Plant Kingdom

Lycopodium, Equisetum, Psilotum are homosporous. Those plants which produce only one kind of spores are called homosporous. Salvinia, Selaginella are examples of heterosporous plants that produce two kinds of spores; macrospore and microspore.

Both assertion and reason are false. Most of the pteridophytes are homosporous meaning they produce similar spores. Selaginella and Salvinia are exception. They produce two kinds of spores (microspores and megaspores). In Selaginella plant, there is seen the seed habit, so it is marked as precursor of seed habit evolution in plants.

Assertion : Heterospory and retention of female gametophyte are responsible for the origin of seed habit in Selaginella.

Reason : Psilotum is a living fossil.

Explanation :

Both the assertion and reason are true, but the reason does not correctly explain the assertion.

Heterospory and the retention of the female gametophyte are indeed responsible for the origin of the seed habit in Selaginella, a pteridophyte. Heterospory refers to the production of two types of spores—microspores and megaspores—by the same plant.

Psilotum, also a pteridophytic plant, is known for its primitive pteridophytic characteristics, which is why it is referred to as a living fossil. However, this does not explain the seed habit in Selaginella.

Summary of Key Points :

Heterospory : Production of two types of spores (microspores and megaspores) by the same plant.

Seed Habit in Selaginella : Originated due to heterospory and retention of the female gametophyte.

Psilotum : Known for its primitive characteristics and is referred to as a living fossil.

This clarification ensures that the linkage between the assertion and reason is correctly understood.