The kinematics and mechanics of leaf expansion: new pieces to the Arabidopsis puzzle

• Kinematic studies revealed how the growth behaviors of cell clusters can influence leaf shape.
• Time-lapse imaging reveals new properties of pavement cell lobe initiation.
• Finite element modeling detects feedback between cell shape, cell wall stress, and microtubules.
• KATANIN-mediated microtubule severing maintains a lobed growth pattern.

Leaves are the primary organs for photosynthesis, and their angle, size, and timing of deployment determine the light capture efficiency of the canopy. Therefore, leaf development is an important trait in both natural and managed populations. In dicot leaves, the spatial and temporal patterns of cell division and expansion are heterogeneous, and a long-standing challenge has been to understand how subcellular and cellular growth processes can operate across broad spatial scales to influence the macroscopic growth of leaves. This review focuses on recent time-lapse analyses that help to clarify relationships between the polarized growth of individual cells, the growth behaviors of cell clusters, and leaf morphology.