Plants do not only come in green but chlorophyll does. The pigment in the plant creates other colored plants other then green.

Could a plant grow under an alternative light spectrum like a green sun or a pure green light? Why is the green spectrum of light that of chlorophyll reflected and not absorbed?

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  • $\begingroup$ chlorophyll reflects green light as this part of the light spectrum is the least used by plants.using green light only will kill the green plants en.wikipedia.org/wiki/Grow_light $\endgroup$ – trond hansen Jun 24 '19 at 3:29
  • $\begingroup$ Yes,but the history of the Earth is so closely bound up with the history of biology (living organisms) that you can't separate the two. $\endgroup$ – Michael Walsby Jun 24 '19 at 7:49
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    $\begingroup$ @MichaelWalsby however this is solidly a biology question, there is no earth science component. $\endgroup$ – John Jun 24 '19 at 17:13
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    $\begingroup$ This question belongs on the biology stack $\endgroup$ – John Jun 24 '19 at 17:16
  • $\begingroup$ There are a few different questions in here, some of which are more about biology than earth science. Personally I'm curious to learn why plants tend to reflect (so presumably not use) the wavelengths that are strongest in sunlight... it seems counterintuitive to evolve this, unless maybe the photon energy in the green part of the spectrum isn't high enough? $\endgroup$ – Semidiurnal Simon Jun 24 '19 at 19:10

chlorophyll is green because that was the part of the spectrum that was left when plants evolved. The bulk of the spectrum was already being harvested by other photosynthetic life. there is actually a wide variety of photosynthetic pigments chlorophyll is just one of many. You may want to check out the purple earth hypothesis.

enter image description here


  • $\begingroup$ A reference for the picture should be included. $\endgroup$ – Fred Jun 24 '19 at 15:40
  • $\begingroup$ A good point, but I think it's not phrased correctly. Chlorophyll is green because of its molecular structure. The different absorption spectra of chlorophylls allowed the organisms that used them to occupy new environmental niches. $\endgroup$ – jamesqf Jun 24 '19 at 17:57
  • $\begingroup$ @jamesqf eh. Chlorophyll is green because of its molecular structure, but the reason for that molecular structure is evolution. $\endgroup$ – Semidiurnal Simon Jun 24 '19 at 19:09

To ask why chlorophyll is green is a bit like asking why haemoglobin is red. That is just the colour of them, in the case of haemoglobin due to the iron content and in the case of chlorophyll probably due to the magnesium atom at the centre of every chlorophyll molecule. As you very likely know, the function of chlorophyll is to carry out photosynthesis, using the magnesium as a catalyst, splitting water into hydrogen and oxygen, then combining the hydrogen with CO2 to create carbohydrates (sugars in the first instance) and more oxygen. The energy source for this process is light, but only light of certain wavelengths will do. Green light isn't up to the job, so it is reflected. There are no green suns, though most stars emit some green light. Whether in other solar systems plants have evolved to use different wavelengths of light than the ones used on Earth is something we can never know, but I think it's unlikely.

  • $\begingroup$ if life exist out there it is most likely around a red star,they are more stabile over time giving life the time needed to evolve and survive. $\endgroup$ – trond hansen Jun 24 '19 at 10:32
  • $\begingroup$ I think stars like our sun are more likely to evolve life on their planets,but at this stage we can't rule out that red stars can do it too,but more likely large red stars rather than red dwarfs. I'm pretty sure that Earth is not the only planet in the galaxy to haver life on it,or even intelligent life,and our galaxy is only one of billions,but I doubt if we'll ever know for sure.. $\endgroup$ – Michael Walsby Jun 24 '19 at 10:43
  • $\begingroup$ When I said large red stars are more likely to evolve life than small ones. I meant the largest type of red dwarves, sometimes called orange dwarves. I didn't mean red giants. $\endgroup$ – Michael Walsby Jun 30 '19 at 7:02
  • $\begingroup$ and i did not mean a star at the end of its life but stars that are long lived and have a low radiation in the uv x-ray and gamma spectrum. $\endgroup$ – trond hansen Jun 30 '19 at 7:32

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