Transport system - Plants

Question 1

Identify the organs in a plant

Answer 1

Plant organs are the leaves, stems and roots of a plant.

Question 2

Describe the external features of a leaf in relation to their functions

Answer 2

External features
- Thin structure with a large flat surface area
- Waxy cuticle
- Upper epidermal cells
- Paliside mesophyl
- Spongey mesophyl
- Lower epidermis
- Guard cells
- Stomata (pores)

Question 3

What does a waxy cuticle do?

Answer 3

• The waxy cuticle is a waterproof layer to prevent rain from entering the leaf

Question 4

What does the upper epidermis do?

Answer 4

• The Upper epidermis are transparent to let light energy pass through them to the cell layers below

Question 5

What does the Palisade mesophyll do?

Answer 5

• Palisade mesophyll contains loads of chloroplasts making it the place where most photosynthesis happens

Question 6

What does Spongey mesophyll do?

Answer 6

• Spongey mesophyll allows rapid gas exchanges by diffusion

Question 7

What does the lower epidermis do?

Answer 7

• The lower epidermis is a lower lining containing guard cells which form stomata

Question 8

What do guard cells do?

Answer 8

• The guard cells control the size of the stomata (pores) and

Question 9

What does stomata do?

Answer 9

-The stomata takes in carbon dioxide and releases oxygen

Question 10

Explain the need for transport systems in plants

Answer 10

move water and minerals upwards from the roots to the leaves and to move sugars, mainly downwards from the leaves to the rest of the plant

Question 11

What is osmosis?

Answer 11

The movement of water molecules from a high concentration to a lower concentration down a concentration gradient through a selectively permeable membrane

Question 12

Describe how root hair cells are specialised to absorb water

Answer 12

Extended surface area and large vacuole to allow absorption of water by osmosis

Question 13

State the function of xylem vessels

Answer 13

Xylem vessels transport water and minerals upwards from the roots to the aerial parts of the plant

Question 14

Describe the structure of xylem vessels

Answer 14

Xylem vessels are hollow tubes lined with rings or spirals of strong waterproof lignin. The hollow tubes have been formed from the remaining walls of dead cells and create a system of pipes to allow transport of water and minerals upwards from the roots

Question 15

Explain why xylem vessels are lignified

Answer 15

The walls of the xylem vessels are lignified to allow them to cope with the pressure changes that take place when water is being transported upwards by the transpiration pull without collapsing in on themselves.

Question 16

Describe the movement of water and minerals from the soil to the air

Answer 16

Water and minerals are moved into the root hair cells from the soil by osmosis and diffusion and then they are transported upwards through the xylem vessels by the transpiration pull. The transpiration pull moves the water and minerals up to the leaves where they exit the xylem vessel to enter either; the palisade mesophyll cells for use as a raw material for photosynthesis, or the air spaces in the spongy mesophyll layer where the water becomes water vapour that evaporates out of the leaf through a stoma by transpiration

Question 17

State the definition of transpiration

Answer 17

Transpiration is the movement of water through a plant and loss of water from the aerial parts (leaves) of a plant by evaporation

Question 18

Identify the structures in a leaf through which most water is lost by evaporation

Answer 18

Most water is lost by evaporation through the stomata that are found between pairs of guard cells mainly in the lower epidermis of a leaf

Question 19

State how plants can control their water loss

Answer 19

Plants can control their water loss via transpiration by opening and closing their stomata. A pair of guard cells control the size of the stomata between them. When the stomata are closed water loss through the stomata is prevented. Stomata are mainly closed at night and open during the day

Question 20

Identify the four factor that affect the rate of transpiration

Answer 20

1. Temperature
2. Surface area of leaf
3. Wind speed
4. Humidity

Question 21

State the effect of each factor on the rate of transpiration

Answer 21

• As temperature, surface area and wind speed increases the rate of transpiration increases
• As the humidity increases the rate of transpiration decreases. As the humidity decreases the rate or transpiration increases

Question 22

State the function of phloem tissue

Answer 22

Phloem tissue transports sugars from the leaves (where they are made by photosynthesis) to other parts of the plant

Question 23

Describe the structure of phloem tissue

Answer 23

Phloem tissue is living and made up of two different types of cells - sieve tubes with sieve plates and combustion cells. Sieve tubes have no nucleus and holy end walls to allow transport of cytoplasm containing dissolved sugars between neighbouring phloem cells. A companion cell has enlarged nucleus that controls both itself and its neighbouring sieve plate cell