1. Light & Photosynthesis
IAFNR Plant and Soil Sciences Module

2. The Nature of Light Form of radiant energy that travels in waves
Wavelength-the distance between each crest in a wave
White light is within the nm wavelength
White light is made up of the colors: red, orange, yellow, green, blue, and violet
Ultraviolet and Infrared light are at the ends of the visible spectrum of light show below
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3. The Nature of Light Light can be absorbed or reflected
Ex. A dark color absorbs light and this energy becomes heat energy (wearing a black shirt on a very sunny day)
Photosynthetic organisms have a pigment called chlorophyll that traps light and makes it into energy
Plants appear green because chlorophyll reflects green light
Red, Violet, and blue wavelengths are absorbed as energy
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4. Sunlight Sunlight is like white light which contains all colors
Duration of light, and intensity varies with location and time of the year
Earth revolves around sun, length of day and intensity of light changes
See diagram below
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5. Why is green light least effective?
Artificial Light
Incandescent light and fluorescent light are common sources of artificial light
There are also special lights designed for growing plants
Colored light
Red and Blue light have greatest effect on growth
Green is least effective
Why is green light least effective?
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6. Photoperiodism Plant response to length of daylight
Plants are separated into
Long-day
Short-day
Day-neutral types
Main response of plants is flowering
Plants need the correct length of uninterrupted light
Also need a dark period for flowering
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7. Plant Structure for Photosynthesis
Thylakoid- where photosynthesis occurs
Stacked up like pancakes inside the chloroplast
Chloroplast- organelle that contains chlorophyll
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8. Step by Step Photosynthesis

9. Let’s Break it Down…
Photosynthesis processes three things within the plant
Transforms light energy from the sun into chemical energy
Carbon from CO2 is made into solid form
Produces oxygen- OUR FAVORITE!!
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10. Factors Affecting Photosynthesis
Light Quality- chlorophyll reacts to light in blue and red wavelengths
Light Intensity- brighter light allows for best photosynthesis
Light Duration- longer day allows for more photosynthesis
Carbon Dioxide Concentration-co2 is required for photosynthesis
Usual atmospheric concentration is 0.03
Temperature- photosynthesis increases with temperature
Water Availability-plants that lack water will close their stomata

11. References
Parker, R. (2010). Plant and Soil Science: Fundamentals and Applications. Clifton Park, NY: Delmar.
Green, H. & Green, J. (2012). Photosynthesis: Crash Course Biology #8. Retrieved from: