| Polycnemoideae | |
|---|---|
| Nitrophila occidentalis | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Core eudicots |
| Order: | Caryophyllales |
| Family: | Amaranthaceae |
| Subfamily: | Polycnemoideae |
| Genera | |
|
3 genera, see text |
|
Polycnemoideae is a subfamily of plants in the Amaranthaceae family.
Contents |
The subfamily Polycnemoideae comprises small herbs, some species are weakly lignified and grow shrublike. The subfamily is distinguishable from all other members of Amaranthaceae by normal secondary growth. The alternate or opposite leaves are often linear or subulate. The stomata of the leaves are arranged in parallel to the midveins.
The bisexual flowers are sitting solitary in the axil of a bract and two bracteoles. The inconspicuous perianth is formed of chartaceous, scarious, white or pinkish tepals. 1-5 stamens are present with their filaments united in a short but distinct filament tube (like in Amaranthoideae subfamily). Anthers are with only one lobe and two pollen sacs (bilocular, like in Gomphrenoideae subfamily). In fruit, the tepals are never conspicuously modified.
The Polycnemoideae are distributed in the temperate regions of Eurasia (central and southern Europe, northwestern Africa, Central Asia), North America, and Australia.
The Polycnemoideae are all C3-plants. This is regarded to be a primary character.
The intrafamilial position of the Polycnemoideae has long been a matter of dispute. The taxon was recognized in 1827 as Tribus Polycnemeae within the Chenopodiaceae family by Dumortier (In Florula Belgica). Later it was treated as belonging to the Amaranthaceae family in 1849 by Moquin-Tandon (in Prodromus systematis naturalis.... Vol 13). Oskar Eberhard Ulbrich raised it to subfamilial level in 1934, again within Chenopodiaceae (in Engler & Prantl: Die natürlichen Pflanzenfamilien. Vol 16c). Today both families are included in Amaranthaceae s.l.
Phylogenetic research revealed, that the Polycnemoideae represent a basal lineage of evolution within the Amaranthaceae family.
The Polycnemoideae comprises only one tribe:
Gudrun Kadereit, Thomas Borsch, K. Weising, and Helmut Freitag (2003): Phylogeny of Amaranthaceae and Chenopodiaceae and the evolution of C4 photosynthesis. - In: Int. J. Plant Sci. 164(6): p.959–986. pdf (chapters description, distribution, photosynthesis, systematics)