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Wayne's Word Noteworthy Plant For Sept. 1996

The World's Largest Vegetable

Largest Vegetable Provides Pain-Relieving Steroids
And Helps Control Human Population Explosion

   1. To Be Or Not To Be A Vegetable
   2. Supermarket Botany: Vegetable Anatomy
   3. The World's Largest Vegetables
   4. Tropical Yams Named After Dioscorides
   5. Steroids That Foam In Water
   6. Cardiac Steroids That Stimulate Your Heart
   7. Contraception With Yams
   8. Steroids: The Drug Of Champions

1. To Be Or Not To Be A Vegetable

Webster's New World Dictionary (Second Edition) defines a vegetable as a plant that is eaten whole or in part, raw or cooked, generally with a main entree or in a salad but NOT AS A DESSERT. Many vegetables, such as tomatoes and pea pods are technically fruits because they develop from the ovary of a flower (following pollination and double fertilization) and they contain seeds at maturity. Seeds develop from structures called ovules inside the ovary. In order for the ovule to develop into a seed, a minute 7-celled embryo sac inside must be fertilized by two sperm. One sperm unites with the egg to form an embryo. A second sperm unites with two polar nuclei inside the endosperm mother cell to form the food-storage tissue in a seed called endosperm. The following "vegetables" are really botanical fruits, including tomatoes, okra, squash, cucumbers, bean & pea pods, peppers and egg plant. Even a corn grain is technically a fruit (called a caryopsis) because each grain develops from a separate seed-bearing ovary with a long, thread-like style. The "silk" is all the styles collectively from several hundred grains in the ear. Since they are typically eaten with a main entree (not as a dessert), all these botanical fruits are also called vegetables.

Botanical Fruits

Botanical Vegetables

Left: An assortment of botanical fruits, including orange, lemon, lime, apple, pineapple guava, banana, avocado, chayote, persimmon, red grapes, tomato and soybean pod. All of these are seed-bearing structures (ripened ovaries), although some are sterile and do not contain mature seeds. Right: An assortment of botanical vegetables, including lettuce, broccoli, red cabbage, asparagus, celery, carrot, parsley, radish, turnip, onion and leek. Although it is not a flowering plant, the mushroom could also be considered a botanical vegetable.

See A Ripe Fruit On A Mature Okra Plant

Fruit or Vegetable?

The controversy over whether a tomato is a fruit or vegetable reached the U.S. Supreme Court. A tariff law that imposed a duty on vegetables but not fruits caused the tomato's status to become a matter of legal importance. On February 4, 1887 action was brought against the collector of the port of New York to recover back duties paid under protest on tomatoes imported by the plaintiff from the West Indies, which the collector assessed under the Tariff Act of March 3, 1883. This controversy was settled in 1893 when the U.S. Supreme Court declared that the tomato was a vegetable. The Court's official interpretation was based on the popular dictionary definition which classifies a vegetable as something eaten at dinner with your main entree, but not as a dessert. The case is known as Nix v. Hedden, 149 U.S. 304 (May 10, 1893).

The tomato (Lycopersicon esculentum) is a botanical fruit. Because
the entire fruit wall or pericarp is fleshy, it is technically called a berry.

In terms of the universe, life, and the pursuit of happiness, this controversy between a fruit and a vegetable is really not that significant or important; however, you are still probably wondering what in the heck is a true botanical vegetable? A botanical vegetable may be defined as any edible "non-fruit" part of a plant. They are NOT ripened, seed-bearing ovaries formed by intimate sexual encounters between plants or between plants and insect pollinators; however, some vegetables are hybrid offspring resulting from sex between two different species, including the broccoflower (broccoli x cauliflower) and rutabaga (cabbage x turnip). In the case of the rutabaga, chloroplast DNA studies have shown that the maternal parent was the turnip. The infamous rabbage (radish x cabbage) was a dismal failure because it ended up with the roots of its cabbage mother and the leaves of its radish father. True botanical vegetables include the following edible vegetative parts of a plant:

Most of the world's botanical vegetables are produced by shrubby or herbaceous plants and vines, but there are some vegetables derived from trees. One case in point is the horseradish tree (Moringa oleifera), also called "malungay" in the Phillipines. This is a small, soft-wooded tree native to India but cultivated throughout the tropics. It is named from the pungent root that is sometimes used as a substitute for the true horseradish (Armoracia lapathifolia) of the mustard family (Brassicaceae). The young, tender, mustard-favored leaves are eaten raw in salads and cooked as a tasty potherb. The cooked leaves are also placed in soups and curries. The long beanlike pods (fruits) of this tree are also used in soups and curries.

