exchange and transport

Question 1

what tissue do water and soluble minerals travel up/down in a plant?

Answer 1

xylem tissue

Question 2

what tissue do sugars travel up/down in a plant?

Answer 2

phloem tissue

Question 3

where are the xylem and phloem found?

Answer 3

in the vascular bundles

Question 4

what does the arrangement of the phloem and xylem provide?

Answer 4

strength to withstand the pulling forces that the roots are exposed to

Question 5

what is the endodermis?

Answer 5

a special sheath of cells, role is to get water from the xylem vessels

Question 6

name one xylem adaptation (1)

Answer 6

narrow tubes, so water column doesn’t break easily and capillary action can be effective

Question 7

name one xylem adaptation (2)

Answer 7

pits in the lignified walls allow water to move sideways from one vessel to another

Question 8

name one xylem adaptation (3)

Answer 8

lignin in spiral patterns, allows the xylem to stretch and bend as the plant grows. Also it strengthens the walls and prevents them from collapsing

Question 9

name one xylem adaptation (4)

Answer 9

made of dead cells that form a continuous column, hence no cell contents, nucleus or cytoplasm, to impede the flow of water

Question 10

what does phloem consist of?

Answer 10

sieve tube elements and companion cells

Question 11

what are sieve tube elements?

Answer 11

they contain very little cytoplasm and no nucleus. they’re lined up end-to-end to form a sieve tube, to transport sugars (sucrose). the sugar is dissolved in water to from sap.

Question 12

the sieve tubes contain sieve plates, what do they allow/contain?

Answer 12

they contain many pores to allow the sap to flow

Question 13

what do the companion cells have?

Answer 13

a large amount of mitochondria, to produce the atp needed for the active process

Question 14

what do the companion cells carry out?

Answer 14

the metabolic process needed by the sieve tube elements

Question 15

the cytoplasm of the sieve tube elements and companion cells are linked through many…

Answer 15

plasmodesmata

Question 16

what do the gaps in the cell walls of companion cells allow?

Answer 16

communication and flow of materials between the cells

Question 17

what is transpiration?

Answer 17

the loss of water vapour from the aerial parts of the plant

Question 18

what three processes does transpiration involve?

Answer 18

1) osmosis: from the xylem to the mesophyll cells
2) evaporation: from the surface of the mesophyll cells into the intercellular spaces
3) diffusion: of water vapour down a water vapour potential gradient out of the stomata

Question 19

the movement of water up the stem is called the…

Answer 19

transpiration stream

Question 20

how is the transpiration stream useful?

Answer 20

1) it enables leaves to acquire water for photosynthesis
2) it keeps cells turgid
3) evaporation of water can help keep plant cool
4) it enables cells to acquire water for growth and elongation

Question 21

how is the rate of transpiration measured?

Answer 21

using a potometer

Question 22

what’s a factor that effects the rate of transpiration? (1)

Answer 22

the amount of leaves.

the more leaves the larger the surface area over which water vapour can be lost

Question 23

what’s a factor that effects the rate of transpiration? (2)

Answer 23

presence of waxy cuticle.

reduces evaporation from the leaf surface

Question 24

what’s a factor that effects the rate of transpiration? (3)

Answer 24

the number of stomata.

the more stomata, the faster the rate of water vapour loss.

Question 25

what’s a factor that effects the rate of transpiration? (4)

Answer 25

air movement/wind.

wind will take away water vapour, maintaining a high water vapour potential gradient.

Question 26

what are xerophytes?

Answer 26

plants that are well adapted to living in very dry/arid conditions

Question 27

what are the xerophytes adaptations to reduce water loss? (1)

Answer 27

pits:

containing stomata at their base which also trap air

Question 28

what are the xerophytes adaptations to reduce water loss? (2)

Answer 28

hairs:
on the surface of leaves which trap a layer of air which can be saturated with moisture to reduce the water vapour potential

Question 29

what are the xerophytes adaptations to reduce water loss? (3)

Answer 29

densely packed spongy mesophyll:

reduces cell SA exposed to air inside the leaves so less water will evaporate into the air spaces

Question 30

reduces cell SA exposed to air inside the leaves so less water will evaporate into the air spaces (4)

Answer 30

closing the stomata:

when water availability is low, reducing water loss and the need to take up water.

Question 31

describe the apoplast pathway

Answer 31

the cellulose cell wall has many water-filled spaces between the cellulose molecules. water can move through these spaces and between the cells, and as the water doesn’t pass through any plasma membranes, it can carry dissolved mineral ions and salts

Question 32

describe the symplast pathway

Answer 32

water enters the cytoplasm through the plasma membrane, and pass form one cell to the next through the plasmodesmata. once inside the cytoplasm, water can move through the continuous cytoplasm from cell to cell

Question 33

what is the function of the root hair cells in the roots?

Answer 33

they use atp to absorb minerals via active transport

Question 34

what do the minerals absorbed by the root hair cells do?

Answer 34

reduce the water potential of the cell cytoplasm, making it lower than the soil. the result is that water is taken up across the plasma membrane by osmosis, as molecules move down the water potential gradient

Question 35

what is the movement of water across the root?

Answer 35

the movement is driven by an active process that occurs at the endodermis

Question 36

what does the casparian strip consist of?

Answer 36

special cells that have a waterproof strip in some of their cells.

Question 37

what’s the function of the casparian strip?

Answer 37

it blocks the apoplast pathway, forcing water into the symplast pathway

Question 38

what is ensured when the apoplast pathway is blocked?

Answer 38

this ensures that water and dissolved nitrates have to pass into the cell cytoplasm through the cell membrane