Key area 5-The Need for Transport

Plant transport systems

We are learning to

• Identify the structures and functions of plant organs involved in the transpiration process.

• To explain why multicellular organisms need transport systems.

I can

• Labe a diagram of leaf structure and identify the various tissues.

• Identify the phloem and xylem found in the stem and describe what they transport.

Why do we need transport systems?

Why can multicellular organisms not gain raw materials this way?

Watch the video and find out!

How does an amoeba gain raw materials for chemical reactions?

Length of

each side

(cm)

Area of

each face

(cm2)

Surface

area of

cube

(cm2)

Volume

of the

cube

(cm3)

Ratio

SA/Vol

1

2

3

4

Calculate the surface area to volume ratio of each cube

1

9

4

6 1 6

16

54

24

96

8 3

64

27 2

1.5

How do plants transport materials to where they are needed?

Plants have vessels inside the stem which carries water from roots to leaves

Why do plants need water?

How does water get from the roots to the leaves?

Transpiration

Xylem and phloem vessels in the stem

Transpiration • Transpiration is the evaporation of water into the

atmosphere from leaves and stems of plants.

• Water moves from the roots of a plant to the leaves.

• Water is vital for the transport of minerals within a plant and for photosynthesis.

• Water is lost through pores, called Stomata, that are on the underside of a leaf.

.

Root hair cell

Xylem

Ring of lignin

Transpiration-Roots • Water taken in by the

roots. Root Hairs increase the surface area for the absorption of water from the surrounding soil.

• Water moves into the root hair cells by osmosis.

• The water builds pressure in the tissues and helps to ‘push’ the water up the plant.

A

J

Xylem

Rings of lignin

Transpiration-Xylem • It is dead tissue.

• The Lignin rings help keep the Xylem tissue open.

• Water and dissolved minerals (e.g. Na, K) travel in Xylem.

• Like a straw in a glass, the water ‘sticks’ the side of the Xylem which helps it move upwards against gravity.

• Water moves in only 1 direction.

Phloem transports sugars up and down the plant

Sieve plate

Sieve tube

Companion cell

Phloem

• The Phloem tissue is alive and carries sugars and organic molecules all around the plant. (upwards and downwards)

Tasks

1. What do we call the movement of water through a plant?

2. By which process does water enter the roots of a plant?

3. How and where (be specific) does water exit a plant?

4. Which vessel transports water through a plant?

5. In which direction does the water travel?

6. Which vessel transports food? In which direction is the food transported?

7. How are xylem vessels strengthened and kept open?

The tissues in a leaf

Label your own

Stomata

Guard cells

Palisade Mesophyll

Lower Epidermis

Upper Epidermis

Phloem

Xylem

Waxy cuticle

Tissue/Cell Function

Epidermis The main photosynthetic cells

Stomata A layer of cells for protection

Guard cells An opening in the leaf to allow for diffusion of gases

Spongy mesophyll Control the opening and closing of stomata

Waxy cuticle A layer of cells where diffusion of gases occurs

Palisade mesophyll A waterproof layer on the top of the leaf

Stomata under the microscope

Transpiration- Leaves

Epidermis

Guard Cell Guard Cell

Waxy cuticle

Palisade mesophyll

Spongy mesophyll

Starter: Quick Questions 1. Which tissue on the leaf transports water and

minerals?

2. Which tissue in the leaf transports Glucose?

3. Which of these tissues is living and which is non-living?

4. In which direction is water transported?

5. How does water travel from the soil into the root hair cells?

6. Through which structures in the leaf does water evaporate from?

7. What name do we give for the transport of water in a plant?

Factors affecting transpiration

We are learning to

• Explain what factors affect transpiration.

• Investigate how light intensity affects transpiration.

I can

• Carry out an investigation to see how various factors effect the rate of transpiration

• Analyse data

• Conclude the investigation.

Factors affecting transpiration

• What would increase the rate water evaporates from a leaf?

• The factors that would increase transpiration are:

– Increase in temperature

– Increase in wind speed

– Decrease humidity

– Increase in Light Intensity (opening of stomata)

– Increase in water supply

Measuring Transpiration

Reservoir (zeroing mechanism)

bubble

water

leafy cutting

Airtight seal

scale

A Bubble Potometer

Reservoir (zeroing mechanism)

bubble

water

leafy cutting

Airtight seal

scale

A Bubble Potometer

•A bubble is introduced to the capillary tube.

•As water is taken up by the plant and lost from the leaves the bubble moves along the scale.

•By comparing the start and end position of the bubble, it is possible to measure the transpiration rate.

Capillary tube

Carry out the experiment!

Volume of water transpired in 1 hour (ml)

Plant Species Normal With heater With lamp With fan

Q1. What do your results show? Did the factors you varied affect the rate of transpiration? Q2. Was there a difference in the rate of transpiration between the two plants? Why do you think this is? Q3. Try to explain why light intensity, wind movement and an increase in temperature affected the rate of transpiration. Q4. What do you think would happen to the rate of transpiration if you covered the underside of the leaf in petroleum jelly?