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31.
Thylakoids isolated from peas (Pisum sativum cv. Kelvedon Wonder) and phosphorylated by incubation with ATP have been compared with non-phosphorylated thylakoids in their sensitivity to photoinhibition by exposure to illumination in vitro. Assays of the kinetics of fluorescence induction at 20° C and the fluorescence emission spectra at-196° C indicate a proportionally larger decrease in fluorescence as a result of photoinhibitory treatment of non-phosphorylated compared with phosphorylated thylakoids. It is concluded that protein phosphorylation can afford partial protection to thylakoids exposed to photoinhibitory conditions.Abbreviations and symbols DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
-
F
0
Level of chlorophyll fluorescence when photosystem 2 traps are open
-
F
m
Level of chlorphyll fluorescence when photosystem 2 traps are closed
- P
Maximum level of fluorescence reached in the absence of DCMU
- PSI (II)
photosystem I(II) 相似文献
32.
Photoacoustic and fluorescence measurements of the chilling response and their relationship to carbon dioxide uptake in tomato plants 总被引:5,自引:0,他引:5
The response of tomato plants to various chilling treatments was studied using two approaches for the measurement of photosynthetic activity. One involved the use of a portable fluorometer for the measurement of in-vivo chlorophyll fluorescence, while the other employed a newly introduced photoacoustic system which allowed changes in oxygen evolution to be followed in a leaf disc. A strong correlation was found between results obtained by each system and those obtained by a conventional open gas-exchange system for the determination of CO2 uptake. Both systems of measurements could readily distinguish between the effects of chilling in the dark (at 3° C for 18 h) and chilling at high photon flux density (2000 mol m-2 s-1 for 5h at 5° C). Chilling in the dark had practically no effect on the quantum yield of oxygen evolution, chlorophyll fluorescence or CO2 uptake, while chilling at excessively high photon flux density resulted in a sharp reduction (50–70%) in the quantum yields obtained. The results support the view that photosystem II cannot be the primary site of damage by chilling in the dark, although it is significantly affected by chilling at high light intensity.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- PA
photoacoustic
- PFD
photon flux density
- PSII
photosystem II 相似文献
33.
The effects of light and several photosynthetic inhibitors on the rate of sulfite metabolism in cells obtained from Cucumis sativus L. cotyledons was studied. The cells were treated with 200 M Na2SO3 and the disappearance of sulfite was monitored using either dithiobisnitrobenzoic acid or fuchsin. The rate of sulfite disappearance in light was double the dark rate. Disalicylidene propanediamine at 1 mM increased this light-enhanced metabolism approx. 50%; neither 1 M 3,4-dichlorophenyl-N,N-dimethylurea nor 0.1 mM cyanazine, which completely inhibited CO2-dependent oxygen evolution, affected the rate of sulfite metabolism. Addition of 200 M Na2SO3 to the cells partially inhibited 14CO2 fixation. The rate of sulfite consumption by the cells did not affect this inhibition. We conclude that light-dependent sulfite metabolism is cucumber cells may utilize reduced ferredoxin generated as a result of photosynthetic electron transport. An injurious interaction between CO2 fixation and sulfite appears to occur independently of the sulfite-metabolism process.Abbreviations DCMU
3,4-dichlorophenyl-N,N-dimethylurea
- DSPD
disalicylidene propanediamine
- DTNB
5,5-dithiobis-(2-nitrobenzoic acid) 相似文献
34.
The cyanobacterium Oscillatoria agardhii was grown in continuous culture under various light conditions in order to study the interactions of light on phosphorus-limited growth. Under severe P-limiting (light-saturating) conditions, a low chlorophyll a and C-phycocyanin content was found. In addition, the light-harvesting capacity, reflected in the values of P
max (maximum light-saturated oxygen production rate) and (photosynthetic affinity), were low compared to light-limited cultures.Reduction of the light climate, either by reduction of the length of the photoperiod or light-intensity, resulted in an increase in light-harvesting capacity (higher pigment content, P
m and ) during growth under P-limiting conditions. Light-induced changes in P
max and could be related to the relative growth rate, being the actual growth rate as a fraction of the growth rate which would be observed under light-limiting conditions.Under P-limiting conditions, reduction of the light-climate caused a reduction in dry weight of the culture. This decrease was mainly due to a decrease in carbohydrate content of the cells. Under all conditions tested, carbohydrates were found to accumulate during the light-period and to be consumed during the dark-period.Evaluation of carbohydrate consumption in the dark yielded a specific maintenance rate constant of 0.001 h-1. This observation leads to the conclusion that the specific maintenance rate constant is independent on the character of the growth rate limiting nutrient for O. agardhii. 相似文献
35.
