# [Wet Thumb Forum]-Light intensity and Internode growth



## JamesHoftiezer (Feb 2, 2003)

I recently bought some rotala indica from the store. Not because I didn't have enough but becuase it had a very tight internodal growth. My r.indica has a nodal length of almost an inch. The purchased plants had a node distance under 1/4".

One of the maintenenace headaches I have it the minimal time it takes for stem plants to grow to the top of the water. With my light (330w) and ferts I can trim some stems and have 3-5" of growth each week. I have tried changing light periods and ferts, but it only see3ms to affect their health, not the growth (in a very general statement)

One visual rule of intensity I am familiar with is glosso. In my tank (36x24x25) the glosso stays fairly compact at 3/4"-1" and grows a light green.

*Here's the question?*
At 3.3wpg I have excellent growth, but in order to acheive a more managable aquascape and more compact growth should I increase the lighting or change the type of lighting?

I am about to rebuild my hood and may add a 250w MH. I may add just; 
add it (5.8wpg) and use it on a limited cycle
or
replace 110w of my PC with the 250 (4.7wpg).

The reason I pose this question is I do not want additional growth (I'd be pruning daily), I actually want to compact the growth I already have.

*James Hoftiezer

Tank Journal - Aquascape ( Latest / Archive )
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## JamesHoftiezer (Feb 2, 2003)

I recently bought some rotala indica from the store. Not because I didn't have enough but becuase it had a very tight internodal growth. My r.indica has a nodal length of almost an inch. The purchased plants had a node distance under 1/4".

One of the maintenenace headaches I have it the minimal time it takes for stem plants to grow to the top of the water. With my light (330w) and ferts I can trim some stems and have 3-5" of growth each week. I have tried changing light periods and ferts, but it only see3ms to affect their health, not the growth (in a very general statement)

One visual rule of intensity I am familiar with is glosso. In my tank (36x24x25) the glosso stays fairly compact at 3/4"-1" and grows a light green.

*Here's the question?*
At 3.3wpg I have excellent growth, but in order to acheive a more managable aquascape and more compact growth should I increase the lighting or change the type of lighting?

I am about to rebuild my hood and may add a 250w MH. I may add just; 
add it (5.8wpg) and use it on a limited cycle
or
replace 110w of my PC with the 250 (4.7wpg).

The reason I pose this question is I do not want additional growth (I'd be pruning daily), I actually want to compact the growth I already have.

*James Hoftiezer

Tank Journal - Aquascape ( Latest / Archive )
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## Vicki (Jan 31, 2003)

Well, for the most part, Iâd say youâre stuck with the pruning job, James. More light will shorten up the internodes on many stem plants, but it doesnât really keep them from leaping to the top of the tank; you still have to keep after them to maintain the height you want. You certainly donât need more light for your rotala; it will grow with nice tight internodes under much less light than you already have.

http://www.wheelpost.com


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## Guest (Apr 25, 2003)

James,

We had similar topic way back on old forum. I know that strong supporters of this idea are 2la and Steve Hampton. They were "first" on our forum to conclude that 9325K GE Aqua Rays bulbs promote more compact growth, shorter nodes with "bushier effect". I know Ghori is using All-Glass CF 110W with the standard fixture bulbs which are GE AR 9325 and he has the same philosophy as for as Kelvin level vs. growth.

I spoke to Dr. Prescott from FishVet and he was also satisfied with those bulbs vs. compact growth. I belive he also discussed this with 2la since he mentioned to me that he spoke with someone from Portland with funny name (2la ?).

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## JamesHoftiezer (Feb 2, 2003)

Then I need to start topping the rotala to keep get the tighter nodes? Pruning the tops should lead to bushier growth, but I haven't wanted to do it until now because I was cutting off the color. I have been replanting the tops.

Would the same apply to ludwigia?

*James Hoftiezer

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## JamesHoftiezer (Feb 2, 2003)

Right now I am using 2x55wx5300k and 4x55wx6400k. 
Maybe get two 10k instead of the 5300k. Someone has some dayactinic bulbs for $9. Would they serve the purpose?

