MORPHOLOGY CELL STRUTURE REPRODUCTION LIFE CYCLE

1. Dr. Saurabh Kumar, HOD, Botany, KCMT
Ectocarpus
Occurrence
It is a marine brown alga found throughout
the world, particularly abundant along the
Atlantic coast.
A few species occur in fresh water.
The plant grows attached to rocks and
stones along coasts and consist of tufts of
brownish, delicate highly branched
filaments.
Some species are epiphytes on other algae.
Some of the common Indian species are E.
coniferus, E. indicus, and E. arabicus.
Ectocarpus fasciculatus grows on the fins of
certain fishes.

2. Dr. Saurabh Kumar, HOD, Botany, KCMT
Structure of thallus
The thallus consists of profusely branched uniseriate
filaments.
Ectocarpus shows heterotrichous habit, consisting of a
prostrate and erect system.
The filaments of the erect system arise from the filaments of
prostrate system.
Prostate system: The prostrate system consists of creeping,
irregularly branched filaments.
These filaments are attached to the substratum with the help
of rhizoids.
Erect system: The erect system arises from the prostrate
system.
It consists of well branched filaments.
Each branch arises beneath the septa. The main axis and the
branches of the erect system are uniseriate. Branches
terminate into an acute point to form a hair.

3. Dr. Saurabh Kumar, HOD, Botany, KCMT
Cell Structure: Cells are cylindrical or rectangular and uninucleate. Cell wall is
thick, composed of three layers of pectin and cellulose. Algin and fucoidan are also present
in the cell wall. These are characteristic gelatinous substances present in the brown algae.
The chromatophores may be ribbon-like with irregular outline or disc-shaped. The
dominant pigment is fucoxanthin. It gives this algae golden brown color. The other
photosynthetic pigments are chlorophyll a, c, beta-carotene and other xanthophylls.

4. Dr. Saurabh Kumar, HOD, Botany, KCMT
Growth :
In erect system growth is trichothallic.
Intercalary meristem is present at the base of the hair.
It is called trichothallic meristem.
It increases the length of the terminal hair and
vegetative cell of the branch.
The growth in the prostrate system is apical.

5. Dr. Saurabh Kumar, HOD, Botany, KCMT
Reproduction:
In Ectocarpous the reproduction takes place
by asexual and sexual methods.
Asexual reproduction
The asexual reproduction takes place by the
formation of biflagellate zoospores.
These zoospores may be haploid
meiozoospore or gonozoospores produced
in one- celled unilocular sporangia.
Or they may be diploid formed in many-
celled plurilocular sporangia.
Both kinds of sporangia are present on the
same diploid sporophyte plant.
The sporangia are borne terminally and
singly on lateral branches.

6. Dr. Saurabh Kumar, HOD, Botany, KCMT
Unilocular Sporangia (one-celled
sporangia) These are borne singly on lateral
branches.
Each sporangium is a stalked, globular, oval or
pear- shaped structure having dense cytoplasm
with many chromatophores and diploid nucleus.
Diploid nucleus divides meiotically into many
haploid nuclei (32-64), each of which changes into
a zoospore.
Each zoospore is small, pear-shaped and haploid
structure with two laterally attached flagella.
Zoospores develop into haploid sexual plant.
Development of Unilocular
Sporangium.
The unilocular sporangia develop from the apical
(terminal) cell of the lateral branches which
increase considerably in size to take on a globose

7. Dr. Saurabh Kumar, HOD, Botany, KCMT
The number of chromatophores also increases within the developing
sporangium.
The diploid nucleus of the initial cell first undergoes meiosis, followed
by several mitotic divisions to produce 32 to 64 haploid daughter nuclei.
There is then cleavage of the cytoplasm to form as many uninucleate
daughter protoplast units, with single chromatophores and haploid
nuclei.
Germination of meiozoospores
After swimming for a while, each meiozoospore on contact with
suitable substratum withdraw its flagella, becomes rounded and
secretes a membrane around it.
Within short time, a germ tube is formed, which divides many times
and forms a prostrate filament.
Some cells of the prostrate filament become active and form erect
filaments.
The plants developed on the germination of these haploid
meiozoospores are gametophytes or sexual plants in the life cycle.

