Jonathan B. Marder
MARDER at agri.huji.ac.il
Sun Dec 8 22:29:30 EST 1996
In article <5879ii$ec4 at net.bio.net>, Rod Savidge <savidge at unb.ca> wrote:
>Can somebody please clarify the following for me.
Rod Savidge asks how we know that oxygen evolved from leaves comes from PSII
rather than superoxide dismutase and catalase.
Since one can get good photosynthetic oxygen evolution from washed thylakoids
(i.e. SOD and catalase absent), this suggests that PSII is capable of
producing molecular oxygen from water at a high rate. There seems no reason
why this activity would not occur also in vivo.
Rod Savidge's question suggests the possibility of PSII producing
superoxide or hydrogen peroxide rather than oxygen. However, there is not much
evidence for high levels of either species. Furthermore, in vivo levels of SOD
and catalase are probably much too low to account for observed oxygen
Jonathan B. Marder , Department of Agricultural Botany
E-mail: MARDER at agri.huji.ac.il | The Hebrew University of Jerusalem
Phone: (08 or +9728) 9481918 | /\/ Faculty of Agriculture
Fax: (08 or +9728) 9467763 |/ \ P.O.Box 12, Rehovot 76100, ISRAEL
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