Which combination of features tends to reduce transpiration?

• A. Thick cuticle, dense hairs, and few stomata
• B. Large leaves with many stomata
• C. Bright leaf surfaces
• D. Exposed roots

Answer: (A)

Transpiration is driven mainly by water loss through the leaf surface, especially via stomata. To reduce this loss, leaves can limit both the openings through which water vapor escapes and the evaporation from the leaf surface itself. A thick cuticle makes the epidermis less permeable, cutting down on water loss through the outer skin. Dense hairs create a boundary layer that slows air movement and keeps the leaf surface more humid, which reduces evaporation. Fewer stomata mean fewer pathways for water vapor to exit. Put together, these features work together to minimize water loss from the leaf, making this combination the most effective at reducing transpiration.

In contrast, large leaves with many stomata increase surface area and the number of stomatal openings, boosting transpiration. Bright leaf surfaces are often associated with higher light and stomatal activity, which can raise transpiration rather than reduce it. Exposed roots don’t directly affect the leaf’s water loss pathways, so they don’t contribute to reducing transpiration.