Investigating Transport in Plants

Question 1

What is the use of ringing experiments to investigate transport in plants?

Answer 1

-Ring of bark is removed
-Sugars of the phloem accumulate above the ring, leading to swelling in this region
-Interruption of flow of sugars to the region below the ring and the death of tissues in this region

Question 2

Describe the use of tracer experiments to investigate transport in plants.

Answer 2

-Radioactive isotopes are useful for tracing the movements of plants
-Radioactive sugars can be traced using autoradiography
-Taking cross sections of film allows use to see the movement of sugars

Question 3

What is the evidence that translocation of organic molecules occurs in phloem?

Answer 3

-When phloem is cut, a solution of organic molecules flow out
-Plants with radioactive carbon dioxide can be shown to have radioactively labelled carbon in phloem after a short time
-Aphids have organic molecules in their needle-like mouthparts, and they remove the contents of sieve tubes
-Removal of a ring of phloem from around the whole circumference of a stem leads to the accumulation of sugars above the ring and their disappearance from below it