Ringing involves removing a circle of the outer tissues from a plant stem. This removes the phloem but not the xylem. A scientist investigated the effect of ringing in one species of plant. Plant A was ringed and plant B was not ringed. Most of the leaves were removed from the plants. Plastic bags filled with carbon dioxide containing radioactive carbon (14C) were tied around the remaining leaves. After a set time, radioactive carbon (14C) was detected in different parts of the plants. Figure 3.1 is a diagram of the investigation and shows the results.

Figure 3.1, two potted plants, each with a leaf enclosed in a plastic bag with carbon dioxide containing 14C: plant A has a ringed stem below the bag, with 14C detected in the leaf and in the roots but no 14C detected in the top of the stem; plant B is not ringed, with 14C detected in the leaf, in the roots and in the top of the stem

Explain why radioactive carbon (14C) was found in the roots but not in the top of the stem in plant A.

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3(a)(ii)Experimental DesignMedium2 marks

Explain the purpose of plant B in Figure 3.1.

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3(b)Plant Structure TransportEasy2 marks

Explain the effect on the rate of transpiration of removing leaves from a plant.

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3(c)Plant Structure TransportMedium2 marks

Suggest the effect on the rate of transpiration of ringing a plant. Give a reason for your suggestion.

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3(d)Plant Structure TransportEasy1 mark

State the name of the structures in a leaf that contain phloem.

3(e)Plant Structure TransportEasy1 mark

State the name of a plant structure that contains lignin and cellulose.