O2 depression

Karen Culver-Rymsza kculver at gsosun1.gso.uri.edu
Tue Nov 7 16:56:13 EST 1995


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 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.

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?

Thank you in advance,

Karen Culver-Rymsza
University of Rhode Island
Graduate School of Oceanography
Narragansett, RI 02882
kculver at gsosun1.gso.uri.edu





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