Mimosa pudica (from Latin: pudica "shy, bashful or shrinking"; also called sensitive plant, sleepy plant and the touch-me-not) is a creeping annual or perennial herb often grown for its curiosity value: the compound leaves fold inward and droop when touched or shaken, to defend themselves from harm, and re-open a few minutes later. The species is native to South America and Central America, but is now a pantropical weed. It grows mostly in shady areas, under trees or shrubs.
The stem is erect in young plants, but becomes creeping or trailing with age. It can hang very low and become floppy. The stem is slender, branching, and sparsely to densely prickly, growing to a length of 1.5 m (5 ft).
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 in mid summer with more and more flowers as the plant gets older. 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 being 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 restrict germination.
Mimosa pudica is well known for its rapid plant movement. Like a number of other plant species, it undergoes changes in leaf orientation termed "sleep" or nyctinastic movement. The foliage closes during darkness and reopens in light. This was first studied by the French scientist Jean-Jacques d'Ortous de Mairan.
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 including potassium ions 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 Mimosoideae subfamily of the legume family, Fabaceae. 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 herbivores. Animals may be afraid of a fast moving plant and would rather 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, humble plant, shameful plant, touch-me-not, and chuimui.
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 Ghana, 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, Texas, 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 habitable by nitrogen fixing bacteria. The bacteria are able to convert atmospheric nitrogen, which plants cannot 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.
Mimosa pudica contains the toxic alkaloid mimosine, which has been found to also have antiproliferative and apoptotic effects. The extracts of Mimosa pudica immobilize the filariform larvae of Strongyloides stercoralis in less than one hour. Aqueous extracts of the roots of the plant have shown significant neutralizing effects in the lethality of the venom of the monocled cobra (Naja Kaouthia). It appears to inhibit the myotoxicity and enzyme activity of cobra venom.
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- "Mimosa pudica (PIER species info)". Retrieved 2008-03-25.
- Elmerich, Claudine; Newton, William Edward (2007). Associative and endophytic nitrogen-fixing bacteria and cyanobacterial associations. Springer. p. 30. ISBN 978-1-4020-3541-8
- "Antiproliferative effect of mimosine in ovarian cancer". Journal of Clinical Oncology. Retrieved 2010-01-13.
- Robinson RD, Williams LA, Lindo JF, Terry SI, Mansingh A (1990). "Inactivation of strongyloides stercoralis filariform larvae in vitro by six Jamaican plant extracts and three commercial anthelmintics". West Indian Medical Journal 39 (4): 213–217. PMID 2082565.
- "Journal of Ethnopharmacology : Neutralisation of lethality, myotoxicity and toxic enzymes of Naja kaouthia venom by Mimosa pudica root extracts". ScienceDirect. Retrieved 2011-07-15.
|Wikimedia Commons has media related to Mimosa pudica.|
|Wikispecies has information related to: Mimosa pudica|
- A list of notable chemical compounds found in Mimosa pudica
- View occurrences of Mimosa pudica in the Biodiversity Heritage Library
- "Sensitive Plant" page by Dr. T. Ombrello
- Fact Sheet from the Queensland (Australia) Department of Agriculture, Fisheries and Forestry
- Page about nyctinasty and leaf movement of Mimosa pudica by John Hewitson
- Youtube video: Mimosa Pudica
- Indiana.edu "Plants in motion" videos of Mimosa pudica: 1 and 2
- "Video:MIMOSA PUDICA SENSITIVE:guide de culture". Ethnoplants.com. Retrieved 2009-10-12.