Mars-Hydro LED Grow Light Discussion

[Robert Celt]

OK seems a little early to me, you may find that you are cheating yourself by going by the brown hairs. My THC Bombs all had mostly orange pistils 2 weeks or more before they were actually ready to harvest. Trichomes were only at 50/50 at that point. You may be missing maximum potency by weeks.

 

[flexy123]

One guy from a journal I read grew with ONE "old style" 300W LED for a 2'x2' tent AT 32" (!) distance.
While he certainly might not have had record yields, he did grow successfully from the beginning to the end, including flowering.

Take from that what you will. If someone grows at 32" distance with one lowly 300W LED I am sure that a 600W or 700W at 18" (which obviously is much closer) will give *sufficient* results. Just saying.

 

[Gnarl E Green]

ok. keep your shit for you please ..... this is a community and not the right place for that

My apologies, Sir, I think you're right. Probably time for me to move on. Thanks for your advice.

 

[Robert Celt]

You are right flexy. My own tests on the Mars II 900 I bought for my 3'6x3'6 (approx. 1mx1m) suggested that the optimum distance for that light in that space was between 16 and 26 inches. Closer than 16 inches and you weren't getting the full effect of the light and above 26 inches the intensity dropped off. I was reading a full 30k+ LUX in the 16-26" range

 

[DarkSidofMike]

hmmmm, maybe i will check again with the microscope to be sure then ..... but the result is very nice .... not too high and not too down buz, like it that way

my last check out with the micro was before i was using leds ......... maybe a good idea to check again ty

OK seems a little early to me, you may find that you are cheating yourself by going by the brown hairs. My THC Bombs all had mostly orange pistils 2 weeks or more before they were actually ready to harvest. Trichomes were only at 50/50 at that point. You may be missing maximum potency by weeks.

 

[Robert Celt]

Every strain is different Mike, but that was my experience with the Bomb strains. I could have left them even longer if I wanted the knock out effect but being a non smoker until recently and still a light smoker, usually an hour or so before bed, I wanted something to kill pain but still be able to function. Therefore, I harvested when the trichomes were mostly cloudy with few clear or amber.

 

[DarkSidofMike]

at this distance you better use a more powerfull panel ... you will not have 500 PAR/umol minimum even in the center .... and your plants want 500 and more!

that why i always say to use more powerfull panels ....... or many smallers ...... the light spread is a big problems for leds lights ..... this is a problem for HPS and CFL too, but bigger with leds

You are right flexy. My own tests on the Mars II 900 I bought for my 3'6x3'6 (approx. 1mx1m) suggested that the optimum distance for that light in that space was between 16 and 26 inches. Closer than 16 inches and you weren't getting the full effect of the light and above 26 inches the intensity dropped off. I was reading a full 30k+ LUX in the 16-26" range

 

[DarkSidofMike]

yes for sure

2 seeds from the same strain are differents ..... even 2 clones from the same mother plants are different sometimes lolll

Every strain is different Mike, but that was my experience with the Bomb strains. I could have left them even longer if I wanted the knock out effect but being a non smoker until recently and still a light smoker, usually an hour or so before bed, I wanted something to kill pain but still be able to function. Therefore, I harvested when the trichomes were mostly cloudy with few clear or amber.

 

[Robert Celt]

The thing is Mike, at that range, I get the same or more light intensity as the sun gives me outside. Although that may not be enough for you or some others, it suits me just fine. I am looking at a harvest of 300+ grams, under a light drawing 413 watts, on my first grow ever. I consider that to be quite good considering most experienced and professional growers rarely achieve much more than 1g/w regardless of light type or method of growing

 

[Gnarl E Green]

OK seems a little early to me, you may find that you are cheating yourself by going by the brown hairs. My THC Bombs all had mostly orange pistils 2 weeks or more before they were actually ready to harvest. Trichomes were only at 50/50 at that point. You may be missing maximum potency by weeks.

PM read, but can't reply. Thanks.

 

[Robert Celt]

For me, its the joy of growing for my own meds and for learning (something always at the top of my agenda). I don't really care how long it takes or how much I harvest so long as I get the quality I want. I am not in it to make money, it illegal here in Canada as you well know.
I do it for the joy of seeing my efforts unfold

 

[DarkSidofMike]

this is surely good results, you can be proud for sure ....

but you are clearly not having a "sun intensity" with your setting forget it ...... outside noon max sunlight is 2000 PAR/umol !!! ...... to have that intensity you need your panel to be at 6 inchs!!!! lol

but sun have a lot of useless green .... as we all know

 

[Robert Celt]

Anytime Green

 

[DarkSidofMike]

yeah, maybe number of grams are too important for me ...... maybe

this is illegal in Canada for now ..... NPD will change it lol

 

[Robert Celt]

You are missing the point Mike, 2000 @ noon depends on your latitude and is ONLY at noon. It climbs from very low at sunrise till noon and then drops off to very low at sunset. And that is during the summer. During flowering, mid August to mid October, the daily average is likely closer to 300 when you factor in the days that the sun doesn't shine (overcast/rain etc). My LED on the other hand, gives my girls 12hrs full intensity which is more than I would get on average from the sun.

