Increased concentrations will increase CO_2 fixation in Calvin cycle, provided light intensity is not limiting, and causes more GP and TP synthesis
If CO_2 concentrations go below 0.01%, RuBP will accumulate, decreasing GP and TP levels (fewer are synthesised); CO_2 levels in leaf air spaces could decrease to this if plant suffers from water stress (closes stomata, reducing CO_2 uptake)
