Special abscission zone is formed

Cells resume division perpendicular to petiole axis

Vascular tissues remain functional

In preparation for leaf fall, a special abscission zone is formed at the base of petioles. It typically starts with cell divisions that take place perpendicular to the axis of the petiole. The growth of the abscission layer does not extend through the vascular tissues.

Shown here is a longitudinal section through the base of the petiole of Coleus blumei showing products of cell division i.e. tabular cells (TC) in the early development of the abscission zone.