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/sci/ - Science & Math

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6034477 No.6034477 [Reply] [Original]

>ask why plant's leaves are green
>"it's because of Chlorophyll, stupid"

This answer frustrates me. It is like asking why someone's car is pink, and then getting the answer "because of the pink paint, stupid".

I am not scientifically minded, so please explain to me why plants are green. If I was born blind, and someone described to me how plants work, I would assume their leaves would be black. Why is the colour green reflected, and not absorbed?

Why are black leaves so uncommon compared to green leaves? I would assume that the plant with the most efficient leaves (black leaves) would out-compete those with colourful leaves who reflect most of the light spectrum.

>> No.6034479

clorophyll absorbs light in a range that doesnt include green.
You can only see green because the rest has been absorved

>> No.6034480

>>6034479
Wouldn't it have been better if all light was absorbed including green?

>> No.6034482

>>6034477
>I would assume that the plant with the most efficient leaves (black leaves) would out-compete those with colourful leaves who reflect most of the light spectrum.

They probably would, if such a thing ever developed. But it never did. Evolution has a lot of momentum, and chlorophyl is very ancient and very fundamental. You couldn't change that molecule without changing all sorts of other stuff.

>> No.6034488
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6034488

>Plants 'seen doing quantum physics'

http://www.bbc.co.uk/news/science-environment-22996054

>> No.6034492

>>6034477

most plants form endosymbiotic relationships with colonies of cyanobacteria-like things called chloroplasts. cyanobacteria have been around for around a billion years now or something, and they've always been green and they've merged with plants much later.

chloroplasts or cyanobacteria work by absorbing sunlight, converting co2 and a photon into sugars and energy molecules. actually they use the heat generated by a photon as it's absorbed in the chlorophyl. chlorophyl is a pigment. a lot of pigments would probably work, but green is probably the first to have evolved and worked successfully. since you don't need to fix what isn't broken, mutations into other colors were phased out by incompatibility, and as such flowers remained green

I have a phd in women's studies.

>> No.6034494

>>6034492
>I have a phd in women's studies.

I guess thats why you think flowers are green.

... i kid.

>> No.6034499

Well I found the magazine that had different color plants based on the type of star, but it's taking forever to download.
Scientific American, April 2008
It's the cover story.

Anyone have a good source for magazines like the awesome sources for books?

>> No.6034509

>>6034492
This is a pretty good explanation, however these cyanobacteria haven't always been green.

Before the ancestors of the green plants we now have on earth, the seas of the world were filled with purple cyanobacteria. We had a purple earth, rather than green or blue.

I'm unsure how these purple cyanobacteria died out, but eventually the green variety took over, mainly due to their ability to take up CO2 and photosynthesize, an ability that the purple variety did not have. This was important because at the time the earth was very CO2 dense.

I watched something a while ago on this but am fuzzy on the details, check out "BBC How to grow a planet, Episode 1, Life from Light".

>> No.6034526

>>6034499
I'm sure the evolutionary patters of life would be different on another planet.

>>6034492
Most leaves also contain carotenoids such as xanthophyll, which is yellow. However they are usually out-shinned by the large amount of chlorophyll in the leaves. Remember, there are 2 different types of chlorophyll that absorb different wavelengths, so chlorophyll is good at what it does.

3 year art history major.

>> No.6034532

>>6034492
>I have a phd in women's studies.
w-why

>> No.6034535

I enjoyed that post very much.

I have an emeritus in origami

>> No.6034541

>>6034492
I think a phd in noose making would be more useful.

>> No.6034539

it's green because that's the most efficient color for absorbing the type of energy it does from the sun
if plants were black they'd get too hot

>> No.6034544

>>6034480
probably, but that is not how plants evolved.

>> No.6034558

>>6034541
You think that's something?
I am doctor honoris causa in plumbing.

>> No.6034578

>>6034480
It's not that the plant needs to capture more photons, it's that the plant needs to capture the right wavelength of light to excite the chlorophyll molecule. Capturing red and blue light is good enough for what the plant needs to do.

