Riccia | Introduction | Morphology | Reproduction ~ Academichunt

Riccia | Introduction | Morphology | Reproduction

The systematic position of Riccia

Class: Hepaticopsida

Order: Marchantiales

Family: Ricciaceae

Genus: Riccia SP

Riccia, a common liverwort, grows usually during the rainy season on temp walls, moist places. There are more than 130 species of Riccia distributed throughout the world. Only 22 species are found in India. All plants are terrestrial (aquatic of the opposite), but only one species is aquatic Riccia fluitans.

Vegetative structure or morphology :

The vegetative body of Riccia plant is a flat, dorsiventral thallus. It branches dichotomously, only ventral side of the thallus there are numerous scale-like structures, one-celled i.e; called rhizoids, which perform the function of the root.

Reproduction of Riccia :

Riccia reproduces both by vegetative & sexual methods.

Vegetative reproduction: Vegetative reproduction of Riccia takes place in 5 ways -

(a) By the progressive growth of the apical region, followed by death and decaying of the older portion, as a result of decay, the two lobes of the dichotomy are ultimately separated and each of them develops into an independent plant.

(b) By the formation of adventitious branches, developed from the ventral surface of the thallus.

(d) By the formation of tubes developed from the thallus.

(e) By the development of gemmae like bodies from the rhizoid tips, these bodies detach themselves from the parent thallus and give rise to new individuals.

Riccia | Introduction | Morphology | Reproduction

Life cycle:

There are two types of plants found in the life cycle of Riccia plant.

(A) Gametophytic plant

(B) Sporophytic plant

Most species of Riccia are monoecious i.e; antheridia (Male reproductive organ)and archegonia (Female reproductive organ) born on the same plant but a few are dioecious i.e; with antheridia and archegonia being born on different plants. The sex organs are born on the dorsal side of the vegetative body.

Antheridia occur in discoid areas above the general level of the thallus . Each antheridium is completely enclosed in an antheridia chamber formed by the growth of the adjacent tissues.

Each antheridium is a pear shaped body with a short stalked. It is surrounded by a single layer of sterile cells forming the wall of the antheridium. There are a relatively large nucleus and dense cytoplasm inside the antheridium. These are antherozoid mother cell or sperm mother cell. Each mother cell undergoes a single nuclear division and and ultimately produce into a single biflagellate antherozoid. When the antherozoid matured, there is a complete dissolution of the cell walls within the antheridium and are ultimately discharged.
Archegonia are also partially enclose by the overgrowth of the surrounding tissues. Each archegonium is a flask shaped body with a very short stalked and consist of two parts on enlarge vessel portion known as venter and an elongated comparatively large, tubular portion called as the neck. The neck consists of a number of (Generally 4 to 6) neck canal cells in neck portion, a hentral canal cell and a large egg or ovum at the centra of the venter portion.

When the archegonium matures there is a complete dissolution of the canal cells, so that a passage is established. Biflagellate antherozoids enter into the venter, one of which eventually fertilizes the egg. The fertilize egg is than surrounded by a thin cellulose wall and becomes an oospre or zygote. With fertilization and formation of the oospore, the sporophytic or diploid generation begins.