Chemical Characterization of the Seed Coats of Orchids From the Subfamily Orchidaceae: A Micromorphological Approach Using FT-IR Spectroscopy

Abstract

Orchids are among the plant species facing the most severe threat of extinction worldwide. A better understanding of the morphological and chemical structures of their seeds would contribute to addressing the challenges encountered during seed germination and, consequently, developing more effective conservation strategies. This study conducted morphometric and FTIR chemical analyses on the seeds of Anacamptis morio (L.) R.M. Bateman, Pridgeon & M.W. Chase, Anacamptis sancta (L.) R.M. Bateman, Pridgeon & M.W. Chase, Neotinea maculata (Desf.) Stearn, Neotinea tridentata (Scop.) R.M. Bateman, Pridgeon & M.W. Chase, Orchis anatolica Boiss, and Orchis italica Poir. When evaluating the morphometric measurements of the seeds, it was observed that the genera showed distinct differences, while species belonging to the same genus clustered together. Parameters such as seed size, embryo size, and cavity percentage had a positive impact on this differentiation. The similarity of the analysed species' FTIR spectra confirms their belonging to the same family. However, the secondary order FTIR spectra clearly revealed variations in absorbance values, highlighting differences between genera and species. It was observed that species belonging to the orchid genus and the genus Anacamptis exhibited similarities among themselves, whereas N. tridentata showed distinct differences from other species. Principal Component Analysis (PCA) based on FTIR results further supported these findings.