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EFFECT OF LIGHT QUALITY ON PLANTS
 
1) photosynthesis
    a) chlorophyll absorbs predominately blue and orange-red light
    b) green-yellow is transmitted and reflected

2) growth responses - due to effect on photosynthesis
    a) colored coverings
         1) plant canopy - shade rich in green-yellow & far red, poor in blue & orange-red light
         2) fiberglass -
         3) tinted/shaded glass
         4) shade cloth or saran
    b) artificial light sources
         1) tungsten - rich in red and far red
         2) fluorescent - rich in blue and yellow-orange
         3) HID - varies

3) pigments
    a) anthocyanins- blue, red and purple in color
    b) carotenoids- orange and yellow in color; absorb 450-500 nm (blue and green);
                                   carotenoids can pass energy to chlorophyll to assist in photosynthesis
    c) phytochrome- absorbs red (660 nm) and far red (730 nm) light; involved in
                                      photomorphogenic and photoperiodic responses
 


     
4) seed germination in light requiring seeds
     Some seeds will only germinate in the light, therefore sow on surface to see sunlight.
     a) sunlight and any white or red light causes germination; (causes Pfr form to be present)
     b) far red light inhibits germination (causes Pr form to be present)
 
 
CONCEPT OF THE "ATMOSPHERIC WINDOW"
The 400 to 700  nm wavelength band of radiation (visible light) from the sun passes through the atmosphere relatively unaffected before reaching the earth's surface, whereas other wavelengths (especially UV and  IR) are absorbed, reflected or scattered by the atmosphere.
  • ultraviolet light - absorbed by ozone
  • visible light - not selectively affected
  • infrared light - absorbed by carbon dioxide and water vapor
Thus, the atmosphere acts as a window allowing visible light through relatively unaffected.  Plants and animals are adapted to utilize this relatively stable source of radiation in their photosynthesis, photomorphogenic responses, sight, etc.