Carpological features of certain Artemisia species distributed in Ukraine

The achenes’ micromorphological structure of six Artemisia species (A. absinthium, A. annua, A. argyi, A. dracunculus, A. marschalliana, and A. vulgaris) distributed in Ukraine was investigated with the aim to identify taxonomically significant carpological features for the studied species. Fruits were collected from wild plants growing in the recreation areas of Kyiv and from the plants hosted in the living collection of the M.M. Gryshko National Botanical Garden of the NAS of Ukraine. Macromorphological features were studied with a binocular microscope Stemi 2000 Carl Zeiss. The ultrastructure of the surface was studied using a scanning electron microscope JSM-6700F JEOL, in the mode of secondary electron emission. Carbon spraying was performed using vacuum thermal evaporation of the vacuum universal post VUP-5M SELMI; platinum spraying was performed with an ion-plasma etching device JFC-1600 JEOL. All investigated species have a well-expressed, true, multicellular, symmetrical, multi-row carpopodium but differ by its shape. The surface of A. annua achenes is reticulate-pitted due to the specific structure of the exocarp and the exotests located below it. Species with lobed and continuous apical rim and species without a rim around the place of attachment of the corolla were found. It was established that the primary ultrastructure of investigated fruits is caused by the shape and character of mucous cell arrangement; epidermal cells of the exocarp are mostly compressed, without clear boundaries. Mostly a thin and inconspicuous cuticle, sometimes wrinkled, with layers and small outgrowths, causes the secondary ultrastructure of these fruits. We believe that the mentioned carpological features may be used as additional criteria in combination with other features to identify studied species.