Practice question

Heterospory denotes reproductive differentiation involving production of two morphologically and functionally distinct spore size classes by same sporophyte. Microspores, small and numerous produced in microsporangia, germinate into reduced male gametophytes producing spermatozoids. Megaspores, larger with stored starch, lipids and proteins, develop into female gametophytes retaining archegonia and supporting embryo growth matrotrophically. This separation improves resource allocation, outcrossing potential and early embryo provision. Selaginella, Isoetes, Marsilea, Salvinia and all seed plants exhibit heterospory; homospory produces one spore type. This structural framework illustrates phylogenetic relationships and adaptive significance highlighted in competitive examinations focusing on comparative plant morphology and systematics.