LightLightPlant ScienceChapter #8

What is light?What is light?

energy that travels in wavelengths short wavelengths = high energy (blue) long wavelengths = low energy (red) ultraviolet = invisible

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

What is meant by light What is meant by light quantity?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

What is light duration?What is light duration?

length of day Long Day Plants >13 hours Short Day Plants <12 hours Day Neutral Plants = no response

How does temperature How does temperature influence crop influence crop selection?selection? Warm Season Crops - soil temp >70

degrees (corn) Cool Season Crops - soil temp <70 degrees

(wheat)

What are the Cardinal What are the Cardinal Temperatures?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 <50 or >130

What is the Frost Free What is the Frost Free Period?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

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

How can we keep a How can we keep a crop from freezing? crop from freezing? (orchards etc.)(orchards etc.)

heaters, smudge pots, irrigation, fans

What is Vernalization?What is Vernalization?

some plants need periodic exposure to cold to regulate life cycle

cherries, winter wheat, sugar beet

What is Bolting?What is Bolting?

sugar beets are exposed to cold during the first year, which triggers the plant to flower instead of develop roots