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Cell types
Parenchyma
Parenchyma are diverse
cells and can have many
different shapes and be
very specialized in their
function.
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Cell types
Parenchyma
Parenchyma cells are usually
isodiametric or polyhedral in
shape.
They have only a primary cell wall
and retain the ability for future
cell division.
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Cell types
Parenchyma
Parenchyma cells contain a
nucleus and when they are
first formed, they are
densely cytoplasmic and have
several small vacuoles.
Cytoplasm
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Nucleus
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Cell types
Parenchyma
However, in older parenchyma
cells the vacuoles merge into one
large central vacuole with the
cytoplasm and organelles - like
these chloroplasts on the edges
of the cell.
Vacuole
Cytoplasm and
chloroplasts
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Cell types
Parenchyma
Parenchyma are diverse cells
and can have many different
shapes and be very specialized
in their function.
Based
on
their
function
specialized parenchyma cells can
grouped as:
Ground tissue
Storage tissue
Chlorenchyma
Aerenchyma
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Cell types
Parenchyma
Vascular
bundle
The cortex and pith in stems
and roots are parenchyma cells
commonly referred to as the
ground tissue.
The ground tissue surrounds
the vascular system in the
stem.
Pith
Cortex
Stem cross-section
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Cell types
Parenchyma
There are several distinct storage
tissues in plants. Three examples are:
Seed endosperm
Storage parenchyma
Ray parenchyma
Storage parenchyma in cotyledon.
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Cell types
Parenchyma
The endosperm is designed to store food for the developing embryo
and seedling.
Endosperm
Embryo
axis
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Corn seed
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Cell types
Parenchyma
The endosperm is filled with lipid bodies, protein bodies and especially
amyloplasts containing starch.
Protein bodies in legume endosperm.
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Amyloplasts in grain endosperm.
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Cell types
Parenchyma
One of the major functions of
parenchyma tissue is to store
food reserves.
In some cases, large amounts
of parenchyma are used for
storage as in this beet root.
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Cell types
Parenchyma
Dilated ray
A second major parenchyma type
used for storage is ray parenchyma.
Ray parenchyma cells grow horizontal
to the developing stem, sometimes
deep within the non-living xylem cells.
Ray
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Cell types
Parenchyma
Ray cells are an important storage
tissue to store carbohydrates and
proteins over the winter in stems.
These stored materials are used to
support new spring shoot and leaf
growth.
Ray
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Cell types
Parenchyma
Parenchyma cells in the
leaf actively involved
with photosynthesis are
termed chlorenchyma.
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Cell types
Parenchyma
Chlorenchyma can be divided into
the leaf palisade layer and the
spongy mesophyll cells.
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Cell types
Parenchyma
The palisade layer is usually one
to three cell layers deep and
develops under the epidermis on
the top (adaxial) side of the leaf.
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Cell types
Parenchyma
The spongy mesophyll cells occur
below the palisade layer and are
loosely packed together.
This creates air chambers that
allows carbon dioxide to move
from the stomata on the
underside of the leaf to these
chloroplast containing cells.
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Cell types
Parenchyma
The leaf Palisade and Mesophyll cells contain abundant chloroplasts easily
seen from the red color of chlorophyll in the leaf cross-section below.
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Cell types
Parenchyma
This electron micrograph
shows a single mesophyll
cell with an active nucleus
and numerous chloroplasts.
Nucleus
Chloroplast
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Cell types
Parenchyma
Aerenchyma can occur in
leaves, stems or roots and
act as air passages.
They occur commonly in
water logged roots and in
aquatic plants.
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Cell types
Parenchyma
Aerenchyma is easily seen
in the leaf of the floating
water lily.
Air in arenchyma spaces
help the leaf to float.
Leaf cross-section in Nymphaea (Water lily)
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Cell types
Parenchyma
Aerenchyma can form from
elongating cells creating large
intercellular spaces or by cells
disintegrating to leave a large
air space.
Stem cross-section in Myriophyllum
(Parrot feather)
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Cell types
Parenchyma
Diaphragm
Small cells form an intricate
lattice
structure
creating
aerenchyma in water hyacinth.
These air passages form pipes
for air transport. However at
intervals, cellular diaphragms
form that allow air but not water
to move through the passages.
This prevents sinking of this
floating aquatic plant in case of
damage that would allow water
into the air passage.
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Lattice cells
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Cell types
Parenchyma
Lotus (Nelumbo) produces an edible
root with large arenchyma spaces.
They help move air down into the
submerged roots.
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