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biology > 3.1.3: transport in plants > Flashcards

3.1.3: transport in plants Flashcards

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1
Q

how do gases diffuse in and out of leaves?

A

via the stomata

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2
Q

what does the xylem transport?

A

water and mineral ions

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3
Q

what does the phloem transport?

A

sugars

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4
Q

what is the transpiration stream?

A

the movement of water up a plant

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5
Q

how do mineral ions move into the root hair cells?

A

a combination of facilitated diffusion and active transport

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6
Q

how are root hair cells adapted for its function?

A

have a large surface area and have very thin walls

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7
Q

what is the apoplastic pathway?

A

water moves from cell to cell through the cellulose walls

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8
Q

what is the symplastic pathway?

A

water moves from cell to cell through the cytoplasm, then via connections from one cytoplasm to another

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9
Q

what is the casparian strip?

A

a waxy strip in the cell wall (suberin)

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10
Q

can water pass through the casparian strip?

A

no because it’s waterproof

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11
Q

what does the casparian strip do to the flow of water and what does this allow?

A

slows it down, and gives the plant some control over which mineral ions pass through

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12
Q

what is xylem tissue made from?

A

many xylem vessel elements

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13
Q

what substances are there in the xylem wall?

A

cellulose and lignin

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14
Q

how is the xylem adapted for transporting water?

A

has lignin in the walls, which is strong and waterproof and has tiny holes called pits which allow water to move sideways into neighboring vessels if there are blockages

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15
Q

what mechanisms are at work when water moves up the stem?

A

root pressure, cohesion forces and adhesion forces

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16
Q

what is mass flow?

A

a whole column of water moving up together

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17
Q

what is root pressure?

A

the active pumping of minerals into the xylem by root cells that produces a movement of water into the xylem by osmosis

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18
Q

what is cohesion tension theory?

A

due to water being polar, they can attract each other and form hydrogen bonds. this means that as they move up the xylem, they will attract and pull up more water, due to cohesion forces and hydrogen bonding

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19
Q

what are adhesion forces?

A

where water molecules are attracted to different molecules and hydrogen bonds form between molecules, causing it to crawl up the xylem wall

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20
Q

what is the capillary affect?

A

more water molecules are in contact with the xylem walls because it is so narrow, increasing the adhesion forces

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21
Q

what drives the movement of water up the plant?

A

the evaporation of vapour from the stomata and leaves

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22
Q

is water transport an active or passive process and why?

A

passive because it doesn’t require atp at all

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23
Q

how does transpiration occur?

A

water from the xylem vessels enters the mesophyll cells, making the spaces saturated with water vapour. these air spaces are close to the stomata so the vapour evaporates out, by diffusion, down a water potential gradient

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24
Q

how have plants adapted to minimize water vapour losses during transpiration?

A

a waxy cuticle, stomata being on the underside of leaves, stomatas being closed at night and plants losing their leaves in winter

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25
Q

where are the vascular bundles located in stems and why?

A

around the edge to give strength and support

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26
Q

where are the vascular bundles located in roots and why?

A

in the middle to help it withstand the tugging strains while in windy conditions

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27
Q

where are the vascular bundles located in leaves and why?

A

in the midrib of a dicot leaf to support the structure of the leaf

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28
Q

what does turgor pressure do?

A

provides a hydrostatic skeleton to support the stems and leaves

29
Q

what does evaporation do to a plant?

A

helps to keep is cool

30
Q

what happens to the stomata during the day and why?

A

mostly open, which allows free exchange of oxygen and carbon dioxide. water vapour is lost via diffusion

31
Q

what happens to the stomata during the night?

A

mostly closed to prevent excessive loss of water vapour. the demand for carbon dioxide is low but oxygen is still required for respiration

32
Q

what are the 2 pieces of evidence for the cohesion tension theory?

A

changes in tree diameter and breaking a xylem vessel

33
Q

how does the changes in a tree diameter prove cohesion tension theory?

A

when transpiration is at its highest during the day, the tension in xylem vessels is at its highest too so the tree shrinks in diameter and vice versa

34
Q

how does breaking a xylem vessel prove cohesion tension theory?

A

air is pulled in to the xylem rather than water leaking out, meaning plant can no longer move water as a continuous stream

35
Q

what are the factors that affect transpiration?

A

light, humidity, temperature, air movement and soil-water availability

36
Q

how does light intensity affect transpiration?

A

increasing the light intensity gives an increasing number of open stomatas, meaning a higher rate of transpiration

37
Q

how does humidity affect transpiration?

A

very high relative humidity will lower the rate of transpiration because of a reduced water potential gradient

38
Q

how does temperature affect transpiration?

