Chlorophyll under strange new stars.

[tjoneslo]

I was originally thinking of a 'water world' with one of those high numbered atmospheres having life in the toxic oceans. I was under the impression that carbon based life is also the SOURCE of most of Earth's free oxygen (plants stealing carbon from CO2).
{/quote]
This is true. Were it not for the green plants constantly breaking the CO2 down, the oxygen would quickly (in geological time) react out of the atmosphere.

A Boron-Hydrogen-Sulfur-Phosphorous dominated environment?
It sounds like a place VERY hostile and toxic to human life.

Yes, true.

One thing to keep in mind is that the long chain molecules created from boron, silicon, or some other elements are not as stable as carbon chains. This means there is far less energy in bonds. This means it's easier to make these compounds, meaning the plants and creatures can be larger than earth creatures. But is also means there's less energy available to them when they are broken down (ie. when the animal eats the plants).

This would mean that (all other things being equal), the plants will be larger than the earth equivalent kinds of plants, and the animals will be smaller, less energetic, or both.

Because of the nature of the compounds under discussion, I'm guessing that this world is orbiting a cooler, red star (e.g. M5 V) where the energy output of the star isn't enough to power the chlorophyll carbon/oxygen cycle.

And at this point, I've reached the end of my knowledge of chemistry.

 

[Thuban]

Living on the Red Edge

"Researchers have sequenced the genome of a unique bacterium that uses a rare form of chlorophyll to harvest far-red light. It is the first chlorophyll-d containing organism to be sequenced, and will provide new information about the genetic evolution of life on Earth."

 

[Ishmael]

I had a thought..

except for 'odd' ecologies like around black smokers, don't chlorophyll using organisms produce all the food in an ecology by virtue of using solar energy to make sugars from water and CO2 and a bit of other stuff? Wouldn't that mean that incident solar radiation determines the amount of food production on a world? I hardly think setting up a lighting system shining on multiple square kms of fields is practical.

That must have an effect on populations and trade.
solar radiation on the surface in w/m^2...what a thing to make a pop dm out of...

 

[Thuban]

I had a thought..

except for 'odd' ecologies like around black smokers, don't chlorophyll using organisms produce all the food in an ecology by virtue of using solar energy to make sugars from water and CO2 and a bit of other stuff? Wouldn't that mean that incident solar radiation determines the amount of food production on a world?

On Earth, to some degree,* but there’s no reason to assume that photoautotrophs will be the dominant primary producers on any given world. An ecosystem where chemoautotrophs or mixotrophs are the dominant primary producers would not require starlight at all or smaller amounts instead.

Many science fiction authors tend to divide up organisms as 'plants' and 'animals,' which loses out on some of the nuances. For Traveller I tend to fall back on the same divisions because (1) they appear often in canon and (2) it’s easier for players to grasp and therefore sets the scene more readily, so I keep the more unusual ecologies as exceptions rather than the rule. However, we shouldn’t assume that 'plants' as we understand them on Earth would evolve elsewhere. Autotrophs may take on very different forms.

* Sunlight alone doesn’t determine yield – there are many other the factors as well.

 

[Agemegos]

Well, given that chlorophyll (green) actually reflects the most energetically prolific part of the Sun's spectrum, and that plants using chlorophyll as their photosynthetic pigment nevertheless predominate over plants using purple-red, orange, blue-green, and brown pigments on Earth, it has to be clear that a match to the colour of the light is not particularly important.

Chlorophyll is relatively inefficient at absorbing sunlight, but relatively efficient at converting what it does absorb into usable chemical energy. Given the expense of making it, and the abundance of the trace elements that go into it, it is the most cost-effective photosynthetic pigment that has happened to crop up on Earth. Given that chlorophyll would be even more efficient under orange, red, or slightly bluer light than we have on Earth, it would probably do very well under any different class of star that is compatible with a habitable planet anyway.

If efficiency at absorbing light were what mattered, and if every colour of pigment were biochemically available, plants under all stars would be black.

 

[Ishmael]

I won't think the best color would be black because that'd cause the 'plant' to absorb perhaps more energy than it can process and raise its temperature higher, which may or may not be good.

I figure that plants over the millenia have adapted to the best most useful method of using sunlight and that similar 'plants' under different stars would adapt as well, so no use worrying about the color except for..ahem...color. But then, just how well would earth plants transplanted to another world fare when forced to use another wavelength?

I don't know very much about chemistry, but if the chemical equation says co2 and stuff and water+sunlight=o2 and stuff and sugars, then assuming chlorophyl that we know about, yeild should be predicted by solar radiation and water available. I have seen equations of such a sort for predicting yeilds of rice crops somewhere... Argiculture will need a certain amount of water to grow things.

just rambling

 

[Agemegos]

I figure that plants over the millenia have adapted to the best most useful method of using sunlight

Only the best and most useful out of possible ways. Just because (for example) a deep blue pigment would in theory be more efficient doesn't necessarily mean that there is any molecule that is that color blue and that works. Photosynthetic pigments depend, on a fundamental level, on the quantum mechanics of organic metal compounds. They can't evolve a new quantum mechanics and they can't evolve a new metallic element. The possibilities are now doubt numerous, but it isn't obvious that there must be a possibility for every colour.

Anyway, if you were to theorise about the worst possible colour for making use of Sunlight you'd pick a yellowish green, and chlorophyll is not far off that. I am therefore left entirely unconvinced that the photosynthetic pigment that wins out under the light of any particular star need bare any obvious relationship to the colour of the starlight. The only thing that you can be sure of is that it won't be white or silver.

 

[Ishmael]

another idea then...
of course the 'possible' ways...if its not possible, it can't be the 'best and most useful'

isn't there a relationship between light frequency and depth of penetration?
If so, then perhaps the best color is one that allows just the right penetration into the plant, past the outer cells....

of course I may have just imagined that bit......