2.57B - Factors affecting transpiration

Edexcel IGCSE Biology

what are the four main environmental conditions that impact the rate of transpiration?

• air movement/wind

• humidity

• temperature

• light intensity

effect of high air movement on the rate of transpiration

• increases transpiration rate

• good airflow removes water vapour from the air surrounding the leaf

• sets up concentration gradient between leaf and air

• increases water loss

effect of high humidity on rate of transpiration

• decreases transpiration rate

• humidity is measure of moisture in the air

• when air is saturated with water vapour the concentration gradient is weaker so less water is lost

effect of high light insensity on transpiration

• increases transpiration rate

• guard cells are responsive to light intensity

• when light intesntiy is high they are turgid and the stomata open allowing water to be lost

effect of high light intensity on rate of transpiration

• increases transpiration rate

• higher temperature = particles have more kinetic energy

• water molecules evaporate from the mesophyll and diffuse away faster