Fig. 6.

Relationship between translocated fractions of ATP and NADPH within their total balance in the plastid under light conditions. Fractions of ATP or NADPH that are exchanged between plastid and cytosol through ATP/ADP translocator (T.ATP) and malate/oxaloacetate shuttle (T.NADPH) depend on the FQR/FNR ratio (the ratio between cyclic [FQR] and non-cyclic [FNR] electron flow through photosynthesis light reactions). Cyclic electron flow through photosynthesis light reactions increases ATP yield without corresponding increase in NADPH formation. This estimate was done under assumption of fixed flux ratio photorespiration / photosynthesis = 0.25. Positive values of T.ATP/ATP indicate import of ATP to the plastid from cytosol, zero value indicate self-sufficient ATP balance in the plastid, while the negative values points on ATP export to cytosol. Negative values of T.NADPH/NADPH indicate export reduced equivalents from plastid via malate/oxaloacetate shuttle, while zero values indicate self-sufficient NADPH balance in the plastid. The shaded area, an ATP/NADPH ratio of 1.3 - 1.5 indicates the ratio required to ensure CO₂-fixation in the Calvin-Benson-Cycle [63, 73]