Adaptations of Leaves

How are leaves in plants adapted to Gas Exchange and Photosynthesis

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Tissues within a leaf

  • Waxy Cuticle- waterproof and helps cut down water loss in the plant
  • Upper Epidermis
  • Palisade Mesophyll layer- main site of photosynthesis
  • Air space- allows air to circulate to maintain a diffusion gradient
  • Vascular Bundle- Contains Xylem and Phloem for the transport of water and mineral ions around the plant
  • Spongy Mesophyll Layer
  • Guard Cells- control opening and closing of stomatal pores
  • Stomata- Site of gas exchange
  • Lower Epidermis
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Leaves & Gas Exchange

  • The Leaf Blade is flat which provides a short diffusion pathyway, increases surface area to volume ratio
  • Spongy Mesophyll is permeated through airs spaces- this allows diffusion to take place and for gases to circulate which maintains diffusion gradients
  • Stomatal pores open and close to allow gas exchange to occur. This also prevents and reduces water loss which keeps surfaces moist which is important to allow gases to dissolve and diffuse
  • Mesophyll cells have partially permeable membranes which allows gases to diffuse in and out of cells.
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Leaves & Photosynthesis

  • Have a large surface area to increase the available area for light absorbsion and diffusion
  • Leaves can orientate themselves towards the sun, this is known as phototropism
  • The leaf is thin to allow light to reach lower layers. 
  • The cuticle and epidermis are waterproof
  • Palisade cells contain lots of chloroplasts and are elongated and densley packed together
  • Chloroplasts can move within the mesophyll cells to position themselves in areas with a higher light intensity
  • There are spaces between cells which allow carbon dioxide to diffuse into cells and for oxygen and water to diffuse away (water by osmosis)
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