Structural variations in reproductive structures of division Bryophyta
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Structural variations in reproductive structures of division Bryophyta

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Structural variations in reproductive structures of division Bryophyta Structural variations in reproductive structures of division Bryophyta Presentation Transcript

  • Group Assignment Structural Variations In Reproductive Structures Of Division Bryophyta (Mosses )
  •  
  • Class Sphagnidae Class Andreaeidae Class Bryidae
    • One of the main three divisions of Bryophytes
    • Bryophytes contain……
          • Division Hepatophyta : Liverworts
          • Division Anthocerophyta: Hornworts
          • Division Bryophyta : Mosses
    • Consists of three classes
    • Class Sphagnidae (Peat Mosses)
    • Class Andreaeidae (Granite Mosses)
    • Class Bryidae (True Mosses)
    • Peat mosses & Granite mosses diverged earlier
    • from the main line of moss evolution. Class Bryidae is the most diverse & large group of all mosses
    Commonly known as “mosses ”
  • Some Granite mosses…..
  • P e a t M o s s e s
  • Hair cap mosses Here are some true mosses…
    • Possesses a gametophyte & sporophyte in life cycle.
    • Dominant phase - gametophyte.
    • Matrotrophic sporophyte , born on gametophyte
    • Leaf like structures ( leafy) Leaves
    • Leptoids Phloem
    • Hydroids Xylem
    • No lignified cells
    • No cuticles
  • Class: Sphagnidae Eg: Sphagnum Class:Andreaidae Eg : Andreaea
    • Bryidae – The true mosses
        • Eg : Pogonatum
    • Very sensitive to air pollution
    • Can survive in dry conditions
    • Some appear in brown color
  • Reproduction Asexual Sexual Fragmentation
    • Production of antheridia & archegonia in gametophyte
    • 2 ) Production of sporangia in sporophyte
    Producing brood bodies Production of Gemmae
  • Variations in Asexual Reproduction Structures of Division Bryophyta (Mosses)
    • Fragmentation is the commonest method……
    Thus, small fragments or pieces of tissue produce an entire gametophyte Young branches Stem pieces Injured leaves From gametophyte Regenerate into a new gametophyte Cluster of newly produced gametophytes Clumps
  •  
  • Campylopus clavatus, a tufted moss
    • A small apical section of each stem is weakly joined to the rest of the stem.
    • This apical section will break off easily.
    • For example if an animal walks across the moss colony or raindrops hit the colony with sufficient force.
    • Typically a colony of  Campylopus clavatus  with numerous loose apical fragments lying on top of the colony .
    • Each fragment consists of a very short stem section, with attached leaves.
    • Nodding thread moss, Pohlia nutans
    • Has catkin-like branches which are readily detached from the parent plant
  • Leaf Fragment Rhizoids are growing from the lower surface and a new shoot is forming on the upper surface of this detached leaf fragment. 
      • fragments can produce protonemata which will ‘bud’ and develop into gametophyte mosses.
    Moss fragments can produce protonemata which will ‘bud’ and develop into gametophyte mosses.
  • Production of Brood Bodies
    • Specialized vegetative reproductive structure
    • on gametophytes.
    • May be in the form of
            • Tubers(plantlets)
            • filaments
            • clusters of green cells
            • small leaves of leafy shoots that are produced in the leaves or stems.
    • When these are detached they grow into another adult plant. 
    • Achrophyllum dentatum  - The rough appearance of the leaves is due to the presence of brood bodies on the leaf margins.
  • Achrophyllum dentatum,  sectional view - Brood bodies consist of short filaments that project above the leaf surface; these break off and form new plants. 
  • Philonotis tenuis,  detached brood body - The brood body of this moss is more complex. It consists of a small shoot with leaves. These are formed close to the stem tip and are easily broken off when touched. 
  • Bryum sauteri  - Brood bodies in some mosses are formed as small tubers on rhizoids. Each is capable of giving rise to a new plant when detached. 
  • Production of Gemmae
    • Tiny, easily dispersed propagules that will germinate to produce new gametophytes.
    •   May be just a single cell or a simple aggregation of cells, rather than a well-structured feature such as a leaf or a branch tip.
    • Rather, the gemmae grow off stems, leaves or thallose surfaces and sometimes are visible only under a microscope 
  • Calymperes dozyanum  leaf gemma
    • The brown, multi-celled gemma is about a tenth of a millimeter long and is attached to the apex of the leaf.
    • In this species such leaf gemmae grow in clusters at the apices of some of the leaves.
    •   A blurry, brown "cap" with a honeycomb-like appearance on the leaf apex.
    •   Initially a gemma was attached at each of those honeycomb cells.
    • Such leaf gemmae are easily broken off and dispersed from the leaf and each is capable of growing into a new plant.
  • Sexual Reproduction of Division Bryophyta
  •  
    • Antheridia.
    • born on a specific structure called antheridial head
    • Spherical or elongated in shape
    • Commonly stalked
    • It consists sterile jacket layer, one cell thick, surrounds numerous spermatogenous cells
    • Jacket layer is sterile
    • Each spermatogenous cell forms a single biflagellated sperm
    • It swims through the water to reach the egg
    Single jacket layer spermatogenous tissue stalk
    • Antheridia occur in the axils of the leaves
    • Typically flask shaped
    • With a long neck & swollen basal portion, the venter
    • Venter encloses a single egg
    • Sterile protective layer(jacket layer) = outer layer of cells of the neck + Venter
    • Contains only a single egg
    • Prior the fertilization neck canal cells are disintegrated facilitating the sperms to reach the egg.
    • Archegonia are on stalks
    • Clustered at the tip of the stem
    • Variations of
    • Reproductive Structures
    • Of
    • Division Bryophyta
  • Variations In Gametangia of Division Bryophyta
  • Let’s have a class wise look…………………….. Class : Sphagnidae
    • Antheridia & archegonia are born at the ends of special branches located at the tips of the moss gametophyte .( Pleurocarpous )
    Eg: Sphagnum
    • Gametangia are associated with leaves along the shoot. 
    • Antheridia are equally elongated with a long narrow stalk and banana-shaped antheridial body
    Antheridia
    • The sterile jacket is one  layered
    • The neck encircles a tube which leads to the cavity (venter) containing the female gamete.   
    Archegonia stalked globose antheridia borne at the tips of branches usually with swollen colored tips of branches near capitulum; long-necked archegonia borne on short branches singly surrounded by perichaetial leaves that are typically longer than branch leaves.
  • Class Andreaeidae Eg: Andreaea Archegonia
    • Typically flask shaped.
    • long neck is filled with neck canal cells.
    • Mature archegonium contains one egg.
    Antheridia
    • Elongated antheridia
    • Have comparatively a long stalk
    • Antheridia are covered with sterile structures for protection
    • Produce number of biflagellate sperms.
  • Class:Bryidae Eg: Pogonatum Antheridia Gametangia are produced by mature leafy gametophytes, either at the tips of the main axis or on a lateral branch.
    • Relatively small
    • Often clustered within leafy structures called splash cups
    • forms a structure called perigonium together with sterile structures.
    In the perigonium, cigar-shaped antheridia mixed with perigonial bracts and other sterile structures.
  • l.s of a perigonium Perigonial bract Cigar shaped antheridium Paraphyses This is the tip of an antheridium. The swollen cells at the apex swell and separate when the sperms cells are mature and the antheridia are wetted. swollen cells at the apex
  • Antheridia of Pogonatum Antheridial heads
    • Splash cups
    • Typically , flower shaped structures which facilitates fertilization of gametes as well as protection of antheridia
  • In many mosses the leaves around the male stem tip that encircle the antheridia form a 'splash cup'. Sperm are released into rainwater or condensation that collects within the cup and are then splashed out when rain drops strike the water. In this way the sperm are carried to the archegonia on nearby plants .   Bryum billardierei  - A male stem tip with a splash cup containing numerous antheridia 
    • Broad leaves (pale green) encircle a group of smaller, sausage-shaped antheridia (deep green) at the tip of a male stem.
