Samaras Database

The data consist of pictures of samaras (Hornbeam samaras) collected during 2019 and 2020 from a single location, Iasi, Romania. All the samaras come from a small set of trees located in the garden of the University Al. I. Cuza / TU Iasi. All the samaras were collected after falling down. The primary purpose of this collection was to define and test asymmetry indices pertinent to samaras and similar objects. The asymmetry of the seedwing makes it spin as it falls, improving its dispersal by wind. The shape of the wing is important in the identification of different hornbeam species. The analysis of the shape asymmetry is useful for evaluating the annual variations, as well as the condition of the hornbeam forests. The usefulness of the database is also related to the fact that hornbeam is considered nowadays an endangered species all across Europe due to acid rains, parasites and climate change. The samaras collected for this study have been photographed together on a white background, in order to have a common reference and to preserve their relative size. An algorithm in Matlab was elaborated for the geometrical analysis of samaras. This algorithm automatically detects the 4 characteristic points (tips of the base, top and lateral wings) and then calculates the distances between them and the corresponding angles, mainly formed by the lateral wings with the samara body. The six distances between tips have also been measured by hand using a ruler, with a limited precision, up to half a millimeter. Depending on the distance at which the photo was taken and on the camera resolution, these distances are also expressed in number of pixels. Next, the distances calculated automatically by the Matlab algorithm were compared to the distances measured manually, finding a good match between the two sets of values, for most of the valid samara images in the database. The database contains at each entry the samara image, the six distances expressed both in millimeters and pixels, associated angles, and a set of specific coefficients which were defined to describe the degree of asymmetry. There is also additional information available, like the image name, date of acquisition, URL link to the original image and the processed image file. The current samara database was primarily used for defining and testing asymmetry indices. In the research work carried out on samara images, the statistical distribution of the geometrical parameters (lengths, angles) and asymmetry indices over the entire database has also been analyzed using histograms. Taking into account these aspects, the elaborated database can become a valuable and useful tool for the study and analysis of asymmetry and anisotropy properties of objects in images, especially in the botanical field. Prof. H.N. Teodorescu has initiated a research on the asymmetry in images [1], and then initiated and planned the current study, developed the theoretical background including the indices of asymmetry used in this research, collected the samaras, wrote a code as used in [1] and [2], corrected measurements, curated the data and some of the results, and contributed to the building of the database. He also wrote this synthesis and several metadata files and conceived the structure of the data collection. C. Nita took some of the samara pictures and contributed to building the database. R. Matei contributed an application for image processing, specifically the Matlab algorithm for detecting characteristic points, calculating distances and asymmetry indices. R. Luca and F. Iftene helped with the storing and web publication of the data collection. References: [1] Teodorescu, H.N., Dascalescu L., “Statistical characterization of images – Anisotropy”, 21st Conference on Applied Electronics (AE), Pilsen, Czech Republic, September 6-7, 2016, Book series: Applied Electronics, pages 269-272, 2016. [2] Teodorescu, Horia-Nicolai, Prawatya, Yo Pa Pa, Zeghloul, Thami et al., “Anisotropy of the triboelectric effects in polymeric slabs”, Tribology International, Volume: 136, pages 496-507, August 2019