Maximum Photoperiod Plants will Utilize - Page 2 - The Planted Tank Forum
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post #16 of 21 (permalink) Old 09-12-2020, 03:57 AM
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Quote:
Originally Posted by Tiger15 View Post
Getting burnt means that the plant is damaged by high light. I know immersed grown Java fern and Anubias in green house need sun screen protection, and shade loving terrestrial plants like Hostas can get burnt under full sun.

But submerged grown plants have water protection so it is not the same. According to Jeffcroll chart, when light reaches the saturation point of a plant, growth will plateau out, not implying burnt out.

https://1gt3sd9flvb3kwgha3wmyhbu-wpe...s-1024x706.jpg

Has anyone experienced low light plants get burnt out by high light under water?

Quote:
when light reaches the saturation point of a plant, growth will plateau out, not implying burnt out.
Right but what is the cause of the slowdown? Lack of say CO2 or a nutrient? Or more uncontrollable factors such as the rise of toxic O2, enzyme shortage ect.
Sadly it's all sort of co-mingled.


Really got to keep in mind "high light" in an aquarium can be like 100PAR.. High light outdoors or in a greenhouse can be 750-2000 PAR.
Not to mention outdoors has a ton of damaging UV and baking IR..

Sooo oddly our "high light" is low light to terrestrials.
And spectrum is "softer"..

AND (some) plants can adapt..
Quote:
Other shade-tolerant species (e.g., iripilbark tree) show moderate (Oberbauer and Strain, 1986) or large (e.g., coffee; Friend, 1984) increases in light-saturated photosynthesis under a high light regime during development. Capacity to adjust maximum photosynthesis to utilize the light regime in which they were grown was demonstrated for 14 early-, middle-, and late-successional species grown in full sunlight and in the shade (Bazzaz and Carlson, 1982).

In a sense we sort of look at it as backwards..
Certain plants can tolerate shade.. some can't





Quote:
Shade-intolerant species tend to respond to high light regimes with much increased photosynthetic capacity. For example, the rate of light-saturated photosynthesis of seedlings of such shade intolerant species as idigbo, afara, and obeche grown at high light intensities was approximately twice as high as that of shaded seedlings. By comparison, seedlings of the shade-tolerant kuka showed little change in photosynthesis whether grown at high or low light intensities.
Quote:
Shade tolerance, defined as the ability to survive and grow under low light, plays an important role in the succession of forest plant communities. The mechanism of adaptation of plants to shading has become an important topic in ecology research. In this paper, we reviewed shade tole-rance of various forest plants and examined their adaptability in terms of morphology and physiology, and discussed the plasticity on growth traits, biomass distribution, crown structure, leaf morphology and physiology, leaf anatomical structure, photosynthetic parameters, carbohydrate allocation, water and nutrient utilization related to shade tolerance of forest plants. Finally, we discussed some problems with previous studies, and proposed possible future research issues.

Look at it another way..
https://www.ledtonic.com/blogs/guide...d-requirements


DLI for ferns ect is 4-6.


DLI for 100 "PAR" over a period of 10 hours is 3.6...
https://www.waveformlighting.com/hor...dli-calculator


300 "par" over 10 hours is a DLI of 10.8
Quote:
Shade plants (annuals and perennials) 6-10


https://pubmed.ncbi.nlm.nih.gov/29733159/
https://www.sciencedirect.com/topics...hade-tolerance




now after all my blah blah blahing..
An article on the favorable conditions for algae growth..
http://www.jlakes.org/config/hpkx/ne...04839-main.pdf


I'll let the more ambitious go through the whole thing..
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post #17 of 21 (permalink) Old 09-12-2020, 04:12 AM
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Originally Posted by Tiger15 View Post
Lengthening the photo period is not a compensation for insufficient intensity. But shortening the period is fine with sufficient intensity to control algae.
Again though let's not talk extremes..
Quote:
Very high PPFD levels over a short duration of time or very low PPFD levels over a long duration of time are rarely ideal for good growth.
Kind of a wishy washy statement..
https://www.ledtonic.com/blogs/guide...d-requirements

Obviously commercial growers need to maximize return for energy input soo they need much more specific standards than most aquarists..
And again their low light is generally our high light..

