Question

In a ring girdled plant
A. The shoot and root die together.
B. Neither root nor shoot will die.
C. The shoot dies first.
D. The root dies first.

Answer 1

Hint: Ring girdling process involves complete removal of the bark from stem’s circumference. In addition to the bark, the phloem vessels are also removed. As a result, the plant has continuous xylem vessels and interrupted or broken phloem due to ring circumcision on the stem part.

Complete answer:
Phloem is a vascular tissue of the plants and mainly transports the nutrients (food or energy sources) from food stores of the plants to its different parts (or organs) including roots, stems, and reproductive tissues. Therefore, the transport of various materials in phloem is usually bidirectional including towards the upper parts as well as lower parts of the plants. This helps ensure the supply of nutrients from photosynthetic sites (leaves) to other plant parts where photosynthesis does not occur normally.
On ring girdling, the bark and phloem part of the stem is being removed. As a result, the movement of nutrients and other minerals from shoot part to root part of the plant does not occur. Hence, the root cells and tissues starve due to prolonged unavailability of food for their survival. This would further lead to death of cells and tissues of roots after some period of time. Therefore, the root dies first in a ring girdled plant.

The correct answer is option D, stating “The root dies first”.

Note:
Xylem is another vascular tissue of plants, but it carries the water and other minerals (absorbed from the plant roots) towards the shoot of a plant. Hence, the movement of materials in xylem is always unidirectional (that is, from roots towards the shoot). Ring girdling does not cause removal of xylem, and thus, the water and other minerals are continuously absorbed by roots and supplied to leaves (where photosynthesis usually occurs). This keeps the shoot alive for a certain period of time, however death of root is then followed by death of the shoot.