Dr. Mohammad Khalid Masroor

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1 Dr. Mohammad Khalid Masroor
Associate Professor & Head Botany Department Bhavan’s Mehta Mahavidyalaya Bharwari, Kaushambi

2 An Introduction to Bryophytes Their classification and uses

3 Bryophyte is derived from a Greek words
Etymology Bryophyte is derived from a Greek words BRYON means mosses and PHYTA means plants

4 Introduction to Bryophytes
Bryophytes are essentially small plants. Depend on water for fertilization They are amphibians of plant kingdom. Are basically land plant. Occupy an intermediate position between algae and vascular cryptogams Are macroscopic plants. Bryophytes, pteridophytes and gymnosperm show archegonium. So called Archegoniatae. Cryptogams means lower plants (Bryophytes)

5 Features Similar with pteridophytes :
Multicellular sex organs, with an outer layer of sterile cells. Permanent retention of zygote within the archegonium. Retention of embryonic sporophyte within the archegonium. Dependence of saprophytes on the gametophyte

6 Features disimilar with Pteridophytes
The sporophyte of a bryophyte is not an independent plant. Sporophyte is not capable of unlimited growth. Conducting system in bryophytes is not differentiated into distinct xylem and phloem.

7 Distribution : World- wide in distribution.
Grow Luxuriantly in humid climate of temperate and tropical regions. Liverworts hepatics are rare is arctic environments. Mosses survive in extreme conditions of arctic and alpine regions. Mosses can tolerate submergence in water in semi-arid condition. Mosses can recover after years of dehydration. Mosses can withstand extended periods of freezing. Few mosses grow on the seashore.

8 Plant Body Plant body is gametophyte which is independent and autotrophic. Gametophyte is thallus, dorsiventral without differentiated into stem leaves and roots. Sporophyte is dependent on gametophyte for its nutrition and physical support. Sporophyte is differentiated into foot, seta and Capsule. Foot is within gametophyte for anchorage and absorption. Seta is an elongate, stalk-like structure meant to project the capsule. Capsule is spore-bearing structure called sporogonium.

9 Regeneration Remarkable regeneration capacity.
Dry and isolated fragments regenerate to form entire plant. For vegetative reproduction specialized structures gemmae are produced. A gemma is cluster of new cells which gives rise to new gametophyte. Cells of saprophyte are also capable of regeneration. Sporophyte regenerate to form a protonema on which appear gametophyte. The regeneration of a gametophyte from a sporophyte without the formation of spores is apospory. Gametophyte may form a mass of cells which regenerate in sporophyte. Regeneration of a sporophyte from a gametophyte, without the formation of gametes is apogamy. Apospory and apogamy are rare events in regeneration of bryophytes.

10 LIFE CYCLE-I Regular alternation between the two generations.
Gametophyte (gamete-producing generation) Sporophyte (spore-producing generation) Gametophyte is haploid and bears sex organs- antheriodia and archegonia and produces gametes, antherozoids and egg. Saprophyte is diploid, undergoes meiosis to form haploid spores. Heteromorphic alternation of generation. Independent and autotrophic gametophyte generation. Sporophyte is always dependent on gametophyte.

11 LIFE CYCLE- GRAPHIC

12 LIFE CYCLE-II The spore is the first or germ cell of the sporophyte generation. Protonema is an ephemeral structure in thalloid liverworts : which bear sex organs. Fertilization in presence of water. Zygote is the first-or germ cell of sporophyte generation Zygote divide to form embryo. Embryo forms spore bearing structure capsule. Capsule encloses archesporium, the fertile tissue. Capsule projects with seta-like structure and draws nutrition from haustorial cells of foot. Archesporial cell differentiate into spore-mother cell and elater-mother cell. Each spore mother cell undergoes reduction division to produce haploid spores. Elaters are present in liverworts and absent in mosses. Capsule of moss has specialised structure peristome for dispersal of spore. Peristome are unique structure of bryophytes.

13 Classification Bryophytes are recognised in two major groups.
Hepaticeae (liverworts). Musci (mosses) In recognition of anamalous character of hornwords, the group spread in three major group. Hepaticeae (liverworts) Anthocerotae (Anthocerotae) As per recommendations of I.C.B.N. these class names have been changed. Hepaticopsida (Hepaticeae, liverworts). Anthocerotopsida (Anthocerotae, Hornworts) Bryopsida (Musci, Mosses).

14 Hepaticopsida Liverworts are a large group of about 330 genera and 8000 species. Six evolutionary Lines represented by following orders. Marchantiales (Chambered-hepatics) Sphaerocarpales (Bottle-hepatics) Monocleales (Giant-thallose-hepatics) Metzgeriales (Multiform-thallose-hepatics) Jungermanniales (Scale moss hepatics) Calobryales (Moss0like hepatics) These orders are based on structure of the gametophyte. The Sporophytes are essentially similar. Cavers (1911) changed in number of orders of liverworts New genus are: Pachyglossa and phyllothallia (Herzog and Grolle, 1958). Enigmalla (Beckmann & Scott, 1992)

15 Anthocerotopsida It is evolutionary group of thalloid liverworts without an internal differentiation. Each cell having single large chlorophast with associated pyrenoid. The horn describes the sporophyts. Single order with one or two families. Anthocerolates Anthocerotaceae Notothylaceae Commonly recognised genera are Anthocerotaceae : Anthoceros Megaceros Dendroceros Phaeoceros Folioceros (Aspiromitus) Notothylaceae : Notothylas Members are distributed in temperate as well as tropical region. Megaceros is quite common on splashed rocks of water streams Dendroceros is common on tress trunks of humid forest.

