Which of the following is NOT a factor that influences a plant's transpiration rate?

• A. Temperature
• B. Humidity
• C. Wind
• D. Soil Texture

Answer: (D)

Transpiration rate is driven by how easily water evaporates from the leaf and moves through the plant to the atmosphere. Temperature boosts the water vapor pressure difference and speeds evaporation, so hotter conditions increase transpiration. Low humidity creates a larger gradient between the moist leaf interior and the drier air, also increasing transpiration. Wind removes the water vapor near the leaf surface, preventing it from saturating the air and allowing more evaporation to occur. Soil texture, while it influences how much water the soil can hold and how available that water is to the plant, does not directly change the leaf-to-air evaporation process. It can affect how long water remains available and thus how long transpiration can continue, but it is not a direct driver of the rate itself.