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Biology II > ch. 36 > Flashcards

ch. 36 Flashcards

1
Q

what does the stem do

A
  • conduits for water and nutrients
  • supports structures for leaves
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2
Q

what do shoot length and branching pattern affect?

A

light capture

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3
Q

what is there a tradeoff between?

A

growing tall and branching
- more energy invested into branching, less energy available for growth in height

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4
Q

what is there a positive correlation between?

A

water availability and leaf size

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5
Q

phyllotaxy

A

arrangement of leaves on the stem
- phyll - leaf
- tax - movement toward/away

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6
Q

phyllotaxy of most angiosperms

A

leaves arranged in spiral

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7
Q

angle between leaves

A

137.5 degrees, likely minimizes shading of lower leaves

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8
Q

what does leaf orientation affect

A

light absorption

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9
Q

low light conditions

A

horizontal leaves capture more sunlight

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10
Q

high light conditions

A

vertical leaves less damaged by sun and allow light to reach lower levels

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11
Q

why are stomatal pores necessary

A

diffusion of CO2 into the photosynthetic tissues of leaves

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12
Q

how is over 90% of water lost by plants

A

evaporation from stomatal pores

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13
Q

what do shoot adaptations represent compromises against

A

enhancing photosynthesis and minimizing water loss

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14
Q

what can root growth adjust to?

A

local conditions
- roots branch extensively into pockets with high nitrate and grow straight through pockets of low nitrate availability

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15
Q

roots and competition

A

roots from same plant less competitive than roots from dif plants

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16
Q

mycorrhizae

A

roots and hyphae of soil fungi form mutualistic associations
- mycorrhizal fungi increase surface area for absorbing water and minerals, especially phosphate

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17
Q

3 transport routes for water and solutes

A
  1. apoplastic
  2. symplastic
  3. transmembrane
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18
Q

apoplastic route

A

through cell walls and extracellular spaces

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19
Q

symplastic route

A

cross plasma membrane once and then travel through cytosol
- use plasmodesmata

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20
Q

transmembrane route

A

repeatedly cross plasma membranes as they pass from cell to cell

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21
Q

apo

A

away, furthest point

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22
Q

sym

A

with, in company

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23
Q

trans

A

cross

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24
Q

plastic

A

to grow or form, capable of being deformed without rupture

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25
Q

plasma membrane permeability controls what?

A

short-distance movement of substances

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26
Q

what types of transport occur in plants

A

both active and passive

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27
Q

establishment of membrane potential in plants

A

pumping H+ by proton pumps

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28
Q

potential =

A

voltage

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29
Q

establishment of membrane potential in animals

A

pumping Na+ by sodium=potassium pumps

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30
Q

different types of energy conversion

A
  1. H+ and membrane potential
  2. H+ and cotransport of neutral solutes
  3. H+ and cotransport of ions
  4. ion channels
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31
Q

osmosis

A

diffusion of water into or out of a cell that is affected by solute concentration and pressure

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32
Q

water potential =

A

solute potential + pressure potential
- determines direction of movement of water
- higher to lower

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33
Q

definition of potential

A

ability to do work

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34
Q

solute potential of a solution is inverse to what?

A

its molarity

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35
Q

what is solute potential also called?

A

osmotic potential

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36
Q

pressure potential

A

physical pressure on a solution

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37
Q

positive pressure potential

A

pushing
- solution being expelled from syringe

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38
Q

negative pressure potential

A

sucking
- solution withdrawn by syringe

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39
Q

turgor pressure

A

positive pressure exerted by plasma membrane against the cell wall and the cell wall against the protoplast

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40
Q

protoplast

A

living part of the cell, which includes plasma membrane

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41
Q

what does water potential affect?

A

uptake and loss of water by plant cells

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42
Q

what happens when a flaccid/limp cell is placed in an environment with a higher solute concentration

A

the cell will lose water through negative pressure and undergo plasmolysis

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43
Q

aquaporins

A

transport proteins in the cell membrane that facilitate the passage of water

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44
Q

what do the opening/closing of aquaporins affect the rate of

A

osmotic water movement across the membrane

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45
Q

bulk flow

A

movement of a fluid driven by a pressure gradient

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46
Q

what does efficient long-distance transport of fluid require

A

bulk flow

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47
Q

where do water and solute move together?

