PINNULARIA

1. Vaucheria
Occurrence: It is found in temperate regions and comprises of about 45 species. Most of the species occur in fresh
waters (streams, springs and water falls) or found in damp soils. A few species, e.g, Vaucheria pilobolides are marine.
Plant body: The thallus consists of branched cylindrical filament. The filament is non septate multinucleated structure.
Septa are produced only during the production of reproductive structure.
Hepteron: The plant is attached to the substratum by colorless branched, short
rhizoids called as hepteron.
Cell wall: The cell wall is thin and consists of cellulose and pectin.
Vacuole: Tubular filament contains a large central vacuole filled with cell sap.
Chloroplast: The chloroplast is small discoid shaped structure without pyrenoids.
Reserve food: Reserve food material is in the form of oil drops.
Reproduction: Vaucheria reproduces by vegetative, asexual and sexual means.
Vegetative Reproduction:
Vegetative reproduction in Vaucheria takes place by fragmentation. The filaments are broken accidentally into
fragments, each of which develops into a new plant. However, this mode of reproduction is not common.
Asexual Reproduction:
In aquatic species the asexual reproduction takes place by multiflaggelate
zoospores whereas in terrestrial species it is by aplanospores.
Aplanospores:
Aplanospores are non-motile spores that are formed singly inside structures called
aplanosporangium. They are formed during unfavourable conditions at the apical
side of aerial hyphae. The aplanosporangium are club-shaped and non-flagellated
structures that are separated from the rest of the thallus by a transverse septum.

2. The aplanospores rupture the cell wall of the aplanosporangium and develop into new filaments.
Zoospores:
Zoospores are flagellated asexual spores that are born singly inside zoosporangium.
Zoosporangia are green-coloured and club-shaped structures that are formed at the apical region of the filaments by
forming a cross-wall from the rest of the filament. At the time of the liberation of the spore, the protoplast of the
zoosporangium contracts, forming a narrow aperture, from which the zoospores are released. The zoospores become
flagellated after liberation.
The zoospores are yellowish-green, multiflagellate, multinucleate and ovoid structures that have a small central
vacuole. They are also referred to as compound zoospores.
Sexual Reproduction:

3. Sexual reproduction in Vaucheria is of oogamous type. The male sex organ
is known as antheridium and the female sex organ is known as oogonium. The
plant body of Vaucheria can either be homothallic meaning both the male
and female sex organs are born close to each other on the same filament
or heterothallic such that male and female sex organs are born on different
plants.

4. Antheridium:
A mature antheridium is usually cylindrical structure that develops before oogonium development in most species. It
develops close to oogonium. The branch bearing the antheridium becomes densely packed with nuclei and few
chloroplasts, therefore the antheridium is often colourless. Later on this branch is cut off from rest of the thallus by
a transverse septum. Inside the antheridium, the nuclei divide mitotically and give rise to biflagellated and spindle
shaped antherozoids. The flagella are dissimilar. one is whiplash and one is tinsel. The antheridium opens at the
apex, antherozoids are released and reached the oogonium.
Oogonium:
The development of the oogonium starts near the antheridium with a bulging in the main filament. A large mass
of colourless cytoplasm called wanderplasm has many nuclei and chloroplasts move into this bulge. The bulge
increases in size and becomes an oogonium. The oogonium is separated from the main filament by the formation
of a transverse septum. At one side of the oogonium a beak called the receptive spot develops. Apical pore is
formed at the apex of the beak through which the antherozoids can enter the oogonium.
Fertilization:
At the time of fertilization the beak of the oogonium ruptures and an aperture is formed in the antheridium.
The oogonium releases a small amount of cytoplasm through the ruptured beak and as a result many
antherozoids get stuck in the liquid but only one enters the oogonium. The antherozoids lose their flagella upon
coming in contact with the ovum and fuse with it to form a diploid zygote. The zygote secretes a thick wall
around it to become an oospore.
Germination of oospore:
The oospore undergoes a period of rest for some months before germination. On germination it produces a new
filament directly

5. Pinnularia:
Habitat:
It is a fresh water alga. It is found in pond. It is also
present on the moist soil.`
Structure:
It is unicellular. Its cell is elongated and elliptical.
Cell wall:
The cell wall is made up of pectic substances. Silica is
impregnated in it. So the cell became very hard. Cell wall
is composed of two halves called valves. These halves
overlap like petridish. The margins of the two valves are
covered by a connecting band.
The two valves with their inner protoplasts are called frustule. The frustule has two views . The
surface view is called valve view and band view is called girdle view . The outer larger valve is called
epitheca. The smaller inner valve is called hypotheca. The surface of valve has minute pores or pits
. It produces characteristic markings on the surface of valves . These markings are bilaterally
symmetrical. The marking free area is called axial field . The markings are arranged in linear rows .

6. The axial field contains a longitudinal slit called raphe.
The raphe is not continuous throughout the length of
the valve .
The raphe is wedge shaped in transverse section. It has
circular thickening called central nodules in the centre.
Similar thickening also present at the outer ends of
raphe . These are called polar nodules . These nodules
open to the external aqueous medium

7. Cytoplasm:
Cytoplasm is arranged in a parietal layer. A large central vacuole is present inside the cell.
Nucleus:
The single nucleus is suspended in the centre of vacuole by a cytoplasmic bridge.
Chloroplast:
Two chloroplast are present along the two sides of the cells. They contain chlorophyll a, c, beta
carotene, fucoxanthin and diatomin pigment. Fucoxanthin gives the alga characteristic colour. The
plastids are few in number. Excess food is stored in the form of oil or chrysolaminarin.
Locomotion:
Locomotory organs are absent in pinnularia. It moves by gliding movements. Circulation of the
streaming cytoplasm causes this movement. Mucilage helps in this gliding.
Reproduction:
Vegetative and sexual reproduction are present in it .

