The petiole is the part of the leaf attaching the blade to the stem.
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.
Petiole XS 40X
Primary vascular bundles in petioles are similar to those of primary stems.
Petiole 100X
A highly magnified image of a petiole primary vascular bundle shows the distinct cap of phloic fibers.
Petiole XS 400X