What is better 18 hours or 24 hours of light..

Interesting read -

" Light Cycles

The dark cycle is very inportant to palnts. Respiration (this is when plants are making energy from sugar to oxygen) Continues in dark but at a much slower pace, almost independent of available oxygen because the leaves are not making oxygen in the dark.

In the dark there is a shift from leaf production to root production as the leaves transfer excess energy down to the branches and roots. Therefore, some dark time allows for better root structures. Giving plants a 24-hour light cycle is not the way to supercharge growth"

This is from "How to supercharge your garden"

"Light period for cuttings

Plants have a free running internal bio-rhythm of 21-27 hours. In this rhythm, they need dark time. Cuttings have a built in daily rhythm (age also) that they inherit from their parent. Cuttings will root better with a 6 hours to 8 hourdark period because this is the main time when leaves and the stems transfer energy down to the root zone for storage and growth."

The chart has hours of light per day on the bottom, and length of roots in millimeters.
-@ 4hours of light the roots after ten days were only 22mm long
-@ 8 hours of light after 10 days the roots were 25 mm long
-@12 hours of light we shoot up to 40mm long
-@16 hours it peaks at 50mm
-@20 hours it drops down to 37mm
-@ 24 hours it drops down to 29mm

There is also info regarding root to yeild ratio vs veg to yield ratio, and draws the conclusion that at the end of the experiments the root to yield ratio was higher
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That is a very interesting piece you got there Knowm! So it would be best at 16hr of light and 8hr of dark for veg? And when you say root/yield was higher than veg/yield do you mean more roots more yield?

I want to know about the root to yeild comment. More roots, more yield?

???? eeemmmmmm?

needs to be stickied

Great post knowm!

Interesting find.

Makes me want to get a new timer. lol.

Definately an awesome. Glad I did it right the 1st time around!!

littlepuppet2002 said:

Yeah, come on-root/yield, veg/yield. what the hell are we talking about here??????????

Click to expand...

"There is also info regarding root to yield ratio vs veg to yield ratio, and draws the conclusion that at the end of the experiments the root to yield ratio was higher"

This pretty much says that when finding ur perfect light cycle (which should be somewhere around 16 / 8 ) make sure u lean a lil more on having strong roots rather than really healthy vegetation. finding a completely perfect cycle is kinda impossible, and having a great root system is more important if u want high yield.

cool, i was just wondering about that.

20 hours light 4 hours dark is my personal favorite... (go figure)

cheers


YES... larger roots mean larger PLANTS..

FYI -

If you are growing hydroponicaly or aeroponically and the roots of all your plants go into the reservoir... the plant with the roots closest to any additional airstones will OUT PERFORM the other plants.. because the roots will be bigger and more robust 'cause they are getting more oxygen..(personal experience)

iloveyou

Less electricity if you don't use 24hrs a day. Sounds like a double good reason to do less hours.

Garden Knowm said:

20 hours light 4 hours dark is my personal favorite... (go figure)

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I started my first grow 21/3 just because no one could give me a decent answer. I still want more proof

I have always gone 24 hours light for veg and then 12/12 flower.Most growers I watched and learn do the same as veg time is so short 2 weeks or under

The problem may not be what it seems. When lights are on 24/7 the temperature is constantly warm, and growth may be inhibited. With constant light, and periodic cooling of the plant, then it grows more. Since it is difficult for us at home to change the temperature on a 24 hour cycle, then we need to turn the lights off to get cooling that way.
ACCELERATING MATURITY IN PICEA SEEDLINGS
USU CROP PHYSIOLOGY LABORATORY: RESEARCH: DWARF PEPPERS

Authors: Omura, Y.; Oshima, Y.; Kubota, C.; Kozai, T.
Authors affiliation: Chiba Univ., Matsudo, Chiba, 271-8510, Japan.
Published in: Hortscience, volumn 36, pages 586-587, (2001).

