Photosynthetic Common Intercept Measurements
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The photocompensation point Γ* ties the biochemistry of RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase), to C3 plant physiology (via the Calvin cycle) and is an essential component of models of leaf photosynthesis. The photocompensation point can be estimated from the intersection of several response curves measured under subsaturating illumination (bottom figure). This simulation demonstrates that a perfect intersection is not expected if there is a significant resistance to transfer through the chloroplast as compared to through the cell wall . An inconsistent intersection is also illustrated when the relationship between the slope and the intercept of the various response curves is examined (top figure). You can modify assumptions of , , Γ*, and rates of day respiration and compare the simulated data to user-entered values for the slope and intercept of measured response curves.
Contributed by: Berkley J. Walker, Dane C. Skabelund, Forian A. Busch, and Donald R. Ort (January 2016)
Open content licensed under CC BY-NC-SA
 B. J. Walker and D. R. Ort, "Improved Method for Measuring the Apparent Photocompensation Point Resolves the Impact of Multiple Internal Conductances to to Net Gas Exchange," Plant, Cell & Environment, 38(11), 2015 pp. 2462–2474. doi:10.1111/pce.12562.