Which gas is absorbed by plants during photosynthesis?

During photosynthesis, plants primarily absorb carbon dioxide from the atmosphere. This process takes place in the chloroplasts of plant cells, where sunlight is used to convert carbon dioxide and water into glucose and oxygen. The carbon dioxide serves as a key reactant in the photosynthetic equation, facilitating the conversion of light energy into chemical energy stored in glucose.

Absorption of carbon dioxide is crucial because it provides the carbon atoms that are ultimately incorporated into glucose molecules, which serve as an energy source for the plant. During the light-dependent reactions of photosynthesis, water is split, releasing oxygen as a byproduct, but it is the carbon dioxide that is actively absorbed for use in the Calvin cycle, where it is fixed into organic compounds.

The other gases listed—oxygen is a product of photosynthesis rather than a reactant, nitrogen is not utilized in this process, and hydrogen also does not play a direct role in the absorption aspect during photosynthesis—reinforce the significance of carbon dioxide as the correct answer.