The P-model assumes optimality to model the weekly timescale acclimatization of Rubisco-limited and light-limited photosynthetic capacities Vcmax and Jmax. Faster (subdaily) variation in these capacities can be modeled by a modified-Arrhenius type function (Kattge & Knorr, 2007) and by adjusting temperature-dependent intrinsic quantum yield $\phi_0(T)$ and soil moisture stress $\beta(\theta)$.

Mengoli et al. (2022) implement a subdaily version of the P-model where optimal values for Vcmax25, Jmax25, and $\xi$ are computed at local noon and accumulated via an exponential moving average. For each day, the instantaneous photosynthetic capacity is then modeled using the current noontime-acclimated capacities. We will use this formulation to implement update_photosynthesis! and update_conductance! for the P-model.