• Chara is fresh water green algae found submerged in shallow water ponds, tanks, lakes and slow running water.
• Chara is found mostly in hard fresh water, rich in organic matter, calcium and deficient in oxygen.
• Chara plants are often encrusted with calcium carbonate, and hence commonly known as stone wart.
2. SYNOPSIS
o Systematic position
o Habit and habitat
o Morphology
o Thallus structure
- Rhizoids
- Main axis
o Cell structure
o Reproduction
- Vegetative Reproduction
- Sexual Reproduction
o Life cycle
3. SYSTEMATIC
POSITION
Division - Charophyta
Class - Chlorophyceae
Order - Charales
Family - Characeae
Genus - Chara
DISTRIBUTION:
Chara has a cosmopolitan distribution. They are
commonly found in hard - mesotrophic waters with
benthic vegetation
In India, Chara is represented by about 30 species of
which common Indian species are C. zeylanica, C.braunii,
C. gracilis, C. hatei etc..
4. HABITAND
HABITAT
Chara is fresh water green algae found submerged in
shallow water ponds, tanks, lakes and slow running
water
Chara is found mostly in hard fresh water, rich in
organic matter, calcium and deficient in oxygen
Chara plants are often encrusted with calcium
carbonate, and hence commonly known as stone wart
Some species are found in brackish water like C.
baltica, C. fragilis found in hot springs
Species such as C. hatei grows trailing on the soil, C.
nuda and C. grovesii are found on mountains, C.
wallichii and C. liydropitys are found in plains
Chara often emits disagreeable onion like odour due to
presence of sulphur compounds
The fossils of alga have been discovered from paleozoic
era
5. MORPHOLOGY
The plant body is a gametophyte
It consists of a main axis (differentiated into nodes and
internodes)
Dimorphic branches (long branch of unlimited growth
and short branches of limited growth)
Rhizoids (multicellular with oblique septa)
Stipulodes (needle shaped structures at the base of
secondary laterals)
6. THALLUS
STRUCTURE
The thallus of Chara is branched, multicellular and
macroscopic. The thallus is normally 20-30 cm in
height but often may be up to 90 cm to l m
Some species like C. hatei are small and may be 2-3
cm long. The plants in appearance resemble Equisetum
hence Chara is commonly called as aquatic horsetail.
The thallus is mainly differentiated into rhizoids and
main axis
7. Rhizoids
The rhizoids are white, thread like, multicellular,
uniseriate and branched structures. The rhizoids
arise from rhizoidal plates which are formed at the
base of main axis or from peripheral cells of lower
nodes
The rhizoids are characterized by presence of oblique
septa. The tips of rhizoids possess minute solid
particles which function as statoliths. The rhizoids
show apical growth
Rhizoids help in attachment of plant to substratum
i.e., mud or sand, in absorption of minerals and in
vegetative multiplication of plants by forming bulbils
and secondary protonema
8. MainAxis
The main axis is erect, long, branched and differentiated into nodes and
internodes. The internode consists of single, much elongated or oblong
cell
The inter-nodal cells in some species may be surrounded by one celled
thick layer called cortex and such species are called as corticate species
The species in which cortical layer is absent are called ecorticate species.
The node consists of a pair of central small cells surrounded by 6-20
peripheral cells. The central cells and peripheral cells arise from a single
nodal initial cell
On nodes develop these following four types of appendages:
Branches of limited growth
Branches of unlimited growth
Stipulodes
Cortex
9. Branches of limited growth
The branches of limited growth arise in whorls of 6-20 from
peripheral cells of the nodes of main axis or on branches of
unlimited growth. These are also called branchlets, branches of
first order, primary laterals or leaves
These branches stop to grow after forming 5-15 nodes and hence
are called branches of limited growth. The stipulodes and
reproductive structures are formed on the node of these
branches
Branches of unlimited growth
The branches – of unlimited growth arise from the axils of the
branches of limited growth hence these are also called auxiliary
branches or long laterals. These are differentiated into nodes
and internodes
At nodes they bear primary laterals and these branches look like
the main axis. Their growth is also unlimited like main axis
10. Stipulodes
The basal node of the branches of limited growth develops short,
oval, pointed single cell outgrowths called stipulodes. In most of
the species of Chara e.g., C. burmanica are bi-stipulate
In some species of Chara e.g., C. nuda and C. braunii are
unistipulate. When stipulodes are present in one whorl at each
node the species are called as haplo - stephanous and with two
whorls on each node are called diplo - stephanous
Cortex
Many species of Chara e.g., C. aspera, C. inferma have inter-nodal
cells of main axis ensheathed by cortex cells. Such species are
called corticated species
The cortex consists of vertically elongated narrow cells. The
internode up to half of its length by corticating filaments
developed from upper node called descending the lower half of
internode is covered by filaments developed from lower node
called filaments. The ascending and descending filaments meet at
the middle of internode. The species without cortex e.g., C.
corallina are called ecorticated species
11. CELL
STRUCTURE
The main axis of Chara consists of mainly two types of
cells:
Nodal cells - The nodal cells are smaller in size and
isodiametric
The cells are dense cytoplasmic, uninucleate with few
small ellipsoidal chloroplasts
The central vacuole is not developed instead many
small vacuoles may be present. The cytoplasm can be
differentiated in outer exoplasm and inner endoplasm
12. Inter - nodal cells - The inter-nodal cells are much elongated. The
cytoplasm is present around a large central vacuole
The cells are multinucleate and contain many discoid chloroplasts.
