Morphology and Reproductive structures of Chara

For PG and UG students

1. Chara (“stone worts”)

Chara grows submerged in
fresh water and upon muddy or
sandy bottoms of pools and ponds,
or in limestone streams.

Certain species have the capacity
of precipitating calcium
carbonate from the water and
covering themselves with
calcareous layers.

Clear hard water is suitable for their
growth.

Mature plant is enriched with
CaC03.

Therefore, they are called as stone

2. Structure of Chara

Plant body or thallus of chara is Multicellular, Macroscopic,
Filamentous and Branched

The plant attains a height of 20-30cm. It has divided into following
parts.

Rhizoids

Arise from lower end, branched, multicellular, no nodes and
internodes, uniseriate, obliquely septate, arise from rhizoidal
plate attached the substratum by means of rhizoids.

Branches

The thallus has long slender upright branches. The axis is
differentiated into node and internodes. From each node arise the
following four types of appendages,

1. Branchlets:
Each node bears a whorl of branches, which has limited growth.

3. 2. Long Branches:

There are one or two branches of
unlimited growth may also be
present in each node. They arise
singly at the older nodes of the main
axis, They often called as axillary
branches. The axillary branch
continues the growth of thallus.

3, Stipuloids:
These are unicellular out growth that
arises from the basal node of each

branchlet. They are usually two in
number.

4, Cortex:

In some species, the intermodal cells

$ aa de a al |

Fig. 3.91 : Chara sp. : A. External morphology, 8. Shoot (branch) of limited arowth or primary lateral C-D. Annan.

4. Cell Structure

Young cells are always uni-
nucleated structures without
conspicuous vacuole.

In the mature cells, the vacuole
may be developed and may
become multinucleated due to
amitosis.

There are many small ellipsoidal
chloroplasts arranged
longitudinally in peripheral
portion of cytoplasm.

The Cell wall of the internodal
cell is impregnated with silica
and calcium carbonate.

The reserve food material is

ALT;

5. Growth of the Thallus

he growth of the thallus is by dome-
shaped apical cell which cuts off
lerivatives at its posterior surface

ach derivative undergoes a transverse
division to produce two daughter cells.

he upper cell acts as nodal initial and
the lower as internodal initial. The
internodal initial elongates many times
its original length and matures to form
internode of the axis.

he nodal initial divides by vertical
divisions intersecting each other to
produce two central cells surrounded by
6-20 peripheral cells.

Each peripheral cell cuts off apical cells

Fig: Growth in Chara

6. Reproduction

The Chara reproduces by vegetative and sexual reproduction.
Asexual reproduction by spore formation is absent.

Vegetative Reproduction

The vegetative reproduction in Chara involves various kinds of
reproductive bodies which on detachment from the parent
plant give rise to a new plant. The common means of vegetative
reproduction are as followings:

Amylum Stars: These are star-shaped groups of cells

developed from the lower nodes. The cells contain amylum
starch. After being detached these develop into new

plants.

Bulbils: These are small, rounded or star-shaped, tuberous
bodies that develop either on rhizoids (Chara aspera) or on
stem nodes (Chara baltica). These develop into new plant on
detachment.

Secondary Protonema: In some cases, protonema-like

antorawths arice from the node af nrimarv nratnnema ar

7. Sexual Reproduction

The sexual reproduction is an advanced oogamous.

The gametes are produced. In antheridia and oogonia
that are enveloped in multicellular sheaths formed
of cells derived from the cells present below the sex
organs.

These specialist complex structures containing the
sex organs are called globule (male fructification)
and nucule (female fructification).

Some species are dioecious while the others are
monoecious. The monoecious species are
protandrous, i. e., the male sex organs develop first.

8. Globule: me mate fructifcation is called as globule. The mature globule is bright
yellow in color. It consists of following parts. Shield cal
Pedicel cell

The globule is attached to the plant by a large cell called as pedicel cell. It extends within the

cavity of the globule and join with the primary capitula

Shield cells

Each globule is in the form of ball like structure whose wall consists of large plate like eight

cells called as shield cells, The outer wall of cach shield cell has radial out growth therefore it many,

appears as multicellular structure,
Wenubr um Sapa

On the inner side of shield-cells in the center is attached an elongated cell called as manubrium.

Primary capitula

The inner ends of manubrial cells are united to form eight isodimetric cells called as primary Pura

capitula )
econdary capitula

Each primary capitula has one or two smaller cells towards the cavity of globule called as Maren

secondary ape

Antheridial Filament

Attached to the primary or secondary capitula are several branched uniseriate filament called

as antheridial filament. Its contents are metamorphosed into a single antherozoid.
Antherozoid

Each antherozoid is an elongated somewhat coiled structure. It bears two flagella,
Liberation of Antheridia

9. Development of

The development of t
peripheral cell of the
growth, It divides by a
globule initial and an
periclinal division. The
cell and the middle o
antheridium. The basal

Globule

e globule starts from the adaxial
lower node of a branch of limited
periclinical division into an outer
inner cell that undergoes another
lowermost cell act as internodal
me forms the basal node of the
nodal cell divides to produce five

peripheral cells, the uppermost cell acting as globule

initial.

The globule Initial divi

les transversely into a basal pedicel

cell and a terminal antheridial mother cell. The pedicel
cell does not divide further rather elongates and protrudes
into the antheridial cavity. The antheridial_mother_cell
becomes spherical and divides by two vertical divisions at
right angles to each other to form a quadrat, All these cells
divide transversely to produce an octant of eight cells. Each
of these eight cells divide periclinally into an outer and an
inner cell. The cells of outer layer divide periclinally again
and as a result three layers of cells are formed lying one

10. Nucule

he female fructification is called as nucule. It consists of following
arts,

Pedicel cell
is present at the base of the nucule on which are present central and
stalk cell.

Oogonium
Upper to the stalk cell is a very much-enlarged structure called as INTER |'
oogonium. Its contents are transformed into a single large NODE ||
uninucleate egg.

Tube cells
he oogonium is covered by five clongated spirally twisted cells,

called as tube cells.

Corona
At the top of the oogonium is a crown of small five cells called the
corona.

11. Development of Nucule

The nucule initial divides twice transversely to produce a
filament of three cells.

The lowermost cell elongates and function as pedicel of the
nucule. The middle cell divides by vertical divisions to form
five sheath initials surrounding a central cell. The terminal cell
functions as oogonium mother cell. It elongates and divide
transversely into a lower small stalk cell and an upper
oogonium. The oogonium enlarges and its contents
metamorphose into a single egg.

The sheath initials elongate, grow upward, and divide
transversely to form two tiers of five cells each. The cells of
the upper tier function as corona cells and these forms the
corona of the nucule. The cells of the lower tier act as tube

cells, The tube cells elongate and twist spirally in clockwise
direction around the oogonium.

The egg becomes filled with starch and oil, its nucleus

12. Fertilization

When the nucule is Mature, the spirally twisted tube cells
separated from each other just below the corona to form five
small slits.

Antherozoids swim through these slits and enter into the
sheath of nucule. One of the antherozoid enters the egg and
fertilization is completed.

The zygote secretes a thick wall and become oospore.

The zygospore falls to the bottom of the pond and germinates
after a period of rest of few weeks or more.

13. Structure and Germination of
Oospore

The oospore germinates after a period of rest.

Its nucleus iosis to produce four h

The oospore divided into two unequal cells by a wall.

The upper cell is small and uninucleate and the lowe
larger and contains three nuclei which di

n to expose the upper cell.

It Fan by an oblique longitudinal wall into a p

which is differentiated into nodes and internodes later on.