AP BIOLOGY

Detailed explanation-1: -The most important factor governing rate of transpiration is the vapour pressure gradient between internal environment of leaf mesophyll tissue and the environment. Thus, the most important factor affecting transpiration is the atmospheric humidity. At high levels of atmospheric humidity, less transpiration occurs.

Detailed explanation-2: -As the relative humidity of the air surrounding the plant rises the transpiration rate decreases. It is easier for water to evaporate into dryer air than into more saturated air. Increased movement of the air around a plant will result in a higher transpiration rate.

Detailed explanation-3: -At high atmospheric humidity, transpiration is low. This is because the rate of transpiration is directly proportional to the saturation deficit. It is dependent on the gradient of vapor pressure. Thus, the higher the humidity, the lower the rate of transpiration.