What kind of light mj 'likes ' ? Decoded from it's reflectance ....

This is why I think HPS works so well. It has a ton of yellow to feed the lower branches, and far-red to lower %PFr there so it wants to stretch to the "good" light. causing the tree shape.

Look at the slope/gradient in the 640-760nm range. That's probably the slope for red/far-red we want to emulate considering the HPS spectrum seems to work so well.. It looks like there's about twice as much percent of relative energy at 660nm as 730nm so a 2:1 ratio of output power could be good to emulate HPS.



TL;DR: Green, Yellow,orange, and far-red penetrate more and cause %Pfr at lower branches to be lower and thus stretch.

Here's something I posted in UK420 on 31 August 2009 - 04:18 AM that explains my theory:


"I just made this with paint. This picture demonstrates the first 3 layers of a plant absorbing a full spectrum light source. Its only an approximation so bear with me.

This again shows penetration vs quality. Notice that the more layers the light goes through, the lower %Pfr will converge at. This assumes you start with a full spectrum!!! if you only have a 660nm light source, the entire plant will converge at 85% eventually, you're telling the lower branches their light source is perfect, when in reality hardly gets any light at all. Having the yellow there gives a contrast of %Pfr between higher and lower layers of the plant. this is one reason I think led grows tend to fail and HPS do so well. Also, the yellow itself allows bottom layers to get some light."

"I made one more diagram to continue my story. This picture demonstrates the common LED grows we've seen and my analysis."


(you can really tell this is written in 2009, lol)

churchhaze said:

Here's something I posted in UK420 on 31 August 2009 - 04:18 AM that explains my theory:


"I just made this with paint. This picture demonstrates the first 3 layers of a plant absorbing a full spectrum light source. Its only an approximation so bear with me.

This again shows penetration vs quality. Notice that the more layers the light goes through, the lower %Pfr will converge at. This assumes you start with a full spectrum!!! if you only have a 660nm light source, the entire plant will converge at 85% eventually which i'd say is like lowering interest rates to attract a housing bubble

you're telling the lower branches their light source is perfect, when in reality hardly gets any light at all. Having the yellow there gives a contrast of %Pfr between higher and lower layers of the plant. this is one reason I think led grows tend to fail and HPS do so well. Also, the yellow itself allows bottom layers to get some light."

"I made one more diagram to continue my story. This picture demonstrates the common LED grows we've seen and my analysis."

Click to expand...

Well ...I guess you really knew from back then ...
(But back then White pc leds ,were not as good like modern are ..From plenty of aspects .. ) .
Yes ...Your graphs ,pretty much -for me -,are correct and the whole 'explanation' stands just fine .
Thanx ,for enriching this thread .
Any idea -graph-link-pdf-pic-article-thought-etc ,on this subject, will be & is much appreciated .

Can't rep you .I've to spread some first .Know that you deserve it ,though ...

Unfortunately, I haven't yet invested in my own LED setup. I'm waiting for 730nm leds to come down in price before I switch from HPS.

The products out there are starting to look very promising, and once 730nm sleep inducing is more common and cheaper, I'll definitely join the experimenting.

I've been considering a flourescent + 730nm grow myself for flowering, but those 10W 730nm arrays cost like 160 dollars still....

stardustsailor said:

Well ...I guess you really knew from back then ...
(But back then White pc leds ,were not as good like modern are ..From plenty of aspects .. ) .
Yes ...Your graphs ,pretty much -for me -,are correct and the whole 'explanation' stands just fine .
Thanx ,for enriching this thread .
Any idea -graph-link-pdf-pic-article-thought-etc ,on this subject, will be & is much appreciated .

Can't rep you .I've to spread some first .Know that you deserve it ,though ...

Click to expand...

You know that are some warm white leds ,that are not considered as the most "efficient " ....

Photometrically measured...
( Radiometrically are fine like the rest ..)...

Due to the reason ,that they emit plenty / some of their radiation ,well beyond the 700 nm mark ....

So ,no need to wait for special FR diodes ,that much ...
Yes ,their effects are more 'pronounced ',for sure ....

Still ,the FR 'needs' can be well 'covered' by a number of 'right' WW leds ...
If used properly ..

....

Has anyone tried or thought of using low pressure sodium as sort of a giant yellow led?

Maybe one day I'll try using that for yellow, then use 660nm and 730nm leds to experiment with R:FR ratios while throwing some blue or white LEDs for the CRY gene expressions.

