EPOW - Ecology Picture of the Week

Sensitive Mimosa (Mimosa pudica)
Western Ghats Mountains, Kerela, India

Explanation:  Did you watch this short movie?  No, this isn't an insectivorous plant trying to eat my finger.  It's a "sensitive mimosa" that I videoed in the mountain jungles of south India.  

South India?  This plant is native to Central and South America ranging from Belize to Ecuador.  However ... it has been introduced widely throughout much of the world, especially the tropics.  In much of its introduced range, it is an invasive weed and is particularly difficult to eradicate due to its thorns, woody root, and swift growth.  

But sometimes even weeds have beneficial uses.  Traditional use of sensitive mimosa are many.  The bitter-tasting root -- which contains tannin, ash, calcium oxalate, and mimosin (an alkaloid) -- is said to be used to treat leprosy, dysentery, inflammations, asthma, blood disease, and many other ailments.  In south India, it is said to be used for jaundice, asthma, piles, and bronchial and blood disorders.  The seeds are used as a diuretic, to regenerate nerves, and other uses.  Quite an amazing and useful weed!

But why does it move when touched?  The leaves close up upon contact but also in response to heat, rain, or wind, and they droop at night.  One idea is that this protects the plant from herbivorous insects, and from excessive drying or loss of nutrients due to leaching by rainwater.  So ... the ecologist asks but cannot answer ... why don't all plants do this, if it's such a beneficial response?

As widespread as it now is, this plant also goes by a great diversity of common names.  In English, it is variously and wonderfully called sensitive mimosa, sensitive plant, bashful mimosa, humble plant, touch-me-not, action plant, live and die, shameplant, and shamebush.