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Plant tissues are collections of similar cells that
serve a specific purpose by functioning
together. Unlike that of tissues present in
animals, the major organs of plants (roots,
stems and leaves) are all composed of the same
three tissues (epidermis, vascular and ground
tissues)
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Meristematic Tissues – embryonic tissue that will
give rise to more specialized kinds when mature
Dermal Tissues – outer layer that covers the plant
body. It permits the exchange of matter between
the plant and the environment.
Vascular Tissues – complex tissue system
responsible for water and nutrient transport
Ground Tissues – constitutes majority of the plant
body, contains three types of cells: parenchyma,
collenchyma and sclerenchyma. It functions for
metabolism, storage and support activities.
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Cells in a meristematic tissue (also called meristem) are active in
growing and dividing and can be considered as embryonic tissues
Two types
Apical meristem – spical meristeems occur at the tips of roots and
shoots. These are the root apical meristem (RAM) and shoot
apical meristem (SAM). They are responsible for the length-wise
extension of the plant body, which is known as primary growth.
Apical meristems give rise to primary tissues
Lateral meristem – lateral meristems are responsible for the
outward expansion of plants, known as secondary growth. They
produce the secondary tissues which constitute the secondary
plant body. Lateral meristems are called cambia (singular,
cambium). Many plants lack lateral meristems. These is only
produced by the vascular cambium). These plants are said to be
herbaceous.
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Three types:
Parenchyma – the progenitor of all other cells
and the most common component of ground
tissues. They perform virtually all the
metabolic activities of plant cells
Examples: chlorenchyma cells – contains
chrloroplasts and are specialized for
photosynthesis; aerenchyma cells contain large
intracellular air spaces and function in gas
exchange
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Collenchyma cells are living at maturity. They
usually occur as discrete strands or as
continuous cylinders beneath the epidermis in
stems and petioles. They also border veins in
dicots. They are relatively long, with
nonlignified primary walls which allow them
to stretch.
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Sclerenchyma cells are non living and lack
protoplasts at maturity. They may be found in all
parts of both the primary and secondary plant
body. They have thick, lignified secondary walls.
They provide strength and support in parts that
have cease elongating. There are two types: fibers
– long slender cells which occur in strands or
bundles; and sclereids – vary in shape, often
branched, and may occur singly or in groups in
ground tissues throughout the plant. They make
up the seed coat of seeds, shells of nuts, and give
the pears its gritty texture. Their function is
primarily for protection.
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A complex tissue system produced from
procambium in primary growth and from
vascular cambium in secondary growth. It
functions for the conduction of water and some
minerals throughout the plant, support for the
plant, and for some food storage. There are
two types: xylem (a complex tissue and one of
the major components of the vascular tissue)
and phloem (the principal food conducting
tissue in vascular plants and consists of
elongated cells
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The epidermis is the outermost layer of the primary
plant body. In organs that undergo secondary growth,
the epidermis is eventually replaced by the periderm.
In leaves and stems the epidermis contain several types
of special cells:
Guard cells – sausage-shaped cells that occur in pairs
on leaf surfaces
Trichomes – hair-like projections (major function is
secretion and absorption
Periderm – replaces the epidermis in stems and roots
that undergo secondary growth. It forms the “bark”
with the phloem. Function is for protection.