedlings with a dual-wavelength spectrophotometer showed that on a fresh weight basis phytochrome concentration was highest in the coleoptile apex (0.175 of mean) ( O.D.) g-1 (fresh weight). The age of the seedlings had little effect on the pattern of phytochrome distribution in the coleoptiles.The extent of growth inhibition observed 2 days after the irradiations was proportional to the logarithm of P
fr amount in the coleoptiles at the time of initial exposure to either red or blue light. Ultraviolet irradiation, however, did not induce either reversible growth inhibition or optically detectable phytochrome changes in vivo.After the conversion of P
r to P
fr bya brief red irradiation, non-photochemical transformation of phytochrome was observed in intact coleoptile tissues. Most of the optically measurable P
fr disappeared within 6 hours at 27°, when the total ( O.D.) decreased to about one fifth of the original level. The optical data did not agree with the fact that 50% of the initial physiological reversibility was still observed 9 hours later. No significant difference in dark transformation rate was seen between intact and excised coleoptile tissues.Abbreviations
P
r
red light absorbing form of phytochrome
-
P
fr
far-red light absorbing form of phytochrome
- ( O.D.)
the change in the optical density difference reading at two wavelengths, following irradiation of the sample with actinic sources of red and far-red light
- UV
ultraviolet light 相似文献
11.
Summary Electrical potential differences across the plasma membrane () of the yeastPichia humboldtii were measured with microelectrodes (filled with 0.1m KCl) inserted into cells immobilized in microfunnels. The registered signals were reproducible and stable for several minutes. On attainment of stable reading for the specific membrane resistanceR
sp was determined by applying square-current pulses to the preparation. Both andR
sp were pH dependent and displayed equal but opposite deflection, reaching its maximal value of –88±9 mV (n=13) andR
sp its minimal value of 10 k·cm2 (maximal conductance) at pH 6.5. Uncouplers and the polyene antibiotic nystatin depolarized the cells, decreasing to –21±15 mV (n=10) with concomitant decrease ofR
sp. Comparison of values from microelectrode measurements with those calculated from the steady-state distribution of tetraphenylphosphonium ions agreed within 10 mV under all physiological conditions tested, except at pH values above 7.0. During microelectrode insertion transient voltage signals (a few msec long) were detected by means of an oscilloscope. These voltage signals were superimposed on the stable recordings described above. These short voltage signals disappeared in uncoupled cells. The closely related values obtained by two independent methods (direct measurements with microelectrodes and calculation from steady-state distribution of a lipophilic cation) provide evidence that these values reffect the true membrane potential of intact cells. 相似文献
12.
Irmgard Heiber-Langer Cécile Clery Johannes Franks Patrick Masson Claude Balny 《European biophysics journal : EBJ》1992,21(4):241-250
The reaction of methanol dehydrogenase with cytochrome c
L from Methylophaga marina and the reactions of the non-physiological substrates, Wurster's blue and ascorbic acid, with both proteins were studied as a function of temperature (4–32 °C), pressure (1–2000 bar) and ionic strength using the optical high pressure stopped-flow method. The thermodynamic parameters H, S and V were determined for all reactions where electron transfers are involved. These data allowed the determination of the Maxwell relationships which proved the internal thermodynamic consistency of the system under study. A conformational change on the cytochrome c
L level was deduced from both breaks in the Arrhenius plots and the variation of the V with temperature.Abbreviations MOPS
4-morpholinepropanesulfonic acid
- CHES
2-(cyclohexylamino)ethanesulfonic acid
- MDH
methanol dehydrogenase
- EDTA
ethylenedinitrilotetraacetic acid disodium salt
- BTB
bromothymol blue (3,3-dibromothymolsulfoneph-thalein)
- PQQ
2,7,9-tricarboxy-lH-pyrrolo-[2,3f]quinoline-4,5-dione
- cytochrome c
HH
mammalian horse heart cytochrome c 相似文献
13.
