Chemical Uses

• Major sources for food

• Major sources for medicines & drugs

• Contain antimetabolites

• Contain food reserves for plant development
  

• Major sources of industrial raw products

  ---

Carbohydrates

• Major storage substance

  • Starch
    • Amylose
      • Straight chain, 200-1,000 glucose units
    • Amylopectin
      • Branched (20-25 glucose units per branch)
      • Major component in most starch grains
  • Hemicellulose
    • Second major form of carbohydrate
    • Found in cell walls and as reserve materials
  • Mucilages
    • Frequently found as a coating material
  • Pectic compounds
    • Pectin
    • Pectic acid
    • Protopectin
      • Above found in cell walls & middle lamella
• Lipids
  • Are highly unsaturated
  • Remain solid at room temperatures
  • Generally associated with lower protein contents
  • Basic types
    • Fats
    • Fatty oils
    • Waxes
    • Phospholipids
• Proteins
  • N-containing compounds
  • Typically only serve as food reserves for the embryo
  • Source of amino acids
  • Basic forms
    • Enzymes
    • Nucleoproteins
      • Deoxyribonucleic acid (DNA)
      • Ribonucleic acid (RNA)
    • Albumins
      • Mainly enzymes
    • Globulins
      • Found predominately in dicots
    • Glutelins
      • Found in most cereal grains
    • Prolamines
      • Are found only in cereal grains
• Other significant chemicals
  • Tannins
    • Have the unique ability to tie up proteins and inhibit enzymatic activity
  • Alkaloids
    • Are complex cyclic N-containing compounds
    • May be solid or liquid
  • Glucosides
    • Formed by reaction between sugar and nonsugar compounds
  • Phytin
    • Major source of P, Mg and K  in seeds
    • Found in the aleurone layer of cereal seeds
  • Growth regulators
    • Auxin
      • May enhance or inhibit germination depending upon species and concentration
      • Is not regarded to be generally important
    • Gibberellins
      • Have a major role in germination
    • Cytokinins
      • Is necessary for cell growth and differentiation
    • Inhibitors
      • Interact with growth regulators to control dormancy
    • Vitamins
      • Role in seeds not fully understood
      • Thiamine appears necessary for developing embryo and endosperm
• Genetic factors
  • Chemical composition varies within and between species
  • Composition can be modified by transgenic manipulation
    • "Energy Dense" corn seed
      • Larger endosperm
        • High oil content
          • Oil 225%> energy than starch
        • High quality protein
    • Modified amino acid composition
      • Lys, Try and Met > in corn
• Environmental influences
  • Cultural practices
    • Planting date
      • Can alter protein % and oil content sb_date4.gif
    • Soil fertility
      • High N = higher protein
    • Plant population
  • Environment
    • Day and night temperatures
      • High temperatures have increased oleic acid levels in rapeseed and sunflower
      • Higher temperatures increased oil content in soybean sb_oil.gif
    • Soil moisture
    • CO₂ concentration sb_co2.gif

References:

Principles of Seed Science and Technology, 3rd Ed., L.O. Copeland and M.B. McDonald. Chapman and Hall, New York, 1995.