Study finds HPS spectrum results in higher photosynthesis rate (per light quanta) than LED spectra

From:

You see that at any given similar PPFD the HPS spectrum results in a (slightly) higher CO2 assimilation rate.

Before the HPS vs LED comparison, the study compared 3 LED lights to find out the best - which was chosen subsequently.

I find this noteworthy because the study itself doesn't seem to mention this, and sadly, they weren't able to use the LED to reproduce PPFD states higher than 1000umol. Which, *I suspect*, the LED would fare even worse due to the blue/red vs green-light mismatch. (green-light has been proven to work better photosynthetically at higher PPFD)

The study itself concludes that LED is far superior to HPS but the argument here relies solely on higher total raw light output, better uniform canopy spread. They state that HPS at its recommended hanging height isn't able to create the same amount of light than LED at all - which IS very believable.

But in a way a skewed argument because in a commercial operation, like a hall or big greenhouse, it is general practice to simply hang as many fixtures up in a cross-lighting setup until saturating light-levels are achieved.
Which will also take care if uniformity of light-spread.

I do not wish to shill for any type of lighting system, but I f*** hate it when studies are done in such a horrible way to basically cash in on a lighting-system weakness.... I don't need a study to realize a HID bulb has less uniform spread than a LED bar light when these systems are used as a single light-source in a tent.
Any PPFD chart shows that already. And the PPF umol/J in the datasheet also gives a clear info on the power of a light-source.

But the HPS spectrum results in a quicker photosynthate-accumulation than the LED spectrum. HPS seems to drive photosynthesis-rates higher, thus, less light-quanta will be actually needed to arrive at the very same amount of carbohydrates.

Keep in mind though it's just a single study and the results may be not without faults. Though the result is in line with my general knowledge about the various light-colours' effects on photosynthesis.
Sadly some of the LED vs LED preliminairy data isn't shown either, which could have been used to create even a bigger gap of HPS vs averaged LED data

Kassiopeija said:

From:

https://www.scirp.org/journal/paperinformation.aspx?paperid=108091

But the HPS spectrum results in a quicker photosynthate-accumulation than the LED spectrum. HPS seems to drive photosynthesis-rates higher, thus, less light-quanta will be actually needed to arrive at the very same amount of carbohydrates.

Click to expand...

still tho doesnt leds close this gap by being much more efficient than hids? wouldn‘t it still take less wattage to arrive to that point with leds? i’m really curious.

also this sounds cool

I grew under HPS for well over a decade and any of my post-blurple leds have out performed hps in every instance. If the above study is accurate I'd have to assume that the superior efficiency of led is more than making up for any spectral deficiency.

crimsonecho said:

still tho doesnt leds close this gap by being much more efficient than hids? wouldn‘t it still take less wattage to arrive to that point with leds? i’m really curious.

Click to expand...

Yeah they do, I mean you see the yellow n light-blue 2 "dots" in the graph as well that sets both systems apart, by much actually.

And what you quoted is true as well although if it's at maximization of THC etc I'd go the UV-B/A N-UV/blue "route" where, conventional white LED also would need a boost.

I just find it noteworthy that the green/yellow/orange/red/IR HPS spectrum has been proven to create higher photosynthetic rates than one of the top-notch LED specs.

Maybe LED could change to better quality as well? Thing is that orange n green are better from many physio-biological aspects anyway...

Kassiopeija said:

Yeah they do, I mean you see the yellow n light-blue 2 "dots" in the graph as well that sets both systems apart, by much actually.

And what you quoted is true as well although if it's at maximization of THC etc I'd go the UV-B/A N-UV/blue "route" where, conventional white LED also would need a boost.

I just find it noteworthy that the green/yellow/orange/red/IR HPS spectrum has been proven to create higher photosynthetic rates than one of the top-notch LED specs.

Maybe LED could change to better quality as well? Thing is that orange n green are better from many physio-biological aspects anyway...

Click to expand...

Exactly!
This why I've been talking with @Stephenj37826 about a 2200K based led - get that HPS spectral goodness and combine it with the ppfd distribution of led. Win Win

Kassiopeija said:

Yeah they do, I mean you see the yellow n light-blue 2 "dots" in the graph as well that sets both systems apart, by much actually.

And what you quoted is true as well although if it's at maximization of THC etc I'd go the UV-B/A N-UV/blue "route" where, conventional white LED also would need a boost.

I just find it noteworthy that the green/yellow/orange/red/IR HPS spectrum has been proven to create higher photosynthetic rates than one of the top-notch LED specs.

Maybe LED could change to better quality as well? Thing is that orange n green are better from many physio-biological aspects anyway...

Click to expand...

you know not really a fan of uv it degrades everything, even the full spectrum leds degrade the ropes hanging at the intakes and stuff i’m really not very interested in uvs just for that reason but yeah for thc that route is better i guess but full spectrum leds sit in the very happy middle for me

yeah maybe they should make a led array like that then we would truly see whats what. you propose to eliminate blue completely? also at that route wouldn’t that cannabinoid boost would be lost? because i can only guess the reason for that boost is either less heat or the blue spectra so eliminating blue or adding ir would cancel that boost, wouldn’t it?

