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Archimedes Plutonium wrote:

Question Steve. When plants use nitrogen as fertilizer. Does the plant
use the nitrogen in gaseous form or is the nitrogen bound up in solid form
before it is used by the plant.

Plants use nitrogen in solution -- e.g., nitrates or ammonium ion
dissolved in the soil moisture.

Or is that a silly question. In respiration
the elements of Oxygen and Carbon Dioxide are in gaseous form. So,
my question is that in plant fertilizer of nitrogen, does that nitrogen when
used by the plant have a gaseous form. I would guess the answer is no
because then, most plants would just take the nitrogen out of the air.

Correct. Gaseous (elemental) nitrogen is fairly inert and plants are
unable to use it directly. It is something of a wonder that certain
bacteria are able to "fix" nitrogen (convert elemental nitrogen to
ionic forms usable by plants).

So, I would guess that the nitrogen has to be in solid form and I would
guess in a compound that is not present in the atmosphere. If that is true,
then it seems as though the commensalism relationship I am searching for
involves the idea that plants need animals because animals have the biochemical
pathways to turn nitrogen into a solid-compound for which plants alone and
the atmosphere cannot do.

IMO plants would survive just fine if there were no higher animals on
earth. As I mentioned before, bacteria and fungi do a fine job of
fixing nitrogen from the air and turning complex proteins (many of
which are of plant origin to begin with) back to a form usable by
plants. Similarly, animals are not needed to convert oxygen to carbon
dioxide. Fires do that quite nicely.

Steve Turner

Real address contains worldnet instead of spamnet