4.4.4 - Translocation Flashcards

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1
Q

Features of the structure of the phloem.

A

Made up of sieve tube elements
End walls are perforated to form sieve plates
Companion cells are associated with sieve tube elements

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2
Q

What is the place where sucrose is made?

A

Source

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3
Q

What is the place where sucrose is used?

A

Sink

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4
Q

What are 3 things that the phloem transports?

A

Sucrose
Amino acids
Inorganic ions

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5
Q

What is the first stage of the mass flow theory?

A

Sucrose is actively transported into the phloem, companion cells are involved.

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6
Q

What happens after sucrose moves into phloem by active transport?

A

Water potential is lowered.
Water moves in by osmosis from xylem.

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7
Q

What happens after water moves into phloem by osmosis?

A

Pressure increases
Causes movement towards sink

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8
Q

What is sucrose used for in the sink?

A

Respiration
Stored as starch

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9
Q

Why is sucrose stored as starch?

A

Sucrose is soluble in water so affects water potential.
Starch isn’t.

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10
Q

Evidence for mass flow theory.

A

There is a pressure within sieve tubes, shown by sap being released when cut.
Concentration of sucrose is higher in source than sink.

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11
Q

Evidence against mass flow theory.

A

Function of sieve plates in unclear, they would hinder mass flow.
Not all solutes move at the same speed - they should do if movement is by mass flow.

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