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Biology🧬🪼 > 3.3)Transport in plants > Flashcards

3.3)Transport in plants Flashcards

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1
Q

why do plants need a specialised transport system?

A

-larger plants have a smaller sa:vol ratio
-transport water and minerals from roots to leaves
-transport sugars from leaves to rest of the plant

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2
Q

why is diffusion alone not efficient for plants?

A

-not very active = respiration rate is low = oxygen can diffuse
BUT
-water cannot be absorbed by air (by diffusion)
-sugars can’t be absorbed by soil (by diffusion)

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3
Q

what are the 2 types of vascular tissue and what do they carry?

A

xylem tissue = water and soluble mineral ions

phloem tissue = assimilates (e.g. sucrose sugar)

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4
Q

what isn’t carried in plant vascular tissue that is in animals?

A

respiratory gases

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5
Q

what are dicotyledonous plants?

A

plants that have 2 seed leaves and a branching pattern of veins

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6
Q

what tissue do vascular bundles contain?

A

-collenchyma & sclerenchyma=provide support and strength to the plant
-xylem = water
-phloem = assimilates

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7
Q

where is the vascular bundle found in a young root and what shape is it?

A

-core of young root
-x shaped = arrangement provides strength to withstand pulling forces that roots are exposed to

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8
Q

what surrounds the vascular bundle (young root)?

A

-sheath of endodermis cells = allows water to enter xylem

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9
Q

what is the significance of pericycle cells and where are they found (young root)?

A

-inside the endodermis
-able to divide and differentiate into any type of cell = grow and repair damaged tissue

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10
Q

where are the vascular bundles found in the stem?

A

outer edge of the stem

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11
Q

how do the vascular bundles differ in woody plants and non-woody plants (in the stem)?

A

non-woody = bundles are separate and discrete

woody = separate in young stems but continuous rings in older stems

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12
Q

what is the significance of the complete rings of vascular tissue under barks of trees?

A

the arrangement provides strength and flexibility to withstand bending forces exerted by wind onto stems nd branches

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13
Q

what is found between the xylem and phloem (in stems)?

A

layer of cambium (meristem cells) = divide to produce xylem and phloem cells

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14
Q

where are the vascular bundles found in the leaf?

A

form the midrib and veins of the leaf

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15
Q

what is the function of companion cells?

A

to load sucrose into the sieve tubes

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16
Q

what are sieve tube elements?

A

make up tubes in the phloem tissue

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17
Q

what are the 3 main structures of the xylem?

A

vessels = carry water nd dissolved minerals
fibres = support the plant
living parenchyma cells = act as packing tissue that separate nd support vessels

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18
Q

where is lignin found in the xylem nd what does it do?

A

-found in walls
-is waterproof = kills the cell = end walls nd cell contents decay

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19
Q

what are found in areas where lignification is incomplete in the xylem?

A

bordered pits = allow movement of water between adjacent vessels

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20
Q

how are xylem adapted to carry water nd mineral ions from roots to leaves?

A

-made from dead cells = form continuous columns from roots to leaves

-tubes are narrow = don’t break easily nd capillary action is effective

-bordered pits = water move sideways to adjacent vessels

-lignin deposited n spiral/annular/reticular patterns = xylem can stretch = stem/branch bends

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21
Q

why is the flow of water not impeded in the xylem?

A

-no cross walls
-no cell contents
-thick lignin layer prevents walls from collapsing

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22
Q

how do sieve tube elements help to carry assimilates up/down the phloem?

A

-lined up end to end to form sieve tubes
-no nucleus, little cytoplasm = lots of space for mass flow of assimilates
-sieve plate cross walls (at ends of tube) = assimilates travel through holes to next sieve tube element

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23
Q

what do companion cells have many of and what are they needed for?

A

-many mitochondria = ATP for active processes = load assimilates into sieve tubes

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24
Q

what are the 3 pathways taken by water?

