Question

Nina's backyard is adorned with a canopy of trees which she loves to watch. A few weeks back, her father had removed a ring of bark from one of the trees for his carpentry work. Nina noticed that the portion of the bark above the ring on the stem is now swollen. What could be the possible reason for this?

• A. Shrivelling of the tissues below the ring of bark
• B. Absence of downward movement of food
• C. Phloem layer is removed from the tree trunk
• D. All the above

Answer 1

The correct option is D All the above

When a ring of bark up to a depth of the phloem layer is removed from the trunk of a tree, the downward movement of food stops. In the absence of the downward movement of food, the portion of the bark above the ring on the stem becomes swollen after a few weeks. The tissues below shrivel showing the bark or phloem is involved in the movement of organic molecules. This shows that phloem is the tissue responsible for translocation of food. This has been proved by the girdling experiment conducted by Marcello Malpighi.
Thus Nina noticed the ring on the stem was swollen after her father had removed a ring of bark.