    • Each antheridium produces numerous biflagellate sperm cells .
    Calyptrochaeta brownii
  • Orthotrichum pusillum produces clusters of antheridia
  • Visible antheridia of Polytrichum on splash cups Antherozoids (sperm equivalent) are produced in tiny sacs, called antheridia. On their release from the antheridia, the antherozoids must then swim through surface water to fertilize neighbouring egg cell The habit shot Longitudinal section through a splash cup.
    • Archegonia ;
    • Relatively small (except haircap mosses
    • eg: Polytrichum )
  • Polytrichum sp - archegonium
    • The archegonia produce the female sex cells or gametes inside the swollen part of the archegonium which is called the venter .
    • this is connected to the outside world by a canal which runs down the centre of the neck, and down which the sperm cells must swim to fertilize the egg cell.
    Neck canal cells
    • Orthotrichum pusillum produces clusters of archegonia
    • The moss Orthotrichum pusillum produces clusters of antheridia and archegonia at the ends of separate branches on the same plant (an arrangement called “monoecious")
    • A cluster of archegonia forms at the tip of a female stem.
    • Each archegonium consists of an enlarged egg-containing basal portion (the venter) and a long neck with a central canal.
    • Sperm are guided down the canal to reach the egg.
  • During embryo elongation archegonium undergoes several changes…. Ptychomnion aciculare  - Fertilized archegonia enlarge to form red , pencil-like structures. The fine thread-like structure at the tip is the neck region of the original archegonium Ptychomnion aciculare  - Continuing growth of the embryo tears open the archegonium to expose a short red stalk (seta ). The seta elongates carrying the top half of the archegonium (calyptra) upward. A capsule with spores develops at the tip of the seta.
  • Variations of Sporangia in Three Classes of Division Bryophyta
  • Again, a class wise view….. Class : Sphagnidae Eg : Sphagnum
    • Sporophyte consists with a foot , very short seta & a capsule.
    • Capsule color varies from red to blackish brown.
    • Capsules are nearly spherical., raised on a stalk called pseudopodium ,a part of the gametophyte & may be up to 3mm long .
    Capsule(sporangium) Pseudopodium seta Operculum
  • Three capsules from Sphagnum henryeuse . Two are round (unexploded) and one that has already exploded. .
    • Operculum separates the rest of the capsule by a circular groove.
    • Capsule dries, operculum blown away with an audible click
    At the top of the capsule , lid like operculum
  • Habit shot of the low-growing Sphagnum moss showing reproductive heads with capsules raised above the mat by pseudopodia . Some capsules are round and not yet exploded, and some have recently exploded (cylindrical).
  • Class: Andreaidae Eg : Andreaea
    • Andreaea , like  Sphagnum , uses a  pseudopodium
    •  
    • However, its capsule opens along 4 longitudinal slits and form the characteristic lantern appearance.
    • The capsule remains intact above and below these dehiscence lines.
    • The mechanism of spore discharge , by means of slits in the capsule, is different from that of any other moss.
    Lantern appearance of capsules
    • The sporangium of the lantern moss is open here, to disperse spores.
    • A few spores can be seen inside. When the sporangium is dry, it opens along 4 or 5 longitudinal slits , and the columella (like a post in the middle) compresses.
    • If it is rewetted, it can close again.
    • The sporangium may open and close many times, dispersing the spores over a long period of time.
    • without a peristome.
  • Sporangia ( capsules) of Andreaea
    • Class: Bryidae
    • eg : P ogonatum
    • Consist of a foot , a seta & a capsule
    Capsule Seta Foot
    • Sporangium…………
    • Usually take 6-18 months to reach maturity in temperate species.
    • elevated on a seta into the air ,facilitating spore dispersal.
    • Capsule Sporangium
    At maturation Sporangia without operculum
  • Some mosses produce brightly colored sporangia to attract insects
  •  
    • SPORANGIUM (Capsule)………
    • Supported by a slender stalk the SETAE
    • When it is young, the sporophyte is protected by a hat-like covering, the CALYPTRA
    • The calyptra is actually maternal gametophyte tissue, a remnant of the archegonium.
