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Growing plants with lasers

AgentMcBaine

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Now, I don't have the interest to grow plants in a very scientific way, compiling data for 4 years on pepper plants, but it would be interesting to see the effects of lasers on plant growth. There haven't been many studies on it published online.
Yamazaki
UCSB
Those are literally everything I could find on the subject.

Here's my serrano peppers (at least I think they are, I put a lot of different seeds in there because it's too cold to sprout anything). The one under the blue 420nm LED light was being irradiated for more than 24 hours before I found the second sprout, and started feeding it 650nm laser light. Not stating anything here as science because there's only 2 plants and everything I ever grew my whole life up until now died before growing up; I'm a terrible father
attachment.php


Here you can see that the first plant is pretty much starting to rot, but that started happening 2 days prior. You see I pulled up the seed because it's pretty much dead now and I was curious. This photo was taken 1 day after the first, with one reasonably long night cycle in between.
attachment.php


There's a great thesis in here somewhere. You could grow 5 plants per pot and shine on them with equal power under one laser, and grow 5 other plants in another pot and shine another wavelength on them, and then get groups with regular LEDs, then groups with incandescent lamps, and whatever. The experiment would take years. Maybe you could get plants to grow faster by saturating them with more light and increasing the frequency of light cycles. Maybe you can influence the plants to produce more chlorophyll a or b.

There's no way I would commit to it, but I will be growing some plants under lasers in a leisurely manner. I'll probably continue with this little 10mw 650nm, then grow more with a 405, 445, 635, and 680. This pepper looks like it's reacting nicely to my laser. Who needs sunlight anyway. I suspect I'd get less fruits if I continued with this one wavelength.
I guess I'll update the OP / add posts if I note anything interesting, in a completely non objective manner of course.


Log1_1; 20 Feb 2016
I switched my plant to a 405nm 80mw for a day. During the second day I noticed the plant was curling up. The leaves have an apparent sunburn, white to beige discoloration where the light was hitting the leaves. Immediately switched back to 10mw 650nm laser. It still seems alive 2 days after switching back. I advise much less than 2200J/cm^2 of violet light daily [25mW/cm^2] for plants containing a high amount of chlorophyll a compared to (b), but this is just speculation based on attachment #3 in post #1. I have yet to expose a healthy plant to blue laser light >410nm.
Log1_2; 21 Feb 2016
Filled another jar for sprouting.
The pepper formerly named Pepe (the sunburned serrano) is now under a 100mw 650nm laser to compensate for reflection.
100mw red laser burned out. It was out of a pen on ebay. What am I doing with my life. Will have to switch to LEDs for the time being. This will give Pepe time to heal if his sunburn isn't terminal.
Log1_3; 22 Feb
Found another working 200mw 301 660nm lying around. Implemented at 115mw/cm^2. Contemplating dimmable laser build. Probably cost $25. Pepe looks like he's stabilizing; I'm hopeful.
Log1_4; 25 Feb
301 burned out. I think the driver spiked when I just unplugged from 5v instead of turning off the power from the strip. Pruned Pepe. He's now under the 420nm LED until he grows a second leaf.
Log1_5; 27 Feb
Maybe I'm exposing my plant to too much light in general. Backed off my LED from Pepe. His remaining leaf looks a little brown/beige. I'm unsure at this point if it's an effect of wavelength or just light exposure.
Log1_6; 5 March
Every seed I planted is sprouting strongly. I have my secondary jar under my desk lit by my LED mood lighting (~640nm, 445nm). My first pot has now been under a 445nm LED, seeing as the 480nm LED I used earlier had no effect on Pepe's growth. Pepe is still alive, but I'm certain his growth is permanently stunted, like Nemo the fish. His one leaf is folded upside down, utilizing the unburned side; a new leaf is sprouting from where the first one left. I have my reservations about starting a new laser build at the moment. I just spent all Thursday from 8am to 10pm at school working on my project, and Friday from 9 to 6 with no sleep in between due to insomnia. Once I'm done with the electrical systems, I'll be much more free to set up a variable output 660 or 445(A140). I'd use an LM317 with a 100ohm potentiometer between the adj and out pins with a limiting series resistor to limit to 350mA. No PWM though, because I've got that going on with the 445nm LED, and the plants don't seem to prefer PWM to CW or versa versa. Now that my new seeds have sprouted I have more reason to implement laser lighting. I was also going to replicate the heating chamber I made at school so that I could bump the temperature up to a more native 90 deg Fahrenheit.. but to be honest, it's 90 in my room during the summer, and it'd probably only be beneficial when I move to an apartment and me wifey wants the AC on. The room temperature at the moment is varied from about 67-70 deg F (I'm using Freedom Units because literature I've found on plants used it).
Log1_7; 13 March
Pepe is dead. The plants under the blue light are growing much faster than the ones in the mood lighting. I hope eventually the strongest pepper will survive and kill the weaker ones. I have to think about transplanting them into a larger container soon.
 

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Laser Chick

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Good luck with that. I don't know how well plants can do photosynthesis on a very narrow or single nm WL.
 

AgentMcBaine

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Good luck with that. I don't know how well plants can do photosynthesis on a very narrow or single nm WL.

