Transport in Plants

Question 1

What is a xerophyte?

Answer 1

A plant that reproduces and lives in an area where water availability is very low. (e.g: cactus)

Question 2

How does a thick waxy cuticle help conserve water for xerophytes?

Answer 2

Helps minimise water loss by stopping the water vapour escaping from the epidermis.

Question 3

How does a sunken stomata help conserve the water for xerophytes?

Answer 3

Sunken stomate reduce air movement and produces a microclimate of humid air that reduces the water vapour potential gradient and so reduces transpiration.

Question 4

How does the reduced number of stomata help conserve water for xerophytes?

Answer 4

Reduces water loss by transpiration and also reduces their gas exchange capabilities.

Question 5

How does the reduced number of leaves conserve the water for xerophytes?

Answer 5

Less amount of stomata, and so less loss of water vapour.

Question 6

How do hairy leaves help conserve water for xerophytes?

Answer 6

They create a microclimate of still and humid air, reducing the water vapour potential gradient and minimising loss of water by transpiration from the surface of the leaf.

Question 7

How do curled leaves help conserve water for xerophytes?

Answer 7

Limits all of the stomata within a microenvironment of still, humid air to reduce diffusion of water vapour from the stomata.

Question 8

What is an example of a plant that has curled leaves as a feature to conserve water?

Answer 8

Marram Grass

Question 9

How do succulents help conserve water for xerophytes?

Answer 9

Succulent plants store water in parenchyma tissue in their stems and roots. Water is stored when it is in supply and then used in times of drought.

Question 10

What feature of a xerophyte’s roots help conserve water?

Answer 10

They have long roots that grow deep into the ground and can penetrate several metres. They also have shallow roots with a large surface area that is available to absorb rain shower.

Question 11

What is a hydrophyte?

Answer 11

A plant that lives in water.

Question 12

Why don’t hydrophytes have a waxy cuticle?

Answer 12

They don’t need to conserve water and so water loss is not an issue, meaning they don’t need a cuticle.

Question 13

How does the adaptation of always-open stomata on the upper surfaces help a hydrophyte survive?

Answer 13

Maximising the number of stomata increases gas-exchange.

Question 14

How do wide, flat leaves help a hydrophyte survive?

Answer 14

This lets them capture as much light as possible to photosynthesise.

Question 15

Why do hydrophytes only need small roots?

Answer 15

Because water can defuse directly into stem and leaf tissue so there is less need for the uptake of water in the roots.

Question 16

How do air sacs help a hydrophyte survive?

Answer 16

This enables the leaves and flowers of the hydrophytes to float to the surface of the water so they can access air.

Question 17

What is aerenchyma?

Answer 17

Specialised parenchyma (packing) tissue that forms in the leaves, stems and roots of hydrophytes.

Question 18

What are the functions of aerenchyma?

Answer 18

Makes the leaves and stems flotable.

It forms a low-resistance internal pathway for the movement such as oxygen to tissues below the water.

Question 19

What does anoxic mean?

Answer 19

Extreme low oxygen conditions.

Question 20

How does aerenchyma help hydrophytes cope with anoxic conditions?

Answer 20

They transport oxygen into the plants tissues.

Question 21

How is water taken up from the soil?

Answer 21

Through root hair cells.

Question 22

How is the process of osmosis able to uptake water from the soil into the plant?

Answer 22

Cells in the root contain mineral ions and solutes and so have lower water potential than the soil solution that surrounds them. So, water moves down a water potential gradient and into the root hair cell.

Question 23

Once the water has been absorbed, where does the water move through?

Answer 23

The cortex.

Question 24

What are the two pathways that water can run through once in the cortex?

Answer 24

The symplastic and apoplastic pathways.

Question 25

What is the symplastic pathway?

Answer 25

Water moves along the symplastic pathway in the cytoplasm by cells that are connected by plasmodesmata to create a continuous column of cytoplasm.

Question 26

What is the apoplastic pathway?

Answer 26

Water goes through the cell walls of cortex walls.

Question 27

What happens in the apoplastic pathway when water is meets the endodermis?

Answer 27

Water is forced to move out of the cell wall when it meets the endodermis due to the Casparian Strip. The barrier is impermeable so water will be unable to pass through it.

Question 28

Where does water travel up the stem of a plant?

Answer 28

Xylem Vessel.

Question 29

How is water potential of the Xylem Vessel kept low?

Answer 29

By moving ions in by active transport.

Question 30

How does water movie up the stem against the force of gravity?

Answer 30

Cohesion Tension

Question 31

What is cohesion tension in terms of plants?

Answer 31

When the water molecules stick together and so run up the stem without the necessity of gravity.

Question 32

How do water molecules stick together?

Answer 32

They form hydrogen bonds.

Question 33

Where does water evaporate from on the leaf?

Answer 33

The mesophyll cells.

Question 34

How is water vapour evaporated in the leaf?

Answer 34

The water moves down a gradient and diffuses out of the stomata into the air.

Question 35

What is capillarity?

Answer 35

The rise or fall of a liquid in a narrow tube, caused by the relative attraction of its molecules for each other and the tube wall. Cohesion and Adhesion tension.

Question 36

Where is the vascular bundle in the stem of a plant and why is it there?

Answer 36

It is around the stem and it’s there to give strength and support.

Question 37

Where are the vascular bundles in a root?

Answer 37

They are in the middle to help the plant withstand strains as the stems are blown by the wind.

Question 38

Where is the vascular bundle in a leaf of a plant?

Answer 38

The midrib of the leaf.

Question 39

What is tannin?

Answer 39

A bitter chemical that protects plant tissues from being eaten.