Plant and Animal Nutrition

• The basic photosynthetic reaction

  Carbon dioxide (CO2) + Water (H2O) → Glucose (C₆H₁₂O₆) + Oxygen (O2)
• Glucose contains the elements carbon, oxygen, and hydrogen – the only elements occurring in complex sugars and in most fats
• Carbohydrates and fats occurring in plants can be made from water and carbon dioxide alone
• Plants also require various other inorganic nutrients
• Compounds that require phosphorus, nitrogen, and sulfur for biosynthesis


  • Amino acids
  • Phospholipids
  • Nucleic acids
  • ATP
• Nutrients


  Any substance required for the growth and maintenance of an organism
• Types of organisms based on mode of nutrition

  • Autotrophs
  • Heterotrophs
• Autotrophs


  Organisms that obtain energy from sunlight and chemicals to produce their own food (e.g. plants)
• Heterotrophs


  Organisms that cannot make their own food and obtain their energy from other organisms (e.g. fungi)
• Macronutrients

  • Nitrogen
  • Potassium
  • Phosphorus
  • Sulfur
  • Calcium
  • Magnesium
• Nitrogen


  Needed for proper leaf growth and development. Deficiency can produce yellowing of older leaves or a general lightening of all the green parts of the plant, combined with stunting of growth. Excess produces hypertrophy of foliage and suppresses fruit production.
• Potassium


  Most important for maintaining the membrane potential of plant cells, and perhaps their turgidity as well (especially in the guard cells of the stomata). Deficiency produces general symptoms of poor health, which can include localized chlorosis (low chlorophyll content), or mottling of leaves with small spots of dead tissue at the tips and between the veins of lower leaves.
• Phosphorus


  Essential for the production of such vital compounds as the nucleic acids and ATP. Needed for flowering, fruiting, and root development. Deficiency produces small dark green leaves over the entire plant and the abnormal presence of red and purple colors in the leaves and stalks.
• Sulfur


  Essential component of protein because of its occurrence in the amino acids cysteine and methionine. Deficiency produces chlorosis in new leaves and buds, usually without spotting, and poor root development. Sulfur can't be absorbed in elemental form but must be present as sulfate.
• Calcium


  Important component of the middle lamella of cell walls (along with pectin). Typically, the terminal bud dies, following a period in which small leaves with dried-up tips are produced. Has a multitude of cellular functions in the plant body. Deficiency causes abnormal growth and cell division.
• Magnesium


  Required for the action of many enzymes and needed in the synthesis of chlorophyll, which contains it. Deficiency produces mottled chlorosis.
• Micronutrients


  • Iron
  • Boron
  • Zinc
  • Manganese
  • Chlorine
  • Molybdenum
  • Copper
• Iron


  Needed in several of the electron transport substances of the cell (ferredoxin, cytochromes), and in some other materials (e.g., phytochrome). Required for chlorophyll synthesis. Deficiency causes interveinal chlorosis characterized by yellowing of the leaf along the veins, that is confined to the youngest leaves. Deficiency in iron absorption can occur in soils with high or low pH.
• Boron


  Function is unknown. Deficiency causes abnormally dark foliage, growth abnormalities, and malformations. Root tip elongation also shows.
• Zinc


  Required for the production of amino acid tryptophan. Since auxins are derived from tryptophan, zinc is indirectly required for the production of auxins as well. Also required as a cofactor for some of the DNA polymerase enzymes. Deficiency produces small leaves and stunted stems owing to short internodes. Excess is poisonous to plants.
• Manganese


  Required as a cofactor for enzymes in oxidative metabolism and in photosynthetic oxygen production. Deficiency produces a mottled, characteristic form of chlorotic leaf yellowing.
• Chlorine


  Required for ionic balance and maintenance of cellular membrane potentials. Needed for oxygen production in photosynthesis. Deficiency results in very small leaves and slow growth. Leaves become wilted, chlorotic, or even necrotic and may eventually become bronze-colored.
• Molybdenum