Two relatives of the horseradish tree: Moringa drouhardii (left) and M. stenopetala (right). Like the horseradish tree (M. oleifera), both species have long, beanlike pods. Unlike the horseradish tree, these two species have large, water-storage trunks and are adapted to hot, arid regions.

Horseradish tree (Moringa oleifera), also called "malungay" in the Phillipines and "malamgal" is some Asian markets. This is a small, soft-wooded tree native to India but cultivated throughout the tropics. The young, tender, mustard-favored leaves are eaten raw in salads and cooked as a tasty potherb. The cooked leaves are also placed in soups and curries.

2. Supermarket Botany: The Anatomy Of Vegetables

Look Up Specific Vegetables Alphabetically In Index

1. Roots & Storage Roots: Beets, radish, rabbage?, rutabaga, turnip, horse radish, jicama, salsify, sweet potato, parsnip, and cassava (tapioca).

2. Leaves & Leafy Heads: Swiss chard, spinach (actually smoked in a pipe by "Pop-eye"), lamb's quarters, water cress, cabbage, kale, collards, turnip greens, lettuce, parsley, brussels sprouts, and endive.

3. Immature Flower Cluster (Inflorescence) & Stalk (Peduncle): Broccoli, cauliflower and the hybrid broccoflower.

4. Sunflower Head (incl. Phyllaries & Receptacle): Artichoke.

5. Stem: Bamboo shoots, kohlrabi and asparagus.

6. Tuber (Modified Stem): Potato, jerusalem artichoke, true yams (Dioscorea).

7. Bulb (Modified Stem): Onion, garlic and chives.

8. Corm (Modified Stem): Taro, dasheen, and water chestnut

9. Rhizome (Underground Stem): Ginger.

10. Leaf Stalk (Petiole): Rhubarb, celery & sweet fennel.

11. Entire Plant Bodies: In Thailand called Khai-nam or "water-eggs" from the minute duckweed (Wolffia globosa). A high protein dip.

You Can Probably Think Of
Many Other Vegetables!

3. The World's Largest Vegetables

So if you exclude massive squash and pumpkins from the vegetable class, what is the world's largest vegetable? This title should be limited to vegetables in a typical human diet--because to Australian koalas, the largest vegetable would most certainly be an enormous eucalyptus tree. The 1985 Guinness Book Of World Records (UK Edition) lists some of the record-breaking vegetables, including a 35 pound (16 kg) turnip, a 45 pound (20 kg) red cabbage, a 28 pound (13 kg) broccoli, a 52 pound (24 kg) cauliflower, a 25 pound (11 kg) lettuce, and a remarkable 124 pound (56 kg) cabbage six feet (1.8 m) in diameter. Although this giant cabbage cited in the Guinness Book seems unbeatable for the title of "World's Largest Vegetable," there are tropical yams belonging to the genus Dioscorea that may be 6 to 9 feet long (2-3 m) and weigh 150 pounds (68 kg) or more, although they are usually harvested at about 2-6 pounds. These yams are not to be confused with fleshy storage roots of red sweet potatoes (Ipomoea batatas) of the Morning Glory Family (Convolvulaceae) which are also called yams. True yams belong to an entirely different and unrelated plant family, the Dioscoreaceae.

It should be pointed out here that some species of giant seaweed or kelp are used for food. The overall dimensions of some of these algae (including their stipes and blades) is probably larger than most Dioscorea yams.

Yams and cassava root at the marketplace in Roseau, Dominica. Also in photo are sweet potatoes, dasheen (left), peppers, pigeon peas (Cajanus) and red sorrel (Hibiscus sabdariffa).

