Question

When the spore of a fern plant falls on moist ground, it germinates to form a green filament. It soon grows into a flat, green, heart shaped structure known as-
A. Adventitious thallus
B. Gametophyte thallus
C. Sporophyte
D. Prothallus

Answer 1

Pteridophytes are also known as ferns. They are produced by spores. Spores can be yellow, black, white etc. the ferns are grown from the small, circular flat structure which are called spores. Spores are developed from both sexual reproduction and asexual reproduction too. A male gamete and female gamete required for sexual reproduction and spores are formed.

Complete answer:
Option A: Adventitious thallus- adventitious thallus are the outgrown structures or advanced structures which can be grown from any part of the plant.
Option A is not the correct answer.
Option B: Gametophyte thallus- Gametophyte thallus are thalli grown from gametic parts of the plant such as male strobili or female strobili; they are unlike adventitious thallus.
Option B is not the correct answer.
Option C: Sporophyte- sporophyte are the structures from where spores are formed. When a spore falls on the ground they germinate into a sporophyte.
Option C is not the correct answer.
Option C: Prothallus- prothallus of pteridophyte is the heart-shaped, flat structure in the life cycle of fern.
Option D is the correct answer.

Therefore, Option D is the correct answer.

Note:
Pteridophytes are formed from the meiosis mode of cell division. Most common example of pteridophytes is ferns, apart from ferns other examples of pteridophytes are- Selaginella, silver fern, Lycopodium etc. they are found in wet and damp places, in moist and shady places. They are tropical and vascularized plants.