
Why Are Plants Green? To Reduce the Noise in Photosynthesis - theafh
https://www.quantamagazine.org/why-are-plants-green-to-reduce-the-noise-in-photosynthesis-20200730/
======
raxxorrax
Some trees and plants that are still rebellious about this:

[https://www.ornamental-trees.co.uk/images/cercis-
canadensis-...](https://www.ornamental-trees.co.uk/images/cercis-canadensis-
merlot-p1128-7419_image.jpg)

Of course those also have chlorophyll, but the color is overridden by other
color particles.

Sadly we have no blue trees. We have blue flowers though and it would probably
be possible to create one. That would be so awesome.

~~~
tipoftheiceberg
The only blue flowers we have are dyed.

We do not know of any “true blue” plant pigments. There are violets and many
colors that might look close..

~~~
irrational
What? I have a bunch of hydrangeas in my yard right now that range from light
to dark blue. They are definitely not violet or any other close blue color.
They are as blue as blue can be. And they haven’t been artificially tampered
with. We planted them 15 years ago and have done nothing for them since. Not
even fertilizer.

~~~
tipoftheiceberg
Those plants that do appear blue are in fact often using a red pigment known
as anthocyanin. Through pH shifts and a mixing of pigments, combined with the
reflection of natural light, the plants are able to generate the appearance of
a naturally occurring, blue color. That's the reason why plants such as
bluebells, hydrangeas and morning glories appear various shades of blue, when
in fact, as Lee explains, "There is no true blue pigment in plants."

~~~
irrational
What does it matter whether they have blue pigment or not? If nearly every
person looks at it with their own eyes and say, "That is definitely blue" then
it is blue. I don't care why or how it is blue. Anything else is just
pedantry.

~~~
Green_man
Some of the "blues" generated in nature rely on specific physical structure or
other tricks to appear blue. This means they reflect predominantly blue light,
but may not retain that "blueness" when ground/processed into a pigment.
That's one reason there are few natural organic blue pigments, even the
ancient Egyptians relied on chemical solutions for "Egyptian Blue".

[https://en.wikipedia.org/wiki/Blue#Pigments_and_dyes](https://en.wikipedia.org/wiki/Blue#Pigments_and_dyes)

Interestingly, the one dye listed in the link above that came from a plant is
indigo, which is extracted from the green leaves of the plant
[https://en.wikipedia.org/wiki/Indigofera_tinctoria](https://en.wikipedia.org/wiki/Indigofera_tinctoria)
. There's no animal or plant I know of that both appears blue and could be
used to create even a poor blue pigment, though I'd definitely be interested
in any exceptions I haven't heard of.

[https://www.youtube.com/watch?v=3g246c6Bv58](https://www.youtube.com/watch?v=3g246c6Bv58)

~~~
thangalin
* [https://www.sciencedirect.com/science/article/abs/pii/030504...](https://www.sciencedirect.com/science/article/abs/pii/0305049189900904)

* [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5444072/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5444072/)

* [https://www.jstage.jst.go.jp/article/fishsci1994/61/6/61_6_9...](https://www.jstage.jst.go.jp/article/fishsci1994/61/6/61_6_964/_pdf) \-- see figure 2 on page 4, showing extracted carotenoproteins

~~~
Green_man
Thanks, this is really interesting stuff!

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russfink
Why wouldn't fluctuations of sunlight that cause instability in the green
spectrum also cause instabilities in the red and blue spectra?

~~~
uj8efdkjfdshf
I think the point is that since the power available at these wavelengths vary
sharply with frequency in these regions of the solar spectrum, the plant can
easily compensate for brightness fluctuations in these portions of the
spectrum with minor tweaks to the target wavelength of the relevant
photosystems

~~~
Sniffnoy
I'm confused though -- how can the plant possibly vary this?

~~~
danbruc
In principle plants have several different variants of the light absorbing
molecules with different absorption spectra but I don't know how this would
actually be regulated. But it is certainly imaginable that plants vary the
relative abundance of the different light absorbing molecules or their
efficiencies and this could be more or less automatic because of varying
conditions like pH or whatnot that affects efficiency or lifetime of the
molecules with a simple feedback mechanism or it could be actively regulated
by a more complex feedback loop.

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odomojuli
The color of plants and the statistics of light is fascinating.

Tangentially related, I was developing a CV app for farmers in an early stage
weed startup right before legalization in California so they could monitor
analytics on the health of their sprouts as well as identify strains. The
camera conditions were all over the place and data preprocessing stage was an
absolute nightmare. We tried everything from filters to background removal,
augmentation techniques through transformations, noise induction for
generalization - nothing really improved the baseline models because the
photos honestly sucked. Farmers ignored our guidelines on lighting and framing
and format and kept sending in inconsistent garbage.

I had a eureka moment. What if we sent each of the farmers a little piece of
square cardboard painted magenta? The idea was that the increase in contrast
would allow us to process the leaf contour a little bit better. The fact that
the card was square meant some farmers even took the time to take the plant
indoors so they could frame it better within the edges. Data quality improved
dramatically. It worked.

