Floral Morphogenesis of Two Annonaceae Species

The floral morphogenesis of Saccopetalum prolificum and Annona muricata was observed by scanning electron microscope(SEM).The perianth of the two species consisted of three alternating whorls,and the inner perianth whorls of A.muricata were variable(numbering 3,5 or 7).The floral primordium of S.prolificum was initially conic.The outer perianth whorl initiated rapidly and then the middle and inner perianth whorls initiated successively.The floral primordium became hexagonal after the inner perianth whorl formed.The stamen primodia were nearly round and originated along the sides of hexagonal floral primordium spirally and centripetally,but arranged in whorls in amture buds.The initiation of carpels could not be distinguished from stamens in early stages,while it appeared chaotic towards the top of the floral apex.In the mature flower buds,both of carpels and stamens were covered by hairs which may have the function of retaining a pollination drop.