Hypothesis about plant-Rhizosphere signals and light color in flowering

I have an idea forming and I wanted to run it by you. Hopefully some experts will have time to chime in.

In my last harvest, I had gone completely organic and had extreme delays in flowering, though I was not adding any nitrogen they still looked more green than they should have by that time. The lighting was 75% daylight tubes and 25% warm white tubes(3000K).

It is my understanding that between the plant and the rhizosphere, there are signals exchanged chemically and electrically. These signals help the soil biology enable the plant to maximize it's potential and in turn bring that energy from the sun down into their world. In organic growing this means you can have all the major nutrients and micro nutrients in the soil sequestered until needed. Something must trigger the changes in the plant to adjust the signals it gives the rhizosphere. Obviously 12/12 lighting makes some differences, but I am guessing that the color of the light may factor into it a lot. Chemical growers might not see this as much due to how they force feed the plant foods with low nitrogen.

To test this I am putting a 250W HPS above my plants in addition to the fluoro tubes I am using vertically. After a day of this I can already smell changes. Is this the microbiology adjusting?

Has anyone else experienced too much nitrogen uptake under blue light?

Can't say since I can't see the soil but the thing that comes to mind is soil temps.

I like mine on the cold side.. How have yours been? Do they sit on cement and stay cool?

Just chatting not critiquing..

It's cool man, the whole point is to get to the truth. It's just a theory. It would explain a lot to me though. Temps in the soil are pretty good normally here. Not sitting on concrete, but they are right by the fresh air intakes so it cools them on the way up.

I think that by adding light, you increased production of all the oils and such that smell.

just like tomatoes taste best after a string of sunny days. and shade grown basil has no flavor.

might I also point out, oregano grown in rich soil is also flavorless.

I was already at 250W per square foot..... gonna technically be less per square foot in the new cab, but not by a lot. Just a more diverse spectrum and a bit more area of coverage.

hmmmm...Interesting theory. I've only used hps so have no practical basis. For Indica (which is triggered by photoperiod) what is the color spectrum change when the Earth shifts? I'm betting more red.

The light issue is something I haven't considered.. The green is a result of reflected light.. So your "shade of green" must be a function of reflection with the light you are using, on the strain you are growing and it's state of biology.. Phew that was a long sentence..


Let's see ( dopler effect ) moving towards us is faster ( shorter ) so it's blue shift ( higher energy ) and moving away is slower ( longer ) and Red ( lower energy)..

I don't know.. Honestly I don't see it myself.. Some leaves are lighter green. They also change during their lives; I've seen them change to darker, lighter or even yellow.. Without manipulating nutrients in any great way.

I am okay with 250 MH bulbs.. They work fine for veg and I read they improve flowering quality in a mixed spectrum.. That one I am testing out this season.

As with any artificial system all the elements must work together.. Air, nutrients , light, water , tem

Their is something to your blue light. I posted this on another thread that is worth glancing over if you have the time.

http://www.icmag.com/ic/showthread.php?p=2584331#post2584331



Light Or Fight? How Plants Make Tough Survival Choices

ScienceDaily (Mar. 2, 2009) — Ever since insects developed a taste for vegetation, plants have faced the same dilemma: use limited resources to out-compete their neighbors for light to grow, or, invest directly in defense against hungry insects.

Now, an international team of scientists at the Salk Institute for Biological Studies and the Institute of Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agronomía (IFEVA) has discovered how plants weigh the tradeoffs and redirect their energies accordingly.

The same light sensor that detects other plants crowding in and gives the signal to switch on the synthesis of the plant growth hormone auxin reduces the plant's responsiveness to the hormone jasmonic acid, which orchestrates the synthesis of a whole array of defensive chemicals, the researchers report in an article published in the current early online edition of the Proceedings of the National Academy of Sciences.

"Understanding how plants resolve the dilemma of resource allocation on a mechanistic level opens the possibility to increase the natural defenses of crops, especially in the high density plantings typical of modern agriculture, which depend on regular applications of insecticides," explains senior author Carlos L. Ballaré, Ph.D., a senior scientist with CONICET (the National Research Council of Argentina) and associate professor at the University of Buenos Aires.

In an earlier study, Ballaré discovered that plants dial down their investment in defense when they perceive an increased risk of competition for light. But just how changes in light quality caused plants to drop their guards were still poorly understood. To connect the two, he turned to Howard Hughes Medical Institute investigator Joanne Chory, Ph.D., in the Plant Biology Laboratory at the Salk Institute and former lab member, Yi Tao, Ph.D., who had dissected the molecular pathway that plants use to adjust their growth and flowering time to shade.

