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Gas Exchange in Plants

Gas Exchange in Plants. Reactions that involve gasses. Photosynthesis Occurs in the chloroplast Energy produced (glucose) Greater volumes of gasses exchanged in photosynthesis Cellular respiration Occurs in the mitochondria Energy produced (ATP). Where does the diffusion of gasses occur?.

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Gas Exchange in Plants

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  1. Gas Exchange in Plants

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

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

  4. Stomata • Where diffusion of gasses occurs • O2 net movement out • CO2 net movement in • Underside of leaves • Guard cells control whether they are open or not (to leave them open would be inefficient. Link to other pictures

  5. Guard Cells (GC) • Kidney bean shaped • 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) • Allow minerals out of GC and thus H2O leaves via osmosis and the stomata closes

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

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

  8. Sensitivity of Stomata • Number and appearance depend on environment conditions • Hot, dry climates with low humidity have fewer stomata • High humidity = more stomata • Low CO2 levels = stomata open • Normal levels of CO2 = stomata relaxed

  9. Beyond the Leaf • 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 • Within the plant diffusion is used in the spongy tissue

  10. Lenticels

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

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