Ceramic Metal Halide (CMH)

[mondragonlloyd]

Confused! Just getting my grow room set for hydroplon,went down and bought the lab,my babies are in the nutes,doing good.I have a 400watt ballast and bulb,so what are the suggestions about which hood to purchase. KINDA LOW IN FUNDS.

 

[down2grow]

Hoosier,

I got inspired by your vertical cab!! What do you think of my cab idea on post #2623?

D2G

 

[master shake]

Umm how can I put this gently...That chart is taken COMPLETELY out of 'context?' and saying '3-6x the amount of light' is a terrible assumption to make. Plants WILL adjust their absorption depending on the spectrum and intensity of the light they have available.

how so man? Do you understand what I was getting at?

I'm no botanist but I deal with graphs a A LOT so I could be misunderstanding...Look at it this way... Have a glance at this graph:

and the graph I posted. Using Chloro. B as an example, it peaks at around 475nm. Look at the SPD chart at 475 nm and compare the HPS to CMH and the CMH produces around 30 on the relative energy scale where as the HPS is virtually ZERO. Or, from the range of 400nm-500nm the average output for CMH is about 30 and for the hps it is probably like what...5??

So, can you explain to me how less output is the virtually same as more output? Since the charts are so out of context...And I never said it puts out 3-6x more light...I said useful light, there's a difference.

 

[master shake]

Thanks for the info, told you I'm no botanist ... So the data in that absorption graph is pretty useless in terms of determining effective light? What exactly does it show?

thanks again


and BTW I never said HPS is terrible for plants...I've been growing with one for 2 years and it has worked very well.

On another note, I've seen people using the cmh or mh for first and last 2 weeks of flowering and using the HPS in between. I know the reasons for doing so but would switching the lights in the middle of flowering stress out the plant? After reading what you've quotes it seems like it may not be a good idea.

 

[LJB]

fyi,

the Philips 400w CMH:

Blue (400-499nm): 20.29 - 25.24%

Green (500-599nm): 38.75 - 39.17%

Red (600-699nm): 35.6 - 40.96%


and

the Osram 400w Plantastar HPS:

Blue: 6.7%
Green: 47%
Red: 47%

Has anyone here conducted controlled, CMH vs HPS flowering studies?

Food for thought, no pun intended - the conclusions from one study conducted using a certain variety of the tomato plant:

http://ncr101.montana.edu/Light1994Conf/1_4_Prikupets/Prikupets text.htm

The qualitative and quantitative effect of each of the three PAR ranges on the formation of the tomato crop is displayed rather clearly...We note the most important significance of radiation is the region 600-700 nm to acheive a high productivity of the tomato community. With a change in the share of Er over 20-75%, the tomato yield can differ by almost 1.7 times; the maximum level of productivity in the experiments was achieved for Er = 75%, although there are signs of saturation of the dependence already for Er = 60-65%. Radiation in ranges 400-500 and 500-600 nm, conversely, is needed in insignificant shares, satisfying evidently, photomorphogenetic processes in plants. Thus, already for Eb = Eg = 15-20% against the background of a high share of red radiation, a drop of tomato productivity is observed. For Er = 35-40% an increase of radiation in the green region weakly affects productivity, an increase of the share of red radiation for Er = 20-40% can lead even to an increase of yield. However, all these effects are observed against the background of a low level of tomato productivity.

questions: - Does the CMH deliver more useful energy than the HPS for a horizontal SOG or SCROG? (keeping in mind relationship of ratio of red to far red and stem elongation)

- Do the differences even out overall no matter what the style of grow? (i.e. less green in the CMH, more red in the HPS)

***

photomorphogenetic processes

When I first read about these (a few days ago), it seemed so intuitive (remember blue spectrum)....In the end, botany is mostly common sense.

Here's a nice little article:

http://www.photobiology.info/prev_mod36.htm

The 'processes' include (1) proximity perception - "The ability to modulate both architecture and reproductive strategy in response to the perceived threat of shading"

(2) Photoperiodic Perception - I hope everyone knows what that is!

