I want to compare the "energy amount"/ calories of leaves when they are turning different colors so does a green, yellow, or red leaf of the same tree have more calories? I know that different color wavelengths of light correspond to different amounts of energy, but does the color also correlate to different amounts of energy?
Answer from Posse Member Dave McKenzie:
"Does a green, yellow, or red leaf of the same tree have more calories?"
This is a valid question that could be answered if the student had access to a bomb calorimeter, which measures the number of calories in a sample by burning it. The caloric content in the leaves of different colors likely would change because the chemical composition of the leaves is changing with different colors. The appearance of red/orange/yellow is the manifestation of the reduction of chlorophyll concentration in the leaf that allows those other colors (chemicals) to be seen. They are always there, but the chlorophyll (green) covers them up. Chlorophyll provides certain chemicals that the other compounds do not. Therefore, the caloric content would change just as it does when we alter the chemicals in our own food (although the use of the word ‘calorie' is slightly different). I do not know of a way to test the caloric content of leaves without a calorimeter. I would expect that green leaves have the highest calorie content because they have the most ‘stuff' in them (chlorophyll). Many species pull materials out of leaves in the fall to reuse next year.
"Different color wavelengths of light correspond to different amounts of energy, but does the color also correlate to different amounts of energy?"
The actual color of the leaf has nothing to do with the caloric (energy) content of the leaf. The color of the leaf is simply the light that is reflected (green/yellow/orange/etc) from the full spectrum after other wavelengths have been absorbed (blue/violet/etc). The amount of energy hitting the leaf (this time measured in photons) changes with season because of the orientation of the earth. The amount is not affected by the material it hits. We must separate these two forms of energy. Photons are emitted from the sun and absorbed by the leaf. The leaf then uses that photon energy to convert raw materials to plant matter. It is the plant matter that is measured in calories. I should return to my first sentence in this paragraph. The energy content of the leaf would vary in terms of calories, but this is not a direct result of color. It is a result of chemical composition (which also affects light reflection and thus, color).
I hope this answers your questions. If you need some follow up or clarification, please let me know.