Unfortunately legalization did not work out as we planned, farmers disappeared
and the market was monopolized by corporations, there wasn't any interest in
helping develop strains locally.

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rkwasny
Related, one of my favourite videos: Richard Feynmann explains fire:

[https://www.youtube.com/watch?v=N1pIYI5JQLE](https://www.youtube.com/watch?v=N1pIYI5JQLE)

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throwaway_USD
My understanding of the evolution of Earth flora is that prior to plants being
green, the dominant plant life was red (think of red algae blooms) and that
the current dominant green plant life likely evolved to use different photons
along the EM spectrum where there was less competition.

Funny enough as I understand visible light and the EMR spectrum there is no
"green" (color/wave length/energy) rather the color green is a construct
originating not in the light spectrum but in the mind of the observer.

~~~
Zaak
There is a range of wavelengths of light that humans perceive as green. The
same is true for every color that is part of the rainbow. In contrast, the
"pure purples" do not appear in the rainbow, and there is no single wavelength
of light that humans perceive as purple (it requires red light plus blue
light).

~~~
Balgair
The perception of color is a pretty wild area of science. Colors seem to be
culturally dependent. In that, people literally cannot see the difference
between blue and green if their language does not have words to distinguish
them. Even when big rewards are given for the 'correct' answer. Colors also
follow certain patterns, with colors like blue being the last to be named in a
culture.

[https://www.youtube.com/watch?v=gMqZR3pqMjg](https://www.youtube.com/watch?v=gMqZR3pqMjg)

Fun fact, the color blue does not appear at all in the _Iliad_ , Homer
describes the ocean as wine, despite the stunning blue colors of grecian seas.

~~~
Aengeuad
>In that, people literally cannot see the difference between blue and green if
their language does not have words to distinguish them.

People literally _can_ see the difference between blue and green even if their
language doesn't differentiate between the two, I don't know if you're
misremembering a claim and a negation sneaked in so please don't take this
post too harshly if that's the case, but the idea that say Japanese people
can't tell the difference between blue and green is patently false and should
be addressed, in fact the video you linked almost does so at 2:34 -

>Some researchers took this and other ancient writings to wrongly speculate
that earlier societies were colour blind.

That Homer described the ocean as wine in colour is not an issue of perception
but one of language in trying to describe a colour that is not differentiated
from other colours, the same is true for other 'perception' issues in the
ancient world like green coloured honey. To be clear visual acuity tests have
been done on modern populations and tribes which don't differentiate between
such colours or overall define less colour categories and it should be no
surprise to learn that they can see the difference between those colours just
fine.

The whole idea that it's a difference in perception is fraught with issues,
like what happens when a language naturally develops words for new categories
of colours or new colours? Does a generation undergo the collective experience
of literally being able to see/differentiate a new colour? If so why isn't
this written about more, is it something that only happens in kids? What would
be the reason for this sudden shift in perspective, because it certainly isn't
a physiological change that occurs.

What happens when an adult learns a second language which differentiates
between more colours? The classic romanticised view here is that learning a
new language _literally_ let's you see the world in a different perspective,
but then why is it that enhanced perspective rarely more than a curiosity
(language x has two words for this colour)? The Russian language has separate
words for a dark blue (siniy) and a light blue (goluboy) but English doesn't
differentiate between them, do the Russians see an extra colour? What does the
science say? Well the science is somewhat interesting here, Russians are able
to differentiate between dark blues and lighter blues ever so slightly faster
(124ms), but this is worlds apart from the claim that some languages are
_literally_ capable of seeing more colours.

In general this line of thinking is known as linguistic relativity, or the
view that language shapes perception and cognition, and is something that has
generally been discredited among linguists as being discriminatory and harmful
as well as being based on faulty reasoning or studies and occasionally
fraudulent papers. For example, and I really don't mean to attribute any
malice to your post, but if we're considering Homer as being unable to
differentiate between an ocean blue and a dark red wine, what do we make of
cultures and languages that don't differentiate between smoking, drinking, or
eating? Do they not know the difference between those actions? What about the
Pirahã people who only have two words (differentiated by tone) for 'small
quantity' and 'large quantity' and no other words for numerals? This line of
thinking is fairly harmless when applied to the way we perceive colours but
can be actively harmful to people who perceive the world the exact same way we
do but don't have as expressive language for these particular topics.

For anybody interested in more linguistic oddities and/or the damage
linguistic relativism can do I recommend the book 'The Language Hoax' by John
McWhorter, there's also an hour long talk on it available on Youtube [0]. The
book deals with the more recent studies on how language affects the ways we
think in a grounded way and shows how minor some of the best examples given
can be like in the case of dark and light blue in Russian. The book is also in
response to the general public's view and romanticism of linguistic relativity
and in particular in response to a book by another linguist Guy Deutscher
titled 'Through the Language Glass', where Guy feeds into the perception that
language helps shape the way we think, and it is a good book but it still
doesn't get close to saying that other languages see more colours.

[0] [https://www.youtube.com/watch?v=yXBQrz_b-
Ng](https://www.youtube.com/watch?v=yXBQrz_b-Ng)

~~~
sergeykish
There is no need to travel to jungles. Subtle differences are all around us.

