Question

In homosporous pteridophyte species, the development of gametophyte is

• A. Hemisporic
• B. Episporic
• C. Endosporic
• D. Exosporic

Hint:

Remember the prefixes: \textbf{Exo-} means "outside," and \textbf{Endo-} means "inside." Homosporous species release their spores, which then grow into a gametophyte outside the spore wall (exosporic). Heterosporous species keep the developing gametophyte protected inside the spore wall (endosporic), a key step in the evolution towards the seed habit.

Answer 1

The Correct Option is D

Step 1: Concept Overview:
The question concerns the mode of gametophyte development in homosporous pteridophytes, specifically whether it occurs inside or outside the original spore wall.
Step 2: Detailed Explanation:


Homosporous pteridophytes produce a single type of small spore, released from the sporophyte.

Upon germination in a suitable environment (e.g., moist soil), the spore wall ruptures, and the gametophyte develops outside the spore wall. This exosporic development results in a free-living, independent, and typically photosynthetic gametophyte, characteristic of homosporous ferns and lycophytes.

In contrast, heterosporous pteridophytes (e.g., Selaginella and Salvinia) produce microspores and megaspores. Their reduced gametophytes develop mostly or entirely inside the spore wall, termed endosporic development.

Hemisporic and Episporic are not standard terms for this classification.

Step 3: Conclusion:
Gametophyte development in homosporous pteridophytes is exosporic.