The source of basic material used for production of glucose in the Calvin cycle (light-independent reactions) is carbon dioxide (CO2).

Here's why:

* Calvin Cycle: This cycle is all about fixing carbon from the atmosphere into organic molecules.

* CO2 Fixation: The first step of the Calvin cycle is the incorporation of CO2 into an existing five-carbon sugar called RuBP (ribulose bisphosphate). This reaction is catalyzed by the enzyme Rubisco.

* Glucose Formation: The fixed carbon is then used to build sugars, including glucose, through a series of enzymatic reactions.

So, while the energy for the Calvin cycle comes from ATP and NADPH generated in the light-dependent reactions, the building blocks for glucose are ultimately provided by CO2.