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
May be in the form of
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
born on a specific structure called antheridial head
Spherical or elongated in shape
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 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 )
Gametangia are associated with leaves along the shoot.
Antheridia are equally elongated with a long narrow stalk and banana-shaped antheridial body
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.
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.
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
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 .
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.
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
eg : P ogonatum
Consist of a foot , a seta & a capsule
Capsule Seta Foot
Usually take 6-18 months to reach maturity in temperate species.
elevated on a seta into the air ,facilitating spore dispersal.
At maturation Sporangia without operculum
Some mosses produce brightly colored sporangia to attract insects
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.
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
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
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.
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.
Reven.P.H.,R.F.Evert.& S.E.Eichhorn,Biology of Plants,7 th edition,2005, USA,pp:345-366