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Encyclopedia of Global Resources part 30

Encyclopedia of Global Resources part 30 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the U.S. Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 260 Corn Global Resources dated to 5200 b.c.e. By 3400 b.c.e. the fossil record shows a marked change in corn notably increased cob and kernel size indicating greater domestication. Fully domesticated corn which could not survive without human help had replaced the wild and other early types of corn by 700 c.e. Extensive attempts at hybridization began in the late nineteenth century but the increase in yield was usually a disappointing 10 percent or so. By 1920 researchers had turned to inbreeding hybridization programs. In these corn is self-fertilized rather than being allowed to cross-pollinate naturally. Following a complex sequence of crossing and testing different varieties the lines with the most desirable traits were put into commercial use and they often produced 25 to 30 percent gains in yield. Although these early hybrids focused on increasing the yield researchers later began to look for insect-resistant and diseaseresistant qualities as well. One of the hybridizers of the 1920 s was Henry A. Wallace founder of Pioneer Seed Company the world s largest seed company and later U.S. vice president under Franklin D. Roosevelt. By the 1950 s hybrid corn varieties were in widespread use. Obtaining Corn Corn processing takes place in one of three ways wet milling dry milling or fermentation. In wet milling corn is soaked in a weak sulfurous acid solution ground to break apart the kernel and then separated. The resulting by-products are found nearly everywhere. Dry milling is a simpler process involving the separation of the hull from the endosperm the food storage organ which is primarily starch in most corn and the germ the plant embr yo by repeated grinding and sieving. Fermentation of corn changes the starch to sugar which is then converted by yeast to alcohol. The process eventually results in ethyl alcohol or ethanol which is blended with gasoline to reduce carbon monoxide emissions acetone and other substances. Uses of Corn The types of corn still in use