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  • Comment on the lifecycle and nature of a fern prothallus

 Comment on the lifecycle and nature of a fern prothallus.

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Pteridophytes show a haplo-diplontic life cycle.

Formation of spores:
The main plant body is a diploid sporophyte, which contains sporophylls. The plant can be homosporous, or it can be heterosporous, producing haploid smaller microspores and larger megaspores.

Germination:
Germination of spores produces haploid, free-living gametophytes called prothallus. The homosporous ferns give rise to bisexual gametophytes, and heterosporous ferns give rise to separate male and female gametophytes.

Formation of gametes:
The prothallus consists of a haploid male sex organ, antheridia and a female sex organ, archegonia, which give rise to antherozoids and eggs, respectively.

Fertilisation:
Fertilisation occurs with the help of water. The diploid zygote develops into an embryo that finally forms a sporophyte.

Nature of the prothallus:

Fern, which is a type of pteridophyte, reveals a haplo-diplontic state. It bears prothallus in the gametophytic stage. Prothallus is the free-living, multicellular, inconspicuous, haploid, photosynthetic, thalloid gametophyte of pteridophytes. It bears unicellular rhizoids for attachment to the substratum. The requirement for damp and moist places is due to the requirement of water for fertilization.

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