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module 3: exchange and transport > 3.3 transport in plants > Flashcards

3.3 transport in plants Flashcards

1
Q

Why do plants need a transport system

A

Large plants have a small SA:V - need specialised exchange surfaces/ transport system

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2
Q

What do plants need a regular supply of

A

Water
Nutrients
Minerals
Oxygen

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3
Q

Why can plants not use diffusion alone

A

High metabolic demand
Large size
Small SA:V
Diffusion is too slow

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4
Q

What is the vascular bundle made of

A

Xylem
Phloem

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5
Q

What does xylem transport

A

Water and mineral ions

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6
Q

What does phloem transport

A

Sucrose and amino acids

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7
Q

What does herbaceous dicotyledonous plants mean

A

Non woody stem , 2 seed leaves plant

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8
Q

How do you dissect a plant

A

Stain
Cut stem longitudinaly or transversely

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9
Q

Describe the structure of xylem tissue

A

Xylem vessels which carry water
Hollow tubes
Elongated
End region of cell lost
Non lignified pit
Thick, lignified wall

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10
Q

What is the purpose of pits in xylem

A

Lateral water movement

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11
Q

What is the purpose of lignin in xylem

A

Waterproof and lignin spirals reinforces vessels so it doesn’t collapse

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12
Q

How does a continuous column form in xylem

A

Dead cells aligned end to end , end regions have been lost

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13
Q

Why are narrow tubes in xylem beneficial

A

Prevents breaking easily, capillary action effective

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14
Q

What are assimilates

A

Sucrose and amino acids

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15
Q

What do phloem consists of

A

Sieve tube elements
Companion cells

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16
Q

What are sieve tube elements

A

Elongated tubes lined up end em to end with sieve plates at the end (of the sieve tube elements)

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17
Q

What do sieve tubes contain and why is it beneficial

A

No nucleus and very little cytoplasm - allows mass flow of sap

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18
Q

What do sieve plates allow

A

Movement of sap from elements

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19
Q

How are companion cells specialised

A

Large nucleus
Dense cytoplasm
Lots of mitochondria

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20
Q

How are companion cells and sieve tube elements joined

A

Plasmodesmata - gaps in cell wall that connects cell

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21
Q

What do companion cells do

A

carry out active processes to actively load assimilates into sieve tubes

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22
Q

How is the vascular bundle structured in the roots

A

Central core of xylem in X shape
Phloem in the arms of xylem
Endodermis around the vascular bundle
Layer of meristem in the epidermis

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23
Q

How is the vascular bundle arranged in the stem

A

Found on the outer edge - Phloem on the outside and xylem on the middle side
Cambium found in the middle
Cortex

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24
Q

How is the vascular bundle arranged in the leaf

A

Xylem ontop of the phloem in the veins of the leaf
Vascular bundle called a midrib

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25
Q

What is transpiration

A

Loss of water vapour from upper parts of the plant via evaporation and diffusion

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26
Q

What is the transpiration steam

A

Flow of water from the root to the leaves in plants where it’s lost by evaporation

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27
Q

What happens during transpiration

A

Water enters the leaf through xylem
Moves by osmosis into cells in spongy mesophyll
Water evaporates from cell walls of spongy mesophyll
Water vapour moves out of leaf through open stomata down the water potential gradient

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28
Q

How is water pulled up a stem

A

Transpiration pull/ stream (cohesion)
Root pressure (active process)
Capillary action (adhesion)

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29
Q

What is the importance of transpiration

A

Transports mineral ions up the plant
Maintains cell turgidity
Water for growth , cell elongation and photosynthesis
Keeps plant cool

30
Q

How much water is lost by transpiration

A

95%

31
Q

What environmental factors affect transpiration

A

Light intensity
Temperature
Humidity
Wind/ air movement
Water

32
Q

How does light intensity impact transpiration

A

Bright LI = stomata open for photosynthesis = increases ROT

33
Q

How does temperature impact respiration

A

Higher temp = more evaporation = more kinetic energy = water potential will increase so increased ROT

34
Q

How does humidity impact respiration

A

Higher humidity = lowers rate of water loss - smaller water vapour potential gradient between air spaces in leaf and outside

35
Q

How does wind/ air movement impact respiration

A

Moving air = water vapour carried away = maintains a water potential gradient

36
Q

How does water impact transpiration

A

Little water in soil = plant cannot replace water lost = stomata close

37
Q

How is water lost through leaves

A

lost as water vapour through open stomata
Which lowers water vapour pressure in gaps = more water moves down gradient

