Riccia is a genus of liverworts in the order Marchantiales. These plants are small and thallose, that is not differentiated into root, stem and leaf. Depending on. Riccia is a thallose liverwort in which the vegetative plant, which is a gametophyte, generally forms rosettes due to the crowded growth of the thallus lobes this. Riccia description with images for under graduate students. the gametophytic phase of the life cycle ends with the formation of zygote.
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In this way the primary axial cell gets surrounded by six cells Fig. A wall is then secreted around the oospore.
The mature sporogonia are embedded in the tissue of the thallus and are visible to the naked eye as small black dots on the thallus. When the pife are produced the original walls of the androcytes become gelatinous thus producing a mucilaginous mass in which the antherozoids float freely.
Life cycle of riccia
When this process of disintegration or decay reaches up to the place of dichotomy, the lobes of the thallus get separated.
The spores germination give rise to the gametophyte. Sex organs develop in acropetal succession i.
Many lkfe develop later on from the multicellular thallus and fix it on the soil Fig. The sporophyte of Riccia is the simplest amongst bryophytes. Plants are usually monoicousand sexual reproduction is by antheridia and archegonia.
It divides anticlinally and periclinally to form a two-layered calyptra along the developing sporophyte. There is no particular time for the development of sex organs, and therefore one can see all the developmental stages in the different sections of the same thallus.
The lower ventral surface has a mid-ventral ridge bearing multicellular scales that originate as a single row but normally separate into two rows as the thallus widens. The adventitious branches develop from the ventral surface of the thallus in species like Riccia fluitans.
Riccia Ms. Inderveena Sharma H.O.D. Botany Department – ppt video online download
Scales are violet coloured, multicellular and one celled thick structures Fig. The haploid number of chromosomes is 8 in species like Riccia arvensis, R.
The plant body of Riccia is gametophytic and gametophytes are fleshy, prostrate and dichotomously branched. The basal cell divides further producing the basal part of the antheridial stalk which remains embedded in the thallus tissue.
The last division in each androgonial cell is diagonal thus producing two androcytes ricciaa mother cells. It completes within a few minutes.
Jacket initials divide by several anticlinal divisions to form a single layer of and theridial ccyle. It lacks foot and seta Fig. This zone riccua the ventral tissue of the thallus and lies below the photosynthetic zone. The canal of cycl neck contains a row of four neck canal cells and is closed at the tip by four lid cells. The spores are released by the bursting of the wall of the enlarged venter which is comparable to the calyptra of other liverworts The release of spores is delayed for a long time till the decay Of the vegetative tissue which may take even a year or so after the maturation of spores.
Twelve to twenty cells in perimeter enclose a small venter canal cell and large egg. These plants are small and thallosethat is not differentiated into root, stem and leaf. Botany Department”— Presentation transcript: The nucleus of each spore mother cell undergoes meiosis reduction division producing four haploid nuclei, and each spore mother cell then divides into four uninucleate irccia, each of which is transformed into a single haploid spore.
The axial cell cuts of a small cover cell at the tip.
Here’s how it works: Two large flagella develop from the conspicuously thickened end of the blepharoplast. At maturity the contents of each androcyte are transformed into a typical coiled biflagellate antherozoid. Chapter ruccia Reading Quiz About how many species of plants inhabit earth today? About project SlidePlayer Terms of Service. Gives structural support less affected by gravity.
Several antherozoids may enter a single archegonium but cycoe one of them fuses with the egg for fertilization.
Life Cycle of Riccia (With Diagram) | Hepaticopsida
The thallus is branched and has a dorsal median groove and ventral median ridge. The wall of each mature spore is very unevenly thickened and it consists Of three layers, the outer exosporium which is thin, hard and cutinised; the middle mesosporium which is very thick and soft; and the inner endosporium which is membranous.
There are no elaters. The thallus is dorsiventrally differentiated. This represents octant stage Fig. Photosynthetic filaments are separated from each other by narrow longitudinal vertical canals called air chambers. This article is about the plant Riccia.
Fertilization takes place in the presence of water the antherozoids liberated in the surrounding water swim towards the archegonia, being attracted chemotactically by the mucilage coming out of the archegonia. Its upper dorsal surface is green and chlorophyll -bearing, with a mid-dorsal longitudinal sulcus furrow or groove.
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Riccia Structure, Life Cycle, Sexual and Asexual Reproduction
The venter goes on increasing lofe size along with the developing sporogonium, and in this way the mature sporogoniurn remains enclosed in the double layered wall of venter. The fusion of the nuclei of male and female gamete results in the formation of diploid zygote or oospore.
In the mature archegonium the venter canal cell and neck canal cells disintegrate and form a mucilaginous mass.
Each air chamber is bounded by four epidermal cells e. After meiosis the mass of spores lies free in the outer layer of calyptra and mature sporogonium has no diploid structure.