Question

Fern spores are actually-
a. Haploid
b. Diploid
c. Triploid
d. Tetraploid

Answer 1

Hint: Spore is a reproductive cell which is capable of developing into a new individual without fusing with a reproductive cell. The ploidy of the spores differs in fern. This difference in ploidy is seen during the spore producing generation and the gamete producing generation.

Complete answer:
> The fern spores are generally haploid and unicellular. They are produced by meiosis in the sporangium of a diploid sporophyte. Under the favorable conditions spores can develop into a new organism through mitotic division and can also produce multicellular gametophyte. A fern generally shows two free-living generations in them. They are a diploid sporophyte generation or a spore-producing plant and a haploid gametophyte generation or a gamete-producing plant. Option (a) Haploid is correct as the fern spores are haploid.

> When the spores are produced, they remain inside the sporophyte which is diploid. So, the spores are actually haploid structures staying in a diploid sporophytic structure. Option (b) Diploid is incorrect.

> The option (c) Triploid is also incorrect as no such stage is seen in case of fern in their life cycle.

> The option (d) Tetraploid is also incorrect as the fern spores are haploid and no tetraploid stage is observed.

Hence, The correct answer is option (A).

Additional information:
Ferns belong to Pterophyta and are characterized by vascular plants with leaves arising from subterranean called fronds and creeping rhizomes. The dominant part of the life cycle of ferns is the diploid or the leaf-bearing sporophyte stage. On the underside of the leaves, there are several rows of sori and each of the sorus is composed of a cluster of sporangia. These sporangia are also sometimes covered with inducium.

The spore mother cell inside the sporangium undergoes meiosis and produces numerous amounts of haploid spores. The sporangium then splits and opens when it matures. This releases millions of spores. Each of these spores germinates and grows into a heart-shaped gametophyte or prothallus. This haploid gametophyte generally bears a male and a female sex organ, called antheridia and archegonia respectively. The ferns also have a primitive method of fertilization involving a multiciliate sperm which swims through water to reach the egg.

Note: Plants we see as ferns are the sporophyte generation. The process of spore production in these spores are unique. The sporophyte here, releases spores during the summer season. Spores must land on a suitable surface, such as a moist and a protected area to germinate and to further grow into gametophytes.