8. Dr. Saurabh Kumar, HOD, Botany, KCMT
These are also formed on diploid plants at the ends of small
branches.
These are elongated cone-like structures, made up of many
small cubical cells or compartments arranged in vertical rows.
Diploid nucleus of each compartment changes into a single
diploid zoospore which again gives rise to diploid plant on
germination.
Development of plurilocular sporangia: These
are elongated, conical, multicellular bodies, developed singly on
diploid (2n) or asexual (sporophytic) plants.
They develop initially like unilocular sporangia at the tip of short
lateral branches.
The apical cell enlarges and functions as sporangial initial
(mother cell).
This sporangial initial becomes enlarged and contains numerous
chromatophores.
Plurilocular (neutral) Sporangium

9. Dr. Saurabh Kumar, HOD, Botany, KCMT
It then undergoes repeated mitotic divisions, forming 6-12 cells
in a vertical row.
The cells than undergo several vertical divisions, as a result of
which a multicellular cone-like structure, consisting of several
hundred small cubical cells, arranged in 20-40 transverse tiers,
is produced forming a plurilocular sporangium .
Protoplast of each compartment metamorphoses into a single
biflagellate zoospore.
There is no reduction division during the formation of zoospore
in plurilocular sporangium.
So each small cubical cells of plurilocular sporangium contains a
single diploid nucleus that metamorphoses into a single,
uninucleate (2n) and biflagellate zoospore.
The zoospores formed from plurilocular sporangia are similar to
meiozoospores developed in unilocular sporangia, but are diploid.
The zoospores from a sporangium liberate through an apical or
lateral aperture,
On germination each produces a sporophytic (2n) plant.

10. Dr. Saurabh Kumar, HOD, Botany, KCMT
Sexual Reproduction Sexual reproduction in Ectocarpus takes place by isogamy or
anisogamy.
Majority of the species are isogamous and homothallic. Some species are anisogamous.
Ectocarpus secundus is heterothallic and anisogamous.
The gametes are produced in plurilocular gametangia. These gametangia are many-celled,
elongated, and sessile or shortly stalked conical structures. Gametangia are produced on the
haploid plants developing from the meiozoospores.
The development of gametangia is similar to that of plurilocular sporangia. These develop
from terminal cell of a lateral branch. The gametangial initial gets inflated.
It divides mitotically by repeated transverse divisions. It produces a vertical row of flat
cells. These cells undergo repeated vertical and transverse divisions.
They form many hundred small cubical cells. These cells are arranged in 24-40 transverse
rows.
The protoplast of each cell metamorphoses into a single, pyriform, biflagellate, haploid
gamete. The flagella are laterally attached. The zoospores and the gametes are similar in
structure. But the gametes are relatively smaller in size. The gametes are liberated through an
apical pore formed in the gametangium .

11. Dr. Saurabh Kumar, HOD, Botany, KCMT
Isogamy Physiological anisogamy Morphological Anisogamy
Isogamous species are E. pusilus
and E. globifer etc.
In these species, the fusion takes
place between alike gametes.
These gametes belong to the same
plant or even to the same
gametangium.
It occurs in species like E.
siliculosus.
The fusing gametes are identical
morphologically. But they show
different sexual behavior. One is
less active and is called female
gamete. The other is more active
and is called male gamete. The
female gamete soon comes to
rest. It settles on a substratum. It
becomes surrounded by active
male gametes. The male gametes
attach themselves to the female
gamete through their anterior
flagella. The anchoring
flagellum contracts, the body of
one of the male gametes comes
in contact with that of the female
gamete and the fusion takes place.
This phenomenon is called
clump formation.
It occurs in species like E.
secundus.
In this case, the two fusing
gametes are dissimilar in size.
They are produced in different
gametangia:
The smaller ones are produced in
microgametangia.
The larger ones are produced in
megagametangia.
Forms of Sexual Reproductions
Fertilization: After fertilization diploid zygote is formed. There is no zygotic meiosis. The
zygote germinates into a diploid sporophyte.

12. Dr. Saurabh Kumar, HOD, Botany, KCMT
Isogam
y
Physiological
anisogamy Morphological

13. Dr. Saurabh Kumar, HOD, Botany, KCMT
Alternation of Generations:
Ectocarpus shows isomorphic alternation of generations.
There is alternation of morphologically similar gametophytic (haploid) and sporophytic
(diploid) generations in its life cycle. ( Sporophyte: The sporophyte is diploid. It develops two
types of sporangia. Zoospores are produced in these sporangia).
Zoospores are produced by mitosis (mitozoospores) in plurilocular sporangia. The zoospores
in unilocular sporangia are produced meiotically (meiozoospores).
The mitozoospores germinate into a diploid sporophyte. These spores cause reduplication
of sporophyte generation.
The meiozoospores germinate to give rise a haploid gametophyte plant. Gametophyte: It
develops plurilocular gametangia.
These gametophytes are similar to the sporophyte in morphology. Haploid gametes are
produced in the gametangia. These gametes fuse to form a diploid zygote. Zygote
germinates into a diploid sporophyte plant. In some species the gametophyte generation is
also reduplicated by the parthenogenesis. In this case, the gametes from plurilocular
sporangia form new gametophyte generation.)

14. DR.SAURABH KUMAR
HOD, Department of Botany
Khandelwal college of Management Science &
Technology
Bareilly.
Dr. Saurabh Kumar, HOD, Botany, KCMT