Surfing the Hyperbola Equations of the Steady-State Farquhar–von Caemmerer–Berry C(3) Leaf Photosynthesis Model: What Can a Theoretical Analysis of Their Oblique Asymptotes and Transition Points Tell Us?

The asymptotes and transition points of the net CO(2) assimilation (A/C(i)) rate curves of the steady-state Farquhar–von Caemmerer–Berry (FvCB) model for leaf photosynthesis of C(3) plants are examined in a theoretical study, which begins from the exploration of the standard equations of hyperbolae after rotating the coordinate system. The analysis of the A/C(i) quadratic equations of the three limitation states of the FvCB model—abbreviated as A(c), A(j) and A(p)—allows us to conclude that their oblique asymptotes have a common slope that depends only on the mesophyll conductance to CO(2) diffusion (g(m)). The limiting values for the transition points between any two states of the three limitation states c, j and p do not depend on g(m), and the results are therefore valid for rectangular and non-rectangular hyperbola equations of the FvCB model. The analysis of the variation of the slopes of the asymptotes with g(m) casts doubts about the fulfilment of the steady-state conditions, particularly, when the net CO(2) assimilation rate is inhibited at high CO(2) concentrations. The application of the theoretical analysis to extended steady-state FvCB models, where the hyperbola equations of A(c), A(j) and A(p) are modified to accommodate nitrogen assimilation and amino acids export via the photorespiratory pathway, is also discussed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11538-019-00676-z) contains supplementary material, which is available to authorized users.