"Transpiration is the pulling of water up from the soil by the plant because of the evaporation of water from the plant's leaves. If you think of soil like a sponge, transpiration is like placing a paper towel on the sponge -- the paper draws water away from the sponge as it evaporates off the paper. In the paper towel, this movement of water is called capillary action, but transpiration is similar in principle."