Floral ontogeny of Magnolia (Magnoliaceae) species provides insights into floral evolution but does not possess taxonomic value at the genus level

Abstract

Floral ontogeny can assist in understanding formation of mature floral structure and provide taxonomic and evolutionary insights at the species and genus level. In this study, floral ontogeny of Magnolia liliiflora, M. maudiae and M. figo was investigated using scanning electron microscopy. The results showed that tepal primordia of these species are initiated asynchronously in whorls, whereas stamen and carpel primordia are initiated spirally and centripetally. Variation in tepal number in M. maudiae was also observed at the early stage of differentiation. Our study demonstrates that floral ontogeny is remarkably homogenous in Magnoliaceae, and thus it cannot serve as a basis for classification at the genus or lower taxonomic levels. Nonetheless, the transition of floral development from typical spiral flowers to typical whorled flowers is of great significance for understanding evolution of angiosperm flowers.