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Re: CO2 and low light

On Mon, 10 Apr 2000, Ivo Busko wrote:

Quoting Mike Grace:

> > Greetings,
> >
> > Quick question.  Is there any reason NOT to add CO2 to a low light (1.5
> > w/gal) tank?
> >
> > Mike

Ivo said:

> I believe it has to do with the compensation point. That is, the light
> level at which the amounts of CO2 consumed in photosynthesis and produced
> by respiration balance out. Below that point the plant will produce more CO2
> than consume, so there is no point in adding extra CO2. Of course, this
> compensation would be extremely variable from species to species, and perhaps
> would depend on other environmental conditions as well.

Way back in Dec. '98 I think it was, Ole Larson summarized some findings
by Ole Pederson at Tropica; someone (Adam Novitt?) brought the same
subject up recently in the context of things that Claus Christensen said
while he was speaking in this country.

It seems that the compensation point can be lowered by adding CO2.  There
is a process called photorespiration that reduces plants' light-use
efficiency.  Increasing the CO2 concentration in the water decreases the
amount of photorespiration and increases the amount of benefit that plants
can get from low light levels.

In short, plants that fail to grow or simply die under low light and low
CO2 may live and even grow under the same light with CO2 added.

So there is a reason to provide CO2 to plants under low light.  I guess
that falls under the heading of environmental conditions that effect the
compensation point.

Roger Miller