Fig. 5.

Comparison between modeled and measured responses of CO₂ assimilation rate, A, and carbon isotope discrimination, Δ, to variation in intercellular pCO₂, C _i, in the C₃-C₄ intermediate species F. floridana and F. brownii. Measured A (a) and Δ (b) as a function of C _i in F. floridana (empty triangles), compared with the modeled responses predicted by C₃-C₄ photosynthetic model assuming an active C₄ cycle (solid lines) or no C₄ cycle activity (dashed lines). Measured A (c) and Δ (d) as a function of C _i in F. brownii (white squares), compared with the modelled responses using the C₃-C₄ models assuming Rubisco activity in the mesophyll cells (solid lines) or a strict compartmentalization of Rubisco in the bundle sheath cells (dashed lines). Parameters used for model simulations are presented in Table 1.