Quote:
Your grow light produces 500 PPFD at 18" from the plant according to your grow light PPFD chart/light footprint.
If the lamp's distance is increased to 20" from the plant, it produces 400 PPFD at the canopy.
If the lamp is lowered to 15", it's producing 700 PPFD. By looking at the chart we see that ~25 DLI is achieved by exposing the plant to 500 PPFD over 14 hours but also when exposing the plant to 400 PPFD over 17 hours or 700 PPFD over 10 hours.
Choose a combination that fits both your grow set up but also your plant's minimum and maximum PPFD limits.
Lengthening the photo-period can be a worthwhile thing..

50 "PAR" over 12 hours is a DLI of 2.16
Same as a 100 "PAR" over 6 hours..

100 over 12 is 4.32
Still.. "low light" in the real world.

For fun

Pretty "flexible"

now 1000"PAR" for one hour is, math wise the same as 100 "PAR" for 10 hours but since you probably max out the photo-systems it's prob only equiv to 400 effective PAR over 1 hour and a
DLI of 1.44..
Would be an interesting experiment..
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Last edited by jeffkrol; 09-12-2020 at 04:33 AM. Reason: edit
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post #18 of 21 (permalink) Old 09-12-2020, 11:19 AM
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Here is what expert says about optimum light duration:

LIGHT DURATION

Minimum of 5-6 hours for new tanks that want to minimize triggering algae.
7-10 hours is common for average, stable tanks.
10+ hours; marginal gains to plant growth rates, increased chances of algae incidence. Suggest using moonlighting/lower powered display lighting if extended lighting hours is desired for viewing purposes.


https://www.advancedplantedtank.com/...e5d6d79a&_ss=r


and explanation of light compensation and limitation ( saturation) points:

https://www.advancedplantedtank.com/...5a8d9483&_ss=r
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post #19 of 21 (permalink) Old 09-12-2020, 01:03 PM
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post #20 of 21 (permalink) Old 09-12-2020, 01:16 PM
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From the op:
Quote:
I'm running a hightech setup with a light dimmer that ramps to 100 percent intensity for about 4 hours flanked by 3 hours worth of 70 percent flanked by 7 hours at 30 percent
(Ed note 14 hours)

I'm not having an algae issues currently.
https://www.aquariumgardens.co.uk/th...algae-38-w.asp

Quote:
Algae normally appears when there is an imbalance in nutrients, CO2, oxygen and light. For example, too much light but too few nutrients and CO2 will cause algae. Poor distribution of CO2 and nutrients is also a common cause of algae. It is talked about widely that that lowering nitrates and phosphates (two vital nutrients) will reduce algae outbreaks, when actually, algae thrives in a low-nutrient environment. This is a myth and should be avoided in planted aquariums.

Here are the main reasons why we get algae in our planted aquariums:
You can't talk about duration without talking intensity, nutrients and plant maintenance as well as considering species to a certain extent.

Quote:
I'm not sure if 10 hours of low say 40 micomol vs 7 hours of higher 100micromol is better for the plants, but the energy we can calculate...
Tom Barr
https://barrreport.com/threads/minin...toperiod.5944/

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post #21 of 21 (permalink) Old 09-12-2020, 02:08 PM
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Quote:
Originally Posted by jeffkrol View Post
From the op:

You can't talk about duration without talking intensity, nutrients and plant maintenance as well as considering species to a certain extent.

Tom Barr
https://barrreport.com/threads/minin...toperiod.5944/
True. Light intensity, CO2, plant species, and nutrients all have influence on what is optimum photo period that ranges from 4.5 hour claimed in Barrreport to 12 hour advocated by Walstad.

heck my tanks got a 4 1/2 hour photo-period and i still get 1/2" a day growth on some of my plants. shorter photo period also prevents algae growth such as GSA especially with tanks that have higher light
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