Xerophytic adaptations minimizing transpiration by reducing water potential gradient

Steps:

• Water potential gradient (ψ_leaf - ψ_atm) drives transpiration; reducing it slows water loss by increasing air humidity near leaf or maintaining high leaf ψ.
• Rolled leaves trap humid air inside, raising local ψ_atm and reducing gradient.
• Hairy leaves create a moist boundary layer via trapped water vapor, decreasing ψ difference.
• Fleshy leaves store water, sustaining high ψ_leaf to lessen overall gradient.
• Sunken stomata increase diffusion resistance but do not directly alter humidity or leaf ψ.

Why B is correct:

• Option B includes rolled leaves, hairy leaves, and fleshy leaves, which directly reduce the gradient per Fick's law of diffusion (rate ∝ Δψ / resistance), focusing on Δψ minimization.

Why the others are wrong:

• A includes sunken stomata, which mainly boosts resistance, not gradient reduction.
• C excludes hairy leaves, missing a key humidity-trapping adaptation.
• D omits rolled leaves, ignoring enclosure of moist air.

Final answer: B