*James Hoftiezer

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## Vicki (Jan 31, 2003)

Iâll second the nice compact internodal growth one gets with Aqua-Rays; Iâve been using the NO bulbs for years and the pcâs since they came out. Rotala rotundifolia seems to be particularly fond of that bulb. Iâve been digging up my rotala, cutting off the tops and discarding the bottoms for years. For the most part, I have grown it under lower light conditions, and Iâve never cared for the kind of growth I get from the bottoms if theyâre left in place. Iâve been topping the same plants for over four years, and still get nice tight internodes.

Ludwigiaâs another story; generally it will be much bushier and branch a good deal more if you simply prune the tops. Replanted tops always seem to be very slow to recoverâalthough they WILL recover. At some point, you may have to dig up and replant, but as long as enough light is getting to the lower part of the stems you can keep it going for quite a while just by pinching off top branches.

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## Cavan Allen (Jul 22, 2004)

Have you considered temperature James? I've found that it's easier for me to keep things growing more compactly when the temperature doesn't get too high. That's purely anecdotal evidence, mind you, but I think temp definitely does have something to do with it.


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## JamesHoftiezer (Feb 2, 2003)

I've been trying to get the tank cooloer for general health, but I hadn't considered it for the internode growth. Its soemthing else to look at.

Still trying to find a source for PC aqua rays. I finally found the T-tubes, but still looking for any 9325K. Any sources?

*James Hoftiezer

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## Vicki (Jan 31, 2003)

Foster & Smith and That Pet Place both carry them, but you have to hunt for them; they're usually listed in the catalogue where the All-Glass PC tops are. Last time I checked, they were $27.99 at That Pet Place, and $34.99 (!) at Foster & Smith. Foster & Smith carries the full line of Aqua-Ray NO fluorescents, too--those are really cheap; I use them in some smaller, low-tech tanks.

http://www.wheelpost.com


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## Robert Hudson (Feb 5, 2004)

When did "Dr. Prescott" become an expert on plants or lighting?







Brighter light will only make the plants grow faster, specially Rotala indica. Indica reacts to light pretty quickly, it is a fast growing plant.

How are you pruning the plant? I found if you always re-plant the tops, the original growth stays thicker, more dense, and bigger. New growth from a cut stem produces thinner stems, smaller leaves, and larger gaps.

Every plant is somewhat different, but I have never found brighter light to produce compact growth on any plant, just the opposite. Cryps for example: cryp wendtii under bright light for me always gets taller and more elongated shaped leaves. Lower light gets shorter, wider leaves.

But in your situation, I agree with Vicki. If Rotala is healthy, its going to grow fast and reach the surface in no time. Nothing you can do about that

Robert
King admin
www.aquabotanic.com


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## Robert Hudson (Feb 5, 2004)

I would agree that temp could play a big role with certain plants. I keep my tanks at 75, (well in the winter anyway) and I keep some plants at room temp. Plants such as didiplis, Cabomba, ludwigia and Bacopa I keep in unheated water before I sell them. I found they do very well this way. Never tried Rotala indica at room temp in the winter, (65 to 70)

James, are you getting hot weather already? Its still mostly in the 60s here.

Robert
King admin
www.aquabotanic.com


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## tsunami06 (Feb 6, 2003)

James,

On the APD, it was discussed that lighting
had very little to do with internodal length.
If you remember aspiringAmano, he had a relatively low light 55 gallon with the 
most compact Limnophila sessiliflora I've
seen in pictures (and apparently most of SFBAAPS in person!).
It was discussed on the APD that higher
PO4 (~0.8-1.0 ppm) and lower nitrate (1-5 ppm),
would give you more compact growth. Perhaps
higher K+ is a factor, too.
I can tell you that after _removing_
110 watts of PC lighting off my 55 gallon,
my Ludwigias and Bacopa have shown shorter
internodal distances. The distance is less than
1/4th of an inch! So it's not the light
intensity.
A local here has a high PO4 to NO3 ratio.
Whenever I see his plants, I think "robust." 
I didn't have GE Aquarays in my tank long
enough to see if the internodes got any shorter. The color rendition was so bad I
swapped them for Tritons. Basically the same, but much better color rendition.

