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Light-Dependent Oxygen Uptake, Glycolate, and Ammonia Release in L-Methionine Sulfoximine-Treated Chlamydomonas

Gilles Peltier and Pierre Thibault
Plant Physiology
Vol. 77, No. 2 (Feb., 1985), pp. 281-284
Stable URL: http://www.jstor.org/stable/4269123
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Light-Dependent Oxygen Uptake, Glycolate, and Ammonia Release in L-Methionine Sulfoximine-Treated Chlamydomonas
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Abstract

Glycolate and ammonia excretion plus oxygen exchanges were measured in the light in L-methionine-DL-sulfoximine treated air-grown Chlamydomonas reinhardii. At saturating CO2 (between 600 and 700 microliters per liter CO2) neither glycolate nor ammonia were excreted, whereas at the CO2 compensation concentration (<10 microliters per liter CO2) treated algae excreted both glycolate and ammonia at rates of 37 and 59 nanomoles per minute per milligram chlorophyll, respectively. From the excretion values we calculate the amount of O2 consumed through the glycolate pathway. The calculated value was not significantly different from the component of O2 uptake sensitive to CO2 obtained from the difference between O2 uptake of the CO2 compensation point and at saturating CO2. This component was about 40% of stationary O2 uptake measured at the CO2 compensation point. From these data we conclude that glyoxylate decarboxylation in air-grown Chlamydomonas represents a minor pathway of metabolism even in conditions where amino donors are deficient and that processes other than glycolate pathway are responsible for the O2 uptake insensitive to CO2.

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