The key difference between collenchyma and sclerenchyma is that collenchyma is a type of live plant cell that has irregularly thickened primary cell walls while sclerenchyma is a type of dead plant cell that has heavily thickened secondary walls.
There are three types of ground tissues in plants. They are parenchyma, collenchyma, and sclerenchyma. Parenchyma cells are the generalized plant cell and make up the bulk of ground and vascular tissues. They are alive at maturity and help in photosynthesis and storage. Collenchyma is another type of ground tissues that have irregularly thickened primary cell walls. Generally, they are also live cells that provide support and structure. The third type, sclerenchyma, are mainly dead cells that have heavily thickened secondary cell walls. They provide rigidity to the plant. This article will discuss the difference between collenchyma and sclerenchyma.
CONTENTS
1. Overview and Key Difference
2. What is Collenchyma
3. What is Sclerenchyma
4. Similarities Between Collenchyma and Sclerenchyma
5. Side by Side Comparison – Collenchyma vs Sclerenchyma in Tabular Form
6. Summary
What is Collenchyma?
Collenchyma cells bear a strong resemblance to the parenchyma. However, they have some distinguishing traits. They occur in groups just beneath the epidermis. Moreover, they have a primary cell wall, which contains a lot of pectins. Thus, they stain in pink with Toluidine blue. Furthermore, the cell wall of collenchyma cells is unevenly thickened. These cells are characterized by thickening of the cell wall, and they are alive, even at maturity, unlike sclerenchyma cells. Furthermore, they tend to occur as a part of the vascular bundles or on the corners of angular stems. The thickening can occur at the corners of adjacent cells or along the tangential walls.
Figure 01: Collenchyma Cells
Collenchymas cells have some overlaps at their end walls. These cells are always living cells. In addition, these are elongated cells and have secondary deposition of cellulose in the cell walls. They usually occupy a peripheral position. These cells are also plastic and elastic as they combine tensile strength with flexibility and plasticity. It is the first supporting tissue that appears in a growing plant. The thickened part of cell wall provides support, and the thinner parts permit stretching and growth of cells and solute transfer across the wall. Walls are rich in water; hence they glisten in fresh sections. Generally, collenchymas cells package closely. However, intercellular air spaces are sometimes visible among the cell. They occur as strands or continuous cylinders in the plant body. However, collenchymas cells are uncommon in roots.
What is Sclerenchyma?
Sclerenchyma tissue is the third type of ground tissues present in plants. They are mainly dead cells that provide support and rigidity to plants. In fact, it is the main ground tissue that supports the plant. Sclerenchyma cells cease cell enlargement. Afterward, secondary thickenings occur. Generally, sclerenchyma cells have heavily thickened secondary cell walls containing cellulose microfibrils and lignin. Hence they do not contain a cytoplasm or a nucleus. Eventually, they become dead and hard. Therefore, when staining, sclerenchyma cells appear in red as shown in figure 02.
Figure 02: Sclerenchyma Cells
Sclerenchyma cells support the plant and occur as bundle cap fibres, individual cells or group of cells. They occur mainly at the cortex, phloem, xylem, bundle sheath, and hypodermis. Wood fibres are absent in gymnosperms and lower vascular plants.
There are two types of sclerenchyma as sclereids and fibres. Sclereids occur alone or in small clusters, and are usually isodiametric although some can be very long. Sclereid has prominent pits and is generally lignified. Fibres are highly elongated and have overlapping end walls. Pits are few and small. They occur in bundles.
What are the Similarities Between Collenchyma and Sclerenchyma?
- Collenchymas and sclerenchyma are two types of plant cells.
- Both types of cells support the plant mechanically.
- Also, both their cell walls contain cellulose.
What is the Difference Between Collenchyma and Sclerenchyma?
Collenchyma cells are elongated plant cells that have irregularly thickened primary cell walls while sclerenchyma cells are dead plant cells that have heavily thickened secondary cell walls. Thus, we can consider this as the key difference between collenchyma and sclerenchyma. The functional difference between collenchyma and sclerenchyma is that the collenchyma tissue provides mechanical support and elasticity to plants while sclerenchyma tissue provides mechanical support and rigidity to plants.
Furthermore, the collenchyma cells are living cells and contain cytoplasm and a nucleus. On the other hand, sclerenchyma cells are dead cells that lack a cytoplasm and a nucleus. Thus, it is another difference between collenchyma and sclerenchyma. Moreover, a further difference between collenchyma and sclerenchyma is that the collenchymas cells have chlorophylls and are able to carry out photosynthesis while sclerenchyma cells are unable to carry out photosynthesis as they do not have chlorophylls.
Below infographic summarizes the difference between collenchyma and sclerenchyma.
Summary – Collenchyma vs Sclerenchyma
Collenchyma and sclerenchyma are two types of plant ground tissue cells. Collenchyma cells are elongated sub-epidermal cells with irregularly thickened cell walls. On the other hand, sclerenchyma cells are the principal supporting cells which have heavily thickened secondary cell walls. Cell walls of collenchyma cells have cellulose and pectin while cell walls of sclerenchyma cells have cellulose, hemicelluloses, and lignin. Moreover, collenchyma cells are living cells while sclerenchyma cells are dead cells. Furthermore, collenchymas cells contain a cytoplasm and a nucleus while sclerenchyma cells do not. Thus, this summarizes the difference between collenchymas and sclerenchyma.
Reference:
1. “Collenchyma Cells: Function, Definition & Examples” Study.com, Available here.
2. “Ground Tissue.” Wikipedia, Wikimedia Foundation, 9 Feb. 2019, Available here.
Image Courtesy:
1. “Herbaceous Dicot Stem: Collenchyma, Sclerenchyma and Parenchyma in Cucurbita” By Berkshire Community College Bioscience Image Library (Public Domain) via Flickr
2. “Angiosperm Morphology: Sclerenchyma Cap and Starch Sheath in Yucca” By Berkshire Community College Bioscience Image Library (Public Domain) via Flickr