Rise Time of the Light Induced Electrical Field across the Function Membrane of Photosynthesis

Abstract

A repetitive laser giant pulse photometer is described which can resolve absorption changes of 0.1% in the time range of 10 ns. With this instrument the following results have been obtained.The rise of the field indicating absorption change in photosynthesis has been measured at 515 nm. The upper limit of the half risetime is about 20 ns. This means that the field formation takes place within this time by a light induced transfer of electrons across the thylakoid membrane.

On the coupling of electrical events at the membranes of energized chloroplasts in intact plant leaf cells

“…The fact that after the first flash the potential decays in the dark towards the dark potential with the system 2 site remaining reduced, might be indicative for the neutralization of the ionic charge at this site (-. OH-) due to the field-driven ion fluxes across the thylakoid membrane as discussed by Witt [5,6] Summarizing, the results justify the conclusion that the phase 1 potential change at the chloroplast membrane is quantitatively associated with an ion binding process at the thylakoid membrane surface and due to induced charge polarization at the enclosing membrane. On basis of our interpretation we have to conclude that this binding process occurs with a rate constant k = 2.7 • 10 a sec -1 .…”

“…The results can be described in terms of the reaction kinetics of an ion binding process (probably of protons) at the thylakoid membrane. This binding has been suggested to occur at the negative binding sites at the outer surface of the thylakoid membrane, formed in the primary photochemical acts upon flash excitation within 20 nsec [6]. It has been discussed that the binding results in a reduction of catalysts occupied by the sites (i.e.…”

Proton translocation in the slow rise of the flash‐induced 515 nm absorbance change of intact chloroplasts

“…This change in absorbance, related to the energized state of the thylakoids, starts with a fast (-IX) rise and relaxes with a slow (-100 ms) decay [2,3]. Recently, in intact isolated chloroplasts a biphasic rise, has been established [4-91.…”

Electrical evidence for the field indicating absorption change in bioenergetic membranes

“…The generation of an electrical field across the membrane of bioenergetic systems as in green plants and bacteria has beerL demonstrated since 1967 by the shift of absorption bands of membrane pigments in the field (electrochromism) [1][2][3][4][5][6][7][8]. Such shifts cause absorption changes of all the bulk pigments incorporated in the membrane (chlorophyll-a, -b and carotenoids) [4,7,8].…”

“…Such shifts cause absorption changes of all the bulk pigments incorporated in the membrane (chlorophyll-a, -b and carotenoids) [4,7,8]. The rise of these so-called 'field indicating absorption changes' takes place in < 20 nsec [5]. It is caused by a light-induced transfer of electrons perpendicular to the bioenergetic membrane.…”