| Autor: |
van Voorthuysen, Tijmen, Bulychev, Alexander A., Dassen, Hans H. A., Snel, Jan F. H., Vredenberg, Wim J. |
| Předmět: |
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| Zdroj: |
Physiologia Plantarum; Sep96, Vol. 98 Issue 1, p156-164, 9p |
| Abstrakt: |
Pre-illumination of the thylakoid membrane of Peperomia metallica chloroplasts leads to a reversible suppression of the flash-induced electrical potential as measured either with the electrochromic bandshift (P515), microelectrode impalement or patch-clamp technique. The energization-dependent potential suppression was not observed in the presence of 1 µM nigericin suggesting the involvement of proton and/or cation gradients. Energization in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and N,N,N′,N′-tetramethylphenylenediamine (TMPD), i.e. cyclic electron flow around photosystem (PS) I, results in the accumulation of TMPD+ in the thylakoid lumen. The reversible suppression of the flash-induced membrane potential was not observed in these conditions indicating that it is not a general cation-induced increase of membrane capacitance. Cyclic electron flow around PSI in the presence of DCMU and phenazine methosulfate (PMS) results in the accumulation of PMS+ and H+ in the thylakoid lumen. The absence of reversible suppression of the flash-induced membrane potential for this condition shows that accumulation of protons does not lead to (1) a reversible increase of membrane capacitance and (2) a reversible suppression of PSI-dependent electrogenesis. Reversible inactivation of PSII by a low pH in the thylakoid lumen is therefore proposed to be the cause for the temporary suppression of the flash-induced electrical potential. The flash-induced PSII-dependent membrane potential, as measured after major oxidation of P700 in far-red background light, was indeed found to be suppressed at low assay pH (pH 5) in isolated spinach (Spinacia oleracea) chloroplasts. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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