1. Gas Exchange in Plants

2. Reactions that involve gasses Photosynthesis Photosynthesis Occurs in the chloroplast Occurs in the chloroplast Energy produced (glucose) Energy produced (glucose) Greater volumes of gasses exchanged in photosynthesis Greater volumes of gasses exchanged in photosynthesis Cellular respiration Cellular respiration Occurs in the mitochondria Occurs in the mitochondria Energy produced (ATP) Energy produced (ATP)

4. Where does the diffusion of gasses occur? Between the environment and the plant Between the environment and the plant Diffusion through the stomata Diffusion through the stomata Within the plant Within the plant Gasses move in and out of the the intercellular spaces (spongy tissue) Gasses move in and out of the the intercellular spaces (spongy tissue) Passive transport Passive transport

5. Stomata Where diffusion of gasses occurs Where diffusion of gasses occurs O 2 net movement out O 2 net movement out CO 2 net movement in CO 2 net movement in Underside of leaves Underside of leaves Guard cells control whether they are open or not (to leave them open would be inefficient. Guard cells control whether they are open or not (to leave them open would be inefficient. Link to other pictures

6. Guard Cells (GC) Kidney bean shaped Kidney bean shaped Take in potassium by active transport – stimulated by light on the leaf Take in potassium by active transport – stimulated by light on the leaf Increases the particles in the cell therefore water enters by osmosis and GC swell opening the stomata (because outer wall is thinner making it bulge out) Increases the particles in the cell therefore water enters by osmosis and GC swell opening the stomata (because outer wall is thinner making it bulge out) Allow minerals out of GC and thus H 2 O leaves via osmosis and the stomata closes Allow minerals out of GC and thus H 2 O leaves via osmosis and the stomata closes

8. Close the gates the water is getting out! Why not leave the stomata open? Why not leave the stomata open? For gasses to pass across the cell membrane they must be dissolved in water For gasses to pass across the cell membrane they must be dissolved in water Thus a film of water must surround the GC’s Thus a film of water must surround the GC’s

9. Why not leave the stomata open? So plants are constantly losing water So plants are constantly losing water This loss of water is called Transpiration This loss of water is called Transpiration Without closing GC the plants would become very dehydrated Without closing GC the plants would become very dehydrated

10. Sensitivity of Stomata Number and appearance depend on environment conditions Number and appearance depend on environment conditions Hot, dry climates with low humidity have fewer stomata Hot, dry climates with low humidity have fewer stomata High humidity = more stomata High humidity = more stomata Low CO 2 levels = stomata open Low CO 2 levels = stomata open Normal levels of CO 2 = stomata relaxed Normal levels of CO 2 = stomata relaxed

11. Beyond the Leaf In the roots and stem gas exchange occurs in the outer layer of cells In the roots and stem gas exchange occurs in the outer layer of cells Lenticels break though the bark (on woody plants) and allow air to diffuse though Lenticels break though the bark (on woody plants) and allow air to diffuse though Within the plant diffusion is used in the spongy tissue Within the plant diffusion is used in the spongy tissue

12. Lenticels

13. Overall Gas exchange in plants is completed by diffusion Gas exchange in plants is completed by diffusion No specific organ involved No specific organ involved

14. REFRENCES www.goole.com www.goole.com www.goole.com www.iteachbiology.com www.iteachbiology.com