Carlos


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## Vicki (Jan 31, 2003)

Guess that's a matter of personal taste, Carlos; I love the look of the AquaRays. I mix them with 6700s over my 120, and find that very pleasing--but I have them alone over two smaller tanks. It makes a difference what kinds of plants and fish you have, I think, as to whether or not they look good. I tried them over my 55 and didn't like them at all--the fish in that tank are predominantly yellow, orange and gold, and the plants are green and bronze--and they looked awful! But over the bleeding hearts and the rummynoses,in a tank with lots of red plants,they look gorgeous.

http://www.wheelpost.com


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## Guest (Apr 25, 2003)

> quote:
> 
> Originally posted by Robert H:
> When did "Dr. Prescott" become an expert on plants or lighting?


Ooooo Robert. Are you putting the guy down ?. I met him one time at our annual auction and he sounded like a descent guy. That was good few years back though. I think I told you to squash East Coast competition







.

As for as Aqua Rays.

This was an opinion not a fact. Maybe it is not 100% true but I'm still not satisfied with any of your opinions to make me belive that this perticular bulb has not effect on nodes growth.

Here is an example:

I started my 55G tank with:

- 2 x Philips Daylight Deluxe 6500K
- 2 x GE Chroma 50 5000K

Hygrophila polysperma, Ludwigia Repens were growing like crazy. I was prunning twice a week to keep things under control. ALthough growth was unbelivable, nodes were ~2" apart or sometimes even more.

Here is the picture how my tank looked like when using bulbs above.










After discussion with 2la and Steve Hampton I decided to give this bulb (9325K) a try and I was amazed with the outcome. My H. Polysperma had ~.5" nodes and Ludwigia was very compact. Plants stayed down with more bushier effect. They stayed healthy as before but I was prunning only once or every other week.

Here is the picture of Ludwigia Repens after new bulb was introduced.










I hope either 2la, Stever or Ghori share their views on this subject.

Join as at www.njas.net


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## 2la (Feb 3, 2003)

> quote:
> 
> When did "Dr. Prescott" become an expert on plants or lighting?


Have you _seen_ his plants? I'd believe him!



> quote:
> 
> Indica reacts to light pretty quickly, it is a fast growing plant.


Indica is one of those plants that heads straight for heaven. IME, increasing the lighting will only encourage shorter internode length, but the growth rate will remain the same or increase, as Robert says.



> quote:
> 
> Every plant is somewhat different, but I have never found brighter light to produce compact growth on any plant, just the opposite. Cryps for example: cryp wendtii under bright light for me always gets taller and more elongated shaped leaves.


I've found the exact opposite of Robert's experience to be true of wendtii. At one time I was running 60W over my 40G, and I was growing wendtii as tall as my Amazon swords (i.e., to the top of the tank). When I switched to 120W and CO2 ejection, I couldn't get it to grow taller than about 7 inches max. Others locally have noticed the same correlation in some of their tanks as well, and one of them regularly brings in her over-foot-tall brown wendtii in to the LFS for store credit. She grows them under lower light intensities. Likewise, both Hygrophila difformis and Hemianthus micranthemoides produce more compact growth under higher light; under lower light, both seem to be encouraged to 'reach' for the light by growing upward while producing longer internodes.



> quote:
> 
> But in your situation, I agree with Vicki. If Rotala is healthy, its going to grow fast and reach the surface in no time. Nothing you can do about that.


And I'll add my agreement here, too: That's just how R. indica grows. I think, however, we mustn't assume that all plant species respond to the various light and nutrient parameters in the same way. Some will grow more compactly under higher light, while others will just grow faster. And I'll endorse Dr. Jay's accurate recount of my experience with the GE Aqua Rays Fresh & Saltwater bulbs. My plants don't grow nearly as fast as my friend with a similar 40G setup but employing daylight bulbs, by my internodal length is noticeably reduced, and the colors of my fish and plants stand out better.

Dude with the funny name










[This message was edited by 2la on Fri April 25 2003 at 08:09 PM.]

[This message was edited by 2la on Fri April 25 2003 at 08:11 PM.]

[This message was edited by 2la on Fri April 25 2003 at 08:12 PM.]


