Salicornioideae

The Salicornioideae are a subfamily of the flowering plant family Amaranthaceae ("sensu lato", including the Chenopodiaceae). Important characters are succulent, often articulated stems, strongly reduced leaves, and flowers aggregated in thick, dense spike-shaped thyrses. These halophytic plants are distributed worldwide.
Description.
The Salicornioideae are annual or perennial herbs, subshrubs, or low shrubs. Their stems are glabrous and often apparently jointed. The alternate or opposite leaves are fleshy, glabrous, often basally connate and stem-clasping (thus forming the joints), with missing or short free leaf blades.
The spike-shaped inflorescences consist of alternate or opposite bracts, these are often connate and stem-clasping, sometimes free. In the axil of each bract, there are one to five (rarely to twelve) flowers, free or sometimes fused to each other, to the bract, and to the inflorescence axis. The flowers are usually bisexual (the lateral flowers may be unisexual). The 2-5-lobed perianth consists of two to five connate tepals. There are one or two stamens and an ovary with mostly two stigmas.
In fruiting phase, the perianth remains membranous or becomes spongy, crustaceous, or horny. The fruit wall (pericarp) may be membranous, fleshy, chartaceous, crustaceous, woody, or horny. The seed is disc-shaped, lenticular, ovoid or wedge-shaped. Its surface may be smooth, papillose, reticulate, tuberculate or longitudinally ribbed. The embryo is curved, half-annular or horseshoe-shaped, rarely only slightly curved. In most genera, the seed contains copious perisperm, but a feeding tissue is missing in "Salicornia" and "Sarcocornia".
Photosynthesis pathway.
The majority of the Salicornieae species are C3-plants. There is only one species that has developed C4-photosynthesis, "Tecticornia indica" (syn. "Halosarcia indica").
Distribution and Evolution.
Plants from the Salicornioideae are found around the world. All are halophytes, growing in coastal or inland saline habitats.
The Salicornioideae originated in Eurasia about 38-28 million years ago, during the Late Eocene/Early Oligocene, and radiated rapidly into its major lineages. "Kalidium", the "Halocnemum/Halostachys"-lineage, "Halopeplis", and the "Allenrolfea/Heterostachys"-lineage were branching off early. Later developed the "Arthrocnemum/Microcnemum"-lineage, the "Halosarcia"-lineage (with "Halosarcia", "Pachycornia", "Tecticornia", "Sclerostegia", "Tegicornia"), and the "Salicornia/Sarcocornia"-lineage. Already in the Middle Miocene, about 19-14 million years ago, all major lineages were present.
Systematics.
The taxon was first published in 1849 by Alfred Moquin-Tandon as a tribe Salicornieae within the family Chenopodiaceae. In 1934, Oskar Eberhard Ulbrich raised the taxon to subfamily level and named it Salicornioideae (in: A. Engler & K. Prantl (eds.): "Die natürlichen Pflanzenfamilien", ed. 2, Vol. 16c).
The family Chenopodiaceae is now included in Amaranthaceae s.l.
Phylogenetic research supports the monophyly of the subfamily. According to Kadereit "et al." (2006), it comprises just one tribe, the Salicornieae. Traditionally two tribes had been distinguished, Halopeplideae and Salicornieae, but these are not monophyletic.