3.3 Translocation Flashcards

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1
Q

what is translocation?

A

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

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2
Q

in which direction can translocation occur?

A

both directions (bidirectional)

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3
Q

is translocation an active or passive process?

A

both

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4
Q

what are the products being transported called?

A

assimilates

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5
Q

what are the main SOURCES of a plant?

A

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

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6
Q

what do sources do?

A

store sugars

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7
Q

what do sinks do?

A

need and use the sugars

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8
Q

what are the main SINKS of a plant?

A

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

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9
Q

translocation is the movement of organic solutes e.g.

A

sucrose

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10
Q

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

A

mass flow

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11
Q

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

A

cytoplasm mesophyll cells

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12
Q

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

A

sieve tubes by diffusion through plasmodesmata

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13
Q

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

A

passive

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14
Q

what is the plasmodesmata?

A

gaps between cells through which cytoplasm can move

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15
Q

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

A

companion cells and sieve tube elements

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16
Q

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

A

diffusion

17
Q

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

A

cytoplasm

by active transport

18
Q

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

A

sieve elements and water flows in by osmosis

19
Q

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

A

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

20
Q

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

A

removal of sucrose into phloem vessels

21
Q

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

A

companion cells into surrounding tissue using ATP

22
Q

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

A

concentration gradient via co transport protein

23
Q

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

A

sucrose

24
Q

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

A

sucrose concentration in companion cells and sieve tube elements

25
Q

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

A

increased surface area for active transport of sucrose into cytoplasm

26
Q

companion cells also have many mitochondria for what?

A

supplying ATP needed for transport pumps

27
Q

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

A

turgor pressure due to rigid cell walls

28
Q

solute accumulation in the source leads to increase in what?

A

turgor pressure

29
Q

increased turgor pressure forces what to where?

A

sap to regions of low pressure in sinks

30
Q

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

A

at any point to cells needing it

31
Q

(phloem unloading) sucrose diffuses from phloem to where?

A

surrounding cells

32
Q

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

A

diffusion

33
Q

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

A

converted into other substances

34
Q

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

A

glucose for respiration

starch for storage

35
Q

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

A

increases water potential

36
Q

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

A

moves into surrounding cells by osmosis

37
Q

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

A

transpiration stream in the xylem