4. Tropical Yams Named After Dioscorides

Although rarely seen in North America, true yams (Dioscorea spp., Dioscoreaceae) are the third most important tropical "root" crop after cassava (Manihot esculenta, Euphorbiaceae) and sweet potato (Ipomoea batatas, Convolvulaceae). This is especially true in West Africa, parts of Central America and the Caribbean, the Pacific Islands, and Southeast Asia. Other important starchy "root" crops are taro and dasheen (Colocasia esculenta, Araceae), the source of Polynesian poi, arrowroot (Maranta arundinacea, Marantaceae), and achira (Canna edulis, Cannaceae). The true yam is about 20 percent starch and as a food is very similar to a potato. The generic name commemorates Dioscorides, the ancient Greek physician and naturalist (1st Century AD). Dioscorides authored the classic De Materia Medica, a five volume reference of several thousand plant drugs that was used for 15 centuries. The most commonly cultivated edible yams are D. rotundata and D. cayensis in Africa, D. alata and D. esculenta in Asia, and D. trifida in the New World, although many cultivated varieties are known. They are climbing perennial vines with shiny, heart-shaped leaves, arising from large underground stems that are technically called tubers rather than roots. Like a potato, the tubers can be propagated by planting sections containing the "eyes" or buds; however, harvesting them is a laborious task because the tubers are deeply buried. Dioscorea is a large genus with more than 600 species. An African species called elephant's foot or Hottentot's bread (D. elephantipes) produces a massive basal stem (caudex) weighing up to 700 pounds (318 kg). The above-ground part of this caudex resembles the shell of a tortoise; hence the common name of "turtleback plant." Like other caudiciform xerophytes (desert plants with enlarged basal stems), the vine relies on carbohydrates and moisture stored in its stem during extended periods of drought. During severe drought conditions the gigantic tuberous stems are eaten as famine food by Hottentots. Luckily for the Hottentots, the tuberous stems are thoroughly cooked because they contains toxic saponins that are broken down during the heating process. Although not a common vegetable, this plant would easily take the record of "World's Largest Vegetable." Another unusual African yam is the air potato (Dioscorea bulbifera). It has small or no subterranean tubers, but instead develops large, liver-shaped aerial tubers up to four pounds (2 kg) each. In New Guinea and Melanesia special ceremonial yams weighing over 120 pounds (54 kg) are grown to reflect the grower's status in the community. The yams are used for gifts and ritualized exchanges. A yam festival is held at harvesttime during which the tubers are covered by elaborate woven masks. There are reportedly yams in tropical Asia and the South Pacific that are much larger. In fact, there is one rather dubious, unconfirmed report of an enormous yam on the island of Pohnpei that was 10 feet (3 m) in length and weighed up to 1500 pounds (680 kg). Rumors have it that at least 10 people were required to carry it. REMEMBER THAT THIS RECORD IS UNSUBSTANTIATED AND MAY NOT BE TRUE.

Subterranean tuber of a true yam (Dioscorea alata), the third most important tropical root crop after cassava and sweet potatoes. The venation and shiny, heart-shaped leaves of true yams are unmistakable compared to those of sweet potatoes and other root crops.

See The Cassava Root
See The Remarkable Potato
See Sweet Potatos & Columbus

The air potato (Dioscorea bulbifera). This unusual African yam develops large, liver-shaped aerial tubers weighing up to four pounds (2 kg) each.

A Hottentot's bread (Dioscorea elephantipes) showing the characteristic heart-shaped leaves and huge caudex resembling the shell of a tortoise.

5. Steroids That Foam In Water

In addition to food, the tubers of some Mexican and Central American species of Dioscorea (including D. composita and D. floribunda) are rich in a natural steroid called diosgenin. Natural plant steroids are formed by the polymerization of 5-carbon isoprene subunits into tetracyclic triterpenoid compounds during complex metabolic pathways inside plant cells.

All steroids have the same fundamental structure of four (tetracyclic) carbon rings called the steroid backbone or steroid nucleus. The addition of different chemical groups at different places on this backbone leads to the formation of many different steroidal compounds, including the sex hormones progesterone and testosterone, the anti-inflammatory steroid cortisone, and the cardiac steroids digoxin and digitoxin. The important animal steroid, cholesterol, also has this tetracyclic backbone structure. Some of these compounds are called steroidal glycosides (or glucosides) because they also contain sugar molecules. Steroidal compounds in the Dioscoreaceae, Liliaceae and Agavaceae are also called saponins because they foam in water. In fact, some of these steroidal saponins, such as the soap lily (Chlorogalum pomeridianum, Liliaceae) were used as soap by native Americans. Steroidal saponins may irritate mucous membranes, break down red blood cells in vitro, and are especially toxic to cold-blooded animals. In fact, fresh bulbs were used to paralyze and capture fish by throwing slices of bulbs into ponds and streams, and roasted bulbs were also eaten by several tribes of California Indians. Apparently the saponins are especially toxic to respiratory organs of fish without affecting their edibility. Saponins have also been used in shampoos, foam fire extinguishers, toothpaste, and in the brewing industry as a foaming agent for the froth ("head") of beer. Commercial sources of saponins include the soapberry tree (Sapindus saponaria, Sapindaceae), soapbark tree (Quillaja saponaria, Rosaceae), and the popular bouncing bet (Saponaria officinalis, Caryphyllaceae).

