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OCR A level Biology > 3.1.3 - Transport in Plants > Flashcards

3.1.3 - Transport in Plants Flashcards

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1
Q

What distinguishes stems from other parts of the plants

A

Presence of nodes and internodes

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2
Q

Role of vascular cambium

A

Responsible for secondary growth and contains meristematic tissue

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3
Q

Functions of roots

A

Anchor the plant in the ground
Store excess carbs
Absorbs water and minerals

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4
Q

Role of parenchyma

A

Involved in respiration, photosynthesis, storage and secretion
Heavily lignified

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5
Q

What is collenchyna tissue made of

A

Collenchyma cells
Pectin
Cellulose

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6
Q

Role of collenchyma

A

Provide support

Expands as the stem grows

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7
Q

Role of endodermal cells

A

Regulates the substances that enter

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8
Q

What is pericycle made of

A

Parenchyma and sclerenchyma

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9
Q

Role of pericycle

A

Maintains meristematic activity

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10
Q

What is xylem tissue made of

A

Tracheids
Vessel elements
Parenchyma
Sclerenchyma

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11
Q

Embolisms

A

Air bubbles formed in plant capillaries

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12
Q

Ions needed by plants

A 
NO3 ^2-
Mg ^2+
PO4 ^3-
K ^+
SO4 ^2-
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13
Q

What is the cortex made of

A

Parenchyma

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14
Q

Transpiration

A

Loss of water from leaves of a plant, occurs from underside of leaf (stomata)
Water moves from areas of high hydrostatic pressure to areas of low hydrostatic pressure

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15
Q

Functions of water in plants

A

Turgidity - keep stems and leaves rigid
Photosynthesis
Enzyme reactions - metabolic processes occur in solution
Transport - ions absorbed in solution and transported in xylem

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16
Q

Apoplastic pathway

A

Water moving from soil solution to root hair and across cortex to the xylem in the cell walls

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17
Q

Symplastic pathway

A

Water moving from soil solution to root hair and across cortex to the xylem through the cytoplasm and plasmodesmata

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18
Q

Vacuolar pathway

A

Water moving from soil solution to root hair and across cortex to the xylem through the vacuoles

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19
Q

Factors affecting rate of transpiration

A

Temperature
Humidity
Light intensity
Wind

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20
Q

Lignin

A

Causes spirals in xylem

Allows cells to stretch/expand

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21
Q

Adaptations of vessel elements

A

Hollow lumen
Perforated cell ends
Lignin for rigidity

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22
Q

Casparian strip

A

Controls amount of water coming in the endodermis

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23
Q

Factors affecting transpiration

A 
Temperature 
Humidity 
Light intensity 
Air movement 
Soil water availability
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24
Q

Control variables when using potometer

A

Cut at an angle to increase SA of lumen
Bung to stop water evaporating
Assemble potometer underwater - prevents air from entering
Dry leaves - no water molecules blocking stomata

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25
Q

Functions of roots

A

Anchor the plant in the ground
Store excess carb reserves
Absorb water and minerals

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26
Q

Purpose of root hairs

A

Provide a very large surface area for uptake of water and ions

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27
Q

Why is the root tip covered by a cap of cells

A

Protects dividing cells of the top and lubricates root movement

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28
Q

Meristem in roots

A

Increase height of plants

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29
Q

Meristem in stem

A

Increase plant girth

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30
Q

Stele

A

Section in middle of transverse section of dicotyledonous root

Endodermis
Xylem tissue
Phloem tissue

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31
Q

Water uptake

A

Water enters capillaries from soil (osmosis)
Apoplast and symplast pathways (root hair cells to cortex)
Water leaves apoplast at endodermis and enter from symplast
Water enters xylem under root pressure then travels in tracheids and vessel elements
Water carried to mesophyll through small veins
Evaporates in leaf air spaces and from stomata

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32
Q

Pith

A

Made of parenchyma cells

Forms inner cortex

33
Q

Epidermis in plants

A

Protects moist under tissues from desiccation and invasion of pathogens

34
Q

Transpiration

A

Loss of water from a plant

H2O moves from an area of high hydrostatic pressure to areas of low

35
Q

What is transpiration affected by

A

Gravity
Electrostatic forces
Water potential

36
Q

How does water enter the xylem from the soil

A

H2O moves into cell as active transport transports inorganic ions into the cell (ATP)
Lowers H2O potential –> higher conc. of solute; conc. gradient
H2O can moves from an area of high WP (soil) to an area of low WP (cell) - osmosis

37
Q

Translocation

A

Movement of dissolved solutes (sucrose) from sources to sinks through the phloem

38
Q

Why is translocation bidirectional

A

Roots can act as a sink by releasing carbs and also as a store depending on time of year

39
Q

Process of translocation

A

Glucose formed in photosynthesis and condensed (sucrose)
Moves into companion cell by active transport (active loading)
Reduces WP allowing H2O to move in (osmosis)
Creates high hydrostatic pressure - mass flow
Sucrose diffuses out of phloem to where it’s needed for growth and storage

40
Q

Mass flow

A

Assimilates enter sieve tube and lower wp
Water enters through osmosis and increases hydrostatic pressure
Assimilates leave at sink and increase wp
Water leaves and lowers hydrostatic pressure
High hydrostatic pressure, forcing sap through vessels towards regions of lower pressure

41
Q

How does the process of translocation reoccur

A

Sink removes sugar, increases WP –> H2O leaves tubes (osmosis) keeping hydrostatic pressure low

42
Q

Tonoplast

A

Membrane around cell wall

43
Q

Function of endodermis

A

Controls amount of H2O coming in (casparian strip)

