Question

What is transpiration ? When does it occur?

Answer 1

Transpiration is the evaporation of water from plants. It occurs chiefly at the leaves while their stomata are open for the passage of CO₂ and O₂during photosynthesis.

But air that is not fully saturated with water vapor will dry the surfaces of cells with which it comes in contact.

So the photosynthesizing leaf loses substantial amount of water by evaporation.

This transpired water must be replaced by the transport of more water from the soil to the leaves through the xylem of the roots and stem.

Transpiration is not simply a hazard of plant life. It is the "engine" that pulls water up from the roots to:

• supply photosynthesis (1%-2% of the total);
• bring minerals from the roots for biosynthesis within the leaf ;
• cool the leaf.

Transpiration can occur any time.

Obviously the rate of transpiration depends on the amount of light , temperature, wind and humidity.

So amount of water transpired on a hot and humid day is much more than that on a rainy day.


And of course, during the day, when the sun is out, the transpiration is more compared to night whic is cooler.