Final answer:
ATP is not a net product nor a reactant of photosynthesis; it is used within the photosynthetic process but does not appear in the overall equation of photosynthesis which has water and carbon dioxide as reactants producing glucose and oxygen as products.
Step-by-step explanation:
The question concerns the photosynthesis process and aims to identify which of the listed options is neither a reactant nor a product of photosynthesis. In photosynthesis, water (H2O) and carbon dioxide (CO2) are reactants, and oxygen (O2) and glucose (C6H12O6) are products.
Therefore, the component not involved as a net product or reactant in photosynthesis is ATP. While ATP is produced and consumed within the Calvin cycle of photosynthesis, it is not a net product of the overall process. The net products are glucose and oxygen, which emerge as the final substances after the entire process.