Question

How many meiosis occurs in the sporangium of Nephrolepis?
(a) 1
(b) 4
(c) 16
(d) Uncertain and variable

Answer 1

Hint: Nephrolepis is a type of fern that exhibits a dominant sporophytic plant body that produces spores asexually. A spore is a one-celled structure that is a product of meiosis in ferns.

Complete answer:
The division of Pteridophytes includes horsetails and ferns. They are used for medicinal purposes and as soil binders. They are considered the first terrestrial plants due to the presence of vascular tissues i.e xylem and phloem for the conduction of water and food respectively. Their habitat includes cool, damp, and shady places although some flourish well in sandy soil conditions also.
Nephrolepis is a type of fern whose main plant body is sporophytic which is differentiated into true roots, stem, and leaves. Their main characteristic feature though is the presence of sporophylls. These are leaves bearing sporangia. Several sporophylls condense to form a compact structure known as strobili or cones. Diploid spore mother cells are present in these sporangia. They undergo meiosis one time to produce 4 haploid spores.

Additional Information:
- The haploid spores are released from the sporangium and dispersed by wind currents to a new substratum.
- After falling on suitable soil, the germination of spores produces a green, thalloid, and free- living gametophyte known as prothallus. It represents the gametophyte stage in its life cycle.
- The prothallus bears both the type of sex organs i.e antheridium or male sex organ and archegonia or female sex organ. Antheridium produces motile sperms that require water to make its way to the mouth of archegonia.
- Their fusion produces diploid zygote that begins to divide within the archegonium of fern. This marks the beginning of the sporophyte stage.
So, the correct answer is ‘1.’

Note:
- Pteridophytes are of two types depending upon the type of spores produced by the sporophytic plant body. These are homosporous and heterosporous pteridophytes.
- Homosporous pteridophytes produce only one kind of spores and thus no specialization in their gametophytes. E.g. Clubmoss.
- Heterosporous pteridophytes produce two types of spores-a larger megaspore and a comparatively smaller microspore. Megaspore gives rise to female gametophyte while microspore gives rise to a male gametophyte. E.g Selaginella.