Control red to far-red light ratio to limit stretching

[Scrogerman]

You the man Spurr, Tagged! another quality thread k+

 

[spurr]

Here is a great read in the newest edition of Plant Physiology online companion (5th ed):

"Know Thy Neighbor through Phytochrome"
C. L. Ballaré, A. Scopel, J. J. Casal and R. A. Sánchez, IFEVA,
Facultad de Agronomía, Universidad de Buenos Aires and CONICET.
http://5e.plantphys.net/article.php?ch=e&id=236

 

[Dave Coulier]

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[spurr]

p.s. also while we are talking far red i heard somewhere that far-red increases resin production - any comments on that ??

So far, I have not found much, but I did find one neat study, uploaded in this post

"EFFECT OF LIGHT QUALITY ON CANNABINOID CONTENT OF CANNABIS SATIVA L. (CANNABACEAE)"
PAUL G. MAHLBERG AND JOHN K. HEMPHILL
BOT. GAZ. 144(1):43-48. 1983

​

Plants of a drug strain of Cannabis sativa L.-grown 33 days under daylight, shaded daylight conditions, filtered green, blue, and red light, and darkness-were analyzed by gas-liquid chromatography for their cannabinoid content.

The highest content of cannabinoids, predominantly 9-tetrahydrocannabinol (9-THC) in this strain, occurred in the youngest leaves of daylight-grown plants. Leaves at successively lower nodes of this control condition and all treated plants subsequently grown in daylight contained progressively lower levels of cannabinoids.

Leaves from plants grown under filtered green light and darkness contained significantly lower levels of 9-THC than those from plants grown in daylight. However, the 9-THC content of leaves from plants grown under shaded daylight and filtered red and blue light did not differ significantly from the 9-THC content in daylight controls, indicating that these conditions did not alter the synthetic rate of this cannabinoid.

The cannabichromene (CBC) content of plants grown under filtered red and green light and darkness differed from the CBC content in plants grown in daylight, indicating that theformation of this cannabinoid was independent of 9-THC. Leaves from plants grown under filtered red and green light and darkness recovered the capacity to synthesize typical levels of 9-THC and CBC when placed under daylight conditions. Plants from all light and dark treatments, when subsequently placed under daylight conditions for 66 days, attained levels of cannabinoid synthesis comparable to the daylight controls

 

[Dave Coulier]

it has been speculated on other forums ambient temperature fluctuations during the day/night cycles contributes significantly to stretching during the onset of flowering.

several mods on serious seeds forums relate similar validations regarding this.

researching different light studies for my upcoming mh/hps comparison has revealed a reoccuring theme on how regardless of using a mh/hps for flowering, the stretch was the same given for each strain used.

I mean to respond to this sooner, but forgot.

Do you have sources for your statement? I ask because I have seen beautiful short compact plants under 6500k T5's become very leggy when they started to shade each other. Excessive temperatures will also counteract the effects blue light has on internodal elongation.

If plants were spaced out, and temperatures were ideal, I would expect there would a noticeable difference between HPS and MH effects on controlling the stretch.

 

[imadoofus]

sources, you ask for? of course not! what kinda troll would i be if i did?

lol...

all completely heresay, but nonetheless, reoccuring heresay; perhaps, it has merit ; )

 

[Dave Coulier]

sources, you ask for? of course not! what kinda troll would i be if i did?

lol...

all completely heresay, but nonetheless, reoccuring heresay; perhaps, it has merit ; )

There is no need to act that way. I was offering you reasons why what you have heard may not be 100% true. Plenty of the grows you'll see on this forum have plants that are badly over-crowded, and that will trigger SAS(Shade Avoidance Syndrome), and no matter how much blue light you supply your plants with, I guarantee that they will stretch.

Read this if you want to educate yourself and stop relying on hearsay. Its a great read posted by Verdant Green.

 

[VerdantGreen]

So far, I have not found much, but I did find one neat study, uploaded in this post

"EFFECT OF LIGHT QUALITY ON CANNABINOID CONTENT OF CANNABIS SATIVA L. (CANNABACEAE)"
PAUL G. MAHLBERG AND JOHN K. HEMPHILL
BOT. GAZ. 144(1):43-48. 1983

​

cool, thanks, the paper seems to find that 'regular' spectrum doesnt unduly effect THC content. i dont think the phlexiglass would have blocked far red light.

 

[VerdantGreen]

Here is a great read in the newest edition of Plant Physiology online companion (5th ed):

"Know Thy Neighbor through Phytochrome"
C. L. Ballaré, A. Scopel, J. J. Casal and R. A. Sánchez, IFEVA,
Facultad de Agronomía, Universidad de Buenos Aires and CONICET.
http://5e.plantphys.net/article.php?ch=e&id=236

this is also a nice short but informative read. i have a few Deep Chunk plants atm and as soon as they started running out of space the increase in stretch is huge!

