Muting Question #1 – Why are plants green??

I’d like to begin this series with this question because I think it reflects exactly what I mean by Muting Question.

Why are plants green? This is a classic question that even children ask. That’s not actually an easy question but, I consider it a quite widespread knowledge. Many people should already know that plants in general have thcharacteristicic green colour because their cells contain a particular molecule named Chlorophyll which is, naturally, green. A vetegetal cell, of course, can contain many other molecules for many other colours. Flavonoids, tannins, Alchaloids and many other compounds contributes to make up all the colors within a plant, from the trunk to the flower. These kind of compound can be contained in the Vacuole, a large acqueos organelle, or into other organelles called plastids (in which we find Chloroplasts in which we find Chlorophyll!). So, briefly, plants and pretty much any other botanical beings are coloured thanks to these compunds, particularly they have abundant green parts thanks to Chlorophyll, which is a fundamental part in the process involved in the Photosyntesis.

But. Yes there’s a but, that’s not my question I’m interested in answering. My actual question is Why is Chlorophyll green??

Ok, so Does this question even make sense? Well, Chlorophyll is a compound shaped by natural evolution to absorb light (which is the beginning of the Light Phase of the Photosyntesis) and it works pretty well. But, anybody who knows a little bit of physics, know that if an object appears to us coloured, it means that some part of the light spectrum is reflected by that object surface and that reflected waves bounce to our eyes. Infact, if you can see a red rose, is because the petals absorb every wave  but the red one. From that, we can say that if we see a plant green is because Chlorophyll absorb every wave but the green wave. That means that natural selection hasn’t done an optimal job in absorbing light; infact the whole process could be more efficient if Chlorophyll, or some other molecule for it, could actually absorb the whole visible light spectrum.

This graph indicates that Chlorophyll absorb pretty much nothing in the Green wavelenght, infact it reflects it. Viceversa Chlorophyll absorb very well red and blue wavelenghts, not reflecting it.
This graph indicates that Chlorophyll absorb pretty much nothing in the Green wavelenght, infact it reflects it. Viceversa Chlorophyll absorb very well red and blue wavelenghts, not reflecting it.
Chlorophyll A structure. Yes there are many kind of Chlorophyll.
Chlorophyll A structure. Yes there are many kind of Chlorophyll.

So my question seems to work, but I still had doubts. Does it makes sense to talk about evolution in this way? I don’t know. But just think of the consequences! If this could be true, all plants should be absolutely black! Not so pleasant, but more efficient!

And another question! Even if black plants couldn’t be a reality, why natural evolution would prefer the green colour over another colour?? I mean are there any difference between having a molecule that reflects only the green waves from another one that reflects only the blue waves?? I think it would be cool to have blue plants, don’t you?

What I did with my doubts is I went to my vegetal biology professor and I asked her! I did by email actually, so She aswered me only after a week. We were in classe, when she said: “Is there the Chlorophyll guy?”. I went up to her, anxious to have my answers, but she said:”You did a really good question! I had to ask some of my collegues because this isn’t my field. But literally anyone of them could answer this!!” I mean: What???

She told me that some of her collegues just stopped talking once she said the question. A retired one, actually said that in so many years of teaching He never thought about that! So here we are, this I think, is a Muting Question. I still don’t have an answer or a hint that says to me if this question makes any sense. But that’s ok, we’re scientists and that is what we do.

Do you think you know why plants are green? Come here, let me tell you a story..

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