Plant- and Marine-derived n-3 Polyunsaturated Fatty Acids ...
PLANT GROUPS - uobabylon.edu.iq
Transcript of PLANT GROUPS - uobabylon.edu.iq
PLANT GROUPS CHLOROPHYTA
1
PLANT GROUPS
(3)
General characteristic of the Chlorophyta
1 Habitat Aquatic (mainly fresh water), terrestrial in
moist situations, a few Epiphytic
2 Pigments Chlorophyll a & b, β-carotene, α-carotene less
prominent
3 Food Reserves Starch, rarely inulin, Oils & Fats
4 Cell Wall Component Cellulose, Crystalline glycoproteins
5 Reproduction Asexual & Sexual (Isogamy, An isogamy &
Oogamy
6 Growth Forms Flagellate coccoid, Filamentous rarely
Foliaceous or siphonaceous
7 Flagella Two or Four Occasionally numerous
Flagella are present in all classes of algae except Cyanophyceae &
Rhodophyceae. There number, nature and mode of Orientation are important.
There are two types of flagella.
1) Acronematic or Whiplash types which are smooth & do not have hairs
(Mastigonemes) on its surface.
2) Pantonematic or tinsel type which have hairs on its surface.
PLANT GROUPS CHLOROPHYTA
2
Flagella hairs are of two types
a) Fibrous solid hairs
b) Tubular hairs
Flagella in Algae & other plant except bacteria are composed of nine peripheral
doubled microtubules & two central single microtubules. This is commonly known
as (9 + 2 Pattern) of fibrils of flagellum these are produced in a matrix
surrounded by Flagellar membrane & Flagellar sheath.
Single central tubules
Peripheral doublet tubules
Radial spokes
Slide arm
Cross Section Showing (9 + 2) Pattern
ppppPPattern Pattern Pattern) Pattern
Membrane
PLANT GROUPS CHLOROPHYTA
3
Cell Structure of Chlorophyta
Cellular organization in Chlorophyta as in all other Algae except Cyanophyta is
Eukaryotic the cells possess cell organelles
Cell Wall: The mature cell of green Algae possesses a definite cell wall.
Usually outer layer is pectic & inner cellulosic.
Chloroplast: Present in many type Reticulate, Peripheral, Stellate, Small
discoid & Spiral.
Pyrenoid: In most green Algae the plastids contain one or more specially
differentiated regions called Pyrenoids these are the major sites of starch
formantion in green Algae.
Eye Spot (Stigma): Most of the flagellated cells that show phototatic
movement have an Eye spot. In green Algae the Eye spot is always in the
Chloroplast near the flagellar bases in anterior portion.
Mitochondria, Golgi bodies, Endoplasmic reticulum, Ribosomes &
Contractile vacuole are present in the cell.
Reproduction
1) Vegetative Reproduction: Portion of the plant body get separated to form
new individuals without any obvious change in the protoplast, cell division
occur.
2) Asexual Reproduction
a) Zoospores are motile & naked spore produced within the
Zoosporangium. These frequently move with the help of flagella
which maybe two or more. In Chlamydomonas the Zoospore
Exactly similar to parent cell & are formed in variable numbers
PLANT GROUPS CHLOROPHYTA
4
(4, 8, and 16). In Filamentous forms, in Ulothrix a cell produces up
to (8 or 16) biflagellate or quadri flagellate. In Oedogonium a single
multi flagellate Zoospore is formed from each cell.
b) Aplanospores are nonmotile & are produced in Aplanosporangia.
They are common occurrence in Chlorella.
c) Hypnospore these are thick walled non motile. Spores that undergo a
long resting period in Sphaerella.
d) Akinetes are the direct modification of vegetative cell which becomes
converted into a thick wall non motile resting spores is formed in
Chladophora.
e) Autospores they are non-motile spores resembling the parent cell in
shape & structure in Scendesmus.
f) Cysts these are resting cells enclosed in a thick envelope is known in
Vaucheria.
g) Palmella stage occasionally during unfavorable condition.
Sexual Reproduction
1) Isogamy
2) An isogamy
3) Oogamy
PLANT GROUPS CHLOROPHYTA
5
Life Cycle
There are different types of life cycle in Chlorophyta classified into four categories
Haplontic life cycle: The main plant body is haploid & the Zygote
being the only diploid stage, in unicellular & filamentous forms.
Diplontic life cycle: The main plant body is diploid which forms
haploid gametes meiotically. Gametes fusion & form diploid Zygote which
directly germinates into a new plant in Cladophora.
