BRYOLOGY
BRYOLOGY & BRYOPHYTE STUDY
BRYOLOGY(STUDY ABOUT MOSSES & LIVERWORTS
IN GENERAL
Bryophytes INTRODUCTION
Bryophytes classification
Bryophytes Habitat
Bryophyte Morphology
Bryophyte Anatomy
Bryophyte reproduction
Bryophytes life cycle.
Bryophyte special character
BRYOPHYTE INTRODUCTION
Bryophytes are the Amphibians of the plant kingdom as they live on soil but depends over water for sexual reproduction.
Traditionally plant kingdom is divided into two kingdom
Cryptogams (non flowering plants)
Include Thallophyta, Bryophyta, Pteridophyta
Phanerogams (flowering plants)
- Also known as spermatophytes
- Include Gymnosperm, Angiosperm
Kingdom – Plantae
Division - Bryophyte
Father of biology - ARISTOTLE
Study of Bryophytes- Bryology
Term bryophyte was given by – Robert Broun
Father of bryology – JOHANN HEDWIG (1730-1799)
Father of Indian Bryology- Prof S.R Kashyap
1.1 JOHANN HEDWIG
German Botanist Hedwig is notable for his studies of Mosses for which he is sometimes called the father of Bryology. In particular the observation of sexual reproduction in the cryptogams.
ACHIEVEMENTS
He dealt with the Anatomy, fertilization, and reproduction in the mosses and provided a new basis of classification based on the distribution of spores. Hedwig was the first to recognize the true organs of reproduction in Mosses and also he demonstrated the close relations between mosses and liverworts
Hedwig greatest achievement is the discovery of the antheridia and archegonia of the leafy moss, which he correctly interpreted as reproductive organs, which was disputed in 1818 by the famous botanist Christian-Konrad-Sprengel.
Bryophyte Habitat
Bryophytes mainly grow in moist, humid and shady places( places out of sunlight). But in the least they found in a variety of habitats, maybe at differing temperature( hot desert to chilling glaciers), elevations,(seawater ecotone to Alpine tundra) and moistures(dry Desert to tropical rain forest).
BRYOPHYTES CLASSIFICATION
The roughly 18,000 species of bryophytes are generally classified into three coordinates phyla, Anthocerophyta(hornworts), Bryophyta(mosses), and Marchantiophyta(liverworts).
The basis of classification is plant body organization.
BRYOPHYTES MORPHOLOGY
They are a small group of plants which have independent multicellular gametophytic plant body as a dominant phase.
They are generally smaller in height, with no true root, stem or leaf. They contain root-like, stem-like and leaf-like structures, therefore, the body is called the thalloid or thallus like.
They remain attached to the surface through unicellular (liverworts) or multicellular (mosses) root-like structure called rhizoids.
They are nonvascular plants or they do not possess vascularization for the conduction of water and minerals, this also necessitates them to live in the dump condition, one favor bryophyte get of this condition is that they can grow over the hard surface over the rocks and these criteria make the organism of the pioneer community.
As similar to another group of the plant kingdom, Bryophyte is also divided into gametophytic and saprophytic phase.
Gametophytic part of the plant consists of Rhizoids, main axis, and leaf, whereas the saprophytic part of the plant composed of the foot, seta, and capsule.
Rhizoids provide anchorage to the plant and also take part in vegetative reproduction.
Main axis holds the leaf-like structures, which are of different types in a variety of plants.
The leaf-like structure contains the chloroplast for photosynthesis. In liverworts, lives are undifferentiated while the leaves of Mosses are single-celled attached to a stem where it is used for water and nutrient transport.
In sporophyte- foot germinate from the archegonium as a result of fertilization which holds the sporophytic generation over the gametophyte and work as a link for supporting the photosynthesized food (at the main axis of the gametophyte ) to be transported to the sporophytic part.
Seta works as similar to the stalk and works as a connecting link between foot and capsule.
