Light-induced rapid absorption changes during photosynthesis: IV. Reactions in aged chloroplasts in the presence of ascorbate and redox dyes
✍ Scribed by Bacon Ke
- Publisher
- Elsevier Science
- Year
- 1964
- Weight
- 441 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0926-6577
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✦ Synopsis
Transient absorption changes at 43 ° m/z are induced in aged chloroplasts by red light flashes. The absorption change occurs in lO -4 sec or less and has a half life of approx. lO -2 sec. The enhancement of the reaction by ascorbate and the abolishment by ferricyanide suggest that an oxidation reaction is responsible for the absorption change.
In the presence of 3-(3,4-dichlorophenyl)-I,I-dimethylurea the absorption change is not observed, but the signal can be restored completely by adding ascorbate.
Available evidence from the decay kinetics of the 43o-m/z transient absorption changes in the presence of ascorbate suggests that dichlorophenolindophenol at all concentrations reacts with cytochrome while phenazine methosulfate at low concentrations reacts with cytochrome and at concentrations greater than 3"1o-5 M with P7oo only. This is in accord with the difference spectra observed in the blue region (where also cytochrome changes are observed) and also with the concomitant and similarly decaying absorption changes at 430 and 703 m/~.
Light-intensity dependency of the complex reaction in aged chloroplasts containing ascorbate and trace amount of phenazine methosulfate showed that at low intensity only the oxidation of the chlorophyll complex takes place. The coupling reaction between the pigment complex and cytoehrolne takes place only at higher light intensities.