Light is the basis for almost all life on Earth. Using energy from the sun, plants, algae and some bacteria create complex sugar molecules that serve as the foundations for most of nature's food chains. But parts of this world-feeding chemical reaction have remained somewhat of a mystery — until now.
For the first time, researchers have observed the beginnings of photosynthesis, starting with a single photon.
"A huge amount of work, theoretically and experimentally, has been done around the world trying to understand what happens after the photon is absorbed. But we realized that nobody was talking about the first step," Graham Fleming, a chemist at the University of California Berkeley and co-author of the new research, said in a statement. Fleming and his team described the process in a study published June 14 in the journal Nature.
When light hits a plant's chloroplast — the sugar factory of the organelle world — it absorbs energy from the incoming photons and uses it to turn carbon dioxide and water into glucose and oxygen, thanks to a pigment called chlorophyll.
Scientists have known about this process since at least the late 1700s, but it's taken much longer to unravel the granular details. A pair of French scientists first isolated chlorophyll in the early 1800s, and by the end of the century, botanist Theodor Wilhelm Engelmann had uncovered its role in absorbing sunlight, according to a 2019 paper published in the Annals of Botany. Researchers made more progress in determining the biochemistry of photosynthesis throughout the 20th century, discovering, for example, that excited electrons help to transfer energy through the chloroplasts.
They also realized that chloroplasts must be very sensitive to light — after all, plants can photosynthesize in shady conditions, and the photons in a ray of sunshine are relatively diffuse. Scientists hypothesized that only a small number of photons are needed to kick off the process. However, nobody had successfully observed that crucial first step.
In the new study, the researchers looked at purple photosynthetic bacteria, which share an ancient ancestor with modern-day plants and algae. They set up a photon source that spits out just two photons at a time. During each test, the first photon fired out was absorbed by an ultra-sensitive detector, while the other struck the bacteria's equivalent of a chloroplast. Sure enough, when the second photon hit its target, photosynthesis started up.
The researchers performed this test over 1.5 million times to ensure that the second photon, rather than some outside force, was triggering the chemical reaction. This confirmed that just one photon was enough to set off photosynthesis.
"This experiment has shown that you can actually do things with individual photons. So that's a very, very important point," Birgitta Whaley, a chemical physicist at UC Berkeley and co-author of the study, said in a statement.
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Joanna Thompson is a science journalist and runner based in New York. She holds a B.S. in Zoology and a B.A. in Creative Writing from North Carolina State University, as well as a Master's in Science Journalism from NYU's Science, Health and Environmental Reporting Program. Find more of her work in Scientific American, The Daily Beast, Atlas Obscura or Audubon Magazine.
So... if photosynthesis in green plants produces sugars, water vapour, oxygen, etc., from carbon dioxide in the presence of photons (light) and is so important for life on Earth , why on earth are countries like Canada, USA, European Union trying to ban carbon dioxide from our atmosphere which is only .04 of 1% of our atmospheric gases? HUH?????Reply
Because the present level of CO₂ in the atmosphere is already 50% higher than it was just 150 years ago, and was for the millennia during which our present ecosphere, including humans, evolved. And it's rising very quickly. This change is starting to create a new, much warmer environment for the planet.Geobiologist said:So... if photosynthesis in green plants produces sugars, water vapour, oxygen, etc., from carbon dioxide in the presence of photons (light) and is so important for life on Earth , why on earth are countries like Canada, USA, European Union trying to ban carbon dioxide from our atmosphere which is only .04 of 1% of our atmospheric gases? HUH?????
Sustaining this trend will be very bad news for all the species currently living here, including us, which evolved under conditions very different from what we are heading for. What we are trying to do is to reverse this trend, to get the CO₂ levels back down to something closer to what we evolved with, to continue to have the kind of world that we, including you, would want to live in. No one is "trying to ban carbon dioxide from our atmosphere."
But you knew that. Whether you choose to acknowledge it or not.
I think you are missing a point in that the mean global temps have dropped since 2008.... And Plants needs about 1500 ppm to grow properly... We are n a CO2 deficit. I researched and taught paleoclimates and I suggest you take a similar course and educate yourself... We've a long way to go, baby!Reply
I don't see the relevance to the rasearch here.Geobiologist said:So... if photosynthesis in green plants produces sugars, water vapour, oxygen, etc., from carbon dioxide in the presence of photons (light) and is so important for life on Earth , why on earth are countries like Canada, USA, European Union trying to ban carbon dioxide from our atmosphere which is only .04 of 1% of our atmospheric gases? HUH?????
But if you are discussing man made global warming, it is the man made greenhouse gas that is banned, not the natural background level. The amount of carbon dioxide has doubled since pre-industrial levels..
The ban is because the rapid increase in global warming has started to cost more than fixing it.
Nitpick: The European Union is not a country.