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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The neck canal initials produce a row of four neck canal cells.
Riccia Ms. Inderveena Sharma H.O.D. Botany Department – ppt video online download
Fertilization ends the gametophytic phase. Antheridium is present singly in an antheridial chamber. The apical growth of the thallus continues and the mature archegonia come to lie near the hinder portion.
About project SlidePlayer Terms of Service. 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 cyxle which projects into the cell lumen Fig.
Riccia Structure, Life Cycle, Sexual and Asexual Reproduction
The thallus is branched and has a dorsal median groove and ventral median ridge. Views Read Edit View history. This cycls initial divides by a transverse division into an upper primary cell and a lower primary stalk cell.
Towards the end of the growing season the apices of the thallus lobes get thickened and form the perennating tubers. Sometimes all the developmental stages can be traced in the single thallus due to the production of archegonia in an acropetalous succession, antheridia and archegonia respectively.
Each archegonium is a flask-shaped structure having a multi-cellular stalk. For the completion of the whole life cycle the gametophyte produces the sporophyte, this sporophyte produces the gametophyte again, and these two generation regularly alternate with each other. Internally the thallus is differentiated into two regions, upper assimilatory region and the lower storage region.
Each androcyte thus metamorphosis into an antherozoid Fig. Basal cell remains embedded in the tissue of thallus, undergoes only a little further development and forms the embedded portion of the antheridial stalk.
Then the periclinal divisions take place in. The wall of the neck consists of a single layer of cells which are arranged in six vertical rows. Simultaneously the primary axial small cell divides transversely and unequally to form small upper primary cover cell and large lower central cell Fig.
Life cycle of riccia
These phases alternate with each other. The androcyte soon looses its triangular shape and becomes somewhat round or oval Fig. The haploid number of chromosomes is 8 in species like Riccia arvensis, R.
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. This mucilaginous mass consists lfe chemical substances such as soluble proteins and certain inorganic salts of potassium. Plants Land plants retain derived features they share with green algae: Spores are very small 0.
These are capable to pass on the unfavorable conditions. A deep cleft or furrow is commonly present in the middle of each lobe on the dorsal side; the sex organs are found embedded in this furrow.
The cells of the amphithecium divide only by anticlinal division to form a single-layered sterile jacket or capsule irccia. A single-layered sterile jacket encloses the mass of androcytes which metamorphoses into antherozoids. A bilayered calyptra forms a protective covering around the capsule. One of the antherozoids penetrates the egg and fertilization is effected Fig.
Primary antheridial cells divide by two successive vertical divisions at right angle to each other to form two tiers of four cells ricdia Fig. If you wish to download it, please recommend it to your friends in any social system.
Rhizoids are unicellular ticcia un-branched. The four spores produced from each spore mother cell remain held together in tetrads for a long time.