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

[Fardsnarp]

Assuming plants started in water it is interesting to note that water absorbs red light first and continues down the rainbow. The blue absorbsion seen in plants may be a result of their earliest biology. The deeper you go the more blue light dependent. You already have a noticable loss of red as shallow as 5 feet. 1.5 meters for you metric centric.

 

[grotbags]

 

[Friendly_Grower]

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.

First off this is a wonderful thread.

For me I feel connected to the "Craft Grower" aspect.
That is where my grow-pride is.

I have a light footprint of four HPS and four COB LEDS with gullwing in the big room.
I have a compact florescent light rack I built that still delivers but it is true I am using the MarsHydro SP3000s in two tents now to facilitate some breeding. They seem to be okay with seedlings leaning in towards center growing at the edges of that LED.

After not being able to grow because of climate change for some years it's all about recreating what I knew and loved.
In the craft sense I like the radiant energy from HPS and sure that can be considered wasted energy use in a watts per gram paradigm but in my belief system it's a little Sunshine to a plant.

Besides I will be piping clean fresh heated air through the hoods into my living space as well come next winter's medical grow afte the proper build out. Waste not want not they say.

It's a enclosed front porch with enclosed grow room and what folks call a lung room where a Co2 burner lives.
The proper build out will happen this summer so if I can answer any questions later on I would be glad to share. We all learn from each other.

So again, in a craft sense radiant energy is part of the environs for my craft grow. A little artificial sunlight.
Remember these are living things. Charles Darwin wrote a wonderful treatise named The ‘root-brain’ hypothesis of Charles and Francis Darwin. We may focus on what Cannabis can do for us but we should also equally invest in what we can do for Cannabis in my opinion.
That is why "My Medical Strain" (MMS for a lack of naming imagination) F2 seed grow 2021-2022 was grown under HPS + LED in Organic Living soil.



LED should continue to evolve and for many it's good enough as it is today.
Again wonderful thread.


Friendly_Grower

 

[Friendly_Grower]

Nice thread Kassiopeija. These threads rarely stay on track. I find in grow comps LED and hps growers always get along and the trolls can't penetrate the conversation. In threads like this however the conversations always fall apart because the trolls, the parrots and the clueless always derail the conversation that the growers try to have.

Noise to Signal Ratios have always been an issue of grow sites.
It helps me to imagine that adults are sitting in chairs talking and there are children crawling around on the floor.
We just have to focus on the conversation and wait out their attention span.

 

[Friendly_Grower]

Oh, I just thought to point out another thing I have witnessed with HPS bulbs.

If you want the most out of your HPS bulb it should naked. Meaning that HPS in an enclosed glass such as a hood or tube did not result in the same growth as a hood without it's glass.

It's a trade off of channeling heated air away vs getting the most from say a Hortilux Eye.

Happy Growing!

 

[Kassiopeija]

Oh, I just thought to point out another thing I have witnessed with HPS bulbs.

If you want the most out of your HPS bulb it should naked. Meaning that HPS in an enclosed glass such as a hood or tube did not result in the same growth as a hood without it's glass.

When heat is a problem HPS is the wrong decision... and yeah, the glass will swallow some light... and the reflector also a good portion... vertical grows with a free hanging bulb seems to be the killer; esp. with another MH thrown therein

 

[Prawn Connery]

Actually the Physio-Indoor spec has photosynthetically available FR (700-780nm) in it.
The HPS huge IR spike's photons at 840nm will NOT be captured by chlorophylls

I believe double-ended HPS has a fair bit more Far Red in it than typical white-phosphor + 660 mono lights when you look at the area under the curve. Even a small amount more is proprtionally significant:

 

[Prawn Connery]

New LED lights stretching

Typically a 1000w hps se has about 1700umol at source, 4000 is not right, maybe youre thinking of ppfd and not ppf? sorry typo 2000

www.rollitup.org

That "article" is more esoteric non-sense than anything I've ever read on the subject.
There simply is no such thing as "noise" in photosynthesis


View attachment 5105715
Actually it's still absorbed in like ~~80% of all incidents, red & blue fare a bit better.
That chart you see in that article is grossly misleading... :/

this review explains it well:

Importance of the green color, absorption gradient, and spectral absorption of chloroplasts for the radiative energy balance of leaves - Journal of Plant Research

Terrestrial green plants absorb photosynthetically active radiation (PAR; 400–700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar...

link.springer.com

Why so negative? The article you posted says this on the subject:

These facts suggest that terrestrial green plants are fine-tuned to reduce excess energy absorption by photosynthetic pigments rather than to absorb PAR photons efficiently.

