Key Functions and Roles of Parenchyma in Plants
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:
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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 plant 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 that 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 Tissue
Based on their form, location and functions carried out, parenchyma cells can be classified.
The principle parenchyma plant tissue is:
Chlorenchyma: Chlorenchyma cells are the one that carries chloroplasts and are responsible for performing photosynthesis. They can also be termed as the mesophyll cells present in leaves and help in differentiating between the palisade and spongy cells. They can be seen in the green parts of the plants such as stems, sepal etc.
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 carnivorous plants.
Vascular Parenchyma: The vascular tissue-associated parenchyma cells. They can be of two kinds:
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.
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.
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.
Prosenchyma: These are elongated fiber-like cells that are thick-walled and provide the plant with rigidity and strength.
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).
Epidermis Parenchyma: It is found in the epidermis of some gymnosperm leaves and tends to carry cutinized cell walls.
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 the parenchyma perform different significant functions. The list of parenchyma functions is given below:
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 orgastic.
Storing water and serving as a source of water.
Transport: Nutrients and other chemicals are transported by Parenchyma cells.
Transfer cells have outgrowth to maximize surface absorption.
Photosynthesis:
Chlorenchyma occurs in mesophyll as well as the other green parts of the plant, has chloroplasts and performs photosynthesis.
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.
Differences Between Xylem and Phloem Parenchyma
The differences between Xylem and Phloem parenchyma are given below:
FAQs on Parenchyma Plant Tissue: Meaning, Structure, and Types
1. What is parenchyma tissue and why is it considered a fundamental tissue in plants?
Parenchyma is a type of simple permanent tissue composed of living, relatively unspecialised cells. It is considered a fundamental or ground tissue because it forms the bulk of the plant body, filling the cortex and pith of stems and roots, the mesophyll of leaves, and the flesh of fruits. Other more specialised tissues, like xylem and phloem, are often embedded within it.
2. What are the key structural features of parenchyma cells?
Parenchyma cells have distinct structural characteristics that relate to their diverse functions. Key features include:
- Shape: They are typically isodiametric, meaning they have roughly equal dimensions, but can also be oval, round, or elongated.
- Cell Wall: They possess a thin primary cell wall made of cellulose and hemicellulose.
- Living Protoplast: Unlike sclerenchyma, these cells are living at maturity and contain a prominent nucleus and cytoplasm.
- Intercellular Spaces: The cells can be loosely packed, creating large intercellular spaces that facilitate gas exchange and storage.
- Vacuoles: Young cells have small vacuoles, which merge into one large central vacuole in mature cells for storing water, nutrients, and waste products.
3. What are the main functions of parenchyma tissue in a plant?
Parenchyma tissue is metabolically active and performs several vital functions for the plant, including:
- Storage: It serves as a primary site for storing food in the form of starch, proteins, fats, and oils. It also stores water, especially in succulent plants.
- Photosynthesis: A specialised type called chlorenchyma contains chloroplasts and is the main site of photosynthesis in leaves and young stems.
- Secretion: It can secrete substances like nectar, resins, and oils.
- Gas Exchange: The intercellular spaces allow for the circulation of gases required for respiration and photosynthesis.
- Healing and Regeneration: Due to their ability to divide, parenchyma cells play a crucial role in healing wounds and regenerating plant parts.
4. How do specialized parenchyma tissues like aerenchyma and chlorenchyma help plants adapt to their environments?
Parenchyma tissue can modify its structure to help plants survive in specific environments. For instance, aerenchyma is a type of parenchyma with large air cavities, which provides buoyancy to aquatic plants, allowing them to float. It also facilitates the diffusion of oxygen from the leaves to the submerged roots. Chlorenchyma is parenchyma rich in chloroplasts, specialised for performing photosynthesis, which is critical for all autotrophic plants to produce their own food.
5. What does it mean for parenchyma cells to be 'totipotent' and how does this property benefit the plant?
Totipotency is the ability of a single plant cell to divide and differentiate to form an entire new plant. Parenchyma cells retain this ability even after they mature. This is highly beneficial for the plant as it enables wound healing and the regeneration of damaged or lost parts. It is also the principle behind plant tissue culture, where a small piece of plant tissue can be used to grow a whole plant in a lab.
6. How does parenchyma tissue differ from other simple permanent tissues like collenchyma and sclerenchyma?
Parenchyma, collenchyma, and sclerenchyma are all simple permanent tissues but differ significantly in structure and function:
- Parenchyma: Consists of living cells with thin cellulose walls. Its primary roles are storage, photosynthesis, and secretion.
- Collenchyma: Consists of living cells with cell walls that are unevenly thickened, especially at the corners. It provides flexible mechanical support to growing parts of the plant like young stems and petioles.
- Sclerenchyma: Consists of dead cells with very thick, lignified walls. Its sole purpose is to provide rigid mechanical strength and support to the plant, often found in seed coats and fibres.
7. What is the difference between xylem parenchyma and phloem parenchyma?
Both are types of parenchyma associated with complex vascular tissues. Xylem parenchyma is the only living component of xylem tissue. Its main functions are to store food reserves like starch and fats and to assist in the radial conduction of water. Phloem parenchyma is found in the phloem tissue and is involved in storing food materials and assisting in the transport of prepared food through the phloem sieve tubes. A key difference is that phloem parenchyma is absent in most monocots.
