In many ways, its vasculature is similar to that of tendrils and primary stems. However, two differences in vascular bundle arrangement were are noted-- the two vascular bundles depicted by the yellow arrows and the large vascular bundle directly underneath them. At the petiole-leaf lamina attachment site, these anomalous vascular bundles coincide with the adaxial (upper) leaf surface.

Primary vascular bundles in petioles are similar to those of primary stems.

A highly magnified image of a petiole primary vascular bundle shows the distinct cap of phloic fibers.