Wind enhances tree transpiration causing greater trunk shrinkage

Steps:

• Tree trunks shrink during the day as transpiration pulls water from xylem, reducing turgor in bark cells.
• Transpiration rate increases with factors that raise water vapor diffusion from leaves.
• Evaluate options: temperature affects evaporation rate, wind disrupts boundary layer, humidity alters gradient.
• Increased wind accelerates water loss most directly among options by speeding evaporation.

Why B is correct:

• Increased wind speed heightens transpiration by removing the humid air layer around leaves, increasing the diffusion gradient per Fick's law.

Why the others are wrong:

• A. Increased temperature boosts transpiration but also induces minor thermal expansion in tissues, limiting net shrinkage.
• C. Increased humidity lowers the vapor pressure deficit between leaves and air, reducing transpiration and shrinkage.

Final answer: B