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AP Biology Semester 2 > Chapter 36 > Flashcards

Chapter 36 Flashcards

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1
Q

phloem transports photosynthetic products from _____ to ______

A

sources to sinks

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2
Q

xylem transports water and minerals from ____ to _____

A

roots to shoots

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3
Q

stem has what two purposes?

A
  1. as conduits for water and nutrients

2. supporting structures for leaves

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4
Q

true or false:

Roots are less competitive with other roots from the same plant than with roots from different plants

A

true

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5
Q

mycorrhizae

A

is a symbiotic association composed of a fungus and roots of a vascular plant.

  • this helps plants colonize land
  • increase the surface area for absorbing water and minerals
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6
Q

what are the two major pathways through plnats

A
  1. apoplast

2. symplast

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7
Q

apoplast

A

consists of everything external to the plasma membrane

-includes cell walls, extracellular spaces, and the interior of vessel elements and tracheids

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8
Q

symplast

A

consists of the cytosol of the living cells in a plant as well as the plasmodesmata

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9
Q

what are the tree transport routes for water and solutes ?

A
  1. the apoplastic route- through cell walls and extracellular spaces
  2. the symplastic route- through the cytosol and plasmadesmata
  3. the transmembrane route- across cell walls
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10
Q

what controls short distance movement of substances?

A

plasma membrane permeability

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11
Q

what type of transport occur in plants?

A

both active and passive

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12
Q

membrane potential in plants is established through what?

A

pumping H+ by proton pumps

  • *proton pump hydrolyzes ATP and uses the energy to pump hydrogen ions out of the cell
  • produces membrane potenetial and proton gradient used to transport different molecules
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13
Q

what is in plant cell membranes that allow only cetains ions to pass

A

ion channels

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14
Q

stomata opens in what three cues

A
  1. light induces guard cells to take up K+
  2. decrease of CO2 in leaf air space
  3. internal clock
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15
Q

guard cells may close stomata during the day if what three things happen?

A
  1. deficiency in water
  2. production of abscisic acid
  3. high temperatures increases CO2 in air space
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16
Q

water potential

A

a measurement that combines the effects of solute concentration and pressure

  • determines direction of movement of water
  • water flows from regions of high water potential to low
  • potential refers to water’s capacity to perform work
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17
Q

what is the water potential equation?

A

Ψ =ΨS +ΨP
(ΨS = solute potential)
(ΨP = physical pressure on solution)

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18
Q

turgor pressure

A

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

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19
Q

protoplast

A

the living part of the cell, which also includes the plasma membrane

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20
Q

aquaporins

A

transport proteins in the cell membrane that allow the passage of water
-affect the rate of water movement across the membrane

21
Q

where does the most water and mineral absorption occur?

A

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

22
Q

what accounts for much of the surface area of roots?

A

root hairs

23
Q

endodermis

A

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

24
Q

what ways can water cross the cortex?

A

either via symplast or apoplast

25
Q

waxy casparian strip

A

of the endodermal wall and blocks apoplastic transfer of minerals from the cortex to the vascular cylinder
-water and minerals in the apoplast must cross the plasma membrane of the endodermal cell (cell in casparian strip) to enter the vascular cylinder

26
Q

what are the steps for water and minerals to go into the tracheids and vessel elements

A

The endodermis regulates and transports needed minerals from the soil into the xylem
• Water and minerals move from the protoplasts of endodermal cells into their cell walls
• Diffusion and active transport are involved in this movement from symplast to apoplast
• Water and minerals now enter the tracheids and vessel elements

27
Q

xylem sap

A

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

  • involves transpiration (the evaporation of water from the plants surface)
  • transpired water is replaced as water travels up from the roots
28
Q

root pressure

A

the pressure given by roots since water flows in from the root cortex
-sometimes results in guttation which is the exudation of water droplets on tips or edges of leaves

29
Q

what helps water and minerals go up the xylem?

A
  1. root pressure (relatively weak and is a minor mechansim of moving water upwards)
  2. cohesion and adhesion (allows for water to stay connected and not go down on behalf of gravity)
  3. negative pressure
  4. transpiration pull (which causes negative pressure)
30
Q

is the xylem made of dead or alive cells?

A

dead hollow cells

31
Q

when the guard cells are turgid what happens?

when the guard cells are flaccid what happens?

A
  1. guard cells bow outward and the pore between them opens

2. guard cells become less bowed and pore closes

32
Q

When guard cells are hypertonic with potassium ions what happens?

A

water enters and makes the guard cells turgid

33
Q

when guard cells are hypotonic with potassium ions what happens?

A

water leaves the guard cell and makes them flaccid

34
Q

what can cause stomata to close during the daytime?

A

drought, high temp, and wind

35
Q

what does abscisic acid do?

A

it is produced in response to water deficiency and causes the closure of stomata

36
Q

xerophytes

A

plants adapted to arid climates

37
Q

what are some adaptations to reduce transpiration?

A
  1. xerophytes
  2. thick cuticle
  3. stomata mostly on underside of leaves
  4. shed leaves
  5. cacti store water
  6. CAM plants (only open stomata at night)
38
Q

translocation

A

the products of photosynthesis are transported through phloem

39
Q

in angiosperms what are the conduits for translocation

A

sieve tube elements

40
Q

phloem sap

A

aqueous solution that is high in sucrose

41
Q

sugar travels from source to sink or sink to source

A

source to sink

42
Q

sugar source

A

an organ that is a net produced of sugar such as mature leaves

43
Q

sugar sink

A

an organ that is net consumer or storer of sugar, such as tuber or bulb

44
Q

what is unique about some storage organs?

A

they can be a sugar sink in summer and sugar source in winter

45
Q

does sugar move by symplastic or apoplastic pathways?

A

it can move by symplastic or both symplastic and apoplastic

46
Q

what do companion cells do?

A

enhance solute movement between the apoplast and symplast

47
Q

phloem loading requires what?

A

active transport

  • proton pumping and cotransport of sucrose and H+ enable the cells to accumulate sucrose
  • at sink the sugar molecules diffuse from the phloem to sink tissues are followed by water
48
Q

pressure flow

A

phloem sap moving through a sieve tube by bulk flow driven by positive pressure

49
Q

self thinning

A

the dropping of sugar sinks such as flowers, seeds, or fruits

AP Biology Semester 2 (5 decks)

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