We can prove it by an experiment:
. Take two petridishes and mark them as A and B.
.Spread cotton wool in both the petridishes.
.Moisten the cotton wool in petridish A with water.
.Place equal number of gram seeds in both the petridishes.
.Keep both the petridishes in a room temperature (25 degrees to 30 degrees).
.observe after two days.
You will observe that seeds in petridish A germinate whereas seeds in petridish B do not germinate.
This shows that water is essensial for germination.
Now, we can say that a plant requires wet soil to germinate.A seed requires adequate amount of water to germinate. In wet soil, adequate absorbtion of water is done.The moisture in the wet soil softens the seed coay and the testa.Seed swells up and embryo breaks through the softned seed-coat and comes out easily.Therefore, it requires wet soil to germinate.
hope it helps.. :)))