Morphological, Anatomical, Seed Micromorphological and Palynological Characterization of Astragalus talasseus Boiss. & Bal. (Fabaceae), Endemic to Türkiye

Abstract

Astragalus talasseus Boiss. & Bal. is a Turkish endemic species belonging to Astragalus sect. Pterophorus (Fabaceae). Despite its taxonomic importance, comprehensive information on its morphology, anatomy, seed micromorphology, and pollen characteristics is lacking. This study aims to provide the first detailed characterization of these features and to evaluate their taxonomic significance. Morphological observations were performed using a stereomicroscope. Anatomical features of the stem, rachis, and leaflets were examined by light microscopy, while the micromorphology of leaflets, seeds, and pollen grains was investigated using scanning electron microscopy (SEM). A detailed morphological description of A. talasseus is presented, along with diagnostic macro- and micromorphological characters. The species is characterized by a lax, cushion-forming, spiny habit; paripinnate leaves; numerous sessile flowers; and a stenonychioid standard. Anatomically, the stem exhibits secondary growth; the rachis contains well-developed sclerenchyma; and the leaflets are equifacial, with anomocytic and anisocytic stomata on both epidermal surfaces, accompanied by non-glandular trichomes. Pollen grains are tricolpate, prolate (P/E: 1.82), and have a microreticulate-perforate exine ornamentation. Seed micromorphological features are also documented in detail. Several diagnostic characters of the floral organs, including the wings, keel, stamens, style, and ovary, as well as legume and seed micromorphology, are reported for the first time for this species. The newly documented diagnostic characters expand the available knowledge of this endemic species and provide valuable data for species identification and future taxonomic studies of the taxonomically complex genus Astragalus.