The Labelling of Malic and Citric Acids of Pea Leaves and Cotyledons of Germinating Peas by 14CO2 in the Dark

Leaflets of green pea plants and cotyledons of germinating peaswere kept in the dark in air containing ¹⁴CO₂. The malate extractedwas labelled to 35–40 per cent in the C-1 position andthe citric acid was labelled to 70–75 per cent in theC-6 position. This showed that two carboxylations, at least,were involved in both tissues, i.e. probably of a three-carbonacid to form malate, and of -oxoglutarate to form isocitrate.