How do plants obtain the carbon dioxide (\(\mathrm{CO_2}\)) required for photosynthesis?

• A. By converting oxygen (\(\mathrm{O_2}\)) into carbon dioxide inside chloroplasts
• B. By absorbing it from the soil through their roots
• C. By producing it internally during cellular respiration
• D. By absorbing it from the atmosphere through stomata in their leaves

Answer: (D)

Verified step by step guidance

1. Understand the role of carbon dioxide (\(\mathrm{CO_2}\)) in photosynthesis: Plants use \(\mathrm{CO_2}\) as a raw material to produce glucose during the light-independent reactions (Calvin cycle) in chloroplasts.
2. Learn about stomata: Stomata are small openings on the surface of leaves that allow gases like \(\mathrm{CO_2}\) to enter and oxygen (\(\mathrm{O_2}\)) to exit. They are regulated by guard cells to control gas exchange and water loss.
3. Clarify the source of \(\mathrm{CO_2}\): Plants do not convert \(\mathrm{O_2}\) into \(\mathrm{CO_2}\), nor do they absorb \(\mathrm{CO_2}\) from the soil. Instead, they absorb \(\mathrm{CO_2}\) directly from the atmosphere through their stomata.
4. Explain why cellular respiration is not the source: Cellular respiration in plants produces \(\mathrm{CO_2}\) as a byproduct, but this \(\mathrm{CO_2}\) is not sufficient to meet the needs of photosynthesis. Plants rely on atmospheric \(\mathrm{CO_2}\) for photosynthesis.
5. Conclude with the correct process: Plants obtain the \(\mathrm{CO_2}\) required for photosynthesis by absorbing it from the atmosphere through stomata in their leaves.