Plants sense the presence of other plants in their neighborhood by the relative increase in incoming far-red light resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants. "When the major photoreceptor for shade avoidance detects neighbors, plants start producing the growth hormone auxin and transport it to their stems, where it helps plants grow taller," explains Chory.

But plants also react to chemical cues in the oral secretions of herbivores and mechanical damage caused by caterpillars and their ilk nibbling on foliage. They increase the production of defense-related hormones, particularly jasmonic acid, which ramps up the concentration of chemicals that make plants unpalatable or at least less nutritious for herbivores.

"Such responses incur what is known as opportunity costs," says Chory. "Resource allocation to competition can limit investment in defense, increasing vulnerability to herbivores, while allocation to defense can reduce competitive ability against neighboring plants."

And that's exactly what first author Javier E. Moreno, a graduate student in Ballaré´s lab, found. Fall armyworms—caterpillars that prefer to chomp on corn, sorghum and other members of the grass family but won't say no to beans, potatoes, peanuts, cotton and other crops—grew twice as fast on Arabidopsis thaliana seedling grown under crowded conditions or exposed to far-red radiation, the light signal plants use to detect the proximity of neighbors. Like many commercially grown crops, Arabidopsis — the lab rat of plant biologists — doesn't tolerate shade well.

But it was more than a matter of limited resources. Mutated Arabidopsis seedlings that no longer responded to far-red radiation but had normal levels of the far-red photoreceptor, still let their defenses down. At closer inspection, the researchers found that far-red radiation decreased the plants' sensitivity to jasmonates. By ignoring jasmonate signals, the plants save resources because they no long invest in defense and, at the same time, avoid the growth-inhibitory effects of jasmonates.

"Without sufficient light to keep photosynthesis going, plants won't have enough energy to invest in sophisticated defense strategies," says Ballaré. "Coupling shade avoidance syndrome with the regulation of resource allocation to defense could provide a major selective advantage for plants growing in the wild, but might increase the vulnerability of densely planted crops to insects."

http://www.sciencedaily.com/releases...0227161823.htm


From what i gathered far red light has an effect of slowing down jasomic production which would be used to trigger a plants defenses. In the case of Cannabis it would diminish Trichome production. BOG has stated he uses diminished light level towards the end of his grows for potency. This can be seen as lowering the levels in the far red light allows the plants mechanisms for defense to function again.


This coupled with the stress from not watering would ramp up the Jasmonic levels and in turn increase Trichome production. All this information can be used in the growers favor, timing would be really key because Jasmonic also slows and or stops growth and would not be as effective i guess if started at the wrong time. also a shift in light spectrum towards the end flowering in favor of less far red would probably help, but only experimentation will tell.


Hope this helped furthered the discussion on this topic

Interesting topic konstantgrdnr, thanks for posting it. Not sure I understand though, because it seems both to suggest far red light is beneficial, but then also maybe is useful too. Knowing it's relationship to cannabis specifically would be nice though. I think the plants do need the blue, but mine seemed to really lack the red. I'm just adding more red, not taking away any blue.

Jack, my shoplights with the daylight tubes have a 98CRI rating, so I'm definitely not being deceived by the lighting. Whatever light they are under, they look like they have more chlorophyll in them, and more leaf than they should late in flower, and they take longer. Nitrogen seems to be a significant part of what the soil biology is feeding the plant. My concern is that the blue light, and perhaps lack of far red is confusing the plant hormonally, and so the soil still thinks it's supposed to deliver a vegetative diet. I'm wondering if the plant "tells" the soil biology to change when the light starts to get more red in the later parts of the year. It would seem logical that if plants are sensitive to the spectral changes, the soil biology would adapt relative to it. I'm just not sure how to scientifically experiment on this subject.

okay so why dont people use metal halides through the whole grow for potency?
ive read conflicting opinions about metal halide potency effects i think ed rosethal says mh makes more potent pot

nibirubian said:

okay so why dont people use metal halides through the whole grow for potency?
ive read conflicting opinions about metal halide potency effects i think ed rosethal says mh makes more potent pot

Click to expand...

Because HPS lights add more weight......

My flowers were always frostier & had more flavor under a MH flowering but the HPS adds alot more weight imho!

The roots provide sugars I believe..

The issues of nitrogen availability have to do with the biology in the soil doesn't it?

My plants have always been green. One went "gold" on me once.

