Question

Which of the following statements is correct?
A) Protonema of moss and prothallus of Dryopteris are sporophytic.
B) Protonema of moss and prothallus of Dryopteris are gametophytic.
C) Moss protonema is sporophytic, Pteris prothallus is gametophytic but plant bodies of Pteris and Funaria are gametophytic.
D) Plant body of moss is gametophytic, while that of Dryopteris is both gametophytic and sporophytic.

Answer 1

Hint: Bryophytes include mosses and liverworts. They are commonly found in moist areas that are under a shade. Bryophytes are known as the amphibians of the plant kingdom, as these plants can survive in the soil but require water for sexual reproduction. They play a critical role in plant succession.

Complete answer:
A protonema is a thread-like structure of a chain of cells. It forms at the very first stage of a bryophyte life cycle. When a moss starts its life from a spore, it grows as a protonema. This protonema then develops into a leafy gametophore. The spores germinate straight into a new gametophyte generation. Whereas, a prothallium (also known as prothallus) of Dryopteris is almost always the gametophyte stage in its life cycle. The prothallus develops from a spore that is germinating. It is very short-lived. It is a concealed heart-shaped structure that is generally two to five millimetres in width. It has a number of rhizoids (hairs that look similar to roots) that grow below it and the male (antheridium) and female (archegonium) sex organs. Protonema of moss and prothallus of Dryopteris is gametophytic.

- A sporophyte is a diploid plant structure. It produces spores through asexual division (meiosis). Hence, protonema of moss and prothallus of Dryopteris is not sporophytic.
- Pteris and Funaria are gametophytic, but moss protonema is not sporophytic.
- Dryopteris is not sporophytic.

Hence, the correct answer is option B, protonema of moss and prothallus of Dryopteris are gametophytic.

Note: In all sexually reproducing plants, an alternation of generation is present between the gametophytic and sporophytic stages. Based on this alternation of generation, three types of life cycles are present in the plant kingdom. They are haplontic, haplo-diplontic, and the diplontic life cycles.