Transport in plants

Question 1

Why do plants need transport systems?

Answer 1

To move substances to and from cells fast

Question 2

What does phloem transport?

Answer 2

Sugars

Question 3

What does xylem transport?

Answer 3

Water and mineral ions

Question 4

What system do xylem and phloem make up in a plant?

Answer 4

Vascular system

Question 5

What does the Xylem look like/ where is it on the cross section of a root?

Answer 5

A cross in the middle of the root

Question 6

What do the phloem look like/ where are they on the cross section of a root?

Answer 6

4 Triangle shapes in between the cross shape of the xylem

Question 7

Where is the xylem located on a leaf cross section?

Answer 7

The top

Question 8

Where is the phloem located on a leaf cross section?

Answer 8

The bottom

Question 9

Where is the xylem located on a stem cross section?

Answer 9

The middle

Question 10

Where is the phloem located on a stem cross section?

Answer 10

The outside

Question 11

Describe the key feature of xylem.

Answer 11

• Long tube-like elements
• The cells are dead (so no cytoplasm)
• Walls thickened with lignin
• Water moves into and out of the xylem the link small pits in the walls where there’s no lignin

Question 12

Describe the key features of phloem.

Answer 12

• Transports sugars
• Arranged in tubes
• Contains sieve tube elements and companion cells

Question 13

What are the key features of sieve tube elements (in phloem)

Answer 13

• Living cells
• Have holes in to allow solutes to pass through
• No nucleus and very few organelles
• Thin cytoplasm

Question 14

What are companion cells? What do they do?

Answer 14

Because sieve tubes elements don’t have a nucleus, the companion cells carry out the living functions for both themselves and the sieve tubes (eg: provide energy for active transport of sugars)

Question 15

Where does water enter the plant and how?

Answer 15

Through the root hair cells into the roots via osmosis

Question 16

How/ why does the water travel down a water potential gradient in a plant?

Answer 16

Because water is constantly evaporated from the leaves and absorbed via the roots, this creates a gradient that keeps water moving though from the roots (high water potential) to the leaves (low water potential)

Question 17

What is the symplast pathway?

Answer 17

Water travels through the living parts of the cells (the cytoplasm)

Question 18

What are plasmodesmata?

Answer 18

Small microscopic channels that connect cell cytoplasms in plants

Question 19

What is the apoplast pathway?

Answer 19

Water goes through non-living parts of the cells (cell walls).

Question 20

What is the Casparian strip and what pathway is it involved in?

Answer 20

A waxy strip in cell walls that forces water travelling via the apoplast pathway into the symplast pathway

Question 21

What is the main water pathway and why?

Answer 21

The apoplast pathway because it provides the least resistance

Question 22

Where does water leave the plant from?

Answer 22

The stomata

Question 23

How do cohesion and tension help move water up plants?

Answer 23

Water molecules are cohesive meaning they stick together and the evaporation of water creates tension (suction) which pulls the water up the leaf

Question 24

What is adhesion in transpiration?

Answer 24

Water molecules being attracted to the walls of the xylem vessels

Question 25

What four main factors affect transportation rate?

Answer 25

1) Light
2) Temperature
3) Humidity
4) Wind

Question 26

How does light affect the transpiration rate?

Answer 26

The lighter it is the faster the transpiration rate stomata open when it is light and close when it is dark

Question 27

How does temperature affect the transpiration rate?

Answer 27

The higher the temperature the faster the transpiration rate because warmer water molecules evaporate faster

Question 28

How does humidity affect the transpiration rate?

Answer 28

The lower the humidity the faster the transpiration rate because if the air around the plant is dry then water potential increases

Question 29

How does wind affect the transpiration rate?

Answer 29

The windier it is the faster the transportation rate because high air movement blows away water from around the stomata

Question 30

What are xerophytes?

Answer 30

Plants that are adapted to living in dry climates

Question 31

How are cacti adapted to dry climates?

Answer 31

1) Thick waxy cuticles to reduce water loss via evaporation
2) Spines instead of leaves to reduce surface area for water loss
3) They close their stomata at hottest times of day when transpiration rates are highest

Question 32

How is marram grass adapted to dry climates?

Answer 32

1) Stomata that are sunk in pits so they are sheltered from the wind
2) Hairs on epidermis to trap moist air to reduce the water potential gradient

Question 33

What are hydrophytes?

Answer 33

Plants that are adapted to living in aquatic habitats

Question 34

How are water Lillie’s adapted to living in aquatic habitats?

Answer 34

1) Air spaces in their tissues allow the plant to float increasing the amount of light they receive
2) Stomata on the upper surface of leaves to minimise gas exchange
3) Flexible leaves and stems to prevent damage from water currents

Question 35

What is translocation?

Answer 35

The movement of dissolved substances (sugars) to where they’re needed in a plant

Question 36

Where does translocation happen?

Answer 36

The phloem of a plant

Question 37

Where does translocation move sugars from and to?

Answer 37

From their source (where it’s made) to a sink (which here it’s used up)

Question 38

What is the mass flow hypothesis?

Answer 38

The sugars leave from the source that has a low water potential and a high pressure down the pressure gradient forcing the sap down to the sink where there is a high water potential and a low pressure

Question 39

What contents and where do they enter the phloem?

Answer 39

Water from xylem and solutes from companion cells

Question 40

What is active loading?

Answer 40

Used to move substances into the companion cells from surrounding tissues