Step 1: Understanding the Problem:
Water absorption by plant roots is categorized into active and passive processes.
Active absorption utilizes metabolic energy (ATP) to generate root pressure, whereas passive absorption is purely driven by the physical pull of transpiration.
Step 2: Approach and Formula:
Determine the relationship between the transpiration rate (controlled by stomatal opening) and the dominant mode of water absorption.
Step 3: Detailed Explanation:
Passive absorption is responsible for almost \(98%\) of a plant's total water uptake.
When stomata are open (typically during the day), transpiration occurs rapidly, creating a strong negative tension or suction force called the transpiration pull.
This massive pull passively draws water up through the roots, entirely bypassing the need for energy-dependent active absorption.
Conversely, active absorption is primarily observed only when transpiration is negligible, such as when stomata are closed or during the night time.
Step 4: Final Answer:
Active absorption usually does not occur when stomata are open.