Introduction:
Girdling, also known as ring barking, is an experimental technique used to study the movement of nutrients in plants. It involves removing a ring of bark from the main stem or branch, resulting in the interruption of the flow of nutrients and water. This disruption eventually leads to the death of certain parts of the plant. Let's explore which part of the plant dies first in a girdling experiment and the reasons behind it.

Reasons behind plant death:
When a plant is girdled, the flow of nutrients and sugars from the leaves to the roots is hindered. This occurs because the phloem, the tissue responsible for transporting sugars and other organic molecules, is located just beneath the bark. Girdling effectively severs the phloem, preventing the downward movement of sugars and nutrients. As a result, the plant suffers from an imbalance between the production of sugars in the leaves and the inability to transport them to the roots. This imbalance eventually leads to the death of specific plant parts.

Order of plant death:
1. Roots: The roots are the first to die in a girdling experiment. Since the phloem is disrupted, the roots no longer receive the essential sugars and nutrients necessary for their survival. As a result, the roots gradually wither and die due to starvation.
2. Shoot tips: After the roots, the shoot tips begin to die. As the downward movement of sugars is halted, the shoot tips do not receive an adequate supply of nutrients. Over time, these parts become weakened and eventually perish.
3. Branches: The branches are the next to be affected. Without a continuous supply of sugars and nutrients, the branch tissues start to deteriorate. The lack of essential resources leads to the death of branches, which may become dry and brittle.
4. Leaves: Lastly, the leaves of the girdled plant begin to die. As the nutrients cannot be transported downward, the leaves lose their vitality and eventually turn yellow or brown. Without sufficient sugars and nutrients, the leaves cannot sustain themselves and ultimately perish.

Conclusion:
In a girdling experiment, the roots of a plant are the first to die, followed by the shoot tips, branches, and finally, the leaves. This order of plant death can be attributed to the interruption of phloem transport, which prevents the downward movement of sugars and nutrients. The plant parts that are the farthest away from the site of girdling, such as the leaves, are the last to be affected. Girdling experiments provide valuable insights into the importance of phloem in nutrient distribution and plant survival.