Translocation: Source to Sink.

Created by: rachel
Created on: 13-02-13 20:33

Give an example of a plant making an organic compound(s)

A plant making sucrose for the transport of energy.

1 of 9

How do leaves make sucrose?

Leaves make sucrose from the sugars they produce in photosynthesis.

2 of 9

Sucrose travels from the ________ cells, where it's made, to the _____ cells, which pump it across their membranes & then it passes into _____ ______ ________ through plasmodesmata.

Mesophyll, companion, sieve tube elements.

3 of 9

What does the accumulation of sucrose do to the water potential inside the seive tube elements? What is the result of this?

lowers the water potential inside the sieve tube elements so water flows in from surrounding cells by osmosis. Hydrostatic pressure then builds up inside phloem sieve tubes & forces sugary sol'n from cell to cell through sieve tubes away from leaves

4 of 9

Phloem sap travels from the _______ to the meristems (growth areas), roots, new leaves, ________, fruits & seeds. What happens at these sinks & what happens to the pressure gradient?

leaves, flowers. At these sinks, sucrose & other assimilates are removed from the sieve tubes, which lowers the hydrostatic pessure - this maintains a pressure gradient from source to sink.

5 of 9

True or False: Phloem sap may move in opposite directions in adjacent sieve tubes, unlike the flow of water in xylem which is always one-way. Upwards from roots to leaves.

True.

6 of 9

What is the evidence that the mass flow in phloem is maintained by an active mechanism

rate of flow = higher than accounted for by diffusion. - Compan. cells & sieve tube e. have mitochondria & use ATP to drive pumps to move sucrose. Achieve this by pumping H+ out cell. H+ diffuses back in cell through carrier protein (transport sucros

7 of 9

Why have some scientists questioned the active mechanism?

Because some protein fibres within sieve tubes have no function in mass flow process.

8 of 9

What is translocation?

The movement of assimilates between sources (eg. leaves & storage organs) to sinks (eg. roots), where they are used.

9 of 9

Other cards in this set

Card 2

Front

How do leaves make sucrose?

Back

Leaves make sucrose from the sugars they produce in photosynthesis.

Card 3

Front

Sucrose travels from the ________ cells, where it's made, to the _____ cells, which pump it across their membranes & then it passes into _____ ______ ________ through plasmodesmata.

Back

Card 4

Front

What does the accumulation of sucrose do to the water potential inside the seive tube elements? What is the result of this?

Back

Card 5

Front

Phloem sap travels from the _______ to the meristems (growth areas), roots, new leaves, ________, fruits & seeds. What happens at these sinks & what happens to the pressure gradient?

Back

View more cards

Similar Biology resources:

See all Biology resources »

See all DNA, genetics and evolution resources »

Get Revising

Translocation: Source to Sink.