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Difference Between Protonema and Prothallus | Protonema vs Prothallus

The prothallus is developed through the alteration of generation from the sporophyte which produces haploid spores. Haploid spores then germinate through mitotic division into prothallus. Then the prothallus undergoes independent development for few weeks and develops antheridia and archegonia that produces flagellated sperms and ova respectively. The motile sperms  (haploid) unite with the ova (haploid) through fertilisation process. A diploid zygote forms upon fertilisation. The zygote then divides and develops into a multicellular sporophyte. The sporophyte grows out of the prothallus in search of water and nutrition and develops into an individual fern.

What is the Similarity Between Protonema and Prothallus?

  • Both are gametophytes.
  • Spore germination develops both protonema and prothallus.

What is the Difference Between Protonema and Prothallus?

Protonema vs Prothallus

Protonema is a filamentous structure, which is thalloid and belongs to the gametophyte of mosses and some categories of liverworts. Prothallus is the gametophyte of pteridophytes.
 Appearance
Protonema has thread like shape. Prothallus is heart shaped.
Develops into
Protonema develops into gametophores which are leafy shoots. Prothallus develops into male and female sex organs.

Summary – Protonema vs Prothallus 

The protonema is a structure which appears as threads. They are developed during the very early haploid stage. Then through different sequential developments stages, the protonema develops into leafy shoots which are referred to as gametophores. It is a characteristic feature of all mosses and many of the liverworts except in hornworts. The protonema is mainly composed of two types of cells; chloronemata and caulonemata. Prothallus is the gametophyte stage of the life cycle of ferns and other pteridophytes. It is a heart-shaped structure. Prothallus develops through the germination of a spore. It is composed of both male and female reproductive units namely antheridium and archegonium. In some species of pteridophytes, chlorophyll is present in the prothallus and is capable of photosynthesis. This is the difference between protonema and prothallus.

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