Investigating Transport In Plants

Question 1

What’s the ringing experiment

Answer 1

A section of outer layers is removed around the complete circumference of a woody stem while it is attached to the rest of the plant

Later, the region of the stem immediately above the missing ring of tissue is seen to swell

Samples of the liquid that had accumulated in the swollen region are found to be rich in sugars and other dissolved organic substances

Question 2

What do the observations suggest that removing the Phloem around the stem lead to?

Answer 2

The sugars of the phloem accumulating above the ring, leading to swelling in this region

The interruption of flow of sugars to the region below the ring and the death of tissues in this region

Question 3

What’s the conclusion from the ring experiment

Answer 3

Phloem rather then xylem is the tissue responsible for translocation for sugars in plants

Question 4

Describe the tracer experiments

Answer 4

This can be done by supplying part of a plant with an organic substance that has a radioactive label. One example is co2 contain the radio active isotope 14C. This radioactivity labelled co2 can be supplied to a single leaf by being pumped into s container which completely surrounds the leaf

The radioactive carbon will then be incorporated into organic substances produced by the leaf, which will be moved around the plant by translocation

The movement of these substances can be tracked using a technique called autoradiography. To reveal when the radioactive traced has spread to in a plant, the plant is killed and then the whole plant is placed on photographic film - the radioactive substance is present wherever the film turns black

Question 5

What do the results of the tracer experiment demonstrate

Answer 5

The translocation of substances from source to sink over time e.g. autoradiographs of plants killed at different times show an overall movement of solutes from the leaves toward the roots