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## 2la (Feb 3, 2003)

> quote:
> 
> I can tell you that after _removing_
> 110 watts of PC lighting off my 55 gallon,
> ...


Carlos, I think you're mistaking the short-internode encouraging effect of high lighting intensity versus that of low lighting intensity. The former is a reaction to an abundance of the raw materials needed for growth. Some plants will use it to put out more leaves and shorter stems between the leaves, while others will invest that energy more into producing longer stems.

The latter effect is a reaction to _reduced_ amounts of available raw materials such that plant growth is slowed. Relatively speaking, plant growth is stunted.


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## tsunami06 (Feb 6, 2003)

2la,

That wouldn't make any sense. Why is my
Ludwigia repens and Bacopa caroliniana
bigger than ever? The Ludwigia is 2-3 inches
across and bright red! Same with Rotala
wallichii, it is two inches wide and brighter red than with the extra 110 watt PCs. I enjoy testing plants in this tank with only 1.75 w/g and watch them grow so well. I honestly
thought I could only grow low light plants
at this light level. These are among
the healthiest plants I've grown.

I believe that at lower light levels (within reason), plants have a better chance for assimilating nutrients, thus producing shorter internodes and better color. 

Back to James's topic, I am not recommending
for him to lower the light level but I do not
think that raising light levels any higher
will get him the shorter internodes he's looking for. Just look at Birgit's tanks. Her Rotala indica has very short internodes with only 2.16 w/g NO Flos. Is it really just light
intensity?

Carlos


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## Steve Hampton (Feb 13, 2004)

As mentioned, I am a fan of the AquaRays Freshwater and Saltwater 9325K bulb too. I give full credit to 2la for convincing me...not by his words, but looking at his plants. Without changing any other controllable variables I replaced some of my 5000K to 6700K bulbs with the 9325K bulbs. The difference was obvious and hard to deny.

What always seems to surprise me is the commonalities. Meaning Dr. Jay in New Jersy, Vicki in Kentucky, Tula in Oregon, me in Florida...even though we have very differing water, we still report very similar results. My repeating the same results would serve no purpose...I'll just say ditto to Vicki, Tula, and Dr. Jay. While there is no denying that many differences for individual plants exist and certain situations won't conform to the norm it sometimes is more than just coincidental that certain "techniques" work.

I've tried to "suggest" on various forums and newsgroups in the past to give the higher K lighting a try. Most report a noticeable decrease of internodal length, a few have hurled insults. Form my limited knowledge it does seem to defy most of the experts opinions on what "should" happen. One of the reasons I love this hobby so much is how many times we find ourselves or someone else who goes against the norm and produces fantastic results.

I have little doubt that we could compile a good bit of supporting scientific evidence and jargon to impress people, but it really always boils down to something basic, try it and see if given your unique situation it helps...in the end that's really all that matters.

[This message was edited by Steve Hampton on Fri April 25 2003 at 11:48 PM.]


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## Cavan Allen (Jul 22, 2004)

I've heard that more blue light will keep things bushier, so that could be it.

Before I got rid of it, I had M. tuberculatum that was growing a _very_ compact 2-3 inches a day (no kidding) under power compact and T8 lighting, 75-76F, and about 5ppm nitrate.









I have a friend who has tried growing Limnophila indica under halides and low nitrates, but his temperature is in the low 80's. Leggy so far. Make of that what you will.


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## 2la (Feb 3, 2003)

> quote:
> 
> Originally posted by tsunami06:
> 2la,
> ...


Yes, you've got me there. I should have mentioned a third possible reaction--one that doesn't occur with any of the plant species I keep so I neglected to mention it--but that's to produce larger leaves to catch more light. The trade-off is that growth of the internodes is sacrificed for growth of the leaves, but in this case that's very much a desired effect. And to reiterate, different plant species respond differently to various environmental factors.



> quote:
> 
> Back to James's topic, I am not recommending
> for him to lower the light level but I do not
> ...


