Parenchyma is a cell and tissue type found in plants that is unspecialized and has thin primary cell walls. Parenchyma cells originate from meristematic tissues and can be permanent or meristematic. They are found in various tissues throughout the plant including the pith, cortex, xylem, phloem, leaves and seeds. Parenchyma cells function in storage, photosynthesis, and aeration and can take on different forms depending on their location and specialization in the plant. Parenchyma is considered the ancestral cell type from which other cell types evolved.
Genome organization in virus,bacteria and eukaryotes.pptx
Anatomy
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3. ANATOMY OF VASCULAR PLANTS
Presentation
Origin, Structure, Development and
Function specialization of Parenchyma
4.
5. Parenchyma is a cell and tissue type in which the cells have
only thin primary walls; the cells are unspecialized, lack the
characteristic wall of collenchyma and the secondary walls of
sclerenchyma; the cells have live nucleate protoplast
concerned with various physiological activities in plants; the
cells are meristematic, or permanent, simple homogeneous
(i.e. composed of one type of cells only), fundamental or
ground tissue upon which other simple and conducting tissues
appear to be embedded.
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7. Parenchyma cells present in the primary plant body, i.e. pith and cortex,
originates from the ground meristem. Procambium and cambium give rise
to xylem and phloem parenchyma of the primary and secondary conducting
tissues respectively. Phelloderm originates from phellogen. In leaves,
protoderm and ground meristem give rise to parenchymatous epidermis
and mesophyll respectively.
8. Mature parenchyma tissues may be compactly set
without any intercellular spaces. Ex endosperm tissue
of seeds. They may also be arranged loosely so that
well spaces are present between them. Ex stems and
leaves of hydrophytes developed intercellular.
Arrangement
9.
10. Parenchyma cells usually have primary walls (e.g., storage and
chlorophyllous parenchyma). The storage parenchyma cells of endosperm
of Phoenix, Asparagus have very thick walls. The thickness of wall is due
to the deposition of hemicellulos.
Usually parenchyma cells contain living protoplast with single or
numerous vacuoles. They may also contain leucoplasts, chloroplasts etc.
(chloroplast containing parenchyma cells are termed as chlorenchyma).
Various carbohydrates, nitrogenous and fatty substances are found in the
cell sap of parenchyma. The parenchyma cells of the roots of sugar beet
and the bulb scales of onion contain amides, proteins, sugars etc. in their
cell sap.
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12. From the evolutionary point of view, the parenchymatic cell is
regarded as the ancestor or precursor of the other cell types of
the plant because it is not much differentiated and shows
similar behavior as meristematic cells. For example, it can
dedifferentiate by decreasing the thickness of the cell wall, and
becomes a totipotent cell that can proliferate. Thus,
parenchyma is an excellent source to produce callus (in
vitro mass of undifferentiated cells that proliferate and
differentiate to give an adult plant).
13. This type of parenchyma, also known as chlorenchyma,
is specialized in photosynthesis thanks to the
many chloroplasts present in the cells. Photosynthetic
parenchyma is commonly found under the epidermis,
where light is more intense, and it is abundant in
leaves, but also in the cortex of green shoots. The
photosynthetic parenchyma of the leaves is known
as mesophyll, which is usually divided in two types:
palisade and spongy mesophyll. Palisade mesophyll is
close to the upper epidermis of the leaves, where it gets
more light.
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15. The cells in this tissue synthesize and stores a number of
substances. Although these substances can be solid, like starch
grains and crystallized proteins, they are mostly found in
solution, such as lipids, proteins, and others. Usually they are
stored in vacuoles, which are the compartment specialized in
storing molecules. In the cytoplasm, some moleculars are also
stored like carbohydrates and nitrogenated substances. Some
parenchymatic cells store only one type of substance, but a
mix of different substances can also be found in the same cell.
16.
17. Although all parenchymatic cells store some amount of water,
those of the aquiferous parenchyma are specialized in this
function. They are large cells, with a thin cell wall and a very
large vacuole where water is stored. In the cytoplasm or in the
vacuole, there is a mucilaginous substance that increase the
capacity of absorption and retention of water.
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19. There are large interconnected empty intercellular spaces,
where gases can diffuse and aerate the root.
Aeriferous parenchyma or aerenchyma contains large
intercelular empty spaces, larger than in other plant tissues.
This tissue is well-developed in plants living in wet or aquatic
environments (these plants are known as hydrophytes),
although it can be also found in non aquatic plants under
stress. Both, stem and root can developed aerenchyma
