submitted 1 month ago* (last edited 1 month ago) by Potatos_are_not_friends to c/[email protected]

As Cary Mitchell, a horticulturist at Purdue University told NPR, in the 1990s, “research showed that you could grow lettuce in just red light. If you add a little bit of blue, it grows better.”

If you’re interested in why, a redditor named SuperAngryGuy wrote up a detailed, well-sourced analysis about three years ago, here

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[-] bhmnscmm 46 points 1 month ago

Any plant can grow with "artificial" light. It's just a matter of generating the correct light spectrum for a plant. There's nothing special about the light coming from the sun.

[-] Gabu 40 points 1 month ago

Well, there is one thing special about the light from the Sun... there's a shit ton of it.

[-] [email protected] 4 points 1 month ago

Also, it's free.

[-] [email protected] 8 points 1 month ago

Well sunlight is full spectrum colour plus ultraviolet and infrared. I'm sure there are benefits to the plant we can't easily measure, since they evolved with full specteum. We found a LED grow bulb with a yellow LED besides RED and BLUE, the plants grow like crazy

[-] [email protected] 1 points 1 week ago

That's going to be less efficient per watt though, plant's are green because they don't use the green light, hence red+blue grow lights.

Not all plants reflect the same range of wavelengths though, and different plants will use different wavelengths to grow. This is basically an exercise in finding which wavelengths we can drop without significantly slowing growth for each plant.

[-] [email protected] 1 points 1 week ago

This articles says plants only absorb 90% of green photons even though green has moat energy, as a way to mitigate over and under lighting in the chemical process. https://www.quantamagazine.org/why-are-plants-green-to-reduce-the-noise-in-photosynthesis-20200730/

[-] [email protected] 1 points 1 week ago

That article just throws out a number. I found a couple papers that give green light absorption numbers between 50% (for lettuce) and 90% (for broadleaf evergreens). Sadly they are paywalled.

The paper that article links talks about pairs of absorption peaks targeting steep portions of the available light spectrum, as a method of reducing power noise in changing conditions. The reason for avoiding green light here would be because the spectrum is too flat around green: there are no pits to help stabilize incoming power. Despite blue light having nearly identical intensity, green plants strongly absorb blue light, supposedly because there's a steep drop off in intensity moving into purple and ultraviolet light. I don't think this explains the decently strong red light absorption though, as the terrestrial spectrum is still rather flat there.

I'd argue this is more a holdover from competition with simpler purple Haloarchaea in ancient oceans, the Purple Earth Hypothesis . Perhaps this avoidance of the otherwise strong green light is what allowed green plants to develop complex structures and those complex structures need much smoother power input, precluding the development of green light photosynthesis. Also possible is that developing new photosynthetic pathways is just too difficult, and green plants are too specialized to try.

Some of those specializations may be the use of green light to direct non-photisynthetic processes, detailed in this paper, which is also more directly relevant to the original point. Some green light increases yields significantly, despite maybe not promoting photosynthesis as efficiently per watt as red & blue light.

[-] [email protected] 2 points 1 week ago

Yes, seems highly complex and we may not fully understand it all yet.

[-] [email protected] 23 points 1 month ago

Most plants do. That's why they're green - they reflect the photons from the mid range, and absorb the ones from the extremes (red and blue/violet) to actually work their shit. Like this:

Picture from Wikipedia.

(I wonder how efficient this would be to power exclusively with solar light. How many layers of plants could we grow, where we usually grow only one?)

[-] shalafi 7 points 1 month ago

Neat! I knew that but the pic is worth 1,000 words.

[-] SatansMaggotyCumFart 15 points 1 month ago

Weed can grow with artificial sunlight too, people have know this for years now!

[-] [email protected] 3 points 1 month ago

Yeah I'm sitting here wondering what all the fuss is about, that's how I've grown weed for decades lmao.

[-] [email protected] 11 points 1 month ago* (last edited 1 month ago)

OP, this will blow your mind!

10,000 heads of lettuce a day - indoors! Pretty damn cool.

[-] [email protected] 6 points 1 month ago

ooo I'm eating lettuce from my lil' hydroponics system right now! It uses a small pump to circulate nutrients and that gamer-powered light energy.

It's the only way I can keep plants alive... give them back to nature...

[-] x4740N 5 points 1 month ago

Pretty sure plants need a rest period as well

[-] Aecosthedark 4 points 1 month ago

I dont know about need, but a lot of weed farmers feel that plants do better with a rest/dark period. I haven't noticed a difference but give them a rest period anyway as its "natural"

[-] [email protected] 3 points 1 month ago* (last edited 1 month ago)

I tried growing a plant in a closet once. The instructions I was given were to leave the light on 24/7 until it was as big as I wanted, then to switch to a 12 on/ 12 off cycle to get it to bud.

I didn’t try very hard on it and ended up with a quarter of mid weed after like 6 months

[-] [email protected] 2 points 1 month ago
[-] [email protected] 3 points 1 month ago* (last edited 1 month ago)

7g, so not really

[-] [email protected] 2 points 1 month ago

Got the wife an aerogarden for Christmas. We’ve been growing a ton of herbs indoors with just the led lights for months. Wait til you find out you don’t even need soil to grow stuff

this post was submitted on 18 Apr 2024
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