Biology · Plant Kingdom · NEET
It is only about the NUMBER of spore types a plant makes. Homosporous = one kind of spore, and every spore is the same size and looks alike. Heterosporous = two kinds of spores: large megaspores (also called macrospores) and small microspores. 'Homo' means same, 'hetero' means different. That is the whole idea.
Only TWO genera: Selaginella and Salvinia. NCERT gives exactly these two as the heterosporous examples. Every other pteridophyte you study (Lycopodium, Psilotum, Equisetum, Pteris, Dryopteris, Adiantum) is homosporous. NEET repeats this pair many times, so memorise 'SS = Selaginella and Salvinia'.
Equisetum is HOMOSPOROUS. Students confuse it because it forms cones (strobili), but cones have nothing to do with spore type. NEET 2017 tested exactly this: 'Equisetum – Homosporous' is a correct match. Do not mix cones with heterospory.
They are the two spore types found only in heterosporous plants. Megaspores are large (macro) and germinate into the FEMALE gametophyte. Microspores are small (micro) and germinate into the MALE gametophyte. In homosporous plants there is just one spore that gives one type of gametophyte (usually bisexual).
All seed plants are HETEROSPOROUS. Gymnosperms are heterosporous only (never homosporous). Angiosperms are also heterosporous. NEET 2016 marked 'Gymnosperms are both homosporous and heterosporous' as WRONG, because they are heterosporous ONLY.
Heterospory is the first step toward the SEED HABIT. In heterosporous plants the megaspore grows into a female gametophyte that is RETAINED on the parent sporophyte, and the young embryo develops inside it. This retention is first seen in pteridophytes and leads to seed formation in gymnosperms and angiosperms.
Homosporous plants usually make a single bisexual gametophyte (it bears both antheridia and archegonia). Heterosporous plants have separate male and female gametophytes because the two spore types germinate separately. So spore type also decides gametophyte sex separation.
Genera like Selaginella and Salvinia produce two kinds of spores. Such plants are known as:
Identify the pair of heterosporous pteridophytes among the following:
Select the mismatch:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
No. Most pteridophytes are homosporous, but two genera, Selaginella and Salvinia, are heterosporous. So the group has both types, but only these two are the heterosporous exceptions to remember for NEET.
Megaspore is large and forms the female gametophyte; microspore is small and forms the male gametophyte. Both exist only in heterosporous plants.
Salvinia is heterosporous. NEET 2017 marked 'Salvinia – Heterosporous' as correct. Watch out: NEET 2017 also tried to trick students by calling Salvinia homosporous in a wrong statement, so lock in that Salvinia is heterosporous.
Bryophytes (mosses, liverworts) are homosporous. Heterospory clearly appears in the two pteridophytes Selaginella and Salvinia and then in all seed plants (gymnosperms and angiosperms).
In heterosporous plants the megaspore forms a female gametophyte that stays on the parent plant, and the embryo develops inside it. This retention of the embryo on the parent is the early step that later became the seed in gymnosperms and angiosperms.
