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PLANT PHYSIOLOGY > 8b > Flashcards

8b Flashcards

1
Q

Movement of water through xylem is due to which properties of water?

A

Cohesion and adhesion

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2
Q

Cohesion- tension hypothesis: water loss through…

A

Stomata and cuticle transpiration

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3
Q

Cohesion- tension hypothesis: related to water potential

A
  • At start leaf has potential between 0 and-1MPa
  • stoma opening results in water loss
  • cells near stoma reduce water potential
  • water flows from cells further away toward stoma
  • results in water gradient
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4
Q

What does transpiration provide for water movement

A

The pull

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5
Q

What works against transpiration?

A

Gravity

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6
Q

Gravity gives a ______ water potential

It is more negative at the _____ of the stem than _____ stem

A

Negative

Top, lower

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7
Q

Is vertical or lateral movement more difficult?

A

Vertical movement

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8
Q

For every 10 meters of height the leaf water potential must be ______ more -ve than root water potential

A

0.1MPa

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9
Q

Leaves of a 30m tree must be ____ more - ve than roots

A

0.3MPa

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10
Q

Which 3 plant parts are not affected by gravity because they have lateral movement?

A

Stolons, rhizomes, and vines

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11
Q

Does cohesion or adhesion resist water movement?

A

Adhesion

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12
Q

Water interacts with cell walls Of ________ _________

A

Vessel elements

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13
Q

As soil dries its water potential becomes more negative or positive?

A

More negative

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14
Q

Leaves lose water faster because the xylem can’t replace it

During night or day?

A

During the day

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15
Q

Stomata close and leaves are rehydrated

During night or day?

A

During night

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16
Q

Soils water potential varies by what?

A

Soil type and % moisture

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17
Q

Roots must have higher or lower water potential than soil to attract water?

A

Lower

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18
Q

Roots must have higher Or lower water potential than leaves?

A

Higher

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19
Q

What puts plants under stress?

A

Dry air and soil

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20
Q

If stomata closes how does transpiration loss still occur?

A

Through the cuticle

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21
Q

Tension on the water column can result in

A

Cavitation

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22
Q

What is cavitation

A

The rupture of a water column

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23
Q

Cavitation can result in

A

An embolism that can spread

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24
Q

What is an embolism?

A

The filling of vessels or tracheids with air or water vapour

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25
Q

In tracheids what can the bubbles not pass through? And what are they restricted to?

A

Bubbles can’t pass through the pit membranes

Restricted to one tracheid

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26
Q

In vessels what does the bubble follow through to empty the whole vessel?

A

Perforation plates

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27
Q

Transpiration is the:

A) flow of water through the xylem
B) loss of water Vapor from plants
C) absorption of water by roots
D) loss of carbon dioxide from leaves

A

B) loss of water Vapor from plants

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28
Q

Approximately ________ % of the water transpired by a plant is lost through its stomata

a) 10
b) 25
c) 60
d) 90

A

d) 90

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29
Q

Which of the following is NOT consistent with cohesion-tension theory?

A) a gradient of water potential exists between the stem and root
B) transpiration brings an increased water potential in the leaves
C) water in xylem is under tension
D) a gradient of water potential provides the driving force for the movement of water from the soil through the plant to the atmosphere

A

B) transpiration brings an increased water potential in the leaves

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30
Q

In vascular plants, cavitation is the:

A) ruputure of water columns
B) expulsion of air from water columns
C) formation of air bubbles due to particulate matter
D) reduction of surface tension at the meniscus spanning pores in the pit membrane

A

A) ruputure of water columns

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31
Q

What is hydraulic redistribution?

A

Passive movement of water from Wet to dry soil via roots

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32
Q

hydraulic redistribution: how is water taken up? Soil conditions? how and where is it transferred to?

A

Water taken up by up roots in moist soil is transferred to dry soil via shallows roots

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33
Q

What does hydraulic redistribution redistribute?

A

Soil water

34
Q

When does hydraulic redistribution occur?

A

At night or during low transpiration periods

35
Q

Root pressure: when and why does movement of water occur

A

At night movement of water occurs when ions are secreted into the xylem

36
Q

Root pressure: ions secreted into the xylem does what to water potential in the xylem and allows water to do what?

A

Decreases water potential in xylem and allows water to flow

37
Q

Root pressure: Decreased water potential in the xylem creates what pressure in the xylem and forces water which direction?

A

Positive pressure, upward

38
Q

Root pressure: positive pressure in xylem causes what?

