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BISC 101 Mid2 > Plant Transport > Flashcards

Plant Transport Flashcards

Lecture 10

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1
Q

Transpiration

A

loss of water from leaves

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2
Q

what does transpiration create?

A

a force that pulls xylem sap upwards

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3
Q

where are water and minerals transported?

A

upwards from root to shoot in xylem

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4
Q

roots absorb…

A

water and minerals from the soil

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5
Q

roots exchange…

A

gases with air spaces in soil

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6
Q

phloem sap function

A

transports sugars in both directions from site of production (leaves) to sites of storage (roots)

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7
Q

Water movement gradient (basically osmosis)

A

moves from areas of high water potential to low water potential

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8
Q

why is waters movement gradient the way it is?

A
  • due to solute concentration gradients
  • physical pressure exerted on water
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9
Q

Transport over short distances

A

occurs in the apoplast and symplast

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10
Q

transport over long-distance

A

occurs via bulk flow

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11
Q

what is the rate of transpiration regulated by

A

stomata (and their guard cells)

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12
Q

where are sugars transported

A

from sources to sinks via the phloem

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13
Q

Solute potential meaning

A

tendency of water to move by osmosis in response to differences in solute concentrations

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14
Q

isotonic solution solute concentrations are in what state?

A

in equilibrium meaning no net movement

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15
Q

water movement in hypotonic solution

A

moves into cell by osmosis
(low to high)

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16
Q

cell volume in animal cell

A

increases until the cell bursts

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17
Q

cell wall in plant cells

A

semi-rigid cell wall

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18
Q

pressure potential meaning

A

tendency of water to move in response to pressure

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19
Q

turgor pressure function

A

keeps cell firm

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20
Q

what are cells with no turgor pressure?

A

flacid

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21
Q

What does water movement in plants depend on?

A

Combination of solute and pressure potential

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22
Q

What is the endodermis

A

cyclindrical layer of cells forming a boundary between cortex and vascular tissue

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23
Q

what does the endodermis do?

A

controls ion uptake (selectively)

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24
Q

pericycle meaning

A

cells can become meristematic; produce lateral roots

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25
Q

what is the casparian strip?

A

narrow band of water-repellent wax secreted by endodermis cell walls

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26
Q

what does the casparian strip do?

A

blocks the apoplastic route forcing water to move into cytoplasm of endodermal cells

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27
Q

what does the casparian strip act as?

A
  • a filter letting K ions through but not Na ions
28
Q

How do plant cells communicate directly?

A

via plasmodesmata

29
Q

how do animal cells communicate?

A

via gap junctions

30
Q

what type of movement do plants use?

A

passive and active transport

31
Q

proton pumps function

A

primary role in plant transport processes and establishing membrane potentials

32
Q

Ion channels function

A

can be gated; opening and closing in response to voltage, stretching of membrane, chemical factors, etc.

33
Q

where is water potential high?

A

in soil

34
Q

where is water potential medium-high

A

in roots

35
Q

where is water potential low?

A

in leaves and the atmosphere

36
Q

where is there a water potential gradient?

A

between roots and shoots

37
Q

what are the 3 hypotheses for how water moves?

A

1) is water pushed against gravity by positive pressure in roots?
2) is water drawn up xylem cells by capillary action?
3) is water pulled up by a force generated in leaves?

38
Q

Guttation meaning

A

excess water forced from leaves early in the morning

39
Q

Does positive root pressure push water upwards against gravity in xylem tissue?

A

root pressure is only a minor mechanism. It’s too weak to counter gravity over long distances

40
Q

what is Surface tension?

A

downward pull that exists on water molecules at an air-water interface

41
Q

what is Adhesion?

A

molecular attraction between water molecules and a solid substrate due to hydrogen bonding

42
Q

what is Cohesion

A

molecular attraction between water molecules

43
Q

Is water movement by capillary action possible?

A

capillary action can only move water over short distances

44
Q

First step of transpirational pull

A

water vapour diffuses from moist air spaces to drier air

45
Q

second step of transpirational pull

A

initially water is replaced from water film coating mesophyll cells

46
Q

third step of transpirational pull

A

evaporation of water film causes water to retreat further into cell wall becoming curved

47
Q

fourth step of transpirational pull

A

increased surface tension pulls water from surrounding cells and air spaces due to cohesion

48
Q

fifth step of transpirational pull

A

water from the xylem is pulled into the surrounding cells and air spaces to replace the water that is lost

49
Q

what water properties does transpirational pull depend on?

A

surface tension
adhesion
cohesion

50
Q

what is the rate of transpiration regulated by?

A

stomatal density, and opening and closing

51
Q

why do leaves have a large SA:vol?

A

to maximize absorption of sunlight for photosynthesis

52
Q

what is wrong with leaves large SA:vol?

A

it increases water loss via stomata

53
Q

what does stomatal number vary with?

A

leaf size/shape and season

54
Q

what does stomatal density vary with?

A

environment and development

55
Q

guard cells take up water to become…

A

turgid, and bow out
= opening

56
Q

guard cells lose water to become…

A

flaccid, and less bowed
= closing

57
Q

translocation meaning

A

movement of sugars through a plant from sources to sinks via the phloem

58
Q

How is phloem sap transported?

A

bi-directionally in sieve-tube elements

59
Q

where is phloem sap transported?

A

from sites of sugar production to sites of sugar use or storage

60
Q

up to 30% of sap is what?

A

sucrose, AA’s, hormones, minerals, mRNA’s

61
Q

What does sucrose moving into sieve tubes do?

A

reduces water potential inside the sieve-tube elements

62
Q

what does the uptake of water do in the pressure-flow hypothesis

A

generates a positive (turgor) pressure which forces sap to flow along the sieve-tube

63
Q

what happens at the sink unloading sucrose?

A

water moves into xylem and turgor pressure drops

64
Q

what does a difference in turgor pressure do?

A

drives movement of phloem sap via bulk flow

65
Q

what direction does sucrose have to be pumped?

A

against its concentration gradient

66
Q

co-transporter function

A

uses the proton gradient to move sucrose into phloem cells against concentration gradient

BISC 101 Mid2 (5 decks)

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