RuBisCO is the rate-limiting factor for plants, yes. But there’s more CO2 in the air naturally than they can adjust upward to compensate for, even before we factor in human-generated sources. The RuBisCO reaction is not maximally-efficient, which is why attempts to increase the rate of enzymatic activity are at the forefront of genetic engineering research into carbon sequestration. Additionally, the two relevant parameters (carbon dioxide fixing and oxygen incorporation) may already have struck a maximally-efficient tradeoff balance in many species of plants; self-modifying to favor increased CO2 fixation is not a trivial step; the gains here can be translated to losses over there, elsewhere in the biosystem. The organism is not its parts.
Anyway, if tomorrow we come up with plants that have a higher efficiency rate of carbon dioxide fixing, and they start pulling more CO2 from the air per unit time, that won’t fundamentally change that the population of plants and the room for them to grow is the determining factor in how much photosynthesis gets conducted—the RuBisCO reaction occurs in plants and protists such as algae when we’re talking about the macroscale, and basically nothing else.
Posit an artificial photosynthetic cell that can pack greater efficiency than the best of plants into the same surface area, and things are different. But we don’t have any such thing as yet.
RuBisCO is the rate-limiting factor for plants, yes. But there’s more CO2 in the air naturally than they can adjust upward to compensate for, even before we factor in human-generated sources. The RuBisCO reaction is not maximally-efficient, which is why attempts to increase the rate of enzymatic activity are at the forefront of genetic engineering research into carbon sequestration. Additionally, the two relevant parameters (carbon dioxide fixing and oxygen incorporation) may already have struck a maximally-efficient tradeoff balance in many species of plants; self-modifying to favor increased CO2 fixation is not a trivial step; the gains here can be translated to losses over there, elsewhere in the biosystem. The organism is not its parts.
Anyway, if tomorrow we come up with plants that have a higher efficiency rate of carbon dioxide fixing, and they start pulling more CO2 from the air per unit time, that won’t fundamentally change that the population of plants and the room for them to grow is the determining factor in how much photosynthesis gets conducted—the RuBisCO reaction occurs in plants and protists such as algae when we’re talking about the macroscale, and basically nothing else.
Posit an artificial photosynthetic cell that can pack greater efficiency than the best of plants into the same surface area, and things are different. But we don’t have any such thing as yet.