Yam (vegetable) – Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Yam_(vegetable)

Yam is the common name for some plant species in the genus Dioscorea (family Dioscoreaceae) that form edible tubers. Although some varieties of sweet potato (Ipomoea batatas) are also called yam in parts of the United States and Canada, it is not part of the family Dioscoreaceae but belongs in the unrelated morning glory family Convolvulaceae.

Differences between true yam and sweet potato "yam"

Yams are a monocot (a plant having one embryonic seed leaf) and from the Dioscoreaceae family. Sweet Potatoes are a dicot (a plant having two embryonic seed leaves) and are from the Convolvulacea family. They are therefore about as distant as two flowering plants can be. Culinarily, yams are starchier and drier than sweet potatoes. The table below lists some differences between yam and sweet potato.[2]

Factor Sweet Potato Yam
Plant Family Morning glory Yam
Chromosomes 2n=90 2n=20
Flower Monoecious Dioecious
Origin Tropical America (Peru, Ecuador) West Africa, Asia
Edible part Storage root Tuber
Appearance Smooth, with thin skin Rough, scaly
Shape Short, blocky, tapered ends Long, cylindrical, some with "toes"
Mouth feel Moist Dry
Taste Sweet Starchy
Beta carotene Usually high Usually very low
Propagation Transplants/vine cuttings Tuber pieces

Yam tubers can grow up to 1.5 meters (4.9 feet) in length[3] and weigh up to 70 kilograms (154 lb) and 3 to 6 inches high. The vegetable has a rough skin which is difficult to peel, but which softens after heating. The skins vary in color from dark brown to light pink. The majority of the vegetable is composed of a much softer substance known as the "meat". This substance ranges in color from white or yellow to purple or pink in mature yams.

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