Question
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The life cycle of Selaginella/ fern is
(a)Diplontic
(b)Haplo-diplontic
(c)Haplontic
(d)Diplo-haplontic

Answer
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Hint: In this plant a dominant sporophytic phase and a short-lived gametophytic phase are present. Selaginella is commonly known as ‘spike moss’.

Complete answer:
Selaginella is a pteridophyte which is mainly seen in humid temperate and tropical rainforests. Selaginella exhibits a regular alternation between sporophytic and gametophytic generations. It is a free-living plant with a distinct root, stem, and leaves and it grows for a long time. It reproduces asexually by the formation of haploid spores within the sporangia. The spores germinate into separate male and female gametophytes. The gametophytes are haploid, free-living, and exist for a short time only. They represent the second phase in the life cycle of Selaginella. The male gametophyte produces male gamete in the antheridium, while the female gametophyte produces the egg in the archegonium. Male and female gametes fuse, forming a diploid zygote. The first cell of the sporophytic generation is the zygote. From the zygote, a free-living, the sporophyte is produced. Thus, in the life cycle of Selaginella, a distinct alternation between sporophytic that is diploid and gametophytic that is haploid generations can be seen.
So, the correct answer is diplo-haplontic.

Note:
 -The male sex organ in non-flowering plants is called an antheridium and the female sex organ in non-flowering plants is the archegonium.
-A gametophyte is a haploid gamete producing form of a plant and a sporophyte is the spore-producing form of the plant.
-The diplohaplontic life cycle is also referred to as haplodiplontic, diplobiontic, or dibiontic life cycle. In this life cycle, multicellular diploid and haploid stages occur and meiosis has occurred in ‘sporic’ condition.