The term tuber plants or root crops is applied to plants which produce subterranean structures that are used as human or animal foods. These perennial plants have organs which store plant nutrients. In many cases the storage organs may be a root or a modified stem, for example a swollen rhizome or corm, or a tuber such as a potato or a swollen root as in carrot or sweet potato. All these swollen underground organs are commonly spoken of as tubers
Root crops are the second most important source of carbohydrates in the worlds food, the most important being cereals. However, in the tropical world, root crops are proportionally much more important. In fact, in many tropical countries where rice is not grown, they are the staple diet. In general the protein content is low, but some, like potato and yam provide significant amounts of certain vitamins.
Sweet Potato (Ipomoea batatas)
Sweet potato is a dicotyledonous plant which belongs to the family Convolvulaceae. Amongst the approximately 50 genera and more than 1,000 species of this family, on Ipomoea batatas is a crop plant whose large, starchy, sweet tasting tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens.
This plant is an herbaceous perennial vine, bearing alternate heart-shaped or palmate lobed leaves as well as medium-sized trumpet-shaped flowers and thus are also grown as ornamental plants. The edible tuberous root is long and tapered, with a smooth skin whose colour ranges between red, purple, brown, yellow, orange and white. Its flesh ranges from white to yellow, orange and purple.
Cassava (Manihot esculenta)
Cassava or tapioca (Manihot esculenta) is a woody shrub of the Euphorbiaceaae that is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root. Tapioca is the third largest source of carbohydrates and contains significant amounts of potassium, calcium, phosphorus and vitamin C.
Tapioca is long and tapered with a firm homogenous flesh encased in a detachable rind about 1mm thick. The skin is light brown to dark reddish brown in colour and has a smooth or rough texture. Commercial varieties can be 5 to 10 cm in diameter at the top and 50 to 80 cm long. The colour of the flesh ranges from chalk white to yellowish.
However, they are poor in protein and other nutrients. In contrast tapioca leaves are a good source of protein but should be supplemented with the amino acid methionine to counter the high cyanide content.
Sengkuang (Pachyrrhizus erosus)
Sengkuang is one species in the genus Pachyrrhizus that is commonly called yam bean.
The sengkuang vine can reach a height f 4-5 metres, given suitable support. Its roots can attain length of up to 2 metres and weigh up to 20 kilograms. The roots exterioris yellowishbrown while its inside is creamy white with a crisp textile that resembles water chestnut or pear.
In contrast to the roots, the remainder of the sengkuang plant is very poisonous; the seeds contain the toxin rotenone, which is used to kill insects and stun fish.
Sengkuang is high in carbohydrates and dietary fiber. It is composed of 86-90% water, containing only trace amounts of protein and lipids. Its sweet flavour makes it a favourite ingredient in rojak and popiah.
Dioscorea alata L. is a genus of over 600 species of flower plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. Known as yams, they are important agricultural crops in the tropical regions, grown for their large tubers.
They are tuberous herbaceous perennial climbers, ranging from 2 to 12 metres in height. The leaves are spirally arranged, mostly broad and heart-shaped. The flowers are individually inconspicuous greenish yellow with six petals; they are mostly dioecious, with separate male and female plants, though a few species are monocious, with male and female flowers on the same plant. The fruit is shaped like a capsule in most species.
Many of these are toxic when fresh but they can be detoxified and consumed and are particularly important in parts of Aftrica, Asia and Oceania.
Taro (Colocasia esculenta)
Colocasia esculenta is a tropical plant grown primarily for its edible corm, a root vegetable known as taro or cocoyam. It is believed to be one of the earliest cultivated plants and is described by historians as an important crop.
Its primary use, however, is the consumption of its edible corm and leaves. In its raw state, the plant is toxic due to the presence of calcium oxalate and the presence of needle-shaped raphides in the plant cells which can cause irritation to the mouth and tongue/ However, the toxin can be destroyed and the tuber rendered palatable by cooking or by steeping in cold water overnight.
Corms of the small round variety are peeled and boiled and used in local favourites such as bubur caca. The leaves are rich in vitamins and minerals.
Serdang Endau ( Livistona endauensis)
This small to medium palmis only found in the forest of Endau-Rompin, Malaysia. the trunk is erect and slender about 20 cm in diameter, carries a crown of palmate with rather stiff segments of green leaves.
The endemic palm of Endau-Rompin is now planted in many public parks and gardens as a rare collection of palm.
Date of Issue : 23rd July 2009
Stamp Value : 30 sen (2 Designs), 50 sen (2 Designs)
Sheet Content : 20 Values
Miniature Sheet : RM3
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