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: Understanding the Concept:
The question asks about the mode of gametophyte development in homosporous pteridophytes. This refers to whether the gametophyte develops inside or outside the original spore wall.
Step 2: Detailed Explanation:


Homosporous pteridophytes produce only one type of spore, which is typically small. These spores are released from the parent sporophyte.

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

In contrast, heterosporous pteridophytes (like Selaginella and Salvinia) produce two types of spores: small microspores and large megaspores. Their gametophytes are highly reduced and develop mostly or entirely inside the spore wall. This is called endosporic development.

Hemisporic and Episporic are not standard terms for this classification.

Step 3: Final Answer:
The development of the gametophyte in homosporous pteridophytes is exosporic.