The document discusses two theories of evolution of sporophytes in bryophytes: the theory of sterilization and the reduction theory. The theory of sterilization proposes that sporophyte evolution involved the progressive sterilization of potentially fertile cells, which can be seen in the increasing complexity of structures like elaters in Riccia, Marchantia, Pellia, Anthoceros, and Funaria. The reduction theory proposes the opposite - that evolution proceeded through a reduction and simplification of sporophyte structures like stomata and dehiscence mechanisms. The simplest sporophyte of Riccia is considered highly evolved under this theory due to extensive reduction.

1. SPOROPHYTIC
EVOLUTION
IN
BRYOPHYTES
AindiraPriyadarsini
Lecturerinbotany
Svagdc,(M)srikalahasti

2. Learning outcomes
1. Sporophyte of Bryophytes -General features
2. Theories of evolution of sporophytes
A.Theory of sterilization
B. ReductionTheory

3. Sporophyte of Bryophytes -General
features
The sporophyte lacks lateral appendages and is
incapable of self-nutrition, which it gets it wholly or
partially from the parent gametophyte to which it is
attached throughout.
The sporophyte of most of the bryophytes show
mostly the same fundamental aspects like
anchoring and absorbing foot, a stalk- like seta for
conduction, support and a capsule, which will have
spores and elaters.

4. Theories of evolution of sporophytes
 a. Theory of sterilization
 The series of sporophyte in Bryophytes show a natural
advance in the progressing elaboration and complexity
(Bower,1908) supported by Cavers(1910), Campbell(1940)
and Smith.
 The fundamental principle involved in this is Progressive
sterilization of the potentially fertile cells (Sporogenous
tissue).
 The following sporophytes of Riccia, Marchantia, Pellia,
Anthoceros and Funaria are studied in detail which are
showing progressive sterilization of sporophytes.

5. The sporophyte of Riccia:
 It is simplest among Bryophytes and has
least amount of sterile tissue.
 The entire embryo forms the spore
producing capsule
 Foot and seta are lacking.
 It only produces spore, does not
distribute.
 It does not dehisce to allow the spores
to escape.

6. The sporophyte of Marchantia:
 Only half of the sporogenous cells develop into
sporophytic mother cells.
 The other half develop into hygroscopic sterile
elaters which help in spore dispersal.
 It illustrates a step further in progressive
sterilization of the sporogenous tissue and its
elaboration.

7. The sporophyte of Pellia:
 The sporogenous tissue of the endothecium forms
the spore mother cells and the sterile elaters.
 The elaters are long slender with double spiral
thickening on their walls. Some of the sterile
elater cells become compact and form
elaterophores, that are used in spore dispersal.
 The sterilization process is advanced further
forming efficient spore dispersal structure.

8. The sporophyte of Anthoceros:
 It shows a step further than Pellia in the
progressive sterilization of the potential
fertile tissue.
 At the centre a sterile columella is formed.
 The capsule wall develops a well ventilated
photosynthetic tissue protected by the
epidermis containing perfect stomata like
structures.

9. The sporophyte of Funaria:
 Major parts of the sporophyte remain sterile and
form the foot and seta. The capsule is pear
shaped structure with its basal sterile part known
as apophysis and theca.
 Annulus is present which helps in spore dispersal.
 The progressive sterilization of the potentially
sporogenous tissue is increased here which gives
the explanation for the Bowers theory of
sterilization for the evolution of sporophyte in
Bryophytes.

10. B. Reduction Theory
 There is opposite school of thought led by Kashyap, church,
Goebel and Evans.
 They hold that the evolution is in downward direction; the series
shows the retrogressive evolution.
 This type the reduction is accompanied by simplification of the
structure of the sporophyte.
 The stomata first became functionless (eg. Sphagnum) and later
on disappeared as in Marchantiales and Jungermanniales.
 On the basis of this the simplest sporophyte of Riccia is
considered as highly evolved though reduced as result of
progressive simplification.

11. Reduction Theory..
 Simplification in dehiscence apparatus.
 Reduction in the photosynthetic tissue in the capsule wall.
 The changes slowly eliminate the seta and foot.
 All these changes happen for the progressive increase in the
fertility of the sporogenous cells.
 Evidence from comparative morphology and experimental
genetics support the view the simple Riccia sporophyte is more
advanced but a reduced structure.

12. Take away points
 Sporophyte of Bryophytes -General features
 Theories of evolution of sporophytes
A. Theory of sterilization
B. Reduction Theory
 Studied the following sporophytes of
 Riccia
 Marchantia
 Pellia
 Anthoceros and Funaria.

13. Thankyou
AindiraPriyadarsini
Lecturerinbotany
Svagdc,(M)srikalahasti