Question

Name the four main forces responsible for the ascent of sap.

Answer 1

Ascent of sap:

It is the upward movement of water along with minerals from roots to the upper parts of the plant by the stem.

It occurs through the tracheary elements of xylem

The four main forces responsible for the ascent of sap are:

1. Root pressure: It is the pressure that occurs in the xylem of roots mainly in cortical cells due to the inflow of water. It pushes the water and minerals in an upward direction. Root pressure develops largely due to the osmotic phenomenon.
2. Capillary action: It causes the water from the lower level to rise and fill up the vacuum created by the loss of water due to transpiration from the leaves.
3. Adhesion of water: The molecules of water stick to the walls of xylem vessels due to the adhesive property of water to the cell wall material. this is called adhesive force.
4. Transpiration pull: Water is lost from the leaf cells to the intracellular space, as a result of transpiration and develops a strong negative water potential. This negative pressure develops an upward pull over the water column.