What color absorbs more light and heat, black or green?

[Winterblues]

Most people would say black absorbs heat and light more than anything but if that is the case why is most vegitation green?

[Occam Bandage]

1. Because sunlight is not pure white.

As such, plants can maximize their benefit by targeting the wavelengths that have the highest benefit-to-cost ratio.

[Winterblues]

2. White reflects sunlight but black absorbs it.

Why is everything green?

[Occam Bandage]

6. Right. Black is the absorption of all wavelengths.

The "green" we see is because plants absorb blue and red wavelengths, which are the most abundant. No sense evolving the ability to absorb the relatively small amount of green light the sun gives off.

[tridim]

Although I've certainly seen plants that have almost black leaves.

But that usually occurs late in the growing season when all the wavelengths are reduced.

[Ian David]

28. And poinsettia leaves turn red around xmas time, IIRC. n/t

[Bill McBlueState]

13. but the solar spectrum peaks in the green

The sun's temperature is 5780 K, so according to Wien's Law, its spectrum should peak at 2900/5780 = 0.5 microns, which is basically green. The sun gives off more green light than any other color.

[Ian David]

3. Plants don't need heat. Heat is infrared. Photosynthesis requires ultraviolet. n/t

[Winterblues]

4. Why is it then most plants quit growing under forty degrees?

:shrug:

[Ian David]

5. Not all plants. There are algaes that live in the ice.

But you make a good point. I should have been more specific.

The primary reason plants are green isn't so they can absorb heat. It's so they can absorb ultraviolet energy for their green chlorophyll to photosynthesize.

But yes, plants can freeze to death.

See also:

Biology, Answering the Big Questions of Life/Photosynthesis
http://en.wikibooks.org/wiki/Biology,_Answering_the_Big_Questions_of_Life/Photosynthesis

Why are plants green?
http://answers.yahoo.com/question/index?qid=20090318061833AA0eqXE

Why are plants green?
(Lansing State Journal, August 14, 1996)
http://www.pa.msu.edu/sciencet/ask_st/081496.html

[TahitiNut]

11. Interestingly, one could observe that if chlorophyll were white then plant life could not have ..

... evolved. :shrug:

[csziggy]

40. For a recent in depth discussion of what plants might be like on other worlds under other stars

The Scientific American article "The Color of Plants on Other Worlds" is great:

Key Concepts

* What color will alien plants be? The question matters scientifically because the surface color of a planet can reveal whether anything lives there—specifically, whether organisms collect energy from the parent star by the process of photosynthesis.
* Photosynthesis is adapted to the spectrum of light that reaches organisms. This spectrum is the result of the parent star’s radiation spectrum, combined with the filtering effects of the planet’s atmosphere and, for aquatic creatures, of liquid water.
* Light of any color from deep violet through the near-infrared could power photosynthesis. Around stars hotter and bluer than our sun, plants would tend to absorb blue light and could look green to yellow to red. Around cooler stars such as red dwarfs, planets receive less visible light, so plants might try to absorb as much of it as possible, making them look black.

http://www.sciam.com/article.cfm?id=the-color-of-plants-on-other-worlds

[tridim]

7. Most plants reflect green and absorb red yellow blue and uv

Because those are the wavelengths that are used for photosynthesis.

[marketcrazy1]

8. did you forget EVRYTHING you learned in grade school!

Photosynthesis

Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. This process occurs in plants and some algae (Kingdom Protista). Plants need only light energy, CO2, and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts, specifically using chlorophyll, the green pigment involved in photosynthesis. Photosynthesis takes place primarily in plant leaves, and little to none occurs in stems, etc. The parts of a typical leaf include the upper and lower epidermis, the mesophyll, the vascular bundle(s) (veins), and the stomates. The upper and lower epidermal cells do not have chloroplasts, thus photosynthesis does not occur there. They serve primarily as protection for the rest of the leaf. The stomates are holes which occur primarily in the lower epidermis and are for air exchange: they let CO2 in and O2 out. The vascular bundles or veins in a leaf are part of the plant's transportation system, moving water and nutrients around the plant as needed. The mesophyll cells have chloroplasts and this is where photosynthesis occurs.

[Occam Bandage]

9. That does not answer the question, which is "why did plants not evolve

the ability to absorb the energy in all wavelengths of light?"

[Ian David]

10. Why didn't you evolve to photosynthesize?

All that sunlight hits your body every day, and what do you do with it?

Yeah, you make some vitamin D, but mostly it just gives you skin cancer.

[TahitiNut]

12. Because I live in a cave.

:dunce:

[Soylent Brice]

30. hooray for green ray frightened cave dwellers!!

lol

[Occam Bandage]

15. Because high oxygen levels interfere with photosynthesis,

and I am the descendant of an evolutionary line that uses oxygen to strip the delicious energy that others produce.

[Ian David]

18. Hey, no sex threads. n/t

[KittyWampus]

24. Wait! Who says we don't do anything else with sunlight? It affects our moods and hormones

which in turn affect our immune system.

Sunlight and how much we get also affects our biological clock.

