Asclepias

From Wikipedia, the free encyclopedia - View original article

Asclepias
Asclepiascommon.JPG
Asclepias syriaca showing flowers and latex.
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Asterids
Order:Gentianales
Family:Apocynaceae
Subfamily:Asclepiadoideae
Tribe:Asclepiadeae
Subtribe:Asclepiadinae
Genus:Asclepias
L.[1]
Type species
Asclepias syriaca
L.
Species

See text.

Synonyms[1]
  • Acerates Elliott
  • Anantherix Nutt.
  • Asclepiodella Small
  • Asclepiodora A.Gray
  • Biventraria Small
  • Oxypteryx Greene
  • Podostemma Greene
  • Podostigma Elliott (probable)
  • Schizonotus A.Gray
  • Solanoa Greene
  • Trachycalymma (K.Schum.) Bullock (possible)
 
Jump to: navigation, search
"Milkweed" redirects here. For other uses, see Milkweed (disambiguation).
Asclepias
Asclepiascommon.JPG
Asclepias syriaca showing flowers and latex.
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Asterids
Order:Gentianales
Family:Apocynaceae
Subfamily:Asclepiadoideae
Tribe:Asclepiadeae
Subtribe:Asclepiadinae
Genus:Asclepias
L.[1]
Type species
Asclepias syriaca
L.
Species

See text.

Synonyms[1]
  • Acerates Elliott
  • Anantherix Nutt.
  • Asclepiodella Small
  • Asclepiodora A.Gray
  • Biventraria Small
  • Oxypteryx Greene
  • Podostemma Greene
  • Podostigma Elliott (probable)
  • Schizonotus A.Gray
  • Solanoa Greene
  • Trachycalymma (K.Schum.) Bullock (possible)
Asclepias syriaca seed pods, Baldwinsville, New York
Milkweed sprout, a few days after sowing
Chemical structure of oleandrin, one of the cardiac glycosides

Asclepias L. (1753), the milkweeds, is a genus of herbaceous perennial, dicotyledonous plants that contains over 140 known species. It previously belonged to the family Asclepiadaceae, but this is now classified as the subfamily Asclepiadoideae of the dogbane family Apocynaceae.

Milkweed is named for its milky sap, which consists of a latex containing alkaloids and several other complex compounds including cardenolides.[2] Some species are known to be toxic.

Carl Linnaeus named the genus after Asclepius, the Greek god of healing, because of the many folk-medicinal uses for the milkweed plants.

Pollination in this genus is accomplished in an unusual manner. Pollen is grouped into complex structures called pollinia (or "pollen sacs"), rather than being individual grains or tetrads, as is typical for most plants. The feet or mouthparts of flower-visiting insects such as bees, wasps and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off, assuming the insect is large enough to produce the necessary pulling force (if not, the insect may become trapped and die[3]). Pollination is effected by the reverse procedure in which one of the pollinia becomes trapped within the anther slit.

Asclepias species produce their seeds in follicles. The seeds, which are arranged in overlapping rows, bear a cluster white, silky, filament-like hairs known as the coma[4] (often referred to by other names such as pappus, "floss", "plume", or "silk"). The follicles ripen and split open, and the seeds, each carried by its coma, are blown by the wind.

They have many different flower colorations, depending on species.

Ecology[edit]

Milkweeds are an important nectar source for native bees, wasps, and other nectar-seeking insects, though non-native honey bees commonly get trapped in the stigmatic slits and die,[3][5] and a larval food source for monarch butterflies and their relatives, as well as a variety of other herbivorous insects (including numerous beetles, moths, and true bugs) specialized to feed on the plants despite their chemical defenses.

