Anthoceros botany

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ANTHOCEROS
MANSI YADAV
ROLL NO.- 204
SECTION- C

ANTHOCEROS
Systematic Position
Kingdom Plantae
Divisions Bryophyta
Class Anthocerotopsida
Order Anthocerotales
Family Anthocerotaceae
Genus Anthoceros

≈ Cosmopolitan
≈ Mainly in temperate & tropical regions
≈ More than 200 species, 25 sp. Recorded
from India. Mostly grows in moist shady
places, sides of ditches or in moist
hollows among rocks
≈ Few species grow on decaying wood.
≈ Three common Indian species--------
≈ A. erectus, A. crispulus, A. himalayensis
Habitat & Distribution

 It occurs in moist, shaded habitats in sub-
tropical and warm temperate regions.
 The gametophyte are dorsiventral and are
often rosette-like.
 On the ventral surface, many smooth
walled rhizoids are present which help in
fixation.
 Scales and tuberculate rhizoids are
absent.
 Some species of Anthoceros are unisexual
and others are bisexual.
 The antheridia and archegonia are sunken
on the dorsal surface of the gametophyte.
 Numerous sporophytes may develop on
the same gametophyte.
Vegetative Structure: External Features

1) Thallus is not differentiated into
photosynthetic zone and storage
zone.
2) All cells are green and contain
chloroplasts.
3) Chloroplasts are associated with
pyrenoids which is a unique feature
of Anthocerotales.
4) There are no air chambers or pores.
5) Schizogenous cavities filled with
mucilage are present. These are often
inhabited by Nostoc (cyanobacteria),
which supply nitrogen through
nitrogen fixation to their host plants.
Vegetative Structure:
Internal Features

1. Fragmentation: occurs
through progressive death
and decay of posterior
portion of thallus.
2. Tubers: develop at the end
of growing seasons. Under
unfavorable conditions, they
perennate and grow in the
next growing season.
3. Gemmae: borne on short
stalks on dorsal surface and
along margins of thalli. They
detach and germinate to
produce new plants.
4. Persistent growing apices:
the apices persists through
the long summer draught
and resume growth only
with the return of favorable
condition. With the
continuous growth the cell
of persistent apex, a new
thallus develops.
Vegetative Reproduction

a. It is oogamous type.
b. Male sex organs are antheridia and
female are archegonia.
c. Many species are monoecious while
some are dioecious. Formation of sex
organs are dependent on specific
photoperiods.
d. Anthoceros being a short day plant, sex
organs develop in winters.
e. Antheridia develop much earlier to
archegonia.
Sexual Reproduction

o Occurs on dorsal surface of thallus
in an acropetal succession inside
closed cavities called antheridial
chambers.
o It is differentiated into a long stalk
and club shaped body. The stalk is
multicellular, slender and consisted
of 4 vertical rows of elongated
cells.
o The club shaped body of
antheridium has single layered
sterile jacket enclosing a mass of
androcytes which metamorphose
into biflagellate curved
antherozoids.
Antheridia

A. These are embedded on dorsal surface of thallus
in an acropetal succession near growing point.
B. The archegonial chambers are absent.
C. It is flask shaped consisted of neck and venter.
D. It contains 4-6 neck canal cells, a venter cell and
an egg.
E. At maturity, the neck canal cells disintegrate and
become mucilaginous.
F. There are no jacket cells covering the
Archegonia.
G. Cover cells or Lid cells are found at the tip of
Archegonium.
Archegonia

∂ The antherozoids swim in
water film.
∂ Some of these reach mature
archegonium.
∂ The mature archegonium is
characterized by mucilaginous
mound at its apex.
∂ The antherozoids pass through
mucilage and enter its wide
open canal.
∂ Single antherozoid fuses with
egg to form a diploid zygote.
Fertilization

The sporophyte is differentiated into 3 distinct
regions:
1. Foot: It is basal, bulbous parenchymatous
structure found deeply embedded in the
gametophyte. It helps in attaching the sporophyte
to gametophyte and in absorption of water and
nutrients from it.
2. Intermediate or intercalary zone: A narrow zone of
meristematic cells located between the basal foot
and the upper capsule. These cells help in the
continuous growth of the sporophyte.
3. Capsule: It is the fertile, major and conspicuous
part of the sporophyte which is long and
cylindrical. It is green when young, but turns grey
or brown on maturity.
Sporophyte/Sporogonium

The capsule is composed of the following structures:
1) Columella: It is central solid core of sterile cells,
consisting of 16 vertical rows of cells. It extends
from the base to almost to the tip of the capsule.
2) Sporogenous tissue: It is the mass of fertile
spore-forming cells surrounding the columella,
like a dome. At the base of the capsule, it is
single layered and called archesporial. It becomes
2-4 layered and develops into diploid spore
mother cells upwards. Towards the tip of the
capsule, the spore mother cells divide by meiosis
and produce haploid spores.
3) Capsule wall: It is the outer wall of the capsule
which is 4-6 layers in thickness. The outermost
layer is called epidermis which is interrupted by
stomata. The inner layers consist of
chlorenchymatous cells and are photosynthetic.

Anthoceros botany

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Anthoceros botany