Chapter 27 The Importance of Plants

Plant Cultivation Fewer than 20 plant species provide more than 90% of our food supply. Selective breeding is process by which we have most of the species of plants we grow. Cultivars have at least one distinguishing characteristic that sets them apart from other member of their species. Examples: McIntosh apples, Valencia oranges

Food Crops Classified by use and family Many crops fit into more than one category.

Cereals Grasses that contain grains (edible, dry fruits) Provide about 50% of the calories in the average human’s diet Wheat and corn are produced in the largest amounts

Root Crops Roots or underground stems that are rich in carbohydrates In many parts of the world, they substitute for cereals in providing the major part of the diet

Legumes Members of the pea family and bear seeds in pods Soybean is the most important legume crop Improve the nitrogen content of the soil

Fruits, Vegetables, Nuts Fruit - part of flowering plants that contains seeds Vegetables - foods derived from the leaves, stems, seeds, and roots of nonwoody plants Nut - dry, hard fruit that does not split open to release its seed

Spices, Herbs, Flavorings Spices - add taste to food, in general come plant parts other than the leaf and are tropical Herbs - add taste to food, come from leaves and can be grown in a home garden Flavorings -not spices or herbs

Food Production Fertilizers supply plants with nutrients Pesticides kill undesirable organisms that harm crops Both of the above have made it possible to feed the increasing number of people on the earth

Nonfood Uses of Plants Medicines - many modern ones still come from plants or were originally obtained from plants Paper, cosmetics, cork, rubber, turpentine, pesticides Clothing - most is made of cotton; others are artificial (rayon, arnel, cellulose acetate), leather enhanced by tannin Dyes - were natural plant dyes; now most dyes are manufactured from coal Fuels Fossil fuels - coal, oil, natural gas Wood Fermented grains (gasohol)

Other Uses of Plants Decorations Prevent soil erosion Reduce noise Provide animal habitat Windbreaks Shade and moderate temperatures Mental well-being, hobby, exercise Tourist attractions, festivals, etc.

Plant Ecology Study of interactions between plants and the environment Photosynthesis Soil formation Plant/animal - pollinators Plant/fungus - mycorrhizae Plant/human - weeds, diseases, etc.

Harmful Plants Addictive plant products - tobacco, cocaine, opium, alcohol Eaten or touched - poison ivy, poison oak, holly berries, mistletoe Hay fever - pollen allergy The pollen that causes allergies comes from small, drab flowers that are wind- pollinated.