Correct Option
The correct option is Both A and R are true and R is the correct explanation of A
Explanation
Transpiration is the biological process involving the evaporative loss of water from the aerial parts of plants, primarily through stomata. This process is central to the Cohesion-Tension Theory, which explains the ascent of sap (water and dissolved minerals) from roots to the upper parts of the plant.
Statement-wise Analysis
- Assertion (A): Correct. Transpiration serves a vital physiological function by generating a pulling force. This force facilitates the absorption of water and minerals from the soil by the roots and ensures their upward movement through the xylem to various plant parts.
- Reason (R): Correct. The mechanism driving this upward movement is the evaporation of water molecules from the leaf cells. As water evaporates, it creates a pressure deficit (suction pressure) or tension within the xylem vessels. This suction, known as transpiration pull, physically pulls the continuous water column from the roots up to the leaves.
- Relationship: The suction force described in the Reason is the direct physical mechanism that enables the absorption and upward movement described in the Assertion. Therefore, R is the correct explanation for A.
Key Takeaway
Transpiration pull acts as the primary driving force for the ascent of sap in tall plants, allowing water and minerals to move against gravity without the expenditure of metabolic energy by the plant.