Relationship between chlorophyll a fluorescence induction and oxygen evolution in barley (Hordeum vulgare) thylakoids treated with alpha-, beta-, and gamma-cyclodextrins

2002 ◽  
Vol 80 (7) ◽  
pp. 741-751 ◽  
Author(s):  
G Sridharan ◽  
E Daneau ◽  
M Fragata
Keyword(s):  
Photosystem Ii ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Chlorophyll A Fluorescence ◽  
Fluorescence Induction ◽  
Nonlinear Phenomenon ◽  
Maximal Level ◽  
Alpha Beta ◽  
Gamma Cyclodextrin ◽  
Oligomeric Compounds

Cyclodextrins, a class of cyclic oligomeric compounds consisting of 6–8 units of D-glucose, alter the oxygen evolution of photosystem II (PSII) in barley thylakoids as well as chlorophyll a fluorescence induction, i.e., Fv/Fo and Fv/Fm where Fm is the maximal level of fluorescence when all PSII centres are closed, Fo is the minimal level of chlorophyll fluorescence when all PSII centres are open, and Fv is the variable fluorescence (= Fm – Fo). The highest Fv/Fm and Fv/Fo values are observed in samples treated with alpha- and beta-cyclodextrins, i.e., 0.618 and 0.629 (Fv/Fm) and 1.617 and 1.667 (Fv/Fo), respectively, whereas in untreated and gamma-cyclodextrin-treated thylakoids, one observes 0.608 and 0.594 (Fv/Fm) and 1.568 and 1.460 (Fv/Fo). This trend is also seen in the oxygen evolution of control and alpha-, beta-, and gamma-cyclodextrin-treated thylakoids, i.e., 183.6, 214.9, 301.7, and 174.0 µmol O2·mg chlorophyll–1·h–1, respectively. First, the fluorescence induction data indicate that in intact thylakoid membranes, the enhancement of oxygen evolution induced by alpha- and beta-cyclodextrins originates in the opening of blocked photochemical centres in PSII. Second, the results show that the correlation between the oxygen evolution of PSII and chlorophyll a fluorescence induction is a nonlinear phenomenon represented by a Boltzman expression.Key words: chlorophyll, cyclodextrins, fluorescence induction, oxygen evolution, photosystem II, thylakoid membrane.

scholarly journals Rate-limiting steps in the dark-to-light transition of Photosystem II - revealed by chlorophyll-a fluorescence induction

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Melinda Magyar ◽  
Gábor Sipka ◽  
László Kovács ◽  
Bettina Ughy ◽  
Qingjun Zhu ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Fluorescence Induction ◽  
Rate Limiting

Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings I. Chlorophyll a Fluorescence Transients and Photosystem II Activity

1982 ◽  
Vol 37 (3-4) ◽  
pp. 268-275 ◽  
Author(s):  
K. H. Grumbach
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Chlorophyll A Fluorescence ◽  
Photosynthetic Electron Transport ◽  
Photosystem Ii Activity ◽  
Chlorophyll A Fluorescence Transients ◽  
Radish Seedlings ◽  
Fluorescence Transients

Abstract Diuron and bentazon are very strong inhibitors of the photosynthetic electron transport in isolated radish chloroplasts. The chlorosis producing herbicide SAN 6706 also inhibited the photosystem II dependent oxygen evolution. Aminotriazole had no effect. The inhibitor concentration for 50% inhibition of photosystem II activity was 10-7 m for diuron and 10-4 m for bentazon and SAN 6706 respectively.Diuron and bentazon quenched the chlorophyll a fluorescence transients in isolated radish chloroplasts drastically, while aminotriazole was not effective. It was of particular interest that the bleaching herbicide SAN 6706 inhibited photosystem II dependent oxygen evolution in a similar concentration as bentazon but had no effect on the chlorophyll a-fluorescence transients suggesting that SAN 6706 is not binding to the same site of the electron transport chain as diuron and bentazon.Apart from their direct influence on electron transport in isolated photosynthetically active chloroplasts the photosystem II and bleaching herbicides assayed also strongly affected photosynthesis in radish seedlings that were grown in the presence of the herbicides for a long time. As already obtained using isolated chloroplasts, photosystem II dependent oxygen evolution like the chlorophyll a fluorescence transients were strongly inhibited by the photosystem II herbicides diuron and bentazon. A reduction but no inhibition of photosystem II activity was observed in plants that were grown in the presence of aminotriazole. The pyridazinone SAN 6706 was behaving contradictory. In partly green plants photosystem II activity was still maintained and even higher than in untreated plants while in albinistic plants no photosynthetic activity was detected.

On the determination of QB-non-reducing photosystem II centers from chlorophyll a fluorescence induction

Plant Science ◽  
2003 ◽  
Vol 164 (4) ◽  
pp. 665-670 ◽  
Author(s):  
Pavel Tomek ◽  
Petr Ilı́k ◽  
Dušan Lazár ◽  
Michal Štroch ◽  
Jan Nauš
Keyword(s):  
Photosystem Ii ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Fluorescence Induction

Characterization of the Inhibition of Photosynthetic Electron Transport in Pea Chloroplasts by the Herbicide 4,6-Dinitro-o-cresol by Comparative Studies with 3-(3,4-Dichlorophenyl)-1,1- dimethylurea

1978 ◽  
Vol 33 (5-6) ◽  
pp. 413-420 ◽  
Author(s):  
J. J. S. van Rensen ◽  
D. Wong ◽  
Govindjee
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Chlorophyll A Fluorescence ◽  
Chlorophyll Concentration ◽  
Fluorescence Emission ◽  
Photosynthetic Electron Transport ◽  
Percent Inhibition ◽  
Mechanism Of Inhibition

An attempt to characterize the mechanism of inhibition of photosynthetic electron transport in isolated pea chloroplasts by the herbicide 4,6-dinitro-o-cresol (DNOC) by a comparison with the effects of 3-(3,4-dichlorophenyl)-1.1-dimethylurea (DCMU) revealed the following: 1.The percent inhibition of oxygen evolution by a given herbicide concentration is the same at various light intensities except at very low intensities where the percent inhibition becomes larger. The same results are obtained with the herbicide DCMU. 2.The concentration of DCMU causing 50% inhibition of oxygen evolution decreases with de­creasing chloroplast (and thus of chlorophyll) concentration. With DNOC, the relative decrease is much less than with DCMU. At the inhibited molecule, there appears to be a cooperative binding of DCMU with two binding sites and a noncooperative binding of DNOC with only one binding site. 3.The chlorophyll a fluorescence induction is influenced by DNOC in the same characteristic way as it is by DCMU: both herbicides cause a faster rise in fluorescence yield than in control chloroplasts, although a higher concentration of the former is required for the same effect. 4.The chlorophyll fluorescence emission spectra at 77 CK show a slight decrease in the bands at 685 and 735 nm, and no or only a very slight decrease at 695 nm upon addition of high con­centrations of either DCMU or DNOC before the onset of illumination. 5.The degree of polarization of chlorophyll a fluorescence is lower after addition of DCMU or DNOC upon excitation by 460 or 660 nm light. It is concluded that, although the chemical structure of DNOC is completely different from that of DCMU, its site and mechanism of inhibition is similar to that of DCMU. Both herbicides inhibit electron transport between the primary electron acceptor of photosystem II and the plastoquinone pool. This causes a closing of the reaction centers of photosystem II. However, the interaction with the inhibited molecule is different for the two herbicides.

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