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biology > Lecture 26 - Plant Nutrition (part 1) > Flashcards

Lecture 26 - Plant Nutrition (part 1) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What did plant evolution result from?

A

adaptations to obtain food

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2
Q

What are the 2 systems that land plants have?

A
  1. above ground shoot system

2. below ground root system

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3
Q

above ground shoot system

A

absorb light for photosynthesis

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4
Q

below ground root system

A

water and minerals

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5
Q

Plant ancestors absorbed nutrients directly from their…

A

aquatic environment

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6
Q

Over time as plants moved onto land…

A

competition for resources resulted in taller plants, with broader leaves (more SA) for more light absorption

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7
Q

What is the cost of plants moving onto land?

A

More SA for light also means more SA for water loss
• Larger plants also need larger roots for anchorage
• Greater distance to transport nutrients between the root and shoot systems

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8
Q

What are the 2 vascular tissues that made the move to land all possible for plants?

A
  • Xylem

* Phloem

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9
Q

Xylem

A

transports water and nutrients from roots to shoots

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10
Q

Phloem

A

transports photosynthates from source to sink

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11
Q

What varies greatly amongst land plants?

A

shoot architecture (i.e. morphology)

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12
Q

What are examples of shoot architecture (i.e. morphology) that varies greatly amongst land plants?

A
  • Stem length and widths

* Branching pattern

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13
Q

What does stem length and widths allow for?

A

allows plants to grow tall

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14
Q

What does branching pattern allow for?

A

allows better light harvesting

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15
Q

What is the function of stems?

A

support leaves and act as conduits for water and nutrient transport

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16
Q

Leaves vary in size & structure & account for much of the diversity we see in land plants so DESCRIBE THIS

A
  • Various adaptations for specific habitats, PREVENTING water loss and MAXIMIZING photosynthesis
  • Most large leafed plants are tropical, smaller leafed plants are temperate, and very small leafed plants occur in harsh habitats
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17
Q

Phyllotaxy

A

is the arrangement of leaves on a plant

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18
Q

What is Phyllotaxy determined and genetically controlled by?

A

the SAM

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19
Q

1 leaf per node –>

A

alternate, spiral

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20
Q

2 leaves per node –>

A

opposite

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21
Q

Multiple leaves per node –>

A

whorled

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22
Q

What does total leaf area affect?

A

the productivity of each plant

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23
Q

How does total leaf area affect the productivity of each plant?

A
  • Leaves can SHADE other leaves on the same plant

* Plants can SELF-PRUNE leaves (and branches!)

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24
Q

Leaves can shade other leaves on the same plant…

A

reducing photosynthetic capacity (ie. They respire more than photosynthesise!)

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25
Q

Plants can self-prune leaves (and branches!)…

A

to optimising leaf area index

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26
Q

Leave orientation also affects…

A

photosynthetic capacity

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27
Q

In low light –>

A

horizontal leaves are best

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28
Q

In high light –>

A

vertical leaves prevent water loss and burning

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29
Q

What is the photosynthesis - water loss compromise?

A
  • Broad leaves absorb more light, have more stomata

* Stomata open to exchange gas, but there is water loss!

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30
Q

What is the roots function?

A

maximize morphology & growth to absorb nutrients

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31
Q

Roots won’t branch in areas of _______. But branches more in areas of _______.

A

low N availability

high nutrient loads, makes more proteins to take up more nitrogen

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32
Q

Roots associate with…

A

mycorrhizae to increase surface area of more nutrient uptake

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33
Q

What are the 2 main “compartments” of plant systems?

A
  1. Apoplast

2. Symplast

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34
Q

Apoplast

A

everything external to the plasma membrane (including cell walls and internal
spaces of dead tracheids and vessels)

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35
Q

Symplast

A

consists of the cytosol, plasmodesmata, & cytoplasmic interconnections

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36
Q

What are 3 main transport “routes”?

A
  1. Apoplastic
  2. Symplastic
  3. Transmembrane
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37
Q

Apoplastic

A

water and solutes move along the cell walls and extracellular spaces (like water through a sponge)

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38
Q

Symplastic

A

water and solutes move through the cytosol

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39
Q

Transmembrane

A

water and solutes move out of one cell, across the cell walls, and into the next cell

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40
Q

Both ____ & _____ transport occur in plant cells

A

active

passive

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41
Q

Primary Active Transport

A

Uses H+ for membrane potentials resulting from proton pumps

• Animals used Na+

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42
Q

Secondary Active Transport

A

H+ is also co-transported in plants (ex. sugar in phloem cells)
• Animals co-transport Na+

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43
Q

What does gated ion channels produce?

