<p>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 <a href="http://adsabs.harvard.edu/abs/2006AAS...209.0605S" rel="nofollow noreferrer">photosynthetic life</a>. there is actually a wide variety of photosynthetic <a href="https://ucmp.berkeley.edu/glossary/gloss3/pigments.html" rel="nofollow noreferrer">pigments</a> chlorophyll is just one of many. You may want to check out the <a href="https://en.wikipedia.org/wiki/Purple_Earth_hypothesis" rel="nofollow noreferrer">purple earth hypothesis</a>. </p>

<p><a href="https://i.sstatic.net/Z3DZY.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Z3DZY.gif" alt="enter image description here"></a></p>

<p><a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/ligabs.html" rel="nofollow noreferrer">Sauce</a></p>

CC BY-SA 4.0
2019-06-24T15:40:40.310Z
A reference for the picture should be included.
Fred
CC BY-SA 4.0
2019-06-24T17:57:02.327Z
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.
jamesqf
CC BY-SA 4.0
2019-06-24T19:09:35.593Z
@jamesqf eh. Chlorophyll is green because of its molecular structure, but the reason for that molecular structure is evolution.
Semidiurnal Simon
CC BY-SA 4.0
2019-06-24T13:49:16.820Z
2019-06-24T17:11:44.360Z
2019-06-24T17:11:44.360Z
John
<p>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.</p>

CC BY-SA 4.0
2019-06-24T10:32:31.540Z
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.
trond hansen
CC BY-SA 4.0
2019-06-24T10:43:48.033Z
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..
Michael Walsby
CC BY-SA 4.0
2019-06-30T07:02:19.470Z
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.
Michael Walsby
CC BY-SA 4.0
2019-06-30T07:32:49.997Z
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.
trond hansen
CC BY-SA 4.0
2019-06-24T08:31:57.437Z
2019-06-24T08:31:57.437Z
Michael Walsby
<p>Plants do not only come in green but chlorophyll does. The pigment in the plant creates other colored plants other then green.</p>

<p>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?</p>

<p><a href="https://i.sstatic.net/6x5AM.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/6x5AM.jpg" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-06-24T03:29:15.137Z
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 https://en.wikipedia.org/wiki/Grow_light
trond hansen
CC BY-SA 4.0
2019-06-24T07:49:46.520Z
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.
Michael Walsby
CC BY-SA 4.0
2019-06-24T17:13:56.643Z
@MichaelWalsby however this is solidly a biology question, there is no earth science component.
John
CC BY-SA 4.0
2019-06-24T17:16:29.220Z
This question belongs on the biology stack
John
CC BY-SA 4.0
2019-06-24T19:10:58.313Z
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?
Semidiurnal Simon
CC BY-SA 4.0
2019-06-24T19:40:54.730Z
As I said,you can't separate biology from earth science. Where do you think nearly all the primordial CO2 went? Where did Earth's abundant oxygen come from? Why has Earth got such massive quantities of limestone? Why is nearly all the iron in Earth's crust in the form of oxides? If you can separate Earth science from biology,you will have performed a miracle worthy of a Nobel Prize!
Michael Walsby
CC BY-SA 4.0
2019-06-25T09:05:25.773Z
@MichaelWalsby correct. You also can't separate earth science from physics and chemistry. Yet, there are questions that fit there more than here. This is the same. The people on biology.se are more likely to know the correct answer. After all, this is a Q&A website and you want answers, not demonstrate that various fields of sciences are related.
Gimelist
CC BY-SA 4.0
2019-06-25T09:23:40.357Z
Biology is not merely related to earth science,it is pivotal to understanding it.
Michael Walsby
<atmosphere><light><plant>
Why does chlorophyll only come in green?
Muze
# Why does chlorophyll only come in green?

(Asked by: username_0 on 2019-06-23)

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?

[![enter image description here](https://i.sstatic.net/6x5AM.jpg)](https://i.sstatic.net/6x5AM.jpg)

**Tags:** atmosphere, light, plant

> **Comments:**
> **username_1**: 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 https://en.wikipedia.org/wiki/Grow_light  
> **username_2**: 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.  
> **username_3**: @username_2 however this is solidly a biology question, there is no earth science component.  
> **username_3**: This question belongs on the biology stack  
> **username_4**: 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?  
> **username_2**: As I said,you can't separate biology from earth science. Where do you think nearly all the primordial CO2 went? Where did Earth's abundant oxygen come from? Why has Earth got such massive quantities of limestone? Why is nearly all the iron in Earth's crust in the form of oxides? If you can separate Earth science from biology,you will have performed a miracle worthy of a Nobel Prize!  
> **username_5**: @username_2 correct. You also can't separate earth science from physics and chemistry. Yet, there are questions that fit there more than here. This is the same. The people on biology.se are more likely to know the correct answer. After all, this is a Q&A website and you want answers, not demonstrate that various fields of sciences are related.  
> **username_2**: Biology is not merely related to earth science,it is pivotal to understanding it.  

---

## 2 answers

### Answer by username_3 on 2019-06-24. Score: 4 | Accepted answer

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](http://adsabs.harvard.edu/abs/2006AAS...209.0605S). there is actually a wide variety of photosynthetic [pigments](https://ucmp.berkeley.edu/glossary/gloss3/pigments.html) chlorophyll is just one of many. You may want to check out the [purple earth hypothesis](https://en.wikipedia.org/wiki/Purple_Earth_hypothesis).

[![enter image description here](https://i.sstatic.net/Z3DZY.gif)](https://i.sstatic.net/Z3DZY.gif)

[Sauce](http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/ligabs.html)

> **Comments:**
> **username_6**: A reference for the picture should be included.  
> **username_7**: 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.  
> **username_4**: @username_7 eh. Chlorophyll is green because of its molecular structure, but the reason for that molecular structure is evolution.  

---

### Answer by username_2 on 2019-06-24. Score: 3

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.

> **Comments:**
> **username_1**: 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.  
> **username_2**: 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..  
> **username_2**: 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.  
> **username_1**: 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.  

---

