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Titolo:
Photoactivation of electrogenic activity in chloroplasts and its relation to photoinduced swelling of thylakoids
Autore:
Bulychev, AA; Vredenberg, WJ;
Indirizzi:
Moscow State Univ, Fac Biol, Dept Biophys, Moscow 119899, Russia Moscow State Univ Moscow Russia 119899 pt Biophys, Moscow 119899, Russia Univ Wageningen & Res Ctr, Dept Plant Physiol, NL-6703 BD Wageningen, Netherlands Univ Wageningen & Res Ctr Wageningen Netherlands NL-6703 BD Netherlands
Titolo Testata:
RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
fascicolo: 6, volume: 47, anno: 2000,
pagine: 754 - 760
SICI:
1021-4437(200011/12)47:6<754:POEAIC>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
PATCH-CLAMP; ELECTRIC-FIELD; MEMBRANE; PHOTOSYNTHESIS; TRANSPORT; CURRENTS;
Keywords:
Peperomia metallica; chloroplasts; thylakoid membranes; electric potential; photocurrent; structural changes;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: Bulychev, AA Moscow State Univ, Fac Biol, Dept Biophys, Moscow 119899, Russia Moscow State Univ Moscow Russia 119899 oscow 119899, Russia
Citazione:
A.A. Bulychev e W.J. Vredenberg, "Photoactivation of electrogenic activity in chloroplasts and its relation to photoinduced swelling of thylakoids", RUSS J PL P, 47(6), 2000, pp. 754-760

Abstract

In patch-clamp experiments on isolated chloroplasts of Peperomia metallicaLind, ct Rodig, (Piperaceae), the replacement of 50 mM KCL in a medium with 50 mM NH4Cl strongly influenced the parameters of photocurrent known to reflect the generation of electric potential in thylakoids. The addition of NH4+ to the medium modified the induction curves of the photocurrent as well as the currents induced by single-turnover flashes in preilluminated chloroplasts. Under the action of a prolonged light pulse (similar to1 s), the steady-state current was much higher in the ammonium-containing medium thanin the presence of Kf. Preillumination of a dark-adapted chloroplast with a 1-s light pulse suppressed the current induced by a single-turnover flash(6 Cls) in the presence of K+ but caused an elevation (by 50-150%) of the flash-induced current and shortening of its relaxation time in the presenceof NH4+ The origin of different induction kinetics for the photocurrent inK+ and NH4+ media is partly clear, because ammonium prevents generation ofthe pH gradient and, subsequently, eliminates the Delta pH-dependent suppression of the electron transport rate. However, this does not explain the origin of NH4+-dependent photostimulation of the current generated by single-turnover flashes, This phenomenon arises from the thylakoid swelling caused by the accumulation of NH4+ in the lumen and from the respective changes in the network resistances. The network element most sensitive to thylakoidswelling is the lateral resistance of the lumen: it decreases upon enlargement of the cross-section area. Stimulation of the flash-induced current bypreillumination in the presence of NH4+ was accompanied by accelerated relaxation of the current, indicating that the phenomena observed are caused by the reduction of network resistance involved in the discharge of the membrane capacity. Thus, the light-induced structural changes in the thylakoid system have a marked effect on the currents measured with the patch-clamp technique.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 10/07/20 alle ore 00:22:21