They do ok according to Yamazaki, but apparently they need to be supplemented with a second wavelength or else they grow up stunted in some way, like to have narrow leaves and not yielding many seeds. Otherwise it says they mature faster
 
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TheDukeAnumber1

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So is this just for funsies? It's my understanding that plants benefit from several wavelengths in the blue and red parts of the spectrum, favoring either blue or red whether they are in a vegetative, flowering, or fruiting stage.
 

Benm

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In general plants require BOTH to grow well. You can grow a plant under laser light, but it simply requires two colors to work. One of them as to be red (660, 650, 635 nm are all fine), the other has to be blue (445 might work well, but 405 could too).

Both light sources being monochromatic is not a problem for the plant: Both the red and blue absorbing complexes can accept a fairly broad range of wavelengths, and more or less convert the energy to what the plant needs for photosynthesis.

So if you want to grow plants under laser light you may proceed and take apart a combined blu-ray and dvd writer unit. If you use both diodes it should be fine, though you'd have to tune the 405/660 nm ratio to an optimum for the plant you are growing if you want good efficiency. If you just want it to grow you might as well use both at maximum power, though i think you'll be wasting a fair amount of energy in the blue if you do.
 

Laser Chick

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Or just stick the seeds into a combined blu-ray and dvd writer unit and call it good ... JK Thanks for the info Benm!!
 

blueasthesky

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Good experiment! I too tried growing some bell peppers in mid January and that didn't go to well unfortunately, too cold :(

By the time it got warm enough I wasn't feeling it anymore. Try giving them some 593.5nm light they'll love it :yh:

-Alex
 

Cyparagon

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It may be fun to mess around with, but by comparison, LEDs will end up being a lot cheaper, a lot safer, a lot easier to drive, a lot easier to heat sink and a lot more robust.
 

Benm

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Absolutely, especially since you can simply buy leds built specifically for this purpose with built-in drivers that run straight of the mains.

But if you want to do it as a proof of concept, just growing plants under only laser illumination for heck of it, this is absolutely possible to do with the lasers found in a simple bluray/dvd combo writer.

And from a safety perspective this need not be problematic - you can use laser diodes without focussing lenses to get a very broadly spread out light pattern pretty much as you would get from LEDs.

Who knows, perhaps laser-grown chilis will be extra spicy :D
 

AgentMcBaine

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LEDs are definitely a good choice, but I just had this 10mw module lying around so I thought i'd give it a go. The sprout is perking up really fast compared to what my mom's growing under her LEDs (635nm+450nm; good for chlorophyll b). If you look at the third attachment in the OP, it might illustrate part of why i'm up to this. The absorption spectra of chlorophyll a and b are high close to the wavelengths of lasers that are readily available, and it's just strange that there has only been one study done, with a 680nm laser. I have power LEDs in the same peaks, but lasers are cool :p
In all, it was just a last ditch effort to save something from dying. It's cold in my room, about 65 degrees F, and I think this laser might have helped supplement enough energy for the sprout to thrive in this cold temperature. It's a great tool for sprouts, and surprised me since it's only 10mw
 

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Laser Chick

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You might need to change your name from AgentMcBaine to AgentMcGreenThumb :)
 

Cyparagon

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The sprout is perking up really fast compared to what my mom's growing under her LEDs

Just as long as you realize a sample size of one is statistically and scientifically insignificant, and could be explained by differing luminous flux and not the light source type. ;)
 
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AgentMcBaine

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Just as long as you realize a sample size of one is statistically and scientifically insignificant, and could be explained by differing luminous flux and not the light source type. ;)

;P gotcha. Not conducting the experiment though, and I want to officially state that nothing I said in this thread is to be considered as any type of scientific evidence correlating any results to any hypothesis. I just like spicy food
 
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TheDukeAnumber1

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It's cold in my room, about 65 degrees F, and I think this laser might have helped supplement enough energy for the sprout to thrive in this cold temperature. It's a great tool for sprouts, and surprised me since it's only 10mw

How long after planting did it take those seeds to sprout? I haven't tried growing serrano peppers but the heirloom peppers I have tried I needed to regulate the temp to 70F+ for them to sprout quickly.

Reminded me of your experimenting style.
https://www.youtube.com/watch?v=UM-wKQqBBnY


Oh me too! But my intestines say otherwise :crackup:

Lol, same here. My taste buds can handle a lot more than my gut.
 
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AgentMcBaine

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How long after planting did it take those seeds to sprout? I haven't tried growing serrano peppers but the heirloom peppers I have tried I needed to regulate the temp to 70F+ for them to sprout quickly.

Reminded me of your experimenting style.
https://www.youtube.com/watch?v=UM-wKQqBBnY

This is the best thing. First I thought of using the energy from the lemons, but that would have started a fire.

I threw about 5 pepper seeds in and waited 2 weeks, then nothing sprouted and I added a bunch of seeds from strawberries, raspberries, peas, and blackberries, and seeds from pickled jalapeño peppers. Just cuz they wouldn't need to be at 90F to thrive. I think sometime mid-week in the second week I noticed the first sprout, which subsequently died a week after that
 




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