The Importance Of Light Spectrum

[jaypeecee]

I still can't see where there is enough difference between the two light absorption curves?

Hi Darrel,

To which two absorption curves are you referring?

JPC

 

[JoshP12]

Hi all,

Just want to share a story about spectrum ... it is important to consider it.

Consider the following scenario:
1) Turned up my CO2
2) Noticed I overshot it and fish were struggling
3) Shifted my spectrum towards more Red and warm white:
Sacrificed Cool white spectrum for Warm white (oranges and yellow and green) and Red.
Got rid of about 10 % of cool white and it equated to about 15% Dark Red (660nm) more AND maybe about 7% of warm white (the numbers will not add up properly -- I just redistributed it) ... fish began to recover near end of photoperiod (could be lots of reasons why so don't draw crazy conclusions)
4) The next day - no gasping.

It isn't the first time that I tweaked light to help dial in CO2 and it isn't the first time I tweaked spectrum instead of tweaking that CO2 dial.

Just an experience in how I help myself set CO2.

Josh

 

[ceg4048]

You may be correct but what (scientific) evidence do you have to back up your statement? I'd also like to pick up on your word 'triggered'. I don't see it as necessarily 'triggered'. Isn't it a case of orange light at 625nm having the potential to 'feed' cyanobacteria with light of the very wavelength that it is well-equipped to utilize? Red light at around 660nm is needed by plants as it corresponds to one of the absorption/action peaks of chlorophyll a - as I'm sure you are very much aware. So, red light is here to stay. The other chlorophyll a peak is at 430nm give or take a gnat's whisker. This is at the blue end of the spectrum and, according to Dr Bruce Bugbee*, is very much needed but, in his words, 'shrinks plants'.

As Darrel alluded to, and as mentioned in oreo57's post, the problem in interpreting and applying this data is one of magnitude. It's all very easy to get wrapped tightly around the axel about this nanometer, or that response curve. How much does all of that translate to what is in our tank in comparison to the contribution of the wide range of other factors such as CO2, nutrition, genetics, light intensity, flow distribution and so forth?

The best solution is to test this for your self, in real tanks. You first need to have control. Do you have enough control of the tank to be able to detect the differences in growth and health and to be able to attribute those differences to blue alone? Doubtful.

Years ago we played with different bulb types to determine if we could at least subjectively determine a performance differences between various colored bulbs. There was no way we were going to be able isolate specific frequencies using T5s (perhaps it's less of a problem now with LED) so we just used bulbs based on supposed color temperatures and had a look at their published spectral curves.

My blue containing bulb choice was Osram 880. A supposed 8000K bulb. No shrinkage was detected.

In comparison, these bulbs are Osram 840, a supposed 4000K bulb with lots of orange/yellow. No problems either, just lots of exaggerated orange/yellow.

Many others have done similar, searching for the holy grail of spectrum and none of us could determine, subjectively, which bulb color performed best. There were just too many variables. Could it have been done more scientifically? Sure, we could have isolated individual stems in a petrie dish and measured the dry weight after X weeks, but to what end? If the tank conditions were good there was no real overall difference in performance. If problems developed in the tank, such as flow issues or CO2 issues, the symptoms were similar across bulb types. You simply cannot separate effects of wavelength from these other factors. Again, these were not just isolated tests. Various lamp types and bulb combinations have been used over the years and no one could say unequivocally that this wavelength is superior to that other wavelength. It's simply a non-issue in our tanks, regardless of the results of that experiment, because the other factors have effects orders of magnitude above the effects of wavelength.


Cheers,

 

[dw1305]

Hi all,

To which two absorption curves are you referring?

These, from the paper you referenced <"Blue light reduces.....">:

Light absorption spectra of the cyanobacterium Synechocystis sp. PCC 6803 (black line) and the green alga C. sorokiniana 211-8K (grey line) acclimated to 35 µmol photons m−2 s−1 white light.

cheers Darrel

 

[jaypeecee]

Hi @JoshP12 @ceg4048 @dw1305 @oreo57

Many thanks for all your feedback. I plan to do some experiments for myself when time permits. If, and when, time does become available, I'll report back.

JPC

 

[erwin123]

Covering crops in red plastic can boost yields up to 37 per cent

A simple, cheap technology could help to boost food production and possibly allow crops to be grown in different places in order to cut down on food miles

www.newscientist.com

To address these issues, Alexander Soeriyadi and Alexander Falber at the University of New South Wales in Sydney, Australia, developed a material called LLEAF that passively converts some of the green wavelengths in sunlight – which are less important for plant growth – to red ones.
In greenhouse trials, the researchers found that the material increased plant yields by an astonishing amount for various crops, including 37 per cent for pak choi. The material is now being tested in bigger, independent trials run by Western Sydney University and the New South Wales government’s Department of Primary Industries.