6. Cardiac Steroids That Stimulate Your Heart

Cardiac glycosides (steroids with attached sugar molecules--including digoxin and digitoxin) from the European foxglove (Digitalis purpurea, Scrophulariaceae) serve as a powerful heart stimulant in humans. They prolong the relaxation phase of the heart (diastole) during which the left ventricle fills with blood. This results in a stronger ventricular contraction (systole) and greater volume of blood pumped out through the aorta. Of course, relaxing the heart so the ventricles have a chance to fill with maximum blood volume can have serious side effects--too much digitalis can cause a permanent relaxation resulting in a "flat-liner" and a one-way trip to the "happy hunting grounds."

Another fascinating story about steroidal glycosides involves the monarch butterfly. Toxic steroidal glycosides are ingested by caterpillars as they feed on milkweed plants of the genus Asclepias (Asclepiadaceae). The glycosides have no ill effects on the ravenous caterpillars and are actually stored in their bodies. Upon metamorphosis the glycosides show up in the bodies of the adult monarch butterfly--thus rendering them toxic to predatory birds. One swallow of such a butterfly is very distasteful or may cause the bird to become gravely ill--and birds quickly learn to avoid monarchs.

7. Contraception With Yams

Contraception with yams is not based on the "plug and play" principle of a diaphragm (or Windows 95!), it is based on an intricate hormonal feedback system called the menstrual cycle. The discovery of a natural steroidal precursor in tropical yams has greatly reduced the cost of synthetic steroids used in birth control pills and corticosteroids used to treat Addison's disease, asthma, arthritis, bursitis, tendinitis, dermatitis, hemorrhoids, and many other ailments. It is possible to synthesize these hormones from bile acids of cattle or extract them from excised adrenal cortexes, but such methods are time- consuming and very expensive. The most cumbersome part of the chemical synthesis of these hormones is the complex steroidal backbone. At one time it took 40 oxen to provide enough cortisone to treat one patient for one day, and in 1938 one gram of cortisone cost $100. Today the naturally- occurring diosgenin in Mexican yams can readily be converted into these valuable steroids by simply adding the appropriate chemical group to the already-present steroidal backbone. In fact, more than 60,000 tons of fresh yam tubers are imported into the United States each year for the production of birth control pills. You can also purchase extracts of yams in tablet form that supposedly prevent ovulation and provide a "natural" method of birth control; however, it would be advisable to thoroughly research these claims before trying the latter method on a mate. If in doubt--you might want to try the very effective and foolproof oral contraceptive "Not Now Dear."

8. Steroids: The Drug Of Champions

Anabolic steroids are essentially the male hormone testosterone and its synthetic derivatives. The latter were developed in the early 1930s to prevent the atrophy of muscle tissue in patients with debilitating illnesses. They were also given to burn victims and surgery patients to speed up tissue rejuvenation. Anabolic steroids entered the athletic scene in Olympic competition in the 1950s, when it was learned that Soviet weightlifters were using them to increase their muscle mass and strength.

And who could ever forget the Seoul Olympics in 1988 when sprinter Ben Johnson of Canada burst out of the starting blocks to win the 100 meter dash, leaving American Carl Lewis in the dust. Three days later the gold medal was given to Lewis because traces of stanozolol (an anabolic steroid) were found in Johnson's urine.

Although athletes have reported remarkable results with steroids, the long-term side effects can be catastrophic--including liver cancer, heart disease, and kidney damage. In addition to tissue building, the steroids can also masculinize one's body. The is particularly noticeable in woman body builders who may grow facial hair as their voice deepens and their breasts decrease in size. Although the FDA has banned most anabolic steroids except for medical use, they are not controlled substances like cocaine and heroin. They are still being smuggled into the United States from Mexico and Europe. Although they started out with Olympians who wanted an edge in their competition, the use of anabolic steroids has now spread to thousands of mediocre athletes who want to look like Mr. Universe.

A boolean search of "dioscorea + yam" using one of the fine Internet search engines (such as Altavista, Yahoo and Lycos) will lead you to a number of references on yams, including commercial sources for naturopathic extracts from the tuber. In addition to diosgenin, some species also contain a wonder drug called DHEA (dehydroenpiandrosterone), a hormone that is also secreted by adrenal glands in the human body. There is some evidence suggesting that this hormone is anti-carcinogenic, may slow down the aging process, and may control obesity. According to some studies the level of this hormone steadily drops as one ages. Whether this chemical can help us to maintain a healthy, youthful body remains to be seen. There are undoubtedly many other factors affecting the aging process.

In addition to being the world's largest botanical vegetable, true yams belong to one of the largest genera of flowering plants on earth; have probably slowed down the exponential population growth of humans more than any other plant (particularly in highly developed countries); have provided some of the most important drugs to relieve numerous painful and debilitating ailments; contain one of the most promising drugs to combat the aging process; and have provided millions of people with one of the world's most important sources of starch.

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