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Originally Posted by Xist
I read a comment that 6% CO2 is lethal. Since that would be 60,000 PPM, 133 times current atmospheric levels, hopefully people do not experience that naturally.
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The concentration for death is less interesting to me than knowing the effects that doubling the concentration over the past 100 years has had.
Our respiration is controlled not by lack of oxygen, but instead concentration of CO2. If the air we breathe in already has a higher concentration of CO2 than what we are designed for, then it slightly alters our respiration impulse. What other things might be affected by a doubling of CO2 concentration?
Concerning the study you quoted, the full conclusion is that photosynthesis varies both positively or negatively depending on the pressure the plant is exposed to.
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The rate of respiration decreased linearly with increasing total pressure up to 0.2 MPa, and increased with increasing total pressure from 0.3 to 0.5 MPa at a low humidity. The rate of net photosynthesis decreased linearly with increasing total pressure under a constant partial pressure of CO2 at 40 Pa. On the other hand, the rate of net photosynthesis was clearly increased by up to 1.6-fold with increasing total pressure and partial pressure of CO2.
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