The article I linked to offers a theory as to why. After all, there is only excess green energy during the middle of the day and plants have other photomorphogenic responses to avoid strong light at that time, such as petiol angle, leaf cupping and transpiration. Being able to absorb green light at other times would be beneficial.

As @Fardsnarp pointed out, if photosynthesis evolved in water, then blue and green light sensitivity should have given the most benefit – especially if waters were shallower 3.4 billion years ago. Unless, of course, the atmosphere was thicker and sunlight that reached the earth was redder . . .

It still doesn't answer why plants don't use the most abundant spectra. Although my theory is that they actually do: leaves are green because reflected green light is the most efficient way to drive photosynthesis in the lower canopy.

We also know that chloroplast pigments change depending on the type of light a plant gets: leaves tend t be darker under bluer light and yellower under redder light. Again, the abillity to change pigment may explain why cannabis plants selectively grown and bred under HPS continue to perform well under a HPS spectra. In many of the experiments I have seen on other types of plants, the ratio of red/green has had less effect on growth than red/blue.

 

[Prawn Connery]

Oh, I just thought to point out another thing I have witnessed with HPS bulbs.

If you want the most out of your HPS bulb it should naked. Meaning that HPS in an enclosed glass such as a hood or tube did not result in the same growth as a hood without it's glass.

It's a trade off of channeling heated air away vs getting the most from say a Hortilux Eye.

Happy Growing!

When heat is a problem HPS is the wrong decision... and yeah, the glass will swallow some light... and the reflector also a good portion... vertical grows with a free hanging bulb seems to be the killer; esp. with another MH thrown therein

Right on! That's precisely why I grew vertically for so long. There is no lost light – bulbs emit in 360 degrees and if you hang a bulb vertically and surround it with plants, very little light escapes and much of it is used. If you hang it horizontally, you lose 15% or more as soon as it hits the reflector. Cool tubes not only add an extra layer of glass, they get dirty – which is arguably worse.

 

[Friendly_Grower]

It also looks "Garden-Party" Cool in my opinion.

 

[BioScout]

After not being able to grow because of climate change

I am worried about CC too and don't doubt you. But what is the story?

 

[tstick]

When you have a full spectrum white light source and your plants are green, then isn't there more reflected green photons bouncing around the tent than when the plants start to fade and change their colors? And depending on what colors your plants take on over time, doesn't the spectrum change inside the tent just from the corresponding colors of the reflected light? Like, when the plants turn yellow, then there are more reflected yellow photons in the tent...right?

 

[Friendly_Grower]

I am worried about CC too and don't doubt you. But what is the story?

I was very poor and lived in a 20 foot trailer in a low income trailer park for two decades.
20 ish years ago a 1K HPS was considered very good.

I built a 16 SqFt planter bed in the back and made my own organic soil from scratch.
I moved from the Yosemite area down to the central valley to not be driving two hours a day to get to work and down at 190 feet above sea level the temperature moved from being cold enough to grow in the back part of that 20 foot trailer in October to then November, December and finally January.
It started getting too warm in March so that was unsafe to run a 1k HPS and so I quit growing out my feminized seeds I made.

I'm now a Home Owner in Southern Illinois and have my Medical Use permit.

So I experienced climate change in California and it is real.
Honestly, there really isn't much of a Winter there anymore.

In truth California has always been a Desert clime but it's moving that way and I don't think it can come back.
In that part of California it's green in winter and turns brown in spring.
In Illinois it's brown in winter and green in spring.

So, LED is a net positive where I came from and here I can use the cold of winter once again to run HPS which I love as a Craft grower growing my own medical use supply.

Did that answer your question okay? @BioScout

 

[Drop That Sound]

A Glass tube, arc tube and some metal\electrodes are way more environmentally friendly produced than state of the art diodes, circuit boards, and chips. Easy to recycle when compared. Magnetic ballasts can run forever with minimal maintenence, and replacement parts.

Look at the destruction that big tech has done to Cali. Silicon valley is a toxic wasteland.

They cap off and cover up old toxic sites with large new housing developments, and would be bankrupt if everyone knew why they were getting cancer\sickness from the fumes that they cannot seem to control seeping up from the ground.

The world is turning into a landfill of throw away items like LED fixtures\components.

LED lights contribute far more to the overall environmental/climate problem than the energy needed to burn conventional HID bulbs.

Digital HID ballasts aren't any better, but has been a short run overall, and more people are going LED since they came out anyway.

 

[Northeastskier]

 

[calvin.m16]

First off this is a wonderful thread.

For me I feel connected to the "Craft Grower" aspect.
That is where my grow-pride is.