How noticeable the reduction in internode length depends on where the starting point is. In James's case, he already has very high lighting, so upping it further will produce only a marginal decrease in internode length--so marginal as to be almost unnoticeable. But you are concentrating on what amounts to a sidenote rather than the main point of my statement, which was that increasing lighting will have an effect _more_ on growth rate, with a reduction in internode length being secondary. Here, too, we might also distinguish between a reduction in internode length per se and compact growth per se. The latter term in my mind also encompasses horizontal growth with the production of many offshoots, not just shorter internode length. If lighting intensity is high enough, many stem plants will tend to grow diagonally or even sidewise, sending offshoots up from many points along the leaning stem. In the case of R. indica, which greatly prefers a vertical growth pattern until it starts to reach the surface of the water, theoretically it would take a LOT of light to do this, and I can't say I've noticed R. indica responding in the same manner that wisteria or pearlweed does.

As for the reference to Birgit's tanks, I think you're mistaking my relative statements for absolute ones. Higher light generally equals shorter internodes, but that does not preclude lower light from being able to produce short internodes as well. The relationship entails a spectrum, and IME it is not a linear one. Within a certain 'comfort range' of lighting levels (say, 2-3+ watts per gallon), R. indica's internodal length is not noticeably different. But head off in either extreme (especially with very low light), you'll be more likely to notice a change in internode length as it relates to the lighting intensity.


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## JamesHoftiezer (Feb 2, 2003)

OK, this is the difficult part of the hobby









I have finally the existence of AquaRay 55w PCs but no actual order yet. www.ThatPetPlace.com is due to have some on 05/05 for $27. As soon as I can, I'll get some.

I'll try higher phosphates for a while. I am already at low nitrates.

Plans for additional lights have been scrapped, but I will be replacing the two 5300k bulbs with 2 9325k. I'll also have the 4 6400k. I might also mix 2,2&2.

I alrady do top-n-plant for the indica. I'm also going to see what happens to the new plants I have with the short internode growth already.

*James Hoftiezer

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## Vicki (Jan 31, 2003)

> quote:
> 
> I've tried to "suggest" on various forums and newsgroups in the past to give the higher K lighting a try. Most report a noticeable decrease of internodal length, a few have hurled insults. Form my limited knowledge it does seem to defy most of the experts opinions on what "should" happen. One of the reasons I love this hobby so much is how many times we find ourselves or someone else who goes against the norm and produces fantastic results.


Couldn't agree more, that's what makes it fun! You know, I think at least some of the resistance to the Aqua-Ray is that All-Glass has used it as their standard bulb for years. I'll confess to the same kind of snobby attitude myself--in the beginning, when I got my first dual All-Glass top for my first serious planted tank, the first thing I did was replace the NO Aqua-Rays with Coralife Tri-Chromatics. I just assumed that it if it came with the hood, it COULDN'T be any good, I never even gave them a try until I got my NEXT hood for my next tank. I was too broke to get new bulbs at that point, and I left the Aqua-Rays in there, and it was at that point that the growth of the plants in that tank REALLY got my attention! I only had dual strips then--and I moved giant hygro and rotala from my 55 gallon, which wasn't as deep as the 45 I moved it to--and was amazed at how more vigorously they grew and how much better the rotala's color was. I've been using them ever since then, and when they came out with the pc 9325 I tried it, and discovered it had the same effect as the NOs did. Some people just don't like the color rendering, and that's fine--that's a very individual matter anyway. All I know is that they work for me.

http://www.wheelpost.com


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## Paulo Pinheiro (Feb 11, 2003)

Hi guys!

I will once again post my opinion based on my long gone plant physiology classes.

As many of you probably know, blue light is the most energetic wavelenght that plants can use. When caught by the apropriate phytochrome (don't remember the name anymore...) it generates energy by producing electrons which are the used for energy production through NADPH. This process leads also to the emission of red fluorescence, which is recovered by another phytochrome.

Plants can perceive the quality of the light they are getting by the amount of energy they can withdraw from it. So if a plant is geting a lot of red light it can only use the second photossystem to produce energy and this energy will be much less than that produced if blue light was available. So the plant will respond with growth in height because blue light is also the one that gets more easily retained by other plants causing shade, trying to reach for more blue light.

On the other hand if the plant has enough blue light it will tend to stay where it is and use the energy more efficiently (branching to have more surface to capture light) and avoiding exagerate growth that could expose it to very high levels of radiant energy, under which photoinhibition would probably occour.

