ICSE Class 8 Answered

Factors Affecting the Rate of Transpiration:

Intensity of sunlight

• On a bright sunny day, stomata open fully, so transpiration is increased.
• On a cloudy day, stomata open partially, so transpiration is reduced.
• At night, stomata close; hence, transpiration is greatly reduced or negligible.

Temperature

• Increase in temperature of the air increases the rate of transpiration.

Velocity of wind

• Transpiration increases with rapid or active air movement.

Humidity

• If the air is humid, the rate of transpiration is reduced.

Carbon dioxide

• Increase in the CO₂ level in the atmosphere over normal 0.03% causes stomatal closure. Hence, it decreases the rate of transpiration.

Atmospheric pressure

• With a decrease in atmospheric pressure, the rate of transpiration increases.