What is heterospory? Briefly comment on its significance. Give two examples.
Heterospory is defined as the production of two distinct kinds of spores—macro (large) spores and micro (small) spores. Plants exhibiting this trait are known as heterosporous.
The megaspores and microspores germinate to give rise to female gametophytes and male gametophytes, respectively. The female gametophytes are retained on the parent sporophytes for variable periods, and the development of the zygote into a young embryo takes place within the female gametophyte. This event is considered a precursor to the seed habit, which is an important step in evolution.
Two examples of heterosporous plants are Selaginella and Salvinia.
Explanation
The answer is derived directly from the provided context which defines heterospory as the production of macro and micro spores. It highlights the significance by explaining that the retention of the female gametophyte and subsequent embryo development within it is a precursor to the seed habit. The examples, Selaginella and Salvinia, are explicitly listed in the text as heterosporous genera.