When do plants care about CO2 fluctuations?

[scottward]

Do plants care about CO2 fluctuations provided, at the lowest point in the fluctuation, the CO2 level is still above ~ 30mg/l (i.e. Rubisco is saturated at 30mg/l)?

e.g.
If, at a particular point in the water, the CO2 level is varying between 20mg/l and 40mg/l, I believe the plant WILL care (growth very poor, possible autofragmentation etc).
However, if the fluctuation was between 30mg/l and 50mg/l, the plant WON'T care (since Rubisco fully saturates at 30mg/l anyway)?

Am I understanding this correctly?

Scott.

[Tug]

That's how I understand it. Of course this means you might just have it wrong. :eek:
Do you have the link? I would like to look at that thread again.

[Tom Barr]

For common aggressive fast growing thin leaved weeds, the range is 20-35ppm of CO2.
For other species? It is going to be higher. they will still grow nicely, but to fully saturate, some might go quite high.

We have 300 species +, maybe 5 have been tested for CO2 and light like this.

Then only a few common weeds.
As far as max levels, this is the same as Liebig's law, but applies to CO2(and light as well)

Regards,
Tom Barr

[scottward]

For common aggressive fast growing thin leaved weeds, the range is 20-35ppm of CO2.

So Tom this is generally the 'indicator' plant group, i.e. fast growing stem plants that show up CO2 issues the fastest and therefore make a good 'indicator' to general CO2 levels?

If the tank was filled just with these plants in the 20-35ppm range, would the answer to my question then be yes - i.e. provided the lowest point of any fluctuation was greater than 35ppm the plant wouldn't care about any fluctuation? Whereas at levels lower than 35ppm the plant would?