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unit one Environmental, Cultural, and Social Factors That


unit one Environmental, Cultural, and Social Factors That Influence the Cultivation and Utilization of Plants 1 History, Trends, Issues, and Challenges in Plant Science – PowerPoint PPT presentation

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Title: unit one Environmental, Cultural, and Social Factors That

unit one Environmental, Cultural, and Social
Factors That Influence the Cultivation and
Utilization of Plants
1 History, Trends, Issues, and Challenges in
Plant Science 2 Terrestrial Ecosystems
Their Relationship to Cultivating
Plants  3 Growing Plants for Human Use  4
Climate  5 Soils 
After reading this chapter, you should be able to
  • Discuss why plants must be cultivated for human
  • Describe the many ways plants are needed and used
    by humans.
  • Describe how growing plants impacts our energy
    use and carbon footprint.

  • Plants are the only terrestrial organisms that
    convert inorganic carbon, oxygen, hydrogen
    nitrogen, and sulfur to organic forms, via
  • They are called autotrophs (meaning
  • Humans, and just about everything else that live
    on land are heterotrophs (or other feeders).
  • Because they feed off autotrophs or other

  • Only a small percentage of all the plant species
    in existence feed the worlds people
  • Cereal cropswheat, maize (corn), rice, barley,
    oats, sorghum, rye, millet.
  • Over half the worlds food supply come from these
  • Roots tuberspotatoes, sweet potatoes,
  • Oil cropssoybeans, corn, peanuts, palm,
    coconuts, sunflowers, olive, safflower.
  • Sugarsugar cane sugar beets.
  • Fruit cropsbananas, oranges, apples, pears, etc.
  • Vegetable cropstomatoes, lettuce, carrots,
    melons, asparagus, etc.

Common crops ranked in relation to the calories
and proteins produced per unit of land area.
Not all of the total production of food materials
is available for human consumption.
Much is lost during harvesting, transportation,
and marketing.
Some of the production is saved to be used as
seed for future plantings.
  • Adults need 2000 to 3000 kcal of energy per day,
    depending on their size and level of activity.

This energy can be provided by carbohydrates, typi
cally found in plant foods.
  • Animal fats tend to be saturated fats, which lack
    double bonds in their fatty acids.
  • Plants can make polyunsaturated fatty acids
    (PUFAs), such as linoleic and linolenic acids.
  • We use linoleic acid to make hormones like
  • Plant energy carbohydrate sources are healthy as
    they are associated with indigestible fiber,
    which protects from colon disorders.
  • Only with unrefined carbohydrates, such as whole
    wheat or brown, unpolished rice.
  • Purified carbohydrates such as refined sugar or
    starch are not as beneficial, and carry their own
    health risks.

  • A plant diet may not satisfy protein
    requirements, as it may be deficient in one or
    more amino acids.
  • Plant proteins often have a low proportion of
    essential amino acids, particularly methionine,
    and lysine.
  • An exception is quinoa (Chenopodium quinoa).
  • Animals generally provide better-quality protein.
  • Eggs are generally regarded as providing perfect
  • Deficiencies of individual plant foods can be
    remedied to a large extent by combining them.
  • Grains tend to be low in methionine pulses, low
    in lysine.
  • A grain/pulse mixture provides a more balanced
  • A balance can also be achieved on a plant
    diet with a small amount of meat or other animal

  • Carbohydrates, lipids (fats), and proteins are
    the bulk constituents of our diet.
  • We also need small amounts organic
  • Most can be obtained from fruits, vegetables, or

  • Vitamin C (ascorbic acid) is found only in fresh
    fruits and vegetables.
  • Vitamin A is derived from carotene, found in
    green, yellow, orange, or red fruits, vegetables,
    and grains.
  • Vitamin B12 is not provided by plants.
  • Cyanocobalamin is manufactured by bacteria,
    especially in ruminant organisms, is available in
    meat dairy foods.
  • We require six major inorganic nutrientscalcium,
    phosphorus, magnesium, sodium, potassium,
    chlorideand seven micronutrients.
  • All can be obtained from plant foods,
    although often more abundant in animal foods.

  • These figures are optimisticcereal yields
    in most countries are lower than in the U.S.

