Ultrastructural features of cypselae in selected Senecio L. (Asteraceae) species

In this study, the cypsela features of eight Senecio species in Türkiye ( Senecio olympicus Boiss., S. paludosus L., S. tauricolus VA. Matthews, S. salsuginea H. Duman & Vural, S. castagneanus DC., S. fluviatilis Wallr., S. pseudo-orientalis Schischk., and S. racemosus (M. Bieb.) DC.) were investigated in detail using light microscopy (LM) and transmission electron microscopy (TEM). A very thick and darkly stained cuticle layer was observed on the epidermal cells of all the species examined. Papillae were observed only in epidermal cells of S. olympicus Boiss, and sclerenchyma cells were less developed in the cypsela. In the other seven species, well-developed sclerenchyma tissue was found along the pericarp wall in the form of a semicircle, in bundles, or around the secretory ducts. Although secretion ducts were observed along the cypsela wall in the mid-layer cells of S. olympicus , S. tauricolus , S. castagneanus , and S. fluviatilis , no secretion ducts were observed in the other four species. Although prismatic calcium oxalate crystals were observed in the intermediate (mid) layer of S. tauricolus, S. castagneanus , and S. pseudo-orientalis , no crystals were found in the other five species. Phytomelanin accumulation was found in the schizogenic spaces between the outer and intermediate layers of S. olympicus , S. paludosus , S. tauricolus , S. castagneanus , S. pseudo-orientalis , and S. racemosus , but not in S. salsuginea and S. fluviatilis .