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Biology: Module 3: Exchange & Transport > Transport in Plants > Flashcards

Transport in Plants Flashcards

1
Q

Reasons why plants need transport system

A

Size, metabolic rate, surface area to volume ratio

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2
Q

Why size affects a plant’s need for a transport system

A

Large plants need to move substances up and down the entire length

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3
Q

Why metabolic demand affects a plant’s need for a transport system

A

Internal and underground plant parts need oxygen and glucose to get to them, hormones need transporting to where they have an effect, mineral ions need transporting to make proteins for enzymes

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4
Q

Why surface area to volume ratio affects a plant’s need for a transport system

A

Plants have a low surface area to volume ratio so diffusion is not enough to supply the plant cells with everything they need

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5
Q

Arrangement of vascular bundles in the stem

A

Around the edge for strength and support

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6
Q

Arrangement of vascular bundles in the root

A

In the middle to help withstand the tugging strains from the wind

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7
Q

Arrangement of vascular bundles in the leaf

A

Midrib of a leaf supports the structure of the leaf

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8
Q

Dicotyledonous plants

A

Plants that make seeds that contain two cotyledons

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9
Q

Cotyledons

A

Organs that act as food stores for developing embryos

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10
Q

Types of dicots

A

Herbaceous, woody

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11
Q

Structure of the xylem

A

Long hollow structures made of columns of cells fused together end to end, thick-walled parenchyma around the xylem vessels, lignified secondary walls, bordered pits

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12
Q

Role of thick walled parenchyma

A

To store food, to store tannins

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13
Q

Role of lignin in xylem

A

To provide mechanical strength

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14
Q

Arrangement of lignin in the xylem

A

Rings, spirals, solid tubes

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15
Q

Role of pits in the xylem

A

To be where the water leaves the xylem for other cells in the plant

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16
Q

Function of the xylem

A

To transport water and mineral ions, to support the plant

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17
Q

Structure of sieve tube elements

A

Many cells joined end to end to form a hollow structure, not lignified, sieve plates

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18
Q

Function of sieve tube elements

A

Main transporting vessels of organic solutes

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19
Q

Function of sieve plates

A

To let phloem contents flow through

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20
Q

Why mature phloem cells have no nucleus

A

Large pores appear in the cell walls, tonoplast and nucleus and other organelles break down, phloem fills with phloem sap

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21
Q

Structure of companion cells

A

Linked to sieve tube elements by plasmodesmata, nucleus and organelles present

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22
Q

Function of companion cells

A

To act as the life support system for the sieve tube cells

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23
Q

Structure of the phloem

A

Sieve tube elements, companion cells, fibres, sclereids

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24
Q

Sclereids

A

Cells with very thick cell walls

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25
Q

How to dissect stems to observe xylem

A

Put material in water containing a strongly coloured dye for 24 hours, rinse it, make clean transverse cut with a sharp blade on a white tile, xylem show up as spots, make a clean longitudinal cut, xylem show up as coloured lines

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26
Q

Limitations of dissection of stem to observe vascular bundles

A

Can’t be adjusted to see phloem, dependent on sharp blade and steady hand, if they aren’t cut in the right place you won’t see any xylem

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27
Q

Process of transpiration

A

Water evaporates from the surface of mesophyll cells into air spaces in the leaf and moves out of the stomata by diffusion, evaporation lowers water potential of the cell, water moves into cell by osmosis through apoplast and symplast pathways, repeated across the leaf to the xylem, water moves out of xylem by osmosis, water molecules form hydrogen bonds with each other resulting in cohesive forces causing capillary action, water drawn up the xylem to replace water lost by evaporation by the transpiration pull, transpiration pull causes tension in xylem

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28
Q

Theory related to transpiration

A

Cohesion-tension theory

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29
Q

Capillary action

A

Water moving up a narrow tube against the force of gravity

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30
Q

What is transpiration an inevitable consequence of?

