Effects of Indoleacetic Acid on CO2 Fixation, Electron Transport and Phosphorylation in Isolated Chloroplasts

1978 ◽  
Vol 5 (4) ◽  
pp. 425 ◽  
Author(s):  
SP Robinson ◽  
JT Wiskich ◽  
LG Paleg
Keyword(s):  
Electron Transport ◽  
Methyl Viologen ◽  
Co2 Fixation ◽  
Indoleacetic Acid ◽  
Direct Interaction ◽  
Co2 Uptake ◽  
Phenazine Methosulfate ◽  
Short Term ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

The effects of indoleactic acid (IAA) on CO2 fixation, electron transport and photophosphorylation were examined. The rate of CO2 fixation by preparations of intact chloroplasts was not significantly increased by the addition of IAA (0.2 - 5 �M). Electron transport and coupled phosphorylations were similarly unaffected when measured with ferricyanide or methyl viologen as the electron acceptor. Cyclic phosphorylntion mediated by phenazine methosulfate was also not increased by IAA. It is concluded that the hormone does not affect photosynthesis by isolated chloroplasts in short-term experiments and that the increased CO2 uptake observed with leaves following application of IAA may result from some effect of the hormone other than a direct interaction with the chloroplasts.

scholarly journals Effects of Cadmium on Carbonic Anhydrase and Activities Dependent on Electron Transport of Isolated Chloroplasts.

1969 ◽  
Vol 63 (2) ◽  
pp. 195-201 ◽  
Author(s):  
Carmen I. Asencio ◽  
Arturo Cedeño-Maldonado
Keyword(s):  
Electron Transport ◽  
Carbonic Anhydrase ◽  
Co2 Fixation ◽  
Strong Inhibition ◽  
Enzyme Preparations ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

Low concentrations of Cadmium inhibit the electron transport and CO2 fixation reactions of isolated chloroplasts. CO2 fixation is more sensitive to Cd than electron transport and dark pre-incubation increases the degree of toxicity to both. Carbonic anhydrase, an enzyme associated with CO2 fixation, is very sensitive to Cd either when applied directly to partially purified preparations of the enzyme or when enzyme preparations are obtained from intact chloroplasts previously exposed to Cd. Strong inhibition occurs at Cd concentrations lower than those required to inhibit any of the electron transport dependent reactions studied. These results are interpreted as evidence that carbonic anhydrase is one of the most sensitive sites of Cd action in isolated chloroplasts.

Effect of the Plastoquinone Antagonist Dibromothymoquinone on Electron Transport Reactions in Chloroplast Preparations

1977 ◽  
Vol 4 (2) ◽  
pp. 253 ◽  
Author(s):  
A Stewart ◽  
AWD Larkum
Keyword(s):  
Electron Transport ◽  
Thylakoid Membrane ◽  
Methyl Viologen ◽  
Control Level ◽  
Type A ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Photosynthetic Control ◽  
Type C

The effects of dibromothymoquinone (DBMIB) on electron transport in types A, B, C and D spinach and pea chloroplast preparations have been studied. DBMIB (1 x 10-6M) strongly inhibited electron transport to methyl viologen in all the types of chloroplasts, while electron transport to ferricyanide was inhibited by 60%. Envelope-free (type C) chloroplast preparations with poor photosynthetic control were inhibited more strongly than intact (types A and B) chloroplast preparations at low (< 5 x 10-7M) concentrations of DBMIB. Type C preparations with good photosynthetic control were less strongly inhibited except in the presence of uncoupler or in the absence of ADP. Above 1 x 10-6M DBMIB, inhibition of electron transport to ferricyanide became progressively less and, with type A chloroplast preparations, a large stimulation compared to the control level occurred. Phenylenediamine stimulated high rates of electron transport to ferricyanide in the presence of low concentrations of DBMIB. At higher DBMIB concentrations, the stimulation was completely reversed and envelope-free chloroplasts again showed greater sensitivity to DBMIB compared to intact chloroplasts. DBMIB appears to have a number of sites of interaction with the thylakoid membrane.

