The ontogeny of flowers and inflorescences in the andromonoecious annual Iranian endemic Dicyclophora persica (Apiaceae)

Abstract

Species of Apiaceae, despite uniform floral structure, show great variation in floral morphs and sexual distribution. In the present study, the ontogeny of the diclinous flowers within the cage‐shaped inflorescences of the andromonoecious Dicyclophora persica Boiss. was studied using scanning electron microscopy (SEM), to determine if they follow the same ontogenetic processes. The development of an interesting, unusual club‐like organ in the center of the umbel was also studied. Our findings show that the floral organs in diclinous flowers follow the same pattern. Petals initiate in a clockwise direction, while stamens form in a helical pattern. The perfect central sessile flower in the umbellet, despite sepal suppression, was synchronized with inner staminate flowers in the initiation of petals, stamens, and carpels. In staminate flowers, two prominent sepals initiate after the inception of the stamens. Ovules only get aborted in the late stages. The club‐like organ initiates from a naked receptacle that has no resemblances to umbellets or flowers. In perfect flowers, the delayed initiation and prolonged spatial constraints are caused by bracts and massive staminate flowers which suppress the sepals and make them sessile. Considering the ovule suppression, staminate flowers may be adapted to prevent the perfect flowers from being exposed to extreme environmental conditions.