Do plants use nitrate?

Hi Everyone,

I've just had a discussion with my local store owner after reading a post
from George Booth saying how Echinodorus may like high-ish nitrates (10-20
ppm).  My store owner says plants don't use nitrates, they use ammonia -
is he correct?

I was thinking Geroge was right, particularly since my swordplants have
never done particularly well (look OK, just haven't grown nearly as big
as their parents).  Mine were in a 125 gal tank with UGF and nitrates
0-4 ppm.  I have now moved them to tanks without UGF & higher nitrates.
Their parents are in a 110 tank with laterite & UG heating (owned by the
store owner).

Also ... I was wondering if anubias might need nitrates also.  My anubias
did poorly when I reduced nitrates in their 25 gal tank, but this kind of
coincided with anaerobic substrate & they just disintegrated :-(.

Any comments would be appreciated.  Hopefully I'll be in the fishroom
tomorrow & maybe we can discuss this there.