I may be in my first grow and no where near a plant expert, but I have been a carpenter/engineer for many many years, so when it comes to numbers and physics, I know what I am doing

 

[Robert Celt]

Its been an interesting debate Mike, but its time for me to pack my pipe, take a few hits and join my wife in bed. Have a good one and keep it growing

 

[DarkSidofMike]

yep. agree with almost all of it .... normal/cloudy days specially at fall are really not 2000 this is clear ... 300 seem good


ty .... have a good time

You are missing the point Mike, 2000 @ noon depends on your latitude and is ONLY at noon. It climbs from very low at sunrise till noon and then drops off to very low at sunset. And that is during the summer. During flowering, mid August to mid October, the daily average is likely closer to 300 when you factor in the days that the sun doesn't shine (overcast/rain etc). My LED on the other hand, gives my girls 12hrs full intensity which is more than I would get on average from the sun.

I may be in my first grow and no where near a plant expert, but I have been a carpenter/engineer for many many years, so when it comes to numbers and physics, I know what I am doing

 

[ganjazz]

New baby's 2nd grow ,10 different strains, 6 auto's on the right, in 1-2 weeks go under led.(now TCL)

Started with LST with some plants to keep low, auto's topping is not advised, only LST and defol with those.
Non auto's probably gonna top all 4 soon for scrog and do LST, defol.

2nd bit (early)partial harvest under mars2-reflector (small-medium nugs)
Hope max one more week for big cut.

 

[Icemud]

but sun have a lot of useless green .... as we all know

Hey Mike,

Want to correct you here....

Plants use green light...actually Green is absorbed at roughly 79% where as red and blue are absorbed between 90-100%. All PAR wavelengths (between 380nm and 780nm) although PAR typically refers to 400nm-700... are used for photosynthesis, just some more efficiently than others.

Green wavelengths actually drive photosynthesis harder than red or blue light in high intensity white light.. this is because green light reflects easier than other colors, therefore it will penetrate deeper into the leaf layers and mesophyll hitting the lower chloroplasts that red and blue do not hit.

You seem like a really helpful guy that wants to know more about lighting DarksideofMike, so please take this as enlightenment. Being helpful is a great thing but when you are sharing information which isn't correct, it doesn't really help people at all. So please take this as just me being helpful.

PS...sorry this quote is formatted very weird, copying and pasting PDF files doesn't work well for some reason and makes it hard to follow.


Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic
Question of Why Leaves are Green Ichiro Terashima Takashi Fujita Takeshi Inoue Wah Soon Chow and Riichi Oguchi
*full article is about 15 pages long, so here are some quotes from it...

Absorbance spectra of chlorophylls or pigments extracted from green leaves show that green light is absorbed only
weakly. Action spectra of photosynthesis for thin algal solutions, transparent thalli of ordinary green algae, and leaves of
aquatic angiosperms also show that green light is less effective than red light. As has been pointed out by Nishio (2000) ,
these facts are often confused, and it is frequently argued that green light is inefficient for photosynthesis in green
leaves. However, many spectra of absorptance (the absolute value of light absorption) measured with integrating spheres
have shown clearly that ordinary, green leaves of land plants absorb a substantial fraction of green light ( McCree 1972 ,
Inada 1976 , Gates 1980 ). It is also known that green light, once absorbed by the leaves, drives photosynthesis with high efficiency ( Björkmann 1968 , Balegh and Biddulph 1970 , McCree 1972 , Inada 1976 ). On an absorbed quantum basis,
the effi ciency or photosynthetic quantum yield of green light is comparable with that of red light, and greater than
that of blue light. The difference between the quantum yields of green and blue light is particularly large in woody
plants grown outdoors in high light. The question of how much green light is absorbed and used in photosynthesis by
the green leaves of land plants has therefore been solved. In this mini-review, however, we aim at further clarifying
another important role of green light in photosynthesis, by considering the intra-leaf profiles of light absorption
and photosynthetic capacity of chloroplasts. First, we briefly explain light absorption by the leaf. Secondly, we
examine the light environment within the leaf. Thirdly, we compare the vertical, intra-leaf profile of photosynthetic
capacity with that of light absorption. We also discuss some serious problems with the use of pulse amplitude
modulated (PAM) fluorometry in assessing leaf electron transport rate and photoinhibition. Fourthly, we propose a
new method to measure the quantum yield of any mono-chromatic light in white light, and demonstrate the effec-
tiveness of green light in strong white light. Based on these arguments, we fi nally revisit the enigmatic question of why
leaves are green.

