Evaporation of water through the leaves is known as transpiration, and it occurs readily only when environmental conditions such as humidity is high.
On the other hand, the absorption of water by root hairs which is then conducted by the xylem vessels up the stem to various parts of the plant is a important process that determines how water move through a plant to ensure cellular processes such as photosynthesis, respiration etc takes place.
Thus, the absorption of water by the roots plays a much more important role in the movement of water in a plant
An independent variable is the only variable that is changed while the rest is kept the same. In this setup, the doctor is using different creams on the same patient with the same skin condition so the independent variable is the skin cream and not the skin condition.
