Nymphaeaceae: A basal angiosperm family (ANITA grade) with a fully developed embryo

Rudimentary, broad and small linear embryos occur among members of the most primitive (basal) extant angiosperms, collectively called the ANITA grade (i.e. Amborella, Nymphaeales and Austrobaileyales). Amborella (rudimentary) and Austrobaileyales (rudimentary in Austrobaileyaceae, Illiciaceae and Schisandraceae and small linear in Trimeniaceae) have kinds of embryos that are known to be underdeveloped; consequently, they must grow inside the seed prior to radicle emergence (germination). On the other hand, it is not known if broad embryos need to grow before radicles can emerge, and whether they are underdeveloped or fully developed. Thus, we addressed the question: 'Is the broad embryo of Nymphaeales also underdeveloped?'. Although the embryo length:seed length ratios in Nymphaea Albert Greenburg, N. capensis var. zanzibariensis and N. immutabilis were 0.311, 0.349 and 0.234, respectively, embryos did not grow prior to radicle emergence. Thus, they are fully developed at seed maturity. If Amborella and Nymphaeales are equally the most basal angiosperms, as some molecular phylogenetic studies indicate, then we must conclude that the broad and rudimentary embryos are equally primitive.