What's new
  • Please note members who been with us for more than 10 years have been upgraded to "Veteran" status and will receive exclusive benefits. If you wish to find out more about this or support IcMag and get same benefits, check this thread here.
  • Important notice: ICMag's T.O.U. has been updated. Please review it here. For your convenience, it is also available in the main forum menu, under 'Quick Links"!

Green Diarrhe

f-e

Well-known member
Mentor
Veteran
I'm doing a green light experiment. Just green. No blue, red or far red messages for the plants. Just a colour that others like myself have used many times for night illumination.

I once had a green led on an negative ion generator 24/7, that had a bud beside it develop extraordinarily well. Then put 100 leds in to try again, and it did nothing.

The PAR charts we see show green works at perhaps 30% the efficiency of red or blue. I'm not sure if these charts are the nasa research that just used monochrome light. Or full spectrum with bands of interest increased. Plus the charts are not our plants anyway. I want to start again myself, with the right plant. Just green light this time.

So, I have a cutting taken a week into flower. Rooted and vegged a little while. Still at 3 blades like early veg. It should express flowers quickly, if it chose to. Or carry on it's veg cycle. Or keel over. All within the next week.



The hardware involved is a 20w green led, on a cpu cooler, in an aptly named 'bud box'

The chip


The plant


The group shot


The bud box


The story starts here



Place your bets now! Will the 20w work like a 7w as the charts suggest, or will something canna specific come to light
 

Hookahhead

Active member
Checking in, excited to see what happens. I expect that cannabis can use some green light, but blue and red are much more critical. Personally, I like the idea of the RGB LEDs run at 100:25:75 respectively.
 

f-e

Well-known member
Mentor
Veteran
I think my lack of blue could be a real issue. A token amount is needed. A sodium gives off enough at our illumination levels, but growing plants under less light (other plants) requires things like the green power, and less still means using the argo with its further addition of blue light. So if I do get growth like a 7w lamp, it will be leggy like it was a 7w amber. Which I have seen done, using sox lamps (low pressure sodium)

I have the popcorn out, hoping I might even grow some more :)
 

mayorofthdesert

Active member
i wonder how mu green light would actually be absorbed & used. the plants reflect green, that's why they look green. i'm sure it does absorb some wavelengths but i'd think a lot gets wasted
 

f-e

Well-known member
Mentor
Veteran
i wonder how mu green light would actually be absorbed & used. the plants reflect green, that's why they look green. i'm sure it does absorb some wavelengths but i'd think a lot gets wasted

PAR graphs suggest maybe 65% less efficiency than red or blue. Recently there has been talk of green light having better canopy penetration because of this lack of interaction. It's not just the story of this 65% bouncing straight back. Though as you have seen, some clearly does.

I have no means to test this. Perhaps a side by side using my 20w green and a 7w full spectrum could lead to a weigh-in of green matter to see how much of the 20 is wasted. I don't expect the same growth pattern, so a weigh-in might be the answer. I'm not legal here though, and don't value that knowledge above my freedom. Not unless I see something interesting over the coming week(s)



I'm pleased to see people are interested. My results alone might be meaningless, but shine a light on something else in the future. Somebodies gotta do it.. :)
 

Hookahhead

Active member
the plants reflect green, that's why they look green.

This is stated matter of factly so often. In actuality it's a gross over simplification of a complex issue. Unfortunately It's also proven untrue. To see for yourself, go out into the forest and look up at the canopy. You can actually see light passing through the leaves. It's mostly green light that trickles down to the forest floor in this manner, and it has a significant impact on plant growth/regulation. Especially considering this might be the only light a plant receives for most of its life, until a tree falls opening a shaft of strong light. Then the plants have explosive growth to try and out compete others for the precious energy. Green light definitely makes in impact on plants, but it's difficult to establish what the effect is based on the published research. Incidentally, the effects of green light on cannabis are even less understood.
 

Ibechillin

Masochist Educator
The main thing thats been spread around about green light that bothers me is people saying it wont interrupt the plants dark cycle so you can work in the room/on plants during lights off. Good info on light filtration Hookahead, it seems the most efficient use of green light is on the bottom side of leaves.

