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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Spores are not immediately dispersed in Riccia.
A vertical cross section of fo thallus shows two distinct zones, viz. Chapter 29 Reading Quiz About how many species of plants inhabit earth today?
Riccia Ms. Inderveena Sharma H.O.D. Botany Department – ppt video online download
The cell walls form the semifluid content of the antheridium during the metamoiphosis. A small part of the cytoplasm, which is not utilised in the formation of flagella may remain attached to the posterior end of antherozoid as a small vesicle. After meiosis the mass of spores lies free in the outer layer of calyptra and mature sporogonium has no diploid structure. At maturity the contents of each androcyte are transformed into a typical coiled biflagellate antherozoid. As all stated the mature spores are released by the bursting of this wall after a long time when the tissue of the thallus has decayed.
The ventral surface of thallus bears many scales and rhizoids. Some cells of the lower epidermis extend to form the scales and both types of rhizoids. Water helps in the dehiscence of the anheridium. Primary neck canal cell divides by a series of transverse divisions to form four neck canal cells. It remains attached to the thallus by a short stalk. Scales are arranged in a transverse row and may be membranous, multicellular, single celled, and with colours ranging from pink, red, violet and black.
The haploid number of chromosomes is 8 in species like Riccia arvensis, R.
The contents of each androcyte are transformed into an antherozoid. Both the androcytes remain enclosed in the wall of the androcyte mother cell with one separate wall Fig. On being detained, these branches develop into new thalli Fig. It absorbs water, swells up and comes out of the archegonial mouth by pushing the cover cells apart.
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Plants are usually monoicousand sexual reproduction is by antheridia and archegonia. Each androcyte thus metamorphosis into an antherozoid Fig. The second division is at right angle to the first and results in the formation of four cells. The primary cover cell divides by two vertical divisions at right angle to one another forming four cover cells which form the mouth of the archegonium.
The thallus is branched and has a dorsal median groove and ventral median ridge.
Life cycle of riccia
The basal cell divides further producing the basal part of the antheridial stalk which remains embedded in live thallus tissue. The main function of the mid-dorsal groove is to retain water required for fertilization. Apical cells of the antheridial wall get swollen by absorbing water. Basal cell remains embedded in the tissue of thallus, undergoes only a little further development and forms the embedded portion of the antheridial stalk.
If you wish to download it, please recommend it to your friends in any social system. Both these cells divide by two vertical divisions at right angle to one another and form two tiers of four cells each.
It is called octant stage Fig. The last division in each androgonial cell is diagonal thus producing two androcytes antherozoid mother cells. The next division is also vertical but it is at right angle to the first.
In Riccia crystallina the scales are inconspicuous and absent. It is a few cells away from the apical cell. It enters the antheridial chamber. It is the most common method of vegetative reproduction in Riccia. The of the mature capsule consists of a single layer of cells surrounding a mass of spore mother cells. Antheridial chamber, in which an antheridium lies, communicates with the clorsal surface of the thallus by terminal opening. The student’s handbook of British hepatics, p. Depending on species, the thallus may be strap-shaped and about 0.
It is more a method of perennation rather than multiplication. The adventitious branches liff from the ventral riccka of the thallus in species like Riccia fluitans. It lies near the periphery of the protoplast Fig. Riccia belongs to the family Ricciaceae of the order Marchantiales.
He considered these cells as the fore-runnes of elaters found in higher forms of Marchantiales. Sexual reproduction in Riccia is oogamous.
Riccia is a genus of liverworts in the order Marchantiales. In Riccia cruciata only two dichotomy result in a cruciate form Fig.
It again divides by a transverse division which is parallel to first division. In smooth-walled rhizoids both the inner and outer wall layers are fully stretched while in tuberculated rhizoids the inner wall layer modifies into peg-like or plate-like in growth which projects into the cell lumen Fig.
There are no elaters.