Fundamentals of Aquatic Lighting

[GlassWalker]

I think topic based FAQs as stickies in the appropriate sub-forum would help a lot.

I've never had much luck with forum based searches. I even get better results using google to search a given forum. Maybe I should search for The Matrix, but then again that might return too many hits!

 

[BigTom]

I have to admit that although this site runs tremendously well generally, the search function can be a bit hit and miss.

 

[roadmaster]

I belong to a couple other forum's where they still spend a dozen or more post's and several paragraphs for each opinion as to what constitutes proper spectrum for plant growth when ever the topic arises.(much of it regurgitated heresay or opinion vigourously defended)
I purchase T8 and T5 bulbs by the case for use in the building I work at as maint eng.
Have expierimented with many different spectrums of these bulbs on my planted affairs and can say that spectrum seem's much ado about nothing when comparison's were made in my tanks.
Intensity/Par are the determining factors in my tanks followed by what looks good to my eyes.
Weed's manage.

 

[ceg4048]

I have to admit that although this site runs tremendously well generally, the search function can be a bit hit and miss.

I think topic based FAQs as stickies in the appropriate sub-forum would help a lot.

Hello,
I agree that we should probably do a better job of "stickying" some threads to make it easier to find.

It's true that there are a couple of limitations to the search function with this software.
The first big miss is that a minimum of 4 characters are required for words so searching, so that a 3 character word search such as "CO2" yields nothing. It might have bee implemented to stop people from searching common words such as "the" or "is" which could tie up the server due to number of occurrences. Powerful engines such as Google have no such limitations.
Another miss is that the engine does not allow exclusion of words, which would be a useful filter.

Lame as it may be, the search function is still a powerful tool if used correctly, so for example here are the search results. It took me 3 minutes to build the search and to execute it. It took me a LOT longer to write about it.:
http://ukaps.org/forum/search/3979746/?q=spectrum&t=post&o=date&g=1&c[title_only]=1&c[node]=50
using the following parameters:
Search phrase = "spectrum"
Search Titles Only Checkbox = checked
Posted by Member = null
Newer Than = null
Search this thread only = unchecked
Search this forum only = unchecked
Display results as threads = checked

You would have easily found the thread that was linked to earlier and a couple more - with additional links.

You can also confine the search to an expression if that expression is entered with quotes such as "excessive light" which returns a different list than if excessive light (without quotes) is entered. Without quotes, the engine returns hits with any of the words instead of only the ones with the the specific phrase.

By default, the "Search this forum only" box is checked, which if not paid attention to, and deselected, will overfilter the search.

Cheers,

 

[ceg4048]

I cannot understand why you say that the light spectrum is unimportant. This challenges everything I've read on the subject. Since the photosynthetic spectrum clearly shows that plants absorb light mostly in the blue and red parts of the spectrum, it makes sense to me that any light needs to ensure significant radiant energy at these wavelengths.

Unfortunately this is another false assumption made by almost everyone, and that is exactly why the comment challenges everything you've read on the subject. What you have read was not written by folks who investigated the specific function of plant pigments. They were told what to think and what to write, so they thought it and then wrote it.

The light harvesting mechanism of plants, algae and some bacteria, such as BGA consists of a central Chlorophyll complex. The complex, has, among many other components, a series of auxiliary pigments which respond to wavelengths of light other than blue and red. The energy captured by these pigments are then passed on to the Chlorophyll and therefore act as a spectral extension of the main Chlorophyll response curve. The leaf analyzes the spectral distribution and fabricates a variety of pigments to perform tasks, such as to reflect wavelengths that have too much energy, to absorb wavelengths that are not primary wavelengths and some pigments are even capable of changing the incident light to another color and reflecting it on to pigments that can then absorb the new color and pass it's energy on to the Chlorophyll.

It's a very sophisticated system and it doesn't need your help. Whatever spectral distribution you provide, the plant will determine how to best use that energy. In this hobby, it actually the opposite of what folks think. There is actually far too much light, that more often than not overwhelms the plants ability to quench the excessive energy.

