Cell division
is to multiply, but when you're going to perform a function--like
contracting for cells, or destroying foreign agents for
macrophages--then you're not dividing. Interphase describe all the time
spent not actively dividing.
Interphase
is when the cell grows and carries on its normal functions. Many, many
cells stay in interphase all the time and never divide.
Also, the phases of mitosis don't take very long at all, so they won't
make up much of the cell cycle even in cells of a root tip.