It is questionable whether the inputs used to
attain U.S. yields are physically available or
environmentally desirable on a worldwide scale.
  • Worldwide there are about 0.25 hectares (0.6
    acres) of cropland for each person.
  • With realistic inputs/yields, this is about
    enough to provide everyone with a vegetarian diet.
  • In addition to land required to grow crops, we
    should count area needed to provide inputs of
    energy and chemicals, and absorb the wastes
  • Chemical inputs of fertilizer pesticides can
    reduce the footprint, as they increase the yield
    from a given area.

  • Crop production has become concentrated and
    specialized in regions countries around the
  • California and Florida produce more than 60 of
    U.S. grown fruits and vegetables.
  • Crops can move thousands of miles from producer
    to consumer.

  • Some arguefrom an ecological perspectivethat we
    should consume local produce.
  • However, energy costs of transport are much
    lower than for out-of-season production in a
  • Nutrient flow from food transport presents
  • The nutrients in the produce are removed from the
    area where the crop was grown.

  • In moist, temperate parts of the world, it is
    easy to forget how much water is needed to
    produce crops.
  • It can take a ton of water to produce a kilogram
    of grain.
  • In dry areas, a large land surface may be needed
    to collect water to be used for irrigation to
    grow crops.
  • Water needs in arid locations cause political

  • Each person in an industrialized country takes
    about 1 hectare of cropland12 of their total
  • If everyone lived in an industrial economy,
    agriculture would occupy all of the worlds land.
  • Because people are not eating beans corn, these
    crops are being fed to animals.
  • Only 10 of the energy available in food crops is
    being recovered in the meat or other animal
  • Due to specialization, crops produced on one farm
    are fed to animals possibly hundreds of miles
  • The crop grower needs fertilizer to maintain high
  • The stock farm has the problem of disposing of
    animal wastes, which contain the same nutrients
    as the fertilizer.

Forage, Fiber, and Fuel
  • Ruminant animals extract energy from plant
    materials indigestible by humans.
  • When fed forage or allowed to graze pasture,
    energy recovery can be as high as 50 of that
    obtained from crops grown for human consumption.
  • Land unsuitable for crops can provide grazing for
  • It should be possible to provide a varied diet
    for the worlds population, if we
  • Reserve the best land for the production of crops
    for human consumption.
  • Confine animals to grazing on marginal land or
    limit their consumption to crop wastes.

Forage, Fiber, and Fuel
  • Grazing must be managed so that it does not lead
    to degradation of soils and vegetation that
    supports it.
  • Difficulty is greatest in tropical countries,
    where demand for food is often most acute.
  • In principle, pasture supports higher levels of
    biodiversity than fields from which crops are

Forage, Fiber, and Fuel
  • Historically, farming/agriculture/forestry has
    provided many useful products in addition to food.
  • Clothing and textiles structural materials fats
    burned for light/heat paper/cardboard dyes,
    perfumes, medicines.
  • Today most of these nonfood materials have been
    more or less replaced by synthetic materials.
  • Often produced from petrochemicals.

Forage, Fiber, and Fuel
  • Only about 2.5 of cropland is devoted to fiber
    crops, both in the U.S. and worldwide.
  • The market for natural fibers is
  • It is unlikely production area of fiber crops
    will increase in the near future.

Forage, Fiber, and Fuel
  • Hemp (Cannabis sativa), has growth potential due
    to high demand for its fiber for clothing and
    other uses.
  • A deep root system aids in reconditioning
    compacted soil.
  • Hemp which is grown for fiber is the same species
    as marijuanaunfortunately.
  • Producing the drug tetrahydro-cannabinol (THC).
  • Because hemp has environmental benefit a fiber
    that produces excellent fabric, many countries
    are again allowing it to be grown, under strict
  • Currently illegal in the U.S., but increasing
    pressure on government agencies is forcing a
    policy reevaluation.