High energy state quenching of chlorophyll fluorescence (qE) is inhibited by low concentrations of the inhibitor antimycin A in intact and osmotically shocked chloroplasts isolated from spinach and pea plants. This inhibition is independent of any effect upon pH (as measured by 9-aminoacridine fluorescence quenching). A dual control of qE formation, by pH and the redox state of an unidentified chloroplast component, is implied. Results are discussed in terms of a role for qE in the dissipation of excess excitation energy within photosystem II.Abbreviations 9-AAmax =
Maximum yield of 9-aminoacridine fluorescence
- DCMU =
3(3,4-dichlorophenyl)-1,1-dimethylurea; Fmax ± Maximum yield of chlorophyll fluorescence
- hr =
hour
- PAR =
Photosynthetically Active Radiation
- QA =
Primary stable electron acceptor within photosystem II
- qE =
High energy state quenching of chlorophyll fluorescence
- qI =
quenching of chlorophyll fluorescence related to photoinhibition
- qP =
Quenching of chlorophyll fluorescence by oxidised plastoquinone
- qQ =
photochemical quenching of chlorophyll fluorescence
- qR =
(Fmax—maximum level of chlorophyll fluorescence induced by the addition of saturating DCMU)
- qT =
Quenching of chlorophyll fluorescence attributable to state transitions 相似文献
14.
Dr. R. V. Nair T. M. Masajo G. S. Khush 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,61(1):19-22
Summary The inheritance of resistance to whitebacked planthopper Sogatella furcifera (Horvath) was studied in 21 rice varieties. Reactions of F1; F2 and F3 progenies of the crosses of 21 resistant varieties with the susceptible variety TN 1 revealed that a single dominant gene governs resistance in Mushkan 41, Santhi, Siahnakidar 195, SM2-34, Tirisurkh 251, Zirijowaian 245, 18, 24A, 39, 76 S, 78, 180, 213 B, 267, 293, CI 6037-4, NP97, S39 JKW and Bansphul. In varieties 65 and 274 A, resistance is governed by one dominant and one recessive gene which segregate independently of each other. Tests for allelism with the Wbph 1 gene originally identified in N 22 revealed that the dominant gene present in all the test varieties is the same as Wbph 1. Further studies are required to determine the allelic relationships of the recessive gene found in varieties 65 and 274 A. 相似文献
15.
C. S. Spyropoulos 《The Journal of membrane biology》1979,47(3):195-238
Summary A previous method of measuring the swelling pressure (
g
) of the cytoplasmic gel of the giant axon ofLoligo vulgaris was refined. The estimates of
g
made with the improved method were consistent with those made with the earlier method. In these methods the activity of the solvent in the gel is measured by increasing the activity of the solvent in the internal phase of the gel by application of hydrostatic pressure to the gel directly. Comparable values for the activity of the solvent in the gel were obtained also by an alternate method, in which the deswelling of the gel is measured upon decreasing the activity of the solvent in the external phase by addition of a nonpenetrating high mol wt polymer (i.e., Ficoll).Additional support was obtained for the earlier suggestion that
g
contributes to the swelling and shrinkage pattern of the whole axon. In part, the new evidence involved two consecutivedirect measurements of intraxonal pressure. The first measurement was that of a mixed pressure composed of
g
and
m
(
m
being the effective osmotic pressure due to the intra-extraxonal gradient in the activity of mobile solutes). The subsequent measurement was that of
g
alone. The latter measurement was made feasible by destroying the axolemma, thereby eliminating the contribution of
m
. An estimate of
m
was obtained by subtracting
g
from the total pressure measured initially. The
m
determined by the above method was two orders of magnitude smaller than the theoretical osmotic pressure. This is consistent with the
m
determined previously, where osmotic intra-extraxonal filtration coefficients were compared to the hydrostatic. The mixed pressure experiments lend credence to the idea that the substantial contribution of
g
to the water relations of the whole axon is due to
g
being of the same order of magnitude as
m
.The degree of free swelling of axoplasmic gels was studied as a function of pH, salt concentration, and hydration radius of the anion of the salt used. The swelling increased with an increase in the reciprocal of the hydration radius, a decrease in salt concentration, and at pH below or above 4.5.The nature of the constraints to the free swelling of axoplasm in axons immersed in seawater was studied. With the seawater employed, these constraints appeared to be due more to the retractive forces of the sheath than to
m
. 相似文献
16.
