Alien plants

[qzzq]

Interesting article from NewScientist.com: <ul type="square"><b>For plants on alien worlds, it isn't easy being green</b><br /><br />The greenery on other planets may not be green. Astrobiologists say plants on Earth-sized planets orbiting stars somewhat brighter than the Sun may look yellow or orange, while those on planets orbiting stars much fainter than the Sun might look black. <br /><br />Vegetation colour matters to astrobiologists because they want to know what to look for as a sign of life on planets outside the solar system. Terrestrial photosynthesis depends mostly on red light, the most abundant wavelength reaching the Earth's surface, and blue light, the most energetic. Plants also absorb green light, but not as strongly, so leaves look green to the eye.<br /><br />Extraterrestrial plants will look different because they have evolved their own pigments based on the colours of light reaching their surfaces, says Nancy Kiang of the NASA Goddard Institute for Space Sciences in New York, US.<br /><br />To determine the best colours for photosynthesis on other planets, Kiang worked with NASA's Virtual Planetary Laboratory at Caltech to determine the light reaching the surfaces of Earth-sized worlds orbiting their host stars at distances where liquid water – and therefore life – could exist. The results depended on the star's brightness and the planet's atmosphere.<br /><br />... (More at the link)</ul> <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[voyagerwsh]

The original research paper:<br /><br /><i>Spectral Signatures of Photosynthesis. I. Review of Earth Organisms</i><br /><br />By N. Kiang <i>et al.</i><br /><br />http://www.liebertonline.com/toc/ast/7/1<br />------------------------------------------------------------------------<br /><br /><i>Journal of Astrobiology</i> offers readers free for the month of March, so take the advantages of them.<br /><br /><br />

 

[qzzq]

Thanks voyagerwsh.<br /> <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[fingle]

I think what you say about the light level makes sense, when you view a plant by moonlight it is very hard to tell what colour it is. Also we have plants that photosynthesize and even though they have enough chlorophyl to care on, they are not green, like the scarlet maple.<br /><br /><br />fingle<br /><br /><img src="/images/icons/smile.gif" /><br /> <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

That's for a different reason.<br />The human retina contains rods and cones.<br />Rods work at low light levels, but in black and white,<br />Cones do color, but need more photons. So at low light levels, we see in black and white. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[arkady]

Reminds me of Daisyworld <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> "<font color="#0000ff"><em>The choice is the Universe, or nothing</em> ... </font>" - H.G Wells </div>

 

[3488]

Hi MeteorWayne.<br /><br />If memory serves me correctly, that is why dogs only have black & white vision, as Dogs do not have cones, just rods. <br /><br />Although your pet dog cannot see the colours of their toys (that is for the owners amusement), they have far superior night vision.<br /><br />Not sure about cats, horses, etc!!<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[MeteorWayne]

IIRC, cats have superb night vision. In addition to the rods, they have a highly reflective surface in back of the retina which reflects the light back through the receptors again. It makes their eyes appear to "glow"<br /><br />I'll ask Amber later what she thinks about it...she's busy looking at birds and squirrels at the moment <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[3488]

Thanks MeteorWayne.<br /><br />I see, they use the light twice, how efficient. Your are right, their eyes do shine incredibly brightly at night when shone upon. So yes, perhaps they too see the world in monochromatic eyes!!!<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[alokmohan]

Good post on astrobiology,rare .None posts on astrobiology .Pioneer post.

 

[silylene old]

<font color="yellow">If memory serves me correctly, that is why dogs only have black & white vision, as Dogs do not have cones, just rods. <br /><br />Although your pet dog cannot see the colours of their toys (that is for the owners amusement), they have far superior night vision. <br /></font><br /><br />That is <b>incorrect</b>. Another urban myth repeated enough until it is believed.<br /><br />Dogs are red-green color blind, same as 4% of humans. Dogs still see yellow and blue. Dog eyes have two of the three major cone types that primates have. (yes I know there is a fourth minor cone type for deep violet associated with sleep cycles)ref. <br /><br />We had a real nice detailed thread on color vision and visual acuity and which animals have it and which don't, I think just after the meltdown...if you can find it. I will summarize quickly: Most land mammals have one or two cone types and do see some colors. Primates and lizards have three cone types and see in the same full color range that we do. Some birds have 4 cone types, as some insects have four or even more color detector cell types and see a broader range of colors than humans. Primates have a single fovea, which is an area on the retina capable of seeing in high detail. Dogs and most other mammals lack a fovea, and their visual acuity is about 1/6 as good as a human with perfect eyesight. Raptor birds have two foveas, and their non-fovea retina has the same cone density as a human fovea (which means there vision is acute at all peripheral angles, and extremely acute in two locations). Some insects and some birds can additionally detect light polarization, which is yet another visual signal. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[3488]

Hi silylene.<br /><br />AFAIK, dogs as you say have sensitivity to the spectrum you posted above, but still 'saw' it in black & white. Chances are I am wrong, as usual!!!<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[docm]

You are wrong.<br /><br />Dogs have dichromatic color vision, not monochromatic vision (B&W). <br /><br />In dichromatic color vision one of the three types of color receptor (cone) pigments is absent, usually the one responsible for red/yellow as in dogs. <br /><br />Humans have trichromatic color vision, meaning we normally have all 3 types of cones and see the entire visible spectrum. Those that don't, usually males, have a visual defect that depends on which receptor is missing.<br /><br />Sea mammals, including cetaceans, are monochromats. There are also two types of monochromatic vision; rod and cone;<br /><br />Rod monochromacy has only rod receptors (B&W) and is considered 'true' color blindness. They also tend to have problems with daylight lighting levels.<br /><br />Cone monochromacy has rods and just one type of cone, resulting in a tinted monochromatic vision. <div class="Discussion_UserSignature"> </div>

 

[kosmonavtkaa]

Some women could be tetrachromats (have four cones):<br /><br /><font color="orange">It has been suggested that women who are carriers for variant cone pigments may be born as full tetrachromats, having four different simultaneously functioning kinds of cones to pick up different colors. One study suggested that 2-3% of the world's women may have the kind of fourth cone that lies between the standard red and green cones, giving, theoretically, a significant increase in colour differentiation. Although further studies will need to be conducted to verify tetrachromacy in humans, at least one tetrachromat has been identified - "Mrs. M," an English social worker, was discovered in a study conducted in 1993.</font>/safety_wrapper> <div class="Discussion_UserSignature"> </div>