Multiple choice

Root pressure is maximum when

  1. transpiration is high and absorption is very low

  2. transpiration is very low and absorption is high

  3. transpiration is very high and absorption is also high

  4. transpiration and absorption both are low
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Root pressure is the positive pressure that develops in the roots due to active water absorption. It is maximum when transpiration is very low (usually at night or high humidity) because less water is being pulled up by transpiration pull, and absorption remains high due to active transport in roots. This allows water to be pushed up the xylem. When transpiration is high, the tension created by transpiration pull dominates over root pressure.

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