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BIO225 > Ch. 38 Water & Sugar Transport in Plants > Flashcards

Ch. 38 Water & Sugar Transport in Plants Flashcards

1
Q

transpiration

A

loss of water via evaporation from the aerial parts of plant

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2
Q

conditions for transpiration to occur

A

1) stomata are open

2) air surrounding leaves is drier than air inside leaves

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3
Q

water potential

A

the potential energy of water in a certain environment compared with the potential energy of pure water at room T and atmospheric pressure

  • living orgs: water potential = solute potential + pressure potential
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4
Q

water flow based on water potential

A

water flows from areas of HIGHER water potential to areas of LOWER water potential

high –> low

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5
Q

solution

A

a homogenous, liquid mixture containing several substances

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6
Q

solute

A

any substance that is dissolved in a liquid

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7
Q

isotonic

A

solute concentrations in the cell and the surrounding solution are the same
- no net movement of water

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8
Q

hypotonic

A

solution has lower solute concentration than the solution on the other side of the membrane
- results in the loss of water & shrinkage of the membrane-bound structure

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9
Q

osmosis

A

diffusion of water across a selectively permeable membrane from a region of low solute concentration (high water concentration) to a region of high solute concentration (low water concentration)

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10
Q

solute potential

A

a component of potential energy of water caused by difference in solute concentrations at two locations
- total solute concentration relative to pure water

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11
Q

low solute potential

A

high concentration of solutes

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12
Q

wall pressure

A

inward pressure exerted by a cell wall against the fluid contents of a living plant cell

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13
Q

turgor pressure

A

outward pressure exerted by the fluid contents of a living plant cell against its cell wall

  • pressure inside the cell
  • counteracts movement of water due to osmosis
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14
Q

turid

A

swollen & firm

- result of high internal pressure

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15
Q

pressure potential

A

any kind of physical pressure on water

- can be positive or negative

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16
Q

megapascal (MPa)

A

a unit of pressure (force per unit area) equivalent to 1 million pascals (Pa)

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17
Q

pascal (Pa)

A

a unit of measurement commonly applied to pressures (force per unit area)

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18
Q

flaccid

A

limp as a result of low internal (turgid) pressure
- no wall pressure

ie. wilted plant leaf

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19
Q

wilt

A

to lose turgor pressure in plant tissue

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20
Q

factors that influence movement of water

A

1) osmosis
2) solute potential
3) pressure potential

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21
Q

when solute potential is negative

A

1) compare solute potential to that of pure water
2) solute potentials are always negative b/c they are compared to water
3) there area always some salts in the cell–water potential is lower than that of water –> pure water will move into the cell

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22
Q

when solute potential is positive

A

1) potential pressure from the turgor pressure is (+) inside living cells
2) effects of equilibirium result in no net movement, no water movment

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23
Q

salt-adapted species

A

respond to low water potentials by accumulating solutes in root cells
- lowers solute potential of these plants

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24
Q

dry-adapted species

A

cope by tolerating low solute potentials

- lose water to the atmosphere

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25
Q

dry air

A

few water molecules present exert low pressure

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26
Q

warm air

A

water molecules move farther part & exert lower pressure

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27
Q

water-potential graident

A

a difference in water potential in one region compared with that in another region
- determines direction that water moves (always higher to lower)

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28
Q

major hypotheses for how water could be transported to shoots

A

1) root pressure
2) capillary action
3) cohesion-tension

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29
Q

vascular tissue

A

tissue that transports water, nutrients, and sugars

- contains xylem & phloem

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30
Q

tissues in the root

A

1) epidermis
2) root hairs
3) cortex
4) endodermis
5) pericycle

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31
Q

epidermis

A

outermost layer of cells

“outside skin”

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32
Q

root hair

A

a long, thin outgrowth of the epidermal cells of plant roots

- provide increased surface area fro water and nutrient absorption

33
Q

cortex

A

(in plants) a layer of ground tissue found outside the vascular bundles of roots and outside the pith of a stem
- stores carbohydrates

34
Q

endodermis

A

a cylindrical layer of cells that separates the cortex from the vascular tissue and location of the Casparian strip

  • controls ion uptake
  • prevents ion leakage from the vascular tissue

“inside skin”

35
Q

pericycle

A

a layer of cells that forms the outer boundary of the vascular tissue

“around circle”

36
Q

water pathways

A

1) transmembrane route
2) apoplastic pathway
3) symplastic pathway

37
Q

Casparian strip

A

a waxy later containing suberin

  • prevents water movement through the walls of endodermal cells
  • blocks apoplastic pathways of water and ion movement
38
Q

suberin

A

waxy substance found in the cell walls of cork tissue and in the Casparian strip of endodermal cells
- forms water repellent cylinder

39
Q

root pressure

A

positive pressure of xylem sap in the vascular tissue of roots

  • generated during night as result of ion accumulation from soil & osmotic water movement into the xylem
  • pressure potential that develops in roots
  • cannot push water all the way up a tall tree

drives water up against the force of gravity

40
Q

guttation

A

excretion of water droplets from plant leaves

  • visible in the morning (dew)
  • caused by root pressure
41
Q

capillarity

A

tendency of water to move up a narrow tube due to adhesion, cohesion, and surface tension

  • draws water up xylem cells
  • result of adhesion creating an upward pull at the water-container interface, surface tension creating upward pull all across the surface, & cohesion transmitting both forces to the water below
  • cannot pull water up a tall tree

aka capillary action

42
Q

adhesion

A

molecular attraction among UNLIKE molecules

ie. water interacts with glass walls of capillary tube through hydrogen bonding

43
Q

surface tention

A

a cohesive force that causes molecules at the surface of a liquid to stick together, thereby resisting deformation of the liquid’s surface & minimizing its surface area

ie. pulls water column up to minimize air-water interface

44
Q

cohesion

A

a molecular attraction among LIKE molecules

ie. holds water molecules in the water column together

45
Q

meniscus

A

the concave boundary layer formed at most air-water interfaces due to adhesion and surface tension