I use one phillips aquarelle bulb in my 65 gal combined with one 3000K and two 6500K daylight bulbs. When I replaced the 10.000K due to algae problems, for one 5300K CRI 95 the plants started dying on me... Someone once said in a post, probably not here that this 5300K has very little PAR (photossinthetically active radiation). The most efficient PAR is definetly blue + red and many bulbs lack one or the other, that why I went with a combination.

Paulo Pinheiro.

Forgot to say... these phillips aquarelle bulbs (10.000K) are only 8 â¬ each and the others only 4 â¬ each, so they come pretty cheap.

Allen's rule: when everything fails read the instructions!!!


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## imported_molahs4 (Feb 3, 2003)

I just uncovered this old thread while looking for answers to my internode problem. I have 3.66 wpg, CO2, and fertilize twice a week. I gave some Limnophila sessiliflora to a friend with about 1 wpg and never fertilizes. In my tank they are leggy, in his tank they are dense, bushy, and lush. I have a similar problem with several other stem plants.

James, did you notice shorter internodes when you moved to the lights with a higher K? Is this really the solution to my problem?

-Scott
tank specs and bad pictures


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## Cavan Allen (Jul 22, 2004)

What is the temperature in your tank?


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## imported_molahs4 (Feb 3, 2003)

The temp is about 77 degrees.

-Scott
tank specs and bad pictures


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## JamesHoftiezer (Feb 2, 2003)

This really is just about rate of growth. I've now seen this in several different tanks and plants. The higer light/ferts generate faster growing plants with longer lengths between internodes. In low light/ferts they get bushier and show better, but will lack the brighter colors (golds, reds)

*James Hoftiezer
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## Cavan Allen (Jul 22, 2004)

Not necessarily. I've been able to get compact growth in high light. Lower temps and low nitrates seem to help that. As I noted in an earlier post in this thread, I had M. tuberculatum growing 2-3 compact inches _every day_. There is more to it than just growth speed. But, it would probably be easier to get compact growth in a lower growth tank.


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## 2la (Feb 3, 2003)

Anyone growing Hydrotriche hottoniiflora, Ludwigia inclinata, Limnophila sessiliflora, or Eusteralis stellata (finally found the trick to growing this plant, and it was simple: MORE LIGHT!) in relatively high light? Ever notice how the internodes are longer towards the bottom and shorter towards the tops, despite the increase in growth rate the closer they get to the light?

Conversely, anyone with 3wpg or more able to get their wisteria to grow upwards rather than sideways, and with long internodes rather than short ones?

I'm with Cavan on this one: It's really species-specific how plants respond to increased lighting, but IME the growth-rate theory doesn't hold true for all or even most plants. Just as plants vary across species with how they respond to certain levels of light, IME there also tends to be a nonlinear relationship between a single plant's growth rate and internode length and the amount of lighting overhead. For example, I can stick some nonspecific plant stems into a 1.5wpg setup, and they'll just kind of sit there, growing very slowly with short internodes. Bump it up to 2.5wpg, and they'll grow faster with longer internodes. Get the lighting up to 3.5wpg, and the growth rate continues to increase (remembering to measure it in terms of plant mass rather than plant height) while the internodes shorten, leading to more compact growth despite an increased rate of growth.

_____


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## Gomer (Feb 2, 2004)

I have R.Indica in my 10g andin my 29g and they both have very different conditions
Both get the same ferts though.

Imy 29g, I have 3.8wpg PC (5000/6700 AH supply mix). The temp is on average around 80 (78-83). 
My 10g I also have 3.8wpg with a pair of 19watt spiral compacts (6500) from home depot, coupled with my very efficent DIY reflector (..not sure what the effective WPG is when you factor in geometry and the reflector)

In the 29g, the nodes at the top are short, but at the bottom of the plant (~ 1/4"), but get larger the further down you go (~ 3/4"). They also grow pretty fast in the tank and are in the middle of the light

In the 10g, I get ~ 50% less elongation at the bottom of the stems. They are in a much more shadowed section (corner and behind driftwood).
I also have some Lrepens in the 10g. I have a group with MUCH tighter nodes from the plants on the very edgeof the tank where light is lower. Still get redish tops, but much tighter nodes than in the more central and better lit leaves.
So...with both those two bits of info, I'd say that it is lighting that has the big impact on nodal growth.