So there is no demonstration that plants "...absorb light mostly in the blue and red..." It's simply that the Chlorophyll pigment itself has a higher response to blue and red but it depends on the other pigments to absorb the remaining wavelengths and to process those wavelengths. On the contrary, it is specifically because the Chlorophyll pigment has such a high response to blue and red that is is easily overwhelmed by blue and red. So if anything, what the photosynthetic spectrum shows is that you should be using LESS amounts of blue and red to reduce photo-inhibition. This fact has been completely misinterpreted for far too long.

Spectrum loving Klingons are a plague, a pestilence of misinformation on this planet.
We are the cure.....

Cheers,

 

[Andy Thurston]

I've found that if i cant find something using the forum search. Using google and entering the same words followed by ukaps works quite well too, especially when searching for titles with lots of 3 letter words.

Can i use two and three letter words within the quotation marks eg. "Dan and andys crypt" or will the search disregard those too?

 

[ceg4048]

Well I'm pretty sure it will ignore the 3 (or less) words in the phrase and just search for the 4 letter (or more) words in the phrase. That makes the phrase the same as not having quotes.

Regret to say that the Google technique you mentioned would be a better option...sorry....

Cheers,

 

[GlassWalker]

Does the ability to change the wavelength of light in the plant have a name? Sounds a bit like fluorescence, but I'm guessing it has a better name than that

Photo-inhibition isn't something I thought about before either. I guess that raises a new question, how much light is too much? I haven't examined plants I have for their native conditions in the wild. As a rough estimate, I doubt anything we would realistically do on a tank would come anywhere near close to what direct sunlight could produce. Exceptions may include if water were naturally coloured, or if plants prefer shaded conditions.

And finally, I've barely started to unravel the matrix code. Don't make me learn Klingon too. Although it does seem an easier read than some plant biology texts...

 

[X3NiTH]

Does the ability to change the wavelength of light in the plant have a name?

Quantum Mechanics.

Apparently chromophores don't actually change the wavelength of light but are able to utilise the energy via Quantum Mechanics.

 

[tmiravent]

I've been learning (very slowly) important stuff about this hobby in this forum.
What 'Ceg4048' says (writes) were a cold bath for my mind. (i was really convinced the opposite, marketing effects...)
The light questions about the Kº, spectrum, par, and other issues are well discussed here in the forum.
And made some experiments and concluded: 'Ceg4048' is really right!
This, more simple, way to think about light made me save a lot of money!
Color, temperature and spectrum is very important for me (for enjoying my tanks) and now i'm free to choose my light without a headache!

Other very useful advice I've learned: this is not rocket science (read this a few times) . When i have some problem and start to build and solution if it turns too complex is because i'm missing the real point. Then a remember the sentence and try to focus on simple solutions. For me this is just a hobby.

John, trying to answer your question:
(My opinion)
- Light spectrum: very difficult to be objective. If there were a perfect spectrum would be the best for our tank?
I would worry about the final color result of the tank. The best spectrum is the one that fit's you.
- Total light output in PAR. It's already answered, the best way to measure what is important to plants.
- Ability to control light intensity. Not a demand but flexibility is always a must. Can be important if you want to make different setup's with different tech plants. Daybreak, night fall and moon light can be very cool...
- Energy efficiency: for me is a demand! I use only LED, less heat and less cost!
- Colour Rendering Index (CRI): for water tanks i would forget this. The best CRI is our imagination!
- Colour temperature (in °K): very important for me. I use this as basic guide for building the colors in my tanks. (very warm, warm, neutral, cold).

Other considerations:
- shimmer effect, if you like and have some water agitation can be a must (can be achieved with LED)
- Lights with optics, can give dramatic shadows and concentrate the power in a smaller area. (like a led spot with 35º)
- Diffused light can give very soft shadows (like T5 or t8)


cheers

 

[OllieNZ]

Does the ability to change the wavelength of light in the plant have a name? Sounds a bit like fluorescence, but I'm guessing it has a better name than that

Photo-inhibition isn't something I thought about before either. I guess that raises a new question, how much light is too much? I haven't examined plants I have for their native conditions in the wild. As a rough estimate, I doubt anything we would realistically do on a tank would come anywhere near close to what direct sunlight could produce. Exceptions may include if water were naturally coloured, or if plants prefer shaded conditions.

