The reason plants need CO2 is to produce longer chain carbon compounds also known as photosynthetic intermediates. Photosynthetic intermediates includes compounds such as ribulose 1,5-bisphosphate, and 2-carboxy-3-keto-D-arabinitol 1,5 bisphosphate. Although the names are complicated, the structures are quite simple (5 carbon chains). Flourish Excel™ does not contain these specific compounds per se, but one that is quite similar. By dosing with Flourish Excel™ you bypass the involvement of CO2 and introduce the already finished, structurally similar compounds. It is in its structural similarity that Flourish Excel™ is able to be utilized in the carbon chain building process of photosynthesis. Simple chemical or enzymatic steps can easily convert it to any one to any one of the above named compounds (or a variety of others).