Transpiration

Question 1

What is transpiration?

Answer 1

The evaporation of water from a plants surface especially its leaves

Question 2

Apart from photosynthesis and maintaining turgor, what do plants need water for?

Answer 2

-metabolic reactions
-transport dissolved mineral ions and assimilates
-help to maintain their temperature

Question 3

How does transpiration happen?

Answer 3

-When water evaporates from the surface of mesophyll cells into the air spaces in the spongy mesophyll
-Water vapour will then diffuse out of the stomata if they are open and there is a ψ gradient

Question 4

What will increase the rate of transpiration?

Answer 4

Anything which increases ψ gradient between air spaces inside the leaf and the outside air

Question 5

What are the 6 factors that affect the rate of transpiration?

Answer 5

-Light Intensity
-Temperature
-Humidity
-Wind/Air Movement
-Water Availability
-The Leaves

Question 6

How does light intensity affect the rate of transpiration?

Answer 6

More stomata open and more widely when light intensity increases to allow more CO2 in for photosynthesis allowing more water vapour to escape from the leaf

Question 7

What is the first way that temperature affects the rate of transpiration?

Answer 7

Stomata open wider when warmer temperature (lets more CO2 in so water vapour out) because the rate of photosynthesis increases at warmer temperature

Question 8

What is the second way that temperature affects the rate of transpiration?

Answer 8

Warmer water molecules have more kinetic energy so will evaporate into the air spaced quicker which increases the ψ gradient so water vapour will diffuse out of leaf quicker

Question 9

How does humidity affect the rate of transpiration?

Answer 9

Lower the humidity, faster rate of transpiration as the air around the plant is dry which increases the ψ gradient

Question 10

How does wind/air movement affect the rate of transpiration?

Answer 10

Water vapour surrounding the stomata is removed more quickly when its windy which maintains the ψ gradient, increasing the rate of transpiration

Question 11

How does water availability affect the rate of transpiration?

Answer 11

If there isn’t much water available in the soil, rate of transpiration will decrease as the guard cells lose their turgor which closes the stomata

Question 12

How do the leaves affect the rate of transpiration?

Answer 12

SA of leaves, number of stomata and thickness of waxy cuticle can also affect the rate of transpiration