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What are tissue?
There are many different cells in the bodies of plants and animals and they
are grouped according to their function
...
The cells of
conducting tissues are long thin tubes that carry liquids up and down the
plant
...
Xylem tissue transports water and minerals from the soil up to the
leaves and the rest of the plant
...
In many plants there is some meristematic
tissue called cambium between xylem and phloem
...
In phloem tissue the cells that carry nutrients from the leaves to the rest of
the plant are called sieve tubes
...
Another important cell in the phloem is called companion
cells
...
Phloem tissue is suited to its function
...
« The end walls with holes allow cytoplasm of one cell to be in
contact with the cytoplasm of the next cell which helps the
nutrients to move more quickly
...
« The companion cells takes over the control of its neighbouring
sieve tube
...
The cells walls
become very strong and are thickened with waterproof chemical
called lignin
...
Vessels and tracheids are
therefore not living cells;they are the skeletons of cells
...
The end walls break down and hollow dead cells become a
continuous tube
...
Xylem tissue is also used to support the plant because lignin is
strong
...
There is annular or ringed,spiral and reticulate,which is like a
net
...
Wood
is the xylem of large plants such as trees
...
« Vessels have no end walls so they form continuous tubes that
carry water quickly through the plant
...
« Xylem cells are dead and contain no cytoplasm so a
continuous flow of water can move up them
...
« Xylem cells are dead and contain no cytoplasm so a
continuous flow of water can move up them
Ground tissue
The ground tissues fill the gaps between the bundles of conducting tissue
and make up the greater part of many plants
...
Parenchyma
tissue fills the spaces between the other kinds of tissues
...
Each cell has a
large vacuole
...
« The thin cell walls allow dissolved nutrients and water to move
between the cells
...
« The air spaces allow gases such as carbon dioxide and oxygen to
move quickly through the plant
...
Chlorenchyma
Chlorenchyma is parenchyma that is specialised for
photosynthesis
...
Chlorenchyma tissue may also be
found near the edge of young stems and it makes them look green
Chlorenchyma tissue is suited to its function
...
v The column shape of some of the Chlorenchyma cells in
leaves allow many cells to be packed together so that many
chloroplast may be exposed to the sunlight
...
The cells are similar to parenchyma but fit together
more closely
...
Collenchyma cells do not contain
lignin,so are living and flexible
...
Collenchyma tissue is suited to its function
...
v The parts of the walls that are not thickened allow
dissolved nutrients and water to pass through the cells
...
Sclerenchyma
Sclerenchyma is also specialised for strengthening the
plant
...
The lignin makes the cells strong but
because it is waterproof,the contents of the cells
die
...
Sclerenchyma tissue is suited to its function
§ The evenly thickened cell walls support and protect the
soft tissues of the plant
...
§ Patches of sclerenchyma can act as supports for the
plant because the cells are packed tightly together and
there are no air spaces
...
The
epidermis protects the inner cells and helps to support the
plant organs
...
They make a waxy,waterproof layer called the
cuticle on the outside that makes them waterproof and helps
them to resist disease
...
v The strong tight fitting epidermal cells make a strong outer
layer that helps to support and protect the plant
...