Tracer & Ringing Experiments

Question 1

Tracer and ringing experiments have been used to investigate mass transport in plants
It is described as a ringing experiment because it involves the

Answer 1

removal of a ring of surface tissues from the stem of the plant while leaving the stem core intact

Question 1

step 1
As the phloem is located towards the outside of the stem and the xylem towards the centre, the ring removes the …..only with the …….remaining intact

the site of ringing is often shown on diagrams as a small black bar dividing the stem

Answer 1

phloem

xylem

Question 2

step 2 After the ringing has been done the plant can then be exposed to a radioactive tracer so that

Answer 2

the direction and rate of translocation can be investigated

Question 3

step 3 14CO2 is commonly used for these experiments as it is

Answer 3

readily absorbed by the leaves and used in photosynthesis to produce sucrose

Question 4

step4The sucrose formed will be radioactive so its subsequent movement around the plant via translocation can be ………..

Answer 4

traced

Question 5

The amounts of radioactive carbon present in different parts of the plant can be detected
If the mass flow hypothesis is correct then

Answer 5

bulk flow of phloem sap should be in one direction (from source to sink) and occur at the same rate in any sieve tube at the same time

Question 6

As leaves are the site of photosynthesis they are the source tissue, sink tissues can be above or below the leaves
If the xylem is damaged during the ringing process the plant will not have and adequate supply of … and will

Answer 6

water

wilt