Advanced light cycle

[Riddleme]

Just wondering how you're quantifying any change and why you think your plants experience midday depression of photosynthesis?

To be honest, I'm not sure if they do or not, they grow great, lots of vigor but by midday there are a few fluctuations in temp and humidity. I grow in an open (not sealed in anyway) room in my basement lights off temp currently 72 goes up to 78 with lights on canopy temp reaches 90 by noon (ambient stays at 78) I do my best to mimic outdoors this way RH changes a couple of points up by midday, so it is something I want to see? I have a microscope camera so I guess I could look at the stomata to record changes?

I have grown for over 40 years so to quantify I would normally go by simple observation as to whether anything in terms of plant response changes I have run some strains for years so I know what to expect from em I very rarely have any problems

Since it is a seed run it won't hurt anything to find out?

my garden ,,,,,,

 

[Beta Test Team]

I wasn't trying to discourage you or disagree, I was just wondering about your 'whys' and 'hows.' Mostly because midday depression of photosynthesis is a problem for outdoor and greenhouse plants more than indoor plants (as the former are often not controlled environments).

If the canopy temp gets to 90'F and above then your plants may indeed experience midday depression of photosynthesis (possibly due to negative effects of temp above about 90'F on rubisco activase and therefore active rubisco).

I wonder, why not dim the lights around midday to keep temp below 85'F? [EDIT: I see you're using fluorescent lamps, so dimming likely isn't a good option.) Though that solution can be expensive to setup in an automated fashion.

In terms of quantifying changes in photosynthetic rate, you're likely to have little success with measuring stomata aperture. The least expensive way I can come up off the top of my head is indirect: IR gun to track leaf temperature and VPD (as affected by leaf temp) around midday would worthwhile because we know how high VPD can affect plants.

If you had a chlorophyll fluorometer you would be in business, but they're kind of pricey (a few grand).

Let us know if you find interesting results from you test!

 

[Only Ornamental]

...
By the way, I have enjoyed our chat here. You're quite smart

The joy is all mine .

Quite smart, eh? I'm literally rolling on the floor right now trying not to lose my supper .

I don't know for sure how smart I really am. Last time I did an IQ test I stopped prematurely, got too bored by the questions and still hit the 140.

Though sometimes, it gets quite lonely up here on the tip of the intellectual Olympus...

But back to topic:
Wouldn't it be possible to directly determine midday depression by measuring CO2 consumption (room ppm) or indirectly estimate it via CO2 usage (of the gas cylinder) each in a more or less sealed environment? The former obviously only in a non-supplemented room and the latter when using CO2 supplementation.
Judging from my experience with CO2 for cell culture incubators I'd assume the results to be rather approximate but good enough for a YES, MAYBE, or NO.

 

[Beta Test Team]

[FONT=Arial, Helvetica, sans-serif]By the way, I have enjoyed our chat here. You're quite smart [/FONT]

The joy is all mine .

Quite smart, eh? I'm literally rolling on the floor right now trying not to lose my supper .

I don't know for sure how smart I really am. Last time I did an IQ test I stopped prematurely, got too bored by the questions and still hit the 140. View Image
Though sometimes, it gets quite lonely up here on the tip of the intellectual Olympus...

But back to topic:
Wouldn't it be possible to directly determine midday depression by measuring CO2 consumption (room ppm) or indirectly estimate it via CO2 usage (of the gas cylinder) each in a more or less sealed environment? The former obviously only in a non-supplemented room and the latter when using CO2 supplementation.
Judging from my experience with CO2 for cell culture incubators I'd assume the results to be rather approximate but good enough for a YES, MAYBE, or NO.

Yes, but too expensive to setup correctly. You're basically describing a photosynthesis chamber, which can be accomplished with a leaf clip. But I think it would be more expensive (and not very accurate) to go that route (DIY) vs. buying a chlorophyll fluorometer and inferring photosynthetic rate and plant stress that way.

Using your exact proposed method though I would say no.

P.S. When I write you're quite smart that's me stating I'm very impressed. I have worked with PhD astrophysicists and quantum physicists often enough to know above average intelligence when I see it (and you're above, above ). I too have had those tests over the years...

 

[Beta Test Team]

By the way, how did you use subscript? I've been looking for that and didn't see it as a feature here.

 

[Only Ornamental]

Subscript? Try font size 1 .

PS Are we having a spell of self-opinionatedness and compare our mental dicks in public?
I got to sober up... LoL!

 

[Beta Test Team]

Ha, no. I think you would win (I was just teasing you back a bit.)

