That roles do atmospheric gases have in photosynthesis? O Carbon dioxide is from glucose during the light-gathering phase of photosynthesis. O Nitrogen is a reactant in photosynthesis that generates chlorophyll molecules. O Oxygen is produced from water during the light-gathering phase of photosynthesis. O Carbon dioxide is a reactant for photosynthesis that provides the carbon in glucose. O Nitrogen is produced during the synthesis phase of photosynthesis when chlorophyll reacts with wat