Translocation Questions

Question 1

Carbon dioxide containing radioactive carbon was supplied to the leaf of a plant.

a) Radioactive carbon atoms will be detected in the phloem. Explain why.
b) Describe how you could use this investigation to show that sucrose can move both up and down the plant.

Answer 1

a) The carbon dioxide will be used in photosynthesis to make glucose. Some of the glucose will be converted to sucrose which is transported around the plant in the phloem.
b) This will be shown if radioactivity can be detected both above and below the leaf being supplied with CO2.

Question 2

An aphid is an insect pest that inserts needle-like mothparts into the veins of a plant. It feeds on sugars.
Explain which tissue in the veins the aphid feeds from.

Answer 2

From the phloem, because dissolved sugars are transported around the plant in phloem

Question 3

A young potato plant grows rapidly during the spring and summer, but in the autumn develops new potatoes, which are storage organs.

Compare the direction of movement of sucrose in the plant at different times of the year.

Answer 3

Sucrose is made in the leaves after photosynthesis. In the spring and summer most of the sugars will be transported in phloem to the growing parts of the plant, such as the tips of shoots and roots.

In the autumn, less sucrose will be transported to these growing parts and more will be transported to the potatoes for storage.

Question 4

Name the two transport systems found in plants.

Answer 4

phloem tubes and xylem vessels