Why do plants need green light specifically? Could plants theoretically photosynthesize different wavelengths? Thank you for reading and have a good day.
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Photosynthesis uses red and blue light for energy conversion because chlorophyll, the pigment responsible for photosynthesis, absorbs light most efficiently in these wavelengths. While green light is not as efficiently absorbed, it is still utilized to some extent in photosynthesis, but the energy is less efficiently captured, which is why plants appear green as they reflect green light.
It’s backwards. Plants appear green because they *reflect* green light, meaning, they don’t use it as much as they use other colored light (red, blue mainly). Why don’t they use all of the green light? That’s open for debate. It could be that evolution just happened to deliver a molecule – chlorophyll – that was damn good at the job of absorbing light, but still only got 90% of the green light.
To add to the others, the reason chlorophyl reflects green light while absorbing red and blue is because of a fluke of evolution. Eons ago, the main photosynthesizers in the oceans used rhodopsin which uses green light and reflects red and blue because that’s the group of wavelengths that the sun shines strongest in. When a new kind of photosynthesis evolved, it had to be competitive with the purple rhodopsin users. So it was tuned to using red and green light that rhodopsin didn’t use. As it happens, this new kind of photosynthesis generated a powerful toxin as a byproduct. The new cyanobacteria had a slightly better ability to withstand exposure to this toxin than the old bacteria that used rhodopsin since they were already surrounded by it, so they gradually replaced the old guard. By then, though, chlorophyl was already optimized to using red and blue wavelengths and couldn’t be changed to also incorporate green.
The deadly toxin, by the way, was oxygen. So harmful was it back then that one of the names for the event is the Oxygen Catastrophe. It’s still highly toxic to life, but most living things nowadays have developed enough defences against it that they can not only thrive in high concentrations, but even metabolize it for energy.
It isn’t. Plants reflect green light and that’s why leaves are green. Indoor greenhouses actually use special LED lights that don’t emit green light to be more energy efficient which make the leaves look black.
Here is an Eons video that explains it well https://youtu.be/IIA-k_bBcL0?si=kCfm_Nga7QVLsLy8
Photosynthesis works on the absorption of RED light (lower energy). Chlorophyll a and b absorb at around 690-700nm and this energy promotes electrons that travel through a transfer chain powering the reactions that generate adenosine triphosphate (ATP) which then powers the conversion of CO2 to sugar.
Accessory pigments absorb high energy blue light to protect the plant from being damaged by the high energy light. This leaves green light being reflected by the plant, so it appears green.
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