Which of the following plant parts contains abundant sclerenchymatous fibres that provide mechanical strength and rigidity?

The correct option is Coconut husk.

Step-by-Step Explanation:

1. Understanding Sclerenchymatous Fibres:
Sclerenchyma is a type of simple permanent plant tissue specialized in providing mechanical strength, rigidity, and structural support to plants. Sclerenchymatous cells are dead at maturity, highly elongated with narrow lumina, and feature extremely thick cell walls hardened by heavy deposits of lignin (a tough chemical substance).

2. Structure of Coconut Husk:
The outer fibrous husk of a coconut is a classic example of tissue dominated by sclerenchymatous fibres. These dense, lignified fibrous bundles give the coconut husk its immense mechanical strength, toughness, and resistance to physical stress, protecting the inner seed.

3. Analysis of Other Options:
- Delicate petals of a flower: Petals are composed of thin-walled, living parenchyma cells designed for flexibility and soft texture, not mechanical rigidity.
- Growing tip of a root: The growing apex of a root consists of meristematic tissue, which is composed of thin-walled, actively dividing cells.
- Soft fleshy pulp of a ripe fruit: The fleshy edible portion of fruits primarily contains soft, living parenchyma tissue specialized for food and water storage.