UV and Insect eyes

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UV and Insect eyes
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• LIGHT
• PHOTOSYNTHESIS

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Spectrum
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Fate of intercepted light?

• Reflect
• Transmit
• Absorb

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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?

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Fig. 5.4
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Absorption

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

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Leaf area index
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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

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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)

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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?

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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

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Light levels year profile
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Photosynthetic Terms

• PAR photosynthetically active radiation
• Light compensation point (LCP)
• Light saturation point (LSP)
• photoinhibition

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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

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LCP
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Shade tolerant

• Low PS rates
• Low respiration rates
• Low metabolic rates
• Low growth rates

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Shade -intolerant

• Higher PS rates
• Higher respiratory rates
• Higher growth rates
• Lower survival in shade conditions

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Shade and Seedlings
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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?

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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?

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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?

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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?

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Shade-Sun leaf
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PS and Temperature

• See page 59 Fig. 6.3-6.4

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PS and Temperature
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PS and temp
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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

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Plants and Temperature

• Frost hardiness mostly genetic
• Addition of protective compounds (antifreeze
  type) allows super cooling
• Ice forms in the cell wall????
• Transpiration cooooooling

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Temperature and plants
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Photosynthesis
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Light Absorption
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PS Activity Problem
Relative PS activity
400 500 600 700
Wavelength
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Light Problem
A
B
C
D
Relative Absorbency
400 500 600 700
Wavelength (nm)
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Photosynthesis

• 6CO2 12 H20 ---gt C6H12O6 6H20 602
• OR
• 6CO2 6 H20 ---gt C6H12O6 602

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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?

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Fates of reactants
C6H1206
H20
C02
02
H20
H20
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Photosynthesis
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PS Activity Problem
Key Plant A Plant B
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Movement of water