 

[IMO]

not really sure about the rules on this forum but if anyone is bugged by this by all means remove it... as many other members, i am on many forums. while doing my own research into lighting i came across this grow i found this grower to be quite knowledgeable and worth looking into what he is doing. I think a lot of the leg work you guys are talking about has been done by him in some capacity. i encourage you to take a look.

here's the journal to match that build

 

[Hash Zeppelin]

MH sucks in general. I still think it is best just to use hps, and it you are having to much stretch than you need to learn how to super crop. this is coming from experience.

 

[spurr]

MH sucks in general. I still think it is best just to use hps, and it you are having to much stretch than you need to learn how to super crop. this is coming from experience.

While I agree most MH lamps are not ideal for highest yield/growth, due to lower PPFD, MH does not suck in general. There are benefits to the blue light from MH in terms of blue light mediated photoresponses of plants (e.g. increased stomatal conductance, phototropism, etc).

PPFD from new horticultural specific MH and HPS lamps, if the same level (should be high, above 800 PPFD), provides pretty comparable rates of photosynthesis. There is a myth in the cannabis world that red light drives rate of photosynthesis much better than blue or green light.

I for one use an enhanced HPS with 'extra' blue and green, ex. I have used Hotrilux Super HPS and Oshio OptiRed. But I plan to test the Hortilux Blue 1,000w because it should be able to provide high PPFD, esp. if on a light mover and closer to canopy, while also providing lots of green light, and sufficient blue light and red light.

This thread isn't about controlling stretch via. topping, LST, super-cropping, etc. Those methods do not control stretch per say, they merely re-direct the stretch into more tops, and thus slows down the growth rate, so it seems like to controls stretch (but really doesn't). Those tops still stretch the same as a plant that has not been trained/topped/etc, if the red:far-red ratio is much below 1:1 intracaonpy. That is coming from many years of experience, and also a solid understanding of the issues involved.

If you put two plants in the same room, one that was topped/trained/super-cropped a few days prior and one that has not been topped/etc., with the same red:far-red ratio intracanopy, both plants will stretch the same (everything else being equal). In fact, by topping/super-cropping/etc., you are reducing the red:far-red ratio (due to more shading of red light from increased canopy size/density) and the topped/trained/super-cropped plant will stretch more...

The two main natural factors that make a plant stretch the most (assuming the plants are getting sufficient levels of nutrients, PPFD, etc.) are red:far-red ratio intraconpy (due to phtyochrome issues) and DIF (due to GA3 buildup issues).

 

[gloryoskie]

Wow, this just blows me away. I am very pleased to have stumbled across this thread. Thank you so much! I will adopt my grows to minimize stretch substituting the lighting/temps control vs the pinching and brute force techniques I've previously employed.

Wow.

 

[Dave Coulier]

Gloryoskie, if you try to follow the steps outlined by Spurr you can get some incredible compact plants even on 18/6. Ive picked up plenty of things from him for awhile now, and do my best to incorporate them, and its paid off.

I keep my canopy temperature at 78-81 degrees, limit my DIF to +10 or less, and keep my ADT above 70 at all times. I haven't gotten a chance to incorporate the cold morning dump yet, but Im sure it'll have an affect just like he says.

Light source is a 6 bulb T5HO fixture running all G.E. Starcoat 54w 6500k bulbs.

Oh, and dont over crowd your plants.

Below is a picture of a 23 day old seed plant from Cannacopias Lemon Grass Thai x Deep Chunk. This plant was 5 inches tall before I removed its 7th node.

I hope I dont sound like that I am showing off a plant, but these pics are proof that Spurr's advise is sound, and will help you grow amazing plants.

 

[3rdEye]

Dave What guidelines do you use for plant spacing if i may ask?

I wanted to chime in with my own very rough findings using DIF between -5 --> 5. It started off due to a heat issue that arose in the house. This fortuitously coincided with my reading this thread.

The flowering room temperatures have been a bit on the low side, which is simply the best that can be done currently. That being said the room temps have been 62-68 and i have plants that were put into flowering that have only shown 2-3inches (5.1-7.62cm) total stretch and are now almost 5 weeks into flowering. I should point out that before i could fix the heat issues the DIF value was 10-15 and my plants stretched much more even with average lower temperatures.

I am going to do my best to continue to create similar conditions and monitor stretch on various cultivars. So far my rough preliminary results indicate that using low DIF values should be looked into more. It will be nice to get some of this automated, but currently i adjust temps manually via increase/decrease of fresh cold air.

Sorry about any threadjacking spurr

back on topic... ahem..

I have noticed less stretch in general with all of my plants by using either MH or MH/super HPS combination for vegetative and flowering growth as compared to using only super HPS for vegetative and flowering growth. I don't have any quantifiable data, but my observations have been consistent to date.

So thanks for the papers and thread. It's proven quite fruitful already.

 

[Dave Coulier]

Dave What guidelines do you use for plant spacing if i may ask?

