Seed morphometry and ultrastructure studies on some Turkish orchids (Orchidaceae)

Abstract

Orchid seeds have great morphological variations that imply the phylogenetic relationship of the species depending on the biodiversity of the family or act as an adaptation to seed dispersal mechanisms depending on the life form. This study aims to both describe and analyse the qualitative and quantitative traits of 12 Turkish orchids representing epidendroids and orchidoids in detail to investigate which properties are diagnostic among these taxa and also reveal if seed properties are differentiated in relationship to the ecological preferences of the studied species. Both qualitative and quantitative features were determined, and measurements were obtained using light and scanning electron microscopy. We applied the unweighted pair group method with arithmetic mean (UPGMA) cluster analysis and canonical discriminant analysis to the qualitative and quantitative traits. Furthermore, we analyzed the same orchid seed in correlation with ecological traits such as habitats and the elevation preferences of species. This study confirmed the usefulness of both data sets for effectively assessing the variation of orchid seeds. Although the seed characters such as the cell shape differences in the chalazal or medial region, seed sizes, cell numbers on the longitudinal axis, and periclinal wall ornamentation are taxonomically conserved, some other characteristics such as seed shape, the absence of periclinal wall ornamentation, and larger embryo size imply ecological adaptation or developmental achievement for germination. This study confirms the diagnostic value of both qualitative and quantitative seed features, which are effective in explaining the orchid seed variety.