3. Introduction
• This theory was first proposed by Walter
Zimmermann in 1930 .
• This theory is based on fossil record and
synthesizes the major steps in the evolution
of vascular plants.
• According to this theory, all vascular plants
evolved either directly or indirectly from a
simple leafless Rhynia type ancestral from
made up of sterile and fertile axes.
4. Meaning of Telome Theroy
• A Telome is defined as “ the single – nerved
ultimate terminal portion of a dichotomising
axis.”
• I.g :- It is the point of the most distal
dichotomy to the tip of a branch. The
connecting axes between dichotomies are
called mesomes.
• Functionally , Telome are two types…
1. Fertile Telome
2. Sterile Telome
5.
6. Process of Telome Theroy
• According to Zimmermann, these Telomes of
primitive Rhynia type of vascular plants have
been subject to certain evolutionary process
in varying degrees among the taxonomic
groups.
• These evolutionary process are :-
1. Overtopping 2. Reduction
3. Plantation 4. Syngenesis
5. curvation
7. 1 . Overtopping
• In this process one of the two dichotomising
branches of the primitive axis produced by the
apical meristem outgrows or overgrows the
other.
• The larger axis thus produced become the
stem, while the shorter or overtopped
branches represent the beginning of lateral
branches or leaves .
8. 2 . Reduction
• In this process , the activity of terminal
meristem of each Telome of the truss becomes
suppressed resulting into much shorter branches
by decreasing the length of Telome and mesomes
• This process is responsible for the formation of
microphyllous leaves of the lycopsida and
sphenopsida as well as the needle like leaves of
conifers .
9.
10. 3 . Planation
• The process of Planation caused the Telome
and mesomes of the truss to shift a three
dimensional pattern to a single plane .
• The process of infilling with photosynthetic
and other tissues between the plannated
branches is called webbing which have led to
the evolution of flattened leaf like structure
with a dichotomously veined lamina .
11.
12. 4 . Syngenesis ( webbing )
• This is an evolutionary process
Where tangential fusion of
Mesomes and Telome takes
place .
• The lateral fusion of sterile
vegetative
Telome and mesomes resulted
into complex
Anastomosing vascular systems
in stem.
13. 5 . Curvation
• This evolutionary process is caused due to
the unequal growth of the tissues on two
opposite flanks of the Telome.
• It has two sub processes :-
1 . Recurvation
2. incurvation
14. A . Recurvation
• In this sub processes the Telome bends inward an
axis.
• The inward projecting sporangia on a
sporangiophore of Equisetum the result of this sub
process .
15. B . Incurvation
• In this sub process, the fertile Telome bends
downward resulting in the downward shifting
of the sporangia from terminal to the ventral
surface of the leaf .
16. Merits of the Telome Theory
• It is outcome 0f a master mind that has
portrayed , in a skilful manner the origin and
evolution of the saprophytes of land plants.
• Many of his assumptions are correct and
based on exact phyletic relationships
between the varions groups of plants both
living and extinct.
• It explains in a nice manner that the entire
saprophytes is an axis that has an
underground portion called the root and an
aerial part called the shoot .
17. Demerits of the Telome Theory
• The Theory is open to criticism in its
application to the origin of lycophyta .
• The origin of microphyllous leaves of the
lycophyta by reduction of the Telome trusses
is not exemplified by any living or extinct
vascular plant .
• Zimmermann scheme for the pteropsida or at
least some pteropsida , has much supporting
evidence .