 

[ripman]

One reason one might switch to CMH vs. HPS is not about quantity of light and hence yield, but about quality of the product: it seems like, in HPS vs. sun terms, HPS gives a less ceilingless, more "heavy", "body-stone", quality of smoke, hence this might be why some people are trying to find different solutions with respect to HPS.
CMH is said to have a more complete spectrum which includes UVB light, which is said to be what is lacking on the HPS bulbs: the question is then, has anyone experienced a higher quality of smoke using CMH vs. HPS?
If you are not commercial, yield is not totally important, quality counts A LOT more...
Also, light levels are given by how potent is the bulb and HOW CLOSE you can keep the bulb to buds... if CMH can be used nearer to buds, you can have lower effective light coming out of the bulbs but get the same yield, as keeping the bulb nearer, less light is dissipated before reaching the plants...

 

[simba]

Has anyone here conducted controlled, CMH vs HPS flowering studies?

Yes and unfort i can not post my results.others have and shown good results and have moved on from reposting over and over..

I can say if u do a bit of research there is a Pharmaceutical Company in Canada that use CMH for there Grows and they are growing medicine. (for the past few Years, continuously trying other lamps as they come out still with CDM400/S51 cmh)

no one has ever said you will get more with cmh than HPS rather its always been said if you get tuned in you will get same yield with better quality results using a single lamp.. multi lamp depending on setup can go a bit less total watts

Some strains are so Tuned to HPS they take a few grows under CMH to come back to Full SPD.to show results. (that are bread indoors under HPS, mh or even mh/hps combo)

most peeps grow indica because its short as with hps sativa it would be to tall, with cmh Sats stay in check Thus giving you a Heady not Couch Lock (allot of peeps want Sats but cant have height they bring. med users need indica mix.)

another point NGW Reluctantly picked up the CMH, why because it works.
(its not as profitable as HPS for them or any one but the Demand is there because it does Provide the results intended..)
this thread and other threads have been around for so long, if cmh was truly crap or even ok or just ok and not showing true benefits the threads all would have died off long ago..not have a minority haveing issues. (i still havent heard back from a few about there breed and strain and enviro conditions, etc.. IE they have gotten it or gave up early)


to the breeder that is on his 2nd grow with cmh with his breads that have been bread only under MHs and no HPS, i would say it would take a few grows to get it back in .

regarding nute issues.
with using cmh yes its well known they get hungrier than under mh, hps or mh/hps..
There is no way the cmh is causing the plant to not uptake food that would mean full spd is bad for a plant. (super short version)
IE feed bit more after early-early veg and silica is a must..

questions: - Does the CMH deliver more useful energy than the HPS for a horizontal SOG or SCROG? (keeping in mind relationship of ratio of red to far red and stem elongation)

yes, at plant level, because you can keep it closer, and its keeps the plants shorter by having Blue....

take a look below
the top left is our fav plant if u notice its absorption is close match to CMH CDM400/s51 curves (close but not exact) but better than any other MH or HPS or combo mh/hps.

top right, notice full spd is needed for full plant development (again CMH could be better but i think its best we have to choose from)

Par SPD

i like to say going to cmh from hps or mh (combo mh/hps not as bad)
is like going from soil to hydro or vice versa... it has a bit of a curve to it..and the great thing like all things if you are starting off with something it will be easier to learn vs remembering one thing for each style >Ph is dif from chem soil to chem hydro enough to kill a plant if used in other style..
if that makes sense.
if your outdoor or greenhouse cmh is virtually same. or if u make a mix that works outdoors use same indoors and ur good to go..

These are just comments no instigating any thing

Thats long

Peace me going for a walk
.

 

[onegreenday]

Cool graphs Simba. Thanks for posting
so far no side by sides yet (that I've seen)
comparing yield and/or potency (varies by person)
but I read people are doing side by sides.
I would not be surprised of those plant/light response graphs do not apply to all plants but may be a general response graph to the plants they tested.
Those graphs are old as the hills.
Never seen them updated or nuanced.

 

[OsWiZzLe]

The bottom line is...CHM for growing MJ is a big waste of time..i said it first and i'm still sticking with it..if anyone would like some real information on how PAR and all this bullshit applies to marijuana.... look for a user on a MJ website named "gojo". Read his posts and you will finally understand.....

HPS is superior in every way to CMH......I keep sitting on the sidelines on not saying shit about this topic...but now after reading gojo's posts it has become clear....if any of u have the balls to challenge this dude on this topic...hint hint ...i'll see u @ CW

 

[OsWiZzLe]

this was not written by me...but by gojo....

Hello lbj,

I apologize for not responding sooner, I went on a mini-vacation for the 4th.


Quote:
Gojo, contrast and compare that with the results from another study published by Tikhomirov at the very same workshop:

http://ncr101.montana.edu/Light1994C...ets text.htm

Look specifically at table 3.

