Fact Checked

What Is Red Chlorophyll?

Megan Shoop
Megan Shoop

Red chlorophyll is a rare red pigment found in a very small percentage of marine plants. Like green chlorophyll, it allows the plants to absorb light to begin photosynthesis, the process by which plants convert energy into food. Plants containing red chlorophyll typically fall into the category of cyanobacteria, or microscopic plants that grow in small colonies on coral reefs and stationary marine animals, like sea squirts.

One particular species of cyanobacterium contains red chlorophyll, also classified as chlorophyll d or chlorophyll f. Called Acaryochloris marina, these cyanobacteria appear red in color, making them unlike the rest of their species. The ancient Greeks gave cyanobacteria their name because cyano means 'blue-green.' Acaryochloris marina does not share this color trait, but shares the same cellular structure, growth patterns, and environmental needs as the rest of its species. Cyanobacteria filled with this chlorophyll can also grow at lower depths than its blue-green cousins.

Red chlorophyll comes from microscopic plants that grown in small colonies on coral.
Red chlorophyll comes from microscopic plants that grown in small colonies on coral.

This variety of marine flora shows up red on the light spectrum because it absorbs infrared light on the extreme end of the light spectrum and reflects visible red light. Infrared light wavelengths are much longer than those in the visible spectrum, allowing them to penetrate deep into the ocean. Most other lights, especially the blues and purples on the short end of the spectrum, are filtered out of the light that travels into the water. If Acaryochloris marina could not absorb infrared light, it could not survive.

There are two kinds of red chlorophyll: chlorophyll d and chlorophyll f. The first kind absorbs infrared light just outside of the visible spectrum, generally measuring 700 wavelengths or more. The second variety absorbs infrared light in the 800 wavelength range and higher. Plants containing chlorophyll f can survive deeper in the ocean than those containing chlorophyll d, though both kinds of chlorophyll require sunlight.

Scientists interested in genetically engineering plants are trying to find a way to make ordinary farmers’ crops produce red chlorophyll. Above the water, red chlorophyll would, theoretically, absorb much more sunlight than green chlorophyll. Green chlorophyll absorbs blue and purple rays of light on the short side of the visible light spectrum, meaning that the rays it absorbs aren’t as strong as red and infrared light. Terrestrial plants able to absorb long, strong infrared rays of light might be able to photosynthesize at a very high rate, meaning they would mature and produce crops very quickly.

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Discussion Comments


The reason chl-a appears blue/green is because it has absorption peaks in the purple and red wavelengths, so by default it reflects light in the green color that we see. Please note that the article is wrong in assuming that longer wavelengths breach deeper water; it is quite the opposite. wavelengths in the red and IR are attenuated the quickest, having the lowest energies. This is why when you go diving at depth, the first color you lose is red; it appears black or brown on fish or coral. This is also fundamentally why the ocean is blue.


@Iluviaporos - Well, evolution isn't perfect. If there isn't any kind of naturally occurring black pigment that can easily show up in evolution plants can't just suddenly decide to be black.

The red in these algae is probably a pigment that's always been available in the DNA but just doesn't get expressed.

Like, it would be possible to put together a bird with scales because somewhere in DNA combinations there is the ability to create scales from what's available to them.

But you probably couldn't make a bird with organic diamond scales since the DNA isn't capable of producing something like that.

Or there could be some other reason. I mean, obviously red algae is less efficient at multiplying in most environments or it would be everywhere. Perhaps green is a better choice than we think.


I think it's really interesting that green is such a ubiquitous color in our world when it is obvious that other colors of chlorophyll can work just as well.

I've always wondered why plants aren't colored black, in fact, because that would allow them to absorb the most light. Maybe in very bright places like deserts it makes sense for them to be green or another color, but anywhere else, surely being black would be an advantage?

These algae have managed to live in the depths of the ocean because they were a different color to the norm, so they could live off the infrared rays that penetrated that deep.

It just seems odd that nothing else ever evolved to take more advantage of more of the light spectrum in the history of the earth.

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    • Red chlorophyll comes from microscopic plants that grown in small colonies on coral.
      By: lilithlita
      Red chlorophyll comes from microscopic plants that grown in small colonies on coral.