A

Apoplast
Symplast
Vacuolar

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25
Q

describe the apoplast pathway

A

-water moves by osmosis
-through spaces between cell walls

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26
Q

describe the symplast pathway

A

-water enters cytoplasm through plasma membrane
-leaves through plasmodesmata to next cell

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27
Q

describe the vacuolar pathway

A

-water passes through cytoplasm nd vacuoles
-leaves through plasmodesmata to next cell

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28
Q

what is water potential?

A

-the tendency of water molecules to move from one place to another
-water moves DOWN water potential grad. (high—>low)

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29
Q

what is the water potential in the cytoplasm?

A

contains mineral ions nd sugars (solutes) = more (-)ive water potential that pure water

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30
Q

what happens when a plant cell is placed in pure water?

A

-water potential in pure water is 0
-water potential in cytoplasm is (-)ive
-water moves down water potential grad.
-water will move into the cell = turgid

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31
Q

what happens once the cell is full of water?

A

water inside the cell exerts P. on cell wall = P. potential build up = inflow of water reduced

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32
Q

what happens when a plant cell is placed in a salt solution?

A

-water potential in cytoplasm in (-)ive
-water potential n salt solution is more (–)ive!!
-water moves down water potential grad.
-water moves out of cell
= flaccid

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33
Q

what is plasmolysis?

A

when the plasma membrane loses contact with the cell wall due to water loss in cytoplasm nd vacuole

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34
Q

what is a potometer used for?

A

measure the rate of water uptake as a leafy stem respires

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35
Q

what is transpiration?

A

-the loss of water vapour from aerial parts (parts above soil) of plant
-mostly though stomata in leaves

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36
Q

why is transpiration limited on the surface of the leaf?

A

waxy cuticle

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37
Q

why does transpiration occur more during the day?

A

-stomata open to release water vapour
-stomata open mostly during day for gas exchange as there is sufficient sunlight for photosynthesis

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38
Q

describe the typical transpiration pathway

A

into leaf through xylem –> (osmosis) spongy mesophyll –> evaporates from spongy m. cell wall –> (diffusion) out of leaf through open stomata

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39
Q

what does transpiration trigger?

A

water lost through transpiration is replaced by transpiration stream = draws more water up the stem

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40
Q

why is transpiration important?

A

-transports useful minerals up plant
-maintains cell turgidity
-supplies water = growth, elongation nd photosynthesis
-supplies water = evaporates = cool plant (on hot day)

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41
Q

how does light intensity affect rate of transpiration (ROT)?

A

light = stomata open to allow gas exchange for photosynthesis = ROT inc.

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42
Q

how does temp affect ROT?

A

high temp = water molecules have more KE = more leave the stomata = ROT inc

high temp = decreases water vapour potential in air = more rapid diffusion ut of leaf

43
Q

how does humidity affect ROT?

A

higher humidity in the air = less steep water vapour potential grad. = ROT decreases

44
Q

how does wind affect ROT?

A

air moving outside of leaf = water vapour carried away = maintain steep water vapour potential grad. = high ROT

45
Q

how does water availability affect ROT?

A

little water in the soil = water lost by transpiration can’t be replaced = stomata close = ROT decreases

46
Q

what precautions are taken when using a potometer?

A

-vaseline around edges of apparatus to prevent air bubbles
-ensure shoot is healthy
-cut stem under water = prevent water entering xylem
-cut stem at angle = provide large SA in contact w water
-dry the leaves

47
Q

what is adhesion?

A

attraction between water molecules and walls of the xylem vessels (carbohydrate molecules)

48
Q

what is cohesion?

A

attraction between water molecules nd other water molecules

49
Q

what are terrestrial plants?

A

plants that live on land

50
Q

why is access to no water a problem for terrestrial plants?

A

-stomata remains open during the day for gas exchange (CO2 for photosynthesis)
-open stomata=water loss via transpiration

51
Q

what are terrestrial plants adapted for?

A

-reduce water loss
-replace water lost

52
Q

what are the structural and behavioural adaptations of terrestrial plants to reduce water loss?

