A vegetative cell is a cell of plant or animal body except reproductive cells; i.e. a cell which does not participate in production of gametes.
Mature pollen grain contains two cells:
Vegetative cell
Generative cell
Both these cells remain together & independently until cellular differentiation takes place, where the generative cell produces 2 male gametes and vegetative cell produces a pollen tube.
The pollen tube is required to carry the sperm towards the egg.
As a result of different purposes of both generative and vegetative cells, each cell develops its own distinct activity during maturation, like a generative cell doubles its genetic content and vegetative cell undergoes certain changes in its cytoplasmic content.