Photosynthesis

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Plant Structure and Photosynthesis

Plants are made of stems, roots and leaves (organs, made of tissue).

Leaves are made of:

  • Mesophyll tissue - most of photosynthesis occurs here
  • Xylem and Phloem - transport water, mineral ions and sucrose around the plant
  • Epidermal tissue - covers the WHOLE plant 

Equation for Photosynthesis:

                                                           (sunlight)

carbon dioxide + water --------------------------> glucose + oxygen  

                                                       (chlorophyll)

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Photosynthesis

  •  the process that produces FOOD in plants and algae. The food is GLUCOSE 
  • happens in chloroplasts, which contain chlorophyll (green substance) - absorbs sunlight, uses energy to convert carbon dioxide and water into glucosee. Oxygen may also be produced
  • happens in leaves of all green plants.

4 raw materials needed for photosynthesis:

1. sunlight: beating down on leaf provides energy for the process

2. chlorophyll: contained in chloroplasts

3. water: reaches the cells by the xylem

4. carbon dioxide: diffuses into the leaf 

the epidermis are located at the top and bottom of the leaf, allowing carbon dioxide and oxygen to diffuse through, the mesophyll is located in the middle of the leaf between the epidermis. 

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Rate of Photosynthesis

The limiting factor (preventing photosynthesis from happening faster) is dependent on the conditions. 

Factors are limited at particular times as it depends ont he environmental conditions:

  • at night, light is the limiting factor
  • in winter, the temperature is affected
  • if it is warm and bright, the amount of carbon dioxide is limited
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Rate of Photosynthesis - Light

If light is limited, it slowws down the rate of photosynthesis:

  • light provides energy 
  • when light increases, photosynthesis increases to a certain point

in that case, the temperature or carbon dioxide level is the limiting factor 

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/photosyn_1.gif)

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Rate of Photosynthesis - Carbon Dioxide

Too little carbon dioxide slows down the rate of photosynthesis 

  • raw material needed for photosynthesis 
  • amount of carbon dioxide increases, photosynthesis increases to a certain point
  • in that case, the graph flattens, indicating the carbon dioxide is not a limiting factor
  • temperature is now the limiting factor if both light and carbon dioxide are fully supplied

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Rate of Photosynthesis - Temperature

  • has to be just right 
  • if it is the limiting factor, it is too low, the enzymes needed for photosynthesis work slower at lower temperatures
  • if the plant gets too hot, the enzymes are denatured 

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/photosyn_3.gif)

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