A

Gaseous exchange for photosynthesis

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31
Q

Evidence for the cohesion-tension theory

A

Trees shrink in diameter when transpiration is at its highest because of the higher tension in the xylem, broken xylem vessels take up air rather than letting water out, broken xylem vessels can’t move water because the continuous stream has broken

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32
Q

How to measure transpiration rate

A

Potometer

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33
Q

Why is it difficult to measure transpiration directly?

A

Hard to condense and collect all water that evaporates from leaves without collecting water from the soil, hard to separate water from transpiration and water vapour from respiration

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34
Q

Precautions when setting up a potometer

A

All joints sealed with waterproof jelly, airtight, calibrated, cut the shoot at a slant, set up underwater

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35
Q

Which wall of the guard cell is more flexible?

A

Outer layer

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36
Q

Factors which will affect the rate of transpiration

A

Light intensity, relative humidity, temperature, air movement, soil-water availability

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37
Q

How does light intensity affect the rate of transpiration?

A

Increased light intensity opens more stomata, increases evaporation from the surfaces of the leaf

38
Q

How does relative humidity affect the rate of transpiration?

A

High relative humidity will lower the rate of transpiration, reduced water potential gradient

39
Q

How does temperature affect the rate of transpiration?

A

Increased temperature increases the kinetic energy of water molecules and increases rate of evaporation, increased temperature increases concentration of water vapour that the external air can hold

40
Q

How does air movement affect the rate of transpiration?

A

Air movement blows away diffusion shells, increases water potential gradient

41
Q

How does soil-water availability affect the rate of transpiration?

A

Dryness will put the plant under water stress and the rate of transpiration will be reduced

42
Q

Things water is used for in plants

A

Turgor pressure, cell expansion due to turgor, cooling by evaporation, transport medium, photosynthesis

43
Q

Adaptations of root hair cells

A

Microscopic size so can penetrate between soil particles, high surface area to volume ratio, thin surface layer, high concentration of solutes in the cytoplasm of root hair cells

44
Q

Names of water pathways through the root

A

Symplast, apoplast, vacuolar

45
Q

Symplast pathway

A

Water moves though continuous cytoplasm of plant cells through plasmodesmata by osmosis

46
Q

Apoplast pathway

A

Water moves through the cell walls and intercellular spaces between cellulose fibres, water entering xylem pulls a thread of water through the cell walls through cohesive forces

47
Q

Vacuolar pathway

A

Water moves through the vacuoles

48
Q

How water moves into the xylem

A

Reaches endodermis and Casparian strip, apoplast pathway diverges with symplast pathway, water passes through selectively permeable membranes, water potential in xylem is lower than that of endodermal cells, returns to apoplast pathway, root pressure results in water being pushed up xylem

49
Q

Why it is good that water must move through selectively permeable membranes before reaching the xylem

A

Removes toxic solutes because of lack of transport proteins for them

50
Q

Thing endodermal cells do to maintain water potential gradients

A

Pump mineral ions into the xylem by active transport

51
Q

Evidence for the role of active transport in root pressure

A

Cyanide causes root pressure to disappear, root pressure increases with a rise in temperature which suggests chemical reactions are involved, low levels of oxygen or glucose decreases root pressure, guttation

52
Q

Guttation

A

The forcing of xylem sap out of the ends of cut stems or from special pores at the ends of leaves

53
Q

Xerophytes

A

Plants that have adapted to be able to live and reproduce in places where there is little water availability

54
Q

Adaptations of xerophytes

A

Thick waxy cuticle, sunken stomata, fewer stomata, reduced leaf area, hairy leaves, curled leaves, succulents, leaf loss, long roots, shallow roots with large surface area, dormancy, disaccharide trehalose

