641

Spirodela polyrhiza (L.) Schleid

Synonym	:	Spirodela atropurpurea Montandon
Family	:	Lemnaceae
Local name	:	English – Duck weed
Flowering and fruiting period	:	October-November
Distribution	:	Moist temperate and Tropical regions
Distribution in kerala	:	All Districts
Habitat	:	Ponds, lakes and waste ditches
Uses	:	The plant is capable for absorbing and storing heavy metals and toxic substances in the tissue hence recommended for bioremediation in polluted water.
Key Botanical Characters:  Floating aquatic herbs. Fronds solitary or cohering in groups of 2-5, symmetric or asymmetric,  orbicular-ovate, base obtuse, apex obtuse or rounded; nerves 5-11, conspicuous; upper side flat, smooth, green, lower side flat, red-purple. Daughter fronds budding from near the point of root-insertion in a slit in the parent frond. Roots 5-10, arising from the greatly thickened part of the frond; root cap acute. Flowers surrounded by a small open spathe in a lateral slit-pouch with 1-pistillate flower and 2-3 staminate flowers each consisting of a single stamen. . Fruit 1-2 seeded, slightly winged. Seeds smooth.