| Property of Light Wave | Perceived by Humans as | Units of Measure | Range Perceived |
|---|---|---|---|
| Wavelength | Color | nanometers (nm) | 400-700 nm |
| Amplitude | Brightness/Intensity | footcandles (fc) | 0 - 10,000 fc |
| What is white light? | All visible wavelengths of light together |
| In white light a leaf appears green because: | |
| it reflects | Green light |
| and absorbs | All other wavelengths of light |
Compare and contrast etiolated growth in darkness and normal growth in light (hint: your lab exercise should assist you!)
| Etiolated Growth Tall Stem Thin Stem White Stem Unexpanded Leaves Yellow Leaves Preserving Cotyledon Reserves | Normal Growth Short Stem Thick Stem Light Green Stem Expanded Leaves Green Leaves Using Up Cotyledon Reserves |
| Color of light perceived | Blue |
| Where light is perceived | Tip (apex) |
| Hormone produced at perception site | IAA (auxin) |
| Side of plant accumulating the hormone | Shaded |
| Side of plant with accelerated growth | Shaded |
| Direction of curvature growth | Toward Light |
Provide the 4th grade (one-step) reaction diagram for photosynthesis:
Now dissect this into the 8th grade (two-step) reaction diagrams for photosynthesis:
Light Reactions
Light Independent Reactions
Sketch a graph of how the rate of photosynthesis relates to the color of light. Be sure to label your axes with both name and some measurement scale with units.
Sketch another graph, this time showing how the rate of photosynthesis and respiration relate to the intensity of light. Be sure to label your axes with both name and some measurement scale with units.
The intensity of light where the two curves cross is called the _____________________________.
What is happening when a plant is kept at an intensity...
higher than this point?____________________________________lower than this point?____________________________________
This page © Ross E. Koning 1994.
Go to the Course Schedule Page.
Go to the Plant Physiology Information Homepage.
Send comments and bug reports to Ross Koning at rkoning@snet.net.