Respiration

• Respiration


  The process of converting the chemical energy in food molecules into a form that can be used by cells
• Respiratory systems (Gaseous exchange surfaces) in plants


  • No well-developed or highly specialised respiratory systems
  • Certain structures allow the movement of gases into and out of the plant
• Structures that allow the movement of gases in plants

  • Stomata
  • Lenticels
  • Root hairs
• Most of the oxygen used by the plant for cellular respiration is produced by the mesophyll cells during photosynthesis
• On a sunny day, so much O2 is produced, that it is given off as a waste product
• Plants have a low metabolic rate and the O2 produced during the day more than satisfies their needs
• Stomata


  1. Early in the morning, when the rate of photosynthesis is low, O2 will diffuse through the stomata and through the cell walls of the leaf cells into the cytoplasm

  2. This continues as long as there is less O2 present in the cell than in the air spaces
• The cell walls of the mesophyll cells act as the main respiratory surface of the plant
• Lenticels


  • Pores located on the stem
  • Below each lenticel there are loosely packed cells with air spaces which allow the diffusion of gases into and out of the stem
• Root hairs


  • Delicate outgrowths of the epidermal cells of plant roots
  • Each is very long and narrow
  • The walls are very thin and permeable
  • The large number of root hairs provide a large total surface area
• Root hairs


  1. Oxygen dissolved in soil water diffuses into the cytoplasm of the root hairs

  2. Carbon dioxide diffuses outwards