So sunlight plays a greater role than just Vitamin D and sun cancer.

Take Chrysanthemums, they set buds and flower according to not just temperature (like a Christmas Cactus) but also according to HOW much light they get. If you grow chrysanthemums under a street light that gives them too much extra light in the fall, they won't flower well.

[Ian David]

26. My point is that your body expends more effort defending itself from sunlight...

... than it does using it.

And instead of harvesting all that energy, we instead sweat our precious bodily fluids out of our skin in an effort to mitigate its impact.

[KittyWampus]

29. ah, but sweating our precious bodily fluids helps rid ourselves of toxins

:)

Just having fun talking about a fun topic.

[Ian David]

34. Why are you so intent on robbing me of my precious bodily fluids?

You sense my power and seek my essence.

[KittyWampus]

35. I just like arguing with you. It gets my blood up

;)

[Ian David]

36. Did you want the five-minute argument, or the course of ten? n/t

[kimmerspixelated]

43. Especially true if you pour on mainstream sunscreen

laden with toxins!

[marketcrazy1]

20. that was not the question

this was the question "What color absorbs more light and heat" and the answer is "black" that color absorbs most of the light spectrum including infra red. as to why plants are green, chlorophyll is a green pigmented chemical that facilitates photo synthesis in plants and algae. why is it green and not black? I could not tell you, perhaps green provides the optimal light absorption properties needed for plant photo synthesis, where black might absorb too much light/heat to be effective...........

[KittyWampus]

25. the Goldilocks effect? Blue chlorophyll reflects too much and Red too little but Green is just right

[csziggy]

42. See my post above about the Scientific American article

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=389&topic_id=5382895&mesg_id=5385858

Essentially, under our star, green is the most efficient color for photosynthesis. Under different stars emitting different wave lengths of light, other colors might be more efficient.

[Tesha]

37. Because the various possible photochemical reactions are all tuned to particular wavelengths of...

light and plants happened to evolve a certain set of
reactions that didn't involve absorbing green.

And this set of reactions presumably managed to
out-compete any other sets of reactions that were
randomly happened-upon so far during the Earth's
long evolution.

Tesha

[Winterblues]

14. Yes that is all well and good but why green and not black or brown?

Why did photosythesis require the color to be green. Is it because it absorbs better from the sun and if it is ..why?

[cbc5g]

17. Answer here

http://en.wikibooks.org/wiki/Biology,_Answering_the_Big_Questions_of_Life/Photosynthesis#Why_are_plants_green.3F



Green isn't absorbed, the other colors are absorbed. Green is reflected which is why you see it as green.

[Richard D]

16. Green is a whole lot prettier than black.

Plants do care.

[ThomWV]

19. Green - because green is my favorite color and Jesus loves me, so its green.

How could it be otherwise?

[ColbertWatcher]

41. Ramen. n/t

[kimmerspixelated]

44. Wait a minute!

Green is MY favorite color!

[KittyWampus]

21. great question!

[soothsayer]

22. they'd fry if they were black (maybe)

[Warpy]

23. Vegetation isn't green to absorb sunlight but to use it

to convert carbon dioxide into sugars. That's what chlorophyll--the green stuff--does.

[KittyWampus]

27. you just made me think- some plants (Orchids) DO essentiall "use" the colors they reflect.

Think of orchids that evolved to not only mimic the shape of insects but the insect coloring as well.

Okay, that's the flower and not the greenery...

[global1]

31. Because God Didn't Think Black Vegetation Would Look Good.....nt

[hunter]

32. The sun is green. To you it looks white because your species evolved here on earth.

Heat up a tungsten filament and it goes from dull red hot, to red hot, to orange hot, to yellow hot, to green hot, to blue hot... The sun is that green hot color but you see it as white because this perception of white improves your ability to discern other colors. You don't see a lot of green stars in the sky for the same reason. You see stars like our sun as a similar white or yellow white color.

Nevertheless humans have rather poor color perception compared to most birds because our little nocturnal mammal ancestors lost one of their color receptors and saved some energy. When color vision became more useful again, when our primate ancestors started eating a more birdlike diet instead of sniffing around in the dark for food, a new receptor evolved when the single mamalian red-green color receptor split into seperate red and a green color receptors. But in comparison to birds these two new receptors are spaced too closely together in the spectrum for optimal color discernmant.

Plants are green for a couple of reasons... if things can be said to have a reason. First there is plenty of green light around. The way the human eye works it sees a spectrum with lower levels of red and blue than the ordinary "white" solar spectrum as "green." The molecules that give plants their colors absorb a greater proportion of red and blue light so the plant looks green. But they also absorb a lot of green light too. A similar thing happens in a common formula for olive or sage green paints. Carbon black which absorbs a broad spectrum of colors is mixed with yellow iron oxide and the resulting paint looks green.

As it happens there are a limited number of molecules easily synthesised by living things that might be useful for photosynthesis. Chlorophyl is one, but there are others. A couple of photosynthetic pathways that don't depend upon Chlorophyl have been discovered. Photosynthesis using chlorophyl became the most common sort of photosynthesis because it was good enough, even though it "wastes" a lot of green.

