Answer:
H2O
Step-by-step explanation:
Calvin cycle is the name given to a set of chemical reactions that occur in the chloroplast stroma. This important route was discovered by Melvin Calvin, who won the Nobel Prize in 1961 for his discovery. The chemical reactions that make up the Calvin cycle occur in the carbon fixation step, one of the photosynthesis phases. In this cycle, CO2 is reduced to glyceraldehyde 3-phosphate and ribulose 1.5 bisphosphate, CO2-acceptor, is regenerated. This is all done with the energy expenditure provided by the ATP and NADPH molecules. For this reason, we can say that for the Calvin cycle to occur, ATP, NADPH, and CO2 must enter the system.
H2O is not required at this time.