The maintenance, adoption of heterospory and germination of a single megaspore within megasporangium to produce a female gametophyte, led to the phenomenon of “seed habit”. It is a characteristic feature of the spermatophytes.
A seed consists of an embryo, stored food and a seed coat.
The seed habit is the most complex and evolutionary successful method of sexual reproduction. It is one of the most significant events in the history of terrestrial plants and was an essential change in the vascular plant’s reproductive system, which occurred approximately 390 million years ago.
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