chapter 9- transport in plants

Question 1

what is a dicotyledonous plant

Answer 1

a plant that forms 2 seed leaves

Question 2

what is a monocotyledonous plant

Answer 2

a plant which forms 1 seed leaf

Question 3

Why do plants require specialised transport systems?

(4 things)

Answer 3

To ensure nutrients reach all tissues.
To allow diffusion across large distances
To overcome the low surface area to volume ratio
To meet the high metabolic demand

Question 4

what is a vascular bundle/vascular tissue made up of

Answer 4

xylem and phloem

Question 5

How are the vascular tissues arranged in the stem and the root of dicotyledonous plants?

Answer 5

in a circle around the edge of the stem

he vascular tissues are arranged in a bundle in the centre of the root.

Question 6

what are stomata

Answer 6

The stomata are pores, usually found in the lower epidermis of a leaf, through which gases such as oxygen and carbon dioxide diffuse.

Question 7

describe what happens during the day and night in terms of stomata, photosynthesis and respiration

Answer 7

day: stomata are open, P and R occur
night: stomata closed, only R occurs

Question 8

what are some characteristics of xylem

Answer 8

no end walls
transports h2o and dissolved mineral ions
transports just up
contains dead cells (lignin)
passive process

Question 9

what is the structure of the xylem (3)

Answer 9

dead
hollow
elongated tube

Question 10

2 main functions of the xylem tissue

Answer 10

to transport water and minerals from the roots to the rest of the plant
to provide strength

Question 11

the xylem contains cells joined end to end with no end wall, how does this feature contrbute to effection transport of water

Answer 11

it forms one continuous/unbroken tube which is essential for the movement of water by cohesion tension

Question 12

Describe the cohesion-tension theory of water transport in the xylem. (3 things)

Answer 12

First, the loss of water by transpiration decreases the water potential in mesophyll cells.
This pulls water up the xylem, which puts it under tension.
Inside the column, water molecules adhere to the walls, and they’re stuck together by hydrogen bonds.

Question 13

xylem contains dead cells, how does this contribute to the effective transport of water

Answer 13

cells do not use ATP to move the water, the movement of water would be slowed by the cell surface membrane and cytoplasm of a living cell

Question 14

xylem has thick walls containing…

Answer 14

lignin

Question 15

how does lignin in the thick walls of xylem contribute to effective transport of water

Answer 15

it helps strengthen the xylem and prevent collapse

Question 16

characteristics of phloem

Answer 16

transports up and down
transports sucrose and AA by translocation
sieve and companion cells
active process

Question 17

what is the name of the main transport vessels in the phloem

Answer 17

sieve tube elements

Question 18

what is the structure of phloem sieve tube elements

Answer 18

many cells joined end to end to form a hollow tube separated by sieve plates

Question 19

what cells are linked to the sieve tube elements and provide support with metabolic activity y

Answer 19

phloem companion cells

Question 20

products of photosynthesis transported in the phloem such as sucrose and amino acids are called

Answer 20

assimilates

Question 24

what materials do plants need to exchange and transport

Answer 24

carbon dioxide
oxygen
water
organic nutrients eg sucrose
inorganic ions (N, P, K)

Question 25

as well as the transport of substances the vascular bundle has

Answer 25

structural support purposes

Question 26

adaptations that a leaf might have to conserve water

Answer 26

THICK waxy cuticle few stomata sunken stomata hairs leaf curled dense spongy mesophyll closure of stomata during the day small SA

Question 27

how are the vascular tissues arranged in the roots of dicotyledonous plants

Answer 27

in a central bundle

Question 28

how are the vascular tissues arranged in the leaves of dicotyledonous plants

Answer 28

in a midrib with many branching veins

Question 29

transport tissues are arranged together in the stems leaves and toots of dicotyledonous plants in

Answer 29

vascular bundles

Question 30

how are the vascular tissues arranged in the stem of dicotyledonous plants

Answer 30

in separate bundles in a ring around the edge of a stem

Question 31

what are plasmodesmata

Answer 31

small channels/pores connecting the cytoplasm of adjacent plant cells

Question 32

if a cell has been plasmolysed what does this mean and what conditions usually forces this to occur

Answer 32

the cell membrane and shrunk away from the cell wall, happens in low external water potential, when water moved out of the cell

Question 33

if the water potential inside the cell is low will water move in or out of the cell

Answer 33

in

Question 34

low intracellular water potenial means the salt concentration is

Answer 34

high

Question 35

high intracellular water potential means that the salt concentration is

Answer 35

low

Question 36

are root hair cells visible to the naked eye

Answer 36

yes they are 200-250micometres in size

Question 37

how is water and minerals contained in soil

Answer 37

in small air spaces in the soil

Question 38

comment on the concentration of solutes in soil and plant and what causes osmosis of water into the plant

Answer 38

osmosis occurs because there is a higher concentration of solutes in the plant than inside the soil

Question 39

what are the three water movement pathways

Answer 39

symplast vacuolar apoplast

Question 40

what is the purpose of water movement pathways

Answer 40

they enable the plant to get the water in as fast as possible

Question 41

which water movement pathways is the slowest

Answer 41

vacuolar

Question 42

which water movement pathways is the fastest

Answer 42

apoplast

Question 43

what is the symplast water movement pathway

Answer 43

water moves through the living spaces of the cell - cytoplasm, it uses plasmodesmata to move across adjacent cells water uses plasmodesmata to move across adjacent cells through the cytoplasm

Question 44

what is the vacuolar water movement pathway

Answer 44

same as symplast but the water moves through the cell vacuoles as well. its the SLOWEST

Question 45

what is the apoplast water movement pathway

Answer 45

water moves through the cell wall and the intracellular spaces. cohesive and tension forces act on the cell walls and pull that water up the plant. water moves through the cellulose fibres in the cell walls of connecting cells

Question 46

what is the casparian strip

Answer 46

impermeable layer of suberin therefore all water in the apoplast pathway is forced into the symplast pathway

Question 47

what is transpiration

Answer 47

Transpiration is the evaporation of water through stomata down a water potential gradient.

