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Monocotyledon

Monocotyledons or '''monocots''' are one of two major groups of flowering plants (angiosperms) that are traditionally recognised, the other being dicotyledons or dicots. Monocot seedlings typically have one cotyledon (seed-leaf), in contrast to the two cotyledons typical of dicots. Monocots have been recognised at various taxonomic ranks, and under various names (see below). The APG II system recognises a clade called "monocots" but does not assign it to a taxonomic rank. Monocots comprise the majority of biomass produced in agriculture. There are between 50,000 and 60,000 species within this group; according to IUCN there are 59,300 species.http://www.redlist.org/info/tables/table1 The largest family in this group (and in the flowering plants as a whole) by number of species are the orchids (family Orchidaceae), with about 20,000 species. The economically most important family in this group (and in all plant families) are the true grasses, family Poaceae (Gramineae). These include all the true grains (rice, wheat, maize, etc.), the pasture grasses, sugar cane, and the bamboos. True grasses have evolved to become highly specialised for wind pollination. Grasses produce much smaller flowers, which are gathered in highly visible plumes (inflorescences). Other economically important monocot families are the palm family (Arecaceae), banana family (Musaceae), ginger family (Zingiberaceae) and the onion family Alliaceae, which includes such ubiquitously used vegetables as onions and garlic. Many plants cultivated for their blooms are also from the monocot group, notably Lilium|lilies, daffodils, Iris (plant)|irises, amaryllis, orchids, Canna (plant)|cannas, Common Bluebell|bluebells and tulips.

Name, characters

The name monocotyledons is derived from the traditional botanical name ''Monocotyledones'', which derives from the fact that most members of this group have one cotyledon, or embryonic leaf, in their seeds. By contrast, the traditional Dicotyledons typically have two cotyledons. From a diagnostic point of view the number of cotyledons is neither a particularly handy (as they are only present for a very short period in a plant's life), nor totally reliable character. Nevertheless, monocots are a distinctive group. One of the most noticeable traits is that a monocot's flower is trimerous, with the flower parts in threes or in multiples of three. That is to say, a monocotyledon's flower typically has three, six, or nine petals. Many monocots also have leaf|leaves with parallel veins.

Morphology, compared to the (broadly defined) dicotyledons

The traditionally listed differences between monocotyledons and dicotyledons are as follows. This is a broad sketch only, not invariably applicable, as there are a number of exceptions. The differences indicated are more true for monocots versus eudicots, as per the APG II system: The family Hydatellaceae, assigned to order Poales in the APG II system, has since been recognized as being misplaced in the monocots, and instead proves to be most closely related to the water lilies, family Nymphaeaceae.

References and external links

*
- Chase MW, Soltis DE, Soltis PS, Rudall PJ, Fay MF, Hahn WJ, Sullivan S, Joseph J, Molvray M, Kores PJ, Givnish TJ, Sytsma KJ, Pires JC (2000). Higher-level systematics of the monocotyledons: An assessment of current knowledge and a new classification. In: Wilson KL, Morrison DA, eds. ''Monocots: Systematics and Evolution.''. CSIRO, Melbourne. 3–16. ISBN 0-643-06437-0
- Tree of Life Web Project: Monocotyledons * Category:Monocots|* Category:Plant taxonomy simple:Monocotyledon

Related Images

- Slice of onion, showing parallel veins in cross section

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