I s'pose this is a variant of the age-old question, "Why are leaves green?" It's fairly easy to ask teh internets and find plenty of answers for that one.
I have a different but related question: why aren't leaves black? That is, chlorophyll varieties in leaves' cells mostly absorb red and blue wavelengths. Why isn't there a pigment in photosynthesis that absorbs green?
Instead, the green gets reflected back to the atmosphere. Its energy is otherwise lost to the plant. Nature is awfully well optimized to so many niches; why would this band of light be wasted?
There are some plants that do absorb green (and have dark leaves). These pigments -- such as anthocyanins, betalains, and carotenoids -- don't have any role in photosynthesis, and play other roles (such as protection against extreme temperature, or acting as an anti-oxidant). Am I missing some pigment in my list that is green-absorbing and participates in photosynthesis? If there were such a plant with a pigment like that, why wouldn't these plants dominate? Is there a large cost to producing the green-absorbing pigment that mostly negates the advantage of the extra energy gained?
After a little more searching on SO, I found the top answer to this question. In slightly different words, it says that light arrives in quanta, the chemistry in photosynthesis is driven by a certain threshold of energy, and any excess energy from a photon goes to waste heat (that tends to denature some of the proteins involved). The answer points to another answer with similar reasoning. However, their explanations don't account for the fact that chlorophylls strongly absorb blue in addition to red, where blue photons have nearly twice the energy of red ones.
Moreover, the answer goes on to say:
Of course, this is still no explanation why leaves are not simply black — absorbing all light is surely even more effective, no? I don't know enough about organic chemistry, but my guess would be that there are no organic substances with such a broad absorption spectrum and adding another kind of pigment might not pay off.
Are there nothing other than educated guesses at an answer? And why not use a combination of pigments, instead of a single, broad-spectrum absorbing pigment? For example, some metabolic pathways use parallel processes. Quoth the Wackypedia:
Sometimes more than one enzyme can catalyze the same reaction in parallel; this can allow more complex regulation: with, for example, a low constant activity provided by one enzyme but an inducible high activity from a second enzyme.