I'm afraid this discussion has not really addressed any substantive issues. To
get benefit from adding CO2, you would have to be measuring the concentration
in the growing area at the critical time of day (or night) and be able to show
that either it dropped to a level which was rate limiting for photosynthesis or
that increased levels produced some measurable improvement in some useful
physiological process.
The Dutch researchers, always searching for a competive edge, have looked at
CO2 addition and found no benefits and indeed never were greenhouse levels low
enough to limit photosynthesis. Published? Probably not but widely circulated
in grower newsletters.
We used to believe that adding CO2 to the air conditioned houses used to
initiate Phalaenopsis flowers in Florida was useful. Some scientists even
explained that the higher CO2 levels were reducing respiration in the heat of
the afternoon and thereby assisting growth indirectly by this reduction. I was
sceptical and we ceased use of CO2, saving many thousands of dollars over a
summer-fall period and there was absolutely no change in the speed of
initiation or the number of spikes initiated per plant.
Andy Easton
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