Figure 1.

Simple representation of the reactions that can be involved in gross O₂ production and uptake of a photosynthesizing cell, showing how labeled ¹⁸O water results in the production of ¹⁸O₂ in the approach developed by Gauthier et al. (2018). In the case of reactions within the peroxisome and mitochondria, this only represents net O₂ consumption, i.e. there is both uptake and release occurring. PSII, Photosystem II; PSI, Photosystem I; Fd, Ferredoxin; M, Mehler reaction; PCR; photosynthetic carbon reduction; PCO, photosynthetic carbon oxidation; PGA, 3-phosphoglycerate; P-Glyc, phosphoglycolate; Glyox, glyoxylate; OAA, oxaloacetate; Mal, malate.