38
Q

What is translocation

A

Movement of assimilates throughout the plant in the phloem

39
Q

What are assimilates

A

Substances that have become apart if the plant (sucrose, amino acids)

40
Q

What is the source

A

Part of the plant that loads assimilates into phloem sieve tubes

41
Q

What is the sink

A

Part of the plant that removes assimilates from phloem sieve tubes

42
Q

What are the order of processes in active loading

A
  1. Active transport
    2.facilitated diffusion
  2. Simple diffusion
  3. Osmosis
43
Q

Explain how active loading works

A

Active transport of H+ ions out of the companion cells using ATP from mitochondria in companion cells - creates concentration gradient
H+ ions diffuse back into via facilitated diffusion through cotransport proteins and brings sucrose with it
Higher conc. of sucrose in companion cells then in the sieve tubes so sucrose moves by simple diffusion
Water potential in sieve tubes decrease so water moves in tubes by osmosis

44
Q

What is plasmodesmata

A

Gaps in cell wall which connects two cells

45
Q

What are the systems that water through plants

A

Apoplast
Symplast
Vacuolar

46
Q

Explain the apoplast system

A

Water passes through spaces in the cell wall / between the cells
Doesn’t pass through plasma membranes into cells
Moves by mass flow

47
Q

Explain the symplast system

A

Water enters cell through the plasma membrane and passes through the plasmodesmata from cells to the next

48
Q

Explain the vacuolar pathway

A

Passes through vacuole as well as symplast

49
Q

What is the casparian strip

A

Waxy, waterproof strip impervious to water and stops water entering by apoplast and forces it through the plasma membrane (symplast)

50
Q

What is the casparian strip made of

A

Suberin

51
Q

What is water potential

A

Measure of tendancy of water molecules to move from one place to another

52
Q

How does water move in a concentration gradient

A

Down the concentration gradient
Moves from higher water potential to lower water potential

53
Q

How does water move in cells in plants

A

Water leaves the cell down the water potential gradient
As higher conc of mineral ions and sugars outside the cell so there is a lower water potential (more negative)
Water moves from cell to more negative cell

54
Q

How is water taken up by a plant

A

W.P is more negative in the cell so water moves in by osmosis

55
Q

What does turgid meant

A

Cell full of water and exerts pressure on cell wall making it stiff

56
Q

What is pressure potential

A

Water exerting pressure on walls

57
Q

How is water lost form a plant

A

Transpiration (evaporation)

58
Q

What happens when a plant is placed in salt solution

A

Has very negative water potential so water moves out

59
Q

What happens if water loss continues in a plant

A

Cytoplasm and vacuole shrink
No longer turgid -> plasmolysis (plasma membrane shrinks) cell is now flaccid

60
Q

What does plasmolysis mean

A

Plasma membrane shrinks

61
Q

What are terrestrial plants

A

Plants living on land

62
Q

How do terrestrial plants exchange gases

A

Through stomata

63
Q

Why do stomata need to be open

A

Allow CO2 moves in
Water loss
Allow 02 to be removed as a product

64
Q

explain adaptations of terrestrial plants

A

Waxy cuticle - reduce water loss by evaporation
Stomata on under surface of leaves - reduces evaporation from direct sun
Closed stomata at night - no light for photosynthesis
Deciduous plants lose leaves in the summer

65
Q

What is a hydrophyte

A

Plant that’s adapted to living in water/ very wet ground

66
Q

What is an example of a hydrophyte

A

Water lily

67
Q

Adaptations of water lilies

A

Stomata on upper epidermis - exposed to gases
Large air spaces - buoyancy in stem, O2 diffuse quickly
Thin waxy cuticle - don’t need to conserve water
Wide, flat leaves - increases SA , lots of sunlight available

68
Q

What is the difficulty with water lilies

A

Struggle with oxygen getting to submerged tissues

69
Q

What is a xerophyte

A

Plant adapted to living in dry conditions/ arid conditions

70
Q

What are examples of xerophytes

A

Cactus
Marram grass

71
Q

Adaptions of cactus

A

Succulents - store water in stem, become fleshy and swollen
Stem is ribbed/ fluted - expand when water available
Spines - reduce SA and water loss
Widespread roots - water underground
Thick, waxy cuticle - reduce evaporation
Sunken stomata/ pits - create local humidity, reduces air exposure

72
Q

Adaptations of marram grass

A

Thick, waxy cuticle - reduce evaporation
Stomata in pits, covered in hair reduce air movement, trap water
Dense spongy mesophyll - reduce water evaporation
Stomata on inner side of leaf - protected
Outer epidermis

module 3: exchange and transport (3 decks)

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