Difference Between Fibres and Sclereids

The main difference between fibres and sclereids is that fibres are unbranched, elongated cells whereas sclereids are short, isodiametric or irregular cells that may be branched or unbranched. Moreover, fibres have tapering end walls while the end walls of the sclereids are blunt.  

Fibres and sclereids are two types of sclerenchyma cells that differ in shape. Fibres originate from meristematic cells while sclereids are formed by the secondary wall thickening of parenchyma cells. 

Key Areas Covered 

1. What are Fibres
      – Definition, Shape, Function
2. What are Sclereids
     – Definition, Shape, Function
3. What are the Similarities Between Fibres and Sclereids
     – Outline of Common Features
4. What is the Difference Between Fibres and Sclereids
     – Comparison of Key Differences

Key Terms

Aastrosclereids, Brachysclereids, Fibres, Macrosclereids, Oosteosclereids, Parenchyma, Sclereids, Sclerenchyma, Xylem 

What are Fibres 

Fibres are thick, elongated, spindle-shaped cells with pointed tips. The lumen of fibres is narrow and contains simple, rounded pits. The secondary cell wall is lignified. Typically, fibres occur in the cortex, pericycle, xylem, and phloem. The main function of fibres is to provide the mechanical strength to the plant while aiding in the dispersal of seeds and fruits.  

The three types of sclerenchyma fibres are surface fibres, xylary or wood fibres, and extraxylary or bast fibres.  

1. Surface fibres – Found in the seed coat (coconut) and fruit wall 
2. Xylary or wood fibres – In the xylem 
3. Extraxylary or bast fibres – Associated with cortex, pericycle, phloem 
   

   Figure 1: Sclerenchyma Fibres

What are Sclereids 

Sclereids refer to the sclerenchyma cells with highly-thickened lignified cell walls with a narrow lumen. They occur in the cortex, pith, pulp of fruits, and fruit walls. The four main types of sclereids are macrosclereids, osteosclereids,  astrosclereids, and brachysclereids. 

1. Macrosclereids – Rod-like sclereids found in the bark and the seed coat of the legumes
2. Osteosclereids – Bone-like sclereids with lobed ends; found in seed coat and fruit wall 
3. Astrosclereids – Star-shaped sclereids found in dicot leaves and gymnosperms
4. Brachysclereids – Isodiametric sclereids found in the cortex, pericarp of the coconut shell, pith; also called stone cells. Numerous stone cells present in the pulp of the fruit are called the grit cells.

Figure 2: Stone Cells

Similarities Between Fibres and Sclerenchyma 

• Fibres and sclereids are two types of sclerenchyma cells found in plants. 
• They are simple tissues that are nonliving. 
• The main function of both cells is to provide structural support to the plant. 
• The walls of both types of cells are thickened by the deposition of lignin. 
• Sclerenchyma cells occur in the hypodermis, vascular regions, cortex, stem, leaves, and fruit walls. 

Difference Between Fibres and Sclereids

Definition 

Fibres: Thick, elongated, spindle-shaped cells with pointed tips

Sclereids: Sclerenchyma cells with highly-thickened lignified cell walls having a narrow lumen

Shape 

Fibres: Elongated cells 

Sclereids: Broad cells with irregular shape 

End Walls 

Fibres: Tapering end walls 

Sclereids: Blunt end walls 

Branching 

Fibres: Unbranched 

Sclereids: Branched or unbranched 

Origin 

Fibres: From meristematic cells 

Sclereids: By the secondary wall thickening of parenchyma cells 

Organization 

Fibres: Generally occur in bundles 

Sclereids: Singly or loose groups 

Occurrence 

Fibres: Cortex, pericycle, xylem, and phloem 

Sclereids: Cortex, pith, pulp of fruits, and fruit walls 

Function 

Fibres: Provides mechanical strength 

Sclereids: Provides stiffness 

Conclusion 

Fibres are elongated cells while sclereids are broad cells. Both fibres and sclereids are sclerenchyma cells with a thick, secondary cell wall that is lignified. The main difference between fibres and sclereids is the shape of the cells. 

Reference:

1. “Different Types of Sclerenchyma -Fiberes and Sclereids and Their Function.” Difference between Dicot and Monocot Embryo, Available Here

Image Courtesy:

1. “Botana curus X dicot fibres 400×” By Kelvinsong – Own work (CC BY 3.0) via Commons Wikimedia
2. “Stone cells in Pyrus pear” By Berkshire Community College Bioscience Image Library (Public domain) via flickr