Transpiration

Transpiration

evaporation of water vapour/molecules from the underside of the leaves (stomata)

Where other part of the leaf can the stomata evaporate from?

Epidermis

Where is stomata found

underside of leaves

What is each stomata surrounded by?

Guard Cells

What is the function of guard cells?

change shape to open or close the stomata

How can water enter the guard cells?

Osmosis

Turgid:

Active transport of K+ lowers ________ ____________.

Water enters by ________

Guard cells are ______ which causes the stoma to ______

water potential

osmosis

swollen

open

Flaccid

Guard cells __________ which causes them the stoma to _______

shrink

close

What genetic factors affect the rate of transpiration

Number, distribution and the size of the stomata

What environmental factors affect the rate of transpiration

Temperature

Humidity

Air Speed

Light Intensity

Temperature:

As temperature increases, it ______ the water potential of the atmosphere. it increases the __________ ________ of water molecules, accelerating their rate of ______________, from the walls of the mesophyll cells and if stomata are ______, it speeds up their rate of diffusion into the atmosphere. The ________ temperature causes the water molecules to ______ away from the leaf more quickly reducing _______ _________ around the leaf.

lowers

kinetic energy

evaporation

open

higher

diffuse

water potential

Humidity

The lower the humidity, the faster the rate of transpiration. If the air around the plant is dry, the concentration gradient between the leaf and the air is increased

Air movement

The windier it is, the faster the rate of transpiration. Lots of air movement blows away water molecules from the stomata. This increases the concentration gradient

Light Intensity

The higher the light intensity, the faster the rate of transpiration.

Stomata open allowing CO2 to enter the leaf to facilitate photosynthesis.

The rate of transpiration slows during the night due to this.

What is the formula for the rate of transpiration

Rate= Volume/Time

What is the formula for volume

3.14 x r² x h