Neotropical Chenopodiaceae

Description

Annual, rarely perennial herbs, subshrubs or shrubs, rarely lianas; plants dioecious, polygamous or monoecious.  Leaves simple, alternate, estipulate, entire to lobed, rarely deeply lobed. Inflorescence racemose or paniculate, cymose, bracteate; bracts transparent, membranous, white, green, red or wine coloured, subtending one or more flowers. Flowers small, hermaphrodite or rarely unisexual, usually actinomorphic, bracteolate; sepals (= tepals) usually 3-5, rarely fewer, free, scale-like or membranous; petals absent; stamens usually 3-5, opposite tepals, free, anthers 1-2-locular; ovary superior, 2(-3)-carpelate, 1-locular, placentation basal, 1 style, stigma< /A> of variable form.  Fruits dry, nutlets or transversely dehiscent capsules; seeds black, testa shiny.

Notes on delimitation

• The Chenopodiaceae is treated as part of a larger, all-encompassing family the Amaranthaceae by some authors (Giannasi et al. 1992, Cuénoud et al. 2002, APG II, 2003, Souza & Lorenzi 2005). 
• Recent molecular studies using the markers rbcL and matK resolve Amaranthaceae-Chenopodiaceae as sister to the Achatocarpaceae (Kadereit et al. 2003, Cuénoud et al. 2002) and this evidence is supported by existing morphological data.

Distribution in the Neotropics

• In the Neotropics, the Chenopodiaceae is represented largely by invasive species and some introduced, cultivated plants. The list of genera below includes the genera reported from Mexico, Central and South America, and the Caribbean.

Distinguishing characters (always present)

• Plants with alternate, simple, estipulate leaves with entire margins.
• Flowers small, several clustered in inflorescences.
• A bract and two bracteoles support a flower.
• Sepals (= tepals) present, free< /A> ; petals absent.
• Ovary superior, 2-3-carpellate; placentation basal.

Key differences from similar families

• Distinct from Amaranthaceae due to its alternate leaves, often lobed or variously divided. Differs from Achatocarpaceae because of its herbaceous (vs. woody) habit and dry (vs. succulent) fruits.

Number of genera

1. Beta L. - Beta vulgaris L. is the well known edible beetroot.
2. Chenopodium L.- a genus with a few medicinal representatives, the better known one being C. ambrosioides L., popularly known as mastruz and erva-de-Santa-Maria in Brazil: a toxic invasive plant that is reported as a treatment for many diseases.
3. Spinacia L. - Spinacia oleracea L., the popular spinach, is a good source of iron.
4. Salicornia L. - species of this genus are adapted to grow in salty marshes and lagoons.

Useful tips for generic identification

Key to genera of Neotropical Chenopodiaceae

1. Plants with swollen root … Beta
1. Plants without swollen root … 2

2. Leaves reduced, stems swollen … Salicornia
2. Leaves present, well developed ... 3

3. Leaves with crenate or deeply lobed margins ... Chenopodium
3. Leaves deltoid, with straight margins ... Spinacia

Status

• Mostly introduced, cultivated or naturalized, with some native, weedy species (Salicornia).

Important literature

APG II, 2003. An update of the Angiosperm Phylogeny group classification for the orders and families of flowering plants: APG II. Bot. J. Linn. Soc. 141(4): 399-436.

Cuénoud, P., V. Savolainen, L.W. Chatrou, M. Powell, R.J. Grayer & M.W. Chase. 2002. Molecular phylogenetics of Caryophyllales based on nuclear 18S RDNA and plastid rbcL, atpB, and matK  DNA sequences. Amer.J.of Bot. 89(1): 132-144.

Giannasi, D.E., G. Zurawski, G.H. Learn & M.T. Clegg. 1992. Evolutionary relationships of the Caryophyllidae based on comparative rbcL sequences. Syst.Bot.17:1-15.

G. Kadereit, T. Borsch, K. Weising and H. Freitag.  2003. Phylogeny of Amaranthaceae and Chenopodiaceae and the Evolution of C3 Photosynthesis. Int. J. Pl.Sci. 164: 959-986.

Müller K. & T. Borsch. 2005. Phylogenetics of Amaranthaceae based on matK/trnK sequence data - Evidence from Parsimony, Likelihood, and Bayesian analyses. Ann. Missouri Bot. Gard. 92:66-102.

Souza, V.C. & Lorenzi, H. 2005. Botânica Sistemática: guia ilustrativo para identificação das famílias de Angiospermas da flora brasileira, baseado em APG II. Nova Odessa, Brazil: Instituto Plantarum.

How to cite

Zappi, D. (2009). Neotropical Chenopodiaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Chenopodiaceae.htm.