Term:

Abaxial
Definition:

The lower part of a structure such as a leaf, i.e., that part of a structure that faces away the main axis to which it is attached. For example, if a leaf is pushed upward and against a stem the surface facing away from the stem is the abaxial surface.
Notes:

In neotropical Lecythidaceae this term refers to the position of the staminal ring elongation in zygomorphic-flowered species which always develops on the abaxial side of the staminal ring and also commonly used to describe the differs in color between the adaxial and abaxial surfaces of leaves. In nearly all species the abaxial surface of a leaf of Lecythidaceae is lighter in color than the adaxial surface.