Transpiration Flashcards
What is transpiration?
The evaporation of water from a plants surface, particularly through stomata (which open to let CO2 diffuse in for photosynthesis)
What factors affect the rate of transpiration?
Temperature
Humidity
Air movement
Light Intensity
How does light intensity affect the rate transpiration?
The stomata open to allow carbon dioxide to diffuse into the leaf for photosynthesis
Photosynthesis rate is faster in faster higher light intensities
—> more CO2 needed
—> more stomata open
How does temperature affect the rate of transpiration
Higher temp = increased kinetic energy of water molecules
= increased transpiration
How does humidity affect the rate of transpiration
humidity - a measure of water content of air
Affects the water potential gradient between air outside the leaf and air inside the leaf
How does humidity decrease the rate of transpiration?
The air around each stoma is ‘wet’
i.e high humidity
This increased the water potential of air
Which decreased the water potential gradient
This decreases transpiration
How does humidity increase the rate of transpiration
lower humidity increases the rate of transpiration
How :
low humidity means increased water potential of the air outside the leaf this reduces the water potential gradient and reduces the rate of transpiration.
How does air movement affect the rate of transpiration?
Disperses humid layer at leaf surface
—> decreases water potential of air
—> increases water potential gradient
Basically changed the water potential gradient by altering the rate at which moist air is removed from the leaf
What is a Xerophyte?
plants that are adapted to living in dry environments
—> adaptations reduce transpiration
What is Marram grass
A xerophyte
How does the thick waxy cuticle of Maram grass reduce transpiration
Thick waxy cuticle - larger diffusion pathway
How does the rolled up leaves in a Maram grass plant reduce transpiration
Traps air and water vapour to decrease the water potential gradient (humid microclimate)
How do leaf hairs in a Marram grass plant reduce transpiration?
Trap still air which decreases the water potential gradient
How do sunken stomata in a Marram grass plant reduce transpiration?
Reduced exposure to air currents which decreases the water potential gradient
what are other adaptations of xerophytes
long roots (deep/cover large surface area)
Swollen stems
Spines
