Effects of bulk pH and of monovalent and divalent cations on chlorophyll a fluorescence and electron transport in pea thylakoids
| Autor: | Daniel Wong, Merkelo H, Govindjee |
|---|---|
| Rok vydání: | 1980 |
| Předmět: |
Chlorophyll
chemistry.chemical_classification Chloroplasts Molar concentration Chemistry Sodium Biophysics Analytical chemistry DCMU Cell Biology Hydrogen-Ion Concentration Plants Biochemistry Fluorescence Electron transport chain Divalent Electron Transport chemistry.chemical_compound Spectrometry Fluorescence Cations Thylakoid Magnesium Photosynthesis Photosystem |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Bioenergetics. 592:546-558 |
| ISSN: | 0005-2728 |
| DOI: | 10.1016/0005-2728(80)90099-7 |
| Popis: | Millimolar concentrations of monovalent cations enhance and divalent cations impede the redistribution (spill-over) of electronic excitation energy from Photosystem (PS) II to PS I in cation-depleted (sucrose-washed) thylakoids; this concept is based on chlorophyll a fluorescence and electron transport measurements over a narrow pH range around 7. We have tested the above concept in pea thylakoids over the pH range 5 to 9 by parallel measurements of various chlorophyll a fluorescence parameters (spectra, transients, and lifetimes at 77 K and 293 K, and polarization at 293 K) and of the rates of partial reactions of PSI and II. Our results provide the following information. 1. (1) Mg 2+ enhancement of fluorescence is maximum between 680 and 690 nm and minimum between 710 and 720 nm. 2. (2) The optimum conditions for the observation of the Mg 2+ -induced enhancement of fluorescence are: wavelength of emission, 685 nm; concentration of Mg 2+ , 10 mM, and pH, ∼7.5. 3. (3) Mg 2+ decreases the efficiency of excitation redistribution from PS II to PS I over the pH range 6 to 9. 4. (4) The antagonistic effects between Na + and Mg 2+ hold simultaneously for both the fluorescence intensity and lifetime, at physiological temperatures, only within the pH range 6 to 8. 5. (5) Mg 2+ enhances the light-limited electron transport rate through PS II in the pH range 5.4 to 8.2 and decreases that through PS I at pH 7.1 and 8.2. The % increase in PS II is, however, about twice the % decrease in PS I. |
| Databáze: | OpenAIRE |
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