Nitrogen
Fixation
Nitrogen
Fixation -
Nitrogen
is
abundant
in
the
atmosphere,
sea
and
rocks.
It
constitutes
four
fifths
of
the
earth's
atmosphere.
It
is
not,
however,
always
present
in
forms
that
can
be
used
by
plants
and
animals.
The
relative
inertness
of
the
nitrogen
molecule
does
not
make
it
a
suitable
source
of
nitrogen
for
most
organisms.
Green
plants
assimilate
nitrogen
mainly
in
the
form
of
nitrate.
This
then
contributes
nitrogen
to
proteins,
nucleic
acids
and
other
biological
compounds.
These
compounds
in
turn
serve
as
a
source
of
nitrogen
for
the
entire
animal
kingdom.
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