Q. During the day which process is the major driving force in the movement of water in the xylem?
Answer: Transpiration pull
Notes: During the day when stomata are open, the transpiration pull becomes a major driving force in the movement of water in the xylem. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism. The remaining 97–99.5% is lost by transpiration and guttation.