When I wrote this thread more than two years ago I was just beginning to learn about light, quanta (photon), PAR (Photosyntheicaly Active Radiation), PPF (Photosynthetic Photon Flux), PPFD (Photosynthetic Photon Flux Density), YPF (Yield Photon Flux), etc. I made more than a few errors in the thread starting post. My understanding of photosynthetic reaction was pretty weak, along with my understanding of light qualifications and quantifications. I have been intending to re-read some older threads of mine and correct any mistakes I made or lack of understanding I had. This thread and my blue/red action spectra thread are perfect examples. I will re-read and correct my blue/red action spectra thread this week, along with adding more info...

In the thread starting post I wrote that blue wavelengths offered higher photosynthetic reaction, which is false. It seems true that leafs can more easily absorb blue photons (400-500 nm; eg. "Photosystem II") by virtue of chlorophyll B (and A) and carotenoids; not that blue photons offer greater photosynthesis. I also implied that the PPF of a bulb does not depend upon distance from canopy, which is of course it does.

In this thread I overstated/over implied the importance of photoadaptation, especially when one considers "photosystem I" ('red' light) and "photosystem II" ('blue' light) responses[1]. For example, photosystem I dependent functions like "phytochrome responses" can not be satisfied via. photoadaptation (as far as I know). Another example is photosystem II dependent functions like "blue light responses" which can not be satisfied via. photoadaptation (as far as I know). Some responsibilities of phytochrome responses are 'sensing' day/night lengths, induction of flowing (from longer nights), chloroplast development (not including chlorophyll synthesis), leaf and flower senescence and leaf abscission. Some responsibilities of blue light response are "phototropism" (leaves turning toward the light source), stomatal opening, chlorophyll synthesis and in terms of C.indica and C.sativa THC conversion (especially in UV around 280-290 nm).

NASA suggests a blue:red wavelength ratio of about 1:8 or higher. I assume NASA suggests this ratio because red photons offer greater photosynthetic reaction while blue photons are more energetic. So one would need greater amounts red photons per blue photon (PPFD) to ensure the plants are not over saturated with blue photons.

That said, as long as the light source is "broad-band" (eg. "white light"; HID like HPS or MH) and not a "narrow-band" like LED the "spectral quality" is IMO marginally more important then the plants' "quantum requirements"[2]. For example, a female C.indica plant grown under a MH will produce quality flowers as long as the quantum requirements are met (ex. >500 PPFD). But, the same (clone) female C.indica plant grown under a HPS will produce sub-par quality flowers if the quantum requirements are not met (ex. <500 PPFD). I think this is an important distinction within the studies we are citing. For example, "table 3" from the study you cited only discussed yield, not quality. The authors found a greater percentage of 'blue' light equates to less tomato yield, but the authors didn't mention if they tomatoes tasted worse...

In a perfect world we would all be using the unit of photosynthesis light measurement known as YPF calculated using the "quantum yield" from the target plant (# of O2 molecules released per # of photons absorbed)[3]. For now we can use the YPF which Katsumi Inada created, I prefer his work to Keith McCree's. However, I think "BubbleBlower" mentioned there is a Dutch(?) research group who may be creating a 'new' YPF. The problem with PPF (umol/m^2) and PPFD (umol/m^2/s) is they are "un-weighted". Both units assume all wavelengths within PAR offer the same rate of photosynthesis. And of course that is not the case. Longer wavelengths (green[4] and red) offer higher levels of photosynthesis than shorter (yet more energetic) wavelengths (blue). Not to forget that there are two main absorption peaks in the 'blue' and 'red' spectrums. In other words PPFD is not providing an accurate picture of what is actually happening to the photons' energy once it strikes the leaf. Thus we have the superior unit YPF thanks in no small part to Katsumi Inada, of the "Inada Curve", alternate to the "McCree Curve" from Keith McCree.