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and . An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (L), root mass fraction (Rf), Pmax, and remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. L increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N.This revised version was published online in March 2005 with corrections to the page numbers. 相似文献
17.
We investigated the frequency-dependence of the flash-induced electrochromic absorbance change, A515, and of the pH-indicating absorbance change of neutral red in isolated intact chloroplasts. The energization pattern of thylakoids depended strongly on the frequency (f) of the exciting flashes, tested between 0.05 and 2 s–1. When the frequency was increased from 0.1 to 1 s–1 the total initial change and the slow rise of A515 decreased by about 30% and 70%, respectively, and both the slow rise and decay were considerably accelerated. These changes were fully reversible, even after prolonged excitation at 1 s–1, if the frequency was decreased again to 0.1 s–1. Accumulation of an appreciable transmembrane electric field strength could not be detected in any of our experiments, at high frequency, since the decay of A515 was considerably accelerated when the frequency was increased. In contrast, pH significantly increased at higher frequencies of the exciting flashes. In the steady-state (after about 100 flashes) pH was about 0.5–0.8 pH unit higher than in the dark or at low frequencies. In the presence of nigericin or dithionite, both of which prevented accumulation of protons in the lumen, the total initial change in A515 at f=1 s–1 relative to that at f=0.1 s–1 decreased to a similar extent as in the control. The proportion of the slow rise relative to the initial amplitude, however, did not decrease. Our data support the suggestion that pH controls the amplitude of the slow rise of A515. However, contrary to a previous statement (B. Bouges-Bouquet (1981) Biochim. Biophys. Acta 535, 327–340), we show that the pH effect cannot be accounted for by variation of the rate of this kinetic component of A515.Abbreviations DCMU
3(3,4-dichlorophenyl)-1,1-dimethylurea
- f
frequency of the exciting flashes
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- PS
photosystem 相似文献
18.
Jacque Topf Huashi Gong Rina Timberg Laurence Mets Itzhak Ohad 《Photosynthesis research》1992,32(1):59-69
Photoinhibition of Photosystem II in unicellular algae in vivo is accompanied by thylakoid membrane energization and generation of a relatively high pH as demonstrated by 14C-methylamine uptake in intact cells. Presence of ammonium ions in the medium causes extensive swelling of the thylakoid membranes in photoinhibited Chlamydomonas reinhardtii but not in Scenedesmus obliquus wild type and LF-1 mutant cells. The rise in pH and the related thylakoid swelling do not occur at light intensities which do not induce photoinhibition. The rise in pH and membrane energization are not induced by photoinhibitory light in C. reinhardtii mutant cells possessing an active Photosystem II but lacking cytochrome b6/f, plastocyanin or Photosystem I activity and thus being unable to perform cyclic electron flow around Photosystem I. In these mutants the light-induced turnover of the D1 protein of Reaction Center II is considerably reduced. The high light-dependent rise in pH is induced in the LF-1 mutant of Scenedesmus which can not oxidize water but otherwise possesses an active Reaction Center II indicating that PS II-linear electron flow activity and reduction of plastoquinone are not required for this process. Based on these results we conclude that photoinhibition of Photosystem II activates cyclic electron flow around Photosystem I which is responsible for the high membrane energization and pH rise in cells exposed to excessive light intensities.Abbreviations cyt b6/f
cytochrome b6/f
- Diuron
3-(3,4-dichlorophenyl)-1 dimethyl urea
- QB
the secondary quinone acceptor of reaction center II
- DNP
2,4,Dinitrophenol
- FCCP
carbonyl cyanide trifluoromethoxy phenylhydrazone
- SDS-PAGE
sodium dodecylsulfate polyacrylamide gel electrophoresis 相似文献
19.