44
Q

What is the Caspian strip made of

A

Suberin - impermeable to water, lipid

45
Q

What does Casparian strip stop

A

Movement of water through the apoplast

46
Q

Source to sink

A

Sugar moving from where its made to where its stored

47
Q

Possible sinks

A

Seeds
Fruit
Meristems
Roots

48
Q

Possible sources

A

Leaves
Food stores in seeds when they geminate
Storage organs

49
Q

How does water get up the xylem

A

Root pressure
Capillary action
Transpirational pull

H2O cannot return to cortex through apoplast therefore pressure builds up in cortex pushing H2O up xylem

50
Q

Root pressure

A

Endodermis in roots uses metabolic energy to pump ions into root
Reduces WP in xylem and medulla
H2O moves across endodermis into medulla (osmosis)

51
Q

Capillary action

A

H2O can rise up a narrow tube against the force of gravity

52
Q

Cohesion

A

Water molecules sticking together

53
Q

Adhesion

A

Attraction between water molecules and the walls of the xylem

54
Q

Transpirational pull

A

Loss of H20 through leaves must be replaced by H2O in xylem
H2O moves up xylem as a result of tension, created by loss of water in leaves
As H2O moves out of xylem, the whole column gets drawn up due to cohesion

55
Q

How does water move in and exit the leaf

A

Enters through the xylem, passes through mesophyll (osmosis) and diffuses through air space in spongy mesophyll
As H2O vapour collects WP rises, when higher in the leaf –> diffuses out of stomata

56
Q

Mesophytes

A

Plants adapted to a habitat with adequate water

57
Q

Halophytes

A

Plants adapted to a salty habitat

58
Q

Xerophytes

A

Plants adapted to dry habitats

59
Q

Adaptations of xerophytes

A

Rolled leaves - reduce SA
Reduced no. and size of stomata - reduces diffusion
Sunken stomata - creates pocket of water vapour
Thick waxy cuticle - impermeable
Hairy leaves - traps water vapour
Dense spongy mesophyll - smaller surface area for evaporation
Thick stem - stores water

60
Q

Hydrophytes

A

Plants adapted to live in freshwater

61
Q

Adaptations of hydrophytes

A

Aerenchyma - parenchyma with many air spaces (buoyancy and flotation): allows O2 to diffuse to roots for aerobic respiration
Reduced root system - water can diffuse directly into leaves, feathery roots hold up plant
Large thin leaves
Stomata on the upper surface only

62
Q

Adaptations of xylem

A

End walls removed to form long tubes
No cytoplasm/cell organelles - little resistance of flow of water
Lignified (waterproofing and strengthening)
Bordered pits - allow movement of water between vessels

63
Q

Adaptations of sieve tube elements

A 
Form long tubes
End walls are retained 
End walls contain many sieve pores (sieve plates)
Thin layer of cytoplasm 
Very few organelles; no nucleus
64
Q

Adaptations of companion cells

A

Closely associated with sieve tube elements
Connected to sieve tube elements by many plasmodesmata
Dense cytoplasm with many mitochondria
Large nucleus

65
Q

Cohesion-Tension theory

A

Evaporation at top of the xylem creates tension in the xylem

Water molecules are cohesive and form a column which is then pulled up by tension

66
Q

Transpiration stream

A

Movement of water up xylem vessels from roots to leaves (area of high hydrostatic pressure to area of low hydrostatic pressure)

67
Q

Translocation occurs through the sieve elements by …

A

Mass flow

68
Q

What gets transported in translocation

A

Assimilates such as sucrose and amino acids

69
Q

Why is using potometer not accurate

A

Assumption that water uptake by plants is the same as water loss
BUT water is used photosynthesis and is produced in respiration

70
Q

Why does wind affect transpiration

A

Vapour around stomata is blown away
Reduces water vapour around stomata
Creates steeper wpg

71
Q

Active loading

A

H+ ions pumped out of cc using active transport
Uses conc. gradient to move back into cc w. sucrose through a cotransporter protein
Sucrose builds up and diffuses through plasmodesmata into sieve tubes
Reduces wp

72
Q

Why is water loss from the leaves unavoidable

A

Stomata opens for gas exchange for photosynthesis
Photosynthesis is necessary to make sugars
Water lost through the cuticle

73
Q

Why is sucrose transported in translocation and not glucose

A

Soluble so can easily travel in solution

Metabolically inactive so not used during transport

74
Q

Why does low temperature cause death of cells

A

Ice forms and pierces membranes

Denaturing of proteins

75
Q

Evidence for the role of active transport in root pressure

A

Some poisons affect mitochondria and prevent production of ATP, when cyanide is applied to root cells, root pressure disappears
Root pressure increases w a rise in temp and decreases w/ a fall in temp –> chem reactions
If O2 levels fall or respiratory substrates so does root pressure
Guttation

76
Q

Evidence for cohesion tension theory

A

Changes in diameter of trees - when transpiration is at its highest as is the tension, diameter shrinks
When a xylem vessel is broken air is drawn in rather than water leaking out
Plant can no longer move water up the stem as continuous stream is broken

77
Q

Evidence for translocation

A

Microscopy allows us to see he adaptations of cc for active transport
If mitochondria of cc are poisoned, translocation stops
Flow of sugars n phloem is 10,000x faster than diffusion —> active process
Aphids

78
Q

Why is water stopped from entering the apoplast through the casparian strip

A

Ensures that water and dissolved mineral ions (especially nitrates) have to pass into the cell through the plasma membrane so the water and ions are in the cytoplasm
Prevents water from cortex going back to medulla

OCR A level Biology (25 decks)

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