46
Q

cohesion-tension theory

A

water is pulled up to the tops of trees along a water-potential gradient, via forces generated by transpiration at leaf surfaces

  • leading hypothesis
  • does not require energy

because of hydrogen bonding between water molecules, water is pulled up through xylem in continuous columns

47
Q

cohesion-tension theory possible due to

A

1) a continuous column of water throughout the plant

2) hydrogen bonding between water molecules

48
Q

bulk flow

A

a mass movement of a fluid/molecules along a pressure gradient

(ie) water movement in through plant xylem and phloem

49
Q

process of the cohesion-tension theory

A

1) water vapor diffuses out of leaf
2) water evaporates inside leaf
3) water is pulled out of xylem
4) water is pulled up xylem
5) water is pulled out of root cortex
6) water moves from soil into root

50
Q

evidence of cohesion-tension theory

A

cut a actively transpiring leaf at its petiole, watery fluid in xylem withdraws from the edge toward inside of leaf

  • xylem sap is under tension
  • little to no xylem sap exits leaf
51
Q

crassulacean acid metabolism (CAM)

A

a type of photosynthesis

CO2 is fixed and stored in organic acids at night

  • day: stomata open
  • night CO2 released to feed Calvin cycle

temporally different than C3 photosynthesis

reduces water and CO2 loss by photorespiration

(ie) pineapple

52
Q

C4 photosynthesis

A

a type of photosynthesis

CO2 is fixed into 4-C sugars rather than 3-C like in C3 photosynthesis
- spatially different than C3 photosynthesis

enhances photosynthetic efficiency in hot, dry environments by reducing loss of oxygen due to photorespiration

(ie) cactus in the desert; sugarcane

53
Q

bundle-sheath cell

A

type of cell found around the vascular tissue (veins) of plant leaves

  • Calvin cycle for C4 plants occurs here
  • rubisco abundant
54
Q

rubisco

A

enzyme that initiates the 1st step of Calvin cycle during photosynthesis: addition of a molecule of CO2 to ribulose biphosphate

55
Q

translocation

A

movement of sugars through phloem by bulk flow

- specifically from sources to sinks

56
Q

source

A

a tissue where sugar ENTERS the phloem
- high sugar concentrations

(ie) stem

57
Q

sink

A

tissue where sugar EXITS the phloem
- low sugar concentrations

(ie) flowers & roots

58
Q

sieve-tube element

A

an elongated sugar-conducting cell in phloem that lacks nuclei

  • has sieve plates at both ends
  • allows sap to flow to adjacent cells

alive at maturity

59
Q

specialiezed parenchyma cell types in phloem

A

1) sieve-tube element

2) companion cell

60
Q

companion cell

A

a cell in the phloem connected to adjacent sieve-tube elements via plasmodesmata
- provide materials to maintain sieve-tube elements & function in loading and unloading of sugars into sieve-tube elements

alive at maturity

61
Q

pressure-flow hypothesis

A

hypothesis that sugar movement through phloem tissue is due to differences in the turgor pressure of phloem sap

62
Q

phloem loading

A

(pressure-flow hypothesis)

sucrose is moved by active transport from source cells through companion cells to sieve-tube members

may depend on a proton pump and a cotransporter

63
Q

phloem unloading

A

companion cells remove sucrose from the sieve-tube members into the sink root cells

  • creates phloem sap w/ a high water potential
  • water then moves back into the xylem
64
Q

passive transport

A

ions or molecules DIFFUSE across a plasma membrane (along their electrochemical gradient)

energy not required

facilitated by channels and carriers (membrane protein)

65
Q

examples of passive transport

A

1) channel proteins

2) carrier proteins

66
Q

channel protein

A

membrane protein that forms a pore

  • admits one or a few types of ions or molecules
  • passive transport
67
Q

carrier protein

A

membrane protein that facilitates diffusion of small molecule (ie. glucose) across a membrane by a process involving a reversible change in the shape of the protein

  • passive transport
  • conformational change

large molecules

68
Q

facilitated diffusion

A

passive movement of a substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins

pay

69
Q

active transport

A

movement of ions or molecules across a membrane against an electrochemcial gradient
- requires energy (ATP) & assistance of a transport protein (pump)

70
Q

examples of active transport

A

1) pump
2) symporter
3) antiporter

71
Q

pump

A

membrane protein that can hydrolize ATP & change shape to power active transport of a specific ion/molecule across a plasma membrane against its electrochemical gradient

72
Q

cotransporter

A

transmembrane protein that facilitates diffusion of an ion down its previously established electrochemical gradient
- uses the energy of that process to transport some other substance against its concentration gradient

73
Q

types of cotransporters

A

1) symporter

2) antiporter

74
Q

symporter

A

cotransport protein that transport solutes AGAINST a concentration gradient
- uses energy released when a different solute moves in the same direction down its electrochemcial gradient

1D

75
Q

antiporter

A

carrier protein that allows an ion to diffuse down an electrochemcial gradient
- uses the energy of that process to transport a different substance in the opposite direction against its concentration gradient

2D

76
Q

secondary activ etransport

A

transport of an ion/molecule in a defined direction against and with its electrochemical gradient

77
Q

proton pump

A

a membrane protein that can hydrolyze ATP to power active transport of protons (H+ ions) across a membrane against an electrochemical gradient

aka H+ ATPase

78
Q

tonoplast

A

membrane surrounding a plant vacuole

BIO225 (26 decks)

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