3.3 Translocation

Question 1

what is translocation?

Answer 1

the movement of sugars throughout the plant in the phloem from source to sink

Question 2

in which direction can translocation occur?

Answer 2

both directions (bidirectional)

Question 3

is translocation an active or passive process?

Answer 3

both

Question 4

what are the products being transported called?

Answer 4

assimilates

Question 5

what are the main SOURCES of a plant?

Answer 5

green leaves and stems
storage organs that are unloading (tubers)
food stores in seeds when they germinate

Question 6

what do sources do?

Answer 6

store sugars

Question 7

what do sinks do?

Answer 7

need and use the sugars

Question 8

what are the main SINKS of a plant?

Answer 8

growing roots
meristems actively dividing
parts laying down food stores - fruits, seeds

Question 9

translocation is the movement of organic solutes e.g.

Answer 9

sucrose

Question 10

what is the process by which organic solutes move from source to sink through the phloem?

Answer 10

mass flow

Question 11

in the symplastic route phloem loading occurs as the sucrose moves through what?

Answer 11

cytoplasm mesophyll cells

Question 12

(phloem loading) in the symplastic route, sucrose moves from mesophyll cells onto where, and how?

Answer 12

sieve tubes by diffusion through plasmodesmata

Question 13

(phloem loading) is the symplast route mainly passive or active?

Answer 13

passive

Question 14

what is the plasmodesmata?

Answer 14

gaps between cells through which cytoplasm can move

Question 15

(phloem loading) in the apoplast route sucrose travels through cell walls to where?

Answer 15

companion cells and sieve tube elements

Question 16

(phloem loading) in the apoplast route what is the process by which sucrose travels to companion cells and sieve tube elements?

Answer 16

diffusion

Question 17

(phloem loading) in the apoplast route, sucrose then moves across the cell membrane where and by what process?

Answer 17

cytoplasm

by active transport

Question 18

(phloem loading) in the symplastic route sucrose ends up where and what flows in?

Answer 18

sieve elements and water flows in by osmosis

Question 19

(phloem loading) in the symplastic route water flowing into the sieve elements where the sucrose is creates what?

Answer 19

pressure of water moving the sucrose through the phloem by mass flow

Question 20

(phloem loading) in the apoplast route sucrose moves by diffusion along a concentration gradient maintained by what?

Answer 20

removal of sucrose into phloem vessels

Question 21

(phloem loading) in the apoplast route, hydrogen ions are actively pumped out of where and using what?

Answer 21

companion cells into surrounding tissue using ATP

Question 22

(phloem loading) in the apoplast route hydrogen ions return to the companion cell down a what and via what?

Answer 22

concentration gradient via co transport protein

Question 23

(phloem loading) in the apoplast route, what is co transported with the hydrogen ions?

Answer 23

sucrose

Question 24

(phloem loading) in the apoplast route, as sucrose is co transported what does it increase?

Answer 24

sucrose concentration in companion cells and sieve tube elements

Question 25

companion cells have infoldings in their cell membrane to give what?

Answer 25

increased surface area for active transport of sucrose into cytoplasm

Question 26

companion cells also have many mitochondria for what?

Answer 26

supplying ATP needed for transport pumps

Question 27

a build up of sucrose means water moves in by osmosis, building up what?

Answer 27

turgor pressure due to rigid cell walls

Question 28

solute accumulation in the source leads to increase in what?

Answer 28

turgor pressure

Question 29

increased turgor pressure forces what to where?

Answer 29

sap to regions of low pressure in sinks

Question 30

(phloem unloading) sucrose can be unloaded at which point and to where?

Answer 30

at any point to cells needing it

Question 31

(phloem unloading) sucrose diffuses from phloem to where?

Answer 31

surrounding cells

Question 32

(phloem unloading) sucrose moves into other cells by what process?

Answer 32

diffusion

Question 33

(phloem unloading) sucrose can also move into other cells by being what?

Answer 33

converted into other substances

Question 34

(phloem unloading) give an example of when sucrose is converted into another substance:

Answer 34

glucose for respiration

starch for storage

Question 35

(phloem unloading) what effect does loss of solutes from phloem have on water potential?

Answer 35

increases water potential

Question 36

(phloem unloading) increase of water potential in phloem means water does what?

Answer 36

moves into surrounding cells by osmosis

Question 37

(phloem unloading) of water carried from solute to sink some is drawn into where?

Answer 37

transpiration stream in the xylem