Environmental Factors Affecting Leaf Water Potential Gradient

Steps:

• Transpiration rate lowers leaf water potential, steepening the gradient from soil to leaf.
• Factors altering transpiration inversely affect gradient steepness: decreased rate reduces gradient.
• Assess each option: factor change impacts transpiration, then gradient.
• Match to correct prediction of gradient change.

Why C is correct:

• Increasing relative humidity reduces vapor pressure deficit (VPD = leaf-air humidity difference), slowing transpiration and decreasing water potential gradient.

Why the others are wrong:

• A: Decreasing temperature reduces evaporation rate, lowering transpiration and gradient.
• B: Decreasing wind speed thickens boundary layer, reducing transpiration and gradient.
• D: Increasing sunlight opens stomata and boosts evaporation, raising transpiration and gradient.

Final answer: C