Question

the seed contain the future plant. why it is said so?

Answer 1

The seed will grow in future and form a new plant.

Answer 2

The seed will develop in future and shape another plant.

A seed, however not dynamic, is a little living thing.

It contains the incipient organism of things to come plant, which isn't changing or creating: it is lethargic.

The regular thought is that the seed "rests" until the point when it gets what it needs to wake up.