Wednesday, April 11, 2007

Blue leaves...

Who hasn't wondered if there is life elsewhere in the universe? What would it look like? How would it function? Through biology, especially evolutionary biology, we can make educated guesses as to the form and function of the flora and fauna of other worlds. Kiang et al. go a step further, into a realm seldom imagined. They calculated the photosynthetically relevant radiation on earth-like planets orbiting other stars. The results are surprising. Different stars have different optimal photo spectra. Therefore, plant colors on other worlds might be different from plants on earth to capitalize on these differences. This would no doubt have cascading effects to all other species on those planets. Imagine blue lizards adapted to hide among blue leaves, and the birds adapted to find them.

Photo by Vincent Lillis.


  1. Western fence lizards, one of the more common lizards in the western US, have a whole lot of blue, but its on the underside of the lizard, so you won't see it unless you catch the lizard.

    See for a typical example.

    The other good example of a blue lizard is Skilton's Skink, which has a bright blue tail:

  2. Yesterday or today I saw a press release on line for an artical about the appear in Nature, if I remember correctly, arguing that early photosynthetic life on Earth was not green but purple. The gist was that the active compounds then absorbed light from the green part of the spectrum and reflected the red and blue parts. (I don't recall the specifics, but I'm sure the article and press release can be located.) If true than your hypothesis about "plant life" taking on other colors occured here on Earth, but too early for us to have witnessed it in real time.

  3. Colors... fascinating stuff.

    I first saw the Skilton's Skink along the banks of the Selway River in Idaho. For years, I searched the herp books for blue snakes of Idaho (there are none). Only some time later did someone point out the skink, and how I had likely mis-identified it. Interesting how all I noticed was the tail, and presumably that is what a predator would primarily notice as well.

    I'll keep my eyes open for the Nature article.

  4. As long as a black-body has enough heat to make one color , it should make the other. I think that atmospheric gas absorbency would have more effect on two colors as close as blue and green. Interesting concept!

  5. Michael,

    The problem is not with what reaches the plant, but what color is best for processing light. On our world it is green that is reflected back to us from plants. That's because conditions at or near the water's surface meant that green chlorophyll was more effective than any other chlorophyll color. That is why seaweed is green, since seaweed is descended from the same life form that gave rise to plants.

    Kelp on the other hand is brown, because it is descended from an ancestor that arose at a layer in the water column where brown chlorophyll worked better. And being 'saddled' with brown chlorophyll when forms able to grow up towards the water's surface appeared, it couldn't 'adopt' green chlorophyll as a better alternative. Sort of like being stuck with a choice your ancestor made.

    Now how blue plants could come about is a puzzlement to me. I combination of unusual circumstances might do it, but what usual circumstances is quite beyond me. Maybe somebody better versed than I in the chemistry of chlorophyll could fill us in.

  6. Thinking back to Keanus' comment, what about all those partly purple Amazonian houseplants we all have collecting dust in our apartments? Certain coleus are nearly entirely purple. Are most plants like deciduous trees, where there are different color chloroplasts reflecting back not only green, but also red or yellow? And is the purple really from reflecting back the blue? I think we don't see a lot of blue plants around because the blue/purple light is the high energy, shorter wavelength light and an optimally adapted plant might have to balance the more efficient electron excitement with the radiation damage. But I'm just blathering. Let's hear what you think.

  7. Welcome to the blogosphere. I have a few questions.

    What happens when Creationism meets evolution?

    How do you explain what
    you don't understand?

    Are we turning into The United States of Creationism?

    Feel free to use the 'toons, with credit to Hypnocrites.

    I know I'm whoring, but I'm just horrified by the anti-science trend in the country, and the only way I have to fight against it is with pen and ink. If my illustrations can help your arguments, they're yours for the taking.

  8. All chlorophyll is green, it's just that different photosynthetic organisms have different additional pigments for using part of the light that the chlorophyll misses.

  9. nit:

    most of your blog links are simply that. Your Sandwalk link goes to a particular post.

  10. Would their hardcore leftist environmentalists be the Blue Party?

  11. I'd expect plants to be black. The first generation of solar cells work by converting one band of light to electricity. Some newer cells have two layers. The short wavelengths are absorbed by the top layer, and the longer wavelengths is absorbed by a lower layer. Total efficiency is higher. If plants did that, they'd have more energy for metabolism. Eventually, they'd do a good job of absorbing all the likely wavelengths.

    I could be wrong, of course. Evolution takes everything into account. It might be harder to keep two or more layers working right, and give advantage to single layer creatures. Why don't animals do more photosynthesis? It could give them a 10% energy advantage.