So is this about the folklore of the plant must have all it's leaves dieing when the bud finishes? Like it must have spent all it's reserves exactly to the day we harvest?
So far with Indica mixes I see there are buds that are ready to cut and then usually there is a second layer of buds that go a while longer. That's a possible style with a green plant.. Two harvests or three..

I've seen light green plants.. usually mixes that favor Sativa when 95% favor Indica.

That's my take..

I have been using the new light for a while now, and I have to say the results are stunning. The bud formations stopped growing leaf and began focusing more on the flowers. Also, the dark green they were experiencing has reduced a great deal, and some are even beginning to show a more natural yellowing.

The next generation, 4 North #1 plants, and 2 C99 X DC are already showing better results than the previous generation which was started under much more blue light. While this is not conclusive evidence of my hypothesis, I do think it does at least give it some weight. I will continue to monitor this. I know my soil mix has not changed a bit.

There was quite a bit of discussion in the Ceramic Metal Halide thread about red vs. blue light which led me to go with a mixed spectrum grow. I have 2 400W CMH and a 600W HPS in my flowering chamber and manipulate where my plants are placed (which regulates what kind of light they are getting) depending on how far into flowering they are.

I have the CMH's on the outside of the HPS which is located in the the middle.... This allows me to place newly flowering plants at the edge getting mostly CMH light (but some HPS bleed) which helps reduce stretch! After the stretch period when pistils are forming at a decent rate I reposition the plants in the middle, directly under the HPS (with a little CMH bleed from both sides) until the plants are getting ready to be flushed. I move the finishing plants back to the edge (under the CMH) until I harvest. That's how I run my perpetual using mixed spectrum and I am enjoying my results.

i think your 250w is drying out the air more an lowering the RH and thus being able to smell more.

magiccannabus said:

I have been using the new light for a while now, and I have to say the results are stunning. The bud formations stopped growing leaf and began focusing more on the flowers. Also, the dark green they were experiencing has reduced a great deal, and some are even beginning to show a more natural yellowing.

The next generation, 4 North #1 plants, and 2 C99 X DC are already showing better results than the previous generation which was started under much more blue light. While this is not conclusive evidence of my hypothesis, I do think it does at least give it some weight. I will continue to monitor this. I know my soil mix has not changed a bit.

Click to expand...

Perhaps not hypothesis-proved, but your results are conclusive. It may indeed be saying something about color temperature (red vs blue) and flower timing, but I think it says more about overall light quality for a given stage of growth.

I'm with you on color temp shift in flower to trigger strong hormone changes. You will not find a bigger believer than me in the significance of the cannabis root/fungal mycelium network bond in organic nutrient delivery. Ask me and I'll straight tell you that if you're trying to grow organic and want to be aggressive (as in, yield well), you need assistance from beneficial fungus and bacteria.

I've been a floro grower for a while now. (I cheat though, use an old over-driven T12 setup that was built for me ages ago) I love General Electric 'daylight' T8s and T12s; they come in 5000K and 6500K color temp flavors. These bastards are great for veg, they make a deep, dark, green chlorination that is great for short, bushy foliage and big, heavy fan leaves. It makes for very "rooty" plants that store shitloads of starches.



Upon going to 12/12 I like to switch to General Electric Plant & Aquariums. They're basically a GE chroma 50 but with an added phosphor coating that slowly burns away. This adds tons of 'red' to the spectrum and they are wonderful for budding. You can easily see the color temp shift from my veg bulbs (left) and my flower tubes (right).

Which brings us to the issue of trying to measure/compare floros. See, the problem is the popular metrics, they are a bit meaningless in light of our true needs as gardeners.

magiccannabus said:

Jack, my shoplights with the daylight tubes have a 98CRI rating, so I'm definitely not being deceived by the lighting.....

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As I said, the daylights are great, but let's take that measurement you have there into account. 98 CRI

Color Rendering Index is a measurement of light 'quality' on the basis of the light spectrum perceived by the human eye. 100 CRI is supposedly 'perfect' color rendering. True sunlight is the golden standard here.

The problem with judging a lamp by CRI for the purposes of gardening lies right in what it was meant for: making light good for humans to see by. Plants on the other hand have different priorities.

Lumens have a similar issue. That's why if you go and look at one of the GE Plant & Aquarium 48 inch T12 tubes that I absolutely love you will find that it coughs up a frankly pathetic 1900 lumens.

However, by PAR, a more plant-oriented measure of the light spectrum, these tubes do very well. With the penetration benefits of overdriving and foil tape reflectors they are a true growing force for bud. Sortof. If you're willing to put in the effort to suit your cab to take advantage of their weird shape.

