24 Hours Vs 18 hours veg
hey guys thought this my be of interest to some,a bit of info on 18 & 24 hour veg, as lot of people debate over which is best, im not saying either way which is 'best', as i feel what suits your needs is the 'best' option, just a lil info below as to why they dont 'need' a dark period
24 Hours Vs 18 hours veg
Most green plants are classified as either C3 or C4 which represents how carbon(C) is used during photosynthesis.
C4 plants temporarily store carbon dioxide(CO2) over the dark period to use for photosynthesis during the day. C4 plants slow down photosynthesis once the stored CO2 is used up and they need to gather it from the air. Which is why trees slow down photosynthesis in the afternoon even though the sun is still bright. This does NOT apply to cannabis.
C3 plants(cannabis/veggies) gather CO2 only during the light period when they are photosynthesizing. During the dark period these plants only use oxygen for their metabolic life processes. They don't uptake CO2, nor do they use it. As soon and as long as the light is on, C3 plants gather and use CO2 for photosynthesis.
C3 plants also have the ability to use higher concentrations of CO2 than what is found in the air. If the light is bright enough and the plants have sufficient nutes, their growth rate will accelerate from it(2000ppm vs. 400ppm of CO2), which increases yield. They can do this continuously, without a dark period throughout the vegetative stage.
The dark reaction is a process of photosynthesis that takes place in both darkness and light. It uses ATP and NADPH molecules that hold energy absorbed from light to break apart CO2 into it's base components. Because it's called a dark reaction and can occur in the dark, some people(Jorge) have said darkness is needed for this to occur. This Is Not So.
Again people get a little obsessed with their plants needs & think of them the same as humans. People need rest, so plants must too. This is false as well. Light means growth. Scientifically. Although 18/6 will 'shock' your plants less when you switch to 12/12, it's a personal choice whether you would rather sacrifice a little growth for a quicker adjustment or less photo confusion. If you want to save money or energy that's a personal choice too. Do what you need to do to make your growing situation work.
Last edited by Superjoint 420; 13-02-10 at 04:26 AM.
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section 8 (23-12-12),
THE DUDE ABIDES (12-11-12)
tho i did read some experiment they did (who-ever "they" are!) on light cycles and it showed that plants with 18 hours a day had the longest root systems while those at 24 hours a day had considerably less root Length.
nice post !!!
good read and educational!!!
interesting m8, i know usually MJ plants roots grow quite deep given the chance
Originally Posted by FZjb
I'v done light cycle experiments, all sorts of em, compared em all and personally i think the best veg cycle is 14/10 or if you plan on a long veg time 15/9, the more dark you give a plant in veg the faster it will grow, as long as the plant gets no more than 10hours of darkness it will not flower, after 3weeks veg with 14/10 your plant will be huge and be covered in preflowers if its kept healthy, this is just my opinion on light cycles, they grow/mature faster,kick into flower "A LOT" faster (1wk hairs and budsites form,2wks you got buds on your plants) and saves money on electric, but everyone's got their personal preferences eh
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interesting. quite contradictory to the original post, and never heard of anyone growing with such a light cycle..
would like to know if anyone else does this?
Originally Posted by Eddie1z
sounds about right m8 i prefer the 24/7 method did 20/4 last grow and my plants are allot biger this time round at the same time.
lmao got that round the wrong way i prefer 20/4 and plants are bigger.
http://www.thctalk.com/cannabis-foru...ad.php?t=20101 my first diary
DO NOT RUN HID GEAR 24 HOUR
It's not designed to run hot full time and need's a cool down period .
A half a hour a day for cool down is good .
Saefty first as alway's
Samhain the stoner saefty officer
Last edited by samhain; 23-02-10 at 01:10 PM.
Do you not find the internodes stretch with so many dark hours?
Originally Posted by Eddie1z
ive not done it myself m8,ai friend did try messing with his light cycles on a white widow & it began to flower with 14-ish hours of ligh but then went hermie, i just run a 18/6 cycle for veg & obvi 12/12 for flowering
Originally Posted by WaterBong
great point there, always something to remember!
Originally Posted by samhain
hours of light
what about 16 hours light? , plants drink at night, when the lights go off the foliage falls asleep and the roots go to work on the nutrients. when i first started growing i was told never to feed my plants during 'daytime' as it puts them under stress.and could turn hermi. but the canna grow guide states 18 hours while others say 20. I start at 20 hours and the knoc 2 hours off every week till their on 12/12 if they need longer just keep them at 16.
has any one tried a 24/7 cycle?
Originally Posted by Superjoint 420
What a load off bollocks and yes 24/7 good for first week when taken clones.
Originally Posted by ktrain
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24 hours of light whilst rooting my cuttings
18/6 whilst in veg, I believe plants need the dark period for a rest (tbh I've vegged under 24/0 lately and was not happy) ((timer broke heheh))
No turn left unstoned..
''The problem with pH is that very, very few people have the equipment or wet laboratory skills to measure pH correctly. In hydro, you can achieve "good enough" with common sense and basic meters. But soil pH is an entirely different ballgame. Hydrogen ions attach to soil particles and cannot be removed by simply passing water over the soil''.
I know plants do suffer from shock,but we never say...ah yes you have shock damage there mate.
I think plants that have suffered shock through transplanting or in our case changing the light period quickly recover,especially if the plant is healthy and all the other needs of the plant are met ie,proper soil, nutes, lighting etc.
It might be a good idea to closely mimic natural light cycles as much as possible ,(time permitting ) after a 24hr veg,and slowly change the lighting incrementally.
You would think 18/6 would induce flowering , i think i will try 18/6 next grow.
Does it affect the growth rate in veg ?.
I would imagine the rest period would aid the plants growth when lights turn back on.
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