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 next division is also vertical but it is at right angle to the first. The distal tier of four cells of the octant stage functions as an apical cell with 2 cutting faces.
The thallus is branched and has a dorsal median groove and ventral median ridge. It is made of somewhat vertical rows of un-branched photosynthetic filaments. The venter consists of a single layered jacket. A single-layered sterile jacket encloses the mass of androcytes which metamorphoses into antherozoids.
The cells of inner layer of the venter wall the sporogonial wall along with some spore mother cells disorganize producing a viscous liquid. The outer cell divides transversely producing a row of four cells, The two lower cells of this row by further transverse and vertical divisions produce a short stalk of the antheridium.
These cells become softened and finally breakdown ,ife release mass of antherozoids. Rhizoids are numerous, cyxle, elongated, tubular and hair-like and are found as simple rhizoids or tuberculate rhizoids.
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Outer cell divides by transverse divisions to form a filament of 4 cells. Registration Forgot your password? Primary venter cell divides only once and forms a small venter canal cell and a large egg Fig. In hygrophilous species species which need a large supply of moisture for their growth the scales ricccia ephemeral i.
life cycle of riccia –
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 ventral surface of thallus bears many scales rlccia rhizoids.
This species can also grow on soil. The thallus of Riccia has a simple structure and is formed of parenchymatous cells which are bounded on both sides by the upper and lower epidermis.
Many antherozoids enter the archegonial neck because of the chemotactic response and reach up to egg. In this way the primary axial cell gets surrounded by six cells Fig. 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 crowded growth of the various rkccia is due to the repeated dichotomies of the thallus The thallus lobes arc flat growing horizontally on the soil and each lobe has a small not that the apex where the growing point is situated.
As all stated the mature spores are released by ccyle bursting of this wall after a long time when the tissue of the thallus has decayed.
The haploid number of chromosomes is 8 in species like Riccia arvensis, R. Rhizoids and scales serve as anchors for the plant. According to Pagansome of the spore mother cells in Riccia crystallina fail to produce spores and form abortive nutritive cells called nurse cells.
In Riccia fluitans, the only aquatic species, thallus is long, narrow, ribbon-like and dichotomously branched. The axial cell cuts of a small cover cell at the tip. In the upper two cells of the row two vertical divisions take place at right angle to each other producing a group of eight ceils or octants. Scales are arranged all along the margin in a single row.
Towards the end of the growing season the apices of the thallus lobes get thickened and form the perennating tubers. The archegonia, like the antheridia, are also embedded in the mid-dorsal furrow of the thallus and are arranged in acropetalous order i.
Some of the cells of the lower epidermis grow out and elongate forming the rhizoids, while certain cells divide and produce the single layered scales. It remains attached to the thallus by a short stalk. The male and female nuclei fuse together producing a single diploid nucleus.
The four nuclei migrate to the periphery of the spore mother cell and lie at equal distance from each other. They are haploid uninucleate and pyramidal in shape Fig. Spores are very small 0. The thallus is dorsiventrally differentiated. On being cyce, these branches develop into new thalli Fig. Rhizoids and scales are present on the ventral median ridge.
Germinal tube is filled with cytoplasm which contains albumin granules, chloroplasts and oil granules. Stalk attaches the antheridium to the base of the antheridial lief.
Riccia Ms. Inderveena Sharma H.O.D. Botany Department
It lacks foot and seta Fig. These plants are small and thallosethat is not differentiated into root, stem and leaf.
An 8-called stage thus results. These are capable to pass on the unfavorable conditions. This zone represents the ventral tissue of the thallus and lies below the photosynthetic zone. A deep cleft or furrow is commonly present in the middle of each lobe ticcia the dorsal side; the sex organs are found embedded in this furrow. Each air chamber is bounded by four epidermal cells e. Chinese Company introduces kf low price Chinese electric car in Pakistan. Mosses and liverworts of Britain and Ireland: To make this website work, we log user data and share it with processors.