Fruit and seed evolution in angiosperms

Angiosperm fruit originates from the ovary of the flower or it develops from the ovary, besides of the carpels, other inflorescence or floral parts may be involved in fruit formation; seed originates from the ovule. Four major classes of fruits are distinguished in angiosperms, viz. multiple fruits, aggregate fruits, schizocarps and simple fruits. Multiple fruits originate from inflorescences; the aggregate fruit comes from a single flower with apocarpous, pluricarpellate and pluripistillate gynoecium; schizocarps originate only from the ovary of a single flower, when ripe can separate into fragments called mericarps; and the simple fruits either are commonly originated from the ovary of a single unipistillate unicarpellate flower or syncarpic pluricarpellate flower. The diversity of seeds is also great among angiosperms, with bitegmic or unitegmic seeds, and alate, arillate, operculate, endothelial, pachychalazal, hairy or sarcotestal seeds. Reflections on fruit evolution are, in fact, very general, selecting a few examples that are restricted to families and genera. Fruit evolution is fundamentally based on changes of gynoecium types and differentiation of the pericarp. Among the hypotheses formulated in the literature, one predicts two main lines of evolution: in the first, there must have been a progressive reduction in the number of carpels that led to monocarpy, thus giving rise to the simple follicle; the second line must have led to a syncarpy, initially a loose adnation, which may have given rise to the capsule. The literature dealing with seed evolution in angiosperm taxa is very vast, but almost always not conclusive.