In the1880s, Alphonse de Candolle, a Swiss botanist, published a book entitled Origin of Cultivated Plants, based on data he had gathered from many sources. He deduced that cultivated plants probably originated in areas where their wild relatives grow.
In 1916, N. I. Vavilov, a Russian botanist and geneticist, began a follow-up of de Candolle's work. During the next 20 years, he expanded on de Candolle's work and modified his conclusions. Vavilov became persuaded, as a result of his research, that most cultivated plants differ appreciably from their wild relatives. He also concluded that dispersal centers of cultivated plants are characterized by the presence of dominant genes in plant populations, with recessive genes becoming apparent toward the margins of a plant's distribution.
Vavilov recognized eight centers of diversity of cultivated plants, with some plants originating in more than one center. The centers, some of which were subdivided, are shown in Figure 24.1.
Since the 1950s, a number of major world crops have been subjected to analysis at the molecular level. These studies have provided evidence that many of the cultivated plants did not originate in Vavilov's centers. A significant number of such studies were undertaken by agricultural geneticist Jack R. Harlan and his students at the Crop Evolution Laboratory of the University of Illinois. Harlan concluded that some crops do not have centers of origin, and he revised Vavilov's concept, preferring instead to associate
Flowering Plants and Civilization 463
€co LogicaL Review
Nothing is more important to the relationship of humans to the environment than cultivated plants that provide sources of food, fiber, animal forage, and medicines. Cultivated plants have been developed in nearly all climatic regions of the earth and reflect the wide diversity of environments occupied by humans. Cultivated plants appear to have originated in six major regions: Near Eastern (e.g., wheat, carrot, apple), Chinese (e.g., soybean, cucumber, peach), African (yam, cotton, coffee), South Asian and Pacific (e.g., rice, sugar cane, citrus fruits), North American (e.g., sunflower, tobacco), and South and Central American (e.g., white or Irish potato, squash, pineapple). Plants originating in these regions are now grown throughout the world. Today's most important cultivated plants are a tiny fraction of the thousands of species used by peoples around the world; preserving the knowledge of useful plants held by traditional societies is a major challenge for this generation of botanists.
crop origins with regions. These regions are illustrated in Figure 14.2. A sampling of cultivated plants that appear to have originated in six major regions follows.
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