As an optical system, the leaf differs from a pigment solution in two aspects: the concentration of pigments into
chloroplasts and the diffusive nature of plant tissues. The first factor decreases the opportunity for light to encounter
pigments and generally decreases light absorption, and has been called the sieve or flattening effect. Once light that is strongly absorbed by chlorophylls, such as blue or red, encounters a chloroplast, most of the light is absorbed. Let us make the drastic assumption that the chloroplast is a sac containing a solution of chlorophylls at a concentration of 100 mol m–3
. This value is chosen because (i) ordinary green leaves are a few hundred micrometers thick; (ii) 50–80% of their volume comprises cells; and (iii) chloroplasts occupy 5–10% of the cell volume. Given that the values of ε for the mixture of chlorophylls at blue and red wavelengths are > 1.0×10 4 m 2 mol –1 , and the chloroplast thickness is 2μ m, then A of the chloroplast calculated
using Equation 1 is > 2. In other words, < 1% of the red or blue light is transmitted through the chloroplast. On the
other hand, for wavelengths that are weakly absorbed, such as green light, T is considerable. When ε for green light is
assumed to be 500 m 2mol –1 ,A and T would be 0.05 and 79.4%, respectively. Using a simple model shown in
Fig. 1, let us consider how the sieve effect is influenced by wavelength. In the left-hand cuvette, photosynthetic pigments are uniformly distributed, whereas the right-hand model comprises one half-cuvette with the pigments concentrated 2-fold and another half-
cuvette containing only the solvent. At wavelengths with strong absorption, the loss of absorptance by the sieve effect
is large. On the other hand, at wavelengths of weak absorption such as green, the loss is marginal. The sieve effect,
therefore, strongly decreases absorptance at wavelengths of strong absorption such as red and blue light. Because of this,
absorption spectra with strong sieve effects show flattened absorption peaks; hence the alternative term ‘flattening effect’.

The second point that distinguishes leaves from a simple pigment solution is that leaf tissues are diffusive. This is due
to the fact that the leaf consists of cells and intercellular air spaces. The refractive index, which depends on both the
material and wavelength of the light, of the bulk plant cells is around 1.48, compared with 1.33 for water and 1.0 for air.
The diffusive nature of leaf tissues increases the light path length (détour effect) and thereby the opportunity for light
to encounter chloroplasts, leading to the increase in absorptance ( Vogelmann 1993 ). On the other hand, the diffusive
nature of the leaf tissues inevitably increases the reflectance, R , of the leaf to some extent. Leaves appear to minimize
R of the adaxial side by having a greater contact area between the adaxial epidermis and palisade tissue cells per unit leaf
surface area than that between the abaxial epidermis and spongy tissue cells. In some species, palisade tissue cells are
funnel-shaped, which further increases the contact area with the epidermis ( Haberlandt 1914 ). By reducing the chances of
refraction at the interfaces between cells and air, R decreases to a considerable extent (compare the differences in R
between the adaxial and abaxial sides).

