scholarly journals The photochemical activities and electron carriers of developing barley leaves

1973 ◽  
Vol 136 (3) ◽  
pp. 803-812 ◽  
Author(s):  
Marijana Plesničar ◽  
Derek S. Bendall
Keyword(s):  
Cytochrome B ◽  
Photosystem 2 ◽  
Cytochrome F ◽  
Reaction Centre ◽  
Photosystem 1 ◽  
Photochemical Activities ◽  
Cyclic Photophosphorylation ◽  
Photosystem 2 Activity ◽  
Barley Leaves ◽  
Electron Carriers

The development of photochemical activities in isolated barley plastids during illumination of dark-grown plants has been studied and compared with the behaviour of plastocyanin, cytochromes f, b-559LP, b-563 and b-559HP and pigments P546 (C550) and P700. Electron-transport activity dependent on Photosystem 1 and cyclic photophosphorylation dependent on N-methylphenazonium methosulphate (phenazine methosulphate) were very active relative to the chlorophyll content after only a few minutes of illumination of etiolated leaves, and then rapidly declined during the first few hours of greening. By contrast, Photosystem 2 activity (measured with ferricyanide as electron acceptor) and non-cyclic photophosphorylation were not detectable during the first 2½h of greening, but then increased in total amount in parallel with chlorophyll. The behaviour of the electron carriers suggested their association with either Photosystem 1 or 2 respectively. In the first group were plastocyanin, cytochrome f and cytochrome b-563, whose concentrations in the leaf did not change during greening, and cytochrome b-559LP whose concentration fell to one-half its original value, and in the second group were cytochrome b-559HP and pigment P546, the concentrations of which closely followed the activities of Photosystem 2. Pigment P700 could not be detected during the first hour, during which time some other form of chlorophyll may take its place in the reaction centre of Photosystem 1. The plastids started to develop grana at about the time that Photosystem 2 activity became detectable.

Coloured Components of Chloroplast Membranes as Intrinsic Membrane Probes for Monitoring the Development of Heat Injury in Intact Tissues

1979 ◽  
Vol 6 (1) ◽  
pp. 121 ◽  
Author(s):  
RM Smillie
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem 2 ◽  
Leaf Tissue ◽  
Proton Pumping ◽  
Cytochrome F ◽  
Heat Sensitivity ◽  
Heat Injury ◽  
Chloroplast Membrane ◽  
Photosystem 2 Activity ◽  
Membrane Probes

Assays for heat injury in intact leaves were investigated by heating leaf tissue at a rate of 1°C per minute and recording changes in chlorophyll fluorescence; chlorophyll absorbance; light-induced absorbance change at 518 nm of the bulk chloroplast pigments (chlorophylls and carotenoids); and photooxidation of chloroplast cytochrome-554 (cytochrome f ). Leaves of the golden passionfruit (Passiflora edulis forma flavicarpa were used as the experimental material. Heat injury to the chloroplast thylakoid membranes began above 35°C as evidenced by abnormal changes in chlorophyll fluorescence and absorbance and inactivation of chloroplast membrane activities. Chlorophyll fluorescence increased and chlorophyll absorbance decreased above 35°C and the increase and decrease, respectively, were greatest at 52°C. The measurements made on intact leaf tissue together with assays of photosystem 2 activity in isolated chloroplasts indicated the relative thermostabilities of several chloroplast membrane activities. Inactivation of photosystem 2 activity linked to oxygen evolution appeared to be associated with membrane changes occurring between 35 and 44°C. The 518-nm absorbance changes indicated that energy-dependent proton pumping and associated reactions were inactivated between 44 and 48°C. Photosystem-1-mediated photooxidation of cytochrome-554 became inactivated between 48 and 52°C. These studies demonstrate that chlorophylls, carotenoids and cytochrome f may be used as intrinsic membrane probes for monitoring the development of heat injury in the chloroplast membrane system. The absorbance and fluorescence changes that these compounds undergo upon heating provide a basis for reliable and rapid methods applicable to intact tissue for determining heat sensitivity in green plants.

scholarly journals A requirement for EDTA in the separation of Photosystems 1 and 2 from the cyanobacterium Chlorogloea fritschii

1981 ◽  
Vol 196 (2) ◽  
pp. 489-493 ◽  
Author(s):  
E H Evans ◽  
C A Pullin
Keyword(s):  
Photosystem 2 ◽  
Photosystems 1 And 2 ◽  
Photosystem 1 ◽  
Molecular Weights ◽  
Kd Values ◽  
Photosystem 2 Activity ◽  
Triton X ◽  
Photosystem 1 And 2

Fractions enriched in Photosystem 1 or Photosystem 2 activity have been isolated from the cyanobacterium Chlorogloea fritschii after extraction of the membranes with digitonin and Triton X-100. Separation of the extract into the two components was achieved by using a Sepharose 6B column, calibration of which gave Kd values of 0.3 for the Photosystem 1 fraction and 0.53 for Photosystem 2. These values corresponded to molecular weights of approx. 500000 and 90000 respectively. The Photosystem 1 particle was shown to aggregate on storage and EDTA was shown to be necessary to separate the Photosystem 1 and 2 fractions.

