Setting the boundaries: Primary cell wall synthesis and expansion

Mature plant cells typically have two-layered walls: a first-formed, thin, outer, primary wall layer enclosing a later-formed, thick, inner secondary wall. The surface area of the primary wall limits the size of the cell and thus the maximum amount of biomass that can potentially be accumulated in the secondary wall. By controlling the shape and size of the cell, the primary wall therefore imposes the limits on the amount of inedible biofuel a plant cell can make.