Chapter 36

Question 1

phloem transports photosynthetic products from _____ to ______

Answer 1

sources to sinks

Question 2

xylem transports water and minerals from ____ to _____

Answer 2

roots to shoots

Question 3

stem has what two purposes?

Answer 3

1. as conduits for water and nutrients

2. supporting structures for leaves

Question 4

true or false:

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

Answer 4

true

Question 5

mycorrhizae

Answer 5

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

Question 6

what are the two major pathways through plnats

Answer 6

1. apoplast

2. symplast

Question 7

apoplast

Answer 7

consists of everything external to the plasma membrane

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

Question 8

symplast

Answer 8

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

Question 9

what are the tree transport routes for water and solutes ?

Answer 9

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

Question 10

what controls short distance movement of substances?

Answer 10

plasma membrane permeability

Question 11

what type of transport occur in plants?

Answer 11

both active and passive

Question 12

membrane potential in plants is established through what?

Answer 12

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

Question 13

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

Answer 13

ion channels

Question 14

stomata opens in what three cues

Answer 14

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

Question 15

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

Answer 15

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

Question 16

water potential

Answer 16

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

Question 17

what is the water potential equation?

Answer 17

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

Question 18

turgor pressure

Answer 18

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

Question 19

protoplast

Answer 19

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

Question 20

aquaporins

Answer 20

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

Question 21

where does the most water and mineral absorption occur?

Answer 21

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

Question 22

what accounts for much of the surface area of roots?

Answer 22

root hairs

Question 23

endodermis

Answer 23

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

Question 24

what ways can water cross the cortex?

Answer 24

either via symplast or apoplast

Question 25

waxy casparian strip

Answer 25

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

Question 26

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

Answer 26

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

Question 27

xylem sap

Answer 27

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

Question 28

root pressure

Answer 28

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

Question 29

what helps water and minerals go up the xylem?

Answer 29

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)

Question 30

is the xylem made of dead or alive cells?

Answer 30

dead hollow cells

Question 31

when the guard cells are turgid what happens? | when the guard cells are flaccid what happens?

Answer 31

1. guard cells bow outward and the pore between them opens | 2. guard cells become less bowed and pore closes

Question 32

When guard cells are hypertonic with potassium ions what happens?

Answer 32

water enters and makes the guard cells turgid

Question 33

when guard cells are hypotonic with potassium ions what happens?

Answer 33

water leaves the guard cell and makes them flaccid

Question 34

what can cause stomata to close during the daytime?

Answer 34

drought, high temp, and wind

Question 35

what does abscisic acid do?

Answer 35

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

Question 36

xerophytes

Answer 36

plants adapted to arid climates

Question 37

what are some adaptations to reduce transpiration?

Answer 37

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)

Question 38

translocation

Answer 38

the products of photosynthesis are transported through phloem

Question 39

in angiosperms what are the conduits for translocation

Answer 39

sieve tube elements

Question 40

phloem sap

Answer 40

aqueous solution that is high in sucrose

Question 41

sugar travels from source to sink or sink to source

Answer 41

source to sink

Question 42

sugar source

Answer 42

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

Question 43

sugar sink

Answer 43

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

Question 44

what is unique about some storage organs?

Answer 44

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

Question 45

does sugar move by symplastic or apoplastic pathways?

Answer 45

it can move by symplastic or both symplastic and apoplastic

Question 46

what do companion cells do?

Answer 46

enhance solute movement between the apoplast and symplast

Question 47

phloem loading requires what?

Answer 47

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

Question 48

pressure flow

Answer 48

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

Question 49

self thinning

Answer 49

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