And finally, I've barely started to unravel the matrix code. Don't make me learn Klingon too. Although it does seem an easier read than some plant biology texts...

From the Optimum Aquarium by Kaspar Horst and Horst E. Kipper
(referring to readings taken is Sri Lanka) "The difference in lux was between fifty and ninety thousand lux"
Unfortunately they don't state the time of day they took the readings so the shaded areas receiving only 50 lux may have received more at some point during the day. They also point out that plants growing in the high light areas were in deep water (3.5m) or suffering from algae

 

[ceg4048]

Does the ability to change the wavelength of light in the plant have a name? Sounds a bit like fluorescence, but I'm guessing it has a better name than that

Yes, it's called
Förster Resonance Energy Transfer (FRET)
It's not Florescence at all although it does occur in chromophores which are capable of fluorescence.

Photo-inhibition isn't something I thought about before either. I guess that raises a new question, how much light is too much?

Well it's really difficult to quantify because the amount of energy hitting the leaf starts a chain of events which then requires other components to complete the chain, principally, CO2 and then nutrients. In fact, this is called the Electron Transport Chain. Photosynthesis is a series of Reduction/Oxidation (Redox) reactions whose function is to deliver high energy electrons to strip CO2 of it's Carbon atoms in order to hydrate the Carbon into sugar. This final Carbo-hydration chemical reaction is not possible without the energy of the electrons. If carbon and other nutrients used in the sugar production are not available in sufficient quantities to match the amount of electrons being delivered the electrons which have nowhere to go spew out of control and poison the plant.

So how much light is "too much" has a relative answer and cannot be quantified unilaterally because as you can see, the answer depends on how much CO2 and nutrients the plants have access to. That, in turn, can depend on CO2 dissolution techniques as well as flow/distribution techniques.

A certain amount of PAR in one tank can be fine, but in another tank, the identical amount of PAR can spell disaster. GENERALLY, what we advocate is that when a tank is first setup, the amount of PAR measured at the substrate should be in the neighborhood of 40-50 micromoles. Even so, as I mentioned, this guarantees nothing because CO2 must be excellent, flow/ distribution should be excellent, nutrient dosing should be excellent and maintenance should be excellent. If these items are satisfied then the probability of success is high.

So, as you can see, my point is that there are a LOT more things to worry about and which have a palpable effect on the health of the tank than what color the light bulb is. These factors are SO much more important than worrying about colors borders on the absurd.

I haven't examined plants I have for their native conditions in the wild. As a rough estimate, I doubt anything we would realistically do on a tank would come anywhere near close to what direct sunlight could produce. Exceptions may include if water were naturally coloured, or if plants prefer shaded conditions.

On the open unshaded areas of tropical forests, PAR values are approximately 2000 micromoles at the water's surface, however, the plants exposed to this value are also semi-exposed to atmosphere and therefore have access to CO2. Plants that are fully submerged are usually in murky waters where the PAR levels are a fraction of what it is at the surface. Other submerged plants have access to CO2 from organic sedimentary bacterial respiration or are fed by natural springs high in CO2.

And finally, I've barely started to unravel the matrix code. Don't make me learn Klingon too. Although it does seem an easier read than some plant biology texts...

Klingons are ever present. They are the ones who write most of the things you read in The Matrix.
Be strong.

Cheers,

 

[James O]

Plants had been dealing with light in it's various forms for millions of years before we decided to stuff them into glass boxes with T8/T5/LED's. Despite the various situations they find themselves in they still manage to cover most of our planet....

Bottom line? Plants know more about light than we do.........so trust them

 

[Marcel G]

The leaf analyzes the spectral distribution and fabricates a variety of pigments to perform tasks, such as to reflect wavelengths that have too much energy, to absorb wavelengths that are not primary wavelengths and some pigments are even capable of changing the incident light to another color and reflecting it on to pigments that can then absorb the new color and pass it's energy on to the Chlorophyll.