Stardustsailor, thanks for putting that all together.

Two questions:
Page 1 Figure 2AB: More of an academic question. Can you explain the constant slope of the curve between 750 and 1000 nm? Looks strange as it occurs b o t h in the reflectance and transmittance curves and is independent from plant age.

You seem to have some background in plant biology / physiology. Can you comment on what is going on in mj between 600 and 670 nm. During flowering it seems that increasing the amount of red as well as shifting into the deep red is beneficial when going from plant/early to late flowering, especially in the last weeks. That has a flavour of "give me as much energy as possible to get the buds ready". However the shift from red towards deep red indicates that it is not (only) about photosynthesis.

PeterFox said:

Stardustsailor, thanks for putting that all together.

Two questions:
Page 1 Figure 2AB: More of an academic question. Can you explain the constant slope of the curve between 750 and 1000 nm? Looks strange as it occurs b o t h in the reflectance and transmittance curves and is independent from plant age.

You seem to have some background in plant biology / physiology. Can you comment on what is going on in mj between 600 and 670 nm. During flowering it seems that increasing the amount of red as well as shifting into the deep red is beneficial when going from plant/early to late flowering, especially in the last weeks. That has a flavour of "give me as much energy as possible to get the buds ready". However the shift from red towards deep red indicates that it is not (only) about photosynthesis.

Click to expand...

1) Not sure .
But a hard guess will be the lack of photoreceptors at this region (750nm -1μm ) ..
Since there are not any of them (of what we know of ,at least) ,then both reflectance and transmittance curves are ,of course, independent from plant age
and slope of the curves is constant.


2) Yes .Photosynthesis of the photon- rich deep reds plays a(huge? )role .
Plant is aging towards it's end of life cycle.
Growth anabolism has long ceased/faded to null ...
Deep reds ,due to their high absorbance ,and being 'Fuel' for PS I (high Energy photosystem ) really helps towards massive flowering ...

But most important is photomorphogenesis ( mostly it's 'indirect ' effects ... ) ..
Long talk ...Way long talk ..
Tips : Potassium-Water-Osmosis-Nitrates-vacuoles-deep roots

At veg the low reds ( 600-640 nm ) are way 'better' in many aspects from Deep reds ...
Due to their high RQE ? Most probably yes...
And their lower absorbance than deep reds ,means that the plant(s) can sustain longer time,
under high irradiations ... like in long summer days...

While during flowering it is exactly opposite ..
Deep reds 'outperform' the 'ambers/low reds ...

Shorter period of light ,but with higher energy and better absorption ....
Productive Efficiency (RQE) is not as high as Ambers/low reds ,but
anyway the plant and it's leaves ,have long passed the point ('zenith' ) of their highest
efficiency 'age'/state ..Only bud leaves ,remain highly efficient ...
(NIR photography of leaf fluorescence can easily reveal that ... )

During late Spring -early Summer,light power rises ...
Until 21 june (North latitudes )..
The power starts to drop ..
But sunlight spectrum becomes more 'deep red ',generally ..
(Along with more FR ,less UV ,less Blue wls )....
Until mid-late Autumn ...

That happens,more or less ,where and when (good to great ) mj ,is grown outdoors ...

We need a long thread for the 'reds ' ...
Great topic ...
..

churchhaze said:

This is why I think HPS works so well. It has a ton of yellow to feed the lower branches, and far-red to lower %PFr there so it wants to stretch to the "good" light. causing the tree shape.

Look at the slope/gradient in the 640-760nm range. That's probably the slope for red/far-red we want to emulate considering the HPS spectrum seems to work so well.. It looks like there's about twice as much percent of relative energy at 660nm as 730nm so a 2:1 ratio of output power could be good to emulate HPS.

TL;DR: Green, Yellow,orange, and far-red penetrate more and cause %Pfr at lower branches to be lower and thus stretch.

Click to expand...

excellent post....+rep........you may be on to something here!

edit.......has anyone used LPS at all in an indoor grow environment as a primary light source ??............lol............scary;P

A "stellar" post, Sailor! Most of it defies my understanding, but I gleaned some very valuable information. Thanks a lot. I'm a minimally involved hobby grower using 2700 and 5000K household LEDs, a bit of UVB and far red, and the result is the best flavor and high I've ever known in 40 years of smoking (now vaping). Keeping it simple seems to work.