Question

Choose the correct option:
The heterosporous pteridophytes are _______________.
a) Lycopodium and Pteris
b) Selaginella and Psilotum
c) Selaginella and Salvinia
d) Dryopteris and Adiantum

Answer 1

Hint: Heterospory is the term that refers to the occurrence of two different types of spores i.e. megaspore and microspore on the same plant.

Complete answer:
To answer this question, we must understand the heterospory in pteridophytes:
> Heterosporous plants produce two types of spores, namely the megaspores (female) and microspores (male) on them. This condition is considered as an evolutionary stage in the development of land plants. The phenomena of heterospory was reported in Pteridophytes for the first time.

> Pteridophytes are considered as an intermediate between the primitive and higher plants. Most of them exhibit homospory, but some of them do exhibit heterospory.

> Heterospory is of immense biological significance because it marked a starting point where the sporophyte became independent and the gametophyte became completely dependent on it. Fertilization of the egg and retention of the zygote inside the megaspore signify the origin of seed habit. Thus, we can say homosporous is a primitive condition while heterosporous is derived as a result of evolution.

> The most widely studied pteridophytic genera in order to understand heterospory and seed habit in Selaginella.

> The major structural difference among the heterosporous and homosporous pteridophytes lie in the size of their spores and this is evident from the fossil records as well. The smaller spores are produced inside the microsporangia and are known as microspores. These germinate to give rise to the male gametophyte. The larger spores develop inside the megasporangia and are known as megaspores. These germinate into the female gametophyte.

As stated earlier, most of the pteridophytes are homosporous (having identical cells) e.g. Equisetum and a very few pteridophytes like Selaginella and Salvinia are heterosporous (having megaspores and microspores).

Thus, the correct answer is option C- Selaginella and Salvinia

Note: The difference between heterosporous and homosporous pteridophyte lies in the size of their spores. The heterosporous pteridophytes produce megaspores as well as microspores while homosporous pteridophytes produce only homosporous which are of same size.