Collenchyma vs Sclerenchyma
There are 3 types of ground tissues in plants. They are parenchyma, collenchyma and sclerenchyma. Parenchyma cells are the generalized plant cell type and are the bulk of ground and vascular tissues. They are alive at maturity and function in photosynthesis and storage.
Collenchyma cells bear a strong resemblance to parenchyma. However, they have some distinguishing traits. They occur in groups just beneath the epidermis. They have a primary cell wall, which contains a lot of pectin. Thus, they stain pink with Toluidine blue. The cell wall is unevenly thickened. Collenchyma cells support the plant. These cells are characterized by thickening of the cell wall, and they are alive at maturity. 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 tangial walls.
Collenchymas cells are elongated typically with some overlap at their end walls. Collenchymas are always living. These are elongated cells, angular in T.S, and secondary deposition of cellulose can be seen. They usually occupy a peripheral position. Cells are plastic and elastic. They combine tensile strength with flexibility and plasticity. It is the first supporting tissue that appears in a growing plant. Thickened part of cell wall provides support, and thinner parts permit stretching and growth of cells and solute transfer across the wall. Walls are rich in water. Glisten in fresh sections. Cells are closely packed but sometimes intercellular air spaces can be seen. They occur as strands or continuous cylinders in the plant body and uncommon in roots.
Secondary wall is deposited after the cell has ceased enlargement. Parenchyma cells eventually develop into sclerenchyma cells. However, this is not usually the case. The distinguishing features of sclerenchyma are the presence of a thick secondary wall, which has highly organized cellulose micro fibrils and usually contains lignin.
Sclerenchyma cells support the plant and occur as bundle cap fibres, individual cells or group of cells. Thickenings in their secondary walls are a characteristic of sclerenchyma cells. They become dead at maturity. They stain red in many commonly prepared slides. They occur at the cortex, phloem, xylem, bundle sheath, and hypodermis. Wood fibres are absent in gymnosperms and lower vascular plants. Fibres outside the xylem are called extraxylary fibres, and they are found mainly in the phloem and the cortex.
There are two types of sclerenchyma. They are sclereids and fibres. Sclereids occur alone or in small clusters, and usually isodiametric although some can be very long. Sclereid has prominent pits and is generally lignified. Fibres are highly elongate and have overlapping end walls. Pits are few and small. They occur in bundles.
What is the difference between Collenchymas and Sclerenchyma?
• Collenchymas are living cells and sclerenchymas are dead cells.
• Wall of collenchymas contains mainly cellulose and wall of sclerenchyma contains mainly lignin.