Why are plants leaves such a vibrant green?
Why are plants leaves such a vibrant green?
They are SO MUCH MORE vibrant than green paint.
And what about the color of the dead leaf - is it simply what you expect when you remove the chlorophyll?
Bring out the spectrometer, choose some plants, look at the sunlight
transmitted through the living leaf
reflected from the living leaf
transmitted through the dead leaf
reflected from the dead leaf
The Peach Tree
Photo 1 and 2, the Peach Tree leaves. Second photo shows the dead leaf
Figure 1, Spectra of Peach Tree leaves: alive and dead, transmitted and reflected light.
Figure 2, Peach leaves spectra, same as Fig 1, just stacked on top of each other
The Crab Apple Tree
Fig 3, Crab Apple leaves spectra, and Sun
Fig 4, Crab Apple leaf spectra, stacked
Comments
1) The question, "Why are leaves such a vibrant green" is perhaps answered by looking at the reflection spectrum, which has plenty of the Solar spectrum wavelengths. The leaf is reflecting raw sunlight, which when mixed with the underlying green gives a very vibrant color. This is especially evident in the Crab Apple tree, Fig 3 & 4.
2) The transmission spectra clearly show that the leaf takes out a wide range of blues and reds.
3) The transmission & reflection spectra have a much stronger Red-IR signal than I expected. In Fig 3 & 4 the signal from 700nm-900nm is very strong. So why don't leaves look more red?
4) That big dip at 760nm is most likely the Oxygen O2 absorption from the transition from the triplet ground state 3Σg of oxygen (two parallel spins in theπ-orbitals) to the singlet sigma excited state "1Σg" But why is it so enhanced in the the leaf compared to the Sun, in both the live and the dead leaf? Does the dead leaf really have so much molecular Oxygen in it?
5) If you remove the chlorophyll do you get the color of the dead leaf? No. It is clearly not that simple.
The Cardinal Flower
Fig 5, Cardinal Flower spectra
The Cardinal Flower spectra almost looks like the Sun minus anything less than 600nm. I say almost, because there is a clear bump 400nm-500nm, which would be adding a spice of blue to the otherwise pure red.