B8 - Transport in Plants

Question 1

What is the function of the xylem? [2]

Answer 1

• transport water and mineral ions
• support

Question 2

What is the structure of a xylem vessel like? [3]

Answer 2

• made up of dead cells
• no end walls between cells
• cells are strengthened with lignin

Question 3

What is the function of the phloem? [1]

Answer 3

• transport of sucrose and amino acids

Question 4

What is the structure of a phloem vessel like? [3]

Answer 4

• made up of living cells
• end walls have perforated sieve plates
• cells walls made of cellulose

Question 5

How are the minerals in the xylem vessel transported? [1]

Answer 5

via active transport

Question 6

How is water moved to the roots? [1]

Answer 6

via osmosis

Question 7

What do xylem vessels not have? [2]

Answer 7

• no cell wall
• no cell membrane

Question 8

Where does the xylem vessel transport to and from? [2]

Answer 8

• transports to the stems, leaves and flowers from the roots

Question 9

What structure do the xylem and phloem form? [1]

Answer 9

vascular bundles

Question 10

What are vascular bundles used for? [2]

Answer 10

• transport
• support

Question 11

What is the flowage like in a xylem vessel? [1]

Answer 11

one-way flow only
- from root to the rest of the plant

Question 12

What is the flowage like in a phloem vessel? [1]

Answer 12

two-way flow movement

Question 13

What is unique about the cells in a phloem vessel? [1]

Answer 13

cells are living but they need support from companion cells

Question 14

What are perforated sieve plates? [1]

Answer 14

it lets some things in and not others

Question 15

Why are companion cells used in phloem vessels? [2]

Answer 15

• phloem cells are living but have no nucleus and very little cytoplasm
• they are supported by companion cells that have all the cell organelles

Question 16

What are 3 differences between xylem and phloem vessels? [3]

Answer 16

1. xylem = no end plates whereas phloem = perforated sieve plates
2. xylem = one-way flow of movement whereas phloem = two-way flow of movement
3. xylem = made up of dead cells whereas phloem = made up of living cells

Question 17

Where is the xylem and phloem located in the roots? [2]

Answer 17

• middle = the cross
• outside the cross

Question 18

Where is the xylem and phloem located in the stem? [2]

Answer 18

• the inside = small dots
• the outside = one dot

Question 19

Where is the xylem and phloem located in a leaf? [2]

Answer 19

• up = thicker and bigger
• down = smaller

Question 20

What is transpiration? [2]

Answer 20

the loss of water from plant leaves by evaporation of water at mesophyll cells and then diffusion of water vapour through the stomata

Question 21

How is water lost from the leaves? [3]

Answer 21

• from the leaves
• to the air
• out of the stomata

Question 22

What are adaptations of root hair cells? [2]

Answer 22

• large surface area
• increases the rate of absorption of water by osmosis

Question 23

How does water travel to the leaves? [2]

Answer 23

• up the stem
• in the xylem

Question 24

Where is water absorbed from and by? [2]

Answer 24

• absorbed from soil
• absorbed by roots

Question 25

How do minerals in the water get into the roots? [1]

Answer 25

via active transport

Question 26

What does active transport require? [3]

Answer 26

- energy - ATP - carrier protein

Question 27

Where does the process of evaporation occur? [1]

Answer 27

from cells to air space

Question 28

Where does the process of diffusion happen? [1]

Answer 28

from stomata to atmosphere

Question 29

How does water move from the roots to the leaves? [3]

Answer 29

- loss of water in leaves reduces tension in the xylem vessels in the leaf - water moves up the xylem tube from high to low pressure - water molecules stick together as they are cohesive

Question 30

What is the Cohesion Tension? [1]

Answer 30

- water molecules are stuck together

Question 31

Which has a lower water potential: soil or root hair cell? [1]

Answer 31

root hair cell

Question 32

What is the transpiration stream? [2]

Answer 32

the movement of water through the plant from the root to the leaves

Question 33

What are the different places water moves through in the transpiration stream? [6]

Answer 33

- root hair cells - root cortex cells - xylem vessel - mesophyll cells - air space - stomata

Question 34

What is the path taken of the movement of water through a plant (transpiration stream)? Explain. [5]

Answer 34

- water enters the root hair cell by osmosis - water enters xylem from root cortex cells by osmosis - water enters mesophyll cells by osmosis - water evaporates from mesophyll cells into air spaces - water vapour leaves the leaf by diffusion through the stomata

Question 35

How is water pulled up the xylem? [1]

Answer 35

by tension and cohesion

Question 36

What are the factors affecting transpiration? [4]

Answer 36

- light intensity - wind speed - temperature - humidity

Question 37

How is brighter light advantageous for transpiration? [4]

Answer 37

- causes more stomata to open up - more water can diffuse out - stomata close in the dark to reduce water loss - when all stomata are open = transpiration rate at its max

Question 38

How is a higher temperature advantageous for transpiration? [2]

Answer 38

- the faster water evaporates from cells of the leaf - diffusion of water vapour out of the leaf increases

Question 39

How is the windier the weather advantageous for transpiration? [3]

Answer 39

- the more water vapour molecules are blown away from the leaf - steeper the concentration gradient between leaf and surrounding air - water diffuses more quickly out of the leaf

Question 40

How is humidity disadvantageous for transpiration? [3]

Answer 40

- more humid = more water vapour in the air - the smaller the concentration gradient between leaf and surrounding air - water diffuses more slowly

Question 41

What is the method when using a potometer? [4]

Answer 41

- lift up tube from beaker to take in an air bubble - air bubble moves towards the plant as water moves into the shoot and is lost via evaporation from the leaves - measure the distance the air bubble moves in a period of time - refill the tube using the reservoir and repeat the measurements

Question 42

What is the method when using a balance? [6]

Answer 42

- place a cut shoot from a plant in a measuring cylinder - pour layer of oil or use bung - weigh the whole apparatus - leave for a period of time - weigh again - calculate change in mass

Question 43

What is wilting? [1]

Answer 43

- the result of a water deficit in the plant

Question 44

When does wilting occur? [2]

Answer 44

when water loss through transpiration exceeds water uptake by the roots

Question 45

What does the loss of water in wilting lead to? [1]

Answer 45

- a loss of turgor pressure in the plant cells - cells become flaccid

Question 46

What is translocation? [2]

Answer 46

movement of sucrose and amino acids in the phloem from sources to sinks

Question 47

What is a source? [2]

Answer 47

parts of the plant that release sucrose and amino acids

Question 48

What is a sink? [2]

Answer 48

parts of the plant that use or store sucrose and amino acids

Question 49

What are the sources and sinks in summer? [2]

Answer 49

- sources: leaves - sinks: flowers, fruits, roots, bulbs, tubers

Question 50

What are ths sources and sinks in winter? [2]

Answer 50

- sources: storage organs like roots, bulbs, tubers - sinks: newly growing leaves

Question 51

Why can plant organs be both sources and sinks? [3]

Answer 51

- depends on the season - in summer more photosynthesis happens in the leaves so nutrients from the leaf go to the roots, etc - in winter there's less light so less photosynthesis so the roots store nutrients from previous photosynthesis reactions and so nutrients go from roots to leaves