 

[Riddleme]

First day of the new light cycle and already an observation has taken place. I have 2 in 1 gallon pots that have had to be watered every day for the past few weeks and when I went to water em today after their first 1/2 hour break they were fine, seems I can wait till tomorrow

for the last week if I missed it by more than 20 min they would be droopin

 

[Mikell]

Personally I am much more interested in what you, Shaggy or Ornamental have to share. You are smokers like me, open minded and not here for donations.

HAH, appreciate it, but I know my limitations, and when to stop talking and start listening.

(most of the time)

(some of the time)

(rarely.)

Found it (See the screenshot)

From:
"Plant Growth Chamber Handbook" (Chap. 1., page 24)
http://www.controlledenvironments.org/Growth_Chamber_Handbook/Plant_Growth_Chamber_Handbook.htm (all chaps are as PDFs)

I was fingercrossing for post-harvest analysis, though admittedly I haven't read beyond the quoted paragraph, nor touched the first two links. The more I work, the less I read. Piss-poor trade off...

 

[stihgnobevoli]

for the way we grow weed, lights on lights off. i personally don't think this will effect anything, maybe decrease your yield a little or increase your harvest time. when the sun sets outside and is rising, the intensity doesn't actually noticeably change. does the sun not feel as hot on your skin at 6am as it does 6pm? is it cooler to you? i've never experienced this. the air temps are cooler since the sun is heating less area of the earth. but the actual power of the sun shouldn't change. i know about the color temperature range. but that's just in relation to how we perceive the sun . like full light vs shadows. the light we see might look different but the spectrum we don't see is still going full tilt.

you should try it regardless. i myself just don't think it will make any positive change. you don't have an option for that in the poll.

 

[Riddleme]

Well I said I would come back here and report if there was anything to see from the new light timing for midday depression and damn if it ain't killin it. To repeat, current light timing is 6.5 on, .5 off, 4 on, 13 off which = 10:30/13:30 total and my plants in week 5 of flower are goin better than ever

you can follow in my grow diary here,
https://www.icmag.com/ic/showthread.php?t=295624

But I'll be doin this from now on !!!

 

[Beta Test Team]

I see no quantification, no data, and no reason to draw the conclusion you seem to have drawn.

See what I wrote in this thread, especially about lag period.

And under those lamps I doubt you're going to have midday depression of photosynthesis, as caused from in part by irradiance (rather than say, high VPD), anyway. Do a bit a research into what triggers the reaction, that should give you a better idea of how to research this issue if you wish to do so.

Outdoor plants and those that are in poorly controlled environments, are those most likely to experience midday depression of photosynthesis.

 

[DooDahMan]

Yeah, go away with that nonsense, 35 years of experience and real life experiments don't mean a thing and nor do the pics showing these differences. You better see what BTT said earlier in this thread before making any observations.

 

[Riddleme]

I see no quantification, no data, and no reason to draw the conclusion you seem to have drawn.

I guess your not me, observation is useful tool and I have seen that which I have seen. Not tellin folks to jump on this or change what they are doin, simply sharing what I have personally observed. What folks do with that info is up to them. You have chosen to not believe me and that is your choice to make. I'm not here to argue about it, if others wish to try it and observe for themselves that is their choice.

But it is damn sure workin in my garden

 

[Baron Greenback]

I think it is too difficult to bring too many outdoor techniques inside. I thought about a moonlight equivalent, reducing hours of light to mimic changing seasons amongst others but it's a completely different challenge. Outdoors, you are pretty much at the mercy of mother nature, indoors, you can provide the perfect growing day, every day.
In doors, they'll do what I say, when I say (well, that's the plan anyway).
It's easier to take indoor techniques outdoors, pruning and shaping can get some monsters, but I do prefer indoor grown as my experience of outdoor is a little limited.

 

[Mate Dave]

This goal of yours can be achieved if you set up a multiple light room with HPS, CMH and a few fluorescent fixtures with differing spectrums.

Why you would bother to do this is beyond me and I can't fathom why you'd get better results than just constant Max-Lumens.

I've voted Highly controversial speculation.

Once plants are fully saturated with Phytochrome and Cryptochrome the lights can be reduced without ill effect, it's still going to effect the bottom line costs.

There is a equation for photosynthesis and it changes with each input difference, mixing it up like you suggest is gonna make a long set of calculations for what?

 

[Icemud]

Hey everyone.. Great topic of conversation and I am really impressed with the ideas and topics being thrown around here.

I voted for

[FONT=Arial, Helvetica, sans-serif]Has a good foundation, but must be proven.[/FONT]

I had the opportunity to run some LED lights by a company called Intelligent Gro and they offer a LED that has the capabilities in which this thread is about. They had 3 channels, a red (bloom), a blue (veg) and a white/red/blue center COB light called (veg). Each channels was able to be controlled by intensity from 0-100 at 1 hour increments for a 24 hour period. Being the lighting enthusiast I am, I was excited to test the lights out... but this also lead me to the same question as this thread was about... does dimming/spectral changes during the daylight period influence the plants positively, how and to what extent...