The capsule is the anterior portion of the sporophyte, which provides a favorable condition for meiosis, whose result is spores inside spore-sac.
TRANSPORTATION IN BRYOPHYTE
The green tissue that makes up most of the plant body is not vascularised; it does not have xylem and phloem cells. The absence of specialized tissue for transporting water and dissolved food throughout the organism limit the organism to a very small size. The only process left for the transport of materials throughout the body is osmosis and diffusion.
The process diffusion is not much helpful for higher plants because it is as slow as 50 micrometers in about 2.5 seconds. At this rate we can calculate that the molecule to travel 1 meter have to wait for 13 years, hence the small size of bryophyte provide them adaption over such qualities.
BRYOPHYTE REPRODUCTION
REPRODUCTIVE STRUCTURE-
The gametophyte produces gametes through mitosis and have multicellular sex organ. The male sex organ is called as Antheridium and the female sex organ is called as Archegonium.
Structure of male sex organ(Anthredium)- It is racket like surrounded by a sterile jacket. The jacket encloses the mass of sperm (mother cell) or androcytes. Which produce two biflagellate antherozoids.
Structure of female sex organ ( Archegonium)- It is flask-shaped with tubular neck and swollen venter. It is also surrounded by jacket cell which has a venter cavity. The ventor cavity has a venter canal cell and an egg cell. The jacket also surrounded the neck which contains 6-10 neck canal cell. BRYOLOGY(STUDY ABOUT MOSSES & LIVERWORTS)
Reproductive process- The antheridium releases biflagellate motile male gamete which reaches archegonium under the influence of sucrose and potassium ion. The male and female gamete fuse inside the archegonium and form zygote. The zygote does not undergo meiosis and instead develop through mitosis to form embryo hence are called as the first embryophyte. The embryo later develops into diploid sporophyte which derives it’ nutrition from photosynthetic gametophytic plant body hence they are not free living.
The sporophyte is called as sporogonium which consists of these parts that are foot, seta, and capsule. The capsule contains spore sac which produces Haploid spores through Meiosis( sporic meiosis). The spores come out of the capsule by the absorption of water and they disposed of out through air current, after falling over suitable ground the spores either develop into thalloid gametophyte e.g in liverworts or a filamentous stage called as protonema e.g in mosses.
Bryophyte is mainly Homosporous that is they produce only one type spores.
About 11 types of vegetative reproduction shown in bryophytes, these are:-
1 Death and decay(Hepaticopsida)
2 Adventitious branches
3 Formation of innovation
4 By cladia
5 Separation of the whole shoot
6 Separation of modifies branch of bud-like form
7 Tubers
8 Gemmae
- Hepaticopsida Gemmae
- Anthoceropsida Gemmae
- Bryopsida Gemmae
9 Protonema
10 Secondary protonema
11 From tuft of rhizoids
BRYOPHYTE LIFE CYCLE
As we have study earlier bryophytes have two generations, Dominant, Independent, Photosynthetic Gametophytic gametophytic generation, and dependent non-photosynthetic Sporophytic structure.
Gametophyte germinates over the moist soil surface from the spores which were dispersed through air and insects after landing mosses develop into a thread-like chain of cells from the germ tube, further it develops into a leafy gametophyte.
In liverworts spores directly develop into the leafy gametophyte.
over the gametophyte, Hedwig discovered Antheridia and Archegonia are found in which male and female gametes are produced respectively.
The biflagellated motile male gamete travels through the water under the influence of starch and potassium ion towards the female gametophyte and follows the fertilization which results into a diploid zygote which undergoes mitotic division result into an embryo, this is the first time embryo appeared in the life cycle of any plant species. This embryo develops into a sporophyte comprising the foot, seta, and capsule. Inside capsule beneath the spore sac, sporogenous tissue undergoes meiotic division as a result spore are formed which follow dispersion and landing over the suitable surface and later germination to protonema or gametophyte in the respective plant body.
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