Proton translocation during the reduction of NO
3
-
, NO
2
-
, N2O and O2, with endogenous substrates, in washed cells of Rhodopseudomonas sphaeroides f. denitrificans was investigated by an oxidant pulse method. On adding NO
2
-
to washed cells, anaerobically in the dark, an alkalinization occurred in the reaction mixture followed by acidification. When NO
3
-
, N2O or O2 was added to cells in the dark or with these compounds and NO
2
-
in light an acidification only was observed. Proton translocation was inhibited by carbonyl cyanide-m-chlorophenyl hydrazone.Valinomycin treated cells produced acid in response to the addition of either NO
3
-
, NO
2
-
, N2O or O2. The proton extrusion stoichiometry (
ratios) in illuminated cells were as follows: NO
3
-
0.5N2, 4.82; NO
2
-
0.5N2, 5.43; N2ON2, 6.20; and O2H2O, 6.43. In the dark the comparable values were 3.99, 4.10, 4.17 and 3.95. Thus, illuminated cells produced higher
values than those in the dark, indicating a close link between photosynthesis and denitrification in the generation of proton gradients across the bacterial cell membranes.When reduced benzyl viologen was the electron donor in the presence of 1 mM N-ethylmaleimide and 0.5 mM 2-n-heptyl-4-hydroxyquinoline-N-oxide in the dark, the addition of either NO
3
-
, NO
2
-
or N2O to washed cells resulted in a rapid alkalinization of the reaction mixture. The stoichiometries for proton consumption,
ratios without a permeant ion were NO
3
-
NO
2
-
,-1.95; NO
2
-
0.5 N2O,-3.03 and N2ON2,-2.02. The data indicate that these reductions occur on the periplasmic side of the cytoplasmic membrane.Abbreviations BVH
reduced benzyl viologen
- CCCP
carbonyl cyanide m-chlorophenyl hydrazone
- DIECA
N, N-diethyl-dithiocarbamate
- HOQNO
2-n-heptyl-4-hydroxyquinoline-N-oxide
- NEM
N-ethylmaleimide 相似文献
36.
The regulation of carbonic anhydrase by environmental conditions was determined forChlamydomonas reinhardtii. The depression of carbonic anhydrase in air-grown cells was pH-dependent. Growth of cells on air at acid pH, corresponding to 10 m CO2 in solution, resulted in complete repression of carbonic-anhydrase activity. At pH 6.9, increasing the CO2 concentration to 0.15% (v/v) in the gas phase, corresponding to 11 M in solution, was sufficient to completely repress carbonic-anhydrase activity. Photosynthesis and intracellular inorganic carbon were measured in air-grown and high-CO2-grown cells using a silicone-oil centrifugation technique. With carbonic anhydrase repressed cells limited inorganic-carbon accumulation resulted from non-specific binding of CO2. With air-grown cells, inorganic-carbon uptake at acid pH, i.e. 5.5, was linear up to 0.5 mM external inorganic-carbon concentration whereas at alkaline pH, i.e. 7.5, the accumulation ratio decreased with increase in external inorganic-carbon concentration. It is suggested that in air-grown cells at acid pH, CO2 is the inorganic carbon species that crosses the plasmalemma. The conversion of CO2 to HCO
3
-
by carbonic anhydrase in the cytosol results in inorganic-carbon accumulation and maintains the diffusion gradient for carbon dioxide across the cell boundary. However, this mechanism will not account for energy-dependent accumulation of inorganic carbon when there is little difference in pH between the exterior and cytosol. 相似文献
37.
Chromatophores isolated from the marine phototrophic bacterium Rhodobacter sulfidophilus were found to photoreduce NAD with sulfide as the electron donor. The apparent K
m for sulfide was 370 M and the optimal pH was 7.0. The rate of NAD photoreduction in chromatophore suspensions with sulfide as the electron donor (about 7–12 M/h·mol Bchl) was approximately onetenth the rate of sulfide oxidation in whole cell suspensions. NAD photoreduction was inhibited by rotenone, carbonyl cyanide-m-chlorophenylhydrazone, and antimycin A. Sulfide reduced ubiquinone in the dark when added to anaerobic chromatophore suspensions. These results suggest that electron transport from sulfide to NAD involves an initial dark reduction of ubiquinone followed by reverse electron transport from ubiquinol to NAD mediated by NADH dehydrogenase.Abbreviations Bchl
bacteriochlorophyll
- CCCP
carbonyl cyanide-m-chlorophenylhydrazone
- MOPS
3(N-morpholino)-propane sulfonate
- Uq
ubiquinone 相似文献
38.
