Parenchyma Cells: Structure, Types and Functions

Parenchyma cells are living cells that are mainly composed of nuclei and protoplasts. Their primary functions include storage and photosynthesis.

• Parenchyma is a simple permanent tissue that makes up the majority of ground tissues in plants and is embedded with other tissues such as vascular tissues.
• They are non-vascular and are made up of simple, living, undifferentiated cells that have been modified to perform various functions.
• Parenchyma can be found in the soft parts of plants, such as the Mesophyll in leaves, fruits, flowers, and young stems.
• It is also present in the stem and leaves, as well as the ground tissue. 

Key Terms: Parenchyma cell, Photosynthesis, Tissues, Pith, Cortex, Shape of Parenchyma cell, Endosperm, Chlorophyllous, Vacuoles, Plastids, Chloroplasts, Chlorenchyma

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What are Parenchyma Cells?

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Parenchyma is a form of tissue consisting of cells that carry out an essential function. Parenchyma, the simple permanent ground tissues, form the bulk of the plant tissues, such as fruit pulp, the tender part of leaves, and other plant organs.

• Parenchyma cells generally come in a variety of shapes, including spherical, oval, round, polygonal, and elongated.
• Their cellulose-based walls are quite thin and might be densely packed or have little intercellular space.
• Photosynthesis, storage, and secretion are all activities performed by the parenchyma tissue.

Parenchyma Cells

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Characteristics of Parenchyma Cells

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The following are the characteristics of Parenchyma cells

Origin of Parenchyma Cells

The ground meristem gives rise to the parenchyma cells that make up the main plant body, such as the pith and cortex. The major and secondary conducting tissues' xylem and phloem parenchyma are produced by the procambium and cambium, respectively.

Fragmentation of Parenchyma Cell In Tissue

Parenchyma tissue covers a large portion of all plant organs. Parenchyma cells are living tissues that can divide when they reach maturity. As a result, the needed help in tissue regeneration and repair is provided.

The shape of the Parenchyma Cell

The growth of parenchyma cells generally grows spherical. Due to interaction with surrounding cells, cell aggregates are polygonal and make it into a parenchyma tissue. The most frequent polyhedral cells have fourteen sides, however, cells with 12, 13, 15, 16, or fewer sides can also be found.

Intercellular Space

Mature parenchyma tissues can be packed tightly together with no intercellular gaps between them like endosperm tissue present in seeds. They can also be loosely organized so that well-developed intercellular gaps exist between them.

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Structure of Parenchyma Cells

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Primary walls are common in parenchyma cells i.e., chlorophyllous and storing parenchyma. The storing parenchyma cells of Phoenix, Asparagus endosperm have extremely thick walls.

• Hemicellulose deposition is responsible for the thickness of the wall.
• A living protoplast with one or more vacuoles is usually seen in parenchyma cells.
• They might also contain leucoplasts, chloroplasts, and other plastids.
• The cell sap of parenchyma contains a variety of carbohydrates, nitrogenous, and fatty compounds.
• In the cell sap of sugar beetroots and onion bulb scales, amides, proteins, sugars, and other compounds can be found.
• Protein and starch are found in the parenchyma cells of many leguminous plants' cotyledons.
• Protein and oils are found in the parenchymatous endosperm of Ricinus communis.
• The parenchyma of the potato tuber contains protein and carbohydrates.
• Starch can be found in the endosperm parenchyma, tubers, cortex, fruits, xylem, and phloem, among other places.
• Water can be found in the parenchyma of storage organs and succulents.

Structure of Parenchyma Cells

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Types of Parenchyma Cells

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The different types of Parenchyma cells are

Chlorenchyma

The mesophyll part of the leaves contains chlorenchyma. Chloroplast can be found in these parenchymal cells. Furthermore, these cells can be discovered in the immature plant cortex of the plant's stem.

• Multiple intercellular gaps are present in these cells, which are loosely packed.
• The stem and aerial roots of plants get their green color from chlorenchyma cells.
• The job of these parenchymal cells is to manufacture food through the process of photosynthesis.

Chlorenchyma

Aerenchyma

The parenchymal tissues are most commonly seen in aquatic plants, where they help the plants maintain their buoyancy.

• These parenchymal cells are loosely packed cells with wide intercellular gaps where air holes or air pockets exist, providing the plant with the necessary buoyancy.
• The plant can also use the gases (oxygen or carbon dioxide) trapped in the aerenchyma.

Aerenchyma

Xylem Parenchyma

The cellulose-based cell walls of xylem parenchyma cells are alive and thin-walled.

• They store carbohydrates, fat, and other compounds such as tannins in the form of food.
• The ray parenchymatous cells transport water in a radial direction.

Xylem Parenchyma

Phloem Parenchyma

Elongated, tapering cylindrical cells with dense cytoplasm and nucleus together makeup phloem parenchyma tissue. Cell walls are made of cellulose and have pits through which plasmodesmata connect between cells.

• The phloem parenchyma stores food material and other substances like resins, latex, and mucilage.
• Phloem parenchyma is absent in most of the monocotyledons.

Phloem Parenchyma

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Functions of Parenchyma Cells

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The following are the functions of Parenchyma cells

• All metabolic processes take place in living parenchyma cells.
• Chlorenchyma, or parenchyma cells with chloroplastids, can photosynthesize.
• Meristematic parenchyma can divide cells and so aids in wound healing and regeneration.
• In aquatic plants, aerenchyma, or parenchyma cells that surround the air gaps, aid in aeration, gaseous exchange, and buoyancy, which aids in floating.
• Epidermal parenchyma tissues with their cutinized peripheral walls of various plant organs aid in protection.
• Turgid parenchyma cells provide mechanical stiffness to seedlings and certain hydrophytes.
• Parenchymal tissues are also responsible for the buoyancy of some aquatic plants.
• Storage of elastic materials such as resins, etc.
• Water and nutrients are transported throughout the plant via parenchymal cells in the xylem and phloem.
• The capacity to develop into secondary meristematic cells is present in these cells (for example, cork cambium).
• All meristematic cells are parenchymal cells, it is crucial to remember this.

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Things to Remember

• Parenchyma is a form of tissue consisting of cells that carry out an essential function.  
• Primary walls are common in parenchyma cells i.e., chlorophyllous and storing parenchyma.
• The storing parenchyma cells of Phoenix, Asparagus endosperm have extremely thick walls. 
• The cell sap of parenchyma contains a variety of carbohydrates, nitrogenous, and fatty compounds.
• In the cell sap of sugar beetroots and onion bulb scales, amides, proteins, sugars, and other compounds can be found.
• Protein and starch are found in the parenchyma cells of many leguminous plants' cotyledons.
• The mesophyll part of the leaves contains chlorenchyma.
• Chloroplast can be found in these parenchymal cells.
• The parenchymal tissues are most commonly seen in aquatic plants, where they help the plants maintain their buoyancy.

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