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 dietWheat 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 podsSoybean is the most important legume cropImprove the nitrogen content of the soil

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

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

Food Production

Fertilizers supply plants with nutrientsPesticides kill undesirable organisms that harm cropsBoth of the above have made it possible to feed the increasing number of people on the earth

Nonfood Uses of PlantsMedicines - many modern ones still come from plants or were originally obtained from plantsPaper, cosmetics, cork, rubber, turpentine, pesticidesClothing - most is made of cotton; others are artificial (rayon, arnel, cellulose acetate), leather enhanced by tanninDyes - were natural plant dyes; now most dyes are manufactured from coalFuels

Fossil fuels - coal, oil, natural gasWoodFermented grains (gasohol)

Other Uses of Plants

DecorationsPrevent soil erosionReduce noiseProvide animal habitatWindbreaksShade and moderate temperaturesMental well-being, hobby, exerciseTourist attractions, festivals, etc.

Plant Ecology

Study of interactions between plants and the environmentPhotosynthesisSoil formationPlant/animal - pollinatorsPlant/fungus - mycorrhizaePlant/human - weeds, diseases, etc.

Harmful Plants

Addictive plant products - tobacco, cocaine, opium, alcoholEaten or touched - poison ivy, poison oak, holly berries, mistletoeHay fever - pollen allergyThe pollen that causes allergies comes from small, drab flowers that are wind-pollinated.