The basal plate is the compact, fleshy stem found in bulbs. It is the location where the new organs form on the bulb.
Meristems that form on the basal plate include those for vegetative and flowering stem, new buds that will form offsets, and the root system that arises as adventitious roots.
Each of the bulb scales used to store food reserves while the bulb is dormant also arise from the basal plate.
The basal plate is anatomically a stem although it has been so modified that it does not immediately resemble a stem.
However, it performs all of the functions of the stem found in most other plants.
It is the source of new vegetative and flowering buds.
The basal plate is visible through the paper covering on a tulip bulb.
With the papery cover removed, you can see that there are several bulblets developing from one side of the basal plate.
Many species of Iris develop from rhizomes, but some use bulbs as their over wintering structure.
The iris to the right has a very textured outer tunica layer and very nicely illustrates that the basal plate is the location where the new vegetative and flower stem arises.
Note how the flower showing blue petals is already formed before the shoot emerges from the bulb.
Here is a section of an iris bulb nicely showing a new vegetative and floral meristem arising from the basal plate (arrow).