tag:blogger.com,1999:blog-6976071487922527618.post872225193737014312..comments2024-03-27T05:38:30.610+01:00Comments on Blank On The Map: Why are plants green?Sesh Nadathurhttp://www.blogger.com/profile/07155102110438904961noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-6976071487922527618.post-22149909200967693472012-09-14T09:57:44.746+02:002012-09-14T09:57:44.746+02:00Interesting point, thanks!Interesting point, thanks!Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-5108966860679400432012-09-14T08:44:21.079+02:002012-09-14T08:44:21.079+02:00Hi Sesh,
Not only can excess light be damaging, b...Hi Sesh,<br /><br />Not only can excess light be damaging, but the energy from light may not be the primary limiting factor in photosynthesis. Have a look at https://en.wikipedia.org/wiki/Photosynthesis#Light_intensity_.28irradiance.29.2C_wavelength_and_temperature<br /><br />I think the limiting factors in photosynthesis are generally carbon & water, particularly since there's a tradeoff in the availability of the two: in order to take up more carbon, plants have to open their stomata which means they lose water more quickly.<br /><br />Having said that, I'm not sure if there's a consensus about a simple, straightforward answer to your question. These are just my musings on a pleasant Friday morning...Sedeer El-Showkhttps://www.blogger.com/profile/03206788455219126375noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-44165311946924305732012-09-09T20:23:38.055+02:002012-09-09T20:23:38.055+02:00Hmm, yes, I hadn't considered that this was al...Hmm, yes, I hadn't considered that this was all probably happening in the sea. But were the retinal organisms supposed to be translucent then? I suppose I should just wait until I can access the actual journal articles themselves.Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-68315993123988666822012-09-09T18:57:56.459+02:002012-09-09T18:57:56.459+02:00I assumed they meant something more like a change ...I assumed they meant something more like a change in spectrum caused by the retinal organisms so the peak energy density was at a different wavelength.<br /><br />I believe this was also happening in the sea and chlorophyll based organisms were deeper than retinal, as retinal already occupied the region close to the surface. Again changing the spectrum.<br /><br />I also imagined it was a simplification and probably just one of many factors ;)<br /><br />Thanks for the welcome, now I'm going to have to read your other posts :)Garethhttps://www.blogger.com/profile/02145167289495324374noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-50676344009937226352012-09-09T15:44:17.128+02:002012-09-09T15:44:17.128+02:00Another thing that a friend pointed out in a diffe...Another thing that a friend pointed out in a different forum is that of course the spectrum of light which arrives at sea level on the Earth is different to that actually emitted by the Sun. It is <a href="http://en.wikipedia.org/wiki/File:Solar_Spectrum.png" rel="nofollow">less strongly peaked at green wavelengths</a> and there is a bit of a drop-off at the very highest (blue) frequencies.Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-18895559441532777502012-09-09T12:11:59.012+02:002012-09-09T12:11:59.012+02:00Hi Gareth, and welcome to this blog! Thanks for th...Hi Gareth, and welcome to this blog! Thanks for the pointers. I don't have access to the journals at the moment either, but the Wikipedia entry on chlorophyll does have a link to an <a href="http://www.livescience.com/1398-early-earth-purple-study-suggests.html" rel="nofollow">article on LiveScience</a> with quotes from some of the scientists.<br /><br />I have to say I'm very sceptical of some aspects of this Purple Earth competition hypothesis. Specifically, they seem to be arguing that the purple organisms based on retinal were already "using up" all the green light, so chlorophyll based organisms evolved to make use of what was left. But this seems to treat the green component of sunlight as a resource similar to say the nitrogen content of soil - there's still sunlight around after the retinal-based organisms have used it, but with all the green removed. I can't see how that is true. Surely any organism with access to sunlight has access to the green wavelengths.<br /><br />On the other hand, the argument that perhaps absorbing green light as well leads to problems with heat dissipation sounds at least plausible.Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-6976071487922527618.post-52305001498597674212012-09-09T10:55:13.886+02:002012-09-09T10:55:13.886+02:00On a recent (well it was on more than 3 months ago...On a recent (well it was on more than 3 months ago!) TV program about plants (I've forgotten the name but it was a BBC program) they claimed that the first photosynthesising organisms arrived later on the scene and there were already organisms using the green spectrum (they were purple coloured). Then used what was available: red and blue, and did so efficiently. I've found a reference to this theory in Wikipedia: https://en.wikipedia.org/wiki/Chlorophyll.<br /><br />With some creative interpretation they then killed off all their competitors using deadly oxygen and took over the planet: https://en.wikipedia.org/wiki/Great_Oxygenation_Event. I think the BBC program did use this creative interpretation.<br /><br />The first two references on this Wikipedia page: https://en.wikipedia.org/wiki/Purple_Earth_hypothesis look like they head to published work but I don't have access to the journals.<br /><br />I should finally add that I have no knowledge in this field, I came across your post from a tweet by Shaun from The Trenches of Discovery and then I got curious and tried to figure out what the BBC were basing their claims on. Sadly I don't have access to any (or I'm too lazy to find more recent open access articles) journals and gooling just turns up Wikipedia results which reference subscription based papers.Garethhttps://www.blogger.com/profile/02145167289495324374noreply@blogger.com