> From: jshane at moose_uvm.edu (John Shane)
> Subject: Plants, CO2/O2 etc.
> Hello Folks...

Hello John

> I've been reading this list for quite awhile, but have never posted; thanks
> to everyone for the very sound advice/opinions. Over the last several days
> there have been a few posts relating to ........ CO2.


> Sorry for the long-winded post, but the idea that "photosynthesis occurs in
> light, and respiration occurs in the dark" is a concept I battle constantly
> with students, and, surprisingly, with a number of otherwise well-informed
> individuals.
>     John Shane                                        (802) 656-2907
> University of Vermont                       jshane at moose_uvm.edu
>  Forestry Department                        FAX --   (802)656-8683

Thanks for the post. 

On this subject, there is something I've been wondering about for some time. 
I have a distant memory from school biology of a concept known as "The
Compensation Point". This (if I remember correctly) is a state that terrestial
plants strive to achieve where the O2 + sugars produced by photosynthesis
are entirely used up in respiration and the water + CO2 produced by respiration
are entirely used up in photosynthesis. The plant is in an optimum state of
equillibrium and is evolved to reach this point for its given growing

For example, a plant growing on a forest floor would reach its compensation
point at the normally low light intensity expected in this position but would
do less well in open country with higher light intensity because it would only
be able to maintain its "compenstaion point" at either end of the daylight 
period when the light intensity was lower.

Does this apply to aquatic plants? If so is it the state we should be striving
to achieve for our plants? Is there anyone who could expand on this subject
more authoritatively than me? It seems to be a neglected issue.

Mick Nally