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SORAL EVOLUTION IN
Chayanika Chowdhury;BOTANY HONS.;2ND SEM
1. DEFINITION OF SORUS.
2. TYPES OF SORUS.
3. INDUSIAL PROTECTION.
4.POSITION OF SORUS.
Definition of sorus:
Sorus, plural sori, in botany, brownish or yellowish cluster of spore-producing
structures (sporangia) usually located on the lower surface of fern leaves.
A sorus may be protected during development by a scale or flap of tissue called
TYPES OF SORUS
1. THE SIMPLE SORUS.
2. THE GRADATE SORUS.
3. THE MIXED SORUS.
:THE SIMPLE SORUS:
The Simplices are primitive and extend to the Paleozoic.
All sporangia within a sorus may be at the same stage of
development (Simplices) The sporangia in such a sorus
development simultaneously and all of them mature together.
E.g. Ophioglossum and Osmunda.
:THE GRADATE SORUS:
In such cases the internal space within the radial sorus gets filled by overlapping
Overcrowding results and there is no space for the proper dehiscence of
sporangia and consequently some of them do not dehisce.
The Gradate with an oblique annulus, occupy a middle position and have been
discovered in the Mesozoic.
EX: Dicksonia, Loxosoma, Trichomanes, Cyathea, Als ophila, etc
:THE MIXED SORUS:
The spores are released in a staggered fashion and even if the
environmental conditions are not favorable when the spores are initially
released; this problem is solved by a constant crop of spores over a
given length of time.
Mixtae annulus is present but in a vertical fashion.
e.g. Polypodiaceae(Adiantum,Pteris,Pteridium, Davallia)
: INDUSIAL PROTECTION :
The indusium may be formed as an epidermal
outgrowth covering receptacle and sporangia (true
indusium) or it may merely be the in turning of the
margin of the leaf to protect the sporangia (pseudo
indusium or false indusium).
:POSITION OF SORUS IN FERNS:
The Ophioglossales are group of interesting ferns in which the
sporangia are marginal in position.
1. In Maeattia, Angiopteris,Danaea etc…the sori are elongagated and
are situated below the lateral veins.
2. In christensia the sori are naked, circular and are irregular arranged
between the lateral veins.
3. In Adiantum the sporangia develop on the underside of special
marginal flaps of lamina that become reflexed and protect the sorus
5. The sori in Mattoniaceae are ventral in position and are usually
arranged in two rows on either side of the midrib. In
Glecheniaceae, the sporangia from distinct sori on the ventral
surface of the leaves.
6. The sporangia in Osmunda ,Davalia, Trivhomanes and many other
ferns are also marginal in position
7. In Salviniales the smaller sporocarp contain many microsporangia
each and the larger ones contain one or more megasporangia per
8. The sporocarp in Marsilea enclose sori that contain both micro and
9. In Marsileales and the Salviniales the sporangia develop in sori
that are borne within distinct structure called the Sporocarp.
FROM THE ABOVE PRESENTATION ,WE CAN CONCLUDE THAT THE SORUS IS
SPECIALISED REPRODUCTIVE STRUCTURE.THE PRESENT ADVANCED
STRUCTURE OF SORUS HAS DERIVED FROM SUCCESSSIVE CHANGE IN THE
STRUCTURE.THE SORUS HAS BEEN COVERED BY INDUSIUM FOR BETTER
PROTECTION. DIFFERENT MECHANISM OF SPORE DEHISCENCE HAS BEEN
EVOLVED .THE GERMINATION OF SPORES HAS BECOME MUCH MORE EASIER .
THIS IS THE EVOLUTION OF SORUS IN FILICOPSIDA.