Floral Development of Nelumbo nucifera (Nelumbonaceae)

Abstract

The floral development of Nelumbo nucifera was compared with that noted in previous studies of Nelumbo, Nymphaeaceae, and other basal angiosperms. Important features include developmental evidence of only two sepals, development of an androecial ring meristem, and an apocarpous gynoecium composed of ascidiate carpels that become embedded in an expanded receptacle. Secretory papillate trichomes cover the stigma and line the stylar canal. The unique apocarpous gynoecium, which lacks a conical residual floral apex, and a greatly expanded receptacle distinguish Nelumbonaceae from the Nymphaeaceae, as does the distinctive androecial ring. Nelumbo is characterized by polysymmetric floral development, with some organs originating spirally (petals) and some in simultaneous whorls (stamens and carpels). This pattern of floral development, as well as the pattern of carpel closure by secretion, is common in several paleoherbs and eudicots and indicates phylogenetic affinity between Nelumbonaceae and basal angiosperms. Because of its unique floral development and anatomy, Nelumbo appears to be an isolated member of the eudicot clade.