Parenchyma Cells in Plants: Structure, Classification and Functions (PPT)


functions of parenchyma

Parenchyma
(Structure, Classification and Function of Parenchyma)

What is simple tissue?

Ø  The tissue (a group of cells with particular function) composed of single type of cells.

Ø  Three types of simple tissue system in plants:

(1).  Parenchyma

(2).  Collenchyma

(3).  Sclerenchyma

What are the characteristics of Parenchyma (Parenchymatous Cells)?

Ø  Parenchyma is a simple permanent tissue.

Ø  They are living cells which contains plenty of water.

Ø  Cells are nucleated with prominent nucleus.

Ø  They are thin walled cells.

Ø  Cell wall composed of cellulosic primary cell wall only.

Ø  No lignin deposition in the cell wall of parenchyma.

Ø  Parenchymatous cells are relatively undifferentiated

Ø  Parenchyma is the least specialized along simple permanent tissues in plants.

Ø  Parenchyma usually occupies in the ground tissue of stem, root, leaves, petiole and fruits.

Ø  They are also found in xylem and phloem as xylem parenchyma and phloem parenchyma respectively.

Ø  The parenchyma of ground tissue is originated from the ground meristem.

Learn more: Classification of Meristems

Ø  Parenchyma of the xylem and phloem are originated from the cambium.

parenchyma ppt

What are the Different Types of Parenchyma?

Ø  Different types of parenchymatous cells occur in plants.

Ø  Classification of parenchyma in plants is based on two criterions: (1) Function and (2) Shape.

Ø  Based on functions the parenchyma is classified into Seven categories, they are:

(1).    Chlorenchyma

(2).    Aerenchyma

(3).    Prosenchyma

(4).    Vascular Parenchyma

(5).    Medullary Parenchyma

(6).    Conjunctive Parenchyma

(7).    Armed Parenchyma

what is chlorenchyma (1). Chlorenchyma:

Ø  They are the parenchymatous cells with chloroplasts.

Ø  Chlorenchyma usually present in the mesophyll tissue of leaves.

Ø  They are also present in the outer cortex young stem.

Ø  The green colour of young stem and aerial roots are due to the presence of chlorenchyma.

Ø  Chlorenchymatous cells are usually loosely packed with many intercellular spaces.

Ø  Function of chlorenchyma: photosynthesis

tissues in leaf

(2). Aerenchyma:

Ø  They are parenchyma cells with plenty of intercellular spaces.

Ø  The huge intercellular spaces appear as large air cavities.

Ø  Air cavities of aerenchyma can store air.

Ø  Aerenchyma is a characteristic of aquatic plants.

Ø  In aquatic plants, aerenchyma assists in floating.

Ø  They provide buoyancy to the plants to balance in the water.

Ø  Respiratory gases (CO2 or O2) stored in aerenchyma can be utilized by the plants when required.

nymphaea aerenchyma

development of aerenchyma

(3). Prosenchyma:

Ø  They are elongated and narrow sized parenchyma.

Ø  They possess interpenetrating tapering (pointed) ends.

Ø  Prosenchyma is usually present in the vascular tissues of higher plants.

(4). Vascular parenchyma

Ø  They are the parenchyma cells occur in the vascular tissue of plants.

Ø  They provide nourishment to the vascular tissues.

Ø  They can also store ergastic substances like resins, tannins etc.

Ø  Axial parenchyma and ray parenchyma of wood are best examples.

Ø  Parenchymatous cells in heart wood (old secondary xylem) forms tyloses which can block the vessels cavities and can prevent the water flow through them.

Lear more: Tyloses formation and its Functions in Wood

what is passage cell(5). Medullary parenchyma:

Ø  Medullary parenchyma occurs in the medullary ray of primary vascular tissue of stem.

Ø  They are radially elongated cells with very thin walled cells.

Ø  They allow radial condition of water and minerals.

Ø  They can also store starch grains.

(6). Conjunctive parenchyma:

Ø  They form the conjunctive tissue of the stele of roots.

Ø  In most of the monocots, the conjunctive tissue becomes sclerenchymatous during maturation.

(7). Armed parenchyma:

Ø  They are star shaped parenchymatous cells with many spiny projections to the interior of the cells.

Ø  Armed parenchyma is found in the mesophyll of some gymnosperm.

Ø  Example: mesophyll cells of Pinus leaf (needle).

Based on shape in cross section (C.S. or T.S.), parenchyma is classified into two categories, they are:

(1).   Angular Parenchyma

(2).   Circular Parenchyma

what is angular parenchyma(1). Angular parenchyma

Ø  In angular parenchyma, the cells are angular and polygonal in outline.

Ø  This parenchyma is usually compactly packed without any intercellular spaces.

(2). Circular parenchyma

Ø  In circular parenchyma, the cells are circular (round) in outline.

Ø  They are usually loosely packed with plenty of intercellular spaces.

What are the Functions of Parenchyma?

@.  Parenchyma forms the fundamental ground tissue system in plants.

@.  Parenchymatous cells can store water.

how circular parenchyma is formed@.  They can store food materials as starch grains, protein grains or oil droplets.

@.  Chlorenchyma of leaves and young stem assist in photosynthesis.

@.  Aerenchyma in aquatic plants provides buoyancy.

@.  Parenchyma can store ergastic substances.

@.  Parenchyma in secondary wood form tyloses.

@.  All meristematic cells are parenchymatous cells

@.  Parenchyma can be easily differentiated into secondary meristem (Eg. cork cambium).


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