A

-waxy cuticle= reduce water loss via evaporation in epidermis
-stomata under the leaf= reduce evaporation=not in direct sunlight
-stomata closed at night= no light for photosynthesis
-deciduous plants lose leaves in winter= ground frozen= less water available + temp too low for photosynthesis

53
Q

what are xerophytes?

A

plants that live in arid (dry) conditions

54
Q

what are some examples of xerophytes?

A

-cacti
-conifers
-marram grass

55
Q

cacti is a succulent, what does this mean?

A

store water in its stem

56
Q

what are some adaptations of cacti?

A

-ribbed/fluted stem= expand when water is available
-spines (instead of leaves)= reduce S.A= reduce water loss
-green stem= photosynthesis
-widespread roots= take up water when available

57
Q

what are some adaptation of other xerophytes?

A

-small leaf S.A
-sunken stomata
-stomatal hairs
-closing stomata (when water is low)
-rolled leaves
-extensive root systems
-reduced # of stomata
-thick waxy cuticle
-leaf loss

58
Q

how does a small leaf S.A affect water loss?

A

reduced S.A for evaporation

59
Q

how does a sunken stomata affect water loss?

A

maintain humid air around stomata=reduce water potential gradient

60
Q

how do stomatal hairs affect water loss?

A

maintain humid air around stomata=reduce water potential gradient=reduce evaporation

61
Q

how does closing the stomata when there is less availability of water affect water loss?

A

reduce water loss=reduce the need to uptake water

62
Q

how does rolled leaves affect water loss?

A

reduce the effect of wind=reduce water potential gradient=reduce evaporation

63
Q

how do extensive root systems affect water loss?

A

-maximise water uptake=increase chances of contact with water
-shallow + wide=absorb rainfall

64
Q

how does a reduce number of stomata affect water loss?

A

reduce the amount of places water can evaporate from

65
Q

how does a thick waxy cuticle affect water loss?

A

waterproof leaves and stem=reduce evaporation

66
Q

how does leaf loss affect water loss?

A

prevent water loss through the leaves

67
Q

what are hydrophytes?

A

plants that live in water
(submerged, surface or at the edge of bodies of water)

68
Q

why do hydrophytes need adaptations?

A

to help them cope with growing in water or permanently saturated soil

69
Q

what are some examples of hydrophytes?

A

-water lilies
-duckweed
-bulrushes

70
Q

why is it important for the leaves of hydrophytes to be kept in the sunlight?

A

receive enough sunlight for photosynthesis

71
Q

what is a problem for hydrophytes?

A

waterlogging= water unable to drain away

72
Q

what are the adaptations of hydrophytes?

A

-very thin or no waxy cuticle
-many + always open stomata
-reduced structure
-wide + flat leaves
-small roots
-large S.A of stem and roots
-air sacs

73
Q

why do hydrophytes have a thin or no waxy cuticle?

A

-do not need to conserve water
-water loss is not an issue

74
Q

why do hydrophytes have many always open stomatas?

A

-maximise gas exchange
-no risk of becoming turgid (always water available)
-guards cells are inactive
-plants with floating leaves=stomata on top of the leaf

75
Q

why do hydrophytes have a reduced structure?

A

the water support the leaves and the flowers

76
Q

why do hydrophytes have wide and flat leaves?

A

capture as much light as possible

77
Q

why do hydrophytes have small roots?

A

water can diffuse directly into the stem and leaf tissue= less need for roots to uptake

78
Q

why do hydrophytes have a large S.A of stems and roots?

A

-maximise area for oxygen to diffuse
-oxygen to diffuse

79
Q

why do hydrophytes have air sacs?

A

allow the leaves and flowers to float

80
Q

how do hydrophytes transpire?

A

-they cannot transpire= transpiration stream stops + mineral ions are not transported
-have specialised structures= HYDATHODES
-found at the tip or margins of the leaf
-release water droplets= evaporate from the leaf surface

81
Q

what do leaves of a plant produce large amounts of ?

A

glucose

82
Q

what is glucose used for in plants?

A

respiration

83
Q

when transporting glucose what is it transported into?