A

Guttation

39
Q

What is guttation?

A

Exudation of liquid water from leaves

40
Q

How are assimilates transported?

A

From source to sink

41
Q

What are assimilated carbons?

A

Carbohydrates in phloem tissue

42
Q

What is a source

A

Site from which assimilate solutes are transported

43
Q

What are sinks

A

Plant parts unable to meet their own nutritional needs

44
Q

In spring and summer, what is the predominant source for long-distance phloem transport?

A

Leaves

45
Q

Name 2 storage sites when exporting assimilates

A

Tubers and corms

46
Q

Sinks are sites that receive transported:

A

Phloem sap

47
Q

Name 3 things that can be sinks

A

Meristems or root tips, developing fruit and seeds, storage tubers and corms

48
Q

Are the different types of sinks active at the same time?

A

No

49
Q

What is the pressure flow hypothesis?

A

Assimilates are transported from sources to sinks along a gradient of turgor pressure developed osmotically

50
Q

pressure flow hypothesis: sugars are loaded into sieve tube-companion cell complexes at a _________

A

Source

51
Q

pressure flow hypothesis: water potential of sieve tube is

A

Decreased

52
Q

pressure flow hypothesis: water moves into _______ ____ from xylem by osmosis

A

Sieve tube

53
Q

pressure flow hypothesis: pressure _________ at the source

A

Increases

54
Q

pressure flow hypothesis: removal of sugar from sieve tubes at a _______ increases ___________ _______ of sieve tube

A

Sink, water potential

55
Q

pressure flow hypothesis: water moves out by

A

Osmosis

56
Q

pressure flow hypothesis: _______ have lower pressure than _________

A

Sinks, sources

57
Q

pressure flow hypothesis: sugar molecules are carried passively by water along the _________ ______ from _______ to _______

A

Concentration gradient

Source

Sink

58
Q

Sieve tube elements are

A

Living cells

59
Q

Vacuole membrane of sieve tube elements disintegrates and vacuole contents mix with_________ to give__________ ______

A

Cytoplasm, phloem sap

60
Q

Vascular bundles vary in ______ and _______ of transfer

A

Speed and site

61
Q

Phloem loading is apoplasticc or symplastic?

A

Can be either

62
Q

Apoplastic is seen in many _______ plants

A

Herbaceous

63
Q

Sugars from mesophyll cells initially follow a ___________ pathway

A

Symplastic

64
Q

Sucrose loading involves

A

Sucrose-proton symport

65
Q

What is symplastic

A

Sugars move entirely via plasmodesmata from mesophyll to sieve tubes

66
Q

Polymer trapping mechanism

A

Sucrose diffuses from bundle- sheath cells to intermediary cells

67
Q

Polymer trapping mechanism: sucrose is used to synthesize _________ and _________

A

Raffinose and stachyose

68
Q

Polymer trapping mechanism: these polymers cannot diffuse back to the bundle sheath cells but can go into:

A

Sieve tubes

69
Q

Passive symplastic loading is seen in:

A

Many tree species

70
Q

Sugars produced at high levels in mesophyll diffuse along concentration gradients to ________ ______

A

Sieve tubes

71
Q

Phloem unloading: at the _______, sucrose is transported out of sieve terse elements

A

Sinks

72
Q

Phloem unloading is apoplastic or symplastic

A

Can be both

73
Q

Phloem unloading: transport into sink tissues depends on

A

metabolic activity

74
Q

Why don’t source cells have a higher water potential?

A

Sugars are transported at the same rate they are synthesized

The sere no loss in water potential in source cells

In tubers sucrose leaves the cell at the same rate as starch is depolymerized

75
Q

Why don’t sink cells have a more negative water potential?

A

Sucrose is depolymerized into starch or cellulose

Flow direction is controlled by unknown switch mechanism (pump is regulated)

Young leaves switch from sink to source upon maturity

76
Q

What are 3 components of water potential?

A

Osmotic, pressure, matric

77
Q

Which of the potentials measure’s waters interaction with dissolved material?

A

Osmotic potential

78
Q

What is the water potential of pure water?

A

0

79
Q

Does water potential become more positive or negative as you add solute?

A

More negative

80
Q

When water potentials of two cells are in equilibrium is there any net movement of water?

A

No

81
Q

Water moves by osmosis into a plant root because

A

Water moves towards areas of higher solute concentration

82
Q

Minerals will more into a root hair cell when:

A

When solute concentration is lower inside the cell and transport proteins are present

PLANT PHYSIOLOGY (2 decks)

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