A newly discovered form of photosynthesis could have implications for exoplanet/exomoon habitability:
The vast majority of life on Earth uses visible red light in the process of photosynthesis, but the new type uses near-infrared light instead. It was detected in a wide range of cyanobacteria (blue-green algae) when they grow in near-infrared light, found in shaded conditions like bacterial mats in Yellowstone and in beach rock in Australia. As scientists have now discovered, it also occurs in a cupboard fitted with infrared LEDs in Imperial College London.
The standard, near-universal type of photosynthesis uses the green pigment, chlorophyll-a, both to collect light and use its energy to make useful biochemicals and oxygen. The way chlorophyll-a absorbs light means only the energy from red light can be used for photosynthesis.
Since chlorophyll-a is present in all plants, algae and cyanobacteria that we know of, it was considered that the energy of red light set the 'red limit' for photosynthesis; that is, the minimum amount of energy needed to do the demanding chemistry that produces oxygen. The red limit is used in astrobiology to judge whether complex life could have evolved on planets in other solar systems.
However, when some cyanobacteria are grown under near-infrared light, the standard chlorophyll-a-containing systems shut down and different systems containing a different kind of chlorophyll, chlorophyll-f, takes over.
Also at ScienceAlert.
Photochemistry beyond the red limit in chlorophyll f–containing photosystems (DOI: 10.1126/science.aar8313) (DX)
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Also at University of California, Riverside.
Exploring Kepler Giant Planets in the Habitable Zone (arXiv:1805.03370)
(Score: 2, Interesting) by MichaelDavidCrawford on Monday June 18 2018, @03:01PM (1 child)
I'm a life-long nite owl. Late one night when I lived in Santa Cruz I drove a few miles up the north coast so I could hang out on a certain beach.
I was at first completely convinced I was hallucinating:
When I got to the wet sand near the water, I was dumbfounded to see the sand flash all around my feet whenever I put either of my feet down.
If I stamped real hard on the wet sand, the flash was brighter and larger in area. It was not long at all that I was running back and forth along the waters edge as I wondered whether one of my Hippy friends had dosed me.
When I waded into the water I discovered that the foam of crashing wave also got lit up. I at the time had not heard of blue-green algae but figured some form of life got lit up whenever there was abundant oxygen.
I just happened to have a glass jar in my car so I scooped some of that sand into it then drove home. But by the time I woke up the following afternoon all those poor little monocellular beacons had died! I was so sad.
I'm 54, I've lived near many beaches. Bonita was heavily into the oceans so she and I went to the beach quite often.
Yet in all my days I never again saw what I did that amazing night at Bonny Doon beach!
Yes I Have No Bananas. [gofundme.com]
(Score: 1, Interesting) by Anonymous Coward on Monday June 18 2018, @03:09PM
You would love to see this then https://things-to-do-in-jamaica.com/glistening-waters-in-jamaica/ [things-to-do-in-jamaica.com]
(Score: 2) by GreatAuntAnesthesia on Monday June 18 2018, @03:19PM
Sounds like this bacteria would be a great candidate for colonising planets in orbit around Red Dwarf stars. I propose we fire a few samples of it off towards Proxima Centauri immediately.
(Score: 2) by JoeMerchant on Monday June 18 2018, @03:49PM (4 children)
There will be more than two ways to make oxygen from CO2 and starlight, I guarantee it.
🌻🌻 [google.com]
(Score: 2) by JoeMerchant on Monday June 18 2018, @03:53PM (1 child)
Damn, it's been too many years: Coach Morris Buttermaker, Bad News Bears (1976), and for some reason it's on the obscure side:
https://encuruj.com/tag/matthau/ [encuruj.com]
🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Monday June 18 2018, @10:50PM
Clbuttic film.
(Score: 3, Insightful) by PiMuNu on Monday June 18 2018, @04:55PM (1 child)
Energy doesn't have to come from photosynthesis even - vent lifeforms for example.
(Score: 3, Interesting) by JoeMerchant on Monday June 18 2018, @07:07PM
Absolutely: straight up heat differentials can be a source too. I think most of the vent lifeforms base on bacteria that extract energy from sulfides.
Photosynthesis is cool because of how it puts oxygen into the atmosphere.
🌻🌻 [google.com]
(Score: 1) by doke on Monday June 18 2018, @04:36PM (2 children)
Chlorophyll-a and -b have two absorption peaks, one in the blue-purple-ultraviolet area, and a second smaller one in the red area. Most plant light discussions suggest that blue-ish light is better for growth, and red is better for encouraging flowering. The lights I use for my rosemary, oregano, basil, etc. plants are blue-ish, specifically 6500K white T5 fluorescents. The mercury vapor emission spikes are reasonably well aligned with the blue-ish absorption region.
https://www.mpsd.mpg.de/154930/2015-04-chlorophyll-rubio [mpsd.mpg.de]
http://zeiss.magnet.fsu.edu/articles/lightsources/mercuryarc.html [fsu.edu]
(Score: 4, Interesting) by moondrake on Monday June 18 2018, @06:35PM (1 child)
The world really needs to stop looking at absorption peaks to say something about plant growth. It is like saying the photopsin in the human eye is green, therefore, humans need only green light.
Isolated Chl-a and b has peaks in the red and blue, yes. But if you would look at whole leaves you'd find most species absorb over 70% of the green. If we could see far red, that would be the color that leaves have.....
Once absorbed, not all light is equal (and things are complex), but the energy of all photons with wavelengths below far red is sufficient to move electrons. That means you get more bang per photon for redder light (as the extra energy per photon in blue is wasted), but there is also the issue about what colors are cheap to create (green LEDs for example are pretty inefficient in terms of $/photon). For LEDs, red is probably going to be most efficient in terms of photosynthesis.
But importantly, plants are far more than photosynthesis. They have receptors for various colors of light that plants probably used to "sense" their environment. A blue light receptor is for example used for stomatal opening (it has been suggested that blue is more suitable to detect absolute light levels under a canopy). Thus without blue, plants act strange like close stomata (less gas-exchange), grow weird shaped petioles and leaves, etc.
For many plants ~80% red + rest blue (in terms of photons/m2/s) is a reasonable choice. But there are many additional consideration depending on circumsance. The red:far red ratio influence things like germination and internode length, depending on your goal, you may want to adjust (if the plants fail to elongate stems and petiole they become so stunted they self-shade, growth eventually decreases. Important unless you harvest early and you do not need stem). Some plants (lettuce IIRC) benefit significantly from additional green (reason is unknown, but green does penetrate better deeper in leaves precisely because chl likes to absorb red and blue). UV can be useful to encourage them to produce pigments that improve tolerance to light or pathogens. And changing the spectrum over the growth period allows you to induce developmental stages like flowering.
Taken everything together it seems that most plants perform optimal (especially if we look at whole-life cycles under natural conditions) under a spectrum resembling that of the sun. What a shocking conclusion!
That of course does not mean you couldn't grow your garden plants under the fluorescent tubes you happen to have laying around. People wanting to optimize however could get much more growth performance by red+blue+(additional colors tailored to species&application).
(Score: 2) by moondrake on Monday June 18 2018, @06:38PM
correction: by photopsin is green, i actually meant it absorbs mostly greenish light (so it is not green at all :)