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## Shane A smith (Jun 15, 2003)

Alright, from what i hear, The Kelvin of light plays a huge role in how short/long a plant of the same specie grows. The Kelvin will even decide what colors the plant chooses to put forth. According to my source the lower kelvin triggers the Xanosylins (Sp?) and the higher Kelvin triggers the Chloraphils (Sp?). I may be crazy wrong here but i think thats what he told me. Higher Kelvin also gets the plants to be more Purple if thats the plants tendancy. I zoned out pretty bad halfway through the conversation. Anyhow my point is in my opinion, its not worth sacrificing the color of the plant to get a little bit more compact growth. Also the bluer the light indeed the more compact growth will be. For the reasons given before. Hope this will help.

50gal 160wpg PC 6500k Clay Substrate.


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## Overfloater (Apr 2, 2004)

I have resurrected this thread because it's a very import issue, and very intersting.

From what I have been reading the blue and red spectrum of light are most *readily* absorbed by plants, _however_, light intensity is more important than spectrum because plants can absorb all wavelengths of visible light. Therefore providing strong light at a sufficient duration is more important than providing light in the "perfect" spectrum.

Now that said, I am curious as to how spectrum can affect plant growth. I have heard that light strong in the blue spectrum produces compact bushy growth while light strong in the red spectrum produces longer stem growth and hence, internodes. A combination of these colors is is preferred with spectrum weighted more towards the blue end. Does anyone have any practical experience using bulbs strong in a particular spectrum and their results?

Bob

Los Dios De Verde

[This message was edited by Godslayer on Wed January 14 2004 at 04:26 PM.]


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## Gomer (Feb 2, 2004)

> quote:
> 
> Originally posted by Godslayer:
> From what I have been reading the blue and red spectrum of light are most _readily_ absorbed by plants, _however_, light intensity is more important than spectrum because plants can absorb all wavelengths of visible light. Therefore providing strong light at a sufficient duration is more important than providing light in the "perfect" spectrum.
> ...


I think I am going to have to dissagree with this. Below is the aborption spectrum of the 2 types of chlorophyll in plants. Keep in mind that Absortion is -log(transmittance) ..ie, the small absorbtion features are "exaggerated" relative to the large features. This means that that area between blue and red is pretty much useless. Recall that the color of the plant is the color it reflects (ie, not absorbed).


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## Overfloater (Apr 2, 2004)

Gomer... good stuff. Let me edit what I said earlier. While plants can absorb all light of the visible spectrum due to accessory pigments they absorb the vast majority of light in the blue and red areas, as your chart shows.

Bob

Los Dios De Verde


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## MarcinB (Apr 16, 2004)

> quote:
> 
> Originally posted by Gomer:
> This means that that area between blue and red is pretty much useless.


The green/yellow light is not so bad Gomer. Take a look at this article. Find the photosynthesis action spectrum of the Anacharis sp. and compare it to the chlorophyll a absorption spectrum. Notice the difference. As you can see plants can photosynthetise under those "useless" wavelenghts.

150L (40G) planted tank
click here for photo
Rate my tank!


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## Gomer (Feb 2, 2004)

I stand corrected...partially







I think a more revamped statement would be that while green and yellow can be used due to the absorption peak widths, it is not nearly as effective as red and blue.

Sounds better? or how would you rephrase?


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## MarcinB (Apr 16, 2004)

It's not only about chlorophyll, plants have also so-called accessory pigments which transfer absorbed energy to the chlorophyll. Take a look at that graph again. Chlorophyll absorbtion at 475nm is very low, but plant photosynthetise quite efficiently under such light. Photosynthesis rate is definitely much slower in the 500-600nm range but the difference is not as huge as the chlorophyll absorbtion spectrum implies.

150L (40G) planted tank
click here for photo
Rate my tank!


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## fc (Mar 19, 2004)

James Hoftiezer,

I hope you are looking at this post. May I know if you any conclusions on how internodes can be shortened after all the pointers from fellow hobbyists?

Thank you in advance.


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