Question 48

how does wind affect the rate of transpiration

Answer 48

increase in wind=increase in rot more water evaporates from spongy mesophyll cells and diffuses out of the stomata. creating a lower water potential inside the mesophyll cells water is pulled up xylem=tension=cohesion=forms water column decrease in water vapour and increase in the water potential gradient

Question 49

what is a hydrophyte

Answer 49

plants adapted to grow partly under water or in wet habitats

Question 50

List three adaptations of hydrophytes to survive in wet habitats.

Answer 50

no waxy cuticle increased number of stomata wide flat leaves to capture light

Question 51

which is an adaptation of a hydrophyte a) a thick waxy cuticle b) many stomata on the upper surfaces of the leaves

Answer 51

b

Question 52

what increases the rate of transpiration

Answer 52

increase in temp increase in wind decrease in humidity

Question 53

how does an increase in temperature increase rate of transpiration

Answer 53

increases the KE and so increases evaporation

Question 54

how does an increase in light increase rate of transpiraiton

Answer 54

increases the open stomata

Question 55

what is a xerophyte

Answer 55

plants that have adapted to survive in habitats where water supply is limited

Question 56

List 4 adaptations shown by the leaves of xerophytes which help reduce water loss.

Answer 56

Thick waxy cuticle Stomata in sunken pits Leaves which are curled Leaves covered in hairs

Question 57

what does a potometer measure the rate of

Answer 57

A potometer directly measures the rate of water uptake. This is proportional to the rate of transpiration.

Question 58

what are the limitations of using a potometer to measure transpiration?

Answer 58

It assumes that all of the plant’s water will be transpired The plant’s roots are removed, This means the calculated rate doesn’t account for the rate of water uptake in the roots.

Question 59

first step of translocation: a carrier protein (not a co-transport protein) moves ... ............ this creates a

Answer 59

H+ ions from the cytoplasm of the companion cell to the cell wall, using active transport. This creates a concentration gradient, and the H+ ions are returned to the cytoplasm via a co-transport protein, which also transports sucrose.

Question 60

3rd step of translocation, what happens after H+ and sucrose are back inside the companion cell and what does this cause

Answer 60

sucrose diffuses into the sieve tube element (this transport is not active). This causes the water potential in the sieve tube element to decrease (adding solutes decreases the water potential).

Question 61

5th step of translocation, what happens after a wpg is created in the sieve tube element, and what does this cause

Answer 61

Water moves from the xylem into the sieve tube element by osmosis This causes the hydrostatic pressure in the sieve tube element to increase.

Question 62

what happens at the sink cell in translocation

Answer 62

At the sink cell, sucrose moving out of the sieve tube element decreases the hydrostatic pressure here. As a result, the sucrose solution moves down the hydrostatic pressure gradient (since the sucrose solution is a fluid, it exerts hydrostatic pressure). Finally, sucrose moves into the sink cell.

Question 63

what is the source cell and sink cell in translocation

Answer 63

source: leaf cell sink: root cell

Question 64

near the source cells sucrose is loaded into the sieve tube element which does what do the wp and hydrostatic pressure

Answer 64

which decreases the water potential (Adding solutes like sucrose will decrease the water potential) and increases the hydrostatic pressure (Hydrostatic pressure is increased as water moves in from the adjacent xylem, down the water potential gradient by osmosis.)

Question 65

in between source cells and sink cells the sucrose solution moves up/down a what..

Answer 65

down the hydrostatic pressure gradient. The sucrose solution exerts a hydrostatic pressure gradient to drive mass flow

Question 66

"Sieve tube elements of the phloem are connected by sieve plates" does this support or undermine the mass flow hypothesis, and why

Answer 66

undermine sieve plates, although they have holes, hinder mass flow more than if there were no sieve plates at all: the phloem should have maximum space to make translocation as efficient as possible. Therefore, the presence of sieve plates does not support the mass flow hypothesis. Additionally, the idea that sieve plates may stop the phloem bursting under pressure has not been confirmed experimentally.

Question 67

"The sap found in mature leaves of a celery has a higher sucrose concentration than sap found in its stalk." does this support or undermine the mass flow hypothesis, and why

Answer 67

supports In this example, the mature leaves are the source and the stalk is the sink. A high concentration of sucrose near the source and a lower concentration of sucrose near the sink would suggest that the sieve tube elements in these locations have different water potentials. Therefore, water will move into the sieve tube element near the source cells by osmosis and out of the sieve tube element near the sink cells. This supports the idea that water moves by osmosis during translocation, and therefore supports the mass flow hypothesis.

Question 68

"A part of a potato plant was observed under a microscope. It was found that the companion cells had a lot of mitochondria." does this support or undermine the mass flow hypothesis, and why

Answer 68

supports Mitochondria are responsible for generating ATP. The fact that companion cells have a lot of mitochondria suggests that ATP is needed. ATP is required as part of the mass flow hypothesis. The presence of many mitochondria therefore supports the mass flow hypothesis.

Question 69

"It was observed that, in sap, salts travel at a different speed to amino acids" does this support or undermine the mass flow hypothesis, and why

Answer 69

undermines If all substances are transported under pressure, they would all be expected to travel at the same speed through the phloem. Therefore, since salts and amino acids travel at different speeds, this undermines the mass flow hypothesis.