8. Vegetative reproduction:
It is the most common method of reproduction. It
produces daughter cells slightly different in sizes.
Vegetative reproduction occurs by simple cell
division. The protoplast expands. It causes slight
separation of epitheca and hypotheca.
Nuclear division occurs by mitosis and cell divides into
two parts. Each half receives one half of the parent
cell. It synthesizes new valve. New valve is fit into the
parent valve. Thus new valves are always smaller than the parent halves. Thus one generation gradually
become smaller in size. It reacted to minimum size. Then its size is restored by auxospore formation.
But second generation remains of same size.
Sexual reproduction (Auxospore formation).

9. 1. Gamete formation:
In some species of Pinnularia, two cells from common
parent or different parents envelope in a common
mucilaginous sheath. The nuclei of both cells divide by
meiosis to form four nuclei. Three nuclei disintegrate.
The fourth one enlarges. Its protoplast metamorphosed
into gamete. The gametes are liberated from the parent
frustules. They fuse to form zygote. The zygote enlarges
to form auxospore. The auxospore secretes new valve
and become adult.
2. Parthenogenesis:
The protoplast of cell secretes a large amount of mucilage. Therefore two valves are separated from
each other. It separates the inner protoplast. The protoplast grows to its maximum size. It secretes silica
rich pectic membrane. New valves are secreted inside the membrane. Nuclear division does not occur.
Therefore auxospores are formed by parthenogenesis.

10. Ectocarpus:
Occurrence:
It is a marine brown alga. It is abundantly found in cold water. A few species occur in fresh water.
The plant grows attached to rocks and stones along coasts. Some species are epiphytes on other
algae like members of Fucale’s and laminaria.
Plant body:
Plant body is filamentous and branched. There are two types of filaments, the prostrate and erect
filament.
Prostrate filament:
The prostrate system is branched and attached to the
substratum with the help of rhizoids. In epiphytic
species this system occasionally penetrates the host. In
free floating species the prostrate system is poorly
developed.
Erect filament:
The erect branches are arranged end-to-end, such that
they are polysiphonous in nature. Sometimes, the erect
branches may grow vertically to form more than one
row of cells.

11. Growth of thallus:
The growth of thallus in primitive brown algae is by an intercalary meristem at the base of a hair or
filament. This type of growth is called trichothallic growth.
Cell structure:
The cells are rectangular or cylindrical. Cell wall is differentiated into outer pectic and inner cellulosic
layers. The outer layer becomes slimy or gummy due to presence of pectic compounds. The most
important constituent of the cell wall is alginic acid found in the outer layer of the cell wall. It forms a
substance algin which is important
economically. The reserve food is mannitol
and laminarin starch.
It is golden brown in colour due to presence
of dominant fucoxanthin. The other
photosynthetic pigments are chlorophyll a,
c, beta carotene and other xanthophylls. The
protoplast contains one central nucleus and
many chromatophores. The number and
shape of chromatophore varies with
species. Pyrenoid are associated with
chromatophores.

12. Reproduction:
Ectocarpus reproduces asexually by zoospores and sexually by isogamy or
anisogamy. The oogamous type of sexual reproduction is absent.
Asexual Reproduction:
The asexual reproduction takes place by zoospores. The zoospores are biflagellate.
The diploid plant (2n) develops two types of sporangia. unilocular sporangia and
plurilocular sporangia. The unilocular sporangia develop haploid zoospores and
plurilocular sporangia develop diploid zoospores.
Unilocular Sporangia:The unilocular
sporangia develop from the apical cell of
short lateral branches. The cell enlarges and
functions as sporangial initial. The nucleus of
the sporangium undergoes meiosis followed
by several mitotic divisions to produce 32-64
daughter nuclei. These nuclei accumulate
some cytoplasm and
develop individual units. Each unit
metamorphoses into a uninucleate and
biflagellate zoospore also called meio

13. zoospore. The flagella are unequal and laterally inserted.
During liberation the apex of the sporangium wall gets dissolved and the haploid
zoospores are liberated in a gelatinous mass.
After some time they get free from the gelatinous mass and swim freely in water. After
the liberation of zoospores a new sporangium may be produced within the old
sporangial wall.
Plurilocular Sporangia:
These are elongated multicellular structures that develop at the tip of short lateral
branches. The sporangial initial becomes enlarged and undergoes repeated mitotic
divisions to produce a vertical row of 6-12 cells. The cells then undergo several vertical
divisions thus a multi chambered structure is formed i.e., the plurilocular sporangium.
The protoplast of each cell metamorphoses into diploid biflagellated zoospore.
The zoospores are liberated through a terminal or a lateral pore formed in the wall of
the sporangium.
Sexual Reproduction:
Majority of the species are isogamous and homothallic. The gametes are produced
inside the plurilocular gametangia, developed on haploid plants.

14. Plurilocular Gametangia:
These are large, elongated and multicellular structures.
Both plurilocular gametangia and plurilocular sporangia
are alike. The plurilocular gametangia produce haploid
gametes while plurilocular sporangia produce diploid
zoospores.
The gametes are slightly smaller in size than the
zoospores. The gametes are liberated from the
gametangia following the same procedure as that of
zoospore liberation from the plurilocular sporangia.
Fertilization and Germination of zygote:
Fertilization results in a diploid zygote. The zygote germinates into a diploid sporophyte
without undergoing any resting
period. The sporophytic plant again
develops unilocular and plurilocular
sporangi