Introduction

Plant tissues are supportive and provide strength and support to the plants. Tissues are the fundamental components of any living body, whether it be an animal or a plant. An organism is made up of multiple tissues that come together. Individual cells make up tissues. A tissue is a collection of cells that have a similar structure and execute similar functions. 

Since most plants are fixed and stationary, they do not move around much, the plant tissues support the plants and offer structural strength. As a result, animal tissue differs significantly from plant tissue. We’ll learn more about plant tissues like chlorenchyma, and collenchyma in this article.

Collenchyma Cells

Bones provide support and structure to both humans and animals. Plants lack bones, but they do have a range of structural cells with various compositions and activities. 

Collenchyma cells are elongated cells that give support and structure and have irregularly thick cell walls. The compounds cellulose and pectin make up their thick cell walls. In young stems and leaf veins, these cells are frequently found beneath the epidermis, or outer layer of cells.

Function of Collenchyma Cells

• Collenchyma cells give structural support and serve as an inner foundation for the plant, similar to how bones protect humans and other animals. Plants face a variety of structural problems, and without these cells, most plants would be too sensitive to be damaged by heavy rains, high winds, and other pressures.
• Collenchyma cells have thicker walls that allow them to provide additional support to the locations where they are present. Most importantly, collenchyma cells sustain and fill in vacant spaces that will be used for future growth in growing sections of the plant, such as shoots and leaves.
• The collenchyma is one of the three basic types of tissues in plants. The parenchyma and sclerenchyma are the other two. The collenchyma’s cells have a thicker primary wall than the parenchyma, which distinguishes them from the other two. The collenchyma and parenchyma cells both have a single cell wall. 
• A secondary cell wall is deposited between the primary cell wall and the plasma membrane in sclerenchyma cells. Both the collenchyma and the sclerenchyma, however, are plant tissues that provide structural support. The sclerenchyma, on the other hand, gives a plant extra strength and structural support.
• The cells of the collenchyma are usually elongated. They are most commonly seen in the growing shoots and leaves. The strands in celery stalks are an example of collenchyma tissue. In contrast to sclerenchyma cells, which lose their protoplast at maturity, collenchyma cells are often alive at maturity.
• The cell walls of many collenchyma cells contain uneven thickenings. An angular collenchyma is formed when the main cell wall thickens at intercellular contact locations. An annular collenchyma is a type of collenchyma cell with evenly thickened cell walls.

Distribution

Collenchyma cells can be found in the rib of some leaves, as well as the periphery of herbaceous stems, petioles (e.g. Begonia), and the periphery of herbaceous stems (e.g. Nerium). They’re also found in the flowering sections, the fruit, and the aerial root (ex. Monstera). In dicotyledons, they frequently occupy the cortex’s periphery layers, and they may be found just beneath the epidermis or beneath a few peripheral layers of parenchyma.

They can generate hypodermis if they are present as a continuous layer. At the outside edges of stems (e.g. Leonurus, Cucurbita, etc.) and petioles, the cells can form distinct ribs or ridges (e.g. Apium). Roots, monocotyledonous leaves, and stems are all uncommon. Collenchyma can be found in the underground roots of Vitis and Diapensia. Vitis and Cassia tora have collenchymatous fruit rinds.

Origin

The ground meristem or the procambium give rise to collenchyma (e.g. Apium graveolens). They could potentially come from elongated cells that look like procambium.

Shape

Isolated collenchyma cells can be circular, elliptical, or elongated in shape. There are also transitional forms. The elliptical or round cells resemble ground parenchyma. The cells could take on the form of a short prism. The elongated cells have both ends tapered and can reach a length of 2 mm, however this is uncommon.

Types of Collenchyma

Angular

The thickening materials accumulate at the cell’s angles and corners. The thickenings can be seen in cross section at the points where many cells connect. Cucurbita, Beta, and other plant petioles are examples.

Lamellar

The thickening elements deposit more thickly on the cell’s tangential walls than on the radial walls, as in the case of stem of Sambucus.

Lacunar

The thickening materials collect in the areas of the cell wall that are directly in contact with the intercellular gaps. Salvia, Malva, and other plants’ petioles are examples.

Structure

High levels of pectin and hemicellulose thicken the walls. There’s also cellulose and protein. The primary pit fields are visible in the walls. Transversely oriented cellulose micro fibrils or alternatively transverse and longitudinally oriented cellulose micro fibrils as indicated by electron microscopy of the petiole of Apium graveolens, the longitudinal micro fibrils may alternate with no cellulosic components.

These alternating layers’ composition vary. One layer is high in cellulose and low in pectin, whereas the other is high in pectin and low in cellulose. The composition and direction of micro fibrils at alternate layers are now thought to be responsible for the apparent lamellation of the cell wall of collenchyma. Lignin is usually completely missing.

However, the cellulose-rich layer may be impregnated with lignin in rare situations (e.g. stem and petioles of Salvia officinalis, Viscum album, Medicago sativa etc.). The wall may also be covered by lignified lamellae. As a result, the collenchyma’s pecto-cellulosic wall may become sclerified.

Collenchyma is active with protoplasm. Some cells may also have chloroplasts. Tannins may also be present in the cells.

Function

• The cells are extendable and flexible, allowing them to support the organs in which they are found.
• Collenchyma-containing chloroplasts can do photosynthesis.
• In other circumstances, such as phellogen, the cork cambium, which divides to form the periderm, the peripheral thick walled collenchyma spreads and regains meristematic activity.
• The mechanical cell of mature plants is the sclerified collenchyma.
• Collenchyma can operate as a storage location for antibacterial chemicals that are used to fight bacteria. Solanum tuberosum agglutinins are hydroxyproline-rich bacterial agglutinins.

Conclusion

Bones provide support and structure to both humans and animals. Plants lack bones, but they do have a range of structural cells with various compositions and activities. Collenchyma cells are elongated cells that give support and structure and have irregularly thick cell walls. Collenchyma cells give structural support and serve as an inner foundation for the plant, similar to how bones protect humans and other animals. Plants face a variety of structural problems, and without these cells, most plants would be too sensitive to be damaged by heavy rains, high winds, and other pressures. High levels of pectin and hemicellulose thicken the walls. There’s also cellulose and protein. The primary pit fields are visible in the walls.