* plants - trees, grasses, flowers, native and garden species, once I knew maybe 400 names, now come to disuse and quickly slip away

* food - ingredients and prepared

* fonts - Comic Sans, Times New Roman, Helvetica and many more

* car models - a lot of people know them by heart

It would be a strange claim we do not perceive difference without a name. We
do but we do not care. And when we care we want to communicate and names
become handy.

------
cortic
I was really looking forward to reading this but its a bit of a
disappointment.

First, green does not have the most energy of the visual spectrum, Blue, or
more specific Violet does;
[https://socratic.org/questions/5348556b02bf347bedff8fed](https://socratic.org/questions/5348556b02bf347bedff8fed)

Second the noise difference from 10% of the green would be negligible compared
to the energy we are talking about. Also _how_ does a plant regulate this
'noise'? The only logical explanation would be expand into the green in dark
and out of it in light, but they have shown no mechanism for a plant to do
that.

Sorry to say that after that fairly long winded article i have come to the
conclusion we still don't know exactly why plants aren't all black.

Edit; Thinking about this more, maybe Chlorophyll a and Chlorophyll b take
inverted wavelengths of light to produce a rectification effect..? Its
interesting, but even if that were true, it would not explain the gap at
green.

2nd Edit; I stand corrected, considerably more green light make it through the
atmosphere thank you for the information spacemark.

~~~
alanbernstein
The "most energy" statement isn't about the frequency of light, it's about the
power output of the sun, which peaks around green.

~~~
jiehong
That power output really is the area under the curve, in which case most of
the sun's energy is in the infrared, actually.

~~~
alanbernstein
Sure. But the peak is around green, which is the point of the article and the
answer to parent's question.

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stpedgwdgfhgdd
The same applies to software development; local optimization does not weigh up
against stability across the entire supply chain.

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hawktheslayer
I might just use this trick of nature to inform how I manage my staff at work.
We spend so much time trying to maximize efficiently, but perhaps at the cost
of stability.

~~~
deeweebee
This is the nerdiest sentence I’ve seen today. Dang!

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Chris2048
But, why do plants need a regular amount of light energy? Can't a black plant
just absorb everything available?

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zadkey
Why are some plants purple like tradescantia pallida?

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jonplackett
I always just assumed there wasn't much green light, so plants optimised for
the rest of the spectrum:

The sky is blue, the sun is orangey.

Where's all this green light I'm missing?

~~~
colanderman
The sun is actually green (that is, is approximated by a black body emitter
with a peak in the green region of the visual spectrum, see [1]). Its light
appears white because that is how we are conditioned evolutionarily. ("True"
white -- i.e. equal spectral energy -- appears blue-grey to us.)

The sun "looks" orange because when you _can_ look at it (sunrise/sunset), its
light is heavily filtered by the atmosphere.

[1] [https://qph.fs.quoracdn.net/main-
qimg-f9bc312e4d114e9e32a627...](https://qph.fs.quoracdn.net/main-
qimg-f9bc312e4d114e9e32a62714c36580aa)

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SeriousM
Finally a clickbait with explanation!

~~~
42droids
Wanted to say the same.

~~~
42droids
Ppl who downvote comments like these are responsible for killing any joy and
fun on the internet.

~~~
hutzlibu
Your fun and joy definition might not meet the definition of others. I for
example do not enjoy metoo comments. If you do, you are likely a minority.

~~~
IncRnd
You started off well, but you ended with a logical fallacy.

~~~
hutzlibu
Why? I shared my experience. Allmost no one I know enjoys these comments.
Wheres the fallacy?

~~~
IncRnd
You started out sharing your experience, yes, but that was not your last
sentence. The fallacy is fallacy of composition, one of the forms of illicit
transference. Another way to phrase that is you formed a hypothesis that you
assumed to be true.

~~~
hutzlibu
That sounds a lot like talking around to me. Can you say concretely, where you
believe my fallacy is?

~~~
IncRnd
> That sounds a lot like talking around to me. Can you say concretely, where
> you believe my fallacy is?

How is that talking around?

I literally told you where your fallacy resides in your words. Then, I labeled
the exact fallacy, providing two common names for the fallacy. Finally, I
provided a simplistic rephrasing of the fallacy to help with your
identification. What else do you need?

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dvh
I thought plants are green because sun is green. Edit: not sure about down
votes, sun has peak in green spectrum. Our eyes are most sensitive to green,
plants are green to utilize it as well.

~~~
laszlokorte
If they would utilize the green light they would not reflect it - so should
exactly not be seen as green by your eyes.

