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O2 depression

Kai Griebenow griebeno at athena.mit.edu
Wed Nov 8 10:22:38 EST 1995


In article <Pine.2.4.9511061337.A5032 at gsosun1>, Karen Culver-Rymsza
<kculver at gsosun1.gso.uri.edu> writes:
|> Dear fellow Photosynthesis-ers
|> I have been running experiments using the Hansatech oxygen electrode on
|> variously treated marine algae.  I have observed a depression in oxygen
|> evolution at light levels near saturating.  The O2 evolution dips
|> showing consumption for up to 4 minutes, then returns to near maximum rates.

I think you should look for the name Nultsch in the literature, he has done
studies on such phenomena. We even did experiments at the Philipps University
Marburg on exactly that subject.

|> I have been unable to find any description of this phenomenon in the
|> literature.  It does not compare to initial "lights-on"-type activity
|> because the cells have been exposed to increasing light levels.

Nultsch and co-workers did a lot on pre-treatment of Algae with very high
intensity light leading to photoinhibition.

|> It is possible this represents some corrective action, as the culture is
|> neither O2 purged or CO2 enriched (as part of the experiemtnal design,
|> potential CO2 limitation/O2 competition is significant).  However, Mehler
|> activity/photorespiration of this magnitude seems unlikely (the O2
|> consumption rate is on the order of 50% max O2 evolution rate)
|> Has anyone similar observations, and if so, plausible explanations?

Plausible explanations are many out there. I am unfortunately too far away from
that area of photosynthesis to remember now everything correctly. I am sure
there is a whole lot about that subject out there, especially on marine algae
that are low-light adapted.

|> Thank you in advance,
|> Karen Culver-Rymsza
|> University of Rhode Island
|> Graduate School of Oceanography
|> Narragansett, RI 02882
|> kculver at gsosun1.gso.uri.edu


Dr. Kai Griebenow       griebeno at mit.edu


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