Plant Transport

Question 1

Why do plants require a transport system

Answer 1

High metabolic demand
Multicellular plant so diffusion won’t be quick enough to ensure cells receive strong supply of nutrients
Small SA:V ratio

Question 2

Relate the structure of xylem to its function

Answer 2

Long,continuous columns made of dead tissue , allowing transportation of water
Contain pits,allow water to move sideways between vessels
Thickened woody substance called lignin to provide structural support and prevent collapse inwards

Question 3

Relate the structure of phloem to its function

Answer 3

Plasmodesmata to allow flow of substances between cytoplasm of different cells
Sieve tube elements to transport sugar around the plant
Companion cells designed for active transport of sugars into tubes

Question 4

Describe the structure and function of the vascular system in the roots

Answer 4

Consists of xylem and phloem

Xylem arranged in an X shape to provide resistance against force

Question 5

Describe the structure and function of the vascular system in the stem

Answer 5

Consist of xylem and phloem

Xylem on the inside of the bundle to provide support

Question 6

Describe the structure and function of the vascular system in the leaves

Answer 6

Consists of xylem and phloem, forms due midrib and veins

Involved in transport and support

Question 7

Define transpiration

Answer 7

The evaporation of water from the leaves of a plan as a result of gaseous exchange

Question 8

What are the factors that affect the rate of transpiration

Answer 8

Increased light
Increased temperature
Increased humidity decreases transpiration
Increased air movements

Question 9

How can we measure transpiration rate

Answer 9

Photometer

Place the cut plant in a water filled tubes that contains one air bubble

Question 10

Define water potential as a mechanism of movement in plants

Answer 10

Water potential =the likely hood of water to move by osmosis down a conc gradient

Question 11

Explain the apoplastic pathway

Answer 11

Water moves through the cell walls and intercellular spaces

Can be used until water reaches Casparian strip

Question 12

Explain the symplastic pathway

Answer 12

Water moves through the cytoplasm via plasmodesmata

Water must be actively transported into cells

Question 13

Explain the cohesion tension theory

Answer 13

• water molecules from hydrogen bonds with each other, causing them to stick together
• surface tension of water creates sticking effect
• when water is lost via transpiration more can be drawn up the stem

Question 14

What are the adaption of XEROPHYTES that allow them to live in dry conditions

Answer 14

• Thick waxy cuticle
• Stomata often closed
• Hair to trap moist air

Question 15

What are the adaptation of HYDROPHYTES that allow them live in wet condition

Answer 15

Stomata often open
Air space for buoyancy
Wide , flat leaves

Question 16

How does translocation occur

Answer 16

Sucrose produced in leaves loaded into sieve tubes via active transport
Lowers water potential
Water move in from xylem
Assimilates move along sieve tube towards areas of lower hydrostatic pressure
Sucrose diffuses into surrounding cells

Question 17

How can you estimate the rate of transpiration

Answer 17

Using a potometer

Question 18

How can you investigate transpiration by using a potometer

Answer 18

1) Assemble potometer in water and insert shoot underwater
2) remove out of water BUT keep end of the capillary tube submerged into beaker of water
3) check if it’s air/water tight
4) Remove end of capillary tube from beaker until one air bubble had formed
5) record starting position of air bubble

Question 19

Why does putting a leaf with a bag effect transpiration

Answer 19

Increases humidity

Which increases transpiration

Question 20

What do plant organelles consist of

Answer 20

Vacuoles - cell sap

Chloroplasts - photo synthesis

Question 21

What is unique about plant cell walls

Answer 21

Rigid structure
Made of cellulose(beta glucose) - permeable substances can go in and out
Act as defensive mechanism, protect from invading pathogens
Gives shape

Question 22

Name and describe two pathways that water takes to reach xylem vessels at the base of the stem

Answer 22

Symplast- passing through the cytoplasm

Apoplast-between the cell walls

Question 23

Explain why movement of amino acid at the roots can maintain a pressure gradient along the phloem

Answer 23

At roots,substances produced in the leaves are likely to be unloaded from the phloem
Increases water potential in the sieve tubes, water then leaves
Reduces pressure inside sieve tube, root< leaf end

Question 24

Give one similarity and one difference between the position of the phloem in a transverse section of root tissue compared with a transverse section of stem tissue

Answer 24

Similarity: phloem is more towards the outer edge of the plant then the xylem
Difference : root,surrounds one central mass of xylem cell rather then discrete bundle in stem