Ethnobotany is the scientific study of relationships between plants and people. Agriculture and domestication of plants began in four separate areas shortly after the Holocene warming began (about 12,000 years ago).
The greatest part of our diet, in terms of weight, volume, and calories, is usually carbohydrates. Foods rich in carbohydrates come from several plant families, but the grass family Poaceae is especially important. All our cereal grains are the small fruits of grasses, each with one seed: wheat, rice, corn, oats, rye, barley, and more. The fruits of grasses are technically known as caryopses, but we call them grains, kernels, or seeds. Each has a tiny embryo (the “germ“) and a large amount of endosperm, which is almost entirely starch (amylose), which is easy to digest into its monomers, glucose. The seed coat and fruit wall together of each caryopsis are called the “bran“.
All living plant cells have proteins in the form of enzymes, microtubules, membranes, and so on, but these are present in only small amounts. Some species produce seeds rich in proteins, and the legume family Fabaceae is especially important, having beans, peas, lentils, peanuts, chickpeas, and many other foods. A protein source that has all amino acids in more or less adequate quantities for us is said to be a complete protein. Many proteins, however, are incomplete proteins. But various proteins are complementary proteins; one has adequate amounts of amino acids that the other lacks, and vice versa. Plants make omega fatty acids and other lipids that are beneficial for us, and just as important, never make cholesterol or harmful trans-fats. Much of the plant lipid in our diet comes in the form of oils. Plants supply us with vitamins and other complex nutrients. In addition, all green parts of plants must make abundant antioxidants that protect cells from dangerous oxygen free radicals produced by photosynthesis. Examples of antioxidants are vitamins C and E, carotenoids, flavonoids, and phenolic compounds. Several plant families produce particularly nutritious foods, such as the citrus family Rutaceae and the rose family Rosaceae. The nutritional value of various plant organs differs.
Herbs and spices are plants with such strong, enjoyable flavors that we use them in such small quantities they provide almost no nutrition. The strong flavors evolved as chemical defenses that deter herbivores from eating plants. Many of the flavors we enjoy are based on just a few classes of chemical compounds, such as terpenes, phenols, alkaloids, and lipids.
Many plants contain chemicals that are so toxic it would be dangerous to try even a nibble. A number of plants contain psychoactive compounds. Many beneficial drugs have been discovered in plants, but at present most are no longer extracted from plants; they are synthesized instead.
Plants excel at making bundles of fibers. From the standpoint of plant anatomy, there are two types of single-cell fibers: xylary fibers that occur in the xylem of hardwood trees and extraxylary fibers that occur anywhere except in hardwood xylem. From the textile standpoint, plant fibers are classified by the part of the plant from which they are extracted: bast fibers (also called soft fibers) occur in phloem, cortex, and bark; hard fibers are extracted from leaves; and those derived from wood are wood fibers even if they are the tracheids of conifers. Chemicals such as waxes, resins, rubber, and drying oils are obtained from plants. Plants also produce wood.
—June 2021
—August 2023
Lance Jones 