Here is a link to the study i referenced in the lighting science sticky about green lighting (PDF) download button on right in blue:

https://www.researchgate.net/profile/Riichi_Oguchi/publication/24043711_Green_Light_Drives_Leaf_Photosynthesis_More_Efficiently_than_Red_Light_in_Strong_White_Light_Revisiting_the_Enigmatic_Question_of_Why_Leaves_are_Green/links/0fcfd512c13512536a000000/Green-Light-Drives-Leaf-Photosynthesis-More-Efficiently-than-Red-Light-in-Strong-White-Light-Revisiting-the-Enigmatic-Question-of-Why-Leaves-are-Green.pdf
 
Last edited:

Betterhaff

Active member
Veteran
We used green light in the lab as a safe light when working with sprouts and seedlings (kind of like red light in the dark room). It kept them from producing much chlorophyll. Interested to see your results.
 

f-e

Well-known member
Mentor
Veteran
The main thing thats been spread around about green light that bothers me is people saying it wont interrupt the plants dark cycle so you can work in the room/on plants during lights off. Good info on light filtration Hookahead, it seems the most efficient use of green light is on the bottom side of leaves.

Here is a link to the study i referenced in the lighting science sticky about green lighting (PDF) download button on right in blue:

https://www.researchgate.net/profile/Riichi_Oguchi/publication/24043711_Green_Light_Drives_Leaf_Photosynthesis_More_Efficiently_than_Red_Light_in_Strong_White_Light_Revisiting_the_Enigmatic_Question_of_Why_Leaves_are_Green/links/0fcfd512c13512536a000000/Green-Light-Drives-Leaf-Photosynthesis-More-Efficiently-than-Red-Light-in-Strong-White-Light-Revisiting-the-Enigmatic-Question-of-Why-Leaves-are-Green.pdf

I think that was a very long winded paper, telling us red and blue are soon intercepted, while green passes further through the tissue before it to is intercepted. Not because the tissue is layered in any way, it's just there are fewer receptors for the green. Thus the lower tissue is making more use of the green. Not because it favours green, but because that's all that is left.
The forest floor explanation nails it. By the time light reaches the ground, most of the red and blue has gone, leaving the light dominated by the green spectrum. The plants can live on that green. They really want a tree to drop though, to get red and blue.

I did get a sniff of something from that paper. Red and green basically make plant tissue, weight for weight. Blue makes less tissue, because some is used a lot for another interesting process. Flavour.


It was all a bit to deep to be of any use to me, but they also spoke of monochrome green having a different effect when accompanied by white light. Which I had imagined myself. A real test would be a side by side, where a pair of 20w whites illuminate one cutting. In the next bay another cutting gets 20w of white and 20w of green. If enough material is present to use the green up, Then we should see slightly more weight, and less taste. As green like red makes weight, while a comparatively greater proportion of blue goes to taste. Realistically, we probably wouldn't get a conclusive result without running the test many times and summing the results. CMH users report a taste change compared to son, but it's just a change. Not a trade of weight for a greater amount of taste.

Actually.. that's not the green having a different effect. I may need to read that paper fully. Not just skim over it.
 

f-e

Well-known member
Mentor
Veteran
I couldn't resist an early peek. About 16 hours in the box.

I potted up as it went in, which would usually perk them up a bit anyway. It's pissing all over the 3 control plants though.

I don't think anybody expected that :thinking:
 

Ibechillin

Masochist Educator
I think that was telling us red and blue are soon intercepted, while green passes further through the tissue before it to is intercepted. Not because the tissue is layered in any way

I may need to read that paper fully. Not just skim over it.

My takeaway from the paper reinforced the benefits of utilizing light movers, overlapping, side or vertical lighting and reflective material to stimulate and saturate chloroplasts in the top and bottom of the leaves simultaneously. When the adaxial (top) surface's chloroplasts become saturated (like from indoor horizontal overhead lighting) photoinhibition takes place on that surface, but not on the abaxial (bottom) surface chloroplasts.

Leaf pigment and thickness both have an effect on light transmission and how the adaxial (top) or abaxial (bottom) sides of a leaf reach photosynthetic saturation. Darker pigments absorb more light and allow less to pass through, Thicker leaves allow less light through as well. This also helps explain the relationship and benefit between the sun rising, dropping and traveling across the sky (as well as light movers) providing different angles of illumination on the same leaf.

From the paper:

"The chloroplasts in the lowermost part of the leaf absorb <10% of those in the uppermost part, even at a wavelength of 550 nm at which the absorption gradient is most moderate. For spinach, various estimations have been published. Using the method of Takahashi et al. (1994) , Vogelmann and Evans (2002) and Evans and Vogelmann (2003) indicated that, on a unit chlorophyll basis, the chloroplasts in the lowermost part absorb about 10 and <20%, respectively, of the green light of those in the uppermost part. For wavelengths with strong absorption, such as red and blue, the fractions are much smaller. In C. japonica , the absorption of 680 nm (red) light by the lowermost chloroplasts is <2% of the absorption by the uppermost chloroplasts on a unit chlorophyll basis. For blue light in spinach, the estimated absorption by the lowermost chloroplasts was <5% of that of the uppermost (Vogelmann and Evans 2002 , Evans and Vogelmann 2003 ).

