Question

Statement I: The forces generated by transpiration can lift a xylem-sizéd column of water over 130 meters height.

Statement II: Transpiration cools leaf surfaces sometimes 10 to 15 degrees, by evaporative cooling.

In the light of the above statements, choose the most appropriate answer from the options given below:

Options

• Both Statement I and Statement II are incorrect.

• Statement I is correct but Statement II is incorrect.

• Statement I is incorrect but Statement II is correct.

• Both Statement I and Statement II are correct.

Answer 1

Both Statement I and Statement II are correct.

Explanation:

• Statement I is correct: According to the cohesion-tension theory, transpiration generates a negative pressure (suction) within the xylem. This force, supported by capillary action and the strong attraction between water molecules, creates a continuous pull capable of lifting water to great heights.
• Statement II is correct: Transpiration facilitates evaporative cooling, which regulates leaf temperature. As water evaporates through the stomata, it absorbs and removes heat, typically lowering the leaf's temperature by 10 to 15 degrees Celsius though this cooling effect can vary based on external conditions.