Which feature of a plant leaf most directly helps maximize photosynthesis by improving light capture and gas exchange?

• A. A broad, thin blade with many chloroplast-rich mesophyll cells and stomata for CO2 uptake
• B. A thick waxy cuticle that greatly increases water loss to speed sugar production
• C. A high density of lignified xylem throughout the mesophyll to block light and reduce evaporation
• D. An absence of intercellular air spaces so CO2 diffuses only through veins

Answer: (A)

Verified step by step guidance

1. Identify the main goal of the leaf feature in the context of photosynthesis, which is to maximize light capture and facilitate gas exchange (CO2 uptake and O2 release).
2. Understand that a broad, thin leaf blade increases the surface area exposed to sunlight, allowing more light to be absorbed by chloroplasts for photosynthesis.
3. Recognize that mesophyll cells are rich in chloroplasts, the organelles where photosynthesis occurs, so having many of these cells enhances the leaf's ability to convert light energy into chemical energy.
4. Note that stomata are pores on the leaf surface that allow CO2 to enter the leaf and O2 to exit, which is essential for photosynthesis and gas exchange.
5. Evaluate the other options by considering their effects on photosynthesis: a thick waxy cuticle reduces water loss but can limit gas exchange; lignified xylem blocks light and is not involved in photosynthesis; absence of intercellular air spaces would hinder CO2 diffusion, reducing photosynthesis efficiency.