N. J. Marshall M. F. Land 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,173(5):565-582
The optics of a variety of stomatopod eyes has been investigated using goniometric eye-mapping techniques and anatomical measurements. The species examined come from 3 of the 4 existing superfamilies: the Gonodactyloidea, Lysiosquilloidea and Squilloidea. This paper examines acuity, optical axes and general features of eye shape. Stomatopod eyes are divided into 3 clearly distinct zones; the mid-band and two hemispheres. Each hemisphere consists of an edge region, a visual streak and a near mid-band region. The optical axes of many ommatidia from both hemispheres are skewed inwards towards the centrally placed mid-band and are rarely normal to the corneal surface. The large skew angle enables each hemisphere to examine an area which extensively overlaps that of the other hemisphere. As a result monocular distance judgement is possible. Most of the ommatidia in each hemisphere are part of a horizontally aligned but vertically acute visual streak area. There is one visual streak per hemisphere and both look into the same 5–10° strip. This narrow strip is also the area in space the mid-band ommatidia examine. An acute zone is present in the eyes of lysiosquilloid and gonodactyloid stomatopods and includes ommatidia, from both the hemispheres and the mid-band. Here inter-ommatidial angles, especially those in the horizontal direction, are reduced. Acute zone facets are enlarged to increase sensitivity rather than aid spatial resolution.Abbreviations and definitions AZ
Acute Zone
- MB
Mid-band
-
D
Corneal facet diameter, as MB facets are asymmetrical, values for width and height of each facet are given
- DH
dorsal hemisphere
-
f
Focal length of each ommatidium, estimated from the centre of the corneal lens to the tip of the rhabdom
- NeMB
Near mid-band ommatidia
-
R
Resolving power=1/2average
- Rh
Horizontal resolving power=1/2h
- Rv
Vertical resolving power=1/2v
- VH
ventral hemisphere
-
Geometrical acceptance angle (a/f×57.3) of each ommatidium
- h
Horizontal inter-ommatidial angle, between facets along a row
- v
Vertical inter-ommatidial angle, between rows; Superfamily Gonodactyloidea
-
g.c.
Gonodactylus chiragra
-
O.s.
Odontodactylus scyllarus
-
H.e.
Hemisquilla ensigera; Superfamily Lysiosquilloidea
-
L.t.
Lysiosquilla tredecimdentata
-
C.s.
Coronis scolopendra; Superfamily Squilloidea
-
O.o.
Oratosquilla solicitans 相似文献
20.
Milan Höfer Klaas Nicolay George Robillard 《Journal of bioenergetics and biomembranes》1985,17(3):175-182
The electrochemical gradient of protons,
, was estimated in the obligatory aerobic yeastRhodotorula glutinis in the pH0 range from 3 to 8.5. The membrane potential, , was measured by steady-state distribution of the hydrophobic ions, tetraphenylphosphonium (TPP+) for negative above pH0 4.5, and thiocyanate (SCN–) for positive below pH0 4.5. The chemical gradient of H+ was determined by measuring the chemical shift of intracellular Pi by31P-NMR at given pH0 values. The values of pHi increased almost linearly from 7.3 at pH0 3 to 7.8 at pH0 8.5. In the physiological pH0 range from 3.5 to 6,
was fairly constant at values between 17–18 KJ mol–1, gradually decreasing at pH0 above 6. In deenergized cells, the intracellular pHi decreased to values as low as 6, regardless of whether the cell suspension was buffered at pH0 4.5 or 7.5. There was no membrane potential detectable in deenergized cells. 相似文献