Preliminary studies on variation in the micromorphology of the seed coat inHabenaria s.l.(Orchidaceae) and relatives

Abstract

AbstractThere are many studies on the biology, ecology and infrageneric classification of the cosmopolitan orchid genus Habenaria. However, there are few data on the seed morphology of species in this genus. The aim of this study was to analyse the seed morphology of Habenaria and related taxa (111 species in total). The species of Habenaria s.l. studied are mostly characterized by a scobiform seed, but the form of individual seed coat cells varies between and among some species. In most of the species analysed, the cell walls are arranged mostly along the main axis of a seed. The size of the embryos and the volume of seeds and embryos also varied in Habenaria. The periclinal wall of the cells in the seed coat of most of the taxa examined is smooth, but there are several species with distinct ornamentation on this wall (slanting ridges, transverse ridges, reticulate ridges). The periclinal wall could be used in taxonomic delimitations, especially when combined with additional features such as seed size, shape and arrangement of the cells in the seed coat. Although many of the morphological groups in Habenaria s.l. were included in this study, no qualitative seed characters that could be helpful in establishing an alternative infrageneric division of this taxon were previously recognized.