Evolution of inflorescence architecture in Nymphoides (Menyanthaceae)

Species of the aquatic genus Nymphoides have distinct and highly modified inflorescence architectures in which floating leaves support aerial flowers. Three inflorescence types exist in Nymphoides, and these differ by their relative elongation of internodes and the number of flowers per node. We compared organ composition and arrangement among the three inflorescence architecture types in representative Nymphoides species and identified several orders of repeating sympodial modules that had the same positional organ arrangement in all Nymphoides examined. The three inflorescence architecture types were found to differ in development primarily by the relative elongation of internodes and/or expansion of leaves. We determined that inflorescence growth in Nymphoides proceeds by recapitulating at various positions one of three continuation axes: a rhizome, inflorescence, or floral continuation axis, all of which have sympodial, modular components. We established a developmental model that reiterated modular components of the continuation axes, and this model sufficiently reproduced the overall morphologies of all three Nymphoides inflorescence types.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Studied representative Nymphoides species from three inflorescence types. ► Sympodial growth characterizes rhizome, inflorescence, and floral axes. ► Modular recapitulation of axes throughout the plant body. ► Despite overall differences, same components in all inflorescence types.