Plant dependence on CO₂ levels

Question

I was wondering which kind of plants would survive longest without CO₂ : plants with fatty, thick leaves or plants with thinner, less fatty leaves? And can we conclude that the plant species that are more dependent on CO₂ levels, would benefit from the greenhouse effect?

Answer 1

Plants do not need CO₂ for survival. They need it just for photosynthesis; if you supply them with alternate carbon source such as glucose then they would survive (See here for non-CO₂ Carbon-source utilization). There are non-photosynthetic plants which are totally dependent on carbon sources other than CO₂; some are carnivorous like venus fly-trap.

I am not sure what you intend when you correlate leaf thickness to CO₂-dependence. Leaf morphology can affect photosynthesis rates but afaik there is no relationship between leaf morphology and CO₂-dependence.

can we conclude that the plant species that are more dependent on CO₂ levels, would benefit from the greenhouse effect

Greenhouse effect is not equivalent to increase in CO₂; increased CO₂ levels can cause greenhouse effect which is a physical phenomenon of entrapment of IR radiation.

CO₂ is fixed by an enzyme called Rubisco; like most enzyme catalyzed reactions this will reach a saturation limit i.e. addition of more CO₂ will not increase the rate of photosynthesis. However the rate of photosynthesis is limited at the Rubisco step because of low levels of CO₂ (See here) and it can be expected that most photosynthetic plants will be benefited by increase in CO₂. However, not all plants would be resistant to increased temperatures and moreover the rate of enzyme catalysis would also change with temperature. So it is not that easy to predict.