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Biology mark scheme > Transport in plants > Flashcards

Transport in plants Flashcards

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1
Q

State three features of a xerophyte which indicate that it live in a dry environment and explain (6)

A
  • has a reduced surface area - less area which water can be lost
  • thick cuticle - waterproofing
  • rolled leaves - trapping water
  • hairs - trapping water vapoue
  • stomata - trapping water vapour
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2
Q

Explain the role of the phloem (1)

A
  • transports carbonhydrates / sugars / products of photosynthesis / sucrose / amino acids
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3
Q

Explain the role of the xylem (1)

A

Transports water and dissolved mineral ions

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4
Q

Explain how the enedodermis carries out its function in the uptake of water and minerals in the plant (4)

A
  • waterproof casaprian sstrip made of suberin whch is hydrophobic
  • blocks apoplast pathway
  • active transport of minerals by endodermis cells
  • into symplast pathway
  • active transport of minerals into pericycle
  • water follows via osmosis
  • water and minerals move into xylem vessles
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5
Q

Explain what is meant by transpiration. Describe the factors affecting transpiration. (7) Describe how you could use a potometer to investigate one of the factors (3)

A

Transpiration
* transpiration is the evaporation of water vapour from inside the leaves of the plant
* through stomata
* down a water potential gradient
* high temperature increases the rate of transpiration
* increased kinetic energy of water molecules
* increases air movement increases the rate of temperature increasing the diffusion gradient
* high humidity decreases rate of transpiraation decreasing the diffusion gradient
* high light intersity increases rate of transpiration
* because of stomatal opening
* sset up under water make sure air cannot get in
* volumer of water taken up per unit of time
* control of wind speed by using a fan
* to give a close approximation of transpiration rate

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6
Q

State the bame of the process by which plants lose water from their leaves (1)

A

Transpiration

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7
Q

Describe one theory that would explain how w\ter moves up the stem of the leafy shoot (3)

A
  • water lost by leaves via transpiration
  • causing tension on water molecules
  • cohesive forces between water molecules
  • adhesive forces between water molecules and and xylem
  • water molecules pulled up into xylem
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8
Q

describe the rolee of potassium ions in guard cells closing the stomata (1)

A

pumpers out of guard cells

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9
Q

describe the rolee of water potential of cells in guard cells closing the stomata (1)

A

increases water potential so water moves out

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10
Q

describe the role of unevenly thickened cell walls in guard cells closing the stomata (1)

A

decreased water so decreases volyne of cell causing walls to move together

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11
Q

How dos the effect of increased humidity effect rate of transpiration (2)

A
  • decreases effect on rate of water loss
  • reduces the diffusion gradient so water potential gradient between iside and outside of leaf
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12
Q

Describe the uptake of water by plants form the soil into xylem (7) explain the role of ions in this process (3)

A
  • water absorbed by root hair cells
  • water can be absorbed into cell walls
  • moves across cortex via apoplast route
  • can also move across plasma membrane into cytoplasm bia omossis
  • water moves from the cytoplasm of one cell to the next via plasmodesmata
  • cells the ymplast route
  • water can also move through cytoplasm and vacoules via vacuoular route
  • casparian strip in endodermal walls
  • made of suberin
  • stops apoplast route water forced into symplast route
  • ions absorbed into root hair cells by active transport
  • ions lowering water potential in root hair cells
  • at endodermic ions absorbed into cytoplasm by active transport
  • ions travel through pericylce into xylem
  • lowers water potential in the xylm
  • lower water potential in root hair cells or xylem increasing osomotic gradient between soil and cell contents
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13
Q

State two practical measures which should be taken when setting up the apparatus to ensure the potometer functions correctly give reasons fro your answers (4)

A
  • shoot cut under water to prevent air enertering
  • shoort with large number of leaves ensure measurable rate of transpiration
  • ensure leves are dry reduces rate of transpiration
  • leave time for apparatus to settle down allow plant to equilibriate
  • seal joint with vaseline to prevent air entering apparature
  • ensure bubble set at approprate position to enable reading being taken
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14
Q

Name the original source of energy that moves wwater through a plant (1)

A

Sunlight

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15
Q

Explain how water moves up the xylem (2)

A
  • molecules of water moving together because of cohesion of molecules
  • adhesion to walls of xylem
  • root pressure pushes water upwards
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16
Q

Explain the difference of diagrams of cross section of roots and stems

A
  • xylem is at centre in root
  • no vascualr bundles in stem
  • endodermis not visible in root
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17
Q

tissue external to xylem is removed by ringing why did an accumulation of sucrose occur (3)

A
  • sucrose is produced in leaf
  • sucrose travels in phloem
  • phlowm is removed by rining
  • sucrose cannot flow to roots
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18
Q

Name the other type of organic molecules likely to accumulate with sucrose in ringing (1)

A

amino acids/ hormones / florigen

19
Q

If growing points of shoots of plants are removed from ringing there is a greater accumulaion of sucrose why (2)

A
  • sucrose used for cell wall formation
  • less sucrose used by sinls as they have been removed
  • therefore more will pass down stem
20
Q

Explain fully the likely effect of the removal of the ring of tissue in the concentration of sucrose below the ring (3)

A
  • sucrose not replaced from above
  • so concentration decreases
  • as movement towards root continues
  • and sucrose used in respiration / sotrage / converted to starch / growth / active transport
21
Q

State the function of sieve tube cell (1)

A
  • translocation of sucrose from source to sink
22
Q

State the function of companion cells (1)