Main Plant (1n)
Zygote (2n)
Fusion
Gamete (1n)
Gamete (1n)
Meiosis
Spore (1n)
Haplontic Life Cycle
e
PLANT GROUPS CHLOROPHYTA
6
Isomorphic alternation of generation: Both haploid & diploid
phases are similar in external appearance, a haploid plant produces gametes & a
diploid plant produces Zoospores. The Zygote develops into a new diploid plant
without undergoing reduction division in Ulva.
Main Plant (2n)
Zygote (2n)
Gametangia
Meiosis
Gamete (+) Gamete (-)
Fusion
Diplontic Life Cycle
PLANT GROUPS CHLOROPHYTA
7
Heteromorphic alternation of generation: The two phases of
life cycles are unequal in size different in external appearance; the Zygote does
not undergo a reduction division but develops into short diploid filament.
Plant (2n)
Plant (1n)
Meiosis
Spore (1n)
Gamete (1n)
Gamete (1n)
Fusion
Zygote
Isomorphic alternation of generation
Diplohaplontic Life Cycle
PLANT GROUPS CHLOROPHYTA
8
Classification of Chlorophyta
Chlorophyta divided into (14) orders:
Order: Volvocales
Member of this order are Unicellular & Coenobial which are normally motile by
means of flagella.
1 Order Volvocales
2 Order Chlorosarcinales
3 Order Tetrasporales
4 Order Chlorococcales
5 Order Chlorellales
6 Order Zygnematales
7 Order Odeogoniales
8 Order Ulotricales
9 Order Chaetophorales
10 Order Chladophorales
11 Order Acrosiphoniales
12 Order Ulvales
13 Order Siphonales
14 Order Caulerpales
Coenobium a Colony of cells firmly allached to each other in which there is some
degree of co-ordination
PLANT GROUPS CHLOROPHYTA
9
In life cycle of these members temporary resting stage, Palmella stage may occurs.
Member of this order represent most primitive, plant life which are widely
distributed in fresh water & soil. Some members are found in brackish & marine
waters. Volvox is known to cause water blooms.
Unicellular Volvocales
Family Chlamydomonadaceae
Genus Chlamydomonas
The Chlamydomonas cell represents most primitive member of living
green plants. It’s widely distributed in variety of habitats mainly in fresh water or
on moist water few species are found in brackish waters. Chlamydomonas
halophile & Chlamydomonas nivalis represent snow algae is found in the
Polar Regions imparting red colour. The red colour is due to red pigment
Haematochrome.
Solitary free swimming cell maybe ellipsoidal, sub cylindrical, spherical or
pyriform, two equal Acronematic flagella are located in the anterior region of the
cell which is responsible for motility. Cells have delicate to massive cup shaped
chloroplast. There is usually one Pyrenoid within a chloroplast. Usually there are
two contractile vacuoles near the base of flagella. A single nucleus lies in the
colourless cytoplasm.
The Stigma or red eye spot is embedded at one side of chloroplast & is
composed of carotenoid subunits about 75nm in diameter it maybe circular or oval.
Positive photo taxis.
PLANT GROUPS CHLOROPHYTA
10
In asexual reproduction the cells of most species become non motile & their
nucleus undergo one or more Mitosis which are followed by Cytokinesis. In this
way (2, 4) or more young cells are formed within parental wall from which they
ultimately escape by rupture of the wall. Released young cells similar than the
parent which gradually enlarge to normal size & repeat the asexual cycle.
Chlamydomonas may also form Aplanospores, Hypnospores & Akinetes.
Sexual reproduction involves fusion of two haploid sexual units forming
diploid cell or Zygote. Some species are Homothallic (Self-compatible) & others
are Heterothallic (Self-incompatible) Gametic union maybe Isogamous, An
Isogamous or Oogamous.
Chlamydomonas
PLANT GROUPS CHLOROPHYTA
11
Coenobial Volvocales
Family Volvocaceae
Genus Volvox
Is to be most evolved of Coenobial form the colony is spherical & appears as
small pin head on the surface of water. The colonies of most of the species are
visible to naked eyes.
The colonies are composed of many small vegetative or somatic cells, & a
few larger flagellate reproductive cells (Gonidia). Cells number of colonies in
different species ranges from (500-50000) cell per colony.
Life cycle of Chlamydomonas
PLANT GROUPS CHLOROPHYTA
12
Colonies are spherical to ovoid & the biflagellate cells lie in single layer
within gelatinous colonial matrix. Each cell is surrounded by gelatinous sheath of
its own. In some species cells are joined to one another by conspicuous or delicate
cytoplasmic strands. The whole Coenobium moves & rotates by means of flagella
of individual cells. Most of the cells in a coenobium are vegetative & do not have
the capacity to form new individuals. Each vegetative cell is biflagellate with to
contractile vacuoles near the base of flagella. Other features of cells are cup shape
to laminate chloroplast, single Pyrenoid centrally located single nucleus &
anteriorly arranged eye spot.
