Biology B2 - Transpiration & Stomata

List the 4 main things transpiration rate is affected by

-light intensity

-temperature

-air flow

-humidity

Expain how light intensity affects the transpiration rate

the brighter the light, the greater the transpiration rate

When does the stomata begin to close?

when its gets darker

Why does the stomata close when it's dark?

because the stomata is open to let c02 in but since c02 is needed for photosynthesis and photosynthesis can't happen in the dark, there is no need for the stomata to stay open

When the stomata is closed, what happens?

very little water can escape

explain how the temperature can affect transpiration rate

the warmer it is, the faster transpiration happens

Why when it's warm transpiration happens faster?

the water particles have more energy to evaporatate and diffuse out of the stomata

explain how air flow can affect transpiration rate

the better the air flow around the leaf (eg stronger wind), the greater the transpiration rate.

What happens if air flow around the leaf is poor?

The water vapour just surrounds the leaf and doesn't move away. This means there is a high concentration of water particles outside the leaf as well as inside it, so diffusion doesn't happen as quickly

What happens if there is good air flow around the leaf?

the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf.

-diffusion then happens quickly from an area of high concentration to an area of low concentration

explain how humidity can affect transpiration rate

the drier the air around a leaf, the faster transpiration happens

What happens is the air is humid?

the leaf already has a lot of water in it, so there's not much of a difference between the inside and outside of the leaf

How can you estimate the rate of transpiration?

by meausuring the uptake of water by a plant

Why is this?

because you can assume that water uptake by the plant is directly related to water loss by the leaves (transpiration)

What are guard cells adapted to do?

open and close stomata

What shape do guard cells have

kidney shape

What happens when a plant has lots of water

The guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.

What happens when the plant is short of water?

The guard cells lose water and become flaccid, making the stomata close. This helps stop too much water vapour escaping

What makes the opening and closing of walls work in a plant

thin outer walls and thickened inner walls

What are guard cells sensitve to?

light

Why do guard cells close at night

to save water without losing out on photosynthesis

Where do you usually find more stomata

On the undersides of leaves as the lower surface is shaded and cooler so less water is lost through the stomata than if they were on the upper surface.

What are guard cells adapted for?

Gas exchange and controlling water loss within a leaf