Abstract: "In transplant production under artificial lighting conditions, continuous lighting is desired to achieve high production efficiency while potentially reducing costs. However, such physiological disorders as chlorosis and necrosis on leaves are often observed under continuous light. Tomato (cv. Momotaro), eggplant (cv. Senryonigo), and sweet pepper (cv. Kyomidori) seedlings were grown for 14 days either under a 12-h photoperiod with a photosynthetic photon flux (PPF) of 300 mumolcntdotm-2cntdots-1 at 24/24 degreeC (temperature in photo-/dark period), or under a 24-h photoperiod (continuous light) with a PPF of 150 mumolcntdotm-2cntdots-1 under one of three temperature regimes: 24/24 degreeC, 28/20 degreeC and 32/16 degreeC (temperature in the former (12 h)/latter half (12 h) of each day). The average temperature was 24 degreeC and daily integrated PPF was 13.0 molcntdotm-2 for all treatments. The dry masses of tomato, eggplant, and sweet pepper seedlings under a 24-h photoperiod were 1.1, 1.5, and 1.6 times, respectively, greater than that under a 12-h photoperiod at 24/24 degreeC. Chlorosis was observed on leaves under a 24-h photoperiod for tomato at 24/24 degreeC and eggplant at 24/24 degreeC, and 28/20 degreeC; but, it was not observed for tomato at 28/20 degreeC and 32/16 degreeC, and eggplant at 32/16 degreeC. For all three species, the stems of the seedlings were shorter on day 14 and the seedlings set the first flower at lower nodal positions when grown under a greater diurnal range of air temperature in the 24-h photoperiod. Fluctuating the air temperature under continuous lighting enables the production of tomato, eggplant and sweet pepper transplants of quality (i.e., having accelerated growth and early flowering) without causing undesirable chlorosis on leaves."

So it is actually something else that is screwing up the growth. My own experience with cuttings shows they go brown in continuous light, but do well on 18/6 regimen.

The above post is for entertainment purposes only. I do not grown pot, but do have experience with rose cuttings.

This is an interesting read....but I'm lost as to why anyone is taking it to be fact.

For every book or article you can find that says go 18/6 you can find just as many that will say 24/0

There's SOOOO many other variables we can fuck up as humans, your vegging light cycle gets lost in the noise anyway.

and by the by....I've tried both....never saw a difference in plant growth at all that I could attend to my light cycle....again, too many other variables we humans can screw up.

I don't know where this info was found....but I'm trying to find where in your post it determines these different root lenghts were in fact a result of light and not some other variable.....every experiment has documentation to this effect and a control group...which you have mentioned none of. You just listed times and root lengths...back to all the other variables that could have had an effect on their root growth.

I'm not saying this is wrong, but there sure isn't enough to say it's right either.

BCENVY said:

This is an interesting read....but I'm lost as to why anyone is taking it to be fact.

For every book or article you can find that says go 18/6 you can find just as many that will say 24/0

There's SOOOO many other variables we can fuck up as humans, your vegging light cycle gets lost in the noise anyway.

and by the by....I've tried both....never saw a difference in plant growth at all that I could attend to my light cycle....again, too many other variables we humans can screw up.

I don't know where this info was found....but I'm trying to find where in your post it determines these different root lenghts were in fact a result of light and not some other variable.....every experiment has documentation to this effect and a control group...which you have mentioned none of. You just listed times and root lengths...back to all the other variables that could have had an effect on their root growth.

I'm not saying this is wrong, but there sure isn't enough to say it's right either.

Click to expand...

GREAT POST..

i personally think REST is good.. a few hours every day.. even 1 hour..

I also have noticed that AIRSTONES directly under/among roots sitting in a reservoir have dramatic impact on ROOT SIZE and YIELD...

iloveyou

Garden Knowm said:

GREAT POST..

i personally think REST is good.. a few hours every day.. even 1 hour..

I also have noticed that AIRSTONES directly under/among roots sitting in a reservoir have dramatic impact on ROOT SIZE and YIELD...

iloveyou

Click to expand...

I also used to think that plants need rest....but they don't, someone on here told me to read ed rosenthal's book....plants don't do anything in the dark nor do they need dark during veg. Plants don't sleep, therefor need no rest, they are the simplest form of cell reconstruction on the planet.

The high temp of the light and it's effect on the plant is more the reason that makes any of this hold water at all. The temp of a HID light on constantly can rise the internal temp of the plants leaves and stalks up over 100 degrees F....unless you are lucky enough, like I am, to have a climate controlled growing room, and this is probably why I've seen no difference no matter what light cycle I've used.

Oh and my leaves, none of my leaves have died or shown signs of chlorosis under a 24 hour cycle. My guess is that is also do to high internal leaf temps.