Achene characteristics of some taxa of asteraceae from the northwestern mediterranean coast of Egypt

Abstract

THIS STUDY aimed to characterize the external morphology of achenes of the 74 taxa belonging to 51 genera and four subfamilies of Asteraceae from the Northwestern Mediterranean coast of Egypt. By using light microscopy, 26 quantitative and qualitative morphological characters were recorded. Among the studied taxa, achene symmetry, hairiness, surface topography, hilum position, presence or absence of pappus and pappus type were found significant diagnostic characters for delimiting the taxa. Two main groups were identified based on the presence or absence of hardened fruiting involucre. Four types and four subtypes were recognized: (1) Achene di-or trimorphic per capitulum, (2) Achene monomorphic and lacking pappus, (3) Achene monomorphic, with coroniform or auriculate pappus, (4) Achene monomorphic, with pappus. A description, photographs and identification keys were provided to assist in identification. Despite the taxonomic significance of achene exomorphology characters on the generic and specific level for the recognition of the different studied taxa of Asteraceae, no mutual link was shown between the taxonomic division of the family into subfamilies and tribes except for few cases.