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Organism 1 Finals > Vasculature 2: phloem and phloem loading > Flashcards

Vasculature 2: phloem and phloem loading Flashcards

1
Q

what is phloem

A

specialized in the movement of large organic compounds throughout the plant

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2
Q

what are photosynthates

A

sugar products of photosynthesis

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3
Q

what is phloem sap

A

solution of sugars, water and other organic compounds found in the phloem

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4
Q

what are the types of phloem cells

A

sieve-tube elements
fibers
parenchyma cells

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5
Q

what are sieve-tube element cells

A

highly specialized unique cells

lack nucleus, ribosomes, vacuole

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6
Q

what are 2 types of sieve tube elements

A

sieve tube members

sieve cells

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7
Q

how are sieve tube elements divided

A

along taxonomic lines

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8
Q

what are sieve tube members

A

specialized phloem cell found mainly in angiosperms
contains a sieve plate
growth supported by a companion cell

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9
Q

what is a sieve plate

A

dividing structure between adjacent sieve tube member cells

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10
Q

what does a sieve plate consist of

A

many plasodesmata enlarged to allow for the efficient transport of nutrients betweencells

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11
Q

how does xylem support growth

A

doesnt because cells are dead at amturity

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12
Q

how does phloem support growth

A

partners with companion cell

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13
Q

what is a companion cells role

A

provides most of the proteins and other metabolites that the sieve tube member needs to remain alive

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14
Q

characterizations of the companion cells

A

are specialized parenchyma cells

connect to a sieve tube member through plasmodesmata

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15
Q

what are sieve cells

A

phloem cell found mainly in gymnosperms and seedless vasc plants

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16
Q

what characterizes sieve cells

A

a lack of sieve plate
being generally longer and thinner than sieve tube members
associate with an albuminous cell

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17
Q

what is an albuminous cell

A

a modified parenchyma cell that supports the metabolic activity of the sieve cell

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18
Q

difference between albuminous cell and companion cell

A

albuminous does not arise from the same mother cell as the sieve cell

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19
Q

what is translocation

A

process of sugars moving through the plant

moves substances from source to sink in the plant

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20
Q

what is the main form of sugar transported through the phloem

A

sucrose

21
Q

what are source tissues

A

any plant part which generates more sugars than it consumes

22
Q

what do source tissue include

A

storage organs

young and fully expanded leaves

23
Q

what are sink tissues

A

any plant part which is unable to meet its nutritional sugar needs

24
Q

what do sink tissues include

A 
roots
storage organs
older leaves
leaves which are expanding
flowers/fruits
25
Q

what is the vegetative stage of development

A
  • younest matur leaves send sugars toward apical stem
  • oldest leaves send sugars to roots
  • middle leaves send sugars in either direction
26
Q

what is the reproductive stage of development

A

fruits require vast majority of sugars in the plant
vegetative growth slows down through lack of sugars for growth
middle leaves will send all their sugars to the developing repro structures

27
Q

what drives movement of phloem

A

source and sink tissues

phloem sap can move up or down the plant

28
Q

what drives the movement of xylem

A

transpiration

water can only move up the plant

29
Q

what is phloem loading/unloading

A

movement of sugars in and out of the phloem

30
Q

what is pressure-flow hypthesis

A

movement of sugars through the phloem

31
Q

what is passive phloem loading

A
  • movement of sugars from the mesophyll cels of the leaf to the phloem cells along a concentration gradient
  • driven by a concentration gradient of sucrose
  • sucrose moves through plasmodesmata of adjacent cells through a symplastic pathway driven by simply diffusion
32
Q

what is active phloem loading

A
  • movement of sugars from the mesophyll cells of the leaf to the phloem cell against a concentration gradient through the spending of ATP
  • sugars travel by the symplastic pathway until the cell layer before the companion cell
33
Q

what happens in active phloem loading

A

ATP powered protons pumps create a proton gradient

sucrose is cotransported with protons as they move down their concentration gradient

34
Q

what is polymer trapping

A

how some plants can move sucrose agaisnt a concentration gradient without the need for membrane transporters

35
Q

what happens in polymer trapping

A

concentrating sucrose by converting it to different, larger, sugar polymers

36
Q

what is an intermediary cell

A

special type of parenchyma cell where sugars are concentrated

37
Q

what are the steps of sugar transport in polymer trapping

A
  • sugars move into the intermediary cell through symplastic active transport
  • sucrose is actively combined with other sugars to form larger sugar polymers
  • polymers too large move back into the mesophyll cell
38
Q

what is symplastic

A

when something moves with the concentration gradient

39
Q

what is apoplastic

A

when something moves agaisnt the concentration gradient

40
Q

what is phloem unloading

A

the process of unloading sugars to the sink parnchyma cells from the phloem cells

41
Q

when is phloem unloading passive

A

in young leaves, actively growing tissues, roots

42
Q

when is phloem unloading active

A

in storage

43
Q

once in the phloem cells, how does sugar move in the vasculature

A

with pressure flow

44
Q

what is pressure flow hypothesis

A

a combination of osmosis, concentration gradients, water pressure and water movement in the xylem

45
Q

steps of pressure flow

A
  • phloem loading (high concentration of sucrose in the phloem)
  • water pulled from xylem into phloem
  • increased water pressure in cell
  • water moves to area of lower pressure through bulk flow (source to sink)
  • phloem unloading (reduces sucrose concentration in phloem
  • water moves back to xylem through transpiration
46
Q

what directions can water flow in the xylem and phloem in pressure flow hypothesis

A

same direction
opposite direction

only 1 direction in phloem even i it can do both

47
Q

why dont we expect water to flow toward the source

A

water along with solutes moves down the pressure gradient and not the potential gradient

48
Q

how is sucrose transported to seeds/flowers

A

water pressure in the source region of the phloem drives the movement of sucrose into the developing seeds or flowers

Organism 1 Finals (21 decks)

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