Why is light Why is light important? important? 1.) Photosynthesis 6CO 2 + 12H 2 O (chl chl & light light ) ) C 6 H 12 O 6 + 6O 2 + 6H 2 O 2.) Needed for chlorophyll production 3.) Photomorphogenesis - development of certain plant parts, esp. flower initiation and development, seed germ...
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Why is light important? 1.) Photosynthesis (chl & light) 6CO 2 + 12H 2 O (chl & light) C 6 H 12 O 6 + 6O 2 + 6H 2 O 2.) Needed for chlorophyll production.
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Why is light important?Why is light important?
1.) Photosynthesis
6CO2 + 12H2O ((chl chl && light light) )
C6H12O6 + 6O2 + 6H2O
2.) Needed for chlorophyll
production
3.) Photomorphogenesis - development of certain plant parts, esp. flower initiation and development, seed germ...
Why is light important?Why is light important?
4.) AnthocyaninAnthocyanin production
5.) Light is energy! Some is converted to heat when it strikes a plant surface
6.) Light influences translocation in the plant
7.) Light can affect abscission (dropping of plant parts) when intensity suddenly changes
LightLight inintetensnsityity
-Refers to brightness
-Often the limiting factor for growing or maintaining plants indoors
Light measurementLight measurement
Light can be measured
in many ways!
- Light meter (photoelectric cell)
FootcandleFootcandle = the unit of illumination equivalent to that produced by a standard candle at a distance of 1 foot
LuxLux = the unit of illumination equivalent to that produced by a standard candle at a distance of 1 meter
ConversionConversion:
1 fc = 11.1 lux1 fc = 11.1 luxThese units measure only visible light
(what the eye can see!)
For scientific reporting of light quantitylight quantity, you might hear the following terms:
candela
lumen
photon flux
quanta
joules
1.) Natural Natural (sunlight)
2.) ArtificialArtificial (bulbs and tubes)
3.) Combination of the above
Sources of light for an interiorSources of light for an interior
SunlightSunlightFactors affecting light penetration into a
ProsPros:--diffuse light, new fixtures avail.--efficient! (7x incandescent!)--22% of energy usable light--cool! 36% of energy heat--last 8,000 - 9,000 hrs (15x longer than incandescent!)
ConsCons:--work best if 70 - 90oF- - traditionaltraditional fixtures bulky --low far-red emission--contain mercury--emit ultraviolet lightemit ultraviolet light
Cool Cool whitewhite
WarmWarmwhitewhite
Daylight fluorescent vs.
Incandescent bulb
400400 500500 600 600 700 700
100908070605040302010
0
FluorescentFluorescent
IncandescentIncandescent
Rel
ativ
e en
ergy
Rel
ativ
e en
ergy
(nanometers)
Sodium vapor lamps(HID lighting)
ProsPros:
-25-35 % of energy visible light
ConsCons:
-yellow/orange/red spectral emission only!
-large ballast (requires special lighting fixtures)
What happens when light contacts a leaf?
ReflectedReflected
Transmitted
Absorbed
Ways to increase Ways to increase artificial light:artificial light:
• Added white reflectors to fluorescent fixtures
• Paint surrounding walls white
• Regularly clean tubes to remove dust
• Regularly clean plants to remove dust
• Change tubes regularly
• Keep plants centered under fluorescent tubes
Natural vs. Artificiallight intensities
• Noon sun during summer can measure 10,00010,000 fc
• Cloudy winter day: 500-2,000 fc
• Inside rarely exceeds 1,3001,300 fc– typical office 20-30 fc
– typical living room • day: 10-1,000 fc• night: 5-10 fc
Minimum light required for plant maintainance???
100 fc100 fc
-Light quantity--Light quantity-Total light per day = footcandles of light x hours of light/day
Example:
100 fc x 16 hrs of light/day
1,600 fc hours/day
Sometimes, extending the daylength can compensate for a lower light intensity...