The profiles of photosynthetic capacity along the gradient of light absorption have been reported for Spinacia oleracea ( Terashima and Hikosaka 1995 , Nishio 2000 , Evans and Vogelmann 2003 ) and E. paucifl ora ( Evans and Vogelmann 2006 ). The differences in photosynthetic properties found between the chloroplasts in the upper and lower parts of the leaf are essentially identical to those found between sun and shade leaves, or between sun and shade plants ( Terashimaand Hikosaka, 1995 ). Based on observations of the differences in the shape of light response curves depending on the direction of irradiation, Oja and Laisk (1976) predicted the existence of an intra-leaf gradient in photosynthetic capacity. The most efficient situation is realized when the profile of light absorption and the profile of photosynthetic capacity are perfectly matched, and all the chloroplasts in the leaf behave synchronously with respect to photosynthetic light saturation ( Farquhar 1989 , Terashima and Hikosaka 1995 , Richter and Fukshansky 1998 ).

When leaves are irradiated from the upper side, therefore, there will be a situation in which the upper chloroplasts are light saturated while the chloroplasts in the lower parts still need additional light to reach saturation. In other words, the quantum yield of photosynthesis differs within the leaf.
 

aridbud

automeister
ICMag Donor
Veteran
The chlorophyll in the plant absorbs the red and blue light much more readily than the green light. Green light is the least effective for plants because they are themselves green due to the pigment Chlorophyll. Blue light, for example, helps encourage vegetative leaf growth.

If green were to help plants grow, they'd be in all LEDs. Combo R, W, B in the amounts Hookahhead posted earlier.
 

f-e

Well-known member
Mentor
Veteran
My takeaway from the paper reinforced the benefits of utilizing light movers, overlapping, side or vertical lighting and reflective material to stimulate and saturate chloroplasts in the top and bottom of the leaves simultaneously. When the adaxial (top) surface's chloroplasts become saturated (like from indoor horizontal overhead lighting) photoinhibition takes place on that surface, but not on the abaxial (bottom) surface chloroplasts.

Leaf pigment and thickness both have an effect on light transmission and how the adaxial (top) or abaxial (bottom) sides of a leaf reach photosynthetic saturation. Darker pigments absorb more light and allow less to pass through, Thicker leaves allow less light through as well. This also helps explain the relationship and benefit between the sun rising, dropping and traveling across the sky (as well as light movers) providing different angles of illumination on the same leaf.

From the paper:

"The chloroplasts in the lowermost part of the leaf absorb <10% of those in the uppermost part, even at a wavelength of 550 nm at which the absorption gradient is most moderate. For spinach, various estimations have been published. Using the method of Takahashi et al. (1994) , Vogelmann and Evans (2002) and Evans and Vogelmann (2003) indicated that, on a unit chlorophyll basis, the chloroplasts in the lowermost part absorb about 10 and <20%, respectively, of the green light of those in the uppermost part. For wavelengths with strong absorption, such as red and blue, the fractions are much smaller. In C. japonica , the absorption of 680 nm (red) light by the lowermost chloroplasts is <2% of the absorption by the uppermost chloroplasts on a unit chlorophyll basis. For blue light in spinach, the estimated absorption by the lowermost chloroplasts was <5% of that of the uppermost (Vogelmann and Evans 2002 , Evans and Vogelmann 2003 ).

The profiles of photosynthetic capacity along the gradient of light absorption have been reported for Spinacia oleracea ( Terashima and Hikosaka 1995 , Nishio 2000 , Evans and Vogelmann 2003 ) and E. paucifl ora ( Evans and Vogelmann 2006 ). The differences in photosynthetic properties found between the chloroplasts in the upper and lower parts of the leaf are essentially identical to those found between sun and shade leaves, or between sun and shade plants ( Terashimaand Hikosaka, 1995 ). Based on observations of the differences in the shape of light response curves depending on the direction of irradiation, Oja and Laisk (1976) predicted the existence of an intra-leaf gradient in photosynthetic capacity. The most efficient situation is realized when the profile of light absorption and the profile of photosynthetic capacity are perfectly matched, and all the chloroplasts in the leaf behave synchronously with respect to photosynthetic light saturation ( Farquhar 1989 , Terashima and Hikosaka 1995 , Richter and Fukshansky 1998 ).