Had a look at your grow setup by the way. Full 360 degree vertical coverage must be insanely good for making bud locations! But it looks like you have found it has limitations when it comes to 'budswell' You can apply as large a quantity of light as you want into a space. (which you have done 45,000 lumens, 512 watts in 15 cubic feet!? Good god man) It will not necessarily preform well for producing the ganjas unless it is of sufficient quality.

Two aspects define this quality. One, which you yourself highly suspected, is color temperature. More accurately, the specific wavelengths of electromagnetic radiation being applied to your plants. For flower, you just have to have the red. Maintaining plenty of blue is fine. That will keep internode gaps tight and bud coverage high. But you've got to get the red in there.

HPS does this well, as you've found, but what it also does is penetrate. Light penetration is a bit hard to define, but it is very different than lumens or quantity of light. Floros can make an epic quantity of light, many many active photons, but they lack utterly in this penetration and therefore need to be right on top of the plants in order to work for bud. And even then the nature of cheap locally-acquired floros means getting your color temps right for a given stage of growth can be a headache.

So you went HID. You have found, already, marked improvement in budding. The red color temp went to work immediately to send your plants into bud. The penetration will come into play later, as the buds start to wad up and put on weight. The difference between fat and skinny buds is a good penetration rate from your light. In order to convince the plants to continue to put on bud, long after they've developed enough flowers to fulfill their evolutionary imperative, this quality is needed in quantity!

I think use of hybrid tech is the real way to go. Keep your super-blue 6500K vertical crazy box. Veg plants like Mad in the thing. Then, when they are 1/3-1/2 the total height you can manage, hang a moderate (150-250w) HPS over the center 'hole' as you have done. Perhaps shut off a couple of your side-lights and mebbe even switch out some of those super-blue daylight tubes for some much redder jobbies like the P&As.

Your internodes would be awesome! Buds would be fat! And there would be hundreds of them! Low side colas could be of pretty decent quality if you trained them close to the redder floro side-lighting. And then you would have mega-crazy red-side-lit-and-HPS-top-lit-super-dense head colas to crown your 360-degree vertical grow. Your space lends itself to a nice tight group of taller, narrower plants anyway, should work out quite nice. That seems to be the way that you are naturally heading anyhow, finding your optimum use of space for getting some fatter buds!

My new cabinet has a bigger floor space, approximately 6 square feet. I haven't rigged up all the side lights, but the 250 overhead is indeed adding to fatness and potency. I love how the fluoro light fills the space and allows for such a lush plant top to bottom. It eliminates shadows and I don't have to worry so much about the lower parts being shaded. Genetically they definitely favor the tops though, so that HPS really helps them along. I will eventually put more red tubes in the side lights though. I definitely want some blue, but I like the way they've been reacting to the red light.

I really want to do a proper test of this theory though. Maybe someone can help me figure out a way to conduct such a test scientifically.

Anyway, here's a pic of my new cabinet. It's a bit older though so there's more plants in there now. I will be putting more shop lights in too. I only have 256W of them, one fixture in each corner.

smokesalot420 said:

There was quite a bit of discussion in the Ceramic Metal Halide thread about red vs. blue light which led me to go with a mixed spectrum grow. I have 2 400W CMH and a 600W HPS in my flowering chamber and manipulate where my plants are placed (which regulates what kind of light they are getting) depending on how far into flowering they are.

I have the CMH's on the outside of the HPS which is located in the the middle.... This allows me to place newly flowering plants at the edge getting mostly CMH light (but some HPS bleed) which helps reduce stretch! After the stretch period when pistils are forming at a decent rate I reposition the plants in the middle, directly under the HPS (with a little CMH bleed from both sides) until the plants are getting ready to be flushed. I move the finishing plants back to the edge (under the CMH) until I harvest. That's how I run my perpetual using mixed spectrum and I am enjoying my results.

Click to expand...

Great response. Good to hear from someone with experience, and it's fun to see how our results have had some things in common. My grow has T8 tubes along the edges, and an HPS in the middle, but stretch basically no longer happens, at all.... and the older plants around the middle are covered in frost. It's also giving me the added benefit of better lower and middle buds. I think our grow spaces are fairly different overall though, both in size and detail.

Ok, guess I'll trot out my two cents. I did the HPS vs MH experiment back in the mid 70's. Matter of fact, it was the first thing I tried when I got the second (HPS) bulb. Identical clones under seperate 1k fixtures, one HPS the other MH. Differences? None that I could tell. Identical quality, identical yield. Certainly, genetic differences overrule light spectrum when it comes to potency and yield. The more you grow, the more you shift your attention from nurture to nature.