The non-limiting level of co2 is what I'm not sure about. What would be the effect of keeping co2 levels at 5 ppm if it was always replenished as fast as it was used?
ppm means parts per million, and is a way to express concentration. another way, more often used in chemistry is moles per liter, or molarity. a reactions speed depends in part, on its concentration. the higher the rate the faster the reaction occurs, photosynthesis included. so if you dont change the photoperiod, the higher the [CO2], the more photosynthesis occurs in a given day.