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

Ch. 38 Water & Sugar Transport in Plants Flashcards

(78 cards)

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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
dry air
few water molecules present exert low pressure
26
warm air
water molecules move farther part & exert lower pressure
27
water-potential graident
a difference in water potential in one region compared with that in another region - determines direction that water moves (always higher to lower)
28
major hypotheses for how water could be transported to shoots
1) root pressure 2) capillary action 3) cohesion-tension
29
vascular tissue
tissue that transports water, nutrients, and sugars | - contains xylem & phloem
30
tissues in the root
1) epidermis 2) root hairs 3) cortex 4) endodermis 5) pericycle
31
epidermis
outermost layer of cells "outside skin"
32
root hair
a long, thin outgrowth of the epidermal cells of plant roots | - provide increased surface area fro water and nutrient absorption
33
cortex
(in plants) a layer of ground tissue found outside the vascular bundles of roots and outside the pith of a stem - stores carbohydrates
34
endodermis
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
pericycle
a layer of cells that forms the outer boundary of the vascular tissue "around circle"
36
water pathways
1) transmembrane route 2) apoplastic pathway 3) symplastic pathway
37
Casparian strip
a waxy later containing suberin - prevents water movement through the walls of endodermal cells - blocks apoplastic pathways of water and ion movement
38
suberin
waxy substance found in the cell walls of cork tissue and in the Casparian strip of endodermal cells - forms water repellent cylinder
39
root pressure
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
guttation
excretion of water droplets from plant leaves - visible in the morning (dew) - caused by root pressure
41
capillarity
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
adhesion
molecular attraction among UNLIKE molecules ie. water interacts with glass walls of capillary tube through hydrogen bonding
43
surface tention
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
cohesion
a molecular attraction among LIKE molecules ie. holds water molecules in the water column together
45
meniscus
the concave boundary layer formed at most air-water interfaces due to adhesion and surface tension
46
cohesion-tension theory
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
cohesion-tension theory possible due to
1) a continuous column of water throughout the plant | 2) hydrogen bonding between water molecules
48
bulk flow
a mass movement of a fluid/molecules along a pressure gradient (ie) water movement in through plant xylem and phloem
49
process of the cohesion-tension theory
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
evidence of cohesion-tension theory
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
crassulacean acid metabolism (CAM)
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
C4 photosynthesis
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
bundle-sheath cell
type of cell found around the vascular tissue (veins) of plant leaves - Calvin cycle for C4 plants occurs here - rubisco abundant
54
rubisco
enzyme that initiates the 1st step of Calvin cycle during photosynthesis: addition of a molecule of CO2 to ribulose biphosphate
55
translocation
movement of sugars through phloem by bulk flow | - specifically from sources to sinks
56
source
a tissue where sugar ENTERS the phloem - high sugar concentrations (ie) stem
57
sink
tissue where sugar EXITS the phloem - low sugar concentrations (ie) flowers & roots
58
sieve-tube element
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
specialiezed parenchyma cell types in phloem
1) sieve-tube element | 2) companion cell
60
companion cell
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
pressure-flow hypothesis
hypothesis that sugar movement through phloem tissue is due to differences in the turgor pressure of phloem sap
62
phloem loading
(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
phloem unloading
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
passive transport
ions or molecules DIFFUSE across a plasma membrane (along their electrochemical gradient) energy not required facilitated by channels and carriers (membrane protein)
65
examples of passive transport
1) channel proteins | 2) carrier proteins
66
channel protein
membrane protein that forms a pore - admits one or a few types of ions or molecules - passive transport
67
carrier protein
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
facilitated diffusion
passive movement of a substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins pay
69
active transport
movement of ions or molecules across a membrane against an electrochemcial gradient - requires energy (ATP) & assistance of a transport protein (pump)
70
examples of active transport
1) pump 2) symporter 3) antiporter
71
pump
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
cotransporter
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
types of cotransporters
1) symporter | 2) antiporter
74
symporter
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
antiporter
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
secondary activ etransport
transport of an ion/molecule in a defined direction against and with its electrochemical gradient
77
proton pump
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
tonoplast
membrane surrounding a plant vacuole

BIO225 (26 decks)

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