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UV and Insect eyes

UV and Insect eyes. LIGHT & PHOTOSYNTHESIS. Spectrum. Fate of intercepted light?. Reflect Transmit Absorb. Fate of leaf intercepted light?. Reflect - (6-12% PAR, 70% infrared, 3% UV) Degree of reflection varies with type of leaf surface

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UV and Insect eyes

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  1. UV and Insect eyes

  2. LIGHT & PHOTOSYNTHESIS

  3. Spectrum

  4. Fate of intercepted light? • Reflect • Transmit • Absorb

  5. Fate of leaf intercepted light? • Reflect - (6-12% PAR, 70% infrared, 3% UV) Degree of reflection varies with type of leaf surface • Transmit - average 10-20% (primarily green and far red) • What would influence this? thickness and structure of leaf • Absorb – What does this depend upon?

  6. Fig. 5.4

  7. Absorption • What determines how much light a plant or a group of plants will intercept? • Quantity and position of leaves

  8. Leaf area index

  9. Leaf Area IndexLAI Interpretation of LAI see fig 5.5 (d) pg 47 (m2 leaf area/m2 ground area) LAI 3 means 3m2 leaf area over each m2 of ground

  10. LAIs of different canopy types Summer Temperate Deciduous Forest: LAI 3-5 (1-5% light hitting canopy reaches floor) Summer Pine Forest LAI 2-4 (10-15% light hitting canopy reaches floor) Tropical Rain Forest LAI 6-10 (.25 – 2% light reaches floor)

  11. Light levels and LAI • Why is the amount of light reaching the forest floor of the pine forest greater than that of the deciduous forest? • Does the LAI of an area change throughout the year? • What are the consequences of this for plants of the forest floor?

  12. Light Levels • Are there other factors other than LAI and leaf angle that would influence the amount of light a forest floor organism might receive? See Fig. 5.7 page 49

  13. Light levels: year profile

  14. Photosynthetic Terms • PAR – photosynthetically active radiation • Light compensation point (LCP) • Light saturation point (LSP) • photoinhibition

  15. PS terms expanded • Light compensation point: rate of C02 uptake in PS = rate of C02 loss in Respiration • Short version rate of PS = rate of respiration • Light Saturation Point – Point at which increasing light does not increase PS • Photoinhibition - High light levels inhibit PS

  16. LCP

  17. Shade –tolerant • Low PS rates • Low respiration rates • Low metabolic rates • Low growth rates

  18. Shade -intolerant • Higher PS rates • Higher respiratory rates • Higher growth rates • Lower survival in shade conditions

  19. Shade and Seedlings

  20. Apply your Smarts • How does the concentration of Rubisco relate to photosynthesis rate? • What does the production of Rubisco have to do with respiration? • What do respiration rates have to do with tolerance to shade?

  21. Apply your Smarts • What do respiration rates have to do with the light compensation point? • What does the light compensation point have to do with shade tolerance or intolerance? • In general what types of plants would you expect to have a lower light saturation point: shade inotlerant or shade tolerant Why?

  22. Apply your Smarts • What would you change in a plant that would increase or lower the light compensation point? • Plant a shade intolerant plant in the shade. What would the plant do to compensate for being in low light?

  23. Leafs and Light • How does the amount of light a leaf receives influence its shape and sizE? • See page 52 • And what does surface area and volume have to do with it?

  24. Shade-Sun leaf

  25. PS and Temperature • See page 59 Fig. 6.3-6.4

  26. PS and Temperature

  27. PS and temp

  28. Plants and Temperature • Heat gain and loss – What are the parameters? • Reflectivity of leaf and bark • Orientation of leaves to sun and wind? • Size and shape of leaves Frost hardiness – • Transpiration cooooooling………

  29. Plants and Temperature • Frost hardiness – mostly genetic • Addition of protective compounds (antifreeze type) allows super cooling • Ice forms in the cell wall???? • Transpiration cooooooling………

  30. Temperature and plants

  31. Photosynthesis

  32. Light Absorption

  33. 100% 0% PS Activity Problem Relative PS activity 400 500 600 700 Wavelength

  34. 100% 0% Light Problem A B C D Relative Absorbency 400 500 600 700 Wavelength (nm)

  35. Photosynthesis 6CO2 + 12 H20 ---> C6H12O6 + 6H20 + 602 OR 6CO2 + 6 H20 ---> C6H12O6 + 602

  36. PS Problem • If you put a plant in a closed container with an atmosphere of 14C02, and H2180 where would you find the radioactive carbon and the heavy oxygen (180) in the container and/or plant?

  37. Fates of reactants C6H1206 H20 C02 02 H20 H20

  38. Movement of water

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