XVI International Botanical Congess

The Secamonoideae, a subfamily within the Asclepiadaceae, show a range of interesting anatomical and palynological features. In several genera and species, there is synorganisation between pollinia from the same anther (intra-staminal synorganisation), as well as synorganisation between adjacent anthers (inter-staminal organisation). Synorganisation within anthers constitute the only record of staminal synorganisation within angiosperms. Some genera belonging to the Secamonoideae show a remarkable range of growth habits ranging from erect, small bodied shrubs to scrambling and twining vines. The group therefore offers a good opportunity to analyse anatomical changes and to correlate them with changes in growth habit. Genera in which such changes can be observed from shrubs to climbers or vice-versa, are usually large tropical genera with different ecological requirement and wide distribution. In those general of Secamonoideae there are only a few species with restricted distribution. Anatomical investigations together with palynological observations provide an enlarged data set for a morphological phylogenetic analysis and all changes can be compared closely with an existing phylogeny from the plastid gene matK. This will help towards a better understanding of the phylogeny of the Apocynaceae s.l.