Question

Transpiration and root pressure cause water to rise in plants by

• A. pushing it upward
• B. pushing and pulling it, respectively
• C. pulling it upward
• D. pulling and pushing it, respectively

Answer 1

The correct option is D pulling and pushing it, respectively

Transpiration is the loss of water from the aerial parts of plants mainly through stomata. This water loss creates a tension and pulls the water column up. This is called transpiration pull, a major force responsible for the ascent of sap.

As the ions are actively transported into the root from the soil, the water potential in the plant cell decreases as compared to the soil. Due to the difference in the water potential, water moves from a region of higher water potential to lower and enters the root.

The positive hydrostatic pressure developed in the xylem of the root due to the entry of water is called root pressure. Root pressure pushes the water column up and causes the ascent of sap.

Hence, transpiration pulls and root pressure pushes the water column causing upward movement of water.