Translocation

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What is translocation?
A precess which moves organic compounds from a source to a sink (the tissues that need them)
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What is the name given for the products of photosynthesis needed to be transported?
Assimilates
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What is the main assimilate transported in the phloem?
Sucrose (disaccaride)
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Name 3 main sources of assimilates
1) Leaves and stem, 2) tubers and tap roots, 3) Food stores in seeds
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Name 3 main sinks of assimilates
1) Roots, 2) Meristems (actively dividing), 3) Any part of the plant that is laying down food stores
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What is phloem loading?
Assimilates moving into the phloem
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Describe the movement of sucrose into the phloem in the symplast route
The sucrose moves through the cytoplasm of mesophyll into the sieve tubes by diffusion through the plasmodesmata. Water follows, increasing the pressure and moving the sucrose along
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Describe the movement of sucrose into the phloem in the apoplast route
Water moves to the companion cells through cell wall and intracellular gaps down a conc grad, CC actively pumps out H ions and then the H ions return through co-transport proteins with sucrose being the co-transporter
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Name 2 ways companion cells have adapted to help in phloem loading
Folded membrane (larger SA, more diffusion for sucrose), lots of mitochondria (produce ATP for transport pumps)
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How does the assimilates travel through the phloem to the sinks?
The build up of sucrose means more water moves in, increases turgor pressure, moving the assimilates by mass flow. The solute accumulation results in the turgor forcing sap into regions of lower conc (the sinks)
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What is phloem unloading?
The unloading os assimilates into the sinks
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How is sucrose unloaded with the conc grad maintained?
Sucrose moves out of the phloem at any point by diffusion into surrounding cells, to maintain the grad, the sucrose quickly moves on to other cells or is converted into another substance
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Give 2 examples of what the sucrose could be converted into
Glucose (for respiration), Starch (for storage)
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What happens to the water?
Water moves out of the surrounding cells and is drawn into the transpiration stream in the xylem
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Other cards in this set

Card 2

Front

What is the name given for the products of photosynthesis needed to be transported?

Back

Assimilates

Card 3

Front

What is the main assimilate transported in the phloem?

Back

Preview of the front of card 3

Card 4

Front

Name 3 main sources of assimilates

Back

Preview of the front of card 4

Card 5

Front

Name 3 main sinks of assimilates

Back

Preview of the front of card 5
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