Which gaseous reactant is required for photosynthesis in plants?

• A. Carbon dioxide (CO2)
• B. Nitrogen (N2)
• C. Hydrogen gas (H2)
• D. Oxygen (O2)

Answer: (A)

Verified step by step guidance

1. Recall the overall chemical equation for photosynthesis, which is: \$6\,CO_2 + 6\,H_2O + light \ energy \rightarrow C_6H_{12}O_6 + 6\,O_2$.
2. Identify the gaseous reactants in this equation. Notice that carbon dioxide (\(CO_2\)) and water (\(H_2O\)) are the reactants, but only \(CO_2\) is a gas under normal conditions.
3. Understand that plants take in carbon dioxide from the air through small openings called stomata in their leaves.
4. Recognize that oxygen (\(O_2\)) is actually a product of photosynthesis, released into the atmosphere, not a reactant.
5. Conclude that the gaseous reactant required for photosynthesis is carbon dioxide (\(CO_2\)), as it is essential for the plant to produce glucose.