Developmental and Structural Section
Sukhorukov, Alexander .
Diversification of carpological characters in the Chenopodiaceae clade (Chenopodiaceae/Amaranthaceae).
On the basis of molecular analysis the Chenopodiaceae clade is divided into six subclades with subfamily status:Chenopodioideae, Suaedoideae, Corispermoideae, Betoideae, Salicornioideae and Salsoloideae (incl. tribe Camphorosmeae). Among many features investigated in the Chenopodiaceae, so far only leaf anatomy and photosynthetic pathways have been used in determining its diversification. Fruit and seed structure should be included as additional parameters in investigating the systematics and phylogeny of the Chenopodiaceae. In total 250 of ca. 1600 representatives are involved in the study. A one- or two-layered dry pericarp consisting of undifferentiated parenchymatous cells is the most common character within Chenopodioideae, Salicornioideae, and Suaedoideae. A multi-layered parenchymatous pericarp is observed only in some members of the tribe Atripliceae (Archiatriplex-clade), Chenopodioideae (Chenopodium sanctae-clarae and related taxa from Juan-Fernandez Islands),C. macrospermum (evidently close related to Chenopodium rubrum-clade),and in the berry-like fruits of Rhagodia and Einadia now transferred into the core members of the genus Chenopodium. Within the Chenopodioideae only Axyris possesses a two-layered pericarp comprising a parenchymatous outer layer (exocarp) and a sclereid layer that occurs in at least one of two heterocarpic fruits. The division of the pericarp into parenchyma and sclerenchyma is also peculiar to Corispermoideae. The Betoideae is distinguished by the multilayered pericarp consisting of lignified cells. The most complicated fruit cover having 3-5 different carpological zones appears in Salsoloideae. The seed coat, especially its outlines and anatomical characters, seems to be most diversified in Salicornioideae (Shepherd & al., 2005). The most interesting transformations in the reproductive structures are found in the Salicornia/Sarcocornia-clade with representatives having e.g. a perianth with hydrated parenchyma and translucent fruit/seed covers. The members of the Chenopodiaceae with a simple pericarp (Chenopodioideae, Suaedoideae) often have the seed coat divided into a thick outer testa and a thin 1-3-layered inner tegmen impregnated with tannin-like substances. The same basic characters are also found in Amaranthus and related genera (Amaranthaceae s.str.). A simplification of the seedcoat layers is observed in Halimione (Atripliceae). The adherence of the pericarp to the seed coat is a usual feature in Corispermoideae and Salsoloideae, and has also sometimes evolved in Chenopodioideae and Salicornioideae. A simplified seed coat consisting of two thin undifferentiated layers is found in Corispermoideae and Salicornioideae. Such synapomorphies as multi-layered exocarp, seedcoat outgrowths, and presence of heterocarpy/heterospermy are not uncommon in various groups of families. The evolutionary reconstruction of the carpological traits is the next step in understanding the phylogeny of Chenopodiaceae.
Log in to add this item to your schedule
1 - Moscow State University, Dept. Higher Plants, Biological Faculty, Vorobyovy Gory 1/12, Moscow, N/A, 119234, Russia
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM