Question

The small heart-shaped gametophyte called a prothallus is part of the life cycle of the
A. Mosses
B. Ferns
C. Liverworts
D. Gnetophytes

Answer 1

The term prothallus is also sometimes used to describe a young liverwort or peat moss gametophyte. Gametophytes refer to the haploid cells which are otherwise known as gametes and are used in the process of reproduction.

Complete answer: The prothallus gametophyte is flat cordate, green, and thalloid in structure. They are non-vascular, free-living, inconspicuous, thin, multicellular, autonomous gametophytes which germinate when the spore falls on the soil. It is seen in most of the pteridophytes. The prothallus is monoecious or dioecious. It carries sex organs, including male antheridia and female archegonia. Prothallus is autotrophic in nature. The gametophyte is referred to as the prothallus of ferns and other pteridophytes. It is thick in one cell, normally formed by the heart or kidney and has no roots, stems or leaves, but it has rhizoids that anchor it to the soil and assist with absorption. A fern is a member of a group of non-vascular plants which have neither seeds nor flowers and reproduce through spores. They differ from mosses by being vascular as they show the presence of xylem and phloem and having life cycles in which the sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, which are tougher than microphylls called clubmoss. The majority of ferns are leptosporangiate origin ferns.
Therefore, option B is the correct answer.

Note: The fern prothallus is homothallic, with the lower surface of the prothallus carrying both antheridia and archegonia. The gametophyte process in the life of pteridophyte is usually a prothallus or prothallium. The prothallus emerges from a germinating spore. Usually, it is a short-lived and heart-shaped structure which is 2-5 millimetres broad.