Question

What is a thallus organisation?

Answer 1

Hint: Thallus is the undifferentiated vegetative tissue which is the green shoot and in some other groups such as fungi, algae etc. The thallus consists of the whole body of a multicellular and non-motile organism. They belong to the group thallophyta.

Complete answer:
Thallus organisation is seen in certain organisms like fungi and algae. It includes other lower organisms. The thallus is defined as an undifferentiated flat tissue that takes place as a filament and can occur as a unicellular structure to complex and unbranched tree-like filaments. The thallus consists of filaments or plates of the cell which forms the tree-like structure and consists of a simple structure that does not contain any specialised tissue such as conducting tissues, stems and leaves. They do not have organised and distinct parts but resemble the vascular equivalents with analogous structures. It consists of visible differences and functional differences and is usually called mycelium which is a thallus of fungus.
An alga is composed of a plant body that is always a thallus and is not differentiated into stem, leaves and roots. They are present in the colonial form and are filamentous with non- septate and multinucleate saponaceous tubes. In the saponaceous tube, the nuclear division takes place without the formation of the septa. The algae consist of motile and non-motile structures of thallus with palmelloid and dendroid aggregates. The collection of cells forms the aggregate which does not have a fixed number of cells shape or size and forms irregular colonies like mass. They are heterotrichous and pseudoparenchymatous.

Note:
The thallus is found in algae, mosses, fungi and liverworts and ferns and club mosses in their gametophytic generation. When the whole thallus of the fungus gets converted into the reproductive cell then the cell is known as holocarpic.