  Needed as part of the denitrifying and nitrogen-fixing enzymes of microorganisms. Plants must utilize this enzyme if they are to employ nitrate as a nitrogen source. However, plants that absorb ammonia as a nitrogen source do not need molybdenum. Deficiency causes low productivity.
• Copper


  Component of some enzymes and cytochromes. Deficiency causes lowered rate of protein synthesis and sometimes in chlorosis. Young leaves may be dark green and twisted, with dead spots.
• Root hairs


  • Slender extensions of specialized epidermal cells that greatly increase the surface area available for absorption
• Root nodules


  • Localized swellings in roots of certain plants where bacterial cells exist symbiotically with the plant. The bacteria help the plant fix nitrogen and in turn, the bacteria are able to utilize some organic compounds provided by the plant.
• Mycorrhizae


  • Symbiotic interaction between a young root and a fungus. The fungus obtains sugars and nitrogen-containing compounds from root cells while the plant is able to get some scarce minerals that the fungus is better able to absorb from the soil.
• Routes for the absorption of water and minerals across plant roots

  • Symplast route (through plasmodesmata)
  • Apoplasy route (along cell walls)

  
• The water and minerals from the soil need to reach the conducting tissues of plants, specifically the xylem

  
• Symbiosis of plants and soil microbes

  • Nitrogen fixation: Biological nitrogen fixation (BNF) is the conversion of atmospheric nitrogen (N2) into ammonia (NH3) exclusively carried out by prokaryotes, such as soil bacteria or cyanobacteria. Biological processes contribute 65% of the nitrogen used in agriculture. The most important source of BNF is the symbiotic interaction between soil bacteria and legume plants, including many crops important to humans. The NH3 resulting from fixation can be transported into plant tissue and incorporated into amino acids, which are then made into plant proteins.
• Some legume seeds, such as soybeans and peanuts, contain high levels of protein and are among the most important agricultural sources of protein in the world
• Mycorrhizae: The symbiotic relationship between fungi and roots


  • A nutrient depletion zone can develop when there is rapid soil solution uptake, low nutrient concentration, low diffusion rate, and low soil moisture. These conditions are very common; therefore, most plants rely on fungi to facilitate the uptake of minerals from the soil.

  
• Biological nitrogen fixation (BNF)


  The symbiotic interaction between soil bacteria and legume plants, including many crops important to humans
• Nitrogen fixation


  NH3 resulting from fixation can be transported into plant tissue and incorporated into amino acids, which are then made into plant proteins
• Legume seeds


  • Soybeans
  • Peanuts
• Legume seeds contain high levels of protein and are among the most important agricultural sources of protein in the world
• Mycorrhizae


  The symbiotic relationship between fungi and roots
• Nutrient depletion zone development

  1. Rapid soil solution uptake

  2. Low nutrient concentration

  3. Low diffusion rate

  4. Low soil moisture
• Most plants rely on fungi to facilitate the uptake of minerals from the soil due to the common conditions that lead to nutrient depletion zones
• Mycorrhizae


  • Form symbiotic associations with plant roots, where the fungi are integrated into the physical structure of the root
  • Fungi colonize the living root tissue during active plant growth
  • Through mycorrhization, the plant obtains phosphate and other minerals from the soil, and the fungus obtains nutrients such as sugars from the plant root
  • Help increase the surface area of the plant root system because hyphae can spread beyond the nutrient depletion zone
  • Function as a physical barrier to pathogens
  • Provide an induction of generalized host defense mechanisms, which sometimes involves the production of antibiotic compounds by the fungi
  • Have a protective role for plants rooted in soils with high metal concentrations, such as acidic and contaminated soils
  • The beneficial effect on the plant is best observed in poor soils
  • Fungi can obtain up to 20 percent of the total carbon accessed by plants