Priyanti, Subject Matter Expert at Edumarz
Solution: Heterospory is defined as the ability of sporophytes to produce more than one kind of spore, usually of different sexes. The smaller spores are male and are called microspores while the larger spores are female and are known as megaspores. Microspores are borne on microsporangia and megaspores are borne on megasporangia. They subsequently germinate into male and female gametophytes respectively, and fertilization occurs.
Heterospory is essential for reproduction and hence survival of plant species. The male gametophyte, upon germination, release male gametes and reach female gametophyte, fusing with their egg. Zygote has to develop inside the female gametophyte, which ensures its proper maturation. This process and subsequent production of seeds is made possible due to the evolution of heterospory. It is the precursor to the seed habit, which is the most successful method from an evolutionary standpoint.
Heterospory occurs in some pteridophytes (Salvinia) and in vascular plants such as gymnosperms (ferns).