Morphological and anatomical structure of achenes in the genus Prenanthes S.L. (Asteraceae)

摘要

Achenes of 11 species of the genus Prenanthes L. (incl. Nabalus Cass.) and one species of Faberia Hemsl. were studied. Several characters of their morphology and anatomy as well as surface were examined and evaluated. The diversity of achene features does not correspond to the current acceptance of Prenanthes s. str., Nabalus, Notoseris and Faberia as distinct genera. We propose to unite all these taxa into a single genus Prenanthes characterized by columnar achenes with a glabrous or slightly ribbed surface without furrows. As a rule, Prenanthes achenes have 5 main vascular bundles and 15--25 sclerenchyma strands overlaid with parenchyma. Fusion of the sclerenchyma strands sometimes may mark the rank of section. Many species have extra sclerification over the sclerenchyma strands, indicating the presence of supernumerary vascular bundles. This character is unusual for the subtribe Lactucinae Dum., to which Prenanthes is currently attributed, but common for Crepidiinae Dum. We propose to transferthe genus Prenanthes to the subtribe Crepidiinae, as supported by the plant morphology and the data of molecular studies.