55
Q

How a thick waxy cuticle reduces water loss

A

Prevents water loss through the cuticle

56
Q

How sunken stomata reduce water loss

A

Reduces air movement, reduce water potential gradient

57
Q

How fewer stomata reduces water loss

A

Reduce water loss by transpiration

58
Q

How reduced leaf surface area reduces water loss

A

Reduced surface area to volume ratio

59
Q

How hairy leaves reduce water loss

A

Trap water lost by transpiration, reduce water potential gradient

60
Q

How curled leaves reduce water loss

A

Confines stomata to microclimates

61
Q

How succulents are good for xerophytes

A

Water stored in specialised parenchyma tissue

62
Q

How losing leaves reduces water loss

A

Water can’t be lost through the leaves

63
Q

How long roots reduce water loss

A

Allow them to reach water that is further down

64
Q

How shallow roots with a large surface area work for xerophytes

A

Can absorb any available water before a rain shower evaporates

65
Q

Adaptations of marram grass

A

Vertical and horizontal roots, stomatal pits, hairs, curled leaves

66
Q

Adaptations of cacti

A

Vertical and horizontal roots, sunken stomata, reduced leaves, succulent

67
Q

Hydrophytes

A

Plants that live in water and need adaptations to cope with growing in water

68
Q

Why hydrophytes need to get rid of water

A

Need to float to get to light, air spaces need to be full of air

69
Q

Adaptations of hydrophytes

A

Very thin or no waxy cuticle, lots of stomata, stomata always open, reduced structure, wide flat leaves, small roots, large surface area of stems and roots under the water, air sacs, aerenchyma, pneumatophores

70
Q

How having a very thin or no waxy cuticle will help a hydrophyte

A

Water can be lost through the cuticle

71
Q

Why can hydrophytes have their stomata open all the time?

A

No worries about loss of turgor

72
Q

How wide, flat leaves help hydrophytes

A

Can capture more light

73
Q

How small roots help hydrophytes

A

Water can diffuse directly into stem and leaf tissue

74
Q

How having large surface areas of stem and root under water helps hydrophytes

A

Maximises the area for photosynthesis, maximises area for oxygen diffusion

75
Q

How having air sacs helps hydrophytes

A

Enables leaves to float to the surface of the water

76
Q

How aerenchyma helps hydrophytes

A

Makes leaves and stems more buoyant, low resistance internal pathway for movement of substances

77
Q

How pneumatophores help hydrophytes

A

Roots that grow upwards to get to the air

78
Q

Adaptations of water lilies

A

Wide flat leaves, stomata on the upside of the leaf, flexible stems

79
Q

Main substance transported by translocation

A

Sucrose

80
Q

Example of a source

A

Leaves

81
Q

Example of sinks

A

Roots, meristems

82
Q

Translocation

A

An energy requiring process that transports assimilates in the phloem between sources and sinks

83
Q

Assimilates

A

Transported products of photosynthesis

84
Q

Process of translocation

A

Hydrogen ions pumped out of companion cell using ATP, hydrogen ions return to companion cell via cotransport protein, sucrose cotransported, sucrose diffuses out of companion cell through plasmodesmata, water moves in by osmosis, carries assimilates, moves to areas of low pressure

85
Q

Adaptations of companion cells

A

Infoldings in cell membranes to increase surface area for active transport, lots of mitochondria

86
Q

How water and solutes are transported through a plant

A

Solute accumulation in phloem increases turgor pressure to force sap to regions of lower pressure, pressure differences transport the stuff

87
Q

How the phloem is unloaded

A

Diffusion of sucrose into surrounding cells, sucrose moves rapidly to maintain concentration gradient, loss of solute in phloem increases water potential of phloem, water moves into surrounding cells by osmosis, surrounding cells can be xylem

88
Q

Evidence for process of translocation

A

Microscopes show adaptations of companion cells, poisoned mitochondria stop translocation, flow is 10000 times faster than it would be if just done by diffusion, aphid’s stylet show there is a positive pressure

89
Q

Questions about translocation

A

Not all solutes move at same rate, role of sieve plates

90
Q

What do potometers measure?

A

Water uptake

91
Q

Why may potometer measurements not be representative of the rate of transpiration?

A

Not all of water uptaken is lost, uptake by a detached shoot is not the same as a whole plant

Biology: Module 3: Exchange & Transport (6 decks)

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