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Light Plant Science Chapter #8. What is light?  energy that travels in wavelengths  short wavelengths = high energy (blue)  long wavelengths = low.

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Presentation on theme: "Light Plant Science Chapter #8. What is light?  energy that travels in wavelengths  short wavelengths = high energy (blue)  long wavelengths = low."— Presentation transcript:

1 Light Plant Science Chapter #8

2 What is light?  energy that travels in wavelengths  short wavelengths = high energy (blue)  long wavelengths = low energy (red)  ultraviolet = invisible

3 What is meant by light quality?  amount of light of different colors  plants absorb red & blue, reflect green  smoke filters blue, sun looks red  glass & plastic filter light

4 What is meant by light quantity?  amount of light energy recieved  measured in foot candles – summer day = 10,000 – living room = 20  crops need 100-10,000  if not enough light, grow tall(leggy, weak stems)  weed control reduces competition for light  planting rate & row spacing  some plants need shade (tobacco), burlap, lathes, screens

5 What is light duration?  length of day  Long Day Plants >13 hours  Short Day Plants <12 hours  Day Neutral Plants = no response

6 How does temperature influence crop selection?  Warm Season Crops - soil temp >70 degrees (corn)  Cool Season Crops - soil temp <70 degrees (wheat)

7 What are the Cardinal Temperatures?  minimum, maximum, optimal temperatures for a crop  wheat min=40 max=90 (when flowering)  crops generally don't grow in areas where average 24 hour temperature 130

8 What is the Frost Free Period?  the time from the last killing frost until the first killing frost of summer  at least 90 days  plant spring wheat when average soil temperature is 37 degrees

9 How does snow cover affect the temperature of the soil?  snow cover insulates, keeps warm

10 How can we keep a crop from freezing? (orchards etc.)  heaters, smudge pots, irrigation, fans

11 What is Vernalization?  some plants need periodic exposure to cold to regulate life cycle  cherries, winter wheat, sugar beet

12 What is Bolting?  sugar beets are exposed to cold during the first year, which triggers the plant to flower instead of develop roots

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