CBSE Class 10 Answered

The transport of water and minerals in plants is carried out by xylem.

• Water enters the root hair through osmosis, and mineral ions enter the root cells by active transport.
• Both water and minerals move upward from cell to cell through the cortex of the root by osmosis.
• From the cortex, water and minerals are brought to the xylem.
• The sap which contains water and dissolved minerals move upwards from the root cells to xylem. The upward movement of sap is called the ascent of sap.
• The xylem vessels of the roots are in continuation with the xylem vessels of the stem.
• Due to difference in concentration of water in roots and soil, a column of water is created which ensures that water reaches to the parts located at a height.

Many factors play a role in ascent of sap and it takes place in many steps. They are as follows:

• Root pressure: The walls of the cells of root hairs are very thin. Water from the soil enters the root hairs because of osmosis. Root pressure is responsible for movement of water up to the base of the stem.
• Capillary action: Water in the stem rises up to some height because of capillary action.
• Adhesion-cohesion of water molecules: Water molecules make a continuous column in the xylem because of forces of adhesion and cohesion among the molecules.
• Transpiration pull: Loss of water vapour through stomata and lenticels in plants is called transpiration. Transpiration through stomata creates vacuum which creates a suction called transpiration pull. The transpiration pull sucks the water column from the xylem tubes and thus, water is able to rise to great heights in even the tallest plants.