YPF is measured from 360 to 760 nm and each photon within each wavelength (a.k.a. "nm" = "nano-meter") is 'weighted' according to plants' photosynthetic response to the photons within said wavelength. PPFD is measured within PAR (400 to 700 nm) and each photon within each wavelength is 'un-weighted', assuming equal photosynthetic response to each photons within all wavelengths within PAR. This distinction is important because we can not compare lamps accurately (ex. MH vs. HPS, etc) if we are using PPFD. One must use YPF because of the wavelength differences from the different light sources. And in fact, it really is kind of impossible to compare white light to LED. There are many reasons why it's hard to compare the light sources accurately[5]. For example it has been found(missing citation) that white light emits only about 85% YPF of red LED YPF, that makes sense but also makes comparisons difficult. Add to those issues the fact of quantum sensor inaccuracies: YPF and PPF from broad-band light sources are more accurately measured with quantum sensors than YPF and PPF from narrow-band light sources. FWIW, IMO the "probe start" HID lamp vs LED argument is moot...IMO the future is of high intensity horticultural lighting will be "pulse start" HID lamps with custom blended phosphor emitting a spectrum closely matching the action spectrum and quantum yield curve of Cannabis spp. (which should be very similar to most other higher herbaceous plants).

A major problem with quantifying photons as PPF/D or YPF is the inherent inaccuracy of quantum sensors, those under a few thousand of dollars anyway. It has been found that quantum sensors are so inaccurate (>10%) that they should be calibrated to a spectroradiometer[6]. This last point is very important because the least expressive 'good' spetroradiometer is about $5,000, and even then it will not be very accurate compared to a more expansive model. The point here is unless each quantum sensor (YPF or PPF/D) is calibrated to the same spectroradiometer they can not be used to accurately measure and compare different lamps. To solve this problem the same quantum sensor must be used for all tests, or each quantum sensor used for testing must be calibrated to the same spectroradiometer. To me 10-20% inaccuracy is far too inaccurate. YPF quantum sensors are more inaccurate (>9%) than PPF/D quantum sensors...

I also came across a few studies by Katsumi Inada[7][8] were he found out of a group of 33 higher plants (26 of them herbaceous plants like Cannabis spp.) all species had near identical action spectrum curves and quantum yield curves. I am ordering a spectroradiometer sometime this year and with the software I can enter the quantum yield curve data from K.Inada and the software will automatically adjust the SPD curve to represent the YPF of the bulb. Then I think it can display the action spectra and quantum yield curve as a silhouette behind the SPD (adjust to represent YPF). I also intend to try and create an action spectra and quantum yield curve of C.indica, C.sativa and the species of "C.indisati"[9] along with other qualification and quantification.

All that said and considering Katsumi Inada's two studies regarding the action spectra and quantum yield curves I now see little reason for Knna's 'hacked' Cannabis quantum yield curve....or my possible attempts at creating a real quantum yield curve for Cannabis spp. ...

FWIW: I prefer using the "Inada curves" to the "McCree curves". I hope this is what you were looking for, there is more that can be written but I tend to labor on, and on. Oh yea, welcome to the site



[1] "Phytochrome: Light Regulates Plant Growth and Development"



[2] "Properties of Light that are Important for Photosynthesis"
by Donlad R. Geiger



[3] "A Companion to Plant Physiology, 4th Edition: Topic 7.3: Quantum Yield"
by Lincon Taiz and Edurado Zeiger



[4] "Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green"
by Ichiro Terashima, Takashi Fujita, Takeshi Inoue, Wah Soon Chow and Riichi Oguchi; 2009

I just read that very intriguing study which states that under "intense" while light such as HID green wavelengths offer higher photosynthetic reaction than red wavelengths (I assume >1000 PPFD is "intense" enough).



[5] "Introduction – LED Based Plant Growing"
by SolarOasis Research Labs; White Paper; 2007



[6] "Accuracy of Quantum Sensors Measuring Yield Photon Flux and Photosynthetic Photon Flux"
by Charles Barnes, Theodore Tibbitts, John Sager, Gerald Deitzer, David Bubenheim, Gus Koerner and Bruce Bugbee



[7] "Action spectra for photosynthesis in higher plants"
by Katsumi Inada



[8] "Spectral Dependence of Photosynthesis in Crop Plants"
by Katsumi Inada

 

[LJB]

Maybe it can be said that the CMH is superior to the MH-HPS, for Indica dominant strains, in particular the aforementioned SOG/SCROG.

And I would think that the MH-HPS combo is superior for Sativa dominant strains, tree and bush grows, VSCROG with two or more stacked bulbs and several tall plants surrounding in a circle, etc.

 

[simba]

onegreenday,
ya some those charts are old.
the top left is actually same from DEA yups DEA..
its what they use to find Pot in open grows with reflection technice.