A

sucrose

84
Q

what happens when sucrose reaches the cell?

A

-converted back to glucose=respiration
-converted to starch=storage
-used to make AA + other essential compounds

85
Q

define translocation

A

transport of assimilates around a plant via the phloem

86
Q

what are assimilates?

A

substances made by the plant using substances absorbed by the environment

87
Q

what are some examples of assimilates?

A

-sugars
-AA

88
Q

where are the assimilates transported to?

A

in the phloem from the sources to the sink

89
Q

what is the source?

A

part of plant that loads assimilates into the sieve tubes

90
Q

what are the sinks?

A

part of plant that removes assimilates from the sieve tubes

91
Q

what are the main sources of assimilates?

A

-green leaves + stems
-storage organs
-food stores
-early spring roots

92
Q

how are green leaves and stems sources of assimilates?

A

glucose made in leaves=converted to sucrose=loaded into sieve tube elements

93
Q

what are some examples of storage organs ?

A

-tubers
-roots
-meristems

94
Q

where are food stores found?

A

seeds when plants germinate

95
Q

why are early spring roots assimilate sources?

A

source=energy stored as starch is converted to sucrose=moved to other plants of the plant=enable growth

96
Q

what 2 components of phloem tissue are concerned with transport?

A

-sieve tube elements
-companion cells

97
Q

what are the steps of active loading of assimilates at the source?

A

1)H+ ions actively pumped out of the companion cells via proton pumps=require ATP
2)ATP–>ADP
3)H+ conc. inside companion cell decreases
4)H+ ions diffuse back into cell=special cotransporter proteins
5)movement of H+ ions into companion cell is ONLY allowed if accompanied by sucrose=SECONDARY ACTIVE TRANSPORT
6)active transport of H+ out of the cell=sucrose moves against conc. gradient
7)movement of sucrose into cell=conc. increase
8)sucrose move into sieve tube via plasmodesmata=high conc. (companion cell) –> low conc. (STE)
9)water potential in sieve tube element decreases
10)water move from high water potential (companion cell) –> low water potential (STE) = osmosis
11)movement of water and sucrose=turgor pressure=mass flow of assimilates in phloem
12)assimilates flow from high turgor pressure to low turgor pressure=down pressure gradient
13)diff in turgor pressure=movement of water by mass flow
14)assimilates can move either up or down=depending on position of source

98
Q

what type of process is assimilate loading?

A

active

99
Q

what type of process is assimilate unloading?

A

passive

100
Q

describe the steps of phloem unloading?

A

1)sugar move into sink= low water potential
2)water follows= from high water potential (STE) –> low water potential (sink) –> OSMOSIS
3)uses sugar for various things=converted into something else
4)help maintain the conc. gradient between STE and sink

101
Q

what are the main sinks in a plant?

A

-roots
-meristems
-parts of plant that are laying down food stores

102
Q

summarise the steps of translocation?

A

1)sucrose actively loaded into STE =reduce water potential
2)water follow by osmosis= increases hydrostatic pressure in STE
3)sap move down sieve tube= high hydrostatic pressure (source) –> lower hydrostatic pressure (sink)
4)sucrose removed from sieve tube = increase water potential
5)water move out of sieve tube= reduce hydrostatic pressure

103
Q

what is the evidence supporting translocation?

A

1) phloem is cut= organic molecules exuded
2)flow of sugars in phloem is 10,000X faster than diffusion=active process
3)plants provided with radioactive CO2 at their roots, show radioactive carbon in phloem= supports mass flow
4)mitochondria is poisoned=inhibits production of ATP=translocation stops
5)sucrose conc. is higher in leaves than roots
6)ring of bark removed from woody stem=bulge forms above ring=build up of fluid=more sugar above bulge than below=evidence for downward flow (leaves to roots)
7)increasing the sucrose in the leaf= increase the sucrose in the phloem
8)downward flow occurs at daylight=photosynthesis – but not at night= higher respiration at night + lack of photosynthesis = no longer a conc. gradient

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