Dec4,6,8,06 - December 4, 2006 Photosynthesis overview...

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December 4, 2006 Photosynthesis overview Light and carbon dioxide are the limiting factors for photosynthesis o There is a small concentration on CO2 in the atmosphere (.03%) o Plants have adapted to trap/attract light and CO2 and to utilize as much light and CO2 that they are exposed to as possible Leaf Structure o Planar structure (flat) Presents the maximum surface area for light intersection o Thin Only about 8-10 cell layers thick, which permits access of CO2 to all cells Also important for heat loss o Intercellular space Allows for rapid diffusion of gasses Maximizes internal reflection (plants absorb about 80% of the light they receive – that is why the front surface is shiny whereas the back is dull) o Columnar shape of the palisade cells (cells on the upper surface of the leaf) Lights is bounced around, absorbed by chloroplasts, and is transmitting downward (light piping) o Asymmetric distribution of chloroplasts There are more chloroplasts in the palisade than in cells lower down Leafs also maximize light absorption in that there is very little leaf overlap Phloem system (positive pressure) o Transports sugars and amino acids o If a tree is girdled, all the bark and phloem has been removed, but not the
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This note was uploaded on 04/25/2008 for the course BIO 101 taught by Professor ? during the Spring '08 term at UPenn.

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Dec4,6,8,06 - December 4, 2006 Photosynthesis overview...

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