Photosynthesis converts carbon dioxide to glucose
The main idea of photosynthesis is that it takes in carbon dioxide and uses that carbon with water to convert it into a chemical form like glucose.
Without light, you cut the plant off from the energy needed to produce photosynthesis. Without water or CO2, you choke the plant from the essential building blocks that is the plants structure.
So water is H2O which provides oxygen and hydrogen. Carbon dioxide is CO2 which provides carbon and oxygen.
The plants use solar energy to break apart the carbon dioxide in the air, and use the carbon for plant material in turn releasing the oxygen. This cycle involving photosynthesis is the short term carbon cycle.