Question

The extent of water absorbed by plant roots, carried through the plant and that gets evaporated from leaf surface is:

• A. (~ 20%)
• B. (~ 40%)
• C. (~ 60%)
• D. (~ 90%)

Hint:

Remember that plants act as solar-powered pumps.
Almost 99% of the water they absorb is lost via transpiration, which cools the leaves and drives the upward movement of essential mineral nutrients.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Plants absorb massive amounts of water from the soil through their root system to sustain physiological functions, transport nutrients, and maintain structural turgidity.
However, only a tiny fraction of the absorbed water is actually retained within the plant body for metabolic activities like photosynthesis, cell expansion, and growth.
The vast majority of the absorbed water is lost to the atmosphere through the stomata of leaves in a physiological process known as transpiration.

Step 2: Detailed Explanation:
- Transpiration is the inevitable consequence of stomatal opening, which is required for $\text{CO}_2$ uptake during photosynthesis.
- More than 90% to 99% of the total water absorbed by a plant's roots is carried through the xylem, moves into the leaves, and eventually evaporates from the leaf surfaces into the surrounding air.
- Less than 1% to 10% of the absorbed water remains in the plant tissue to drive cell division, vacuole expansion, and biochemical reactions.
- In warm, dry, or windy conditions, the transpirational pull is highly accelerated due to a steep vapor pressure deficit between the leaf interior and the dry atmosphere.
- Therefore, the nearest estimate representing the proportion of water lost through transpiration and evaporation is approximately 90%.

Step 3: Final Answer:
The extent of absorbed water that gets evaporated from the leaf surface is approximately 90%.