Which one is not a unit of vegetative propagation?

Seed

The correct answer is Option (4) → Seed

Vegetative propagules are parts of a plant that can give rise to a new plant without sexual reproduction. In angiosperms, several structures can serve as vegetative propagules. In plants, the units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb are all capable of giving rise to new offspring. These structures are called vegetative propagules. Obviously, since the formation of these structures does not involve two parents, the process involved is asexual.

Flowers are the reproductive structures of flowering plants involved in sexual reproduction, where male gametes fertilize female gametes to produce seeds. After dispersal, seeds germinate under favourable conditions to produce new plants.