Flowering plant

Flowering plants
Scientific classification
Kingdom: Plantae Division: Magnoliophyta
Classes
Magnoliopsida (dicots) Liliopsida (monocots)

The flowering plants are one of the major groups of modern plants, comprising those whose seeds arise from structures called flowers. These are not always conspicuous, and many flowering plants are not often thought of as such. They first appeared at least 140 million years ago, during the Jurassic period, but may have diverged from the gymnosperms[?] in the earlier Triassic period.

Systematics

Flowering plants are usually treated as a division, sometimes called the Angiospermophyta or Anthophyta, but now more often called Magnoliophyta after the type genus Magnolia.

The classification of flowers has undergone considerable revision as ideas about their relationships change. That classification given by Arthur Cronquist[?] in the 1981 work An Integrated System of Classification of Flowering Plants is still used in many places, but since then many of the groups have been questioned. By now a general concensus has started to emerge about what the breakdown of the Magnoliophyta should look like, although there is still some variation. A typical version, called the Angiosperm Phylogeny Group system, can be found at the Missouri Botanical Garden (http://www.mobot.org/MOBOT/Research/APweb/welcome.html).

The main split among the flowers is between the dicotyledons and monocotyledons, called dicots and monocots for short. The name comes from the number of leaves within the seed, called cotyledons, but there are other notable differences (see how to distinguish a monocot from a dicot).

Most dicots belong to a group called the eudicots, but the dicot condition is primitive, and there are a few groups which are phylogenetically as close or closer to the monocots than to the eudicots. These comprise the following:

• Ceratophyllales (hornworts[?])
• Nymphaeales (waterlilies and kin)
• Piperales (peppers and kin)
• Aristolochiales (birthworts[?] and kin)
• Laurales (laurel trees[?] and kin)
• Canellales
• Magnoliales (magnolias and kin)

One division of the eudicots is as follows:

• Ranunculales (buttercups[?] and kin)
• Proteales
• Caryophyllales
• Saxifragales (saxifrage[?] and kin)
• Santalales
• Subclass Rosidae
  • eurosids I[?] (including Celastrales[?])
    • Malpighiales
    • Oxalidales[?]
    • Fabales (peas and kin)
    • Rosales (roses and kin)
    • Cucurbitales (gourd and kin)
    • Fagales (beech and kin)
    • eurosids I incertae sedis
  • eurosids II
    • Myrtales (myrtles[?] and kin)
    • Brassicales (mustards and kin)
    • Malvales (mallow and kin)
    • Sapindales (soapberries[?] and kin)
    • eurosids II incertae sedis
  • Geraniales
  • Rosidae incertae sedis (including Zygophyllales[?])
• Subclass Asteridae[?]
  • Cornales order. (dogwoods[?] and kin)
  • Ericales order (heath and kin) - 26 families
  • euasterids I
    • Garryales[?] - 4 families
    • Solanales (nightshades and kin) - 7 families
    • Gentianales (gentians and kin) - 4 families
    • Lamiales (mints and kin) - 20 familes + 4 genera incertae sedis
    • 3 families incertae sedis
      • Family Boraginaceae (borage[?] family)
      • Family Plocospermataceae[?]
      • Family Vahliaceae[?]
  • euasterids II
    • Aquifoliales[?] (hollies and kin) - 3 families
    • Apiales (parsley and kin) - 7 families
    • Dipsacales (teasels[?] and kin) - 7 families
    • Asterales (daisy and kin) - 13 families

And the monocots are divided as follows:

• Acorales[?] (sweet flag[?])
• Alismatales (water plantain[?] and kin)
• Arales (aroids[?])
• Liliales (lilies and kin)
• Dioscoreales (air potatoes[?] and kin)
• Asparagales (asparagus and kin)
• Pandanales[?] (screw-pines[?] and panama hat plants[?])
• Arecales (palms and kin)
• Commelinidae
  • Commelinales (spiderworts and kin)
  • Zingiberles[?] (ginger and kin)
  • Bromeliales (bromeliads and kin)
  • Typhales (cattails and kin)
  • Juncales (rushes and kin)
  • Cyperales (sedges[?])
  • Hydatellales
  • Eriocaulales (pipeworts[?] and kin)
  • Poales (grasses and kin)

Traditionally the dicots and monocots are treated as classes, formerly called the Dicotyledonae and Monocotyledonae, but now called the Magnoliopsida and Liliopsida according to the convention that classes and lower ranks must be named after type genera. In the Cronquist system, the basal dicots form a subclass, called the Magnoliidae[?]. In other systems, these are divided into one or more classes, while the eudicots are treated as a class Rosopsida or further divided.

The most common families of plants, in order of abundance, are:

1. Asteraceae (daisy family): 25,000 species
2. Orchidaceae (orchid family): 18,000
3. Fabaceae (pea family): 17,000
4. Poaceae (grass family): 9,000
5. Rubiaceae (coffee family): 7,000
6. Euphorbiaceae (spurge family): 5,000
7. Cyperaceae[?] (rush family): 4,000

Functional groups

Plants may be organized according to their growth pattern:

• Annual: live for one growing season[?]
• Biennial: live for two growing seasons
• Perennial: live for many growing seasons
  • Herbaceous (nonwoody): soft stems that die each year
  • Woody: hard stems which enable tall growth
    • Trees: single trunk, branching occurs high aboveground
    • Shrubs: no trunk, so branching occurs at ground

Plants may also be organized according to how they are used. Food plants include fruits, vegetables, herbs, and spices.

References

• Oldest Known Flowering Plants Identified By Genes (http://www.news.harvard.edu/gazette/1999/12.16/angiosperms.html), William J. Cromie, Harvard Gazette, December 16, 1999.