Perhaps a better way of asking the question is, "why does chlorophyll capture the wave lengths that it does?"

The only way that carbon-based life forms can capture energy from light is by synthesizing pigments with conjugated double-bond networks. While ultraviolet contains a lot of energy per photon, it cleaves many covalent bonds between carbon and other atoms, and it requires very short conjugated networks (dienes) to be captured. On the other hand, IR radiation does not carry much energy and it would require extensive, complicated pigment molecules to capture (altough some bacteria that live underwater do capture IR light because it penetrates farther than visible light). Blue light, captured by chlorophyll, is a good wavelength to capture because it's the shortest wavelength that won't rapidly destroy the pigment molecule.

>> No.6034584

>>6034526
yeah...but they needed a comparison so they talk about which wavelength is dominant from the sun...

>> No.6034627
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6034627

I seem to recall it also had something to do with insects seeing only in deep-red/near IR, and in those wavelengths green looks black. And so this is why there's no green flowers, because the flowers need to be a different color than the rest of the plant to attract insects. To pollenate, you see.

Concurrent evolutionary biology or something, IIRC.

I could be totally wrong though.

>> No.6034648

Leaves don't have a color. No matter does. Color is just the way our brains interpret the electromagnetic stimulation in our retina.

*Most* leaves have a much higher concentration of chlorophyll in their chloroplasts (an organelle present in plant cells but much more prominent in the tissues of leaves) than other "pigment" compounds plants use for photosynthesis.

>> No.6034656

>>6034648
>phenomenon X doesn't exist
>describes phenomenon X in the next sentence

For the sake of your sanity and everyone nerves, you need to stop fucking doing that.
Describing something doesn't strip it of its existence.

Also your answer is shit and you could have at least read the thread.

>> No.6034664

>>6034648
Aw crud, I posted that half explained. Chlorophyll absorbs a wide range of frequencies of visible (what we see as color) electromagnetic waves except for a certain band that instead gets refracted. When that band of light waves reaches us they appear as the color green.

Why is the range of green not used for photosynthesis as well? Here's what I know:
Plants DO have some pigment molecules that absorb green light, but they are usually in much lower concentration than chlorophyll, that is largely due to plants evolving from green algae. Chlorophyll is also really good at absorbing higher frequencies of VL (more energetic) than the other pigment molecules; even if green itself is more in the middle in terms of frequency.

>> No.6034671 [DELETED] 

>>6034656
No, it's actually
>Phenomenon X is an attribute of A, but rather of B

>> No.6034672

>>6034656
No, it's actually
>Phenomenon X is not an attribute of A, but rather of B

>> No.6034680

>>6034672
>Color is the way our brains interpret the electromagnetic stimulation in our retina.
that's the definition of color

>> No.6034688

>>6034680
Glad you agree with me then. :)

>> No.6034696

>>6034688
so leaves have color, because our brain interprets the light reflecting off them

>> No.6034726

>>6034696
Sure anon, so does CO with the right equipment. In fact it can be any color we want it to be... as long as that color that represents CO is a wavelength shot from a screen our eyes can perceive. My point is color is something in our heads. Some matter just has the ability to pop up as colored in our eyes. If the differentiation I make doesn't matter to you, that's fine.

>> No.6034738

>>6034726
There is no "differentiation" to do. The word implies you would be comparing two different things.
"Objects don't have a color because I call 'having a color' something completely nonsensical" is not a smart statement.

>> No.6034864

>>6034738
Saying that color is a creation of our mind is very different from just saying that x thing has color. Color doesn't exist outside our mind, unlike air compression or matter propagation.

>> No.6034873

>>6034864
Oh ok you're just being dense.

>> No.6034881

>>6034873
And you like having the last say even if it's just an Ad hominem.

>> No.6034911

>>6034656
To be fair, a lot of Professors do this as well. Even more annoying is when they give an incorrect description of the fundamental phenomenon so it sounds like the higher level interpretation is incorrect (Analytical Chemists should just never mention QM).