Optimum Light Period

Before running down the path of duration and intensity and modifying anything.........

Back up...............what is it that you want to do with plant growth?
Do you really and honestly want more growth and faster growth rates?
The whole point of reducing light is to reduce growth rates and demand for CO2 and nutrients.

Keep that in mind here.

If you want to increase the rate of growth, then perhaps.............but simply increasing light, or adding a bit more during part of the day is pretty simple and straight forward.

As few aquarist ever do dry weight analysis, you really cannot do much comparing with one light treatment vs another, but you can likely predict the outcomes if all else is equal(rare in most cases, but you might spot some trends as mentioned above, more light = more growth).

"Optimum light" assumes => more growth/faster growth and mostly maximum growth.

I'm not sure folks want that.
The trade off folks seem to tell me and others................... is that they want managed growth, so grow some things in at low stable light, then a bit of fast at max growth, then reduced light to reduce growth once filled in good.

Or have a bit more patience and have a slower growth tank.
Few ever asked for the fastest growth

If a farmer ask for optimum yields, this means the most dry weight harvest. For us it would mean that X plant light treatment has a higher weight/color, pigment, seed production, development etc than say plant treatment Y.

Just be careful is the question asked, ask "what is the real thing I am looking for?".

Regards,
Tom Barr

 

Probably about 40-50micromols seems like a safe bet, you want a little wiggle room and not go to the bone here.

Well, 6-10 hours is the likely range that will help the most. Less than this, things drop off a bit. Depends on the species but in most cases, 8-10 is best for good efficient growth. You do not get the same results from adding 2x as much for 1/2 the time............it does not work that way.............

It can. I think it will depend on many things also though, individual plant species species, reserves the plants in question have built up etc.
I can cover Crypts (no light measured at all) for a month and they do fine if they have access to light outside the cover. They are able to draw and translocate resources.

I think this was more your point/question, but think about algae though.............they need higher light in general, so adding high intensity but shorter time frames does not help there.

But you can get to the point where you start limiting plant growth via duration as well.

But..............I think working on intensity and sticking with 8-10 hours first and getting really well known in that area should be done first.

I have no examples of nice ADA scapes with 2-4-6 hour ranges available to compare with. Do you? Would you spend 10-20K and set them up and win in the top 20 in the ADA contest?

This was low picked fruit, but we already have a good consensus about the duration, yes, it can be manipulated but do you want to go down to the bone there? Plants can and do adapt to intensity pretty good, duration? Much less so and it will be tougher to say anything more than theories...............

8-10 hours ought to do it for most plants.
You can watch and see when they "close up", like Cabomba species, you might argue that that is a sign of enough duration and adding more light is not needed.

This does occur faster at higher intensity light. How much more? Maybe 7 hours vs say 11 if you stretched it to extremes. Maybe more if you went way down on intensity.

As you approach the edge of LCP's whether from duration and intensity or some combo of the 2, you really will have more troubles and issues as many species will have different tolerances. The nice thing about all this that I did, was the fact I had some nice scaped examples with a wide range of plants that I knew of and several replicates , as well as knowing the tanks and the folks's general care and routines. So I did not have to do much work to show the tanks needed little light in terms of intensity. To test what you seek, that's a lot of work and I am not that motivated to do it, you are certainly welcomed to do it however

Regards,
Tom Barr

 

This gives some nice aesthetic value to lighting, my client in LA does this.
I think seeing the long gradual light changes is nice myself.

But measuring it and telling someone some good hard data for all plant species, higher number of replicates etc, nice top placing scapes and their systems is rather tough. I went after the easy to measure and argue low picked fruit with the ADA example for good reason.

I simply had to falsify what some have long been claiming and give a nice scaped examples as well. I did not have to prove the min light or the duration that is optimal or deal with variations in dawn to dusk scenarios

I'm much lazier than many think. It's far easier to falsify a hypothesis folks might have than to prove what something is............

Think about that for awhile.
Seriously...................

If you can falsify it, then you know it's not due to that hypothesis (eg, must have high light) and can move on. That's something you know cannot be right because before you are several examples that clearly show it's not the case!

Showing what is the cause, the limits etc, that's harder.
Requires more work, pushes the limits of specific species tolerances etc.

Regards,
Tom Barr

 

Pretty much, they flower/change their phenology according to light duration(say when it gets to less than 11 hours, many switch gears and produce dormant structures, eg tubers........, some go to seed.

Many however respond to water levels and emeregence for flowering.
Many have hetrophylly(see Sculpthrope for more differences).

We keep the light the same, but can manipulate it.
Generally, all we wnat is vegetative growth, not tubers, seeds etc.

You got it/the concept etc down.

Algae however does the same things and does not grow well in the winter in FW systems. So less than 11 hours etc often causes many species not to grow well.

Less than 10 hours does a number of some species as well.
But plants seem fine to about 7-8 hours.

Depends on if the light is intense.

You can measure the light and the total duration in PAr units as PAr is micromols per meter ^2/sec.

So you can total up the time in seconds X the PAR reading.

This can give you some flex to go longer or shorter and still get the same relative amount of sugar produced by photosynthesis. This has obvious limits, you cannot pack all the light into say 2 hours and try to do very low levels for 20 hours.
You might want to stick around 10 hours and then go one way or the other...........most seem most interested in the shorter durations, so start with 8 hours and then give things 3-4 weeks before changing things, this is a typical time for low light adaptations.

reduce by 30 minute blocks, so to go from 10 hours to 8 might take 4 months, or 8 to 6, another 2 months.

It might work well in some species, bad in others.
Need to make sure it's not CO2/nutrients, pruning, cleaning the filter issues if you get a bad response, if not, then you can assume that the plant is meeting its demand for light.



Regards,
Tom Barr

 

Well, the "how" is still very straight forward and rather simple.
No techy needed.

Regards,
Tom Barr

 

There are some very nice dimmers, but not in the USA.........that can do exactly what folks might want here.

Regards,
Tom Barr