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.
The basal swollen portion of the archegonium is known as the venter and the upper elongated portion as the neck. Simultaneously the nucleus also becomes crescent shaped, homogeneous and ultimately comes in contact with the blepharoplast. Antheridia and archegonia remain enclosed with in the antheridial and archegonial chambers and develop on the dorsal surface of the thallus Fig.
Primary neck canal cell divides by a series of transverse divisions to form four neck canal cells. The lobes are thicker in the middle and gradually become thinner towards the margins.
life cycle of riccia –
A mature archegonium is a flask shaped structure. Asexual reproduction occurs by sporesby fragmentation of the rosettes, and by formation of apical tubers. Download ppt “Riccia Ms. Upper two cells of the 4 celled filament are known as primary antheridial cells and lower two cells are known as primary stalk cells Fig. Scales are violet coloured, multicellular and one celled thick structures Fig.
In Riccia cruciata lifee two dichotomy result in a cruciate form Fig. Both these cells divide by two vertical divisions at right angle to one another and form two tiers of four cells each.
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He considered these cells as the fore-runnes of elaters found in higher forms of Marchantiales. Riccia plants may be monoecious or dioecious depending upon the species. In India a in polyploid species gaugetica Udar and Chopra reported 24 n and 48 In chromosomes number. The act of fertilization also stimulates the division of the wall of the venter. Cycoe this way the primary axial cell lifr surrounded by six cells Fig.
Each of the three peripheral initials divides by an anticlinal vertical division forming two cells.
These plants are small and thallosethat is not differentiated into root, stem and leaf. Several rivcia may enter a single archegonium but only one of them fuses with the egg for fertilization. Many antherozoids enter the archegonial neck because of the chemotactic response and reach up to egg.
Riccia Ms. Inderveena Sharma H.O.D. Botany Department
The canal of the neck contains a row of four neck canal cells and is closed at the tip by four lid cells. These cells contain chloroplast and are capable of developing into new thallus. One of the antherozoids penetrates the egg and fertilization is effected Fig. In the apical region they project forward and. Primary venter cell divides only once and forms a small venter canal cell and a large egg Fig.
Vegetative reproduction in Riccia is quite common and takes place by the following methods: The lower group of Peripheral cells by further anticlinal divisions produces a single layered wall of the venter.
It divides anticlinally and periclinally to form a two-layered calyptra along the developing sporophyte. The entire archegonium develops from the outer cell.
Riccia – Wikipedia
According to Campbell the exosporium and mesosporium rupture at the triradiate mark and the endosporium comes out in the form of a tubular outgrowth called the germinal Fig.
It remains attached to the thallus by a short stalk. The haploid number of chromosomes is 8 in species like Riccia arvensis, R. 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. As ricciw development of the antheridia is going on cyce surrounding vegetative tissue grows up and the antheridia become embedded in the dorsal furrow.
Ricciaceae Marchantiales genera Bryophyte stubs. Sexual reproduction in Riccia is oogamous. The thallus in Riccia is dichotomously branched and the growing point is ricia in its apical notch. The venter goes on increasing in size along with the developing sporogonium, and in this way the mature sporogoniurn remains enclosed in the double layered wall of venter.
The male and female nuclei fuse together producing a single diploid nucleus. The neck canal initials produce a row of four neck canal cells.
In certain species few sport mother cells do not produce spores but disorganise producing a mucilaginous fluid, The original wall of the sporogonium disorganises producing a mucilaginous fluid before the maturation of spores. Nucleus of each spore mother cell divides by two successive divisions to form 4 haploid nuclei. It cuts a number of cells on its left and right side to form the multicellular thallus Fig. The basal cell divides further producing the basal part of the antheridial stalk which remains embedded in the thallus tissue.
Fertilization ends the gametophytic phase. The wall of the venter is also formed of a single layer of cells which are arranged in several vertical rows.
Under favourable conditions it develops into a new thallus. Each branch of the thallus is linear, wedge-shaped or obcordate. Rhizoids are nearly lacking in aquatic forms, but there are usually numerous unicellular rhizoids of two types on the ventral surface.
The lower storage region is a continuation of the upper assimilatory region and is parenchymatous. Then the periclinal divisions take place in.
Primary androgonial cells divide be several repeated transverse and vertical divisions resulting in the formation of large number of small cubical androgonial cells Fig. The sporophyte of Riccia is the simplest amongst bryophytes. The union of these gametes or fertilization results in the production of an oospore which is diploid.