A

increased temperature also increases the kinetic energy of the water molecules, so it increases the rate of evaporation.

39
Q

how does air movement affect transpiration?

A

increased wind means when water is diffused out, the water potential concentration increases therefore increases transpiration

40
Q

how does soil availability affect transpiration?

A

if the plant is very dry, it will be under water stress and the rate of transpiration will be reduced

41
Q

what must plants living on land be adapted to do?

A

reduce water loss and to replace water that is lost

42
Q

what are xerophytes?

A

plants adapted to live in dry habitats, where there is little access to water

43
Q

what is the importance of a thick, waxy cuticle in xerophytes?

A

helps minimise water loss and and in most plants, up to 10% of water loss by transpiration is actually through the cuticle

44
Q

what is the importance of a sunken stomata in xerophytes?

A

found in pits, producing a of still humid air that reduces the water potential gradient therefore reducing transpiration

45
Q

what is the importance of a reduced number of stomatas in xerophytes?

A

reduce water loss by transpiration and also reduces their gas exchange capabilities

46
Q

what is the importance of a reduced number of leaves in xerophytes?

A

have a small surface area to volume ratio, reducing water loss by transpiration

47
Q

what is the importance of hairy leaves in xerophytes?

A

creates a microclimate of still, humid air, reducing the water potential gradient and minimising water lost by transpiration

48
Q

what is the importance of curled leaves in xerophytes?

A

confines the stomata within a microenvironment of still, humid air to reduce diffusion of water vapour from the stomata

49
Q

what is the importance of succulents in xerophytes?

A

they store water in specialised tissues and then are used in drought

50
Q

what is the importance of leaf loss in xerophytes?

A

prevent water loss through their leaves by losing leaves when water isn’t available

51
Q

what is the importance of root adaptations in xerophytes?

A

long, tap roots grow deeper into the ground to access water that is below the surface, to get as much from the soil as possible. some have shallow roots with a large surface area to absorb rainwater

52
Q

what is the importance of avoiding the problems in xerophytes?

A

adapted to cope by avoiding situations entirely. plants may lose their leaves and become dormant. others may survive as storage organs

53
Q

what is the importance of no waxy cuticle in hydrophytes?

A

don’t need to conserve water because their is plenty available

54
Q

what is the importance of always open stomatas on upper surfaces in hydrophytes?

A

maximises gas exchange. floating plants have them on upper surface so they are in contact with air

55
Q

what is the importance of a reduced structure to the plant in hydrophytes?

A

water supports the leaves and flowers so there is no need for structure

56
Q

what is the importance of wide, flat leaves in hydrophytes?

A

to capture as much sunlight as possible for photosynthesis

57
Q

what is the importance of small roots in hydrophytes?

A

water can diffuse directly into the stem and leaf tissue so there is a less need in uptake by roots

58
Q

what is the importance of a large surface area of stem and roots under water in hydrophytes?

A

maximises area for photosynthesis and for oxygen to diffuse into submerged plants

59
Q

what is the importance of air sacs in hydrophytes?

A

enable leaves to float to the surface of the water for photosyntheis

60
Q

what is the importance of aerenchyma in hydrophytes?

A

specialised packing tissue in leaves, stems and roots make them more buoyant and form a low resistance internal pathways for movement of substances

61
Q

is cacti and example of a xerophyte or a hydrophyte?

A

xerophyte

62
Q

how are cacti adapted?

A
  • thick, waxy cuticle to reduce water loss
  • spines instead of leaves to reduce the surface area for water to be lost
  • close their stomatas at the hottest times of day when transpiration rates are high to reduce water lost
63
Q

is marram grass a hydrophyte or a xerophyte?

A

xerophyte

64
Q

where is marram grass found?

A

in sand dunes

65
Q

why are sand dunes such harsh conditions for plant growth?

A

the gap between rains may be months or even years so water is rarely available

66
Q

how is marram grass adapted?

A
  • sunk in pits so they are sheltered from wind, slowing down transpiration
  • layers of hair on epidermis which traps moist air around the stomata and reducing the water potential gradient
  • roll their leaves to reduce the exposed surface area for losing water and protects stomata from wind
  • thick, waxy layer to reduce loss of water by evaporation
67
Q

what are hydrophytes?

A

plants that live in water, partially submerged

68
Q

what is aerenchyma tissue do?

A

allows oxygen to diffuse through the plant to all respiring cells, it is also a route for waste gases to get out

69
Q

how do hydrophytes transpire?

A

contain specialised structures at the tips of their leaves called hydathodes, which release water droplets which may evaporate from the surface

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