Leaf growth in dicots and monocots: so different yet so alike.

In plants, most organs grow post-embryonically through cell division and cell expansion. The coordination of these two growth processes is generally considered to be different between dicots and monocots. In dicot plants, such as the model plant Arabidopsis, leaf growth is most often described as being temporally regulated with cell division ceasing earlier at the tip and continuing longer at the base of the leaf. Conversely, in monocot leaves, the organization of the growth processes is rather viewed as spatially regulated with dividing cells at the base of the leaf, followed by expanding cells and finally mature cells at the tip. As our understanding of the leaf growth processes in the two major classes of flowering plants expands, it becomes increasingly clear that the regulation of the growth processes is to a great extent conserved between dicots and monocots. In this review, we highlight how the temporal and spatial organization of cell division and cell expansion takes place in both dicot and monocot leaves. We also show that there are similarities in the molecular wiring that coordinates these two processes during leaf development.