A

produces electrical signals similar to action potentials in animals
• K+ ions for the opening/closing of guard cells

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44
Q

What absorption or loss of water occurs by…

A

Osmosis (passive transport)

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45
Q

Water potential

A

(solute concentration + pressure) will direct the flow of water

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46
Q

Free water

A

(not bound to ions/solutes) moves from higher water potential to lower water potential

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47
Q

Active & passive transport in plant cells

A
  1. Uses ATP-dependent proton pumps to pump H+ OUT of the cell, establishing a membrane potential
  2. H+/sucrose cotransporters play a key role in sugar-loading INTO the PHLOEM
  3. H+/NO3 - cotransporters important for nitrate uptake BY the roots
  4. Opening and closing of the guard cells in the stomata
48
Q

What is water potential determined by?

A

solute potential and pressure potential

49
Q

Solute potential

A

is directly proportional to its molarity

• Also called osmotic pressure (solutes affect direction of osmosis)

50
Q

Solutes in plants are mostly…

A

ions & sugars

51
Q

Pure water has a solute potential =

A

0

52
Q

As solutes are added, ions bind to water –>

A

less free water

• Has a negative effect on water potential, so always written negative

53
Q

Pressure potential

A

is the PHYSICAL pressure on the solution
• Can be + or -
• Water inside plant cells is usually under + pressure due to water uptake

54
Q

The protoplast (living part of the cell)…

A

exerts (+) pressure on the cell wall, creating turgor pressure

55
Q

Water inside tracheids and vessels is often under…

A

negative pressure (tension)

56
Q

Flaccid cells (limp)

A

are from a loss of water

- The cell has a pressure potential = 0

57
Q

If put into a solution that has a lower water potential (hypertonic)…

A

water leaves the flaccid cell, resulting in plasmolysis

58
Q

If put into a solution of pure water (hypotonic)…

A

water moves inside the cell since the cell has more solutes than the pure water, exerting turgor pressure and becoming turgid

59
Q

Once the direction of water movement is determined…

A

aquaporins aid in the transport of water across the plasma membrane

60
Q

Aquaporins

A

They affect the rate in which water moves through the membrane

61
Q

Permeability of aquaporin channels is decreased by…

A

increases in cytosolic [Ca2+] or decreases in cytosolic pH

62
Q

Short-distance transport occurs…

A

across plasma membranes

63
Q

Long distance transport occurs through…

A

bulk flow

64
Q

Bulk flow

A

Movement of a liquid in response to a pressure gradient

65
Q

Bulk flow always occurs from…

A

high to low pressure

66
Q

Bulk flow is independent of…

A

solute concentration

67
Q

Where does bulk flow occur?

A

Occurs in tracheids and vessel elements in xylem and sieve-tube elements of the phloem

68
Q

Mature xylem cells have no ______ & sieve-tube elements lack bulky _____

A

cytoplasm

organelles

69
Q

Both kinds of transport can occur to move the same stuff around. Describe short-distance active transport & long distance transport

A

Short-distance active transport loads sugar into phloem cells

Long distance transport moves it from shoot to root

70
Q

Healthy/not wiltered plant =

A

turgid

71
Q

Wiltered plant =

A

flaccid

72
Q

Where does most of the absorption of nutrients & water start?

A

at the root hairs

73
Q

Root hairs are…

A

Permeable to water and its associated ions

74
Q

Where does water pass freely through (during transpiration)?

A

the cell walls and extracellular spaces (apoplastic transport)

75
Q

Pass through the cortex until it reaches the ________ surrounding the vascular stele (during transpiration)

A

endodermis

76
Q

Selective transport

A

forces water + minerals into the symplastic route due to the Casparian strip

77
Q

Casparian strip

A

highly suberized layer impervious to water

78
Q

Water and minerals then returns to the ______ route in the tracheids and vessel elements

A

apoplastic

79
Q

Once in the xylem, the xylem sap ______

A

move up the stem via bulk flow and into the leaf veins

80
Q

Leaf cells get water and essential nutrients, but water is lost due to…

A

transpiration -> water vapour exits the leaf

81
Q

What must the roots do continuously to counteract the loss through transpiration?

