Categories: Agriculture; economic botany and plant uses; food
Grains are the fruits or seedlike fruits of plants, particularly members of the grass family, Poaceae. Important cereal grain crops are all produced by annual grasses and are dry (desiccant)fruits with the ovary wall fused to the seed coat. Inside the fruit wall-seed coat covering (the bran) is a small embryo (germ) and a large amount of stored food (endosperm).
Grains were the first domesticated crops and allowed the development of all of the great early civilizations. Several factors contribute to the importance of grains in agriculture: ease of growth, storage, and preparation; high yields; and high-energy, easily digestible content (starch). The wild relatives of cereal grains all disperse their seeds by the shattering, or breaking apart, of mature fruiting stalks. Harvesting these wild species is a problem because the seeds are flung everywhere when the fruiting stalk is disturbed. Afirst step in the domestication of all grains was the elimination of shattering so that inflorescences could be harvested. For grasses, such as wheat, that produce many stems, or tillers, arising from the base of the plant, selection led to synchrony in the production of the tillers so that all the inflorescences of a plant would set fruit at the same time. For grasses, such as corn, that had a thick main stem, selection led to the elimination of secondary branches and a concentration of seeds in one or a few large inflorescences. The second half of the twentieth century saw selection for shorter stature that allows grains to grow better in tropical regions. While thirty-five species of grasses have been domesticated, only five are major crops today: wheat, rice, corn, sorghum, and barley.
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