Hello...

I need some information about:
The effect of excessive amounts of CO2(carbon dioxide) in plants and how/why plants release CO2 at night (supposedly.. that's what I heard). Please post.. at least 50 words long, or send me an email to gsvg5@hotmail.com

From the topic: "Debate! Dr. Gray....."

Dr. Gray mentions that "It is known that vegetation and crops tend to benefit from higher amounts of atmospheric CO2, particularly vegetation which is under temperature or moisture stress."

Well, fortunately, it seems as if we'll be living is such a world (temp. & moisture stress), so "vegetation" will thrive for us.

You might want to research this a bit (google), to get a more complete, balanced and true picture.

I seem to recall hearing that increased CO2 causes increases in vegetative growth, but limits somatic growth.
Somatic growth (fruits and seeds) is where we get much of our nutrients, so maybe the benefit isn't all that clear.
Increased CO2 promotes quantity, not quality.

At night, when plants are not producing glucose (via photosynthesis), they are growing and developing (burning that glucose).

To do this they use normal "animal" metabolic pathways (i.e. Krebs Cycle), respiring CO2.

At least I think that's right....
Some plants have unique metabolic pathways too (CAM, C-4 plants).

I'd think 100% CO2 would kill a plant within a day.
I think even 4-5% will kill a plant. I know there is some fairly low optimum, over which higher concentrations are detrimental.

THanks for your help.

Thankfully (after all those years trying to memorize the horrible thing) I think I am correct.

Krebs Cycle

The pyruvate molecules produced during glycolysis contain a lot of energy in the bonds between their molecules. In order to use that energy, the cell must convert it into the form of ATP. To do so, pyruvate molecules are processed through the Kreb Cycle, also known as the citric acid cycle.
http://library.thinkquest.org/C004535/aerobic_respiration.html
&

Citric acid cycle in E.coli and plants

The citric acid cycle is highly conserved in all organisms. There are metabolic differences, however, under different circumstances. ....Oxaloacetate itself is used up in this reaction and needs to be replenished from the combination of two acetate units produced in the complete oxidation of pyruvate. This is performed by the glyoxylate cycle in bacteria (and plants; in the organelles called glyoxysomes). In this cycle, isocitrate is split by isocitrate lyase into succinate and glyoxylate. The latter can be linked with acetyl-CoA to form malate and CoA in a reaction catalyzed by malate synthase. Acetyl-CoA is formed from ATP and acetate by a phosphoryl group transfer to form acetyl-phosphate and ADP.
http://www.whatislife.com/reader2/Metabolism/pathway/tca.html

Just a passing comment, since I know next to nothing about it, and certainly don't have a definitive answer to the original question.

When considering the optimum CO2 level for a plant, I would think it might be very important to consider other variables affecting enzyme activity and photosynthesis, such as levels of light, temperature, moisture, and minerals (particularly for the production of the CO2 fixing enzyme, phosphoenolpyruvate carboxylase).

I gather that when aquarists use rather intense lighting, such as the penetrating metal halide sort, they find that artificially increasing the water's CO2 content produces much more luxuriant plants.

This is an interesting page about plant physiology:

http://www.colorado.edu/eeb/courses/4140bowman/lectures/4140-06.html

You might find more answers here:

http://www.biology-online.org/biology-forum/about292.html

Hi redewenur, the two above URL's you found are wonderful.
I have learnt such a lot from them.
Makes me realise that for a Science Forum, I am 'waffling' too much.
Thanks. Mike Kremer

how & why does co2 kill plants?

does anyone know why & how Co2 kills plants? can anyone tell me??? please? long explanation and explain... Thanx so much!

CO2 is important in establishing the homeostatic mechanism whereby both plants and animals maintain their internal pH. If there is too much CO2, the CO2 absorbs into the cytosol and affects the internal pH, dropping it into the acidic end of the carbonate-bicarbonate buffer system, thus poisoning the enzymes which need a specific pH to function.

So too much CO2 will acidify the leaves and kill the plant.