Just a couple of days ago I studied this issue more deeply, and have found some studies/articles which supports Clive's claims. Here are few of them:
1) http://cpl.usu.edu/files/publications/poster/pub__3801011.pdf
2) http://pcp.oxfordjournals.org/content/50/4/684.full.pdf
3) http://www.ledgrow.eu/LightColor.pdf
It has been found that green leaves can absorb from 50 to 90% of green light! Also the green light has roughly the same quantum yield as the red one.

 

[GlassWalker]

Great links, although I've only scanned through them quickly for now.

 

[tmiravent]

Amazing
So much information...
my brain hurts!
I follow James O advice:
cheers

 

[Tim Harrison]

Haha not this old chestnut AGAIN...

I'm confused cause all the papers linked by ardjuna state that not all wavelengths of photons are equally efficient in driving photosynthesis Doesn't this mean that at least some importance can be ascribed to light quality despite accessory pigments?

I may well have misunderstood, but I'm also confused as to Clive's assertion that there is no demonstration that plants '...absorb light mostly in the blue and red...'. Thomas Engelmann might disagree if he were still alive to do so. Look under the heading "Scientific Investigations" http://en.wikipedia.org/wiki/Theodor_Wilhelm_Engelmann Pretty elegant...huh

I also thought that a spectrophotometer could be used to measure the proportions of light of different wavelengths absorbed and transmitted by a pigment solution to similar effect But I may be wrong about that too, or maybe misunderstood its relevance

And isn't UV light the major cause of photoinhibition (defined as light induced damage) not visible wavelengths; although the latter is also obviously damaging too...especially blue wavelengths? And what about photosystem I - I thought that wasn't very susceptible to photoinhibition And isn't photosystem II damaged by light irrespective of intensity and Klingon's - haven't some studies concluded that low light intensity can be more damaging than high light intensity? And anyway, isn't the rate of damage directly proportional to the rate of repair so that photoinhibition very rarely impacts on plant health?

Those questions asked, maybe one of the reasons that flow and distribution are so important to us as aquatic plant growers is because lack of CO2 and nutrients can decrease the rate of repair and therefore have a negative impact on plant health. Maybe that's the main reason why achieving a balance between the various parameters - especially light - is so important, particularly at the beginning when the system has yet to stabilize...

And maybe it's one of the reasons why spectrum does matter especially with regard to adaptation to resource limitation, and say, the relatively expensive use of accessory pigments, and its subsequent impact on the rate of repair

My favorite quote...

'...Adaptation to resource limitation is a costly affair. Whether the plant invests in more chlorophyll or more enzymes it results in higher nutrient requirements and higher energy use. The higher energy use comes from the fact that proteins require constant maintenance in the cell to work properly and these maintenance processes absorb valuable energy and carbohydrates, which might otherwise be used for growth purposes...'

But obviously this need not necessarily be a problem in our aquariums where most of us go to great lengths to ensure that lack of light quality is compensated by an abundance of other resources, including light quantity.

SPECTRUM RULES

 

[ceg4048]

And isn't UV light the major cause of photoinhibition (defined as light induced damage) not visible wavelengths

Nope, absolutely not. That's just another Klingon argument. Just because UV causes photoinhibition it does not automatically mean that there is little or no effect from the visible light that we provide. Photoinhibition is constantly occurring, even when the lighting is low or moderate. It's the RATE of damage that increases with increasing intensity. Photosystem II takes the most damage specifically because it is extremely sensitive. Blue/Violet has the highest energy, so it does the most damage of the damage caused by visible light. So the plants have to repair the damage to the proteins that get damage by producing new replacement proteins.

Again, it's a really complicated system and so researchers have to be careful about the conclusions they draw. Here is a PubMed abstract ( http://www.ncbi.nlm.nih.gov/pubmed/12232146 ) discussing the recovery of terrestrial pea leaves:

D1 protein turnover and restoration of the photochemical efficiency of photosystem II (PSII) after photoinhibition of pea leaves (Pisum sativum L. cv Greenfeast) acclimated to different light intensities were investigated. All peas acclimated to different light intensities were able to recover from photoinhibition, at least partially, at light intensities far above their growth light irradiance. However, the capacity of pea leaves to recover from photoinhibition under increasing high irradiances was strictly dependent on the light acclimation of the leaves; i.e. the higher the irradiance during growth, the better the capacity of pea leaves to recover from photoinhibition at moderate and high light. In our experimental conditions, mainly D1 protein turnover-dependent recovery was monitored, since in the presence of an inhibitor of chloroplast-encoded protein synthesis, lincomycin, only negligible recovery took place. In darkness, neither the restoration of PSII photochemical efficiency nor any notable degradation of damaged D1 protein took place. In low light, however, good recovery of PSII occurred in all peas acclimated to different light intensities and was accompanied by fast degradation of the D1 protein. The rate of degradation of the D1 protein was estimated to be 3 to 4 times faster in photoinhibited leaves than in nonphotoinhibited leaves under the recovery conditions of 50 [mu]mol of photons m-2 s-1. In moderate light of 400 [mu]mol of photons m-2 s-1, the photoinhibited low-light peas were not able to increase further the rate of D1 protein degradation above that observed in nonphotoinhibited leaves, nor was the restoration of PSII function possible. On the other hand, photoinhibited high-light leaves were able to increase the rate of D1 protein degradation above that of nonphotoinhibited leaves even in moderate and high light, ensuring at least partial restoration of PSII function. We conclude that the capacity of photoinhibited leaves to restore PSII function at different irradiances was directly related to the capacity of the leaves to degrade damaged D1 protein under the recovery conditions.

So basically what this is saying is that leaves that were originally grown in LOW light and then pummeled with high light do not recover and repair the photoinhibitive damage as easily as leaves that were originally grown in HIGH light. This makes perfect sense to me, because the high light leaves already have developed a tolerance for high light so they can recover more easily from damage done to them at higher recovery light levels than the leaves that are accustomed to low light. People misinterpret this and draw the erroneous conclusion that "low light intensity can be more damaging than high light intensity?".

I thought that wasn't very susceptible to photoinhibition

It's not as susceptible to damage due to light because it is not as sensitive to light.

isn't the rate of damage directly proportional to the rate of repair so that photoinhibition very rarely impacts on plant health?

No, because the rate of repair is inversely proportional to the light intensity. The rate of damage is directly proportiona to the PAR intensity.

And maybe it's one of the reasons why spectrum does matter especially with regard to adaptation to resource limitation, and say, the relatively expensive use of accessory pigments, and its subsequent impact on the rate of repair

Again, no, because the total damage being done is related to the PAR intensity. Whatever proportion of damage is due to specific wavelengths you are not going to be able to control that anyway - but you can easily control the PAR, then you really don't need to worry about which wavelengths are causing more damage than others.

I'm confused cause all the papers linked by ardjuna state that not all wavelengths of photons are equally efficient in driving photosynthesis Doesn't this mean that at least some importance can be ascribed to light quality despite accessory pigments?

As we mentioned ad nauseum, yes, there is some importance, but the magnitude of that importance is so small compared to the importance of other factors that for our purposes it becomes completely irrelevant. You will never solve any problem in your tank by changing the color of your bulbs and you will never see a difference in plant health or growth rate from one bulb to another. If that's not good enough for people then it means they prefer living in a dream world, which is exactly what The Matrix was created to do.

Cheers,

 

[Tim Harrison]

Hmmm...Clive I've decided that you're an Agent of the Matrix...a false profit attempting to divert us from the real Parousia. The real path to enlightenment lies with the acceptance that spectrum does matter - no matter how small or insignificant you consider it's influence in the context of our aquariums, and I think you've unintentionally confused the issue with all this photoinhibition malarky...

...Thomas Englemann must be spinning in his grave...

 

[James O]

From this I take:

'rate of repair is inversely proportional to the light intensity. The rate of damage is directly proportional to the PAR intensity'

'Whatever proportion of damage is due to specific wavelengths you are not going to be able to control that anyway - but you can easily control the PAR, then you really don't need to worry about which wavelengths are causing more damage than others'

As we can't control the nm spectrum each bulb/LED produces we are stuck with controlling intensity (PAR). Even if we could, you would still have spill of various spectrums of light available from other bulbs for other plants, daylight from the window and room lighting.

I think in the real world of my tank, where plants are not grown as isolated specimens under specific lights, the amount of light is more important than the colour