The Suaedoideae are a subfamily of plants in the family

Amaranthaceae Amaranthaceae ( ) is a family of flowering plants commonly known as the amaranth family, in reference to its type genus '' Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, maki ...

(now including the former family Chenopodiaceae). These plants are characterized by well-developed leaves, which, except for the ''Bienertia'' genus, feature a central vascular bundle and numerous lateral bundles. Suaedoideae are found nearly worldwide and play a significant role in the vegetation of shorelines and salty inland habitats, particularly in arid regions. The subfamily includes both C3 and C4 plants, with C4 photosynthesis having originated independently four times within the group. Phylogenetic research divides Suaedoideae into two tribes: Bienertieae and Suaedeae.

Description

The Suaedoideae have well-developed leaves. Except for genus '' Bienertia'', the leaves show a central and many lateral vascular bundles. The leaves are neither decurrent nor amplexicaul. The inflorescences are axillary cymes. The flowers are sitting free in the axils of bracts, with lateral bracteoles. The perianth consists of 5 tepals, which are more or less fused basally. 5 stamens are present. The seed encloses a spiral embryo, mostly without any perisperm.

Distribution

The Suaedoideae have a nearly worldwide distribution. They are important members of the vegetation of shores and salty inland habitats. They are especially common in dry (arid) regions.

Photosynthesis pathway

Among the species of Suaedoideae, there are nearly equal numbers of C₃-plants and C₄-plants. During the evolution of the subfamily, the C₄-photosynthesis pathway seems to have been derived from four independent origins: two times with Kranz C₄ anatomy in ''Suaeda'' section ''Salsina'' and ''Suaeda'' section ''Schoberia''. Two independent origins of non-Kranz C₄ systems are found in ''Bienertia'' and ''Suaeda'' section ''Borszczowia''. In these plants, the photosynthesis pathways are located without spatial separation in a "single cell C₄" type.

Systematics

According to phylogenetic research by Kapralov et al. (2006), the Suaedoideae are grouped in 2 tribes: * Tribus Bienertieae Ulbr., with only one genus: ** '' Bienertia'' Bunge ex Boiss., with 3 species: *** '' Bienertia cycloptera'' Bunge ex Boiss. *** '' Bienertia sinuspersici'' Akhani *** '' Bienertia kavirense'' Akhani * Tribus Suaedeae, with only one genus: ** '' Suaeda'' Forssk. ex J.F.Gmel. (inclusive ''Alexandra'' Bunge and ''Borszczowia'' Bunge). With about 82 species, nearly worldwide. The genus can be further divided: *** subgenus ''Brezia'' (Moq.) Freitag & Schütze **** section ''Brezia'' (Moq.) Volk *** subgenus ''Suaeda'' **** section ''Alexandra'' (Bunge) Kapralow et al. **** section ''Borszczowia'' (Bunge) Freitag & Schütze **** section ''Physophora'' Iljin **** section ''Salsina'' Moq. s.l. (sensu Schütze et al.) **** section ''Schanginia'' (C.A.Meyer) Volk **** section ''Schoberia'' (C.A.Meyer) Volk **** section ''Suaeda''

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