Light in the Greenhouse

Energy Relationship of Photosynthesis and Respiration Carbohydrate Respiration Photosynthesis CO + H O 2 2 2 O 1_2 LOW HIGH Energy 2H + 2H + 2 O 1_2

Best case scenario: CO 2 levels are optimum Irrigation is optimum Available nutrient levels are optimum Optimum light intensity Too much light lowers net photosynthesis Too little light lowers net photosynthesis Actual optimum level varies, by species, growth stage location on plant

CO 2 levels are optimum

Irrigation is optimum

Available nutrient levels are optimum

Optimum light intensity

Too much light lowers net photosynthesis

Too little light lowers net photosynthesis

Actual optimum level varies, by species, growth stage location on plant

Growing Plants under Artificial Lights Intensity Duration Quality

Intensity

Duration

Quality

Light Quality Classified according to wavelength Primarily the visible spectrum of light is used for photosynthesis Don’t forget about red and far red light and the special signals provided to plants

Classified according to wavelength

Primarily the visible spectrum of light is used for photosynthesis

Don’t forget about red and far red light and the special signals provided to plants

http://www.wfu.edu/users/mcguaf1/images/PhotosynthesisActionSpectrum.gif

http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-3.htm

Maximizing Light Intensity in the Greenhouse Environment Greenhouse design Clean Glass Plant Spacing

Greenhouse design

Clean Glass

Plant Spacing

Light Intensity Reduction Frame – 10% Glass – 7% Sash Bars – 5% Overhead equipment – heaters, reflective cloth, fans, etc. Geographic orientation of greenhouse

Frame – 10%

Glass – 7%

Sash Bars – 5%

Overhead equipment – heaters, reflective cloth, fans, etc.

Geographic orientation of greenhouse

Reducing Light Intensity Spray shading compounds on the actual greenhouse (white paint and water was common) Using shade cloth

Spray shading compounds on the actual greenhouse (white paint and water was common)

Using shade cloth