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Bio 186 > Transport in plants > Flashcards

Transport in plants Flashcards

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Biology 101 flashcards
1
Q

What are the two major angiosperm clades?

A

monocots

eudicots

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2
Q

What is a monocot?

A

one cotyledon (seed leaf) examples are orchids palms and grasses

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3
Q

What are eudicots?

A

two cotyledons (seed leafs) examples are roses, sunflowers peas, oaks, maples

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4
Q

Tissue organization of roots of vascular plants:

What is a characteristic of the epidermis?

A

it lacks a cuticle

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5
Q

Tissue organization of roots of vascular plants:

the ground tissue or cortex has what three uses?

A

storage

conduction of water and minirals from the root surface to the vascular tissue

innermost layer of cortex= endodermis; acts as selective barrier

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6
Q

Tissue organization of roots of vascular plants:

vascular tissues outer most layer is what?

A

outer most layer of vascular cylinder is called the pericycle and it gives rise to lateral roots

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7
Q

Tissue organization of the stem:

epidermis has a what?

A

a cuticle

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8
Q

Tissue organization of the stem:

ground tissue (cortex and pith) is used for what?

A

support

storage

photosynthesis

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9
Q

Tissue organization of the stem:

what is the arrangement of vascular bundles?

in eudicots

in monocots

A

eudicots: arranged in a ring
monocots: scattered throughout cortex

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10
Q

The ascent of water in a plant: how does it happen?

what are the four options?

A

diffusion

root pressure

capillary action

suction pump

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11
Q

Tissue organization of the stem:

diffusion characteristics?

A

water moved for short distance (>100 micro meters)

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12
Q

Tissue organization of the stem:

Root pressure characteristics?

A

water pushed upward from roots (least important)

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13
Q

Tissue organization of the stem:

capillary action characteristics?

A

cohesion and adhesion help fight gravity

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14
Q

Tissue organization of the stem:

suction pump characteristics?

A

water pulled up from roots by leaves

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15
Q

what do Fungi help do?

A

help plants absorb water and nutrient from soil

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16
Q

Where are the three places that water needs to move to and from?

A

from soil into roots (into epidermal cell)

across root (from cell to cell and across tissue)

across whole plant (roots–> leaves, leaves–> roots)

short and long distance transport

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17
Q

short distance transport of water across plasma membrane:

what does water potential(Ψ) predict?

A

predicts direction in which water will flow

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18
Q

what is Ψp?

A

pressure potential

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19
Q

what is Ψs?

A

solute potential (osmotic potential)

20
Q

what is Ψ measured in?

A

units of pressure: megapascals( MPa); 1 MPa = 10 atmospheres)

21
Q

What is Ψp when it is positive?

what is Ψp when it is negative?

A

Ψp is positive when a solution is compressed, negative when a solution is stretched (under tension)

22
Q

what is going on when Ψs is zero?

Ψs is negative what is happening?

A

Ψs = zero for pure water

Ψs is negative if solutes are present

23
Q

water moves in what direction?

A

doesn a water potential gradient

regions of high Ψ to region of low Ψ

24
Q

what do aquaporines do?

A

facilitate water transport

25
Q

flaccid plants are what?

A

limp: cell in surroundings where there is a tendancy for water to leave

26
Q

Turgid plants are what?

A

very firm: cells have greater (solute) than surrounding

water enters

27
Q

Plasmolysis plants are what?

A

cells loses water –> plasma membrane pulls away from cell walls

28
Q

Short distance transport from outer root cells to inner cells of roots is called what?

A

lateral transport

29
Q

What are the three routes in short distance transport of water within tissues and organs?

A

three routes

transmembrane route –> repeated crossings of plasma membranes

via symplast –> one crossing of plasma membrane

via apoplast

30
Q

What is Bulk flow function?

A

used for long distance transport

Bulk flow: movement of a fluid driven by pressure

independent of solute concentration

in xylem (tracheids and vessel elements) and phloem (sieve- tube elements)

in xylem: root pressure and negative pressure

31
Q

What is pushing xylem sap?

A

root pressure

32
Q

pulling xylem sap: cohesion tension hypothesis.

what drives this process?

A

transpiration

as water evaporates from the leaves, the water column is pulled up

33
Q

pulling xylem sap: cohesion tension hypothesis.

what are the key elements in this process?

A

water moves down a potential gradient

water column in xylem is under tension

weight of water column is supported by cohesion amoung water molecules and adhesion to the xylem

The casparian strip of the endodermis enforces symplastic movement of water and dissolved minirals

34
Q

What problems do bubbles pose?

A

serious problem for a plant

the xylem and water columns must be continuous for the cohesion tension mechanism to work

35
Q

Why do water columns break?

A

dissolved gasses can form bubbles when frozen xylem water thaws in the spring

dry soil can hold water so tightly that the tensile strength of water is exceeded

36
Q

solutions to the bubble problem?

A

be a small annual plant

make new xylem every year

use tracheids (smaller diameter), not vessels

vary the diameter of water conducting cells during the growing season

re establish continuous water columns by pushing water up from below–> root pressure

37
Q

what is the major pathway for water loss?

A

stomata

38
Q

Stomata: major path for water loss

Why do plants transpire?

A

unavoidable when stomata are open

water and minerals are transported up the xylem column to aerial parts of the plant

transpiration provides evaporative cooling

39
Q

How do the stomata work?

A

guard cells have bands of cell wall thickening

mechanism of opening:
Ψs in the guard cell falls –> water enters the guard cell down the Ψ gradient –> stomatal aperture opens

active transport of H+ out of the guard cells generates membrane potential

K+ from epidermal cells enters guard cells through K+ channels

water enters by osmosis

cells become more turgid

stomata open

40
Q

Photosynthesis- transpiration compromise

factors involved in stomatal opening and closing?

A

Water balance of the plant

internal clock

CO2
(low –> stomata open)
(high–> stomata close)

hormones: abscisic acid (ABA)
produced in roots and leaves in response to water deficiency
single guard cells to close stomata

Light
blue light
activation of blue light receptors stimulates activity of proton pump in the plasma membrane of guard cells –> promotes absorption of K+
independent of photosynthesis and 10X more effective than red light

red light:
works indirectly by increasing photosynthesis –> increase demand for CO2 –> decrease CO2

41
Q

Bulk flow by postive pressure: phloem transport

what are minerals transported?

A

sugars, (sucrose), AA, Minerals, Hormones

42
Q

Bulk flow by postive pressure: phloem transport

direction of transport?

A

from sources to sink

may change with season of plant’s developmental stage

43
Q

Bulk flow by postive pressure: phloem transport

sources?

A

plant organ that is a net roducer of sugar, by photosynthesis of by starch breakdown

44
Q

Bulk flow by postive pressure: phloem transport

sink?

A

organ that is a net consumer or depository of sugar

45
Q

Pressure flow model of phloem transport

A

sugar is loaded into companion cells and sieve tubes

water follows sugar by osmosis down Ψ gradient

uptake of water generates positive pressure

sugar is pushed along sieve tube by bulk flow

sugar is unloaded from phloem at the sink, moves by facilitation diffusion from phloem into sink tissue

Bio 186 (18 decks)

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