The girdling or ringing experiment is that

Options

A. The metallic ring is tightly tied to a stem
B. The ring of tissue external to xylem is removed in a stem
C. The area is simply marked in the form of ring in a stem
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding the Girdling Experiment**: The girdling or ringing experiment is a method used to study the role of phloem in the transportation of food in plants. The objective is to demonstrate that phloem is responsible for transporting food produced by photosynthesis.

2. **Identifying Plant Tissues**: In plants, there are two main types of vascular tissues: xylem and phloem. Xylem is responsible for transporting water and nutrients from the roots to the rest of the plant, while phloem is responsible for transporting food (sugars) produced during photosynthesis.

3. **Procedure of Girdling**: In the girdling experiment, a ring of bark, which contains the phloem, is removed from the stem of a woody plant. This removal is done carefully so that the xylem tissue remains intact and undisturbed.

4. **Observation After Girdling**: After the girdling, the phloem is no longer able to transport food downwards to the parts of the plant below the girdle. As a result, the food produced by the leaves accumulates above the girdle, leading to swelling or accumulation of nutrients in that area.

5. **Conclusion**: The experiment clearly shows that phloem is essential for the translocation of food. The correct answer to the question is that the girdling or ringing experiment involves the removal of a ring of tissue external to the xylem in a stem.

### Final Answer:
The girdling or ringing experiment is that the ring of tissue external to xylem is removed in a stem.

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