Micromorphological Characterization of Astragalus chamaephaca (Fabaceae) With Observations on Pollen Viability

Abstract

Astragalus chamaephaca Freyn is a geographically restricted endemic species of Central Anatolia assigned to sect. Macrosemium Bunge. Detailed micromorphological data for this taxon have remained limited. This study provides a comprehensive account of pollen morphology, pollen viability, seed surface ornamentation, and indumentum characters based on LM and scanning electron microscopy and compares the results with published data for A. paradoxus Bunge, the second member of the section. Pollen grains are trizonocolporate, isopolar, subprolate (P/E = 1.42), with perforate ornamentation at the polar region and to microreticulate–perforate sculpture toward the equatorial region. Seed coat ornamentation is reticulate–rugulate, and seeds are oblate in lateral view. Indumentum is markedly reduced and restricted to sparsely distributed simple basifixed hairs on the calyx teeth. Comparative evaluation indicates consistent differences between the two species, particularly in leaflet morphology, legume indumentum, and seed shape, whereas pollen and seed surface characters conform to the general pattern observed in the genus. TTC staining revealed predominantly unstained pollen grains, suggesting low detectable metabolic activity in the examined dried material. While these findings do not directly reflect fertilization capacity, they provide baseline data for future reproductive studies. Overall, the combined structural evidence supports the current placement of A. chamaephaca within sect. Macrosemium.