Inorganic Phosphate Concentration in the Stroma of Isolated Chloroplasts and Its Influence on Photosynthesis

1987 ◽  
Vol 14 (4) ◽  
pp. 451 ◽  
Author(s):  
SP Robinson ◽  
C Giersch
Keyword(s):  
High Performance ◽  
Co2 Fixation ◽  
Colorimetric Method ◽  
Reaction Medium ◽  
Thylakoid Membranes ◽  
Rapid Decrease ◽  
Phosphate Concentration ◽  
Intact Chloroplasts ◽  
Metabolic Pool ◽  
Isolated Chloroplasts

The concentration of inorganic orthophosphate (Pi) was determined in the stroma of isolated chloroplasts during photosynthesis under Pi-saturated and Pi-limited conditions. Pi was determined calorimetrically or by high performance liquid chromatography of extracts of chloroplasts labelled with 32Pi. When chloroplasts were illuminated in the absence of added Pi, photosynthesis soon declined due to Pi-depletion. After 5 min in the light, photosynthesis had declined to 2% of the maximum rate. At this point, stromal Pi was estimated to be 1.4 mM by the colorimetric method and 0.2 mM by 32P chromatography. Using the colorimetric method, Pi equivalent to approximately 1 mM in the stroma was found to be associated with thylakoid membranes isolated from chloroplasts, irrespective of the Pi content of the intact chloroplasts. This was considered to be a non-metabolic pool of Pi. During steady- state photosynthesis with optimal concentrations of Pi added to the reaction medium, the stromal Pi concentration was estimated to be 2.6 mM and 1.6 mM with the colorimetric and 32P methods, respectively. Measurement of stromal 32Pi in chloroplasts illuminated with varying concentrations of 32Pi in the reaction medium suggested that photosynthesis was saturated at stromal Pi concentrations above 2.0-2.5 mM. Photophosphorylation by thylakoid membranes was saturated at Pi concentrations above 1.2-1.5 mM. It is concluded that, during photosynthesis in isolated chloroplasts in the presence of an optimal supply of Pi from the reaction medium, the stromal Pi concentration is just above that required to saturate photophosphorylation. Any decrease in the supply of Pi from the medium results in a rapid decrease in stromal Pi to the point where photophosphorylation may become Pi-limited, decreasing the rate of CO2 fixation.

Molecular biology of enzyme adaptations in higher eukaryotes

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 272-283 ◽  
Author(s):  
Donal A. Hickey ◽  
Bernhard F. Benkel ◽  
Charalambos Magoulas
Keyword(s):  
Molecular Biology ◽  
Tissue Specificity ◽  
Enzyme System ◽  
Direct Interaction ◽  
Evolutionary Genetics ◽  
Short Term ◽  
Eukaryotic Genes ◽  
Higher Eukaryotes ◽  
The Relationship

Multicellular eukaryotes have evolved complex homeostatic mechanisms that buffer the majority of their cells from direct interaction with the external environment. Thus, in these organisms long-term adaptations are generally achieved by modulating the developmental profile and tissue specificity of gene expression. Nevertheless, a subset of eukaryotic genes are still involved in direct responses to environmental fluctuations. It is the adaptative responses in the expression of these genes that buffers many other genes from direct environmental effects. Both microevolutionary and macroevolutionary patterns of change in the structure and regulation of such genes are illustrated by the sequences encoding α-amylases. The molecular biology and evolution of α-amylases in Drosophila and other higher eukaryotes are presented. The amylase system illustrates the effects of both long-term and short-term natural selection, acting on both the structural and regulatory components of a gene–enzyme system. This system offers an opportunity for linking evolutionary genetics to molecular biology, and it allows us to explore the relationship between short-term microevolutionary changes and long-term adaptations.Key words: gene regulation, molecular evolution, eukaryotes, Drosophila, amylase.

