Sclerenchyma MCQ - Practice Questions with Answers

Simple Permanent Tissues: Sclerenchyma Fibres

• Sclerenchyma is the simple permanent tissue made up of thick-walled, lignified and dead cells.
• They have a secondary wall deposited with lignin which makes them devoid of protoplasm and dead.
• It consists of two types of cells: Fibres and Sclereids

Fibres:

• These are elongated cells with pointed needle-like ends called tapering ends.
• They are always dead at maturity.
• These originate from the procambium of apical meristem and from vascular cambium.
• Fibres can be classified on the basis of their position in the plant body as follows:

1. Intraxylary fibres: present in xylem (wood).
2. Extraxylary fibres: present outside the xylem, that is, in the phloem.

Intraxylary Fibres: these are of the following types:

• Libriform fibres: Thick-walled wood fibres have simple pits.
• Fibre Tracheids:  Thin-walled wood-fibres having bordered pits

Extraxylary Fibres: these have simple pits and are of the following types:

• Cortical fibres: these are present in the cortex
• Perivascular fibres: these are present in the periphery of vascular bundles
• Phonic fibres: these are present in the phloem

Functions of fibres: provide mechanical strength, maintain elasticity and are economically important.

Simple Permanent Tissues: Sclerenchyma Sclereids

Sclereids:

• These are non-prosenchymatous cells.
• They do not have pointed ends 
• They can originate in epidermal cells of leaves, in vascular bundles, in the periderm, in the seed coat, etc.
• These can be of the following types: 

1. Brachysclereids/Stone Cells: These are small and isodiametric in shape. They occur in the cortex, pith, phloem, and pulp of the Pyrus.
2. Macrosclereids:  These are rod-shaped or columnar sclereids. They occur in the leaves, cortex of stem, and testa of seeds.
3. Osteosclereids: These are bone-shaped sclereids dilated at their ends. They occur in the leaves and seeds of several monocots.
4. Astrosclereids: These are star-shaped. They occur in leaves of Nymphaea, Trochodendron, etc.
5. Trichosclereids: These are hair-like and branched. They occur in hydrophytes.

Functions of Sclereids: provide stiffness, mechanical strength, and protection.