Fig 1. MPM size classes and transitions.

Schematic of the MPM’s cell size classes and its three class transitions: carbon fixation, division, and carbon loss. The boundaries of the m cell size classes (v_i for i = 1, 2, …, m + 1) are logarithmically spaced, so that cells can transition to a size class that is exactly half their original size when they divide. For this purpose, the integer j is selected so that $v_{i-(j-1)}=\frac{1}{2}{v}_i$ for i ≥ j; cells in the first j−1 size classes cannot divide.