Specifically, the partial pressure of carbon dioxide. https://en.wikipedia.org/wiki/Artificial_photosynthesis#Some_advantages,_disadvantages,_and_efficiency ht

Specifically, the partial pressure of carbon dioxide. https://en.wikipedia.org/wiki/Artificial_photosynthesis#Some_advantages,_disadvantages,_and_efficiency https://en.wikipedia.org/wiki/Artificial_photosynthesis#Some... "the efficiency of photosynthesis ... is usually below 1%, ... However, plants are efficient in using CO2 at atmospheric concentrations," This engineered tree would have to pump CO2 into itself.