A

Carry out metabolism to suppy sieve cells with energy contains lots of mitochondria

23
Q

Name two other pathways by which water moves across the roote cortex except the vacoular pathway (4)

A
  • Apoplast
  • via cell walls
  • symplast
  • via cytoplasm / plasmodesmata
24
Q

How does the casparian strip affect the route of water takes into stele (1)

A
  • Makes the water pass through (symplast) prevents it going through the apoplast
25
Q

Give one benefit of tranpiration to a plant (1)

A
  • cooling effect
  • upply movement of minetal ions
  • maintains transpiration
  • required for photsynthesis
26
Q

Suggest why the end of the shoort should be cut under water before inserted into the potometer (2)

A
  • prevent entry of air into xylem preenting formation of air bubble
  • whcih would break transpiration stream
27
Q

State what measurementsw ould have bee made in order to determine the rate of transpiration (2)

A
  • diameter of capilalry tuber
  • distance travelle by bubble
  • time taken
28
Q

Explain how sunken stoma is able to reduce transpiration (3)

A
  • High humidity in air chamber because water vapoyr removed by wind / water vapour trapped
  • this reduces the water potential gradient
  • between the inside of the leaf and air chamber/ inside and outside of the stoma
29
Q

Describe end explain two other adaptations whcih reduce the rate of transpiration in plants that live in very dry condition (2)

A
  • rolle leaves reduce surface areaexposed to the environment
  • reduced number of stomata less openings for water to be lost through
  • hairs on leaves increase humidity reducing water potential gradient
  • thick cuticle reduce evaporation from ssurface of leaf
30
Q

Bame two other types of cells except companion cells and sieve tube element forund in phloem (2)

A
  • pernchyma
  • phloem fibres
31
Q

Explain how two features of the sieve tube element enable the phloem to carry out its functio (4)

A
  • sieve plates - permits biderectional flow
  • few organelles - no obsstruction to flow of solutes
  • plasmodesmata - allows transport of molecules from companion cell to sieve tube elements
32
Q

Suggest why the prescence of large numbers of mitochondira in the companion cells dows no support the mass flow theory (3)

A
  • mass flow is a passive process
  • from hgih to low concentration
  • ATP not required since a passive process
33
Q

Describe the similarities and differences in the structure and functioning of arteries and xylem vessles (10)

A
  • both tubular
  • both have movement by mas flow
  • both movement along pressure gradients
  • both movement in one direction only
  • artery transports bloow xylem water
  • arteries living xylem dead
  • movement of liquid pulastile in arteries smooth in xylem
  • pressure generated by heart in arteries no pump for xylem
  • xylem contains lignin
  • xylem has support dunction
  • adhesiv forces in xylem
  • arteries have muslce and elastic tiue
  • arteries recoil
  • smooth entoehrlium of artery reducing friction
  • artery walls composed of layers
  • remembers to use whereas
34
Q

State the term used to describe plants adapted for dry conditions (1)

A

xerophytes

35
Q

Name one source and one sink in plants (1)

A
  • source - lead and sink - shoot tip or root
36
Q

Describe and explain the strucutral adaptations hwon by a water lily and marram grass that enable them to survive in environments that differ in terms of water availability (10)

A

Water lilly
* it is a hydrophyte
* access to water all year round
* roots submerged in mude at bottom of a pond and floating leaves on surface
* there are large air spaces present in leaves whcih allows them to float on the surface allowing oxygen to diffurse to roots for respiration
* xylem tissue poorly developed as water provides support
* stomata are found on upper epidermis of leaves to allow gas exchange with the air
* they have a thin cuticle as water loss iss not a problem
Marram grass
* xerophyte
* lives in habitats with low water availability
* thick cuticle to reduce evaporation as waterproofing
* stomatal pores on upper epidermis
* rolled leaves reduce transpiration as trap water vapour
* sunken stomata in pits
* hair surround stomata trap water vapour
* mainitaining humid air around stomata reducing water potential gradient

37
Q

Outline a method by which the density of stomata coul dhave been determines (3)

A
  • coat surface of leaf with clear nail varnish
  • examine using light microscope
  • count number of stomata in field of view
38
Q

Why is it imporatnt that no air bubbles enter the potometer (1)

A
  • block the xylem
39
Q

Explain why light intensity and temperature are controlled in a potometer investigation

A
  • increase inn temperature increase in kinetic energy
  • increase in light intensity increases tomatal oopening
  • increasing evaporation of water vapour
40
Q

Why is less water vapour lose through stomata in xerophytes (3)

A
  • sunken stomata cuase water vapour build up in pits
  • reduced diffusion gradient
  • rate of transpiration reduced
  • moving air can easily disrupt diffusion as blow away water vapour
41
Q

Suggest why it is difficult to calculate stomatal density in xerophytes (1)

A
  • Stomat sunken in pits so will nto shown up in impression
42
Q

Explain why leaves where removed above region to be invesitgated in ringing experiment (2)

A
  • reduces photsynthesis
  • reducing sugar production above experimental region
43
Q

State two variables which should have been controlled in rinign experiment (1)

A
  • light intensity
  • wavelength species
  • temperature
  • surface area of leabes
  • humidity
  • air movement
44
Q

With reference to the role of the caspariant trip explain how cyanide would result in reduction of root pressure (3)

A
  • stopes apoplast pathway
  • movement of ions into xylem requires active transport
  • Cyanise is a repisratory inhibitor preventing ATP synthesis
  • lower water potential gradient reducing root pressure

Biology mark scheme (9 decks)

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