Forage, Fiber, and Fuel
  • Biofuels result from processing of plants to
    produce biodiesel/ethanol for internal combustion
  • Oil from soybeans (Glycine max), sunflower
    (Helianthus annus) canola (Brassica rapa) is
    used as biodiesel fuel.
  • Starches/sugars in corn (Zea mays), sugarcane
    (Saccharum officinarum), and switchgrass (Panicum
    virgatum) are fermented to produce ethanol.
  • Because biofuel crops are often food crops, using
    them for fuel negatively affects the food supply.
  • Nonfood crops may occupy former food crop land.
  • Energy is required to produce the fuels so the
    net gain in fuel energy may be as low as 50.

Forage, Fiber, and Fuel
  • Apart from fiber and biofuel, the major nonfood
    use of crops is for nonfuel oil-based industrial
  • Tropical oil crops, such as coconut (Cocos
    nucifera) and oil palm (Elaeis guineensis), are
    the main sources of oils used in soaps and
  • Temperate oil crops, (canola soybean (Glycine
    max)), are used in the manufacture of lubricants
    and plastics.
  • Concerns about pollution petroleum availability
    have led to suggestions to return to plants as
    chemical feedstock.
  • For detergents, plastics, pharmaceuticals, and
    other industrial chemicals.

Forage, Fiber, and Fuel
Forage, Fiber, and Fuel
  • Before the industrial revolution, most fuels
    raw materials (except for metals) used to
    manufacture everyday goods were of biological
  • Sources gradually supplanted by coal and oil,
  • In 1930 plants supplied about 30 of raw
  • Today over 80 of chemicals are petroleum
  • Some suggest this trend will reverse, with 50 of
    chemical feedstock biological by 2050.
  • This would require a massive restructuring of the
    chemical industry and diversion of land from food

  • From the earliest history of modern humans, the
    shaman elders of a tribe used herbs to treat
    diseases and disorders among tribal members.
  • Ethanobotany study of plant usage by indigenous
    cultures preservation of the knowledge
    has become an important branch of plant science.
  • Until the last century, most medicines were
    derived directly from plants
  • Today, about 25 of pharmaceuticals are based on
    plant products, and the rest are produced
  • An example of modern-day medicine that can trace
    its roots to usage by Native Americans is
  • Salicylic acid is found in the bark of willow
    trees (Salix).

Pleasure, Ornamental, and Recreational Uses
  • Some plant products that we consume provide
    pleasure, but no nutritional benefitand may even
    be harmful to our health.
  • Tobacco and various forms of alcohol represent
    some very profitable ways of using land.
  • Tropical countries can find more profit in
    growing coffee or tea for export than producing
    staple food crops.
  • Sugarcane in the tropics and sugar beet in
    temperate countries tend to be more profitable
    than staple foods.
  • About 8 of the U.S. corn crop is used for corn
    syrup sweetener in this way, which helps raise
    corn prices.

Pleasure, Ornamental, and Recreational Uses
  • Since neolithic times, people have coevolved with
    agricultural plants and animals.
  • Shaped by selection/breeding, these organisms
    have influenced our physiology, psychology, and

Pleasure, Ornamental, and Recreational Uses
  • One of the most persistent expressions of
    biophilia is a desire for cut flowers or potted
  • In cool-temperate areas, these plants are mostly
    produced in greenhouses.
  • It is often cheaper to produce cut flowers in
    warmer countries transport them to the U.S. or

Pleasure, Ornamental, and Recreational Uses
  • A downside to human-made diversity is that, after
    introduction to the U.S., some ornamental plants
    have escaped to become agricultural weeds.
  • Others have become invasive displaced native
  • Environmental Protection Agency (EPA) data imply
    that more pesticides, mostly herbicides, are
    applied to lawns than to agronomic crops.

Pleasure, Ornamental, and Recreational Uses
Pleasure, Ornamental, and Recreational Uses
  • Ornamental crops, more labor intensive than other
    crop, account for nearly 20 of U.S. agricultural
    labor costs.
  • These enterprises provide jobs for many people,
    from day laborers to corporate executives.
  • Ornamentals may also require more intensive use
    of fertilizers and pesticides than traditional
  • Many greenhouses nurseries now practice water
    and fertilizer recycling and use low
    environmental impact methods of pest control when
  • These crops provide variety in our diets,
    materials for manufacturing, pharmaceuticals,
    perfumes, etc.
  • Playing a very important role in local/regional

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