LJB "Maybe it can be said that the CMH is superior to the MH-HPS, for Indica dominant strains, in particular the aforementioned SOG/SCROG."
~Yups, lights can be super close without heat and full spd bennies (short version)

"And I would think that the MH-HPS combo is superior for Sativa dominant strains, tree and bush grows, VSCROG with two or more stacked bulbs and several tall plants surrounding in a circle, etc. "
actually cmh is best proven when used on sativias,
my prob with combo bulbs.
1. cost more to operate/replace 2 lamps vs 1.
cmh has FULL SPD combo doesnt. and mixing the spd is harder with combo and more costly.. for no benifti from a single lamp with all spd.


Im going to make a single gallery of all cmh photos good and bad (some are lanky newbies to cmh/growing but shows cmh qaulities with or without knowing how to grow when starting..

some pics from people here showing there results. some where lucky i think in dialing in so fast.

400 W Vscrog.

Hello everybody, hello Simba !!
This was my first harvest under CMH 400W (first grow, 5 girls)
About 230g (8 oz) of very nice quality !!
Here is a bud of my favorite, KO Kush (******) :
http://www.icmag.com/gallery/data/500/29999dachop.JPG

Greensgolds first harvest.
First CMH in the books. To many varibles to really comment, but it was by far not one of my best grows. Here's a pic at the nine week chop.

from our good freind AZ,

The following pics are some of a "bonus mix" that one of reefermans guys sent me a few years back. I feel stupid that the leaves show so much nute burn, but I have found some nutes that I can get locally that are working well in coco. I have yet to dial in the dosage on the 3-20-17 bloom booster.LOL











The next is a JohnnyBlaze Girl




And some SweetBlue(m) X JohnnyBlaze(f) that are in 90%coco/10%EWC and 12/12 from seed.

from MPL the thread starter,

Harvested one of my plants. The buds were too heavy for it to hold up anymore and I wanted to try some early harvest bud anyway. It was maybe 50/50 cloudy/clear.













And here is the larger of the two. I'm going to keep it until it is 50/50 cloud/amber. It's also starting to drop its colas.

This is GHS The Church grown under a 250 cmh the yeild on just this one plant was around 50g I smoked a bunch before I weighed couldn't resist

Nice job Doug!!!! How was the smoke?

Just for those folks that have been claiming that the CMH causes too much leaf and all that jazzz.








Now I have to admit that I burned the **** out of these girls playing with new nutes and such.

 

[simba]

i love this one so im showing again..
there is to many pages for others to go threw all so im picking out goodies to show. Good and bad..

theres physics (gravity, Electro mag fields) and Chemistry in play in regards to burning position IE hor or vert>> in the hps retros there is a Dif.. 250-400 (20-150 dont matter)
if you burn in wrong position life and color is affected.. shortened version..

if your like 90% of us you want horizontal..

This is horizonta setup .. but i been asked the temp Q's..
if this was HPS in exact same setup (IE if i switch out the cmh for hps) i couldnt do this..
DOnt try this at home.. Yes its warm but Not HOT well gets toasty
yes i am gripping the bulb..

 

[simba]

sorry im quoting a few grows. so pages may run but its worth the data .

Hey guys I finally got a comparison going between the the Phillips CMH (400 watt) and the Hortilux EYE HPS (400 watt).

My experiment is far from scientific, but hopefully it will shed some light (no pun intended) on how much (if any) better the CMH is compared to a HPS growlight.

To do this I built a SCROG using Wallyducks C99xHaze (5 clones + the mother plant). The screen is 2x4, with half of it covered by (half of) the CMH, and half of it covered by (half of) the HPS.

Well they say a pictures worth a thousand words, so here ya go:

Just the Scrog:


With the other plants in the room:

 

[simba]

and another goodie

TGT - yep, all the same strain GH SSH. They were all vegged with the 400W CMH and then when I fliiped to 12/12 I added a 250W HPS on the right side. The canopy was even (flat) when flowering started The left side stayed shorter, started flowering sooner, and are further along. Do not forget that we are comparing a 250W HPS to a 400W CMH, but they difference in the stretching is unreal. CMH all the way. I hope to get the 250W HPS into a CMH working, thanks for the ideas and keep any more suggestions coming.

Week 2 of flowering with HPS off for picture only (notice the two lights are even)


After 5 weeks of flowering (the HPS is still in there, but just way up high (along with the plants))


N dubbya

 

[simba]

and another..
Ikes i need to get a gallery for all CMH photos. in one spot. but this shows it for now.
Again ur choice but make an infomed one..