The cytoplasm is also differentiated into outer exoplasm and inner
endoplasm
The endoplasm shows streaming movements. The cell walls
between the nodal cell and inter-nodal cells are porous to help in
cytoplasmic continuity between cells
13. REPRODUCTION
Reproduction in Chara takes place by vegetative and sexual
methods. Asexual reproduction is absent.
Vegetative Reproduction in Chara
It takes place by the following methods
Amorphous bulbils
The amorphous bulbils are group, many cells, irregular in shape
which develop on lower node main axis e.g., C. delicatula or on
rhizoids e.g., C. fragifera and C. baltica. The amorphous bulbils
are perennating structures, when the main plant dies under
unfavourable conditions; these bulbils survive and make Chara
plants on return of favourable conditions
Secondary protonema
These are tubular or filamentous structure which develops from
primary protonema or the basal cells of the rhizoids. The
secondary protonema like primary protonema form Chara plants
14. Bulbils
The bulbils are spherical or oval tube-like structures
which develop on rhizoids. In C. aspora or on lower
nodes of main axis e.g., C. baltica. The bulbils on
detachment from plants germinate into new thallus
Amylum stars
In some species of Chara e.g., C. stelligna, on the lower
nodes of main axis develop multicellular star shape
aggregates of cells. These cells are full of amylum starch
and hence are called Amylum stars. The amylum stars do
detachment from plants develops into new Chara thalli
15. SEXUAL
REPRODUCTION
Sexual Reproduction in Chara
The sexual reproduction in Chara is of highly advanced
oogamous type. The sex organs are macroscopic and
complex in organization
The male sex organs are called antheridium or globule
and the female oogonium or nucule. Most of the Chara
species are homothallic i.e., the male and male sex
organs are borne on the same nodes e.g., C. zeylanica.
Some species e.g., C. wallichii are heterothallic i.e.,
male and female sex organs are borne on different
plants
The sex organs arise on the branches of limited growth
or primary laterals, the nucule above the globule. The
development of globule and nucule takes place
simultaneously but species globule matures before
nucule
16.
17. Globule
The globule is large, spherical, red or yellow
structure. The mature globule is made up of 8 curved
shield cells, 8 elongated manubrial cells, 8 centrally
located primary capitulum cells and 48 secondary
capitulum cells
The secondary capitulum cells give rise to many
antheridial filaments. Each sperm mother cell forms
a single bi-flagellated antherozoid
Liberation of Antherozoids
At maturity the shield cells of antheridium separate
from each other exposing antheridial filaments in
water. The sperm mother cell gelatinizes to liberate
the antherozoids
18. Nucule
The Nucule of Chara is large, green, oval structure with short stalk. It is
borne at the node of the primary lateral. It lies just above the globule in
homothallic species
The mature Nucule is attached to the node by the pedicel cell. The Nucule
is surrounded by five tube cells. The tips of tube cells from corona at the
top of nucule.
The oogonial cell possesses a single large egg or ovum. The Nucule contains
large amount of starch and oil. The receptive spot is present at the upper
part of Nucule
Fertilization
When the oogonium is mature, the five tube cells get separated from each
other forming narrow slits between them
Antherozoids are chemotactically attracted towards ovum. The
antherozoids enter through these slits and penetrate gelatinized wall of
the oogonium.
Many antherozoids enter oogonium but one of those fertilizes the egg to
make a diploid zygote. The zygote secretes a thick wall around itself to
make oospore
20. Oospore
The mature oospore is hard, oval, ellipsoid
structure which may be brown e.g., C. inferma,
black e.g., C. corallina or golden brown e.g., C.
flauda. The oospore inside contains a diploid
nucleus and many oil globules in cytoplasm.
On maturity of oospore the inner walls of tube
cells get thickened, suberised and silicified. The
oogonial as well as oospore walls become thick.
The oospore nucleus moves towards the apical
region. In advanced stage the outer walls of the
envelope or sheath cells fall off and the inner
parts remain attached to mature oospore in form
of ridges.
Germination of Oospore
The oospore germinates when favourable conditions
appear. The diploid nucleus present in apical
colourless region divides by meiosis forming four
haploid daughter nuclei.
At this stage a septum divides oospore into two
unequal cells. The upper smaller apical cell contains
a single nucleus and the large basal cell contains
three nuclei. The three nuclei of basal cell
degenerate gradually. The oospore apical cell divides
by longitudinal division to make a rhizoidal initial
and protonemal initial.
The rhizoidal initial shows positive geotropism and
forms primary rhizoid, the protonemal initial shows
negative geotropism and forms primary protonema.
The primary protonema differentiates into nodes
and internodes. The peripheral cells of the basal
node give rise to rhizoids and secondary protonema.
The peripheral cells of the upper nodes give rise to
lateral branches
21. LIFECYCLE
The plant body of Chara is haploid. The vegetative
reproduction takes place by the formation of amylum
stars, bulbils and secondary protonema.
Asexual reproduction is absent. The sexual
reproduction is advanced oogamous type.
The male and female sex organs are globule and nucule
respectively. After fertilization a diploid spore is
formed.
At the time of germination diploid oospore nucleus
divides to make hapoid nuclei and haploid Chara plant.
Thus the life cycle of Chara a predominantly haploid
type
