Answer:
Water ascent in plants, also known as transpiration, is the process by which water is transported from the roots to the leaves and other parts of the plant. It occurs through a series of interconnected tubes called xylem vessels, which are located in the stem and branches of the plant.
Step-by-step explanation:
The mechanism of water ascent in plants involves several factors:
Capillary action: Water moves up the xylem vessels by a process called capillary action, which is the movement of a liquid along the surface of a solid due to the cohesive forces between the liquid and solid.
Cohesion and adhesion: Water molecules are attracted to each other (cohesion) and to the walls of the xylem vessels (adhesion). This causes water to form a continuous column that stretches from the roots to the leaves.
Evaporation: Water is lost from the leaves of the plant through the process of evaporation, which occurs when water molecules escape from the surface of the leaves into the air. This loss of water creates a negative pressure (tension) in the xylem vessels, which helps to pull more water up from the roots.
Root pressure: In some plants, root pressure also plays a role in water ascent. This is the hydrostatic pressure that is generated within the root cells as a result of the active transport of ions and nutrients into the xylem vessels. Root pressure can help to push water up the xylem vessels, especially when the soil is moist and there is a high demand for water by the plant.