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  CO2 Injection Replies
From: Ted.Held at hstna.com on 2005.01.03 at 13:57:48(12535)
Thank you to the responders. I also thought of different ways to supply the CO2. I passed on the dry ice idea because I did not really want to exclude oxygen. I think the usual idea is that an increase in the CO2 from, let us say, 0.4% to 0.8% in an airspace will be beneficial. Who knows what total immersion might do? There is the threat that the plant would be asphyxiated at night when it needs oxygen. They might risk asphyxiation even during daylight hours. Does anyone know what would happen?

The basic conjecture, as I see it, for CO2 injection is that plants are limited in the growth potential from a deficiency of CO2 as a nutrient. Even the most ardent fans would probably admit that when any supposed CO2 deficiency is sated, additional gas would be wasted.

Based on this, I was hoping to see a growth spurt as the theorized CO2 starvation was alleviated. Once I observed that none had occurred, especially with small signs of decline, I ended the experiment. I imagine that the unwanted byproducts of candle burning are at least contenders with possible detrimental effects of too much CO2 as reasons for the evident slight decline in plant vigor. The important thing for me was that new growth was not observed, which I would have expected if CO2 deficiency was an important consideration. Another possibility is that the benefits of CO2 were exactly countered by detrimental effects of byproducts or that the byproduct effects were slightly greater than the benefits of CO2. That the two effects are exactly or nearly the same seems very unlikely to me. And since I think that the byproduct effect is likely minor, I discounted the second interpretation. I am open to contrary arguments, however.

In the experiments that I have seen written up, CO2 is increased slightly via compressed CO2 gas cylinders into the air space within closed experimental chambers. In field experiments, an enclosure cube is made with polyethylene sheet on a frame. Gas is then fed in, in a measured and precise way, for a length of time and the effects on plants noted in comparison with similar setups without the CO2. The amounts added were intended to see what would happen if CO2 levels in the real atmosphere were to increase in some realistic way, not to see what would happen in the unlikely event of an all-CO2 atmosphere. The report I saw was done in an open field with multiple plant species within the enclosures. There, it was discovered that certain species responded favorably, while others were indifferent or actually harmed by elevated CO2 concentrations.

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