Ncert Exercises & Solutions

Heterospory, i.e, formation of two types of spores— microspores and megasporesis a characteristic feature in the life cycle of a few members of pteridophytes and all spermatophytes. Do you think heterospory has some evolutionary significance in plant kingdom?

Heterospory is production of spores of two different sizes and sexes by the sporophytes of land plants. Two types of spores are produced by heterosporic plants.

Small spores are microspores which germinate into male gametophyte and large spores are macrospores which develop into female gametophyte.

In evolution of plants pteridophytes are intermediate between bryophytes and gymnosperms. All bryophytes are homosporous and all gymnosperms are heterosporous. This condition is advanced as sexual dimorphism result in cross fertilisation.

Primitive or earlier pteridophytes are homosporous later pteriodophytes are heterosporous e.g., Dryopteris, Pteris-homosporous Selaginella, Salvinia-heterosporous.

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