View
215
Download
2
Tags:
Embed Size (px)
Citation preview
Greenhouse Management
Light
2162Adam Nash
PHOTOSYNTHESIS
CO2 + H2O + Light Energy C6H12O6 + O2
•Complex Carbohydrates•Proteins•Fats
•Takes place in the Chloroplast
Light Quality
• Visible Wavelength– Visible light is between ~ 400 - 700 nm
• Wavelength vs. Energy
Shorter Lower
Longer Higher
Light Spectrum
Photosynthesis Uses Mostly Blue and Red light (reflects green) Visible Light
• Violet• Blue• Green• Yellow• Orange• Red
Light Intensity 3,000 foot-candle will saturate most
greenhouse plants 10,000 foot-candle needed to saturate
lower levels of canopy Midwest Light Levels
• 10,000 summer midday• 500 winter midday
Maximizing Light Intensity Metal framework Wider frame spacing Paint wooden frames white Choice of covering material Clean glass Wider plant spacing
Supplemental Lighting To increase light intensity To control photoperiod
Moving Supplemental Lights
Types of Lights Incandescent
• High heat, low efficiency, high red, low blue Fluorescent
• Expensive, less heat, low power, high blue
Photoperiod Response of a plant to the day/night cycle Can measure a difference of 5 min in 24 hrs. Controls:
• Bolting in lettuce• Bulbing in onions• Tuber formation in dahlia• Poinsettia bract coloration• Flowering in Mum• Etc., etc., etc.
Did you see a commonality among the examples on the previous slide???
Reproduction
Plant Categories Short-day plants Long-day plants Day-neutral plants
Short Day Plants(long night plants)
Typically initiates reproductive behavior when day length drops below 12 hours
Long Day Plants(short night plants)
Typically initiates reproductive behavior when day length exceeds 12 hours
Modifying Day Length
To create a short day / long night• Example: Poinsettias• Use black-out cloth (note: a flashlight provides
enough light intensity to create a short night) To create a long day / short night
• Example: for vegetative growth on young mums• Turn on light for a few hours in middle of night
Adding Light Also Means… Higher Intensity Light
• High Photosynthesis Rate In Greenhouse High Intensity Light
• Higher Temperatures• Lower Humidity• Causes More Transpiration
Use More Water
Temperature Effects OnNet Plant Growth
When rate of photosynthesis exceeds the rate of respiration, net growth occurs
When rate of photosynthesis equals the rate of respiration, no growth occurs
When rate of photosynthesis is less than the rate of respiration, plant growth declines
(Cooler nights are used to reduce the rate of respiration to ensure net plant growth)