Development of male and female flower in Asparagus officinalis. Search for point of transition from hermaphroditic to unisexual developmental pathway

Asparagus officinalis is a dioecious plant. The flowers start to develop as hermaphrodites and later become unisexual. In female flowers the stamens degenerate, while in male flowers the ovary stops growing without degenerating. We have examined young asparagus flowers using SEM and optical microscopy in order to determine the exact moment of transition from hermaphroditic to unisexual development. We defined 13 stages of development, starting from flower primordia up to completely mature flowers and labelled them with numbers from -6 to 7. The first five stages are fully hermaphroditic: a difference between sexes becomes visible at stage — 1 when the style begins to develop in female flowers. Degeneration of stamens in female flowers starts somewhat later. At the stage of transition, some differences between sexes also appear in the bidimensional polypeptide pattern of flowers. RNase activity shows a distinct peak at this stage (in female flowers only), probably related to stamen degeneration.