So that's why plants are green. Beyond that plants have to deal with heat and water loss. Some plants have very elaborate mechanisms to keep from overheating and loosing too much water. In a very real sense there is too much solar energy at times for the plant to deal with, for example a clear hot day at noon, which plays somewhat in the favor of chlorophyl too. If the green light of the noonday sun is reflected, the plant stays a little cooler.

It's all a magnificent set of delicate balances and compromises.

[OPERATIONMINDCRIME]

33. Because It Works. The Answer Just IS That Simple.

It works. All the wavelengths absorbed regardless of what is reflected is enough to efficiently give and sustain life to the plant. That's what evolution does: It makes things efficient. In this case, the color simply works well enough or perfectly enough for the plant that no further evolution is necessary. It does what it needs to do.

One could always say "well wouldn't it be better if the color was blah blah blah?", but that's always just a silly exercise. It's like saying "wouldn't we be better off if we had three arms? Two penises? Etc etc.

Green works. That's all you really need to know to answer the question. Chlorophyll etc is green because that is justtttttt right to efficiently give and sustain life of the vegetation. It does what it needs to do, and no further evolutionary change is necessary.

Someday if the environment undergoes drastic changes to the degree I can't even readily think of, maybe further evolution would be necessary and a different color would result. But for now? Black absorbs more light and heat. Vegetation is green because it serves its purpose and from the vegetations' perspectives, there is no need whatsoever for further color evolution at this time.

[Igel]

38. Because absorbing all light would be expensive,

absorbing a few wavelengths is much cheaper.

Think of it as cost and benefit superimposed on a bunch of random mutations.

You have a mutation that allows to pick up a wavelength or narrow range of wavelengths and convert that energy to a useable form, great. You have a food source.

Other plants also did the same thing. I believe that there's speculation that a lot of early life was probably purple or red. They had less "powerful" energy sources and, as a consequence, were less able to compete.

Most plants pick up a few wavelengths. But for every wavelength absorbed, a different molecule is needed, and that probably entails having different pathways.

So, why aren't plants black for maximum efficiency? 1. Perhaps not a sufficient number of molecules were randomly produced and selected for--in other words, the necessary mutations never occurred, so there was nothing to be selected for. 2. Perhaps the need isn't sufficient for plants to have evolved incorporating all the available chorophyll molecules. They got along well enough with them so there wasn't a great enough bump in survival and reproduction. 3. Perhaps there's actually a reason that makes having *too* many chlorophyll molecules a disadvantage--perhaps it's too complicated or expensive for an organism to maintain all the different genes and molecular machinery for using them. 4. Perhaps the molecules were produced by random mutation and the benefit was high enough, but chance extinctions destroyed them, or what was necessary for them to be incorporated into a variety of genomes never happened. Chance can destroy as well as create.

[hunter]

39. I think of it this way: the plant doesn't need any more energy.

It's got enough to live and reproduce where it is.

In some environments the trees dominate, shading out their competition underneath, but in other environments growing taller isn't appropriate because there simply isn't enough water for trees -- either the place is dry, or the water is frozen for much of the year. Growing taller has an insignificant or negative value.

Plants can pack more or less chloroplasts (and thus more chlorophyll) into their energy collecting surfaces. Plants simply never needed more efficient energy collectors because other factors were limiting their growth. Greater collection efficiencies were of no value, just as those extra reptilian color receptors were of no value to a little mammal hunting mostly with its nose and whiskers. But the capacity for having additional color receptors remained

In the larger pictures of life, price doesn't matter. A thing has value, or it doesn't. I don't pay any attention at all to the price of things that have no value to me. If Oprah gave me a car it would have a negative value to me. I might give it to someone else to avoid paying taxes, or even to avoid having another car. I view cars as an irritation. My 25 year old truck works fine, so please Oprah, give the car to someone else.

The ecological world works very much the same way, it's not so much what things cost, but the value of things within a given environment.

Most plants and animals have a huge library of genetic processes that are simply inactive. When the environment changes it's never so much the innovations that allow a species to evolve into something more suited to the changed environment, it's more like a simple readjustment and reinterpretation of existing plans.

The model of evolution as an economic process is wrong. The model of human social and environmental relationships as an economic process are wrong too. The environment is very rich, and in any given place there's only a few limitations to expansion, and usually these are big limitations such as the availability of water, or some specific nutrient, the presence of toxins, or the availability light. Within these environments certain biological expressions are valuable, while others are not.

Personally I tend to think models of supply and demand, or costs and benefits, or even profits or losses, are grossly unstable and do not accurately reflect the basic biology of human beings and the earth's environment. By our careless use of these unstable models we have placed our society and billions of human beings in great jeopardy.

[NutmegYankee]

45. Ah - You see the green because they REFLECT it.

They do not absorb the green light, and instead it reflects back to your eyes.

Chlorophyll does best in the red and blue areas of the spectrum. I guess the green wavelength isn't as efficient a driver of the chemical process, but there are other pigments that reflect red and yellow, which is why leaves change color when the chlorophyll dies off in Fall.