LED's make Less Heat. Do plants Yield more in Higher Heat?

[MeanBean]

I grow with LED's, yeah I know right?

My grow area stays coool. like 70 - 75... Just wondering if raising it to 85 would help..

Any input is welcome

 

[Hydro Cabbage]

70 -75 is perfect...my room doesn't get above 77 and I have HIDs

 

[hamstorg]

Hey Meanbean,from what i've been seeing in Mr.Sleepies thread,i would advise you to actually go up with your temps,as we could see Sleepy's plants had stunting whilst having low temperatures,but to be honest,testing should be done,different grows with different temperatures.

Why not try out a new led grow with 85 degrees constant?

 

[secondtry]

Ideal temp for peak Pn (rate of photosynthesis) with Co2 at 750 ppm (about what it used to be millions of years ago) is ~ 83'F; I keep it at 80-84'F but the work by Chandra, et al., 2008 cited 25-30'C (77-86'F) as an acceptable rage with ideal temp what I stated. But the fact you grow with LEDs mean the Pn will be low anyway, so raising room temp to raise Pn might be a non-starter. Without Co2 ideal temp is about 75-78'F.

I would do two things if I were you: Get Co2 and get HPS. Then raise room temp to 80-84'F.

Chandra, et al., 2008
Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Journal Physiology and Molecular Biology of Plants
http://www.springerlink.com/content/a3527u6018823x43/

Abstract

Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m−2s−1), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol−1) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20–25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m−2s−1 PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m−2s−1 PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m−2s−1 and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m−2s−1. In view of these results, temperature and light optima for photosynthesis was concluded to be at 25–30 °C and ∼1500 μmol m−2s−1 respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol−1) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol−1) level. Elevated CO2 concentration (750 μmol mol−1) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m−2s−1 PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.

...................

At 20 and 25 oC, WUE (water use efficiency) increased with increase in PPFD up to 2000 μmol m-2s-1 (Fig. 5). On the other hand, WUE increased only up to 1500 μmol m-2s-1 PPFD at 30 oC and decreased thereafter at higher light levels. Temperature higher than 30 oC had an adverse effect on WUE of this species. The maximum WUE was observed at 30 oC and under 1500 μmol m-2s-1 PPFD. Photosynthesis appears to have a greater influence than E (transpiration) over regulating water use efficiency in C. sativa. A highly significant positive correlation was observed between WUE and PN (r = 0.92). Together, high temperature and high PPFD had an adverse effect on the WUE in C. sativa.

GL

 

[GreenThumbBumb]

Why do people always respond with stupid opinions that dont matter. This thread has nothing to do with HID. It seems they do prefer a little higher temp range, i let my get up to 85 and they seemed to love it but im running aero and didnt want my res temps going uo with it. Next run will be hempy and plan on letting it get around 85. Even with my HID plants performed fine in 85.

 

[Grat3fulh3ad]

But the fact you grow with LEDs mean the Pn will be low anyway

GL

you'll need to back up that dubious assertion.

 

[MeanBean]

Thanks everyone! great points but yes I would like to hear more about this Pn shit.

I KINDA wanted to add UV to my garden, LED is a bit short of UV, heard this could help. has anyone done this? Do you know the spectrum range to look for, perhaps a place online to buy them?

I know adding like 2 cfl bulbs will add about 10 degress to my cab... Always could throw another LED unit in there as well. the 126w Penetrator adds about 10 degreees.

 

[secondtry]

Why do people always respond with stupid opinions that dont matter. This thread has nothing to do with HID. It seems they do prefer a little higher temp range, i let my get up to 85 and they seemed to love it but im running aero and didnt want my res temps going uo with it. Next run will be hempy and plan on letting it get around 85. Even with my HID plants performed fine in 85.

He seemed to want to increase yield, that was his whole reason for the thread. And to increase yield increasing heat won't matter, he needs to increase PPFD and PAR range; hence, he needs HPS to increase yield so yes, I answered his question more thoroughly than you did.

And btw, Pn is the way to quantitate plant response to light stimuli, that and respiration/transpiration.

 

[secondtry]

you'll need to back up that dubious assertion.

Dubious? What makes it dubious?

In that study it was shown the peak Pn was from 1,300-1,500 PPFD, this has been found by other studies too. That is why I made that statement, please consider that LEDs don't emit enough PPFD to reach peak Pn of cannabis. If a LED was to offer 1,300-1,500 PPFD it would probably have to be inches from the canopy, if not closer.

