Eudicots

Categories: Angiosperms; Plantae; taxonomic groups

The eudicots, class Eudicotyledones (literally "true dicots"), are descended from a common ancestor and comprise three-quarters of all flowering plants. It is one of the two main classes of the angiosperms, the other being the monocots, or Monocotyledones.

Eudicots, the common name used for class Eudicotyledones, are the most common group of flowering plants, comprising 75 percent of all angiosperms. The other 25 percent, monocots

(Monocotyledones), are often characterized by pollen grains that have a single aperture (or line of weakness). Eudicots have pollen grains that typically possess three apertures, referred to as triaperturate pollen. Thus, there is no monocot-dicot division among the flowering plants. Whereas "monocot" remains a useful term, "dicot" does not represent a clade (a collection of organisms which have a single common ancestor) and should no longer be used. It is more useful to refer to eudicots, which represent a well-defined clade of angiosperms.

Previously, the angiosperms were divided into two major groups, traditionally recognized as classes: the dicots (short for dicotyledons, class Mag-noliopsida) and the monocots (monocotyledons, class Liliopsida). Dicots have been distinguished from monocots by several morphological (external physical) and anatomical features, but all of these were subject to exception. For example, most dicots possess two seedling leaves, or cotyledons, and typically

Eudicot (Dicot) Families Common

in North America

Common Name

Scientific Name

Acanthus family

Acanthaceae

Borage family

Boraginaceae

Buckwheat family

Polygonaceae

Buttercup family

Ranunculaceae

Cactus family

Cactaceae

Daisy family

Asteraceae

Evening primrose family

Onagraceae

Gentian family

Gentianaceae

Ginseng family

Araliaceae

Madder family

Rubiaceae

Milkweed family

Asclepiadaceae

Mint family

Lamiaceae

Mustard family

Brassicaceae

Pea family

Fabaceae

Phlox family

Polemoniaceae

Pink family

Caryophyllaceae

Pokeweed family

Phytolaccaceae

Primrose family

Primulaceae

Purslane family

Portulacaceae

Rose family

Rosaceae

Saxifrage family

Saxifragaceae

Verbena family

Verbenaceae

Violet family

Violaceae

Waterleaf family

Hydrophyllaceae

Note: For a full list of angiosperm families, see the tables that accompany the essay "Angiosperms," in volume 1.

Source: U.S. Department of Agriculture, National Plant Data Center, The PLANTS Database, Version 3.1, http:// plants.usda.gov. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Note: For a full list of angiosperm families, see the tables that accompany the essay "Angiosperms," in volume 1.

Source: U.S. Department of Agriculture, National Plant Data Center, The PLANTS Database, Version 3.1, http:// plants.usda.gov. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

have net-veined leaves; monocots, in contrast, usually have one cotyledon and leaves with parallel venation.

The monocot-dicot division was recognized as early as the nineteenth century. However, later studies of phylogeny (the evolutionary history of a group of organisms) have demonstrated that this split does not reflect the evolutionary history of an-giosperms. Phylogenetic trees (which are visual representations of the evolution of a group of organisms) showing historical relationships have been constructed based on deoxyribonucleic acid (DNA) sequences, as well as morphological, chemical, and other characteristics. These trees indicate that whereas the monocots form a clade, all dicots do not form a distinct group. The monocots appear among the groups of early-diverging (or early-evolving) lineages of angiosperms, all of which have traditionally been considered dicots. All early branches of the angiosperm phylogenetic tree, including the monocots, are best referred to informally as basal angiosperms.

Most angiosperms form a distinct clade, referred to by J. S. Doyle and C. L. Hotton as the eudicots, or true dicots. Whereas basal angiosperms are often characterized by pollen grains that have a single aperture (or line of weakness), eudicots have pollen grains that typically possess three apertures, referred to as triaperturate pollen. The eudicot clade receives strong support from analyses based on DNA sequence data. Importantly, the eudicots represent only a subset of the formerly recognized group dicots. Many basal angiosperms are traditional dicots but are not eudicots. Thus, there is no monocot-dicot split in the angiosperms. Whereas "monocot" remains a useful term, "dicot" does not represent a clade (a collection of organisms which have a single common ancestor) and should no longer be used. It is more useful to refer to eudicots, which represent a well-marked clade of flowering plants.

Was this article helpful?

0 0
Naturally Cure Erectile Dysfunction

Naturally Cure Erectile Dysfunction

Whether we like it or not, for many men it gets increasingly difficult to perform sexually as the years advance.

Get My Free Ebook


Post a comment