Question

Zygotic meiosis takes place in
A. Selaginella
B. Spirogyra
C. Pinus
D. Brassica

Answer 1

Zygotic meiosis is also referred to as the haplontic life cycle. A haploid thallus is the characteristic of this life cycle. The cycle involves only an individual type of free living organism therefore it is also known as haplobiontic life cycle.

Complete answer:
Zygotic meiosis as the name suggests is referred to as the meiosis of zygote. It takes place in some of the lower plants and animals. They don’t form haploid gametes. Sex cells of both male and female are diploid. They fuse and form tetraploid zygote. This zygote undergoes meiosis, thus forming a diploid zygote. Spirogyra bears haploid plant body forming zygospores after the gametic fusion. The nucleus of these zygospores undergoes zygotic meiosis thus forming four haploid nuclei. Three out of these four nuclei degenerate while only one being functional. Under favorable conditions, germination of these zygospores of Spirogyra takes place. Spirogyra displays haplontic life cycle and thus shows zygotic nucleus.
On the other hand, Selaginella is a bryophyte, Spirogyra is a green alga, Pinus is a pteridophyte and Brassica is an angiosperm. But zygotic meiosis takes place only in lower plants and as bryophyte, pteridophyte and angiosperm are higher plants. So, green algae that is the Spirogyra undergoes zygotic meiosis.

Hence, the correct answer is option (B).

Note: Common names of Spirogyra are blanket weed, mermaid's tresses and water silk. It is a filamentous green alga belonging to order Zygnematales. This genus spirogyra is characterized by spirally or helically arranged chloroplasts.