I have a light footprint of four HPS and four COB LEDS with gullwing in the big room.
I have a compact florescent light rack I built that still delivers but it is true I am using the MarsHydro SP3000s in two tents now to facilitate some breeding. They seem to be okay with seedlings leaning in towards center growing at the edges of that LED.

After not being able to grow because of climate change for some years it's all about recreating what I knew and loved.
In the craft sense I like the radiant energy from HPS and sure that can be considered wasted energy use in a watts per gram paradigm but in my belief system it's a little Sunshine to a plant.

Besides I will be piping clean fresh heated air through the hoods into my living space as well come next winter's medical grow afte the proper build out. Waste not want not they say.

It's a enclosed front porch with enclosed grow room and what folks call a lung room where a Co2 burner lives.
The proper build out will happen this summer so if I can answer any questions later on I would be glad to share. We all learn from each other.

So again, in a craft sense radiant energy is part of the environs for my craft grow. A little artificial sunlight.
Remember these are living things. Charles Darwin wrote a wonderful treatise named The ‘root-brain’ hypothesis of Charles and Francis Darwin. We may focus on what Cannabis can do for us but we should also equally invest in what we can do for Cannabis in my opinion.
That is why "My Medical Strain" (MMS for a lack of naming imagination) F2 seed grow 2021-2022 was grown under HPS + LED in Organic Living soil.



LED should continue to evolve and for many it's good enough as it is today.
Again wonderful thread.


Friendly_Grower

It's sunshine to me in the winter too. I walk down and stand under those lights and nothing beats it. I can imagine how the plants "feel" under that.

 

[Kassiopeija]

Why so negative?

Oh I'm not, no worries. But the article you cited is pseudo-science and gets rightfully heavily criticised so. People asking what this non-sense is supposed to mean in the comments...
I still don't see the relevance all of this has with green-light when HPS has next to none of that (my original point....)

The article I linked to offers a theory as to why. After all, there is only excess green energy during the middle of the day

That is not a fair description of the sun's colour change occuring during a day. It is actually blue that will become increasingly "excessive" from mourning to midday which is why plants have more photoprotective compounds available in the blue region than in the green.

Although my theory is that they actually do: leaves are green because reflected green light is the most efficient way to drive photosynthesis in the lower canopy.

"Your theory"? Well good, then we are in agreement because the review I presented you actually prooves that already and the mechanism is explained in great detail. And it cites a boatload of additional references for further study.

Not to say I have read a dozen studies on the very same topic that sheds light to this mechanism in various forms & under different conditions, like high irradiance in-leaf photosynthesis rates, dense canopy light assimilation or how the photosynthetic apparatus undergoes a structural change to optimize the harnessing of the farred & green-enriched shadelight.
I've been making posts on this very subject at RIU for almost a decade now showing diagrams & exemplary pics when growers actually would deny green (or otherwise) "light penetration".
It's actually old news. Photobiological textbooks have these info's for decades.

That's why I know what kind of esoteric mumbo-jumbo I can directly refuse, the arguments against novel claims mount up skyhigh but it would just be a waste of time when reliable peer-reviewed information is the way better route to go

 

[Kassiopeija]

When you have a full spectrum white light source and your plants are green, then isn't there more reflected green photons bouncing around the tent than when the plants start to fade and change their colors? And depending on what colors your plants take on over time, doesn't the spectrum change inside the tent just from the corresponding colors of the reflected light? Like, when the plants turn yellow, then there are more reflected yellow photons in the tent...right?

well, yes it changes... the article in this thread explains it well:

Chlorophyll does not reflect green light – how to correct a misconception

Source: https://www.tandfonline.com/doi/full/10.1080/00219266.2020.1858930 ABSTRACT Plant leaves are green because they contain the green photosynthetic pigments, chlorophylls a and b. Popular science literature, and sometimes even textbooks, state that the greenness is caused by reflection of...

www.rollitup.org

and it also proves that chlorophyll doesn't deflect green photons at all. Other mechanisms at large are actually responsible for that.
But in a growroom with a dense canopy you can expect that +90% of all light is captured by leaves so efficiently are these in their light absorption.

 

[Kassiopeija]

View attachment 5106247

ahaha is - or was - there a HPS growroom in that attic?

the trick is to cover all the walls with double mylar or alu foil, so that the IR doesn't escape & gets absorbed by the wall. Even police nightvision can detect that. The IR in the 800-+1000 range just simply transmits through many materials, incl. leaves, too

 

[calvin.m16]

@Kassiopeija what LED would you recommend for flower in the $1,000 range for a 5x5.