Floral organogenesis of Limnocharis flava

Abstract

Besides a trimerous calyx and corolla, the mature flower exhibits a polyandric androecium and an apocarpous gynoecium consisting of a whorl of carpels. The primary pattern of the flower is completely trimerous and tetracyclic. After the inception of 3 sepals and 3 petals, 3 ant-sepalous primary androecial primordia are initiated each of which forms 3 stamens (i.e., secondary androecial primordia). Opposite these 3 groups of 3 stamen primordia, 3 groups of 3 carpels are initiated, on 3 extremely inconspicuous primary gynoecial primordia. Additional carpel primordia are formed in varying numbers between the original 3 groups. Before carpel inception, the 3 primary androecial primordia merge laterally forming an androecial ring. Additional stamen primordia arise on this ring 1st between the 3 groups of 3 stamen primordia and then in a centrifugal direction as the androecial ring broadens at the base. Eventually 4 whorls of stamens and 2 to 3 whorls of staminodia are formed secondarily on the androecial ring which arose from the primary primordia. Morphogenesis and construction of the flowers of L. flava differ from all other taxa of the Alismatales in 2 major respects: there are no stamen pairs primarily associated with the petals and the 1st formed carpel primordia do not alternate with the stamen primordia of the preceding whorl, so violating Hofmeister''s rule of alternation.