When leaves are irradiated from the upper side, therefore, there will be a situation in which the upper chloroplasts are light saturated while the chloroplasts in the lower parts still need additional light to reach saturation. In other words, the quantum yield of photosynthesis differs within the leaf.

I see. So while a single leaf could catch any colour, anywhere, the ratio of green receptors is higher on the bottom.

I made some uplights using white leds. I saw more gpw (grams per watt) from them, than the 600s overhead. My story is, that lower foliage had previously been growing air-bud with power made elsewhere in the plant. There is obviously good reason to chop this stuff off in a scrog. But just how much.. not knowing quite what would stretch up and be useful, and what might just leave a hole.

So, I made up some uplighters in white (and burple). Then grew so much lower foliage that it was shocking. That all comes off at the end of grow, but taught me the uplights are only for flower. Which if we look at the gpw figure again, becomes more impressive as we think g/kwh because these lights are not used in veg. My uplights are the best lights I have.

The burples appeared to produce just as much lower foliage as the whites.

While it's interesting to know whats happening in an individual leaf, it's how the plants as a whole respond that's meaningful to me. The mechanics that we can control. Light movers. Interlighting. Energy we could apply at night perhaps. Which is what I'm really interested in with this green light experiment.

Lots of plants will be preying like mine before lights on. It's happy, but wants more light. It could soon be exhausted though. We will have another look in around 9 hours.
 

Hookahhead

Active member
Here is me rambling for little bit.. Plants do appear green because a good amount of green light is bouncing off them. However again this explanation is grossly over simplified.

The truth is plants are pretty inefficient at absorbing/utilizing light energy in general. In best case scenarios only about 30% of photons are absorbed (Other inefficiencies within the plant means that even less is actually converted into biomass). This means a "green" plant under normal conditions is also reflecting back lots of purple, blue, yellow, orange, red light. However, our human eyes only have receptors for red, green, and blue. Since the chlorophyll does absorb a greater portion of the red and blue, the plant appears green... but this is a physical limitation of the human body not the plant. When the chlorophyll breaks down (think of tree leaves in the fall) we see the leaves change color because less of the red and blue is being absorbed by the leaf. Under absolutely perfect lighting conditions, the plant should appear black because it's absorbing all of the light.

LED is the first type of lighting that we can use to target specific wavelengths. Research in this area is progressing rapidly, but we still haven't fully dialed in this technology. By providing light in the appropriate quantities, we make the system much more efficient by eliminating the wasted photons. However, plants are complicated organisms and therefore it's hard to determine the exact effect a specific wavelength of light has on a plant. Just because a plant grows a certain way under 100% blue light doesn't necessarily mean blue light causes that type of growth. Instead, that type of growth might be because the plant is compensating for something it's lacking.

We know that all of the hormones in a plant work in at least a 2-way balance to regulate plant growth. For example, applying just auxins or cytokinins alone will produce very noticeable and specific changes in growth. So at first glance it's easy to attribute that growth to either auxin or cytokinin, but further research has revealed that it's actually the ratio of the two hormones that determines the outcome. Likewise, we have to be careful to avoid this in assessing how a specific wavelength effects the plant.

Another unique feature of LED that is just starting to get some attention is their ability to turn on and off rapidly and efficiently. If you've ever played with those remote control RGB lights, they run off of PWM (pulse-width modulation). It's basically a timer that allows the diode to switch on and off rapidly. The advantage is that you can blink a LED on and off so quickly that it appears as continuous light, just slightly dimmer.

In my opinion, this is where we will find the next big advance in grow light technology. People like to think of plants as machines... if we use more nutrients, water, and light it should grow bigger/faster! All of us learned early on that's simply not how things work. We know it's possible to photosaturate a plant, where any additional light is wasted. However, it's quite possible that we might find certain "flash patterns" that overcome these obstacles. A simple Arduino or RPI controller puts the technology in everybody's hands.

