Factors Influencing Transpiration Rate

Steps:

• Transpiration is the evaporation of water from plant leaves through stomata.
• Key factors include wind speed, humidity, light, and temperature, which affect water vapor diffusion.
• Wind removes humid air around leaves, speeding diffusion; low wind slows it.
• Evaluate options: only decreased air currents reduce the rate.

Why A is correct:

• Air currents (wind) disperse the boundary layer of humid air around leaves, facilitating water vapor diffusion; decreasing them thickens the layer, slowing transpiration per Fick's law of diffusion.

Why the others are wrong:

• B: Decreased humidity lowers external water vapor concentration, increasing the diffusion gradient and transpiration rate.
• C: Increased light intensity opens stomata wider, allowing more water vapor escape and raising transpiration.
• D: Increased temperature boosts kinetic energy of water molecules, accelerating evaporation and transpiration.

Final answer: A