A

tracheids and vessel elements of xylem and sieve-tube elements of phloem

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48
Q

what do branching veins within leaves ensure

A

that all living cells are within a few cells of the vascular tissue

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49
Q

what is bulk flow enhanced by

A

structural adaptations of xylem and phloem cells
- mature tracheids/vessel elements have no cytoplasm
- sieve-tube elements have few organelles in cytoplasm
- perforation plates connect vessel elements
- porous sieve plates connect sieve-tube elements

50
Q

where does most water and mineral absorption occur

A

near root tips
- where root hairs are located and epidermis is permeable to water

51
Q

what accounts for much of the surface area of roots?

A

root hairs

52
Q

what happens after soil solution enters the roots?

A

the extensive surface area of cortical cell membranes enhances uptake of water and selected minerals

53
Q

what does active transport enable in the roots

A

essential minerals to accumulate at much higher concentrations in roots compared to the surrounding soil

54
Q

endodermis

A

innermost layer of cells in the root cortex
- surrounds vascular cylinder and is last checkpoint for selective passage of minerals from cortex into the vascular tissue

55
Q

water can cross the cortex via what?

A

symplast or apoplast

56
Q

Casparian strip

A

waxy strip in endodermal wall that blocks apopastic transfer of minerals from the cortex to the vascular cylinder

57
Q

what must water/minerals cross to enter the vascular cylinder of roots

A

the plasma membrane of an endodermal cell

58
Q

what do endodermal cells discharge?

A

water and minerals from their protoplasts into their own cell walls

59
Q

what are involved in the movement from symplast to apoplast

A

diffusion and active transport

60
Q

once in the apoplast after the endodermis, what do water and minerals do?

A

enter the tracheids and vessel elements

61
Q

xylem sap

A

water and dissolved minerals transported from roots to leaves by bulk flow

62
Q

what does the transport of xylem sap involve?

A

transpiration

63
Q

transpiration

A

evaporation of water from a plant’s surface

64
Q

how is transpired water replaced

A

as water travels up from the roots

65
Q

what do root cells do at night?

A

continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential

66
Q

root pressure

A

a push of xylem sap as water flows in from the root cortex

67
Q

what does root pressure sometimes result in?

A

guttation

68
Q

guttation

A

exudation of water droplets on tips or edges of leaves

69
Q

positive root pressure is relatively…

A

weak
- minor mechanism of xylem bulk flow

70
Q

cohesion-tension hypothesis

A

transpiration and water cohesion pull water from shoots to roots

71
Q

what is xylem sap normally under

A

negative pressure, or tension

72
Q

transpirational pull

A
  • water vapor in air spaces of leaf diffuses down water potential gradient and exits leaf via stomata
  • as water evaporates, air-water interface retreats into the mesophyll cell walls
  • surface tension of water at air-water interface creates a negative pressure potential
73
Q

what lowers water potential?

A

negative pressure potential

74
Q

how are water molecules pulled from more hydrated areas of the leaf

A

by the negative pressure potential created at the air-water interface

75
Q

what transfers the pulling forces to the water in the xylem

A

the cohesion of water molecules

76
Q

how are water molecules attracted to each other

A

cohesion
- water molecules exiting xylem tug on adjacent water molecules down the column

77
Q

what does adhesion do in the xylem

A

offset the force of gravity

78
Q

why do vessel elements and tracheids not collapse under negative pressure

A

thick secondary walls

79
Q

what can cause a break in the chain of water

A

drought stress or freezing
- causes cavitation

80
Q

cavitation

A

formation of a water vapor pocket

81
Q

how can transport of xylem sap continue after cavitation

A
  • move between adjacent xylem cells through pits
  • move from xylem to phloem tissue and back again
  • cavitation can be repaired
  • new xylem is added by secondary growth
82
Q

what is blue flow in xylem sap ascent driven by

A

water potential difference at opposite ends of xylem tissue
- driven by transpiration

