Gas exchange in plants

• Gas exchange: The process by which oxygen and carbon dioxide diffuse in and out of the blood
• the structure of a leaf; being large and flat, increases the surface area available for gas exchange
• the irregularly shaped spongey mesophyll cell layer creates air pockets and further increases the surface area of the leaf, and allows gases to travel freely
• the moist surfaces of the spongy mesophyll cells dissolves gases, making movement more effective.
• most gaseous exchange occurs in the stomata and lenticels
• stomata: openings on the underside of the leaf that allow gases to enter and exit
• lenticels: pores in the bark that allow gases to move in and out
• stomata are:

  -mostly found on the underside of leaves

  -bordered by two bean-shaped guard cells, with a thick inner wall and a thin outer wall

  -able to open and close
• open stomata's:

  -water moves into the guard cells, the thin outer walls stretch outwards, but the thin inner walls dont flex-causing the pore to widen

  -open in the daytime, triggered by light

  -water moves out of the plant, more water is lost as temperature increases, gas exchange occurs
• closed stomata's:

  -water moves out of the guard ells, outer walls dont bulge, so the inner walls move together closing the pore

  -closed at night, triggered by the light

  -no water or gas exchange occurs
• the functions of a stomata:

  -Gaseous exchange; Stomata allow a plant to take in carbon dioxide needed for photosynthesis and remove oxygen.

  -Transpiration; Stomata help reduce water loss by closing when conditions are hot or dry.

  -Moisture balance; They maintain moisture balance by opening and closing according to weather.
• lenticels allow for gaseous exchange, although the diffusion of gases through the lenticel is relatively slow
• the process of gas exchange in plants:

  1. stomata open and allow CO2 from the atmosphere to diffuse into the leaf.
  2. CO2 is absorbed by mesophyll cells within the leaf.
  3. inside the leaf, CO2 combines with water to form glucose and oxygen, during the process of photosynthesis.
  4. the oxygen produced during the photosynthesis exits the leaf through the open stomata and diffuses into the atmosphere.
  5. Glucose produced is used by the plant as energy.