Parenchyma Plant Tissue

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What is Parenchyma Tissue?

Parenchyma is a form of simple permanent tissue that makes up a significant portion of plant-soil tissues, where other tissues are embedded, such as vascular tissues. These are non-vascular and consist of cells that are basic, living and undifferentiated and are configured to perform different functions.

The other types of simple permanent tissues are:

  • Collenchyma

  • Sclerenchyma

Parenchyma Tissue Diagram

Below is the given picture represents the parenchyma tissue diagram:

[Image will be uploaded soon]

Define parenchyma tissue along with its characteristics

  • They are permanent living tissues that have the capacity to split at maturity and assist in wound regeneration and healing.

  • As reproductive cells (spores, gametes) are parenchymatous in nature, parenchyma cells are the base of a plant.

  • A single parenchyma cell fertilized cell has the capacity to develop into an entire plant. These cells are termed as "totipotent" cells.

  • Parenchyma cells exist as homogeneous parenchyma tissues in the form of continuous masses, such as in the pith and cortex of stems and roots, flesh of succulent fruits, mesophyll of leaves and in the seed endosperm.

  • To form heterogeneous complex tissues such as xylem and phloem, parenchyma cells can be associated with other cell types.

  • Parenchyma cells are important for activities such as assimilation, photosynthesis, preservation, secretion, respiration, excretion, and radial transport as water and solvent.

Structure of Parenchyma Cells:

  • Parenchyma in plants is found to be a living cell.

  • It has a prominent protoplast and nucleus.

  • Parenchyma in plants cells is either polyhedral or isodiametric in shape. They can also be oval, polygonal, elongated or round.

  • Such cells are packed tightly or may have limited intercellular space.

  • They are built up of a thin cell wall which is mainly composed of cellulose, hemicellulose.

  • Cells of the parenchyma tissue are joined by plasmodesmata.

  • They've got some little vacuoles. Smaller vacuoles combine to become a large central vacuole in the older parenchyma, that might absorb anthocyanin or tannins.

  • In the vacuoles of the parenchyma cells that serve as a water source, water is plentiful.

  • In the endosperm of the date palm, storage parenchyma cells can have thick cell walls.

  • Flowers and fruits' also carry the parenchyma cells which carry chromoplasts.

  • Cells of parenchyma can have a thick lignified wall, making it difficult to distinguish it from sclerenchyma.

  • The hydraulic property of the cells gives mechanical strength to the parenchyma.

  • In the parenchyma tissue in plants, some cells which are specified to conduct photosynthesis, are observed to carry chloroplasts.

  • The parenchyma cells that are responsible for performing the role of secretory tend to have Golgi bodies, dense protoplasm which is rich in ribosomes, and a highly developed endoplasmic reticulum.

Types of Parenchyma Tissues with their Functions

Types of parenchyma tissue

Based on their form, location and functions carried out, parenchyma cells can be classified. The principle parenchyma plant tissue is:

1. Chlorenchyma: Chlorenchyma cells are the one which carries chloroplasts and are responsible for performing photosynthesis. 

  • They can also be termed as the mesophyll cells present in leaves and helps in differentiating between the palisade and spongy cells.

  • They can be seen in the green parts of the plants such as stems, sepal etc.

2. Transfer Cells: They play a significant role in the short-distance transmission of solutes.

  • They include cell wall ingrowths that substantially increase the plasma membrane surface area.

  • Sucrose is transported through a proton/sucrose cotransporter mechanism across the membrane.

  • These are found in those regions of plants where the processes like absorption and secretion occur. Examples of the same may include, nectaries, salt glands and in carnivorous plants.

3. Vascular Parenchyma: The vascular tissue-associated parenchyma cells. They can be of two kinds:

  1. Phloem Parenchyma: It consists of tapering, elongated, and cylindrical cells which carry dense cytoplasm.

  • Plasmodesmata associations occur between the cells via pits in the walls.

  • It stores foods such as resins, latex and mucilage, and other materials.

  • They are absent in monocotyledons.

  1. Xylem Parenchyma: It is composed of cells that are thin-walled. The wall of the cell is composed of cellulose.

  • Food products such as fats, starch and a few other substances like tannins and crystals are processed.

  • Radial water conduction occurs by ray parenchyma cells.

  • They help to avoid damage to tracheids and vessels in the water-stress state.

4. Storage Parenchyma: These store different compounds such as water, starch, proteins, etc. They serve as a reservoir for food and water.

  • For plants, stored protein is a better source of nitrogen.

  • Bountiful starch-containing amyloplasts are found in starch storing cells such as in cereal endosperm, potato tubers, and cotyledon.

  • Parenchyma cells are found to be specialized in water storage tissue in succulent plants.

5 . Prosenchyma: These are elongated fibre-like cells which are thick-walled and provide the plant with rigidity and strength.

6 . Aerenchyma: They contain very wide spaces that are intercellular. These are found in aquatic plants.  

  • Aerenchyma aids in the floating plants' buoyancy.

  • It helps with respiration and provides aquatic plants with ample oxygen.

  • The creation of aerenchyma takes place naturally in the rice roots (Oryza sativa).

7 . Epidermis Parenchyma: It is found in the epidermis of some gymnosperm leaves and tends to carry cutinized cell walls.

8 . Conjunctive Parenchyma: This form of parenchyma is observed in the root system. Further, they are found to be  Non-cutinized, mostly on the outer layer of the young parts of the root, and with a thin cell wall.  It is recognized as a piliferous layer or epilema.

Parenchyma Tissue Function

The ground tissue of plants is produced by Parenchyma cells. The tissues of parenchyma perform different significant functions. The list of parenchyma function is given below:

  1. Storage: 

  • There is a large intercellular space in Parenchyma cells that is suitable for storage.

  • High concentrations of starch are found in the potato and cassava tubers.

  • These can store fats, water, droplets of oil, and substances that are ergastic.

  • Storing water and serving as a source of water.

  1.  Transport: 

  • Nutrients and other chemicals are transported by Parenchyma cells.

  • Transfer cells have outgrowth to maximize surface absorption.

  1. Photosynthesis:

  • Chlorenchyma occurs in mesophyll as well as the other green parts of the plant, has chloroplasts and performs photosynthesis.

  1. Healing and Regeneration:

  • Parenchyma cells that maintain their ability to divide even at maturity help in wound healing and regeneration. Tyloses present in the parenchyma of xylem aid in the prevention of vascular tissue damage during drought.

FAQ (Frequently Asked Questions)

1. What are the Functions of Xylem and Phloem? 

Ans. One of the two types of transport tissues in vascular plants is Xylem, the other being phloem. Xylem's fundamental function is to carry water from the roots to the stems and leaves, but it also helps in the transport of nutrients. Phloem is the type of living tissue in plant species which transport the soluble organic compounds formed during photosynthesis to different parts of the plant. This method of transport is called translocation.

2. Give Different Types of Permanent Tissue.

Ans. Different types of Permanent Tissue are:

  • Simple Permanent Tissue

  • Complex Permanent Tissue 

  • Secretory Tissue