What is Telome theory in Pteridophytes?

telome theory The theory that the leaves (megaphylls) of ferns and seed plants evolved by the modification of terminal branches (telomes) of stems. It envisages that firstly, instead of the primitive equal (dichotomous) branching of the stem, there developed a main axis with lateral side branches.

What is Telome concept in botany?

Definition of telome : a hypothetical plant structure in a theory of the evolution of leaves and sporophylls in vascular plants that consists of one of the vegetative or reproductive terminal branchlets of a dichotomously branched axis.

What is the merits of Telome theory?

This is a simple concept and explains most of the morphological problems about different organs of a plant. According to Bierhorst (1971) this theory is too simple and too easily applicable but unfortunately its excessive use has greatly diminished its value.

Who proposed Telome theory?

Zimmermann defines the telome as the single-nerved extreme portion (at base or apex) of the plant body from the tip to the next point of branching. The following two types of telomes have been recognized on the basis of their function: Vegetative or sterile telomes: without sporangia also called phylloids.

How Telome concept supports the evolution of Pteridophytes?

This theory is based on fossil record and synthesises 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 form made up of sterile and fertile axes (the telomes).

What is Telome truss?

A “telome” is defined as ultimate terminal portion of a dichotomising axis i.e., it is the point of the most distal dichotomy to the tip of a branch. Several telomes, either fertile or sterile, becomes grouped together by connecting mesomes to form a more complex structure, called syntelome or telome truss.

How telome concept supports the evolution of Pteridophytes?

What is Enation theory?

enation theory The theory that accounts for the origin of the fern leaf by suggesting that it arose from the development of simple outgrowths (enations).

What is a Telome explain the steps involved in the origin of Megaphyllous leaves through Telome theory?

According to the telome theory, megaphylls evolved from the three-dimensional lateral branches of early vascular land plants in a hypothetical series of three transformations; first, the formation of determinate lateral branches (overtopping); second, the development of ‘flattened’ branch systems (planation); and third …

What is telome and Mesome?

This theory is based on fossil record and synthesises the major steps in the evolution of vascular plants. A “telome” is defined as ultimate terminal portion of a dichotomising axis i.e., it is the point of the most distal dichotomy to the tip of a branch. The connecting axes between dichotomies are called mesomes.

What is telome and Syntelome?

Several telomes, either fertile or sterile, becomes grouped together by connecting mesomes to form a more complex structure, called syntelome or telome truss (Fig. 7.134).

What are Telome and syn Telome?

What is the telome theory in biology?

The telome theory is due to the work of Zimmermann. He goes back to the earliest and simplest type of vascular plant known, that in the Psilophytales in which the body consists of branching leafless axes, which are all substantially alike.

What is the telome theory of Psilopsida?

1. Psilopsida: The telome theory can be applied to interpret the evolution of a synangium of Psilotum. The overtopping, reduction and syngenesis have combined to produce a synangium of Psilotum (Fig. 7.139A-D).

Is the telome theory ‘misfit’ for interpreting the origin and evolution of microphylls?

Hence, the Telome theory is ‘misfit’ for interpreting the origin and evolution of microphylls in Lycopsida. This theory was propounded by F. O. Bower (1935). The enation theory seems to be more convincing than the telome theory for explaining the origin of microphyllous leaves (Fig. 7.143A-D).

What is the fusion of sterile vegetative telomes and mesomes?

The lateral fusion of sterile vegetative telomes and mesomes resulted into complex anastomosing vascular systems in stem (e.g., polystelic condition in Selaginella). The fusion of fertile trusses with their terminal sporangia resulted in the formation of synangia of Psilotum.