Explanation:

In a ring-girdled plant, the correct answer is option 'C', which states that the root dies first. This phenomenon occurs due to the disruption of the vascular system of the plant caused by ring girdling.

Ring Girdling:
Ring girdling is a process in which a ring of bark is removed from the stem or trunk of a plant, resulting in the disruption of the vascular tissues present in the bark. The vascular tissues, specifically the phloem, are responsible for transporting sugars and other nutrients from the leaves to the roots and other parts of the plant.

Effects of Ring Girdling:
When a plant is ring girdled, the following effects take place:

1. Interruption of Nutrient Flow: The removal of the bark ring interrupts the flow of sugars and nutrients from the leaves to the roots. This disruption prevents the roots from receiving essential nutrients, causing them to eventually die.

2. Accumulation of Sugars: As the flow of sugars from the leaves to the roots is blocked, the sugars start to accumulate above the girdle. This accumulation can lead to imbalances in the plant's metabolism and affect various physiological processes.

3. Starvation of Roots: With the disruption of nutrient flow, the roots are deprived of essential sugars and nutrients required for their survival. As a result, the root system weakens and eventually dies.

4. Shoot Survival: In a ring-girdled plant, the shoot initially continues to receive sugars and nutrients from the leaves through the xylem. Since the xylem is responsible for water and mineral transport, it remains intact even after ring girdling. Therefore, the shoot can survive for a certain period until the accumulated sugars are depleted.

5. Shoot Death: Eventually, as the accumulated sugars are used up and the root system dies, the shoot also starts to deteriorate and eventually dies. Without a functional root system, the shoot cannot obtain water and essential minerals, leading to its death.

Conclusion:
In summary, in a ring-girdled plant, the root dies first due to the disruption of nutrient flow caused by the removal of the bark ring. The shoot, although initially surviving due to the continued supply of sugars from the leaves, eventually dies once the accumulated sugars are depleted and it becomes deprived of water and essential minerals.