C9

Question 1

What are the needs of plant transport systems?

Answer 1

-Metabolic demands
-Size
-Small SA:V ratio

Question 2

What is a dicotyledonous plant

Answer 2

Plants that produce seeds containing two cotyledons (organs that act as food stores)

Question 3

What is the transport system in dicots

Answer 3

Vascular system

Question 4

What is a vascular bundle?

Answer 4

Vascular system of herbaceous dicots made up of xylem and phloem tissue

Question 5

Where are vascular bundles in the stem?

Answer 5

Edge

Question 6

Where are vascular bundles in the root?

Answer 6

Centre

Question 7

Where are vascular bundles in the leaf?

Answer 7

Midrib of the leaf

Question 8

What is a a xylem

Answer 8

Plant transport tissue that carries water and minerals from root to other parts of the plant, provides support

Question 9

What is the structure of xylem

Answer 9

-Non-living cells
-Xylem vessels which are long hollow structures made by columns of cells fusing
-Xylem parenchyma packs around xylem, storing food
-Xylem fibres which are long cells with lignified secondary walls to provide mechanical strength

Question 10

What is the phloem?

Answer 10

Plant transport tissue that carries products of photosynthesis to all cells of plant

Question 11

What is the structure of the phloem

Answer 11

-Sieve tube elements
-Many cells joined together forming long, hollow structure
-Perforated walls to form sieve plates

Question 12

What are companion cells

Answer 12

Active cells found next to sieve tube elements that supply the phloem vessels with all their metabolic needs

Question 13

How are companion cells and sieve tube elements linked?

Answer 13

By plasmodesmata- microscopic channels through cellulose walls linking cytoplasm

Question 14

What is the importance of water in plants?

Answer 14

-Turgor pressure provides hydrostatic skeleton supporting plants
-Turgor drives cell expansion
-Loss of water cools plants
-Transport of mineral ions in solution
-Raw material for photosynthesis

Question 15

How are root hair cells well adapted as exchange surfacesc

Answer 15

-Microscopic so can penetrate between soil particles
-Large SA:V ratio
-Thin surface layer so short Diffusion distance
-Concentration of solutes in cytoplasm maintains water potential gradient

Question 16

Why does water move into root hair cell from soil

Answer 16

Root hair cell has lower water potential than soil as root hair cell contains different solvents

Question 17

What are the two different pathways water can take across the root

Answer 17

Symplast pathway
Apoplast pathway

Question 18

What is the symplast pathway?

Answer 18

Movement of water and solutes through the cytoplasm of the cells via plasmodesmata by diffusion

Question 19

How does water move through the symplast pathway

Answer 19

Root hair cell takes in water giving it a higher water potential than next door cell so water moves to that cell via osmosis
Process continues until it reaches xylem

Question 20

What is the apoplast pathway?

Answer 20

Movement of substances through the cell walls and cell spaces by diffusion and into the cytoplasm by active transport

Question 21

How does water move through the apoplast pathway

Answer 21

Water fills spaces between loose open network of fibres in cellulose cell wall
As water molecules move into xylem, more molecules move through apoplast due to cohesion
Creates tension causing continuous flow of water

Question 22

How is water moved in the xylem

Answer 22

Water from apoplast pathway reaches endodermis - layer surrounding vascular tissue in roots
Water forced into cytoplasm due to waterproof Caparian strip
Passes through selectively permeable membrane
Joins water in symplast pathway
Water potential of xylem is lower, so water moves through endodermis by endodermis through symplast pathway
Returns to apoplast pathway to enter xylem

Question 23

What is root pressure

Answer 23

Active pumping of minerals into the xylem by root cells that produces movement of water into the xylem

Question 24

What is evidence for active transport in root pressure

Answer 24

-Some poisons affect mitochondria and prevent production of ATP, when applied to roots, there is no energy supply and root pressure disappears
-Increases with rise in pressure
-Oxygen falls, root pressure falls
-Xylem sap exudes from cut stems

Question 25

Photosynthesis

Answer 25

CO2 + H2O —> O2 + C6H12O6
Provides food for plants

Question 26

How are leaves adapted for photosynthesis

Answer 26

Large SA to catch sunlight
Waxy cuticle coating to make them waterproof

Question 27

How do gasses leave and enter the plant?

Answer 27

Stomata

Question 28

What is a stomata

Answer 28

Pores in the surface of the leaf that may be opened or closed by guard cells

Question 29

What is transpiration

Answer 29

Loss of water vapour from stems and leaves of a plant as a result of evaporation and diffusion

Question 30

What is the transpiration stream

Answer 30

Water moves by osmosis through apoplast pathway from xylem to leaf, where it evaporates

Question 31

What is capillary action?

Answer 31

Movement of water through xylem due to difference in water potential, cohesion and adhesuom

Question 32

What is cohesion tension theory

Answer 32

Model explaining movement of water through a plant during transpiration

Question 33

Explain cohesion tension theory

Question 34

What is evidence for cohesion tension theory?

Answer 34

-When transpiration is at its height, tension in xylem is high, tree shrinks in diameter
-When xylem vessel broken, air drawn in rather than water leaving

Question 35

What are factors affecting transpiration?

Answer 35

-Light keeps stomata open for gas exchange
-Humidity
-Temperature increases evaporation and decreases relative humidity of air
-Air movement
- Soil water availability

Question 36

What is translocation?

Answer 36

Movement of organic solutes around a plant from source to sink

Question 37

Is translocation active or passive

Answer 37

Active process

Question 38

Main sources of assimilates

Answer 38

Green leaves and green stems
Storage organs
Food stores in seeds

Question 39

What are sinks in plants

Answer 39

Roots that are growing
Meristems

Question 40

What is phloem loading?