Presentation on theme: "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."— Presentation transcript:
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 3.) Photomorphogenesis - development of certain plant parts, esp. flower initiation and development, seed germ...
Why is light important? Anthocyanin 4.) Anthocyanin 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
Light intensity - Refers to brightness - Often the limiting factor for growing or maintaining plants indoors
Light measurement Light can be measured in many ways! - Light meter (photoelectric cell) Footcandle Footcandle = the unit of illumination equivalent to that produced by a standard candle at a distance of 1 foot Lux Lux = the unit of illumination equivalent to that produced by a standard candle at a distance of 1 meter
Conversion Conversion: 1 fc = 11.1 lux These units measure only visible light (what the eye can see!) light quantity For scientific reporting of light quantity, you might hear the following terms: candela lumen photon flux quanta joules
Artificial light Supplemental to sunlight -extend hours of light intensity -increase intensity of light Sole source -role: room lighting plant lighting combination
Considerations not necessary with sunlight: spectral emission = range of colors produced by the light Light Quality!!! Artificial light 380 430 470 500 560 600 650 760 orange violet blue green yellow red indego Visible Light (nanometers) Gamma rays X-rays Ultra- violet InfraredRadio
PA RPAR) Photosynthetically Active Radiation (PAR) Range = 400 - 700 400 - 700 nanometers Based on length of each wavelength of light ~~~~~~~~~~~~~~~~~~~~ Chlorophyll blue430 red 670 Chlorophyll and associated pigments utilize light energy primarily in the blue (430 nm) and red (670 nm)
Choosing artificial lights Sources: Incandescent bulb Pros Pros: - -small - -no special fixtures - -dramatic - -range of wattages available Cons Cons: - -light is concentrated - -7% of energy usable light - -90% of energy heat! - -short life (750 hrs.) -red/orange blue -high in red/orange & low blue
Fluorescent tubes (cool-white, warm-white, daylight) Pros Pros: - -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!) Cons Cons: - -work best if 70 - 90 o F - traditional - traditional fixtures bulky - -low far-red emission - -contain mercury -emit ultraviolet light
Natural vs. Artificial light intensities 10,000Noon sun during summer can measure 10,000 fc Cloudy winter day: 500-2,000 fc 1,300Inside rarely exceeds 1,300 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 fc
-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...