Transpiration is the process where water absorbed by plant roots through evaporation. It is important as it allows plants to absorb more water and nutrients from the roots while cooling the plant down. The rate of transpiration is affected by factors like light, humidity, temperature, wind, and leaf surface area. Transpirational pull refers to the pulling force inside the xylem tissue that causes water to move up from the roots to the leaves as water vapor is lost from the leaves.