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light and electron flow

Lazar Dusan lazard at prfnw.upol.cz
Wed Oct 17 11:47:58 EST 2001

>  Dear users,
>  I am looking for some references and literature about the rates of
>  electron flow through photosystem II when algae adapted to different
>  light intensities (low light[5 =B5E m-2 -1]; normal and high light [e.g.
>  200 =B5E m-2 s-1]). Perhaps anyone knows a reference with PI-curves
>  (light saturation curves) at these light quantities.
>  Thank you very much for your help.
>  =46rank Uxerland

Hi !
At the (low) light intensities you mentioned above, the rate limiting
event in electrom transfer steps through PSII should be delivery of
quantum of light and not the electron transfer itself.
For example, for very high light of 3400 micromol m-2 s-1, there
is 1 quantum of light delivered to PSII every about 180 microsec (see
Lazar and Pospisil 1999, Eur. Biophys. J.  28, 468-477). Thus for 5
(200) micromol m-2 s-1, 1 quantum of light should be delivered to
PSII every about 122 msec  (3 msec) that shoud also determine the
overall rate of electron transfer through PSII that should be 8.2
(333) s-1. However, these are only approximate results calculated for
PSII of higher plants. But you can calculate it yourself using the
approach described in the above mentioned article.
Yours sincerely,
Dusan Lazar

Dusan Lazar
Dept. of Exp. Physics, Faculty of Science, Palacky University,
tr. Svobody 26, 771 46 Olomouc, Czech Republic
e-mail: lazard at aix.upol.cz


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