These are all purely hypothetical scenarios, but an idea of what could be possible in the future... For instance, maybe running a strong light, that switches on and off every 1/4 second might produce the same growth as continuous lighting by allowing the plant to "rest" in those 1/4 second off periods. The light would then be 50% more efficient! Another possibility would be to flash 2 different wavelengths independently. In this example, you could flash blue at one interval and red at another. There's a lot of room to experiment whether it's best to over lap them, or run one while the other is off. I find it completely ironic, that a flashing blue and red police light could potentially make a great grow light. :biggrin: The last scenario is to try and mimic a normal daylight cycle. This would be a bit more complex, but you would have mostly red starting the day (sunrise) with more blue filling in through the day with almost all white (RGB) by noon. Then you would start to taper the blue off again so that it's mostly red/farred at sunset. If any of these lighting conditions produces good growth that is on par with "normal" growing conditions, it could greatly increase the efficiencies of our lighting systems. Within the next 10 years 2g/w will be the new standard.. not because of greater yield but because of wasting less photons.
 

f-e

Well-known member
Mentor
Veteran
Good read.
I think we have done some flashing light stuff without realising. The bars seen on peoples photo's sometimes, are there because their lights are strobing. Watching rotating machinery with a single fluorescent light can give the impression it's stationary. That's really quite slow though. When I think about it, colour is only our perception anyway, and meaningless to a plant. It just gets bombarded by photon's that themselves have a different frequency. Wavelength and frequency being directly proportional. Led's are some of the first non-strobing lights in the mainstream. Though most do strobe still. It depends on the control gear. It seems we have looked at a lot of switching frequencies already and found no effect. The only purposeful experiments I know of are with strobe lights. I believe 1000w without strobing is the same as 2000w that does strobe. Plants just don't respond that quickly. And that any alternating behaviour between different colours will be more like an hour of each, not microseconds. Where do we start though? I'm guessing the daylight replication, but a lot more daytime spent at full light. With lower levels serving as repair or transition periods.


Back to the program... It's happening...
The top of the plant is growing single blade leaves. The main stem looks a little like a plant re-vegging. With alternating lumps on each side that are likely tiny curled up leaves. Air temps is 25c but at maybe 100mm from the led, heat stress at the tip needs checking. As it can also have a 'spudding' effect.

I dunno what, but it's going on. This isn't normal growth. It's like flowering without any flowers. I will get a better snap tomorrow


48 hour shot


In the pic, I don't see it trussing up like a Brussel Sprout. Maybe I just got that impression seeing a leaf or two, and having seen that behaviour before. Wishful thinking at just 48 hours. I will get a snap soon. So you can see for yourselves
 

f-e

Well-known member
Mentor
Veteran
I think I missed day 3. I'm also thinking the single blades might of appeared in the first 24 hours, and nothing much has happened since. No growth. No death. No white hairs on the more recent growth. However, there could be a little more flower development where there was some already, along with more resin along the leaf boarders. The camera struggles to pick it up though.

A plant in darkness would by now be looking different. This really isn't doing much though.


Temp at the tip was 28c. Perfectly fine.
 

f-e

Well-known member
Mentor
Veteran
Day 5.6

Calcium signs. It's hot enough, bright enough and fed enough. Maybe a bit higher humidity than I'm used to, and no air movement though. That could be reducing it's uptake. I think it's me... not the light. There are signs of growth though.

These are the 16 hour and today pics, side by side.


The top has developed over the last 1.5 days


But it's asking me to pay it some attention




I must be a great grower, in my first diary, I'm really killing it.


A plant in darkness would try and grow a couple of top leaves in this time, but would of made small ones in a very light colour. And quit after 3 or 4 days. I have left them in the dark for a week or so before, with maybe 20 mins light a day. They bounce right back when under light again. I should of really put a control plant in total darkness. My bad.


Killing it! lol


What we can see, is that green certainly isn't ignored by our plants. It's likely the 30-40% efficient that we read about. This plant isn't vegging though. It's moving towards single bladed leaves and today you might see the calyx's starting to form, that it had stopped doing (it's a reveg remember)
 

f-e

Well-known member
Mentor
Veteran
Okay, nothing to see at the usual resolution, so lets get a bit closer


I think you can see what's going on here. It has barely any interest in heading upwards, and hasn't even got a growing tip as such. The top is bunching, and maybe it's age hasn't changed, or maybe it's heading into flower. But there are no white hairs. Just frosty calyx.


This seems to be heading in the direction I wanted. With green light sustaining life, but not stopping the flower cycle.

Early days...

Edit: That's not a calyx.. It's a leaf !
 

f-e

Well-known member
Mentor
Veteran
Mixed feelings about today's findings. It's a game of spot the difference.

That one was a comparison, 90 hours apart.

That's the 6.6 day, and today's 8 day picture. About 35 hours apart. Can you spot the latest?

My optimism needs dialing back a bit.

Coming up to the third feed in coco. There looking a bit green to me. Or maybe yellow. They could even glow in the dark from what I can tell. They're neither growing or dying. They're just sat there, with no heads, yet alive. It's Zee-Weed
 
Top