Transport and Transpiration

7/30/2019 Transport and Transpiration

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Transport and water relations

in plants


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Transport of water and food in

plants


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How does water get in?


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The roots


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How does it travel around the

plant?


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Water and plant cells


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Hydrostatic skeleton

The pressure of eachcell wall against itsneighbour results in

stiffness that allows theplant to stay upright.


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If cells dont

have

enough

water in

them thenthe plant

wilts.


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What is Transpiration?

The loss of water vapour throughEVAPORATION from the

stomata, on the underside of theleaves
http://www.cornwallwildlifetrust.org.uk/images/jpgs/transpiration_b.jpg


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3 Forces help water

to travel through

the plant Osmotic pressure

as water enters

the root hairs

Cohesion

between water

molecules

Transpirationevaporation from

the stomata


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Stomata and Guard cells

Stomata are small pores

(holes) on the underside of

leaves

The cells to either side of

them are known as guard cells

These cells open or close the

stoma depending on how

much water is being lost from

the plant by transpiration


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Distribution of stomata


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Experiment to investigate

stomatal distribution

Use nail polish to make an impression of

the leaf When its dry, peel it off and view under a

medium power objective


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How guard cells work

Guard cells open to

allow gas exchange

They close to control

water loss


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When its wet

water enters the cell byosmosis

the outer walls can

expand but the inner

walls can not.

As the outer walls

enlarge, the inner walls

are pulled apart.

This opens the stoma

When its dry

Water leaves the cell by

osmosis

The guard cells shrink the stoma closes


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The potometer

A potometer can be used to

measure the rate of transpiration.


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Rate of transpiration

As the leaf loses water, so the air bubble

moves. The distance moved over a time

period is measured.


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The drier the air, the faster the transpiration rate!

Transpiration rate


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Plants have a transport system made upof tubes called xylem and phloem.

Xylem carries water and mineral salts from

the roots up the stem to the leaves. Phloem carries dissolved food from the

leaves to all parts of the plant.

Water passes into the root hairs from the

soil water by osmosis.

Summary


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Mineral salts are taken up by active

transport.

Leaves lose water to the air by

transpiration.

Transpiration is controlled by the openingand closing of stomata.

Environmental factors like wind, humidity

and temperature can affect transpiration.

Documents

Transport and Transpiration