16 Musci/Bryopsida Class Brypsida include mosses.
Classification is based on characters of gametophyte and sporophyte. Initially mosses have been classified into two groups. acropcarps (Sex organs and sporophyte on the main stem or branch) pleurocarps (Archegonia and sporophyte on lateral branches) Earlier taxonomists on the basis of structure and features of a moss sporophyte recognized three distinct evolutionary lines. Bryales Andreaeales Sphagnales The current trend have few more distinct evolutionary lines. Bryoles (Joint-toothed mosses) Archidiales (large-spored mosses) Tetraphidales (Four-toothed mosses) Polytrichales (hair-cap mosses) Buxbaumilaes (Bug-mosses) Sphagnales (Bog-or peat-mosses) Andreaeales (lantern-mosses) In mosses Bryales, largest order comprising 30 families. These mosses are known as joint- toothed mosses. This character separate from rest of mosses.

17 Evolution Have low evolutionary potential.
High degree of variability in liverwort, genera scapania and calypogeia. Adapt to extreme types of habitats except the marine. Genetic variations are seen due to : gene mutation changes in chromosome structure and number. genetic recombination. Natural selection operates due to reproductive isolation.

18 Evolution - Liverworts :
Cytologically uniform group. Formation of diploid spores and gemmae. Polyploids are at a selective advantage. Hybridization is known. Effectiveness in induced mutation Evidence of gene mutation resulting diffused growth. Genetic differences observed in Lophocolea heterophylla. Marchantia polymorpha is radiation tolerant form. Evidence of reproductive isolation.

19 Evolution - Mosses : Structural changes in chromosomes in mosses.
Evidence of genetic variation due to recombination & mutation. There are high frequency of haploid is Bartramiaceae, Mniaceae & Polytrichaceae. Most of the mosses are diploid. Recessive mutation found. Polyploidy is most important factor in evolution. 66% Primary polyploids, 19% secondary polypoloids. Monocious and "weedy" species fruit abundantly. Pottia, Funaria and Physcomitrium produce abundance of capsule. Family Amblystegiaceae have hydrophytic mosses.

20 ORIGIN (I) Simplest green land plants.
Considered to be monophyletic group. (Campbell, 1895, 1898; Cavers, 1911) Anthoceros and its allies are isolated group. Schuster, 1966; Chopra, 1967; Crum, 1976 questioned monophyletic origin. Liverworts and mosses have common ancestor. Hornworts are ancient pteriodophyte adapted a bryophytic life cycle. Polyphyletic origin is based on their familiarity with members of Hepaticeae. Four distinct lines recognised are: Hepaticopsida Anthocerotopsida Bryopsida Sphagnopsida. There groups are classified on basis of cytology and chemical nature. Bioflavonoids isolated in cell walls of mosses. Chloroplast. coded 165 and 235-r RNA genes from a number of bryophytes- mosses, liverworts and hornworts. and algae is indicative of polyphyletic origin.

21 Pteridophytic-Origin of Bryophytes (II)
Kashyap and Dutt, 1925 postulated pteridophytic ancestry. There is link between Horneophyton and Anthoceros. Dorsiventral gametophyte originating from erectradially symmetrical isophyllous prototype Bryophytes - Psilophytes (Haskell, 1949; Christen son 1954) Originated from unknown Pteridophyte which were simplest like Rhynia and Horneophyton. These plant lacked roots as well as leaves. Presence of tracheid-like elements with spiral thickenings in columella of Anthoceros Prosakuer 1960) Lignin is chemical constituent of tracheid but present in mosses gametophyte of Dawsonia (Siegel, 1962) There were two main evolutionary trends: Elaboration of sporophyte Simplication of gametophyte. This lead to the formation of vascular plant. Second trend: Maintenance of gametophyte Simplication of sporophyte.

22 ALGAL- ORIGIN OF BRYOPHYTES (III)
Bryophytes share with green alage- Photosynthetic pigments, Cell wall components Food reserves Flagella Lipid metabolism is intermediate between algae and higher plant. View supported by chopra, 1967, Fott, but questioned by Steere, 1969; Crum, 1976; Smith, 1978). Similarities predicts common ancestor. Similarity of filamentous protonema.

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28 Hepaticopsida (Liverworts) Anthocerotopsida (Hornworts)
Bryopsida (Mosses) Hepaticopsida (Liverworts) Anthocerotopsida (Hornworts)

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34 Bryopsida

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36 Hepaticopsida

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38 Anthocerotopsida

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73 FOSSIL HISTORY Fossil evidence is supportive of a long history.
Authentic fossil records of liverworts in upper Devonian and mosses in Carboniferous. Fossil lacking necessary details have been described as "fossil moss" or fossil liverwort." Muscites Hepaticites. Hepaticites willsii (walton 1925, 1928). first fossil record from carboniferous. Hepaticites kidstoni is thalloid livertwort. Treubites kidstoni (schuster & scott, 1969) Earliest Hepaticites devonicus (Henber, 1961) from upper Devonian. Most interesting and enigmatic fossil bryophyte is Naiadita (Harris 1938, 1961). Mesozoic). Well preserved fossil mosses (Neuberg, 1956, 1958, 1960) are described from Peruvian beds (USSR) "Eubryales Incertae sedis" Fossil Intia is similar to Mnium and Bryum. Fossil leaf genus Protosphagnum is similar to Sphagnum. Fossil records of Naiadita and Protosphagnum do point out that pryophytes of the past were quite unlike that of today.

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