Anton F. Post 《Archives of microbiology》1986,145(4):353-357
Transitions in growth irradiance level from 92 to 7 Em-2 s-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O2 evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla
chlorophyll a
- CPC
C-phycocyanin
- PS II
photosystem II
- PS I
photosystem I
- RC II
reaction center of photosystem II
- P
photosynthetic O2-evolution
- I
irradiance, Em-2 s-1
-
light utilization efficiency of cells, mmol O2·mg dry wt-1·h-1/Em-2 s-1
-
light utilization efficiency of photosynthetic apparatus, mol O2·mol Chla
-1·h-1/Em-2 s-1
- Pmax
maximal rate of O2 evolution by cells, mol O2·mg dry wt-1·h-1
- Pmax
maximal rate of O2 evolution by photosynthetic apparatus, mol O2·mol·Chla
-1·h-1
- LL
low light, E m-2 s-1
- HL
high light, E m-2 s-1
- LH
low to high light transition
- HL
high to low light transition
-
k
specific rate of adaptation, h-1
-
specific growth rate, h-1
-
Q
pool size of cell constituent, mol·mg dry wt-1
-
q
net synthesis rate of cell constituent, mol·mg dry wt-1·h-1 相似文献
39.
The photosynthetic capacity of detached leaves of a non-yellowing mutant of Festuca pratensis Huds. declined during senescence at a similar rate to that in a normal cultivar. Respiratory oxygen uptake in the dark continued at similar rates in both genotypes during several days of senescence. In chloroplasts isolated from leaves at intervals after excision, the rate of photosystem I (PS I)-mediated methyl viologen reduction using reduced N,N,N,N-tetramethyl-p-phenylene diamine as electron donor also declined in both genotypes, possibly due to loss of integrity of the photosynthetic apparatus in the cytochrome f-plastocyanin region. There was a similar fall in PS II electron transport using water as electron donor and measured at the rate of reduction of 2,6-dichlorophenolindophenol. Partial restoration of this activity by the addition of diphenyl carbazide was evidence for lability of the oxygen-evolving complex during senescence. An accentuated difference between mutant and normal material in this case indicated that the mutant retains a greater number of functional PS II centres. Changes in the light-saturation characteristics of the two photosystems have been discussed in relation to the organization of the photosynthetic membranes during senescence.Abbreviations and symbols DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DCPIP
2,6-dichlorophenolindophenol
- DMSO
dimethyl sulphoxide
- DPC
diphenyl carbazide
- MV
methyl viologen
- PS I, PS II
photosystem I, II
- TMPD
N,N,N,N-tetramethyl-p-phenylene diamine 相似文献
40.
Photosynthetic characteristics of detached barley leaves during greening in the presence of SAN 9785
The effects of the pyridazinone compound SAN 9785 on the photosynthetic competence of leaves, on the photochemical activity of isolated thylakoids and on the formation and spectral properties of chlorophyll-protein complexes were studied during a 72-h greening period of detached etiolated leaves of barley (Hordeum vulgare L. cv. Horpácsi kétsoros). It was established that i) the photosynthetic capacity of the leaves decreased considerably (by 80 and 90%, as determined by14CO2 fixation and fast fluorescence induction measurements, respectively); ii) the photochemical activity of isolated thylakoids from water to potassium ferricyanide and from dichlorophenol indophenol/ascorbate to methylviologen exhibited only slight reductions when expressed on a chlorophyll basis compared with the control; iii) the slow fluorescence induction curves of the treated leaves demonstrated the presence of a peculiar fluorescence component interrupting the quenching of fluorescence at around 1 min illumination; iv) a shortage of the chlorophyll-protein complex of photosystem I (CPI) occurred with a higher content of the monomer of the light harvesting complex in the thylakoids of treated leaves; and v) the fluorescence spectrum of the CPI band present in treated leaves indicates the destruction of the structural integrity of this complex during isolation from the membrane.Abbreviations Chl
chlorophyll
- CPI, CPII
chlorophyll-protein complexes of the reaction centres of PSI and PSII
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DPIP
2,6-dichlorophenol indophenol
- DPIPH2
chemically reduced form of DPIP
-
F
o
fluorescence of constant yield
-
F
v
fluorescence of variable yield
-
F
i
,F
m
mitial and maximum yield of fluorescence
- LHCP3
monomer of the light-harvesting complex
- LHCP2 and LHCP1
oligomers of the light-harvesting complex LHCP3
- PSI, PSII
photosystems I, II
- SAN 9785
4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone, also known as BASF 13-338
- SDS-PAGE
sodium dodecyl sulphate-polyacrylamide gel electrophoresis 相似文献