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Author Topic: Why don't plants have black leaves?  (Read 3429 times)

Offline clueless

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Why don't plants have black leaves?
« on: 16/02/2014 20:05:29 »
Hi. Chlorophyll gives plants their green color. There are other pigments in the leaves too, such as xanthophylls (yellows) and carotenoids (yellows, oranges and reds). These pigments are also used in photosynthesis but occur in lesser quantities than the green chlorophyll. The combinations of the different pigments make different shades of green.

But, in a fantasy world of mine, I need two types of the trees whose leaves have black and grey color. Donít ask why. Is that stupid, or it is plausible for trees on another planet to have grey and black leaves, perhaps because of magic in the leaves? Should I feel embarrassed now? :-[ Or it is OK because black color absorbs light and heat?
« Last Edit: 26/02/2014 21:54:37 by chris »


 

Offline Bored chemist

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Re: Black leaves??
« Reply #1 on: 16/02/2014 21:07:12 »
I don't see a problem.
We have dark brown leaves
http://en.wikipedia.org/wiki/File:Laminaria_hyperborea.jpg
OK, they grow underwater, but that's not a problem for a fantasy world.
 

Offline CliffordK

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Re: Black leaves??
« Reply #2 on: 16/02/2014 22:13:12 »
The more light a plant absorbs, technically the better it would grow.  So black might be an excellent color for leaves. 

Pure grey?  I don't know.  If you look at your plants on Earth, there certainly are a variety of shades of green, from some that are very dark to some that are almost yellow.  Many trees have dark older foliage, and light young foliage. 

Another thing to keep in mind.  Not all light is what we call "visible light". 

Our visible light spectrum is in part because of what our sun puts out, and in part because of what is filtered by the upper atmosphere.  UV can be damaging to at least terrestrial cells.  However, if one's planet was located near a red dwarf, perhaps one's spectrum would extend far into the IR.  One could potentially have a plant that was mostly transparent to "visible light", but absorb IR.  Or, perhaps pure white, reflecting most visible light while absorbing energy from other parts of the spectrum.
 

Offline Aemilius

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Re: Black leaves??
« Reply #3 on: 16/02/2014 23:41:16 »
I don't see a problem.
We have dark brown leaves

Right, and I forget what the name of it was, but there's a tree that has extremely dark red (really almost black) leaves too.

Since it's all fantasy, I can even envisage an unbearably hot and harsh environment on the surface of a planet filled with something like kerosene. Any plant life living on the planet would have to develop an effective strategy for survival.

If there was a constant wind that always blew in the same direction over hundreds of thousands of years, evolution might take a hand as any plant life there looked for ways to escape the deadly heat at the surface.... maybe the black leaves would even develop aerodynamic properties.

One good strategy might be if the roots sucked up the kerosene from inside the planet and stored it in huge permanently airborne aerodynamically shaped black leaves kept aloft by constant never ending winds. Just imagine, an ancient and enormous form of alien plant life....

....that acts just like planes full of jet fuel!


Another effective strategy for plant life in such a harsh unforgiving environment might be using sheer mass as insulation from the lethal surface temperatures. I can imagine giant thousand foot tall squarish looking black cactus-like lifeforms....

....living skyscrapers towering above the landscape!

« Last Edit: 05/03/2014 04:28:32 by Aemilius »
 

Offline CliffordK

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Re: Black leaves??
« Reply #4 on: 17/02/2014 01:02:05 »
One thing about plants back here on Earth is that they actively do transpiration.  I.E.  Using evaporation and capillary actions to transport water and minerals from the soil up to the leaves,and then allowing the water to evaporate much like we sweat.  Ideally in a rain forest the water goes up to the upper atmosphere, cools, and falls back as cool rain.  In many senses, the plants can actively control their own environment.
 

Offline RD

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Re: Black leaves??
« Reply #5 on: 17/02/2014 02:18:13 »
... in a fantasy world of mine, I need two types of the trees whose leaves have black and grey color ...

Sounds like Daisyworld ... https://en.wikipedia.org/wiki/Gaia_hypothesis#Daisyworld_simulations
 

Offline clueless

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Re: Black leaves??
« Reply #6 on: 17/02/2014 03:53:02 »
Orgonath Big is the tallest timber tree, entirely black, including leaves that absorb more light energy than any other tree. Not bad. But what about Orgonath Small with black trunk and grey leaves? Well, Orgonath Small is a short tree, because its greyish leaves cannot absorb enough light for the tree to grow taller. Someone ran an experiment with strips absorbing light. Obviously the black strip absorbed the most. But the red, blue, and green ones did not absorb much. Interestingly, the dark grey and purple ones absorbed more than one would imagine. Do you think that I should change the darn grey color of the leaves so I don't offend botanists or it is passable?
 

Offline evan_au

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Re: Black leaves??
« Reply #7 on: 17/02/2014 11:09:47 »
Grey leaves are just like black ones, except they let through a fraction of the light for the lower leaves to collect.
After 10 (or 100) grey leaves, it will be as dark as a canopy of black leaves.
 

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Re: Black leaves??
« Reply #7 on: 17/02/2014 11:09:47 »

 

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