The effect of O2 and CO 2 concentration on photosynthesis and glycolate accumulation in bean leaves treated with α-hydroxy-2-pyridinemethanesulfonic acid (α-HPMS), the glycolate oxidase inhibitor.

(14)CO2 assimilation, (14)C incorporation into glycolate and glycolate accumulation in α-HPMS† treated bean leaves at various O2 and CO2 concentrations were studied. In 1% CO2 oxygen concentration had no significant effect on glycolate accumulation and (14)C incorporation into glycolate. In the CO2 concentration range of 0.03% to 0.01%, increased oxygen concentration decreased not only (14)CO2 assimilation but also glycolate accumulation and (14)C incorporation into glycolate. In 1% and 0.1% CO2, no matter what O2 concentration was supplied, and in 0.03% CO2 with 2% and 21% O2, all of the glycolate accumulated was formed from newly assimilated carbon. In 0.01% CO2 and 2%, 21% and 100% O2, and in 0.03% CO2 with 100% O2, a substantial portion of the glycolic acid that accumulated in leaves originated from endogenous unlabelled substrates. These findings are discussed in terms of possible changes in the ratio of RuBP carboxylation to RuBP oxygenation and of changes of RuBP pool size, induced by changing O2 and CO2 concentrations.