FLORAL DEVELOPMENT OF DIOECIOUS STAGHORN SUMAC, RHUS-HIRTA (ANACARDIACEAE)

The organogenesis of floral development in the dioecious clonal tree s pecies Rhus hirta (Anacardiaceae) offers an excellent model system to study gender expression in dioecious plants. Pistillate and staminate flowers from developing inflorescences were collected from Grover Isla nd, located off the northern shore of Prince Edward Island, Canada. Th e developmental morphology of both floral types was studied using scan ning electron microscopy. The early stages of floral development of R. hirta are essentially the same in the two sexes. Both the stamen and carpel primordia are initiated in male and female flowers. Furthermore , the primordial sex organs on both flower types show striking similar ities in size and symmetry as well as sequence of initiation in the ea rly stages of development. During the later stages of development, the stamens in the female flowers and the gynoecium in the male flowers a bort, resulting in very different morphologies at maturity. Statistica l analyses revealed that the height of the mature gynoecium and stamen s as well as the length of the petals differed significantly between s exes. This species may be reflecting its relationship to hermaphroditi c ancestors during the early stages of development.