83
Q

what does bulk flow require energy from

A

not from plant, but is solar powered like photosynthesis

84
Q

how does bulk flow differ from diffusion

A
  • driven by differences in pressure potential, not solute potential
  • occurs in hollow dead cells, not across membranes of living cells
  • moves entire solution, not just water or solutes
  • much faster
85
Q

do leaves have higher or lower surface area compared to volume

A

higher

86
Q

what happens when high surface areas of leaves increase the rate of photosynthesis

A

increase in water lost through stomata

87
Q

what do guard cells do

A

open and close stomata to help balance water conservation with gas exchange for photosynthesis

88
Q

what controls stomatal density

A

genetic and environmental control

89
Q

what happens to guard cells when they are turgid

A

guard cells bow outward and pore between them opens

90
Q

what happens to guard cells when they are flaccid

A

become less bowed and pore closes

91
Q

what do changes in turgor pressure result from

A

reversible uptake and loss of potassium ions by guard cells

92
Q

what are required to move K+ across the plasma membrane?
(under guard cell slides)

A

proton pumps that generate membrane potential

93
Q

when do stomata generally open and close

A

open during day, close at night

94
Q

what is stomatal opening triggered by?

A
  1. light
  2. CO2 depletion
  3. internal clock in guard cells
95
Q

circadian rhythms

A

24-hour cycles - internal clocks of eukaryotic organisms

96
Q

abscisic acid (ABA)

A

hormone produced in response to water deficiency and causes closure of stomata

97
Q

what do sunny, warm, dry, and windy conditions cause?

A

evaporation and increased transpiration rates

98
Q

true or false, some evaporative water loss occurs through the cuticle when stomata are closed

A

true

99
Q

what happens if uptake/transport of water not sufficient to replace lost water

A

plant will wilt

100
Q

evaporative cooling

A
  • another result of transpiration
  • can lower temperature of leaf
101
Q

xerophytes

A

plants adapted to arid climates

102
Q

xero

A

dry

103
Q

when do some desert plants complete their life cycle

A
  • during the rainy season
  • others have fleshy stems that store water or leaf modifications that reduce rate of transpiration
104
Q

crassulacean acid metabolism (CAM)

A

stomatal gas exchange occurs at night

105
Q

translocation

A

products of photosynthesis are transported through phloem

106
Q

elements for translocation in angiosperms

A

sieve-tube elements

107
Q

phloem sap

A

aqueous solution that is high in sucrose

108
Q

where does phloem sap travel

A

from sugar source to sugar sink

109
Q

sugar source

A

organ that is net producer of sugar, such as mature leaves

110
Q

sugar sink

A

organ that is net consumer or depository of sugar, such as roots, buds, and fruits

111
Q

true or false: A storage organ can be a sugar sink in the summer and sugar source in the spring

A

true

112
Q

where must sugar be loaded before being exported to sinks

A

sieve-tube elements

113
Q

does sugar move by symplastic of apoplastic pathways

A

depends on species

114
Q

what do companion cells do

A

enhance soul movement between apoplast and symplast

115
Q

what kind of transport does phloem loading require in many plants

A

active transport

116
Q

what enables the cells to accumulate sucrose

A

proton pumping and contransport of sucrose and H+

117
Q

what occurs at the sink

A

sugar molecules diffuse from the phloem to sink tissues and are followed by water

118
Q

how does phloem sap move

A

through a sieve tube by bulk flow driven by positive pressure called pressure flow
- flows from high pressure sources to low pressure sinks

119
Q

self-thinning

A

dropping of sugar sinks such as flowers, seeds, or fruits
- occurs when there are more sugar sinks than the sources can support

120
Q

symplast

A

continuum of cytosol linked by plasmodesmata

121
Q

apoplast

A

water-filled cell walls and intercellular spaces

Biology II (43 decks)

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