And then we have the PAR range: red nanomters (600-700) offer the higherst Pn under LEDs, while green (500-600nm) is showing to offer highest Pn under HID with red a second close, blue (400-500nm) offers the lowest Pn. The point being LEDs only offer a few nm, if that, in red and blue; while HIDs offer the whole red, green and blue PAR range (in varying SPDs), that means HIDs will offer more Pn than LEDs by the fact they offer so many more nanometer is red and green.

Please see my posts in this thread for more info:

"Investing in new lights LED or HID?"
https://www.icmag.com/ic/showthread.php?t=158600

Here is a quote of mine from that thread:

A common misunderstanding is by lamp makers who report irridiance by PAR, by people in cannabis world, and by most all grow shops and cannabis gurus that define PAR as a measure of irridiance, and it's not, it's a identification ("qualification") of photons which drive photosynthesis, that's all, and it is a range from 400-700 nanometers (wavelengths). Now, PPFD (Photosynthetic Photons Flux Density) is what the lamp companies mean when they write PAR, and PPFD measures ("quantitates") the irridiance of photons (umol) within a predefined area at the canopy within PAR range (400-700 nm); basically counting how many photons within PAR strike the canopy in a sq meter per second. That is the light measure to use for plants, NOT lumens, lux, Kelvin, footcandles, etc. To get more exact the PPFD per nanometer (not the total PPFD) needs to be weighed with the relative amount of photosynthesis provided from each photon in each nanometers, i.e., "Quantum Yeild", QY.

Cannabis has ideal-maximum rate of photosynthesis (Pn) with irridiance of 1,300-1,500 PPFD. Much over 1,500 PPFD and "photoinhibition" will lower Pn and Pnnet.

HTH

 

[secondtry]

Thanks everyone! great points but yes I would like to hear more about this Pn shit.

I KINDA wanted to add UV to my garden, LED is a bit short of UV, heard this could help. has anyone done this? Do you know the spectrum range to look for, perhaps a place online to buy them?

I know adding like 2 cfl bulbs will add about 10 degress to my cab... Always could throw another LED unit in there as well. the 126w Penetrator adds about 10 degreees.

hey,

For Uv you want Uv-b and some Uv-c; although UV-c is dangours so it's best to just stick with UV-b. I have used it for about a year and I have written much about it; accourding to light quantum phssycs. I use a "Osram Ultra-Vitalux" 300 watt replite lamp; IMO they are they way to go.

Please see this thread at CW, I am "guest", I used to be a mebmer there. I offer all info you need to know, all according to fact based math and proven scientific theory. I offer the exact irridiance to use and how to meaure it. Too much info to put here, but in that there I have two buddies who are also using UV but they use differennt lamps. Here ya go:

"10K Bulbs....are they good for anything?"
http://cannabis-world.org/cw/showthread.php?t=5072

P.S. It's been shown the UV-b does increase secondary metabolite production in cannabis, like THC-A a great deal, I offer many white papers and studies regarding UV-b effects upon cannabis and one great one about it's increase effect upon THC-A. I notice a different in the strength of the UV-b cannabis and I will start using semi-quantitative TLC soon (comparative) which will provide analytical assays (until I can afford HPLC and/or GS )

 

[Grat3fulh3ad]

It's more about PAR than lumens. non-PAR lumens do not influence Pn.
You need to back up your dubious assertion.
http://www.icmag.com/ic/showpost.php?p=2869081&postcount=7
Looks like 1500w of LED can do plenty of intensity to be more than "inches" from the canopy... Perhaps you should be slower to jump to conclusions.

 

[Grat3fulh3ad]

anyhow... I'll be setting up a proper 1000w hps vs. 504w LED test soon...
Should give me all the proof I need one way or the other.

 

[Grat3fulh3ad]

There are uv LEDs, it would be easy to add a few to an array.

HID bulbs are shielded to block UV, right?

 

[secondtry]

It's more about PAR than lumens. non-PAR lumens do not influence Pn.
You need to back up your dubious assertion.

No it's not. It's more about PPFD, lumens are not for plants. Look up "photoadaptation" in terms of plants adapting to the spectrum they are provided.

Ideally we use Yield Photon Flux (YPF) range of ~ 360-780nm, not 400-700nm (PAR) because in fact, nm outside PAR do drive photosynthesis.

How else would you like me do back up the facts of light quantum physics for you?

http://www.icmag.com/ic/showpost.php?p=2869081&postcount=7
Looks like 1500w of LED can do plenty of intensity to be more than "inches" from the canopy... Perhaps you should be slower to jump to conclusions.

All those pics tell you is one can grow and flower cannabis under LEDs. And I agree, that was not what I wrote. I wrote that Pn will be lower with LEDs and that to reach ideal PPFD of 1,300-1,500 LEDs would probably have to be inches from the leaf. Both of which are correct and your point about 1,500w LEDs is not relevant. Now, if you measure the Pn and the PPFD *then* I would be interested.

