Plant tissues include collenchyma, Sclerenchyma, parenchyma cells, their features, difference between collenchyma, sclerenchyma and parenchyma cells

1. PlantsTissues
• collenchyma
• Sclerenchyma
• parenchyma cells
• Their features
• Difference between collenchyma, sclerenchyma and parenchyma
cells
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2. collenchyma,sclerenchyma and parenchyma
cells
Cells derived from meristem that have acquired a special
function like photosynthesis, secretion, storage are treated
as part of matured tissue. There are different types of
mature tissues. Example: parenchyma, collenchyma,
sclerenchyma, xylem and phloem.
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4. Collenchyma cells
 Where is it found? Collenchyma tissues are mainly found under the epidermis in
young stems in the large veins of leaves.
 What do they do? Collenchyma is primarily a mechanical tissue adapted for
support of growing organs. they are stretchy and can change size as a young leaf grows,
collenchyma cells can elongate and still give the leaf structure.
Unique Structural Features
 The thickenings are deposited unevenly; thickenings are present at the
corners of the cells, and contain cellulose and pectin, collenchyma cells
show thin and thick wall portions depending on the direction of the cut.
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5.  A few chloroplasts may be present in the cells.
 If they contain chlorophyll they are known as
colerenchyma.
 Collenchyma cells are considerably elongated
and circular, oval or polygonial in cross section.
 Vacuoles are small.
 Nucleus is present hence the tissue is living.
 Intercellular spaces are absent.
 Their cell walls don't contain lignin.
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6. Features linked to Function
 The cells are composed of living, elongated cells running parallel to the
length of organs that it is found in.
 The cells have thick cellulose cell walls which thickened at the corners.
This makes the plants more structure of the plant flexible whilst still
holding desired structure.
 Intercellular air spaces are absent or very small to make them more
closely packed increasing strength.
 The cells contain living protoplasm and they sometimes contain
chloroplasts so that photosynthesis can take place.
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8. Sclerenchyma cells
 Where is it found? They often occur in bundles or strands and can be
found almost anywhere in the plant body, including the stem, the roots,
and the vascular bundles in leaves.
 What do they do?These are greatly elongated cells whose long, tapering
ends interlock, thus providing maximum support to a plant.
Unique Structural Features
 Mature sclerenchyma cells are usually dead cells that have heavily
thickened secondary walls containing lignin.
 The cells are rigid and nonstretchable and are usually found in
nongrowing regions of plant bodies, such as the bark or mature stems.
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9. Types
Sclerenchyma tissue is further divided into: sclerids and fibers.
 Fibers
 Fibres are greatly elongated cells whose long, tapering ends interlock,
thus providing maximum support to a plant. They often occur in
bundles or strands and can be found almost anywhere in the plant
body, including the stem, the roots, and the vascular bundles in leaves.
 Sclerids
 Sclerids are extremely variable in shape and are present in various
tissues of the plant, such as the periderm, cortex, pith, xylem,
and phloem. They also occur in leaves and fruits and constitute the
hard shell of nuts and the outer hard coat of many seeds. Sometimes
known as stone cells, sclereids are also responsible for the gritty
texture of pears and guavas.
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11. Parenchyma Cells
 Where is it found? It is usually present
in cortex, pericycle, pith, and medullary rays in
primary stem and root.
 What do they do? It generally constitutes the
"filler" tissue in soft parts of plants.
Unique Structural Features
 Parenchyma cells are living cells and may
remain meristematic at maturity—meaning
that they are capable of cell division if
stimulated.
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12.  They have thin and flexible cellulose cell walls, and are
generally polyhedral when close-packed, but can be roughly spherical
when isolated from their neighbours.
 They have large central vacuoles, which allow the cells to store and
regulate ions, waste products, and water.
 Tissue specialised for food storage is commonly formed of parenchyma
cells.
Features linked to Function
 The shape of parenchyma cells varies with their function.
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13.  Shapes of parenchyma:
• Polyhedral
• Stellate (found in stem of plants and have well developed air spaces
between them)
• Elongated (found in tissue of leaf)
• Lobed (found in spongy and mesophyll tissue of some plants)
 Their main function is to repair.
 In leaves, they form the mesophyll and are responsible
for photosynthesis and the exchange of gases. Parenchyma cells in
the mesophyll of leaves are specialised parenchyma cells called
chlorenchyma cells (parenchyma cells with chloroplasts).
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14.  Storage of starch, protein, fats, oils and water in roots, tubers
(e.g. potatoes), seed endosperm (e.g. cereals)
and cotyledons (e.g. pulses and peanuts)
 Secretion (e.g. the parenchyma cells lining the inside of resin ducts)
 Wound repair and the potential for renewed meristematic activity
 Other specialised functions such as aeration (aerenchyma) provides
buoyancy and helps aquatic plants in floating.
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16. Parenchyma Collenchyma Sclerenchyma
Location Stem,root ,leaves ,flowers
,fruits widely distributed
Below the epidermis Outermost boundries
of plant parts cortex
,pith ,hard seeds etc
Function Stores and assimilate food Provide mechanical
support and elasticity
Provide mechanical
support
Provide mechanical
(turgidity)
Manufacture sugar
and starch
Stores waste products like
tannin ,resin,gum etc
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