Inhibition of Photosynthetic Reactions by Aureomycin

1984 ◽  
Vol 39 (6) ◽  
pp. 627-633 ◽  
Author(s):  
Ji-yu Ye ◽  
U. Heber
Keyword(s):  
Membrane Potential ◽  
Proton Gradient ◽  
Effective Inhibitor ◽  
Mesophyll Protoplasts ◽  
Electrochromic Shift ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Photosynthetic Reactions ◽  
Isolated Chloroplasts

The effect of aureomycin on photosynthesis was investigated. This antibiotic which has been reported to stimulate photosynthesis at very low concentrations is an effective inhibitor at higher concentrations. In mesophyll protoplasts and isolated chloroplasts from spinach, 50% inhibition of CO2 reduction required about 20 μᴍ aureomycin. The reduction of 3-phosphoglycerate and of oxaloacetate by intact chloroplasts was also inhibited, but not that of nitrite and methylviologen which was actually stimulated. NADP reduction by broken chloroplasts and methylviologen- dependent photophosphorylation were also sensitive to aureomycin. The electrochromic shift at 518 nm which indicates formation of a light-dependent membrane potential was suppressed in the presence of 200 μᴍ aureomycin and the transthylakoid proton gradient was decreased. The data confirm reports that aureomycin has uncoupling properties, and they indicate that it also acts as an inhibitor of ferredoxin/NADP reductase.

scholarly journals Biological CO2 Uptake and Upwelling Regulate the Air-Sea CO2 Flux in the Changjiang Plume Under South Winds in Summer

2021 ◽  
Vol 8 ◽  
Author(s):  
Dewang Li ◽  
Xiaobo Ni ◽  
Kui Wang ◽  
Dingyong Zeng ◽  
Bin Wang ◽  
...  
Keyword(s):  
Surface Waters ◽  
Carbon Sink ◽  
Co2 Flux ◽  
Co2 Uptake ◽  
Short Term ◽  
Biological Production ◽  
Initial Stage ◽  
Wind Event ◽  
Wind Events ◽  
Biogeochemical Parameters

The partial pressure of CO2 (pCO2) in the sea and the air-sea CO2 flux in plume waters are subject to interactions among biological production, horizontal advection, and upwelling under wind events. In this study, time series of pCO2 and other biogeochemical parameters in the dynamic Changjiang plume were presented to illuminate the controlling factors of pCO2 and the air-sea CO2 flux after a strong south wind event (July 23–24, maximum of 11.2 ms–1). The surface pCO2 decreased by 310 μatm (to 184 μatm) from July 24 to 26. Low-pCO2 waters (&lt;200 μatm) were observed in the following 2 days. Corresponding chlorophyll a and dissolved oxygen (DO) increase, and a significant relationship between DO and npCO2 indicated that biological uptake drove the pCO2 decrease. The salinity of undersaturated-CO2 waters decreased by 3.57 (from 25.03 to 21.46) within 2 days (July 27–28), suggesting the offshore advection of plume waters in which CO2 had been biologically reduced. Four days after the wind event, the upwelling of high-CO2 waters was observed, which increased the pCO2 by 428 μatm (up to 584 μatm) within 6 days. Eight days after the onset of upwelling, the surface pCO2 started to decrease (from 661 to 346 μatm within 3 days), which was probably associated with biological production. Regarding the air-sea CO2 flux, the carbon sink of the plume was enhanced as the low-pCO2 plume waters were pushed offshore under the south winds. In its initial stage, the subsequent upwelling made the surface waters act as a carbon source to the atmosphere. However, the surface waters became a carbon sink again after a week of upwelling. Such short-term air-sea carbon fluxes driven by wind have likely occurred in other dynamic coastal waters and have probably induced significant uncertainties in flux estimations.

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