what is parencyma and its functions
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Answer:
Parenchyma is a type of simple permanent tissue that makes a major part of ground tissues in plants, where other tissues like vascular tissues are embedded. They are non-vascular and composed of simple, living and undifferentiated cells, which are modified to perform various functions. The other simple permanent tissues are:
Collenchyma
Sclerenchyma
Basic types of plant tissues
The main characteristics of parenchyma are:
They are living permanent tissues that have the ability to divide at maturity and help in the regeneration and healing of wounds
Parenchyma cells are the foundation of a plant as reproductive cells (spores, gametes) are parenchymatous in nature
Single parenchyma cell of a zygote has an ability to develop into an entire plant. These cells are called “totipotent” cells
Parenchyma cells occur in the form of continuous masses as homogeneous parenchyma tissues e.g. in pith and cortex of stems and roots, mesophyll of leaves, the flesh of succulent fruits and in the endosperm of seeds
Parenchyma cells may be associated with other types of cells to form heterogeneous complex tissues such as parenchyma of xylem and phloem
Parenchyma cells are essential for activities like photosynthesis, storage, secretion, assimilation, respiration, excretion and radial transport of water and solute
Structure of Parenchyma Cells
It is a living cell
It has a prominent nucleus and protoplast
The cells of parenchyma are isodiametric or polyhedral in shape. They may be polygonal, oval, round or elongated
These cells are closely packed or may have small intercellular space
They are made up of thin cell wall made up of cellulose, hemicellulose
Plasmodesmata join the cells of the parenchyma tissue
They have several small vacuoles. In the older parenchyma, smaller vacuoles merge to become a large central vacuole, which may accumulate anthocyanin or tannins
Water is abundant in the vacuoles of the parenchyma cells that act as a water reservoir
Storage parenchyma cells may have thick xyloglucan walls e.g. in the endosperm of the date palm. The sugar is used during germination and walls become thin
The parenchyma cells of flowers and fruits contain chromoplasts
Parenchyma cells may have a thick lignified wall that makes it difficult to differentiate it from sclerenchyma
Hydraulic property of cells gives the parenchyma its mechanical strength
Chloroplasts are present in the parenchyma cells that are specified to perform photosynthesis
The parenchyma cells which perform a secretory function, have dense protoplasm that is rich in ribosomes, Golgi bodies and a highly developed endoplasmic reticulum
Types of Parenchyma Cells
Parenchyma cells can be categorised based on their structure, location and functions performed. The main parenchyma tissues are:
Functions of Parenchyma cells
Parenchyma cells form the ground tissue of plants. Parenchyma tissues perform various important functions:
Storage: Parenchyma cells have large intercellular space which is ideal for storage
High amount of starch is present in the tubers of potato and cassava
These can store water, fats, oil droplets, and ergastic substances
Store water and act as a water reservoir
Transport: Parenchyma cells transport nutrients and other chemicals
Transfer cells have outgrowth for increasing absorption surface
The xylem parenchyma helps in radial transportation of water and minerals
Some cells transport light from the surface to underground cells
Photosynthesis: Chlorenchyma present in the mesophyll and the other green parts of the plant, have chloroplasts and perform photosynthesis
Gas Exchange: Aerenchyma cells help in the gas exchange
Protection: In gymnosperms, the parenchymatous cell have spiny projections that help in the protection from predators
Totipotent: Parenchyma cells have an ability to transform to the other types of cells and act as a precursor for other types of cells
Buoyancy: Aerenchyma present in aquatic plants have air sacs that help in floating
Cuticle present on epidermis helps in reducing transpiration in water stress condition
Thick-walled parenchyma cells provide mechanical strength to the plant
Healing and regeneration: Parenchyma cells which retain their ability to divide even on maturity help in regeneration and wound healing. Tyloses present in the xylem parenchyma help in preventing damage to vascular tissues in the condition of drought.
Parenchyma cells are living cells that have diverse functions ranging from storage and support to photosynthesis and phloem loading (transfer cells) Parenchyma cells which contain many chloroplasts and are concerned primarily with photosynthesis are called chlorenchyma cells.
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