Different Types of Sclerenchyma -Fiberes and Sclereids and their Function

Sclerenchyma: (Gk; Sclerous: hard; enchyma: infusion)

•       Non-living mechanical tissue

•       Thick walled, lignified and pitted cells without protoplasm at maturity

•       Distribution: cortex, hypodermis, vascular regions of stem, leaves, fruit wall etc

    1. Sclerenchyma Fibres

• Thick, elongated, spindle shaped cells with pointed tips.
• Narrow lumen with simple rounded pits and lignified secondary wall
• Distribution: cortex, pericycle, xylem and phloem

Types of Fibres:

• a. Surface fibres: found on fruit wall and seed coat (e.g., coconut)
• b. Xylary or Wood fibres: associated with xylem
• c. Extraxylary or Bast fibres: seen associated with cortex, pericycle and phloem

Function of Fibres:

• Provide mechanical support to the plant parts
• Surface fibres help in seed and fruit dispersal

      2. Sclereids

•       Small sclerenchymatous cells with highly thickened lignified walls and narrow lumen. 

      Distribution: pulp of fruits, fruit walls, cortex, pith etc

  Different types of Sclereids

•       a. Brachysclereids: isodiametric sclerieds called as stone cells

Grit cells: Numerous Stone cells present in the pulp of fruits (guava, sapota)

Distribution: cortex, pith, pericarp of coconut shell

•       b. Macrosclereids: rod like sclerieds- present in bark and seed coat of leguminous plants

•       c. Osteosclerieds: Bone like sclerieds with lobed ends-seed coat and fruit wall

•       d. Astrosclereids: star shaped sclerieds- dicot leaves and gymnosperms

Functions of Scelrenchyma

• Dead mechanical tissue providing strength and support to the plant
• Protects from damages
• Xylem fibres in water conduction
•  Fibrous sclerenchyma of fruits and seeds helps in seed dispersal.