1. Introduction
Apiaceae is one of the largest and cosmopolitan plant families that distributed over the all continents. Based on molecular phylogenetic classifications, this family subdivided into five subfamilies. Of these, subfam. Apioideae is the largest clade including 380 genera and 3200 species (Steven, 2001, Calviño et al. 2016, Downie et al. 2010). Iran is a major center of diversification of this family among Asian countries (114 genera and 164 species) and even in the world that included many small and large endemic genera (Pimenov and Leovov 2004, Valiejo-Roman et al. 2006, Ajani et al. 2008, Ajani and Mozaffarian 2019, Mousavi et al. 2021).
Species of Apiaceae determined by simple or compound umbels and uniform floral formula, i.e., five reduced sepals, five petals, five stamens and two bicarpellate inferior carpels (Singh 2010, Simpson 2011). Superficially, one would expect homogenous floral morphology in this family. The features, however, are highly diverse in this family. The variation is even observable in common, well-known and economically important species like Coriandrum sativum L., and Daucus carota L. (Baczyński et al. 2022, Claßen-Bockhoff et al. 2023 unpubl.). By so far (~42 species), the ontogenetical works based on scanning electron microscopy (SEM) are continuously confirming this variations (Erbar and Leins 1985, Erbar and Leins 1997, 2004, 2010, Leins and Erbar, 2004, Ajani et al. 2016, Baczyński et al. 2021, 2022). However, the rest works since 1985 backward (Payer, 1853, 1857, Jochmann 1854, Sieler 1870, Schuchardt 1881, Schumann 1890, Jurica 1922, Borthwick et al. 1931, Sattler 1973), has performed under light microscopy and most likely need to repetition by scanning electron microscopy.
Andromonoecy is co-existence of perfect and staminate flowers (diclinous) in the same plant. Many studies have confirmed that it is promoting outcrossing. This breeding system occurs frequently in Apiaceae (Yampolsky and Yampolsky 1922, Bell 1971, Webb 1981, Schlessman et al. 1990, Koul et al. 1993, Richards 1997, Schlessman 2010, Ajani and Claβen-Bockhoff 2012, 2019, 2021). In Apiales clades, mapping the known breeding systems on molecular inferred trees has confirmed that andromonoecy has evolved independently several times in different clades (Schlessman 2010). This fact reflected by diverse distribution types of the diclinous flowers in different species. The floral sexual types usually placed close to each other within umbel whereas in genera likeFerula L., Dorema D. Don., and Prangos Lindl., they spatially separated on umbels or large units of inflorescence (Rechinger 1987, Reuther and Claßen-Bockhoff 2010, Ajani and Claßen-Bockhoff 2012, 2021).
Based on anatomical data, Liehr (1922) found the possibility of sexual transformation from staminate to perfect flowers with aging the plant. This evidence, furthermore, confirmed by removing the terminal umbel that followed by transformations in higher order umbels (Reuther and Claßen-Bockhoff 2013). The ontogentical studies in diclinous flowers of perennial andromonoecious, Astrantia major L., Dorema aucheri Boiss., and Ferula hezarlalehzarica Ajani showed the similar pattern. Only in late stages, despite initiation of ovary loculament, the ovules get inhibited in staminate flowers as small remnants (Leins and Erbar 2004, Ajani et al. 2016).
Species of Apiaceae (tribe Echinophoreae) determined by unique inflorescence architecture. Each umbellet includes rings of hardened pedicellate staminate flowers that centered on a sessile perfect flower that resembled a cage “lantern-shaped” (Rechinger 1987, Reuther and Claßen-Bockhoff 2010). The enlarged peripheral flowers with ray petals resembled the entire umbel as pseudanthia, i.e., a multi-flowered unit that looks like a single flower (Baczyński et al. 2021, 2022). Considering the unique inflorescence, this tribe has recognized early as monophyletic group using the molecular data (Downie et al. 2001, Valiejo-Roman et al. 2006, Ajani et al. 2008, Mousavi et al. 2021).
Dicyclophora persica Boiss., is an endemic species which is widely distributed in southern Iran (Mozaffarian 2007, Rechinger 1987). Beside unique “cage-like” inflorescence, center of the umbel occupied by blackish club-like organ that overtopping the umbel plane and making an intensive contrast with peripheral white ray flowers. It composed of a head that hold by a long white column (Fig. 1). Its color and even shape is highly diverse. In generic and species description, it indicated as central umbellet “umbellula centralis” (Rechinger 1987, Mozaffarian 2007). The ontogenetic processes of the umbellets and sexual floral morphs are not known.
The onotogenetic bases of andromonoecy are less studied in Apiaceae (e.g., Leins and Erbar 2004, Ajani et al. 2016). The present study particularly focused on developmental patterns of the diclinous flowers in the annual Iranian endemic Di. persica , in order to determine whether these flowers follow the same pattern. We expect that the results will present more data on development pathways of andromonoecy in the Apiaceae-Apioideae. The ontogeny of interesting unusual club-like organ, furthermore, studied to determine whether it is homologous to an umbellet or outgrowth of umbel receptacle.