    • Until the spores are mature, the mouth of the capsule is covered by a cap-like lid, the OPERCULUM , which eventually falls off to allow spore release
    • Spore release is typically regulated by one or two rings of teeth around the mouth of the capsule, the PERISTOME.  
  • The calyptra
    • derived from the archegonium.
    • Is commonly lifted upward with the capsule as the seta elongates.
    • Prior to the spore dispersal , the protective calyptra falls off, revealing the teeth, the peristome
    The Peristome
    • surrounds the opening of the sporangium.
    • the teeth of the peristome are formed by the splitting, along a zone of weakness, of a cellular layer near the end of capsule.
    • In most mosses, the teeth uncurl when the air is relatively dry & curled up when moist.
    The movements of teeth expose the spores. Which are gradually released
  •  
  • Ptychomitrium polyphyllum showing the calyptra on the left capsule and the exposed peristome on the right
  • The peristome is different in morphology across species, and is used as a classification tool. In all species, however, it opens and closes in response to changes in humidity Moss capsule cross section
    • Callicladium haldanianum (or possibly Brachythecium oxycladon ) showing a well-developed peristome with two rings of teeth
    • Entodon seductrix capsules at various stages of development
  • Structural variations in Capsule (Sporangium) of Division Bryophyta
    • Variations of Seta
    • Variations of Capsule (Sporangium)
    • Variations of Calyptra
  • Curled seta So short seta (reduced) Astomum muhlenbergianum
  • Pohlia nutans Bryum argenteum  - capsule inverted.  Variations of Sporangia (Capsules)
  • Capsules of  Pleurophascum grandiglobum Tayloria callophylla  - capsule erect  Capsules of Entosthodon apophysata Tayloria gunnii
  • Immersed capsules Physcomitrium pyriforme, capsule shaped like a child’s toy top The capsules elevated slightly above the linear leaves, have a broadly tapered neck that contributes to an unusual overall shape reminiscent of a weather balloon
  • Spore capsules of the moss  Funaria hygrometrica . The green capsules contain immature spores and the brown capsules contain mature spores.   Funaria   with a long seta and an inclined capsule.
  • Cylindrical capsules
  • T .  Hypnum , a recurved capsule.   G.polytrichum   large capsules are somewhat angular on their sides  H.  Diphyscium has a very short seta so that the capsules lies surrounded by the perichaetial "leaves".
  • Variations of Calyptra The sporangium increases in size as the spores within develop. The archegonial covering known as the calyptra also enlarges and varies in size , longevity and shape , providing a characteristic useful in distinguishing different mosses from one another. Psilopilum crispulum  - As the capsule (green ) enlarges, the covering calyptra (red) splits open to expose the lid at the top of the capsule. 
  • Dawsonia superba  - The calyptra of this moss is cap-shaped (conical) and has a dense covering of woolly hairs Macromitrium longipes  - The calyptra is conical and pleated, forming a hood over the capsule beneath.
  •   Hypopterygium filiculaeforme  - The pointed, tapering calyptra are in the process of being shed from the two capsules to the right. 
    • References….
    • Reven.P.H.,R.F.Evert.& S.E.Eichhorn,Biology of Plants,7 th edition,2005, USA,pp:345-366
    • http://www.bobklips.com/earlywinter2009.html
    • http://comenius.susqu.edu/bi/202/ARCHAEPLASTI
    • DA/VIRIDIPLANTAE/Bryophytes/BRYOPHYTA/bryophyta.htm
    • ACKNOWLEDGEMENT…..
    • Mrs. Priyangani Senanayake
    • Dr.(Mrs.) Sagarika Kannangara
    • Mrs. Dinusha Gunawardana
    • Department of Botany
    • Group members………
    • BS/2007/042 – D.M.W.R Dissanayake
    • BS/2007/065 – A.U Gurusinghe
    • BS/2007/112 – H.K.K Nadeera
    • BS/2007/117 – D.T Paranagama
    • BS/2007/126 – W.I.A Perera
    • BS/2007/140 – R.H.A.A Ranasinghe
  • Thank You
  •