Seed Micromorphology of Orthosiphon spp. and Its Relatives (Lamiaceae)

The genus Orthosiphon in the Lamiaceae or Mint family is closely related to Ocimum and is economically important for medicinal and ornamental plants. Even though the leaf and flower morphology look different, but the characteristics of the seeds (nutlets) are almost the same. This study aims to determine the micromorphological character of the Orthosiphon seeds using a Scanning Electron Microscope (SEM). Observation of seeds apart from using SEM also with light microscopy on four taxa of Orthosiphon spp (Orthosiphon aristatus with pink flower, O. aristatus with white flower, O. endanghidayatae sp. nov., O. radjaampatensis sp. nov. and two taxa of Ocimum (O. canum and O. basilicum) as comparisons of their close relatives in the Lamiaceae. The largest seed size in O. aristatus with purple flowers (2727 μm x 1364 μm) was elliptic oblong and the smallest size was O. hidayatae (2182 μm x 1591 μm in the oblong shape), while the color of the seeds was from blackish brown to black. A detailed explanation of the surface of the seeds, whether or not trichomes, the characters at the end of the seed axis are described in this paper. The evolution of the main seed characters in Orthosiphon is also discussed.