Exchanging Materials in Plantstodhigh.com/clickandbuilds/WordPress/wp-content/uploads/... · 2018....

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Exchanging Materials in Plants


All living things need to exchange materials

Plants need to obtain

certain materials for

healthy growth, including:

sunlight

water

mineral ions

oxygen

carbon dioxide.

Like all organisms, plants have to get materials for growth

from their environment. Plants must then transport the

nutrients to the part of the plant that needs them.

Where do plants get these nutrients?


How are plants adapted for transport?

The cell and tissue structures in different parts of the plant

are adapted to allow transportation of essential materials.

Leaves are entry and

exit points for the gases

needed by plants.

Roots absorb water and

minerals from the soil.

Stems connect the roots to

the leaves, flowers and fruits.

They contain cells specially

adapted for transportation of

water, minerals and sugars.


Roots and uptake

Roots are adapted to obtain water and mineral ions.

Roots are long and thin, and divide into many branches.

This root network covers a large area in the soil.

Near the growing tips of roots are root hair cells. These

have projections that reach out between soil particles to

increase the surface area for absorption.

soil

mineral ions

and water

molecules

root

hair cell


Which cells transport nutrients?

The phloem and xylem are arranged as vascular bundles.

Plants contain two types of cell adapted for transportation.

Phloem cells transport sugars

produced in the leaves up

and down the stem to growing

and storage tissues.

Xylem cells transport water

and minerals up the stem from

the roots to the shoots and

leaves. This transport occurs

in one direction only.

Both phloem and xylem form continuous systems

connecting roots, stems and leaves.


Transporting water, mineral ions and sugar


Demonstrate water movement


Exchange of gases in plants

When the concentration of

carbon dioxide inside the

plant is low, it will diffuse in

from the air, through pores in

the leaves into the plant cells.

Plants use carbon dioxide and produce oxygen during

photosynthesis. These gases move in and out of the leaves

of plants by diffusion through the stomata.

If the concentration of

oxygen is high inside the

plant, it will diffuse from the

plant cells through the pores

and into the air.


Adaptations for gas exchange

Leaves are adapted to increase the rate of diffusion of

gases, and to reduce the rate of water loss by evaporation:

A flat leaf shape increases

the surface area for diffusion.Internal air spaces allow

the gases to reach cells.

Thin leaves

minimize

the diffusion

distance for

gases.

A water-

proof waxy

cuticle

reduces

water loss.

Guard cells control the opening and closing of the stomata

to regulate how much water is lost through these holes.


How do gases enter and leave plants?

Stomata are small holes, or pores, that can be found on

the underside of leaves. A single hole is called a stoma.

Each stoma is surrounded by two guard cells.

When guard cells gain

water, they curve outwards.

This opens the stoma,

allowing carbon dioxide in

and oxygen out.

Losing water causes the guard

cells to come closer together,

closing the stoma. This stops

the movement of gases, but

also prevents water loss.


Water and gas exchange in plants


What is transpiration?

Transpiration is the loss of water from the leaves of a plant.

Most of this occurs from the underside of a leaf, where the

water vapour can leave through open stomata.

In hot, dry and windy conditions, evaporation

of water from plant leaves is more rapid.

Transpiration rates also vary naturally in

response to environmental factors such as

temperature and humidity.

This loss of water at the leaf will cause

more water to be taken up by the roots.

However, if it cannot be replaced, the

stomata will close to prevent wilting.


Transpiration rates


Why does transpiration vary?


Transpiration – true or false?


Glossary


Anagrams


Multiple-choice quiz

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