Topic 14'2 Plant Nutrition

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Topic 14.2 - Plant Nutrition

• Biology 1001 - November 18, 2005

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5. Essential Minerals of Plants

• Mineral nutrients are essential chemical elements
  that plants extract from the soil in the form of
  inorganic ions
• Macronutrients are needed in relatively large
  amounts
• Nitrates supply nitrogen
• Phosphates supply phosphorus
• Sulfates supply sulfur
• Ca2, Mg2, K
• Generally function as components of
  macromolecules eg. Mg2 is a component of
  chlorophyll K functions in water balance
• Micronutrients are needed in very small amounts
• Ionic forms of chlorine, iron, manganese, boron,
  zinc, copper, nickel, and molybdenum
• Often function as enzyme cofactors, components,
  or to activate enzymes
• Macronutrients and micronutrients are essential
  elements because they are required for a plant to
  complete its life cycle
• Without the proper nutrients, mineral
  deficiencies occur

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Mineral Deficiencies
Chlorosis due to Mg2 deficiency
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6. Obtaining Nutrients

• Figure 37.2!
• Carbon dioxide enters the plant through the
  stomata in the leaf
• Water, mineral nutrients and oxygen are absorbed
  through the roots
• Water and oxygen exit the plant through the leaf,
  while carbon dioxide is expelled from the roots
• Plants are net producers of oxygen and net
  consumers of carbon dioxide and water
• 80-90 of a plants wet weight is water
• The bulk of a plants dry mass is derived from
  carbon dioxide

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The Role of Bacteria in Symbiotic Nitrogen
Fixation

• Symbiotic relationships with nitrogen-fixing
  bacteria provide certain plants with a source of
  fixed nitrogen
• Usually plants in the legume family eg. Peas,
  soybeans, peanuts, alfalfa and clover
• The bacteria, such as Rhizobium, live in
  swellings on the roots called nodules that
  consist of plant cells with the bacteria in the
  form of bacteroids located in vesicles

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Mycorrhizae and Plant Nutrition

• Mycorrhizae (fungus roots) are modified roots
  consisting of mutualistic associations of fungi
  and roots
• The fungus benefits from a steady supply of sugar
  donated by the host plant
• The fungus increases the surface area for water
  uptake by the root, and selectively abosrbs
  phosphates and other minerals from the soil and
  supplies them to the plant
• Occur in most plant species, and probably
  represent an early adaptation to a terrestrial
  environment

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Unusual Nutritional Adaptations of Plants

• Epiphytes, parasitic plants and carnivorous
  plants use other organisms in unusual
  nonmutualistic ways
• Epiphytes nourish themselves but grow on other
  plants
• They obtain water and minerals through leaves,
  from rain
• Parasitic plants absorb sugars and minerals from
  their hosts
• Some are photosynthetic, some not
• Roots may function as haustoria,
  nutrient-absorbing projections into the host
  plant
• Carnivorous plants obtain nitrogen and minerals
  by killing and digesting small animals such as
  insects
• They are photosynthetic, but live in acid bogs
  and other mineral-poor soils

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Unusual Nutritional Adaptations in Plants