Today we will discuss about the world of Bryophyta
Definition of Bryophyta
A division of nonflowering plants characterized by rhizoids rather than true roots and having little or no organized vascular tissue and showing alternation of generations between gamete-bearing forms and spore-bearing forms; comprises true mosses (Bryopsida) and liverworts (Hepaticopsida) and hornworts (Anthoceropsida)
- Autophytic nutrition.
- Aphibians among the Plant Kingdom because it needs water during the reproduction
- Thallus body
- Reserve food material is starch
- Cell wall- cellulose
- Sporophyte depends upon the gametophyte
- Adult life starts with gametophyte
- Chemotropism- occurs by synthesis of sucrose
- Vascular tissue is absent
- Eg. Any kind of moss
Q and A on Bryophyta
- What are the main characters of Bryophyta? (3)
Ans. The main characters of Bryophyta:
a) Bryophyta is a kind of non-flowering, autophytic independent plant.
b) The gametophytic plant body of the lower Bryophytes are not differentiated into root, stem and leaves, Eg.- Riccia. They are thallus like.
c) Conducting tissue systems (xylem and phloem) are absent. It does not possess true roots, instead of that unicellular or multicellular rhizoids are present.
d) The bryophytes reproduce asexually by means of spores.
e) The male sex organ is known as the antheridium (pear shaped) and the female sex organ (flask shaped) is called the archegonium.
f) The sporophytic plant is always attached with the gametophytic plant, and is fully dependent upon the gametophytic plant for growth and nutrition.
- What is tympanum? What is its function? (2)
Ans. Tympanum is a thin, membranous covering below the operculum, also called epiphragm.
Function: It covers the archesporial sac from the upper side.3. How many peristome teeth are present in Pogonatum? (2)
Ans. There are 32 membranous peristome teeth, which are partially hygroscopic and are arranged in two layers.
- Name the structures that protect the capsule of moss. (2 )
Ans. Calyptra, operculum, tympanum and peristome are the structures that protect the capsule of moss.
- What is calyptra? (2)
Ans. The gametophytic tissue covering the venter of archegonium, which persists after fertilization and remains as the outer covering of the moss capsule.
- Name two Indian species of Riccia and two Indian species of Pogonatum. (2+2)
a) Riccia discolor and Riccia gangetica
b) Pogonatum microstomum and Pogonatum aloides
- What is rhizoid? And state its function. (2)
Ans. The rhizoids are long thick walled, multicellular or unicellular structures with oblique septa, may be twisted together to form a rope like structure or may be coiled into an entangled mass.
Function: The rhizoids help in anchorage and also in absorption of water. It may help in vegetative propagation.
- What is operculum? (2)
Ans. It is the apical cap-like structure in the form of a beak in the capsule of Pogonatum. They are attached to the distal end of theca by a ring-like diaphragm. The upper cap-like structure below the calyptra is called operculum.
- What is the function of nurse cell? (2)
Ans. The sterile spore mother cells within the Riccia capsule form the nurse cells, which provide nourishment to the developing spores.
- Write the differences between rhizoid and scale. (3)
3. Two types- Smooth walled and pegged.
4. Occurs in mid ventral region on the ventral side of the thallus.
5. Function: Fixation of thallus to the substratum and to absorb water and solutes from the soil.
2. Coloured- pink, red, violet or black
3. No types.
4. Occurs along the two margins on the ventral side of the thallus.
5. Function: Protection of the growing point and to increase the absorptive surface.
- What are the functions of paraphyses and perichaetial leaves? (1+1)
Paraphyses leaves: The multicellular sterile branches separating the sex organs of moss, which hold moisture and prevent drying of sex organs.
Perichaetial leaves: The perichaetial leaves are sterile leaves, which surround the sex organs from outside and prevent them from drying.12. How spore dispersal occurs in Riccia? (3)
Ans. There is no spore dispersal mechanism noted in Riccia, the matured spores are retained within the capsule, after the decay of the gametophytic tissue, the capsule bursts and the spores are liberated outside.
- What is oosphere? (2)
Ans. The spherical, non-motile haploid female gamete in bryophytes is called oosphere, which is fertilized by the biflagellate antherozoid, to form the diploid oospore.
14. What are liverworts? (2)
Bryophytes belonging to class Hepaticeae called liverworts because they resemble liver of higher animals.
15. What is chloronema? (2)
Ans. The chlorophyllous protonema is called chloronema, which develops to form the moss gametophyte.
16. Describe the alternation of generation of Bryophyhta
Alternation of gneration:
Sporogenic Meiosis Growth
Diploid generation (2n) Haploid generation (2n)
Growth Mitosis (n)
Zygote (2n) Fertilization Gametes
In the life history of certain plants the sporophytic generation with diploid set of chromosomes and gametophytic generation with haploid set of chromosome are found to alternate with one another. This phenomenon is called alternation of generation eg. Moss, fern etc.
Role of mitosis and meiosis: In this process the gametophytes remains in haploid condition, this plant produces the haploid male and female gametes. Hence the gametes are produced here through mitosis.
The haploid gametes unite to form the diploid zygote, which gives rise to diploid sporophyte. The diploid spore mother cell present in this sporangia of this sporophyte divide through meiosis to form spores, which germinate to gametophyte hence the sporophytic and gametophytic generations are brought about by the influence of mitosis and meiosis respectively.
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