If generally try to keep enough room between the plants so that lower leaves on each of the plants still are bathed in light, and not being covered up by their neighbors.

Keeping them spaced apart is very important. Shortly after these pics were taken, I allowed them to get too crowded, and they started to stretch considerably. Even when spaced apart, the SAS(Shade Avoidance Syndrome) can be triggered by Far-Red light reflected from neighboring plants, but I haven't found that to be any significant problem. The stretch really began when they started to create a dense canopy reducing the R:FR ratio below the canopy.

 

[hades]

Using red plastic mulch actually increases the far red:red ratio over the incoming light sources fr:red ratio from what I have read. White mulch will have the same reflected far-red:red ratio, and will provide the same benefits with regards to soil temp, water loss.

Check out this PDF to learn more.

Hi Dave,

Pleasure to meet you, too. I am sorry if I was not very exact about that, it had been a few years.

It came in two types, one was a plastic mulch and the other was sheets of plastic that you laid on top of your rowed beds. Red absorbs all other colors and reflects red back into the canopy, thereby increasing the ratio of red to far red, like you said.

There is a lot of research about this. You can find it here:
http://plasticulture.psu.edu/?q=node/4

What Does Colored Mulch Do?
Colored mulch mimics the reflective patterns of the green leaves of neighboring plants. The plant will sense the increased ratio of far-red to red light as though it is reflected from the nearby plants, when in fact it is just the colored mulch. The colored mulch "tricks" the plant into putting more energy into shoots to outgrow other plants. Some colored mulch even "tricks" the plant into producing more and better tasting fruit.

http://www.plasticulture.org/fg_wavelength.htm

• Red – partially translucent allowing radiation to pass through and warm the soil, but also reflects radiation back into the plant canopy changing the ratio of R:FR light. This may result in changes in plant vegetative and flower development and metabolism leading to early fruiting or increased yields in some fruit and vegetable crops.

I'd be interested to find out the different effects this could have on indoor/outdoor cannabis plants. It seems that different colors effect different plants in different ways =D Like peppers have shown 12% yield increase over a three year period when grown over silver plastic mulch.

 

[spurr]

There is a lot of research about this. You can find it here:
http://plasticulture.psu.edu/?q=node/4
http://www.plasticulture.org/fg_wavelength.htm
I'd be interested to find out the different effects this could have on indoor/outdoor cannabis plants. It seems that different colors effect different plants in different ways =D Like peppers have shown 12% yield increase over a three year period when grown over silver plastic mulch.

Hi hades,

Thanks for posting those links, I will read up on this topic for sure, neat stuff! PSU is a great source of info from fungi to plants

1. However, I am a bit confused. The quote you cited and I re-posted below, seems to be either worded poorly or going counter to what we are trying to achieve in this thread. In the following quote the author(s) is(are) stating the goal is to increase the far-red to red ratio; which is the opposite of what we want, i.e., we want to increase the red to far-red ratio. Also, note that the author(s) write(s): "The colored mulch "tricks" the plant into putting more energy into shoots to outgrow other plants." In effect, they doing the complete opposite of what we want to do:

http://plasticulture.psu.edu/node/126

What Does Colored Mulch Do?
Colored mulch mimics the reflective patterns of the green leaves of neighboring plants. The plant will sense the increased ratio of far-red to red light as though it is reflected from the nearby plants, when in fact it is just the colored mulch. The colored mulch "tricks" the plant into putting more energy into shoots to outgrow other plants. Some colored mulch even "tricks" the plant into producing more and better tasting fruit.

2. That said, I did find this info in the PSU link you posted. The following quote is referring to what we want, i.e., increased red to far-red ratio, and this quote is the opposite of the quote above. So it seems the goals of the two different pages at the PSU site are opposite, or the quote above is just worded very poorly:

http://plasticulture.psu.edu/?q=node/4

Both red and black mulches reflected about the same amount of PAR, but red plastic increased the ratio of red:far-red wavelenghts (R:FR) in the reflected light. The R:FR ratio and the amount of blue light reflected toward the canopy apparently are critical. In turnips, blue and green mulches induced longer leaves and higher shoot:root ratios than white mulch. The R:FR ratio reflected from white plastic is lower than that of sunlight.

More later

 

[spurr]

Oh yea,

Using plastic mulch is a better option than plastic sheeting to allow the media to release Co2, etc., and for not too greatly decreased evapotranspiration (using plastic sheeting can reduce evapotranspiration too greatly).

 

[gloryoskie]

The mulch vs sheeting have me puzzled, gas transmission properties of one vs the other, etc. I will look into it. Sheeting seems more user friendly. Also I have read through many threads and outside links of yours and am in debt to you for the info. I grow soil, micro, my needs are modest, however I follow the science, not the rote. Thanks again.

robertmarvel.com, a commercial site with some info on plastic mulch. I have no affiliation.