The increase in absorptance due to light diffusion (détour effect) is signifi cant in the spongy tissues in bifacial leaves
whose abaxial surfaces are paler than their adaxial surfaces ( Terashima and Saeki 1983 , Vogelmann 1993 ). In such leaves,
spongy tissues have cell surfaces facing various directions and fewer chloroplasts (or chlorophyll) per unit mesophyll
volume. In leaves of Camellia japonica, a typical example, lengthening of the optical path is more marked in the spongy
tissue than in the palisade tissue ( Terashima and Saeki 1983 ). On the other hand, in spinach, where the difference in the
chlorophyll content per unit mesophyll volume between the palisade and spongy tissues use is small, the optical path
length does not differ much between the tissues ( Vogelmann and Evans 2002 ). The consequence of lengthening the optical path can be shown using the same model ( Fig. 2 ). In this model, the path length increases by 3-fold (see Vogelmann 1993 ). At strongly
absorbed wavelengths, the increase in absorptance achieved by lengthening the light path is 11% (while the increase in
A is, of course, 3-fold). In contrast, for weakly absorbed wave-lengths such as green light, the increase in absorptance is
much greater. In summary, for strongly absorbed light such as red or blue, the sieve effect decreases absorptance considerably,
whereas the détour effect increases absorptance marginally. On the other hand, for green light, loss in the efficiency of
absorptance by the sieve effect is small, while gain in absorp-tance by the détour effect is large. Consequently, green
leaves absorb much green light. Typical values of absorp-tance at 550 nm range from 50% in Lactuca sativa (lettuce)
to 90% in evergreen broad-leaved trees ( Inada 1976 ). The corresponding absorptance values for blue and red lights
range from 80 to 95%. Moreover, as already mentioned above, it has been clearly shown that the quantum yield of
photosynthesis based on absorbed photosynthetically active photon flux density (PPFD), measured at low PPFDs, was
comparable between green and red light. When measured in leaves grown under natural conditions, particularly for those
of trees, the quantum yield of green light is considerably greater than that of blue light ( Inada 1976 ), because some
fraction of blue light is absorbed by flavonoids in vacuoles and/or carotenoids in chloroplast envelopes. Moreover,
some carotenoids in thylakoid membranes do not transfer energy to reaction centers, or transfer with an effi ciency sig-
nifi cantly less than 1.0 ( Akimoto and Mimuro 2005 ). For example, one of the most abundant carotenoids in thyla-
koids, lutein, transfers its energy to chlorophyll with an effi-ciency of 0.7 ( Akimoto et al. 2005 ). The effi ciency for
neoxanthin is even less, at most 0.09 (Akimoto et al. 2005 ). Accumulation of flavonoids and carotenoids is well known
to increase in response to ultraviolet and/or strong light ( Lambers et al. 2008 ). This probably explains to a considerable
extent why the quantum yield of blue light is low. Evans and Anderson (1987) reconstructed the absorbance spectrum of thylakoid membranes from those of the chlorophyll–protein complexes and estimated the relative excitation of PSII and PSI. Evans (1987) argued that imbalance of PSII/PSI excitation would occur at wavelengths where light is absorbed by Chl b because energy is preferentially transferred to PSII. This might also explain why the quantum yield of blue light on an absorbed quantum basis is low. If this effect is large, a decrease in the PSII quantum yield (Genty's parameter, see below) might be expected at wavelengths strongly absorbed by Chl
b . In a preliminary study with rice leaf discs illuminated with monochoromatic lights at a low PPFD of 5–12 μ mol m –2 s –1

Although the light absorption profi les calculated by Nishio (2000) are spurious ( Vogelmann and Evans 2002 ), his
argument has nevertheless been proven experimentally to be correct using our differential quantum yield method.
Namely, red light is more effective than green light in white light at low PPFDs, but as PPFD increases, light energy
absorbed by the uppermost chloroplasts tends to be dissipated as heat, while penetrating green light increases photo-
synthesis by exciting chloroplasts located deep in the mesophyll. Thus, for leaves, it could be adaptive to use chlo-
rophylls as photosynthetic pigments, because, by having chlorophyll with a ‘green window’ the leaves are able to
maintain high quantum yields for the whole leaf in both weak and strong light conditions.

 

[ruddie]

Ed Rosenthal would disagree with regards to the 550n wavelength. Also I always thought if in this case the object is green it means it's reflecting more green then anything else, that's why it's green. It even appears this massive expert in growing indicates you could in theory walk into a flowering dark room with a green light and not disturb them. Am I reading this right?

text below from ed rosenthals site Ed Rosenthal's Marijuana Grower's Handbook

GREEN AND BLUE LIGHT AT NIGHT

As plants evolved for hundreds of millions of years they never actually had to deal with separation of light spectrums or unusual lighting regimes. When they received light it came from the sun in a mixture of spectrums and they could pick and choose which to use. It was only with the advent first of gas and then electric lighting that plants encountered unusual regimens and splintered spectrums.

Plants measure day length using the red light spectrum. While they use other spectrums for other purposes, they are not sensitive to them as far as flowering is concerned. They are almost totally insensitive to green light and for this reason reflect it back to us while absorbing most other spectrums.

Plants’ insensitivity to green light can be used to a gardener’s advantage. You know that turning the light on in the middle of the dark cycle disturbs the plants’ flowering paradigm. The light, HPS, fluorescent and MH lamps all emit red light. Green fluorescent and LED lights contain no red light and will not disturb the dark period. You can go in the garden under adequate light to work, as long as it is green.

Plants use blue light for certain regulatory processes and also for photosynthesis. Chlorophyll absorbs both blue and red light and uses the light’s energy to power the complex process in which water and atmospheric carbon dioxide are converted to sugar and oxygen gas. Blue light does not affect the regulation of flowering.

When blue light is turned on during the dark period, plants photosynthesize but their flowering isn’t affected. This results in more growth as the plants produce more sugars. Before LED lights it was difficult to create a pure blue light. Instead, most of the time other spectrums were filtered out, which can be an inconvenient process. Try using between 20 and 40 watts of mixed blue light per 1000 watts of regular light. I have done only initial experimentation with this so test this in a limited way first. I suspect that the additional light is an efficient way of increasing total yield

Aside from red and blue light, plants also use orange light for photosynthesis. I haven’t experimented with them yet, but orange LEDs might also help increase yield and probably can be lit continuously, just like the blues. More on this as the news breaks—or at least, as it fractures.