the world > plants > part of plant > (defined by) distribution, arrangement, or position > [adjective] > of surface position (3)
Botany. Of or belonging to the anterior or lower surface.
Designating the surface of an organ, esp. a leaf, which during development initially faces away from the main axis or stem (usually the underside…
Designating the surface of an organ, esp. a leaf, which during development initially faces towards the main axis or stem (usually uppermost or…