Photosynthesis in detached rye leaves at normal and low oxygen concentration. I. Incorporation of 14CO2 into 2-oxo acids.

In the leaves of rye plants at the milk maturity stage of grains, the following eight 2-oxo acids were detected by catalytic hydrogenolysis of the respective dinitrophenylhydrazone derivatives: 2-oxoglutarate, pyruvate, oxaloacetate, glyoxylate, hydroxypyruvate, 2-oxoisovalerate, 2-oxo-6-aminocaproate and 2-oxo-5-guanidinovalerate. Lowering of O2 concentration decreased incorporation of 14CO2 not only into the intermediates of the glycolate pathway, i.e. glyoxylate and hydroxypyruvate but also into other 2-oxo acids. At the same time, the level of these 2-oxo acids was much higher than in the leaves photosynthesizing at normal O2 concentration. On transfer to the dark for 6 h, the level of most of 2-oxo acids was lowered and the differences in specific radioactivity persisted. It seems that, under normal conditions, formation of pyruvate, oxaloacetate, glyoxylate and hydroxypyruvate in the light is closely related to CO2 assimilation.