March, 2002: Southern Africa
Due to the effects of cattle grazing, land clearing, and fires, scientists
have come to realize the importance of protecting gene pools of vanishing
economically important wild plants. One of the hottest-tasting peppers
known, the habanero, may be the key to saving farmers' crops-as well as
the lives of elephants-in Africa.
 Chili Peppers. |
Chili peppers, or chilies (Capsicum sp.), were cherished by the Inca, Aztec, and Mayan civilizations. Wild-type chiltepines, which are red, pea-sized chili peppers, have grown inPeru, the Caribbean, Mexico, and the American Southwest for more than 8,000 years. Native American women rubbed chiltepine powder on their nipples to wean their babies, and the Incas burned various chilies to create an irritating smoke to deter European invaders. Chiltepines are often referred to as the "mother of all chilies" because they are among 23 wild chilies that provide the genetic basis for milder, domestic varieties of peppers. These 23 are the descendants of the first chilies-tiny red berries that grew on vines in the Amazon region and were then dispersed great distances by birds
A 2,800-acre Wild Chile Botanical Area has been established in the Coronada National Forest of Arizona. Here, scientists can study the successful wild-type populations for their resistance to disease and pests as well as for drought- and frost-tolerant genes. This information can eventually be applied to the almost 3,000 chili pepper varieties that exist today, nearly all of which are either C. frutescens or C. annuum. Many wild-type populations are still harvested and used to treat ailments ranging from indigestion to arthritis. Additionally, many varieties are used as insect and bear repellents; to deter skunks, squirrels, and deer; and even against human attackers. So why not against elephants?
In several countries in southern Africa, corn and banana crops are an open invitation to crop-raiding elephants. In Zimbabwe alone, 200 people a year are killed as a result of elephant encounters, and sometimes just as many elephants fall victim to farmers' bullets. While wildlife has raided crops for as long as humans have engaged in agriculture, such incidents have increased recently as we push deeper into forests to claim and clear more land for cultivation. Additionally, elephants have come to recognize the farms as easy targets for a good meal with minimal effort expended on their part.
Over the past seven years, a zoologist named Ferrel Loki Osborn has been experimenting with ways to use a spray made from chili pepper extract against farm-raiding elephants. A naturally occurring chemical in chili peppers called capsaicin (C18H27NO3) causes a heat sensation when it reaches nerve receptors. This heat deters mammals from grazing on chili peppers-or on crops that have been sprayed with chili pepper extract. Interestingly, birds cannot sense the heat, so they can feed freely on chili peppers, and are well suited for dispersing the seeds.
The chemical structure of capsaicin.
The first sprays Osborn developed required that the applicant get dangerously close to the elephant-and also that the wind be on the farmer's side. Eventually, Osborn constructed a flimsy fence and then draped it at regular intervals with rags dipped in a mixture of grease and capsaicin extracted from the hottest habanero peppers. Erecting such a fence around the perimeter of crops-coupled with planting items along the fence that are known to be avoided by elephants, such as thorny plants-has significantly reduced crop loss. Most recently, a research assistant named Kinos Mariba has devised a method for deterring the few brazen young males who cross the fence. He mixed habanero and tabasco peppers with elephant dung in a 2:1 proportion and made the substance into briquettes. Farmers can then burn these briquettes in small fires around their fields. The dung does not contribute to the repellent effects-it serves only as a burnable (and readily available) medium.
A chili pepper's heat is measured in Scoville units, named after the pharmacologist Wilbur Scoville in 1912. By mixing different dilutions of dried chili peppers with alcohol, sugar, and water, a panel of tasters determine at what dilution the pepper no longer burns the mouth. For example, a green pepper has zero Scoville units, a jalapeno can range from one thousand to several thousand Scoville units, and the chiltepine rates about seventy-five thousand Scoville units. The habanero peppers used by Dr. Osborn? One million Scoville units! Because of the subjectivity of this method, many scientists are now instead measuring the amount of capsaicin in peppers, but still expressing this amount in Scoville units. For people who consume chili peppers, dairy products, not water, are found to be best at neutralizing the heat.
 Some typical plants of the Solanaceae family |
Chili peppers are the fruits of plants in the Solanaceae family, commonly referred to as the deadly nightshade family because it has many poisonous members, several of which produce toxic alkaloids. Among the 90 genera and almost 3,000 species of the Solanaceae are the potato (Solanum tuberosum); ornamentals such as petunia (Petunia sp.); the tobacco plant (Nicotiana); and the notoriously poisonous plants belladonna (Atropa belladonna) and jimson weed (Datura stramonium). The Solanaceae family is widely distributed throughout tropical and temperate regions. Although the plants occur on every continent, they are particularly concentrated in Australia, Central America, and South America. The flowers are bisexual, with petals fused at the base into a corolla with anthers attached to the corolla tube.
Dr. Osborn has reason to be proud. Not only has he helped save many cash and food crops for farmers (and elephants' lives in the process), but he has also introduced another potential cash crop into the African economy-chili peppers.
References, Websites, and Further Reading
Levetin, Estelle, and Karen McMahon. 1999. Plants and Society, 2d ed. New York: McGraw-Hill Companies, pp. 275, 279-81.
Nevala, Amy E. F/M 2000. In the Southwest, a new plant reserve protects the mother of all chilies. National Wildlife, p. 14.
Revkin, Andrew C. June 20, 2000. Need elephant repellent? Try this hot pepper brew. The New York Times, Tuesday Science Section.
Simpson, B.B, and Molly C. Ogorzaly. 1995. Economic Botany: Plants in Our World, 2d ed. New York: McGraw-Hill Companies, pp. 131-35.
http://www.botany.hawaii.edu/faculty/carr/solan.htm
University of Hawai`i at Manoa, Solanaceae family page
http://www.hort.purdue.edu/rhodcv/hort410/pepper/pepper.htm
Purdue University, School of Agriculture, peppers page
Related Reading in Stern, Kingsley R. 2000. Introductory Plant Biology,
8th ed. New York: McGraw-Hill Companies.
Chapter 8: Flowers, Fruits, and Seeds
Petals, corolla, anthers, pp. 129-32
Structure of a flower, p. 130, fig. 8.5
Fruit and seed dispersal, p. 139
Chapter 16: Plant Names and Classification
Genera, species, common names, pp. 268-69
Chapter 24: Flowering Plants and Civilization
Solanaceae, deadly nightshade family, pp. 450-51
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
If you have a question or a problem about
a specific book or product, please fill out our Product
Feedback Form.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com
or let us know what you think by filling out our Site
Survey.