Milkweeds use three primary defenses to limit damage caused by caterpillars: hairs on the leaves, cardenolide toxins, and latex fluids. Data from a DNA study indicate that more recently evolved milkweed species use these preventative strategies less but grow faster than older species, potentially regrowing faster than caterpillars can consume them.[6]

Uses[edit]

The milkweed filaments from the coma (the "floss") are hollow and coated with wax, and have good insulation qualities. During World War II, over 5,000 t (5,500 short tons) of milkweed floss were collected in the United States as a substitute for kapok.[7][8] As of 2007, milkweed is grown commercially as a hypoallergenic filling for pillows.[9] A study of the insulative properties of various materials found that milkweed floss was outperformed by other materials in insulation, loft, and lumpiness, but scored well on various metrics when mixed with down feathers.[10]

Seeds

In the past, the high dextrose content of the nectar led to milkweed's use as a source of sweetener for Native Americans and voyageurs.

The bast fibers of some species can be used for cordage.

Milkweed latex contains about 1 to 2% latex, and was attempted as a source of natural rubber by both Germany and the United States during World War II. No record has been found of large-scale success.

Milkweed is beneficial to nearby plants, repelling some pests, especially wireworms.

Milkweed also contains cardiac glycoside poisons that inhibit animal cells from maintaining a proper K+, Ca+ concentration gradient.[citation needed] As a result, many natives of South America and Africa used arrows poisoned with these glycosides to fight and hunt more effectively. Milkweed is toxic and may cause death when animals consume 10% of their body weight in any part of the plant.[citation needed] Milkweed also causes mild dermatitis in some who come in contact with it.

The leaves of Asclepias species, and of some species formerly classified as Asclepias such as Gomphocarpus physocarpus, are the only food source for monarch butterfly larvae and other milkweed butterflies. These plants are therefore often used in butterfly gardening.[citation needed]

Species[edit]

Some Asclepias species:

Asclepias-albicans.jpgAsclepias albicansWhitestem milkweed, native to the mojave and sonoran deserts
Asclepias amplexicaulis Blue Ridge.jpgAsclepias amplexicaulisBlunt-leaved milkweed, native to central and eastern United States
Asclepias asperula - Antelope Horns.jpgAsclepias asperulaAntelope horns, native to American southwest and northern Mexico
Asclepias sp. flowers (Marshal Hedin).jpgAsclepias californicaCalifornia milkweed, native to central and southern California
Asclepias cordifolia.JPGAsclepias cordifoliaHeart-leaf milkweed, native to the Sierra Nevada and Cascade Range up to 2000 m.
Asclepiascryptoceras.jpgAsclepias cryptocerasPallid milkweed, native to the western United States.
Asclepias curassavica (Mexican Butterfly Weed) W IMG 1570.jpgAsclepias curassavicaScarlet milkweed, tropical milkweed, bloodflower, bastard ipecacuanha, native to the American tropics, introduced to other continents
Asclepiaseriocarpa.jpgAsclepias eriocarpaWoollypod milkweed, native to California, Baja California, and Nevada
Asclepias erosa 5.jpgAsclepias erosaDesert milkweed, native to California, Arizona, and Baja California
Asclepias exaltata (2985661678).jpgAsclepias exaltataPoke milkweed, native to eastern North America
Asclepias fascicularis flowers 2003-06-05.jpgAsclepias fascicularisNarrow-leaf milkweed, native to Western United States
Asclepias humistrata.jpgAsclepias humistrataSandhill milkweed, native to southeastern United States
Swamp Milkweed Asclepias incarnata Flowers Closeup 2800px.jpgAsclepias incarnataSwamp milkweed, native to wetlands of North America
Asclepias lanceolata plant.jpgAsclepias lanceolataLanceolate milkweed (Cedar Hill milkweed), native to coastal plain of eastern United States from Texas to New Jersey
Asclepias linaria.jpgAsclepias linariaPine needle milkweed, native to Mojave and Sonoran deserts
Asclepias linearisSlim milkweed
Asclepias longifolia.JPGAsclepias longifoliaLongleaf milkweed
Asclepiasmeadii.jpgAsclepias meadiiMead's milkweed, native to midwestern United States
Asclepias nyctaginifolia.jpgAsclepias nyctaginifoliaMojave milkweed, native to the American southwest
Asclepias obovataPineland milkweed
Purple Milkweed Asclepias purpurascens Head.jpgAsclepias purpurascensPurple milkweed, native to eastern, southern, and midwestern United States
Asclepias quadrifolia 001.jpgAsclepias quadrifoliaFour-leaved milkweed, native to eastern United States and Canada
BB-3386 Asclepias rubra.pngAsclepias rubraRed milkweed
Asclepias solanoana.jpegAsclepias solanoanaSerpentine milkweed, native to northern California
R27182818 milkweed img 0312.jpgAsclepias speciosaShowy milkweed, native to western United States and Canada
Asclepias subulata flowers 2.jpgAsclepias subulataRush milkweed, leafless milkweed, native to southwestern North America
Asclepias subverticillata.jpgAsclepias subverticillataHorsetail milkweed[11]
Asclepias sullivantii.jpgAsclepias sullivantiiSullivant's milkweed
Common milkweed-tracy.jpgAsclepias syriacaCommon milkweed
Butterfly Weed Asclepias tuberosa Umbel.jpgAsclepias tuberosaButterfly weed, pleurisy root
Asclepias uncialis lg.jpgAsclepias uncialisWheel milkweed
Asclepias variegata.jpgAsclepias variegataWhite milkweed
Asclepias verticillata (3197723098).jpgAsclepias verticillataWhorled milkweed
Asclepias vestitaWoolly milkweed
Asclepiasviridiflora.jpgAsclepias viridiflora
Asclepias viridis 1.jpgAsclepias viridisGreen milkweed
Asclepias welshii 1.jpgAsclepias welshiiWelsh's milkweed

Formerly placed here[edit]

Some species formerly classified under the Asclepias genus include:

References[edit]

  1. ^ a b "Taxon: Asclepias L.". Germplasm Resources Information Network. United States Department of Agriculture. 2003-03-13. Retrieved 2013-02-05. 
  2. ^ Singh, B. and Rastogi, R.P. (1970). Cardenolides-glycosides and genins. Phytochemistry 9: 315-331.
  3. ^ a b Robertson, C. (1887) Insect relations of certain asclepiads. I. Botanical Gazette 12: 207–216
  4. ^ Sacchi, C.F. (1987) Variability in dispersal ability of Common Milkweed, Asclepias syriaca, seeds, Oikos Vol. 49, pp. 191-198
  5. ^ Frost, S.W. (1965) Insects and pollinia. Ecology 46: 556–558
  6. ^ Ramanujan, Krishna (Winter 2008). "Discoveries: Milkweed evolves to shrug off predation". Northern Woodlands (Center for Northern Woodlands Education) 15 (4): 56. 
  7. ^ Hauswirth, Katherine (2008-10-26). "The Heroic Milkweed". The Christian Science Monitor. Retrieved 2014-02-14. 
  8. ^ Wykes, Gerald (2014-02-04). "A Weed Goes to War, and Michigan Provides the Ammunition". MLive Media Group. Michigan History Magazine. Retrieved 2014-02-14. 
  9. ^ Evangelista, R.L. (2007). "Milkweed seed wing removal to improve oil extraction". Industrial Crops and Products 25 (2): 210–217. doi:10.1016/j.indcrop.2006.10.002. 
  10. ^ McCullough, Elizabeth A. (April 1991). "Evaluation of Milkweed Floss as an Insulative Fill Material". Textile Research Journal 61 (4): 203–210. doi:10.1177/004051759106100403. 
  11. ^ Asclepias subverticillata (A. Gray) Vail, USDA PLANTS
  12. ^ "GRIN Species Records of Asclepias". Germplasm Resources Information Network. United States Department of Agriculture. Retrieved 2011-02-22. 

External links[edit]