For asexual reproduction few cells of Volvox coenobium differentiated as
asexual reproductive cells (Gonidia) by growing larger with disappearance of
flagella & gradually thickening, a number of daughter cell are produced by the
division & re division of gonidium which are held together as a new colony. Since
the number of Gonidia divide at the same time many new colonies are formed
simultaneously.
Sexual reproduction is strictly Oogamous. Depending on the species &
strains coenobia may contain ether eggs or sperms (Dioecious) or they may contain
both (Monoecious).
Both kinds of gametes are development from cells of the posterior half of the
coenobia. The egg cells are usually dense & darker in appearance than Gonidia
they enlarge without undergoing any division & loss their flagella during
development. Cells forming Antherozoids divide successively giving arise to
numerous spindle shaped biflagellate Antherozoids.
Non motile female gametes are much larger than the male gametes &
surrounded by a gelatinous sheath. The groups of sperms are liberated from their
PLANT GROUPS CHLOROPHYTA
13
parent colonies & presumably by chemotactic stimulation swim to the surface of
female colonies, finally one sperm penetrate female colony & fertilize the egg. The
resulting zygote very soon develop thick wall & become red, zygote divides by
meiosis & a new coenobium is formed through the formation of single zoospore.
Coenobium of Volvox
Life Cycle of Volvox
PLANT GROUPS CHLOROPHYTA
14
Order: Chlorococcales
This order contains non motile unicellular & colonial green Algae. Cell wall
is usually thin & there is no vegetative cell division. Cells lack flagella, contractile
vacuoles & eye spot. Asexual reproduction is achieved by Zoospores,
Aplanospores, Autospores & daughter coenobia. Sexual reproduction is by Iso or
anisogametes. These Algae are mainly present in fresh water reservoirs & in
terrestrial situations.
Division Chlorophyta
Class Chlorophyceae
Order Chlorococcales
Family Chlorellaceae
Genus Chlorella
This genus is found in various habitats. It is mainly present as plankton form
in fresh water, bodies & on terrestrial habitats rich in organic matter. Some species
are common on sub aerial habitats, Symbiotic association of Chlorella species
with Lichens & Animals (Hydra) are also found.
Cells are usually solitary or sometimes aggregated in groups being
enveloped by mucilage. The cells are small, spherical or ellipsoidal. Each cell
possesses a single parietal & usually Cup shaped chloroplast with one Pyrenoid.
Cells have thin cellulosic wall, centrally placed small nucleus & other Eukaryotic
organelles.
PLANT GROUPS CHLOROPHYTA
15
Chlorella is an important tool for physiological experiments. It has widely
been used in the study of respiration & photosynthesis. It is also used for
purification of air in space capsules. An antibiotic Chlorellin is extracted from
this Alga. Chlorella is the first Alga to have been grown extensively in axenic
culture.
Cells have very high food value with about 50% proteins, 20% fats & 20%
carbohydrates & rich in amino acids & vitamins. Because of this, Scientists in
different countries are trying to cultivate it on mass scale. It may act as food of
future.
Reproduction is exclusively Asexual which is achieved by the production of
Autospores, 4, 8, 16 Autospores are produced by the division of mature cells &
are liberated by rupture of the parent cell wall. These non-motile spores develop
into new individuals.
Chlorella
PLANT GROUPS CHLOROPHYTA
16
Colonial Chlorococcales
Division Chlorophyta
Class Chlorophyceae
Order Chlorococcales
Family Chlorellaceae
Genus Scenedesmus
Usually consists of a linear series of 4 or 8 cells (Sometimes 2-32)
coenobium. Cells joined together by the localised production of mucilage. This
genus is widely used in physiological studies outer cells of which frequently have
spines or projections.
Scenedesmus quadricauda
PLANT GROUPS CHLOROPHYTA
17
Division Chlorophyta
Class Chlorophyceae
Order Chlorococcales
Family Chlorellaceae
Genus Pediastrum
Pediastrum is a common planktonic genus which consists of flat plate of
cells varying from 2-128 depending upon the species. The outer cells have
projections on the surface.
A number of biflagellate Zoospores are produced during asexual
reproduction. These are liberated in a vesicle within which they lose their flagella
& become arranged in the form characteristic of the present colony. The
biflagellate gametes are produced in the same way as Zoospores but are liberated
from the vesicle before fusing.
Pediastrum