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Re: CO2 use at nightime?

Mark wrote:

>CO2 is used directly by plants; there is no chemical precursor or 
>storage product for CO2.

This is probably true in all aquatics but not all plants.  Many desert
plants employ a system in which CO2 is taken up by the plant at night and
temporarily fixed into a storage molecule (not ribulose).  Upon sunrise,
the plant shuts its pores up tightly, thereby preventing water loss in the
heat.  CO2 that has been stored up during the cool night is then released
from the storage molecule and dropped in the calvin cycle as
photosynthesis provides ATP and NADPH.  At night the plant opens up
for gas exchange once again.  I don't remeber the detailed biochemistry
but I think these plants are called CAM plants.

Water not being a major concern for aquatic plants <g> I don't think that
this comes into play in our systems, and so I apologise for straying into
the "Off Topic Zone".  Just wanted to set the biological record straight.