Leaf shape diversity with an emphasis on leaf contour variation, developmental background, and adaptation.

Leaf shape varies markedly. Here I focus on the diversity in leaf contour, which can be considered marginal variation in curvature if we omit detailed marginal structures such as serrations. This curvature can be described by a combination of sigmoids: a curve for the apical half and a curve for the basal half connected with or without an interval. Marginal curvature is determined by the position of the leaf meristem, the acceleration and deceleration of cell proliferation in the leaf meristem, and the angle of directed cell proliferation. Several key factors contributing to this variation have been revealed to date, but the majority of the underlying genetic mechanisms are unclear. Here I provide an overview of current knowledge and propose future directions for the field.