HTH

 

[MerryPrankstr]

Actual facts not BS propaganda here, please!

Actual facts not BS propaganda here, please!

I am one of a group that has been successfully growing with LEDs for the last couple of years. We don't sell our lamps, but all our work is public domain and everyone is free to go out and build their own. SecondTry's comment on requiring more light intensity is indeed a fact, but after that I'm afraid he has things quite muddled.

There are different components used in LED lamp construction that can radically change performance in your grow room. The most important factor is the actual LED emitters.

If you are trying to grow with 1 watt emitters (a la LED Girl's lamps) they will perform marginally at best. Not trying to put her down, it's just that these are cheaper LEDs that don't have the output needed to flower robustly like in natural daylight. LED Girl would serve herself and the community better by moving on to the newer, more powerful technology ( i.e. 15 and 45 watt emitters), but when suggestions of this nature were made to her, she has abruptly deleted all such threads. Too bad! We are just trying to help her develop her product and help others.

With 2 or 3 watt emitters, we actually start to see some real good flowering and at 5 watt emitters we have an even output in photonic flux to match HPS and MH lamps. With the newest 15 watt emitters one actually gets so much light output that it is equal to the sun at noon in a tropical latitude.

Tests made by a friend who is a legal Hawaiian Med Grower were conducted to compare his latest build against natural tropical sunlight, and the LEDs outperformed sunlight!

Back to the original question, I have found that the best growth was obtained at 80-85 F temps during the day, but I got better F to M ratios from seed keeping my grow at 75-78 F.

M.P.

 

[Grat3fulh3ad]

PAR is for plants.
PAR = Photosynthetically Active Radiation.

How many photosynthetically active photons are striking the leaf surface, and how efficiently photosynthesis is carried out at a given wavelength.
Why make the plant adapt to a spectrum you provide, instead of adapting the spectrum you provide to the plant's need?

Side by side 1000w HPS vs 504w LED will tell the only story that matters.
Pn = dry weight, ultimately.

If I spend half energy and get the same weight then I am photosynthesizing the provided photons more efficiently.
If the weight is comparable, then I'd say there was more photosynthesis going on, and that the rate of photosynthesis (Pn) was higher.
If the weight from 504w LED is 1/2 the weight from 1kw hps, then the Pn must be roughly the same per energy cost.
If the 1kw hps bests the 504 LEDs by better than double, then I'll buy your assertion.

 

[bloyd]

I look forward to your led show head, do you plan to use a production model light or is it something you are designing?

 

[secondtry]

anyhow... I'll be setting up a proper 1000w hps vs. 504w LED test soon...
Should give me all the proof I need one way or the other.

There is already plenty of "proof" and to carry out any meaningful testing you need to know at least the Pn, Pnnet and PPFD (weighted to Quantum Yield); otherwise you will be offering subjective non-analytical opinions based on assumptions as results. I have as much 'proof' (i.e. scientific theory; there is no scientific fact) as should be needed in this very thread. Please, don't just po-po what I wrote, read it and digest it. You will see you are incorrect and your understandings are not at all accurate. I am not trying to be rude, just to force a bit of reality upon you to help you; it's like tough love

 

[MeanBean]

I am one of a group that has been successfully growing with LEDs for the last couple of years. We don't sell our lamps, but all our work is public domain and everyone is free to go out and build their own.
M.P.

Where can I see this?

Also I need a smaller uv CFL than 300 watts!

Looks like I have a ton of reading to do! Please quit turning this into a LED bash.. All though I do apreciate the point of view of Bulb growers!!

That's like me asking how do I get around in a wheelchair and you telling me to shut up and walk... not gonna happen. HELP me in the situation I am in.... LED

I was asking about temps though not Par!!!! lol still interesting!

 

[secondtry]

PAR is for plants.

Ok , this is my last try to help you:

PAR = Photosynthetically Active Radiation = a range of nanometers (wavelengths) which drive photosynthesis, *not* a measure of irridance (how much light). Aloguht, as I wrote, there are nm outside PAR which drive photosynthesis, and the "accessory pigments" in leaf can use non-PAR and transfer energy to chlorophyll A and/or B IIRC.

PPFD = Photosynthetic Photon Flux Destiny = the amount of photons within PAR hitting the canopy per sq meter per second.

OK? So to recap: PAR = 'what is it' and PPFD = 'how much of it is there'.

PPFD is used to count/measure light (photons) for plant, not lumens, lux, Kelvin or footcandle.

If you don't trust me trust goolge, even tho I'm way funnier than goolge!