Changes in photosystem 2 activity associated with plant tolerance to lead

1981 ◽  
Vol 21 (3) ◽  
pp. 269-274 ◽  
Author(s):  
J.R. Homer ◽  
R. Cotton ◽  
E.H. Evans
Keyword(s):  
Photosystem 2 ◽  
Plant Tolerance ◽  
Photosystem 2 Activity

scholarly journals Multiple light-induced reactions of cytochromes b and c in Rhodopseudomonas spheroides

1969 ◽  
Vol 114 (4) ◽  
pp. 793-799 ◽  
Author(s):  
O. T. G. Jones
Keyword(s):  
Cytochrome C ◽  
Cytochrome B ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Close Association ◽  
Antimycin A ◽  
Reaction Centre ◽  
Difference Spectra ◽  
Cytochromes C ◽  
Rhodopseudomonas Spheroides

Illumination of chromatophore preparations from Rhodopseudomonas spheroides causes the oxidation of a cytochrome c and a slight oxidation of a cytochrome b with a maximum at 560nm. When illuminated in the presence of antimycin A the oxidation of cytochrome c was more pronounced and cytochrome b560 was reduced; the dark oxidation of cytochrome b560 was biphasic in the presence of succinate, but not in the presence of NADH, a less effective reductant. Split-beam spectroscopy showed that, in addition to the reduction of cytochrome b560, another pigment with maxima at 565 and 537nm. was reduced and was more rapidly oxidized in the dark than cytochrome b560. This pigment, tentatively identified as cytochrome b565, was also detected in spectra at 77°k, after brief illumination at room temperature; the maxima at 77°k were at 562 and 536nm. In the absence of antimycin A, light caused a transient reduction of cytochrome b565 and an oxidation of cytochrome b560. Dark oxidation of b565 was rapid, even in the presence of antimycin A and succinate. Difference spectra, at 77°k, of ascorbate-reduced minus succinate-reduced chromatophores or of anaerobic succinate-reduced minus aerobic succinate-reduced chromatophores suggested that two cytochromes c were present, with maxima at 547 and 549nm. When chromatophores frozen at 77°k were illuminated both these cytochromes c were oxidized, indicating a close association with the photochemical reaction centre. A scheme involving two reaction centres is proposed to explain these results.

Localization and Function of Cytochrome f in the Thylakoid Membrane

1977 ◽  
Vol 32 (3-4) ◽  
pp. 271-280 ◽  
Author(s):  
Georg H. Schmid ◽  
Alfons Radunz ◽  
Wilhelm Menke
Keyword(s):  
Electron Transport ◽  
Outer Surface ◽  
Thylakoid Membrane ◽  
Time Lag ◽  
Photosynthetic Electron Transport ◽  
Cytochrome F ◽  
Antigenic Determinants ◽  
Light Reaction ◽  
Transport Reaction ◽  
Cyclic Photophosphorylation

Abstract A monospecific antiserum to cytochrome f agglutinates stroma-free swellable chloroplasts from tobacco and Antirrhinum. Consequently, antigenic determinants towards which the antiserum is directed are located in the outer surface of the thylakoid membrane. The antiserum inhibits linear photosynthetic electron transport. Just as described earlier for the antiserum to polypeptide 11000 this inhibition develops in the course of the light reaction. Ultrasonication in the presence of anti­ serum abolishes the light requirement and the maximal inhibition of the electron transport reaction is immediately observed. Electron transport in chloroplasts from a tobacco mutant which ex­ hibits only photosystem I-reactions is also inhibited by the antiserum. No time lag in the light for the onset of inhibition is observed with these chloroplasts. As chloroplasts of this mutant have only single unfolded thylakoids it appears that light might preponderantly open up partitions. If the light effect is interpreted in this way, cytochrome f should be located in the partition regions but nevertheless in the outer surface of the thylakoid membrane. However, a rearrangement of molecules in the membrane in the light by which the accessibility of cytochrome f is changed can­ not be excluded. The inhibition of linear electron transport by the antiserum is approximately 50 per cent and can only be increased to 75% upon the addition of antibodies to plastocyanin. The inhibition by the antiserum to cytochrome f as well as the combined inhibition by the antisera to cytochrome f and plastocyanin can be by-passed by DCPiP. It appears that cytochrome f and plastocyanin cannot be connected in series in the electron transport chain but are both closely associated in the thylakoid membrane. PMS-mediated cyclic photophosphorylation in chloroplasts from wild type tobacco and the tobacco mutant NC95 is only inhibited if the chloroplasts are sonicated in the presence of anti­ serum. If one disregards, that ultrasonication might cause reaction artifacts, it is thinkable that the cytochrome f, involved in the PMS-mediated cyclic photophosphorylation reaction, might be located inside the membrane.

scholarly journals Diaminobenzidine an Electron Donor to Photosystem 1 and to Photosystem 2 in Chloroplasts

1975 ◽  
Vol 52 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Gozal BEN-HAYYIM ◽  
Ziwia DRECHSLER ◽  
Judith GOFFER ◽  
Joseph NEUMANN
Keyword(s):  
Electron Donor ◽  
Photosystem 2 ◽  
Photosystem 1
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