Genus Anthoceros

Anthoceros(Gr. Antho=flower +keras=horn) is a genus of hornworts, a group of non-vascular plants that belong to the division of Bryophyta.

Hornworts are known for their distinctive, horn-like sporangia, which are the structures that produce and house spores of spores, called spores.

The genus has about 200 known species.But the most prominent are found in Himalayan areas are Anthoceros hemalyensis, Anthoceros chambensis and Anthoceros erectus.

Thallus formation:

The thallus of Anthoceros is a flat, green, lobed structure that can reach up to 15 cm in length. It is composed of a single layer of cells and lacks true roots, stems or leaves. The surface of the thallus may be smooth and velvety or contains spines or ridges. Despite this, the thallus is capable of performing photosynthesis, which is the process by which light energy is transformed into chemical energy and stored in the form of sugars.

The chloroplasts, which are the structures responsible for photosynthesis, are located in the upper layer of cells in the thallus.

Reproduction - Gametophyte

The Gametophyte reproductives by means of vegetative reproduction and sexual reproduction.

Vegetative reproduction:

Vegetative reproduction in Anthoceros is a process by which new plants are produced from vegetative structures, such as stems or leaves, rather than from seeds.

It may take place from different types of methods.

In Anthoceros, vegetative reproduction is often achieved through the production of specialized structures such as rhizomes, tubers,gemmae or spore-producing structures called sporangia.

These structures develop into new individuals that are genetically identical to the parent plant.

Sometimes, vegetative reproduction may take place on the older cells of thallus situated far away from apex and results in the formation of different branches that grow into new plant.

This method of reproduction is an efficient way for Anthoceros to spread and colonize new habitats, as well as to ensure the persistence of the species in changing environmental conditions.

Sexual Reproduction:

The reproductive system of Anthoceros is characterized by the presence of both male and female gametangia on the same individual. The male gametangia are called antheridia, and the female gametangia are called archegonia.

The antheridium is a stalked structure that produces and releases sperm cells, while the archegonium is a flask-like structure that contains an egg cell and the neck canal cells that guide the sperm cells to the egg cell.

Antheridium:

The anthredia develop in some roofed cavities called antheridal chambers found on the dorsal surface of thallus.Generally, one to twenty five anthredia may develop in each antheridal chamber.

Antheridium of Anthoceros

The antheridium is usually found on the surface of the thallus and is composed of a stalk and an antheridium proper.

The sperm cells are produced by meiosis, a type of cell division that halves the number of chromosomes in a cell.

A superficial cell present on dorsal side divides transversely to form inner cell that act as roof initial.A mucilage filld space is present between this antheridal initial.The roof initial is then converted into chamber.

As a result, the antheridal initial develops into primary antheridal and primary stock cell which further divides to produce the stock of a antheridium. The vertical divisions in primary antheridal cells give rise for daughter cells.

Thee transverse division in these daughter cells give rises the four days of 4 cells, which further divide periclinally to produce the tiers of inner primary androgonial cells and the eight outer primary jacket cells which further divides to give rise jacket layer.Finally, the repeated divisions in primary androgonial cells produce androcytes. These androcyte first divide into two cells, then each of them metamorphoses into biflagellate and heroes or male sperms😉

The antheridal has a spherical structure that contains the sperms cells. After being produced, the sperm cells are released into the water, where they are capable of swimming towards the archegonium.

Archegonium:

The archigonia is directly connected with vegetative cells and it is embedded in the thallus. The archigonia is totally naked🤭 and just the cells of it's neck are covered with cover cells.

Archegonium of Anthoceros

The archegonium is also composed of a stalk and an archegonium proper. The archegonium proper is a flask-shaped structure that contains the egg cell and the neck canal cells.The archegonium of Anthoceros resembles with the archigonium of pteridophytes.

The egg cell is the female gamete and is produced by meiosis.It develops from three intersecting vertical walls to produce three peripheral jacket initial covering the axial cell. The axial cell develops to cover initial by transverse division.The cover cell divides periclinally to form four cover cell, and a central cell. The central cell then divides into primary canal which develops in a row of 4 to 6 neck canal cells.

After all the primary went to sell divides to form mental canal cell and an egg.The neck canal cells are specialized cells that guide the sperm cells to the egg cell.

Fertilization:

Fertilization in Anthoceros occurs when a sperm cell enters the archegonium and fertilizes the egg cell. The fertilized egg cell then divides and develops into a sporophyte, which is a stage in the life cycle of a hornwort that produces spores. The sporophyte produces a capsule, which is the structure that contains the spores. The fragments are dispersed by wind and water, and when they land on a moist surface, they grow into new hornwort individuals.

Conclusion:

In conclusion, Anthoceros is a remarkable plant that is able to perform photosynthesis and produce fragments, despite the absence of true roots, stems or leaves. The reproductive system of Anthoceros is characterized by the presence of both male and female gametangia on the same individual, and fertilization occurs when a sperm cell fertilizes the egg cell.

The fertilized egg cell then develops into a sporophyte, which produces the fragments that are dispersed and grow into new hornwort individuals.

Genus Anthoceros: Introduction, Thallus formation and Reproduction

Genus Anthoceros

Thallus formation: