Mimosa pudica, Photo: Michael Lahanas
Mimosa pudica L.
* Species Plantarum 1:518. 1753
Mimosa pudica (Sensitive Plant) (pudica = shy), is a creeping annual or perennial herb often grown for its curiosity value: the compound leaves fold inward and droop when touched or shaken, re-opening minutes later. The species is native to South America and Central America, but is now a pantropical weed.
The leaves are bipinnately compound, with one or two pinnae pairs, and 10-26 leaflets per pinna. The petioles are also prickly. Pedunculate (stalked) pale pink or purple flower heads arise from the leaf axils. The globose to ovoid heads are 8–10 mm in diameter (excluding the stamens). On close examination, it is seen that the floret petals are red in their upper part and the filaments are pink to lavender. The fruit consists of clusters of 2-8 pods from 1–2 cm long each, these prickly on the margins. The pods break into 2-5 segments and contain pale brown seeds some 2.5 mm long. The flowers are pollinated by the wind and insects. The seeds have hard seed coats which restricts germination.
Mimosa pudica is well known for its rapid plant movement.
The leaves also close under various other stimuli, such as touching, warming, blowing, or shaking. These types of movements have been termed seismonastic movements. The movement occurs when specific regions of cells lose turgor pressure, which is the force that is applied onto the cell wall by water within the cell vacuoles and other cell contents. When the plant is disturbed, specific regions on the stems are stimulated to release chemicals which force water out of the cell vacuoles and the water diffuses out of the cells, producing a loss of cell pressure and cell collapse; this differential turgidity between different regions of cells results in the closing of the leaflets and the collapse of the leaf petiole. This characteristic is quite common within the Mimosaceae family. The stimulus can also be transmitted to neighboring leaves. It is not known exactly why Mimosa pudica evolved this trait, but many scientists think that the plant uses its ability to shrink as a defense from predators. Animals may be afraid of such a fast moving plant and would rather go and eat a less active one. Another possible explanation is that the sudden movement dislodges harmful insects.
Taxonomy and nomenclature
Mimosa pudica was first formally described by Carl Linnaeus in Species Plantarum in 1753. The species epithet, pudica, is Latin for "bashful" or "shrinking", alluding to its shrinking reaction to contact.
The species is known by numerous common names including
* sensitive plant
Mimosa pudica is native to South America and Central America. It has been introduced to many other regions and is regarded as an invasive species in Tanzania, South Asia and South East Asia and many Pacific Islands. It is regarded as invasive in parts of Australia and is a declared weed in the Northern Territory, and Western Australia although not naturalized there. Control is recommended in Queensland. It has also been introduced to Nigeria, Seychelles, Mauritius and East Asia but is not regarded as invasive in those places. In the United States of America, it grows in Florida, Hawaii, Virginia, Maryland, Puerto Rico, and the Virgin Islands.
The species can be a troublesome weed in tropical crops, particularly when fields are hand cultivated. Crops it tends to affect are corn, coconuts, tomatoes, cotton, coffee, bananas, soybeans, papaya, and sugar cane. Dry thickets may become a fire hazard. In some cases it has become a forage plant although the variety in Hawaii is reported to be toxic to livestock.
Mimosa pudica can form root nodules that are inhabitable by nitrogen fixing bacteria. The bacteria are able to convert atmospheric nitrogen, which plants can not use, into a form that plants can use. This trait is common among plants in the Fabaceae family.
In cultivation, this plant is most often grown as an indoor annual, but is also grown for groundcover. Propagation is generally by seed.
Its extract immobilizes the filariform larvae of Strongyloides stercoralis in less than one hour. In contemporary medicine, Mimosa pudica is being investigated for its potential to yield novel chemotherapeutic compounds. It contains an alkaloid called mimosine, which has been found to have potent antiproliferative and apoptotic effects.
1. ^ "Mimosa pudica information from NPGS/GRIN". www.ars-grin.gov. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?24405. Retrieved 2008-03-27.
Source: Wikispecies, Wikipedia: All text is available under the terms of the GNU Free Documentation License