Correct Option
When the bark of a tree is removed in a circular fashion around its base, a process known as girdling or ringing, the phloem tissue is disrupted. Phloem is located in the inner bark and is responsible for the translocation of sugars (food) produced during photosynthesis in the leaves to the roots and other non-photosynthetic parts of the plant. With the phloem pathway interrupted, the roots are deprived of the necessary energy supply for their metabolic activities, growth, and maintenance. Consequently, the roots starve and die, leading to the eventual death of the entire tree, even though the xylem (which transports water) may remain functional for some time.
Incorrect Options
- Option 1: The xylem tissue, responsible for water transport from roots to aerial parts, is located deeper within the stem, inside the phloem. Girdling primarily removes the bark and phloem, leaving the xylem initially intact. Therefore, water transport is not immediately affected, although it will cease once the roots die.
- Option 3: While an open wound created by girdling could potentially lead to microbial infection, the primary and direct cause of the tree's death in this scenario is the physiological disruption of nutrient transport to the roots, leading to their starvation and subsequent failure.
- Option 4: Roots obtain oxygen for respiration from the air spaces within the soil. The removal of bark does not directly impede the supply of oxygen from the soil to the roots. Oxygen availability to roots is largely independent of the bark's integrity.