Tuber

views updated May 29 2018

Tuber

A tuber is a swollen, underground storage organ that develops on the roots of certain species of plants. Some types of tubers are highly nutritious, mostly because of their energy content in the form of starch.

Agricultural species of plants that develop edible tubers include the white potato (Solanum tuberosum ), sweet potato (Ipomoea batatas ), tapioca or cassava (Manihot esculenta ), and yam (Dioscorea batatas).

The white potato is the most important and best-known of the agricultural tubers. The potato is a native of the Andean plateau of South America. In this species, tubers develop at the end of roots that emerge from underground stems, known as stolons. Potato tubers have stem buds known as eyes which can sprout and grow new, aboveground stems. It appears that potatoes have been cultivated by indigenous peoples of the Andean plateau for at least 6,500 years.

The varieties of potatoes that are most commonly cultivated in modern, industrial agriculture typically develop rather large tubers with white centers. However, there is a great diversity of other varieties of potatoes, especially in their native Andean range. These varieties commonly form relatively small tubers with brown, red, yellow, or purple skin, and white or darker-colored interiors.

Potato tubers are very nutritious, especially as a source of starch. However, they also contain about 2% protein and valuable minerals and vitamins, especially vitamins B and C. Interestingly, potato foliage is poisonous because of its content of a toxic alkaloid known as solanin. This chemical also occurs in green sprouts of the eyes of the tubers, which is why these should be excised and not eaten.

The potato was first discovered by Europeans in the mid-1530s when Spanish conquistadors observed its cultivation in Peru. The potato subsequently became a commonly cultivated food in Europe, initially as a food for livestock. Around the beginning of the seventeenth century, people also began to commonly eat the potato. Its high productivity and favorable nutritional qualities are believed to have been important in allowing population growth in Europe during the next several centuries. However, at the beginning of the nineteenth century a new disease of potatoes occurred. The potato blight, caused by the fungus Phytophthora infestans, became a recurrent disaster, and widespread famine resulted. In some regions such as Ireland, poor people ate little else but potatoes, and the blight caused mass starvation which to some degree was alleviated by massive immigration to North America. The potato blight is still an important disease. However, this disease is now controlled by growing resistant varieties of potatoes by managing the environment to make it less favorable to the fungus and by the use of fungicides.

See also Nightshade.

Bill Freedman

Tuber

views updated Jun 27 2018

Tuber

A tuber is a swollen, underground storage organ that develops on the roots of certain species of plants. Some types of tubers are highly nutritious, mostly because of their energy content in the form of starch.

Agricultural species of plants that develop edible tubers include the white potato (Solanum tuberosum), sweet potato (Ipomoea batatas), tapioca or cassava (Manihot esculenta), and yam (Dioscorea batatas).

The white potato is the most important and best-known of the agricultural tubers. The potato is a native of the Andean plateau of South America . In this species, tubers develop at the end of roots that emerge from underground stems, known as stolons. Potato tubers have stem buds known as "eyes" which can sprout and grow new, aboveground stems. It appears that potatoes have been cultivated by indigenous peoples of the Andean plateau for at least 6,500 years.

The varieties of potatoes that are most commonly cultivated in modern, industrial agriculture typically develop rather large tubers with white centers. However, there is a great diversity of other varieties of potatoes, especially in their native Andean range. These varieties commonly form relatively small tubers with brown, red, yellow, or purple skin, and white or darker-colored interiors.

Potato tubers are very nutritious, especially as a source of starch. However, they also contain about 2% protein and valuable minerals and vitamins, especially vitamins B and C. Interestingly, potato foliage is poisonous because of its content of a toxic alkaloid known as solanin. This chemical also occurs in green sprouts of the eyes of the tubers, which is why these should be excised and not eaten.

The potato was first discovered by Europeans in the mid-1530s when Spanish conquistadors observed its cultivation in Peru. The potato subsequently became a commonly cultivated food in Europe , initially as a food for livestock . Around the beginning of the seventeenth century, people also began to commonly eat the potato. Its high productivity and favorable nutritional qualities are believed to have been important in allowing population growth in Europe during the next several centuries. However, at the beginning of the nineteenth century a new disease of potatoes occurred. The potato blight, caused by the fungus Phytophthora infestans, became a recurrent disaster, and widespread famine resulted. In some regions such as Ireland, poor people ate little else but potatoes, and the blight caused mass starvation which to some degree was alleviated by massive immigration to North America . The potato blight is still an important disease. However, this disease is now controlled by growing resistant varieties of potatoes by managing the environment to make it less favorable to the fungus and by the use of fungicides.

See also Nightshade.

Bill Freedman

Tuber

views updated May 23 2018

Tuber (order Pezizales) A genus of fungi in which the fruit bodies occur underground. The hymenium is not exposed to the exterior, and spores appear to be dispersed by animals that eat the fruit bodies. The fruit bodies of Tuber species are edible and highly prized as truffles (T. aestivum summer truffle; T. melanosporum, Périgord or black truffle; T. uncinatum, Burgundy truffle).

tuber

views updated Jun 11 2018

tu·ber / ˈt(y)oōbər/ • n. 1. a much thickened underground part of a stem or rhizome, e.g., in the potato, serving as a food reserve and bearing buds from which new plants arise. ∎  a tuberous root, e.g., of the dahlia.2. Anat. a rounded swelling or protuberant part.

tuber

views updated Jun 27 2018

tuber A swollen underground stem or root in certain plants. It enables the plant to survive the winter or dry season and is also a means of propagation. A stem tuber, such as the potato, forms at the end of an underground stem. Each tuber represents several nodes and internodes. The following season several new plants develop from the terminal and axillary buds (eyes). Root tubers, such as those of the dahlia, are modified food-storing adventitious roots and may also give rise to new plants.

tuber

views updated May 21 2018

tuber Botanical term for underground storage organ of some plants, e.g. potato, Jerusalem artichoke, sweet potato, yam.

tuber

views updated May 23 2018

tuber A swollen stem or root that functions as an underground storage organ. Stem tubers (in potatoes, for example) often produce buds along the stem from which aerial stems arise the following season. Root tubers produce no buds, or produce buds only at the point where the tuber is attached to the stem of the plant.

tuber

views updated May 23 2018

tuber thickened portion of the underground stem of a plant. XVII. — L. tūber hump, swelling.
So tubercle small rounded projection XVI; (path.) swelling or nodule XVII. — L. tūberculum, dim. of tūber, tubercular, tuberculous XVIII. tuberculosis disease characterized by the formation of tubercles (tubercle-bacilli). XIX.

tuber

views updated May 17 2018

tuber In plants, the short, swollen, sometimes edible underground stem, modified for the storage of food, as in the potato, or as a swollen root (for example, dahlia). They enable the plant to survive an adverse season (winter or dry season), providing food for the later development of new shoots and roots.

tuber

views updated May 23 2018

tuber A swollen stem or root that functions as an underground storage organ. Stem tubers (e.g. in potatoes) often produce buds from which aerial stems arise the following season. Root tubers produce no buds, or produce buds only at the point where the tuber is attached to the stem of the plant.