transport in plants

Question 1

Why do plants need a transport system?

Answer 1

to get water and minerals from the roots up to the rest of the plant;
to carry assimilates made at the leaves down through the plant

Question 2

What is the role of collenchyma and sclerenchyma?

Answer 2

to provide mechanical strength and support plant

Question 3

Where is sclerenchyma and collenchyma found?

Answer 3

in the vascular bundles

Question 4

Direction of flow in phloem and xylem

Answer 4

xylem - up
phloem - up or down as needed

Question 5

Describe the vascular bundle in the young root

Answer 5

Bundle in centre, xylem x shaped and phloem between arms of x shape

Question 6

Where is the endodermis in the young root?

Answer 6

surrounds the vascular bundle and medulla

Question 7

Where is the pericycle found?

Answer 7

Layer cells just inside the endodermis in young root

Question 8

What is the pericycle?

Answer 8

layer meristem cells able to differentiate

Question 9

Where are vascular bundles located in the stem?

Answer 9

Found around the outside of the stem

Question 10

How are vascular bundles organised in the stem?

Answer 10

phloem on outside, xylem inside, cambium layer between them. sclerenchyma on outer edge of vascular bundle

Question 11

Adaptations of xylem to its function (5)

Answer 11

aligned dead cells, continuous column;
thin tubes;
bordered pits;
lignification
no walls/contents to obstruct water

Question 12

How is capillary action maintained in the xylem?

Answer 12

thin tubes, water column doesn’t break easily - adhesion

Question 13

What are assimilates?

Answer 13

mainly sucrose and amino acids, dissolved in water to form sap, products of photosynthesis

Question 14

Describe the structure of the phloem (3)

Answer 14

sieve tube elements elongated;
perforated sieve plates between them;
companion cells between tubes

Question 15

What do companion cells do?

Answer 15

load assimilates into phloem

Question 16

How are sieve tube elements adapted for mass flow?

Answer 16

no nucleus and little cytoplasm

Question 17

How are companion cells adapted?

Answer 17

dense cytoplasm and large nucleus, many mitochondria to produce ATP for active processes

Question 18

What are plasmodesmata?

Answer 18

gaps in cell wall connecting cells by their cytoplasm

Question 19

Describe the apoplast pathway

Answer 19

• water enters cellulose cell wall by cohesive forces in water molecules

Question 20

Describe the simplest pathway

Answer 20

• water moves through plasmodesmata and cells
• enters cytoplasm
• using osmosis

Question 21

Describe the apoplast pathway

Answer 21

• water moves through molecules in cell wall
• by cohesive forces in water molecules
• does not enter cell

Question 22

How does water move between water potential?

Answer 22

from area of high potential to low

Question 23

What happens if plant cell placed in pure water/higher potential?

Answer 23

water moves in by osmosis until becomes turgid, cell wall prevents bursting, pressure potential between water and cell wall

Question 24

What does turgid mean?

Answer 24

plant cell intake lots of water, swells and cell membrane exerts pressure on cell wall

Question 25

What happens if plant cell placed in lower water potential?

Answer 25

water leaves by osmosis, cytoplasm and vacuole shrink, membrane will pull away from cell wall

Question 26

What does flaccid plant cell mean?

Answer 26

cell lost lot of water, cell membrane does not exert pressure on cell wall

Question 27

Term when plant tissue/cell loses a lot of water

Answer 27

flaccid

Question 28

What does plasmolysed mean?

Answer 28

cell membrane detached from cell wall due to water loss

Question 29

What is water potential?

Answer 29

Tendency of water molecules to move from one area to another

Question 30

What is transpiration?

Answer 30

loss of water (vapour) from plant via leaves

Question 31

How is water lost from a plant?

Answer 31

from leaves through stomata,

Question 32

Describe the pathway taken by water through the leaf

Answer 32

into cells of spongy mesophyll from xylem,
evaporates from cell walls and diffuses out of open stomata

Question 33

Loss of water out of the stomata depends on what?

Answer 33

Must be lower water vapour potential outside of the leaf

Question 34

Why is transpiration important? (4)

Answer 34

water moves transports minerals up plant;
maintains turgidity;
supplies water for growth, photosynthesis;
evaporation keeps plant cool

Question 35

Five factors which affect transpiration rate

Answer 35

temperature;
wind;
humidity;
light intensity;
water availability

Question 36

How does increased temperature affect the rate of transpiration?

Answer 36

higher = increase;
increased evaporation rate, water vapour potential in leaf rises;
thermal->kinetic energy increases diffusion rate;
potential gradient cause rapid diffusion—

Question 37

How does high light intensity affect the rate of transpiration?

Answer 37

higher light intensity causes stomata to open and water to leave, increases rate

Question 38

How does humidity affect the rate of transpiration?

Answer 38

humidity increases water potential outside leaf reducing rate transpiration, reduces concentration/potential gradient

Question 39

How does air movement affect the rate of transpiration?

Answer 39

Air carries away water vapour in the air, increasing potential gradient,/making water potential gradient steeper quicker transpiration

Question 40

How does water availability affect the rate of transpiration?

Answer 40

More water can replace lost water, if low supply stomata close and leaves wilt - more water, increased transpiration