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Photosynthesis explained 24/7 vs 18/6

Discussion in 'Lighting Reference' started by Captain Bowlpiece, Sep 26, 2002.

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    Captain Bowlpiece Med MJ Grower

    There is this ongoing debate about 24/7 vs 18/6 during veg of MJ. Let's get something straight. The purpose of growing during the veg period is to produce the most foliliage in the shortest time as possible. The foliliage is a product of photosynthesis. That is how the plant GROWS in other words. It doesn't grow in the dark. In the dark, it is practically dormant. That is why if it is dark for long enough, the plant starts to flower (it thinks it is dying and wants to save its gene stuff, like all living things). It is also why a mother plant can live in a vegetative state for years. 18/6 merely wastes time. It accomplishes nothing.

    To make it clearer, please refer to the diagram below. And if anybody says that in nature, there isn't 24 hours of light, I promise to smack them with a 5 gal bucket.
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    Captain Bowlpiece Med MJ Grower

    Indoors is not mimicking outdoors

    Thanks Spunjah!

    The main thing to keep in mind is that the indoor experience is not a replica of outdoors. The strains that are best suited for indoor growth have been bred and grown indoors for generations. Whether you grow in soil or hydro, under fluoros or HID, the only link between the indoor grower and the outdoor grower has to do with plant mechanics. Things like uptake of water and nutes, maturing, sexing. These are basics that exist in both worlds. For that matter, the production of sugars is basically the same in both worlds as well. It's just with the indoor world, we can control many more of the factors than the outdoor farmer. We choose when to go from a vegetative timetable to a flowering one. We decide on ALL the factors of a grow. Humidity, temperature, the works. Let's see an outdoor farmer grow his plants to full maturity in just 4 months.

    Having said that, the objective of growing indoors has to be kept in mind when deciding whether to go 24/7 or 18/6. If you are trying to create a little piece of the outdoors indoors, then by all means, have a nighttime. You might want to hook up a high velocity fan and blow your plants over once a season to replicate a wind storm, and if you live in the north, perhaps a blast from a CO2 fire extinguisher would seem like frost. Obviously, that is not the point. The goal is the best, biggest crop in the least amount of time. Taking 6 hours a day in the dark means your plants lose 42 hours of growth each week. Why waste all that time when your plant could be photosynthesizing it's green butt off. Plants don't need REST. That's what is so amazing about them. Give them the right ingredients, and they do the rest.
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    JoseHempSeed Guest


    i've been smacked with worse than 5 gal buckets :crazy: so here goes...

    i like your reasoning, and totally agree - the goal is to produce potent buds.

    but aren't there the so-called "dark reactions" where the plant produces sugars and becomes stronger and develops roots that absorb nutrients to become bigger and grow bigger buds???
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    interesting hypothesis, i understand your reasoning well.
    --------- during my last grow, i had to have the 6 hrs of dark period, during the hottest point of the day {summertime}-- the lights were tooo intense. that was the only way i could control the heat.
    - i wonder if the reduction of lumens [during the summer heat] for the xtra 42 hrs of growth, would be a fair swap?? as you already know, i have 3 lights in one hood,- a 400w hps- a 400w mh,- and a 250w hps. i could try running the 250 and the halide for veg, then kick in the other 400 for flowerring. what are your thoughts?? latr, J D.
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    Agent86 Grand Master Gardener

    I agree with The Capt'n on this one guys:

    I started my grow with the lights on 18/6.
    After reading what Ed Rosenthal had to say on the subject I changed them to 24/0. It only took a few days to realize they were growing at a much faster rate.
    I'm done experimenting. I'm sticking to 24/0 for veg from now on.

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    Knore Marijuana Research

    I think Ozgrowa sets a standard for all of us - And last time i checked he was using 18/6 im fairly sure

    There has been many threads on 24/7 VS 18/6 and 20/4 VS 24/7

    Its a never ending debate

    Personally - There needs to be an amount of darkness each cycle - In my book the plants and also the equipment need it.

    JoseHempSeed hit it right on the nail - Plants do certain chemical and biological activities/reactions during complete darkness and ONLY during complete darkness -

    You say indoor is not a replica of outdoor ? How is it not?

    Go way way way back to the start .. Where do you think all the strains that are growing indoor now started ? Yup - Outdoors !!!

    I dont want 2 get into it too much - We could go for hours about it

    All im saying is think about it logically - Plants definately do need a dark period each cycle - Even if it isnt for long - Certain things happen during Darkness that dont during light

    You may have a faster growing plant on 24/7 - But that doesnt necessarily mean its going to be a better plant
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    with no scientific evidence

    no technical backup here i grow indoors my plants get light 24-7 while in veg state it seems to me that my plants are shorter in height but much denser in terms of nodes per inch and in terms of radial shoot development

    it seems to me that the 24-7 beats the plant down so to speak
    in my non controlled experiments the plants that i have grown under 18-6 cycle were taller with an increased node spacing

    I like the result of shorter denser compact plant i end up with many budsites and thats what I want budsite not stalky stemmy growth it also fits my growspace well
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    JoseHempSeed Guest

    best thing is do a web search on photosynthesis or calvin cycle. that will explain the plant's need for darkness. darkness is necessary to complete the photosynthetic reactions.

    i used to grow 24/0, then switched to 18/6. the plants do seem a little denser under 18/6, but the biggest change was the reduction in the electric bill :D
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    HydroSan Banned

    I started here: Flowering have a look through the index for further reading;)

    went on to:Photoperiodism and Phytochrome

    got a bit lost in science and then found this:Etiolation which talks more about what happens during the dark period, or rather how a plant moves towards the light:rolleyes:

    ended up here: bgetting's view is the one to note:

    For the record, The consensus I got from reading all this and the scientificly adept posters such as Delta, bgetting etc. is that the plants do indeed need some rest. opinions varied on how much rest though:rolleyes: but I have formed the view that 20/4 for veg growing is very close to optimum:) everyone agrees 12/12 is best for flowering, the opinions vary on types of lighting though;)

    here's another delta thread explaining things proper:


    PS whilst researching this subject, I find it has been done to death on here. can't all the relevent stuff be put into a sticky to avoid the six monthly debate, this is one of two active threads on the same subject :rolleyes:
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    We are attempting to battle the nature of evolution, one I might add we cant win.

    Plants all over the world evolved to accept light and dark periods, how would you like it if you NEVER were able to sleep. While we have the luxury of eyelids so that we can "learn" to sleep with lights on, plants dont have this ability and must continue to be awake when the lights continually supply them with energy.

    Even though they are just plants, I wouldn't appreciate the constant stress of never being able to rest, it just doesn't work for me, maybe this 24/7 thing is what causes all these hermies to pop-up. Just think about why we're even growing the plant, to mellow out right? It's only fair to let the plant do the same:D .

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