6 - Plant Nutrition

• Plant Nutrition
• Subtopics

  • Types of nutrition
  • Photosynthesis
  • Leaves
  • Uses of glucose
  • Testing leaves for starch
  • Limiting factors
  • The importance of photosynthesis
• Nutrition is taking in useful substances for energy, growth and development
• Nutrition/Feeding


  • Plants: light, carbon dioxide, water and ions
  • Animals: organic compounds and ions and usually need water
• Heterotrophs

  Animals and fungi that can’t make their own food and feed on organic substances originally made by plants
• Autotrophs


  Green plants that make their own food and use simple inorganic substances (carbon dioxide, water, minerals)
• Organic substances


  Any substance containing carbon-based compounds, especially produced by or derived from living organisms
• Organic compounds


  Molecules associated with living organisms that contain carbon, including carbohydrates, lipids, nucleic acids, proteins, enzymes, and hydrocarbon fuels
• Inorganic compounds


  Compounds which do not contain carbon and are not derived from living matter
• Photosynthesis


  The process where plants produce glucose and oxygen by combining carbon dioxide and water with the help of light energy
• Photosynthesis


  Light energy + carbon dioxide + water → glucose + oxygen
• Chlorophyll


  Green pigments that trap sunlight, inside the chloroplasts
• Light energy is absorbed when sunlight falls on chlorophyll
• The chlorophyll releases energy, which makes carbon dioxide combine with water, with the help of enzymes in the chloroplast
• Leaf structure and adaptation

  • Lamina
  • Vein (Vascular bundles)
  • Epidermis
  • Guard cell
  • Stoma
  • Air space
  • Mesophyll layer
  • Cuticle
  • Cell Wall
  • Vacuole
  • Cytoplasm
  • Nucleus
  • Chloroplast
• Xylem

  Carry water or mineral salts upward
• Phloem


  Carry glucose (in the form of sucrose) upward/downward
• Vascular bundles are transport system tissues in plants
• The leaf structure includes a waxy cuticle layer to prevent water loss
• The upper epidermis layer protects inner cells
• The palisade mesophyll layer is for maximum photosynthesis
• The spongy layer contains air spaces to allow for oxygen, carbon dioxide and water vapor to pass through
• The lower epidermis layer contains guard cells and stomata to let the oxygen and carbon dioxide pass
• Leaves are adapted to obtain carbon dioxide, water and sunlight
• Carbon dioxide acquisition

  Diffuses in through stomata on the leaf
• Water acquisition

  Absorbed by root hair cells in the root hairs
• Sunlight acquisition

  Broad and flat surface of leaf helps to obtain sunlight
• Adaptation


  Function supported by stem and petiole to expose as much of the leaf as possible to sunlight and air
• Large surface area


  To expose as large an area as possible to sunlight and air
• Thin leaves


  To allow sunlight to penetrate to all cells; to allow CO2 to diffuse in and O2 to diffuse out as quickly as possible
• Stomata in lower epidermis


  To allow CO2 to diffuse in and O2 to diffuse out
• Air spaces in spongy mesophyll


  To allow CO2 and O2 to diffuse to and from all cells
• No chloroplasts in epidermal cells


  To allow sunlight to penetrate to the mesophyll layer
• Chloroplasts containing chlorophyll


  Present in the mesophyll layer to absorb energy from sunlight
• Palisade cells arranged end on

  To keep as few cell walls as possible between sunlight and the chloroplasts
• Chloroplasts inside palisade cells arranged broadside on


  To expose as much chlorophyll as possible to sunlight
• Xylem tubes


  Within short distance of every mesophyll cell to supply water to the cells in the leaf
• Phloem tubes


  Within short distance of every mesophyll cell to take away sucrose and other organic products of photosynthesis
• All cells need energy to do metabolic reactions
• Glucose will be broken down by respiration of cells