Hello,

KO Kush (******) just before harvest :










Rebel Shack F2, from ****** too :






an other Rebel Shack F2 :








and this is a Sweet Tooth 1.1 from Spice of Life :








All plants are J+73 of 12/12 under CMH 400W.

It was my first grow and I am very happy with that CMH bulb, thank you Simba !!

 

[simba]

yet another

Here is an update for my C99xHaze scrog, now at 4 weeks flowering.

The right side Is lit by a Hortilux EYE HPS. The left side is lit by a CMH.
Both bulbs are 400 watts.

I had to leave town after the second week.....so i stopped training them then.
You can see how much the pladies stretched during that time.

Second Week:



Fourth Week


Fourth Week CMH Side:



Fourth Week HPS side: (Sorry about the pic quality....CMH gives way better pics)



And a shot of the full box......with the other plants in there:




I'll update next week.....no conclusive evidence yet.

Heres my two babies that have been under a 250 CMH. Week 4 of 12/12

PK -

G13 -

here are a few shots of my current NL scrog under 2 x 400w cmh. my 1st attempt at a scrog. Im liking it so far.

these are on day 31 of 12/12.

in addition to the cmh's, I also have an hps added in there for some additional red spectrum. I originally had it right between the cmh reflectors and it seemed the plants were all leaning to the middle towards the hps. I moved the hps to the back wall last weekend and angled it out over the scrog. now all the buds are standing at attention to the cmh's.

regards,
JT

 

[simba]

dd

if u notice one of the growers below gots about .74 GPW first time around..
not bad not Greatest but first time with cmh..

This is GHS The Church grown under a 250 cmh the yeild on just this one plant was around 50g I smoked a bunch before I weighed couldn't resist

A 400w CMH bud for the non-believers.. It's as fat as a 2 liter bottle.

Just chopped the Reeferman bonus mix girl tonight. Looks great, budz are hard, smells very sour!!!!










I'm guessing 3 1/2 to 5oz.

800w CMH = 632 Grams in soil

Next run I know I will get 800+ Grams and surpass the 1/1 gram/watt ratio with an additional scrog and clones of 1 know producer.

 

[simba]

go back a few pages to 178 to see all pics. reposted.from earlier.


Cant stress enough go with good breads and good genetics

CMH wont make more leaves than the plant will under the sun.... the plant has those leaves waiting to come out to work but under hps its not worth it.

Not a doubt in my mind that CMH performs well.
Made my calyxs swell like hard nipples lactating resin.
Which of course, makes my nipples hard.

CMH all day.

I call shenanigans.

One months veg and 17 weeks of flower



No veg and 21 weeks of flower



My current grow specifically calls for 30 days of veg for maximum yield. Why? Because veg has a profound effect on yield.

Another evolutionary step for mankind...

1600 watts of Ceramic Metal Halide, running STRONG! Follow the link in my sig, to watch the show. Should be fun!

 

[LJB]

Great photographs...

This paper lends itself to the pro-CMH camp:

http://ncr101.montana.edu/Light1994Conf/1_3_Tikhomirov/Tikhomirov text.htm

Therefore, usage of the curve for action spectrum of photosynthesis is not correct in light regulation under long-term stationary regimes, since certain reactions to spectrum and intensity of PAR aren't taken into consideration. All spectral requirements obtained under short light influence tests have similar limitations.

What should be done? It's necessary to be guided by data obtained under long-term influence of spectral and intensity characteristics on photosynthetic plant systems and even better on canopies of plants. These are the photosynthetic structures which ultimately form to produce the harvested yield. We've obtained some results which support this conclusion. These are some of the universal responses (Tikhomirov et al., 1991):

1) The time for maximum affectivity of photosynthesis of plant canopies appears earlier with red (600-700 nm) and later may shift to shorter wave length regions of PAR. This shift depends on specific plant reaction to spectrum of PAR;

2) The relative effectiveness of blue rays increases and green and red rays decreases with higher levels of irradiation (Fig. 2 and 3);

3) Maximum photosynthesis of canopies is possible only under combinations of blue, green and red radiation. Any kind of combinations of two of these wavebands or with only one spectral region, always reduces productivity.​

[..]

It is not necessary to provide light conditions for maximum photosynthesis of every plant leaf but to provide light conditions for optimal photosynthesis of the plant canopy.