Morphological, anatomical and micromorphological study of Aethionema semnanense (Brassicaceae), an endemic and endangered species from Iran

Aethionema semnanense is a rare, endemic, and endangered species of Iran, belonging to the earliest-diverging lineage of the family Brassicaceae. This study provides an integrated analysis of the morphological, anatomical, and micromorphological features of this species to clarify its taxonomic position and structural adaptations. Macromorphological traits such as ovate to orbiculate leaves, bilocular boat-shaped silicules, and winged filaments were documented. Anatomical observations revealed amphistomatic leaves with differentiated palisade and spongy tissues, idioblastic crystal-bearing cells, and well-developed vascular bundles. Micromorphological examination of seed surface patterns using scanning electron microscopy (SEM) demonstrated a distinct reticulate sculpturing that clearly differs from closely related species, including A. arabicum and A. cordatum. These combined characteristics reinforce the systematic distinctness of A. semnanense and contribute to understanding structural variation and adaptive strategies among early-diverging Brassicaceae taxa. The results also provide valuable information for future taxonomic, phylogenetic, and conservation-oriented studies on the genus Aethionema.