3. INTRODUCTION
• The plastid is a membrane bound organelle found
in the cells of plants, algae, and some
other eukaryotic organisms.
• Plastids were discovered and named by Ernst
Haeckel, but A. F. W. Schimper was the first to
provide a clear definition.
• Plastids are the site of manufacture and storage of
important chemical compounds used by the cells
of autotrophic eukaryotes.
4. • They often contain pigments used
in photosynthesis, and the types of pigments in
a plastid determine the cell's color. They have
a common evolutionary origin and possess a
double-stranded DNA molecule that is circular,
like that of prokaryotic cells.
6. CHROMOPLASTS
• Chromoplasts are plastids, heterogeneous orga
nelles responsible for pigment synthesis and
storage in specific photosynthetic eukaryotes.
7. APPEARANCE
• Chromoplasts are plastids that are colored due
to the pigments that are produced and stored
inside them.
• They are found in fruits, flowers, roots, and
senescent leaves.
• The color of these plant organs is associated
with the presence of pigments, apart
from chlorophyll.
8. STRUCTURE
• Chromoplasts vary in structural appearance under
an electron microscope.
• They may generally be grouped into five types:
(1) globular, (2) crystalline, (3) fibrillar, (4)
tubular, and (5) membranous.
• Nevertheless, some chromoplasts may be harder
to classify when their structure is rather
complicated, such as those of tomatoes that
appear both membranous and crystalline in
appearance.
9. FUNCTIONS
• Chromoplasts are found in fruits, flowers, roots,
and stressed and aging leaves, and are responsible
for their distinctive colors.
• This is always associated with a massive increase
in the accumulation of carotenoid pigments.
• The conversion of chloroplasts to chromoplasts
in ripening is a classic example.
• They are generally found in mature tissues and
are derived from preexisting mature plastids.
10. • Chromoplasts synthesize and store pigments such as
orange carotene, yellow xanthophylls, and various other
red pigments.
• The main evolutionary purpose of chromoplasts is
probably to attract pollinators or eaters of colored fruits,
which help disperse seeds.
• However, they are also found in roots such
as carrots and sweet potatoes.
• They allow the accumulation of large quantities of water-
insoluble compounds in otherwise watery parts of plants.
12. PHAEOPLASTS
• These are yellow or brown plastids found in
brown algae, diatoms and dinoflagellates.
• Fucoxanthin is a carotenoid pigment which
masks the colour of chlorophyll a, which is
also present.
• It also absorbs light and transfer the energy to
chlorophyll a.
16. CHLOROPLASTS
• The chloroplast, found only in algal and plant cells, is a cell
organelle that produces energy through photosynthesis.
• The word chloroplast comes from the Greek words khloros,
meaning “green”, and plastes, meaning “formed”.
• It has a high concentration of chlorophyll, the molecule that
captures light energy, and this gives many plants and algae a
green color.
• Like the mitochondrion, the chloroplast is thought to have
evolved from once free-living bacteria.
18. STRUCTURE
• Chloroplasts, like mitochondria, are oval-shaped and have two
membranes: an outer membrane, which forms the external
surface of the chloroplast, and an inner membrane that lies just
beneath.
• Between the outer and inner membrane is a thin
intermembrane space about 10-20 nanometers wide.
• The space within the inner membrane is called the stroma.
• While the inner membranes of mitochondria have many folds
called cristae to absorb surface area, the inner membranes of
chloroplasts are smooth.
• Instead, chloroplasts have many small disc-shaped sacs called
thylakoids within their stroma.
19. • In the stroma, enzymes make complex organic
molecules that are used to store energy, such as
carbohydrates.
• The stroma also contains its own DNA and
ribosomes that are similar to those found in
photosynthetic bacteria.
• For this reason, chloroplasts are thought to have
evolved in eukaryotic cells from free-living
bacteria, just as mitochondria did.
21. FUNCTION
• Chloroplasts are the part of plant and algal cells that carry out
photosynthesis, the process of converting light energy to
energy stored in the form of sugar and other organic molecules
that the plant or alga uses as food.
• Photosynthesis has two stages.
• In the first stage, the light-dependent reactions occur.
• These reactions capture sunlight through chlorophyll and
carotenoids to form adenosine triphosphate (ATP, the energy
currency of the cell) and nicotinamide adenine dinucleotide
phosphate (NADPH), which carries electrons.
22. • The second stage consists of the light-independent
reactions, also known as the Calvin cycle. In the
Calvin cycle, the electrons carried by NADPH
convert inorganic carbon dioxide and to an organic
molecule in the form of a carbohydrate, a process
known as CO2 fixation.
• Carbohydrates and other organic molecules can be
stored and used at a later time for energy.
24. LEUCOPLASTS
• Leucoplasts are a category of plastid and as such
are organelles found in plant cells.
• They are non-pigmented, in contrast to other plastids such
as the chloroplast.
• Lacking photosynthetic pigments, leucoplasts are not green
and are located in non-photosynthetic tissues of plants, such
as roots, bulbs and seeds.
• They may be specialized for bulk storage
of starch, lipid or protein and are then known
as amyloplasts, elaioplasts, or proteinoplasts (also called
aleuroplasts) respectively.
26. AMYLOPLASTS
• Amyloplasts are a type of plastid, double-enveloped
organelles in plant cells that are involved in various
biological pathways.
• Amyloplasts are specifically a type leucoplast, a
subcategory for colorless, non-pigment-containing plastids.
• Amyloplasts are found in roots and storage tissues and
store and synthesize starch for the plant through
the polymerization of glucose.
• Starch synthesis relies on the transportation of carbon from
the cytosol, the mechanism by which is currently under
debate.
28. ELAIOPLASTS
• Elaioplasts are a type of leucoplast that is specialized
for the storage of lipids in plants.
• Elaioplasts house oil body deposits as rounded
plastoglobuli, which are essentially fat droplets.
30. PROTEINOPLASTS
• Proteinoplasts are specialized organelles found only in plant cells.
• Proteinoplasts belong to a broad category of organelles known as plastids.
• Because they lack pigment, proteinoplasts are more specifically a kind
of leucoplast.
• They contain crystalline bodies of protein and can be the sites of enzyme
activity involving those proteins.
• Proteinoplasts are found in many seeds, such as brazil
nuts, peanuts and pulses.
• Although all plastids contain high concentrations of protein, proteinoplasts
were identified in the 1960s and 1970s as having large protein inclusions
that are visible with both light microscopes and electron microscopes.