I've done a ton of research over the years in regards to lighting based on my love for lights (for some reason I have always been fascinated with them) but also for my want to know everything I can about producing the best cannabis I can. I voted the way I did because there is a ton of reasearch out there on plant lighting, but it seems that even between different studies there are arguments on how plants use light, and I have seen that this not only differs between plant types but also different phenos.

I was reading into mid day depression and I will have to find the source in my huge library of abstracts and pdfs I have saved relating to lighting, but it seems that I remember that the highest rate of photosynthesis occurs within the first few hours of the daylight period, followed by a mid day depression, ramps back up to almost maximum, and then slowly tapers off towards the end of day. Now this I don't believe was a cannabis specific study, but it is very interesting based on this topic...

If we were able to change the intensities of lighting over the daylight period, then we could max our plants efficiency as well as max our electrical efficiency savings as well. For instance, if that is true about cannabis, where the highest rate of photosynthesis is in the first few daylight hours, then if we look at it a music equalizer... we could actually lower the intensities in the morning (like lowering the bass in a bass heavy song), possibly reduce the potential of a mid day depression, and drive photosynthesis on a constant rate through the day by increasing the intensity (speculation). I don't know which would be better as there are other factors that play into mid day depression as well such as UV levels but just a thought.

This is why I voted for "has a good foundation, but must be proven" because I do believe it has application.

I do plan on running some test/comparisons with the Intelligent Gro lights, but my grow area currently is in use testing other LED lights so the experiments will be on hold for a while until I can find the room to do them. I would like to run a test, same spectrum output, but one on a 12/12 and one on a dimming (sunrise/sunset) schedule. I know it will not be a completely accurate comparison when I do this due to the actual LED chips wavelength changing due to junction temp changes when dimmed but I think It still may provide us some insight into how a dimming vs non dimming schedule may change things.

Anyhow I am fairly new on this forum, but definitely am very impressed with the discussion here...and I have to say Beta Test Team....extremely impressed with your knowledge I look forward to meeting all of you and hopefully helping solve the mystery of plant lighting

 

[Icemud]

Here is the results of a study done on pepper plants using different daylight intensities. I know its not cannabis, but it does show that the changes in intensity could also possibly benefit us as well.


Source: EFFECT OF SUNLIGHT REGIMES
ON GROWTH AND YIELD
OF PIQUIN PEPPER
(Capsicum annuum L. var. aviculare)
L. A. Rodríguez-del Bosque¶; R. Sánchez-de la Cruz; M. M. Silva-Serna
Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP)
Campo Experimental Río Bravo. Apartado Postal 172, Río Bravo, Tamaulipas, C. P. 88900. MÉXICO
Correo-e: rodriguez.luis@inifap.gob.mx (¶Autor responsable)

Piquin yield was highest in the morning sunlight condition,
and lowest in the afternoon and all-day treatments.
None sunlight condition produced an intermediate yield.
Plants in the afternoon and all-day sunlight coincided to have
the lowest growth and yield, suggesting afternoon sunlight
was responsible for the poor performance of piquin pepper
in this study. When plants grow under a leaf canopy, where
the light received is primarily far-red, phytochrome is removed
from their leaves and their stems become elongated
(Salisburry and Ross, 1992), a situation observed in this
study in the none sunlight condition, in contrast to the short
stems resulting from the all-day and afternoon light conditions.

 

[Beta Test Team]

Midday depression of photosynthesis (either single or double) is not a forgone conclusion for indoor plants, nor outdoor plants.

And it's much more likely to happen to outdoor plants in hot and dry climates, especially when it's bright outside (around noon, well above 1,250 PPF, which is irradiance most indoor cannabis growers never use).

This issue of midday depression of photosynthesis is very likely a non-issue for indoor plants, especially those with well controlled environments. It's very safe to assume indoor plants do not experience it, rather than to assume they do experience midday depression of photosynthesis.

 

[Riddleme]

Midday depression of photosynthesis (either single or double) is not a forgone conclusion for indoor plants, nor outdoor plants.

And it's much more likely to happen to outdoor plants in hot and dry climates, especially when it's bright outside (around noon, well above 1,250 PPF, which is irradiance most indoor cannabis growers never use).

This issue of midday depression of photosynthesis is very likely a non-issue for indoor plants, especially those with well controlled environments. It's very safe to assume indoor plants do not experience it, rather than to assume they do experience midday depression of photosynthesis.

and yet my plants are growing better since I adjusted for it?