A

The roots must be continuously absorbing water to counteract the loss through transpiration

82
Q

If water loss in the leaves > root absorption…

A

the plant wilts

83
Q

How does xylem sap travel to the leaves?

A
  • Root pressure pushes it up the plant
  • Root cells are continuously actively pumping mineral ions in the xylem sap
  • The Casparian strip prevents mineral ions for going back into the root (selectively permeable, remember?)
  • Accumulation of minerals lowers water potential inside the vascular cylinder, causing water the flow from the root into the vascular stele, generating root pressure
  • This pushes the xylem sap up the stem
84
Q

Root pressure

A

pushes xylem sap up the plant

85
Q

Too much pressure of xylem sap being pushed up the stem can cause what?

A

guttation, water droplets exude (forced out) from the leaves (NOT the same as dew)

86
Q

Root pressure only accounts for a small fraction of what?

A

bulk transport in xylem

87
Q

Cohesion-tension Hypothesis

A
  • Transpiration provides the pull

* Cohesion of water molecules transmits this pull from shoots to roots

88
Q

Transpiration (Cohesion-tension Hypothesis)

A

provides the pull

89
Q

Cohesion (Cohesion-tension Hypothesis)

A

of water molecules transmits this pull from shoots to roots

90
Q

Xylem sap is normally under…

A

negative pressure (tension)

91
Q

Transpirational pull

A
  • Stomata on the leaves lead to internal air pockets, exposing mesophyll cells to CO2 for photosynthesis
  • Air is saturated with water vapour. Air outside the leaf is drier, and therefore has lower water potential than air inside the leaf
  • The negative water potential develops on the mesophyll cells, resulting in tension
92
Q

Stomata on the leaves lead to internal air pockets…

A

exposing mesophyll cells to CO2 for photosynthesis

93
Q

Air is saturated with water vapour. Air outside the leaf is drier, and
therefore has…

A

lower water potential than air inside the leaf

• Causes water to leave from inside of leaf to outside

94
Q

The negative water potential develops on the…

A

mesophyll cells, resulting in tension

95
Q

Cohesion

A

attractive force between the same kind of molecules
• Very strong due to hydrogen bonds in water
• Can pull water molecules up without them separating

96
Q

Adhesion

A

attractive force between different molecules

• Water molecules on hydrophilic cell wall molecules

97
Q

Upward pull on the sap creates…

A

tension

98
Q

Secondary cell walls prevent the…

A

tracheids and vessels from collapsing

99
Q

Air bubbles (embolisms) can disrupt the bulk flow of…

A

xylem sap

100
Q

Prolonged hydraulic failure can cause…

A

plant death

101
Q

What is transpiration regulated by?

A

stomata

102
Q

Leaves have high ______, which maximizes ______

A

SA:volume ratio

photosynthesis (but also water loss!)

103
Q

Stomata (sing. Stoma)

A

are flanked by 2 guard cells, which control the diameter of the stomatal pore

104
Q

When guard cells take in water from neighbouring cells, they become…

A

more turgid

105
Q

Uneven cell wall thickness causes the guard cells to…

A

bow (becoming bean shaped)

106
Q

When water is lost the guard cells become…

A

flaccid & the pore closes

107
Q

Change in turgor is a result of…

A

reversible absorption and loss of K+

108
Q

Accumulation of K+ inside the guard cell lowers the…

A

water potential, forcing water inside the guard cell (H+ leaves the cell)

109
Q

Loss of K+ ions from the guard cell raises the…

A

water potential of the guard cell, forcing water out of the guard cell (H+ enters the cell)

110
Q

Accumulation/loss of K+ both facilitated by active transport of H+ ->

A

results in a gradient and generation of a membrane potential which drives K+ in/out of the cells

111
Q

Opening/closing of stomata regulated by what?

A

circadian rhythms and plant hormones (ex. ABA produced is produced during water shortages)

112
Q

Most large leafed plants are what?

A

tropical

113
Q

Most smaller leafed plants are what?

A

temperate

114
Q

Most very small leafed plants occur where?

A

in harsh habitats

115
Q

What are limitations in architecture due to?

A

finite energy to devote to shoot growth

116
Q

What does Active Transport allow during transpiration?

A

root cortex cells to absorb and store essential minerals (K+, nitrates)

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