Comparative micromorphology and anatomy of seeds and endocarps of selected Primulaceae and their systematic implications

Abstract

Seed and endocarp micromorphology and anatomy of 16 taxa from the genera Ardisia, Geissanthus, Stylogyne, Myrsine (Myrsinoideae), and Jacquinia (Theophrastoideae) were examined using stereo- and scanning electron microscopy and discussed in the light of the current phylogenetic framework. In all species, the ornamentation of the seed surface was reticulate, tuberculate, or tuberculate-colliculate with several differences concerning the cell outline and anticlinal cell wall boundaries. For seeds of almost all Myrsinoideae species, one-layered seed coat devoid of rhomboid or prismatic crystals was characteristic, while seeds of J. armillaris had a two-layered seed coat with prismatic crystals. The one-layered seed coat in Myrsinoideae may be considered a synapomorphy of this subfamily. The endosperm tissue in seeds of Myrsinoideae was differentiated into two types. Seeds of Ardisia and Geissanthus species were characterized by ‘pitted’ endosperm, while in seeds of Myrsine species both the ‘pitted’ endosperm and endosperm with evenly thickened cell walls were present. In seeds of Theophrastoideae, the endosperm was ‘pitted.’ Our results confirmed that the concave hilum area is characteristic of subglobose seeds of Myrsinoideae. The ruminate endosperm was present in all the examined Myrsine species, but it was absent in Ardisia crenata, Geissanthus ambiguus, and Stylogyne pauciflora seeds. Thus, the ruminate endosperm is not the feature clearly distinguishing the seeds of Myrsinoideae and Theophrastoideae. Endocarps of Myrsinoideae vary in terms of their morphology and anatomy. The variation within the primary and secondary sculpture of their inner surface and the presence of stomata in endocarps of particular species may have systematic implications.