Mr Press wrote: > The "Liebig Principle" states that growth will always be limited by >whatever nutritional factors are in limited supply.
I do not disagreed with what you write. However, the CO2 issue is quite complex. There are three things going on. First, to get any CO2 in the first place, a plant must expose its wet tissue to the air. More CO2 means more exchange per unit time, of course, but there is a second factor. This is the amount of water lost in transpiration while this is going on/ Per unit of carbon fixed, less water is lost if CO2 concentrations are higher. The third issue is that of the light compensation point. This is a jargon term for the quantity of light that is required at a give air temperature for photosynthetic gains to exactly equal respiratory losses. It turns out that this is much lower in elevated CO2 concentrations, meaning that active growth occurs at lower light intensities. This is normally a Good Thing. There are other tweaks around nutrient loss from leaves that have open stomata, lowered photorespiratation rates under non-limiting CO2, but I will not rehearse these. In essence, plants eat CO2; its concentration is usually the growth limiting factor within a hydrated plant's normal range; ergo, getting more of it is desirable. _____________________________________ Oliver Sparrow Tel: UK (0)20 7736 9716 www.chforum.org www.treknepal.org www.datafreeze.com
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