chapter 29: the importance of plants 29-1 plants and people 29-2 plants and the environment

Chapter 29: The Importance of Plants

29-1 Plants and People

29-2 Plants and the Environment

I. Botany• Branch of biology dealing with the 350,000 species of plants.

29-1 Plants and People

II. Plants as Food

• Fewer than twenty plant species provide more than 90 percent of our food supply; 10,000 plant species have shown value as foods.(1) Agriculture (11,000 years ago)• Farmers propagated plants that had valuable traits, including high fruit yield.

(2) Cultivars (i.e., cultivate-variety)• Crops that evolved through artificial selection (e.g., Thompson Seedless Grapes, MacIntosh Apples, Valencia Oranges, Yoshiro Cherries.)

III. Food Crops

• Classified by use and by family but not phylogeny.

Category Description Examples

Cerealsgrasses with edible dry fruit known as grains

rice, wheat, corn, oats, rye

Root cropsroots or underground stems rich in carbohydrates

potato, sweet potato, taro

Legumesmembers of the pea family with protein-rich seeds in pods

soybean, peanut, bean, pea, alfalfa

Fruitsthe part of a flowering plant containing seeds

apple, banana, grape, orange, pineapple

Vegetablesleaves, stems, seeds, and roots of soft plants

spinach, sweet corn, tomato, turnip

Nutsa one-seed fruit with a hard outer layer

peanut, walnut, pecan, coconut, almond

Spicesplant parts other than the leaf that add taste to food

pepper, vanilla, ginger

Herbsplant leaves that add taste to food

sage, dill, basil, mint, oregano

(A) Cereals (provide 50% of the worldwide calories in the human diet) • Grasses containing grains, the edible, dry fruits of a cereal. • Rice, wheat, corn, oats, sorghum, rye and millet are all examples of cereal crops.

(B) Root Crops

• Roots or underground stems that are rich in carbohydrates.• Potatoes, beets, carrots, radishes, rutabagas, turnips, and cassava (tapioca).

(C) Legumes (mutualism with the N-fixing bacteria Rhizobum in the roots) • Members of the pea family and bear protein-rich seeds in pods.• Soybean, Alfalfa, Peanuts, and Clover.

(D) Fruits, Vegetables, and Nuts • A group of classifiable plant products consumed for nutrition.(1) Fruits• Part of the flowering plant that usually contains the seeds. (e.g., tomatoes, green beans, squash, etc…)

(2) Vegetables • Derived from the leaves, stems, seeds, and roots of non-woody plants. (e.g., spinach, celery, lettuce, carrots, etc…)(3) Nuts • Hard outer layer and a dry, one-seed fruit. (e.g., almonds, walnuts, pecans, hazelnuts, cashews, etc..)

Assortment of true and false nuts: A. Hazelnut (Corylus americana), B. Pecan (Carya illinoensis), C. Peanut (Arachis hypogea), D. Macadamia Nut (Macadamia integrifolia), E. Almond (Prunus amygdalus), F. Brazil Nut (Bertholletia excelsa), G. Chestnut (Castanea dentata), H. Kukui Nut (Aleurites molucanna), I. Water Chestnut (Trapa bicornis), J. Walnut (Juglans regia). [True nuts: A. & G.; Drupes: B., D., E., H., I. & J.; Seeds: F.; Legumes: C. Note: The pecan (B) and walnut (J) are also considered to be a true nuts by some botanists.]

(E) Spices, Herbs, and Flavorings • Spices are derived from non-leaf tropical plant parts and herbs are usually derived from leaves and can be temperate; flavorings like chocolate are placed in a separate category.(1) Quinine (a type of flavor)• Flavor derived from the bark of the cinchona tree used to make tonic water and also treat malaria.

(F) Food Production

• Massive food shortages have not occurred due to increased use of irrigation, fertilizers, pesticides, and improved cultivars.

(1) Fertilizers • Supply plants with essential minerals and nutrients like nitrogen and phosphorous.

(2) Pesticides• Chemicals designed to prevent competition for limited resources, typically with herbivorous insects.

IV. Nonfood Uses of Plants

• Include industrial, recreational, atmospheric, and medicinal forms of utilitarian value.

(A) Medicines

• Plants were our first medicines, and early plant biologists or botanists like Carolous Linnaeus, were often medical doctors.(1) Aspirin (acetylsalicylic acid)

• Derived from the bark of the white willow tree (Salix genus)

(B) Clothing and Fabric Dyes• Cotton (hairs attached to seed of cotton plant), Linen (flax plant), and artificial fabrics (rayon)—processed wood fibers, tannin (many trees) used to toughen leather products.• Dyes derived from coal, which is partially the result of fossilized plant remains.

(C) Fuels (for heat, electricity, and machine fuel)• Fossil fuels (developed countries) and wood materials (underdeveloped countries)

(1) Gasohol• Grains can be fermented into alcohol and mixed with gasoline; about 10% alcohol, can be used as a cost effective alternative to full gasoline.

(D) Other Uses of Plants

• Environment—Prevent soil erosion, reduce noise pollution, provide habitats for life, act as windbreaks, provide shade for housing.• Inspirational—the “cocklebur plant” provided an idea for Velcro when the inventor had a burr caught in his clothing.

I. Plant Ecology (interactions between plants and the environment)• Plants play a major role in the abiotic cycling of Earth’s water, oxygen, carbon dioxide, and inorganic nutrients (and also biotic roles).

29-2 Plants and the Environment

II. Plant-Animal Interactions

• Plants have evolved roles at prey, predators, and mutualistic symbionts.• Ex: Some orchid species have evolved to resemble their wasp or bee pollinators.

III. Plant-Microbe Interactions (mutualism and parasitism)• Mutualisms between nitrogen-fixing bacteria (legumes) and mycorrhizal fungi (most terrestrial plant species)

IV. Protecting Native Plants

• Human activity has changed natural plant populations by introducing foreign plant species, diseases, and animals.(1) Weeds (e.g., water hyacinth, kudzu, crabgrass, and dandelion)• Undesirable plants that often crowd out crop plants or native plant species.• Water hyacinths float on lakes and rivers, growing so rapidly and densely that they impede boats and shade underwater plants.• The introduction of a fungal disease in 1904, chestnut blight, virtually wiped out the American chestnut as a dominant forest tree in eastern USA

V. Harmful Plants

• Tobacco, cocaine, opium, poison ivy, poinsettia sap, holly berries, and American mistletoe.

(1) Hay Fever (plant allergies of small, drab flowers that are wind-pollinated)• Allergic reaction that results from pollen release of three seasons:

(1) Early Spring—Oak, Ash, Birch and Sycamore Pollen

(2) Late Spring/Early Summer—Grasses Pollen

(3) Late Summer/Early Fall—Ragweed Pollen

Revisiting Interdependence of Organisms

• Plants provide people with food, medicines, commercial materials, and oxygen.

Assessing Prior Knowledge

• Describe several plant adaptations that have been selected for by nature.• Explain how human activity may have influenced the evolution of several plant species.