Question

What is meant by thallus?

Answer 1

Hint: Thallus is the plant body of algae, fungus, and other lower creatures that used to be classified as Thallophyta. A thallus is a multicellular structure made up of filaments or plates of cells that can range in size from a single cell to a complex treelike structure. It has a basic structure with no specialised components like a stem, leaves, or conducting tissue that are seen in higher plants.

Complete answer:
The undifferentiated vegetative tissue of some species, such as algae, fungus, some liverworts, lichens, and the Myxogastria, is known as thallus, which means "a green shoot" or "twig". Previously, many of these creatures were classified as thallophytes, a polyphyletic group of closely related organisms. Thallodal, thalliform, and thalloid are all terms for organisms or structures that resemble thallus.
The complete body of a multicellular non-moving organism with no arrangement of tissues into organs is referred to as a thallus. Even while thalli do not have the same organised and distinguishable elements as vascular plants (leaves, roots, and stems), they may have homologous structures that are similar to their vascular "equivalents".
An analogous structure has a similar function or macroscopic structure but a different microscopic structure; for example, no thallus has vascular tissue. In rare cases, such as the Lemnoideae, where a vascular plant's structure is thallus-like, it is referred to as having a thalloid structure, or sometimes as a thalloid structure.
Although the anatomy of a thallus is mostly homogeneous, there can be apparent differences as well as functional variances. The thallus of a kelp, for example, may be separated into three parts. The holdfast to anchor, stipe to hold the blades, and blades are all elements of a kelp thallus for photosynthesis.

Note:
A fungus's thallus is commonly referred to as a mycelium. The term thallus is also used to describe the lichen's vegetative body. Thallus is also known as 'frond' in the seaweed world. Prothallus is the gametophyte of various non-thallophyta plants such as clubmosses, horsetails, and ferns.