OneHitDone said:

2200K based

Click to expand...

tbh I feel using a metric developed for humans will lead into the wrong lane (IF used as the primary base...)

hmmm what did he say?

I'm not set... not at all.... but what's know from other plants and photosynthesis generally now seems to become more evident for cannabis, too... though there need to be more studies to confirm that sure BUT.... my gut-instinct tells me here's much more to be gained than when growing lettuce... since hemp is one of the strongest sun-tolerant plants that there is!!

crimsonecho said:

you propose to eliminate blue completely?

Click to expand...

oh no blue is MANDATORY... but how much is needed talking in terms of "area under the curve" to establish a functional plant physiology? like this:

I'm more & more sighting evidence for a specialized Cannabis spectrum that could work with tops ppfd levels well beyond
2000umols (and yields accordingly) and green & farred are the most obvious choices to pump additional light where blue n red can't reach at all

I mean how many of you grow with 1500umols before CO2? Alot are shy of 1000umols because their tops will fry... or the investment cost is not returned??

Got 24k in 2 rooms... 12 led 12 gavita de's


Same crop, same inputs, but split between the rooms will be a fun comparrison

Samwell Seed Well said:

same inputs

Click to expand...

same power draw for the lights for each room, or canopy ppfd levels?

Higher photosynthesis rate but is it as efficient or more efficient? Doubt.

Kassiopeija said:

same power draw for the lights for each room, or canopy ppfd levels?

Click to expand...

I have a troll master sensor.

The HPS room is set up for 1300+ umol at about 18" between canopy and lights

The led room will be harder to achieve, due to the plants will be smaller, so slightly tilted to the HPS room

Samwell Seed Well said:

The HPS room is set up for 1300+ umol at about 18" between canopy and lights

The led room will be harder to achieve, due to the plants will be smaller, so slightly tilted to the HPS room

Click to expand...

the total amount of umol/s released would be a thing to look at


they say cannabis can take much more, and that the conventional method of "mere" PPFD is skewed... better - hang fixture higher + increase power draw

crimsonecho said:

you know not really a fan of uv it degrades everything, even the full spectrum leds degrade the ropes hanging at the intakes and stuff i’m really not very interested in uvs just for that reason but yeah for thc that route is better i guess but full spectrum leds sit in the very happy middle for me

Click to expand...

you're right it does and so it did from MH CMH back then...
the diode degradation a huge problem actually shying manufacturers away, yes... though I suspect many LED system have to be replaced due to their innane weakness towards high humidity..
that said pulsed UV may be the thing...

and you could use one of those mexican sombrero hats

and I also suspect HPS spectrum isn't "the end of that continuum" in regards to photosynthesis rates... not at all... given it's 840nm peak only creating heat...

I grow with an hps. It works great. I have no plans on changing unless someone wants to buy me a new LED light to replace what I'm currently using.

Kassiopeija said:

I find this noteworthy because the study itself doesn't seem to mention this, and sadly, they weren't able to use the LED to reproduce PPFD states higher than 1000umol. Which, *I suspect*, the LED would fare even worse due to the blue/red vs green-light mismatch. (green-light has been proven to work better photosynthetically at higher PPFD)

The study itself concludes that LED is far superior to HPS but the argument here relies solely on higher total raw light output, better uniform canopy spread. They state that HPS at its recommended hanging height isn't able to create the same amount of light than LED at all - which IS very believable.

Click to expand...

Hi Kassiopeija, I'll have to get @Prawn Connery to look at this later but I was under impression that green light was more effective at lower PPFD not higher? Do you know what spectrum the Fluence was? I know PC is always saying that indoor cannabis was selectively grown under HPS for 40 years before LEDs so plants that performed best under HPS were bred over successive generations. We have also seen different results for different strains. Some of the older strains still perform very well under HPS while some of the newer strains seem to like LED.

I know I'm expected to defend LED but I would think there would be more to it.

LEDs have their place. I personally never liked HPS, tried them years ago but always had to change back ceramic metal halides. These days I only grow in very small spaces that wouldn't work at all with HID lights, I could use a 150W HPS, but I doubt I'd yield the 350g I do with the 190w LEDs.

Kassiopeija said:

From:

https://www.scirp.org/journal/paperinformation.aspx?paperid=108091

View attachment 5103496
You see that at any given similar PPFD the HPS spectrum results in a (slightly) higher CO2 assimilation rate.

Before the HPS vs LED comparison, the study compared 3 LED lights to find out the best - which was chosen subsequently.

I find this noteworthy because the study itself doesn't seem to mention this, and sadly, they weren't able to use the LED to reproduce PPFD states higher than 1000umol. Which, *I suspect*, the LED would fare even worse due to the blue/red vs green-light mismatch. (green-light has been proven to work better photosynthetically at higher PPFD

Click to expand...

I will read the study later, but am I reading this wrong or is the smallish gap between led and hid getting smaller at higher ppfd?

I have been growing off and on since HID lights were THE shiz! And the combination of MH and HPS just always worked. That being said, the LEDs of today are MUCH safer and easier to deal with. However, I recently ordered an HPS conversion bulb for my old HydroPot MH magnetic ballast light. I might have to go old school on the next run!