David Tissue at Western Sydney University and his colleagues recently completed a trial of the material. They installed it over a greenhouse to cover a 200-square-metre plot of lettuces next to an identical plot of lettuces that wasn’t covered by LLEAF. The yield of cos lettuce, also known as romaine, rose by 14 per cent under the material, while that of butterhead lettuce increased by 27 per cent.

Tissue is now testing LLEAF on cucumbers, with plans for several other crop trials over the next five years. The Department of Primary Industries is trialling it with blueberries, but results aren’t available yet.

One important consideration is whether taking green light from plants and giving them extra red light might harm them, says Tissue. He noticed that lettuces grown under the material had an orange tinge, probably because the altered sunlight changed their composition of carotenoids and other pigments. “But we need to do further research to see if this changes the flavour or nutrition,” he says.

Found this interesting, but rather than create a new thread, I thought it best to add this to the most recent light spectrum thread....

 

[oreo57]

Covering crops in red plastic can boost yields up to 37 per cent

A simple, cheap technology could help to boost food production and possibly allow crops to be grown in different places in order to cut down on food miles

www.newscientist.com

Found this interesting, but rather than create a new thread, I thought it best to add this to the most recent light spectrum thread....

Article being behind a paywall makes it difficult to make any other observations regarding it.

although more research is needed to see if it affects the flavour and nutrition of plants.

Actually important for crop plants.. High intensity or high blue content generally favors flavor and nutrition.
For planted tanks.. not an issue really except for possibly color..

Found this.. Interesting.. seems they are implying using green photons and re-emitting them as red??
As in "flourescence"?
That is a bit cool.
If it's JUST a filter it would decrease PAR
needs clarification..Too much market-speek.

The films are made from special dyes that absorb and diffuse photons from the green spectrum of light, and emit it again as red light to increase plant photosynthesis.
They reduce the amount of light which the plants can’t use, and the diffusion of the light they can is done so more evenly, and in a way as to reduce shadows.

Covering Crops in Red Plastic Can Boost Yields Up to 37 Percent

An Australian ag-startup is discovering that red films atop existing greenhouses can produce more light plants need to photosynthesize.

www.goodnewsnetwork.org

LLEAF 620 is a low-red spectrum color to boost photosynthesis and increase production in most plants, while for aquatic plants, LLEAF 590 is the best choice for applications where light penetration through water for increased growth rate is required.

 

[oreo57]

OK that parts solved.

Covering crops with red plastic can increase yields by 37 percent - Techzle

Image: Pixabay/Geoluro11 A simple, inexpensive trick can boost food production and even make it possible to grow crops in places where they normally don’t grow. Growers can increase the yield of their crops by covering them with a plastic that increases the amount of red light on the plants...

techzle.com

It is a transparent plastic with a fluorescent dye that absorbs green wavelengths and gives it back in the form of red. It can be hung over existing greenhouses. As a result, the light inside the greenhouse turns a soft pink. ‘It’s quite beautiful,’ says Soeriyadi.

 

[dw1305]

Hi all,

If it's JUST a filter it would decrease PAR
needs clarification.

That was what I was thinking. Sun-light is incredibly bright, so even with the inevitable loss from the conversion process it might still offer advantages.

<"Horticultural grow-lights arrays"> are still often "narrow spectrum", so really just red and blue LEDS.

cheers Darrel

 

[erwin123]

Technical — LLEAF

www.lleafgrow.com

This the interesting part though based on the chart, the conversion efficiency is quite low - a significant drop in greens and even blues, and only a slight rise in reds.... nevertheless, it seems that certain crops respond to it. Its being tested by a Aussie Govt agency so it seems legit: Smart Glass and LLEAF: novel spectra-shifting tech to boost energy-efficiency, crop growth and yield under cover

 

[oreo57]

Technical — LLEAF

www.lleafgrow.com

This the interesting part though based on the chart, the conversion efficiency is quite low - a significant drop in greens and even blues, and only a slight rise in reds.... nevertheless, it seems that certain crops respond to it. Its being tested by a Aussie Govt agency so it seems legit: Smart Glass and LLEAF: novel spectra-shifting tech to boost energy-efficiency, crop growth and yield under cover

Chart is relative.. As the blue peak is replaced by red the entire rest of the spectrum is pushed down proportionally.
Not sure one can really say that without a par measurement. May hold, may not.

They should present "before and after" PPFD measurments.
The seem to acknowledge PPFD losses though..

However, as it changes light intensity and spectral quality.......